Merge branch 'refactor' of https://github.com/RyanRory/loki-messenger-android into refactor

libsession/build.gradle

@@ -33,12 +33,36 @@ android {
 }
 
 dependencies {
-
+    // Local:
+    implementation project(":libsignal")
+    // Remote:
+    implementation "com.goterl.lazycode:lazysodium-android:4.2.0@aar"
     implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlinVersion"
     implementation 'androidx.core:core-ktx:1.3.2'
     implementation 'androidx.appcompat:appcompat:1.2.0'
     implementation 'com.google.android.material:material:1.2.1'
+    implementation "com.google.protobuf:protobuf-java:$protobufVersion"
     testImplementation 'junit:junit:4.+'
     androidTestImplementation 'androidx.test.ext:junit:1.1.2'
     androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
+
+    // from libsignal:
+    implementation "com.google.protobuf:protobuf-java:$protobufVersion"
+    implementation "com.googlecode.libphonenumber:libphonenumber:8.10.7"
+    implementation "com.fasterxml.jackson.core:jackson-databind:$jacksonDatabindVersion"
+
+    implementation "org.whispersystems:curve25519-java:$curve25519Version"
+    implementation "com.squareup.okhttp3:okhttp:$okhttpVersion"
+    implementation "org.threeten:threetenbp:1.3.6"
+
+    implementation "org.jetbrains.kotlin:kotlin-stdlib-jdk7:$kotlinVersion"
+    implementation "org.jetbrains.kotlin:kotlin-reflect:$kotlinVersion"
+
+    implementation "org.jetbrains.kotlinx:kotlinx-coroutines-android:1.3.9"
+    implementation "nl.komponents.kovenant:kovenant:$kovenantVersion"
+
+    testImplementation "junit:junit:3.8.2"
+    testImplementation "org.assertj:assertj-core:1.7.1"
+    testImplementation "org.conscrypt:conscrypt-openjdk-uber:2.0.0"
+
 }

libsession/src/main/java/org/session/libsession/messaging/Configuration.kt

@@ -0,0 +1,22 @@
+package org.session.libsession.messaging
+
+import org.session.libsignal.libsignal.loki.SessionResetProtocol
+import org.session.libsignal.libsignal.state.*
+import org.session.libsignal.metadata.certificate.CertificateValidator
+import org.session.libsignal.service.loki.protocol.closedgroups.SharedSenderKeysDatabaseProtocol
+
+class Configuration(val storage: StorageProtocol, val signalStorage: SignalProtocolStore, val sskDatabase: SharedSenderKeysDatabaseProtocol, val sessionResetImp: SessionResetProtocol, val certificateValidator: CertificateValidator) {
+    companion object {
+        lateinit var shared: Configuration
+
+        fun configure(storage: StorageProtocol,
+                      signalStorage: SignalProtocolStore,
+                      sskDatabase: SharedSenderKeysDatabaseProtocol,
+                      sessionResetImp: SessionResetProtocol,
+                      certificateValidator: CertificateValidator
+        ) {
+            if (Companion::shared.isInitialized) { return }
+            shared = Configuration(storage, signalStorage, sskDatabase, sessionResetImp, certificateValidator)
+        }
+    }
+}

libsession/src/main/java/org/session/libsession/messaging/StorageProtocol.kt

@@ -0,0 +1,75 @@
+package org.session.libsession.messaging
+
+import org.session.libsession.messaging.jobs.AttachmentUploadJob
+import org.session.libsession.messaging.jobs.Job
+import org.session.libsession.messaging.jobs.MessageSendJob
+import org.session.libsession.messaging.opengroups.OpenGroup
+
+import org.session.libsignal.libsignal.ecc.ECKeyPair
+import org.session.libsignal.libsignal.ecc.ECPrivateKey
+
+interface StorageProtocol {
+
+    // General
+    fun getUserPublicKey(): String?
+    fun getUserKeyPair(): ECKeyPair?
+    fun getUserDisplayName(): String?
+    fun getUserProfileKey(): ByteArray?
+    fun getUserProfilePictureURL(): String?
+
+    // Signal Protocol
+
+    fun getOrGenerateRegistrationID(): Int //TODO needs impl
+
+    // Shared Sender Keys
+    fun getClosedGroupPrivateKey(publicKey: String): ECPrivateKey?
+    fun isClosedGroup(publicKey: String): Boolean
+
+    // Jobs
+    fun persist(job: Job)
+    fun markJobAsSucceeded(job: Job)
+    fun markJobAsFailed(job: Job)
+    fun getAllPendingJobs(type: String): List<Job>
+    fun getAttachmentUploadJob(attachmentID: String): AttachmentUploadJob?
+    fun getMessageSendJob(messageSendJobID: String): MessageSendJob?
+    fun resumeMessageSendJobIfNeeded(messageSendJobID: String)
+    fun isJobCanceled(job: Job): Boolean
+
+    // Authorization
+    fun getAuthToken(server: String): String?
+    fun setAuthToken(server: String, newValue: String?)
+    fun removeAuthToken(server: String)
+
+    // Open Groups
+    fun getOpenGroup(threadID: String): OpenGroup?
+    fun getThreadID(openGroupID: String): String?
+
+    // Open Group Public Keys
+    fun getOpenGroupPublicKey(server: String): String?
+    fun setOpenGroupPublicKey(server: String, newValue: String)
+
+    // Last Message Server ID
+    fun getLastMessageServerID(group: Long, server: String): Long?
+    fun setLastMessageServerID(group: Long, server: String, newValue: Long)
+    fun removeLastMessageServerID(group: Long, server: String)
+
+    // Last Deletion Server ID
+    fun getLastDeletionServerID(group: Long, server: String): Long?
+    fun setLastDeletionServerID(group: Long, server: String, newValue: Long)
+    fun removeLastDeletionServerID(group: Long, server: String)
+
+    // Open Group Metadata
+    fun setUserCount(group: Long, server: String, newValue: Int)
+    fun setOpenGroupProfilePictureURL(group: Long, server: String, newValue: String)
+    fun getOpenGroupProfilePictureURL(group: Long, server: String): String?
+    fun updateTitle(groupID: String, newValue: String)
+    fun updateProfilePicture(groupID: String, newValue: ByteArray)
+
+
+
+
+    fun getSessionRequestSentTimestamp(publicKey: String): Long?
+    fun setSessionRequestSentTimestamp(publicKey: String, newValue: Long)
+    fun getSessionRequestProcessedTimestamp(publicKey: String): Long?
+    fun setSessionRequestProcessedTimestamp(publicKey: String, newValue: Long)
+}

libsession/src/main/java/org/session/libsession/messaging/fileserver/FileServerAPI.kt

@@ -0,0 +1,262 @@
+package org.session.libsession.messaging.fileserver
+
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.functional.bind
+import nl.komponents.kovenant.functional.map
+import okhttp3.Request
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.libsignal.util.Hex
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsignal.service.loki.api.SnodeAPI
+import org.session.libsignal.service.loki.api.LokiDotNetAPI
+import org.session.libsignal.service.loki.api.onionrequests.OnionRequestAPI
+import org.session.libsignal.service.loki.database.LokiAPIDatabaseProtocol
+import org.session.libsignal.service.loki.protocol.shelved.multidevice.DeviceLink
+import org.session.libsignal.service.loki.utilities.*
+import java.net.URL
+import java.util.concurrent.ConcurrentHashMap
+import kotlin.collections.set
+
+class FileServerAPI(public val server: String, userPublicKey: String, userPrivateKey: ByteArray, private val database: LokiAPIDatabaseProtocol) : LokiDotNetAPI(userPublicKey, userPrivateKey, database) {
+
+    companion object {
+        // region Settings
+        /**
+         * Deprecated.
+         */
+        private val deviceLinkType = "network.loki.messenger.devicemapping"
+        /**
+         * Deprecated.
+         */
+        private val deviceLinkRequestCache = ConcurrentHashMap<String, Promise<Set<DeviceLink>, Exception>>()
+        /**
+         * Deprecated.
+         */
+        private val deviceLinkUpdateInterval = 60 * 1000
+        private val lastDeviceLinkUpdate = ConcurrentHashMap<String, Long>()
+
+        internal val fileServerPublicKey = "62509D59BDEEC404DD0D489C1E15BA8F94FD3D619B01C1BF48A9922BFCB7311C"
+        internal val maxRetryCount = 4
+
+        public val maxFileSize = 10_000_000 // 10 MB
+        /**
+         * The file server has a file size limit of `maxFileSize`, which the Service Nodes try to enforce as well. However, the limit applied by the Service Nodes
+         * is on the **HTTP request** and not the actual file size. Because the file server expects the file data to be base 64 encoded, the size of the HTTP
+         * request for a given file will be at least `ceil(n / 3) * 4` bytes, where n is the file size in bytes. This is the minimum size because there might also
+         * be other parameters in the request. On average the multiplier appears to be about 1.5, so when checking whether the file will exceed the file size limit when
+         * uploading a file we just divide the size of the file by this number. The alternative would be to actually check the size of the HTTP request but that's only
+         * possible after proof of work has been calculated and the onion request encryption has happened, which takes several seconds.
+         */
+        public val fileSizeORMultiplier = 2 // TODO: It should be possible to set this to 1.5?
+        public val fileStorageBucketURL = "https://file-static.lokinet.org"
+        // endregion
+
+        // region Initialization
+        lateinit var shared: FileServerAPI
+
+        /**
+         * Must be called before `LokiAPI` is used.
+         */
+        fun configure(userPublicKey: String, userPrivateKey: ByteArray, database: LokiAPIDatabaseProtocol) {
+            if (Companion::shared.isInitialized) { return }
+            val server = "https://file.getsession.org"
+            shared = FileServerAPI(server, userPublicKey, userPrivateKey, database)
+        }
+        // endregion
+    }
+
+    // region Device Link Update Result
+    sealed class DeviceLinkUpdateResult {
+        class Success(val publicKey: String, val deviceLinks: Set<DeviceLink>) : DeviceLinkUpdateResult()
+        class Failure(val publicKey: String, val error: Exception) : DeviceLinkUpdateResult()
+    }
+    // endregion
+
+    // region API
+    public fun hasDeviceLinkCacheExpired(referenceTime: Long = System.currentTimeMillis(), publicKey: String): Boolean {
+        return !lastDeviceLinkUpdate.containsKey(publicKey) || (referenceTime - lastDeviceLinkUpdate[publicKey]!! > deviceLinkUpdateInterval)
+    }
+
+    fun getDeviceLinks(publicKey: String, isForcedUpdate: Boolean = false): Promise<Set<DeviceLink>, Exception> {
+        return Promise.of(setOf())
+        /*
+        if (deviceLinkRequestCache.containsKey(publicKey) && !isForcedUpdate) {
+            val result = deviceLinkRequestCache[publicKey]
+            if (result != null) { return result } // A request was already pending
+        }
+        val promise = getDeviceLinks(setOf(publicKey), isForcedUpdate)
+        deviceLinkRequestCache[publicKey] = promise
+        promise.always {
+            deviceLinkRequestCache.remove(publicKey)
+        }
+        return promise
+         */
+    }
+
+    fun getDeviceLinks(publicKeys: Set<String>, isForcedUpdate: Boolean = false): Promise<Set<DeviceLink>, Exception> {
+        return Promise.of(setOf())
+        /*
+        val validPublicKeys = publicKeys.filter { PublicKeyValidation.isValid(it) }
+        val now = System.currentTimeMillis()
+        // IMPORTANT: Don't fetch device links for the current user (i.e. don't remove the it != userHexEncodedPublicKey) check below
+        val updatees = validPublicKeys.filter { it != userPublicKey && (hasDeviceLinkCacheExpired(now, it) || isForcedUpdate) }.toSet()
+        val cachedDeviceLinks = validPublicKeys.minus(updatees).flatMap { database.getDeviceLinks(it) }.toSet()
+        if (updatees.isEmpty()) {
+            return Promise.of(cachedDeviceLinks)
+        } else {
+            return getUserProfiles(updatees, server, true).map(SnodeAPI.sharedContext) { data ->
+                data.map dataMap@ { node ->
+                    val publicKey = node["username"] as String
+                    val annotations = node["annotations"] as List<Map<*, *>>
+                    val deviceLinksAnnotation = annotations.find {
+                        annotation -> (annotation["type"] as String) == deviceLinkType
+                    } ?: return@dataMap DeviceLinkUpdateResult.Success(publicKey, setOf())
+                    val value = deviceLinksAnnotation["value"] as Map<*, *>
+                    val deviceLinksAsJSON = value["authorisations"] as List<Map<*, *>>
+                    val deviceLinks = deviceLinksAsJSON.mapNotNull { deviceLinkAsJSON ->
+                        try {
+                            val masterPublicKey = deviceLinkAsJSON["primaryDevicePubKey"] as String
+                            val slavePublicKey = deviceLinkAsJSON["secondaryDevicePubKey"] as String
+                            var requestSignature: ByteArray? = null
+                            var authorizationSignature: ByteArray? = null
+                            if (deviceLinkAsJSON["requestSignature"] != null) {
+                                val base64EncodedSignature = deviceLinkAsJSON["requestSignature"] as String
+                                requestSignature = Base64.decode(base64EncodedSignature)
+                            }
+                            if (deviceLinkAsJSON["grantSignature"] != null) {
+                                val base64EncodedSignature = deviceLinkAsJSON["grantSignature"] as String
+                                authorizationSignature = Base64.decode(base64EncodedSignature)
+                            }
+                            val deviceLink = DeviceLink(masterPublicKey, slavePublicKey, requestSignature, authorizationSignature)
+                            val isValid = deviceLink.verify()
+                            if (!isValid) {
+                                Log.d("Loki", "Ignoring invalid device link: $deviceLinkAsJSON.")
+                                return@mapNotNull null
+                            }
+                            deviceLink
+                        } catch (e: Exception) {
+                            Log.d("Loki", "Failed to parse device links for $publicKey from $deviceLinkAsJSON due to error: $e.")
+                            null
+                        }
+                    }.toSet()
+                    DeviceLinkUpdateResult.Success(publicKey, deviceLinks)
+                }
+            }.recover { e ->
+                publicKeys.map { DeviceLinkUpdateResult.Failure(it, e) }
+            }.success { updateResults ->
+                for (updateResult in updateResults) {
+                    if (updateResult is DeviceLinkUpdateResult.Success) {
+                        database.clearDeviceLinks(updateResult.publicKey)
+                        updateResult.deviceLinks.forEach { database.addDeviceLink(it) }
+                    } else {
+                        // Do nothing
+                    }
+                }
+            }.map(SnodeAPI.sharedContext) { updateResults ->
+                val deviceLinks = mutableListOf<DeviceLink>()
+                for (updateResult in updateResults) {
+                    when (updateResult) {
+                        is DeviceLinkUpdateResult.Success -> {
+                            lastDeviceLinkUpdate[updateResult.publicKey] = now
+                            deviceLinks.addAll(updateResult.deviceLinks)
+                        }
+                        is DeviceLinkUpdateResult.Failure -> {
+                            if (updateResult.error is SnodeAPI.Error.ParsingFailed) {
+                                lastDeviceLinkUpdate[updateResult.publicKey] = now // Don't infinitely update in case of a parsing failure
+                            }
+                            deviceLinks.addAll(database.getDeviceLinks(updateResult.publicKey)) // Fall back on cached device links in case of a failure
+                        }
+                    }
+                }
+                // Updatees that didn't show up in the response provided by the file server are assumed to not have any device links
+                val excludedUpdatees = updatees.filter { updatee ->
+                    updateResults.find { updateResult ->
+                        when (updateResult) {
+                            is DeviceLinkUpdateResult.Success -> updateResult.publicKey == updatee
+                            is DeviceLinkUpdateResult.Failure -> updateResult.publicKey == updatee
+                        }
+                    } == null
+                }
+                excludedUpdatees.forEach {
+                    lastDeviceLinkUpdate[it] = now
+                }
+                deviceLinks.union(cachedDeviceLinks)
+            }.recover {
+                publicKeys.flatMap { database.getDeviceLinks(it) }.toSet()
+            }
+        }
+         */
+    }
+
+    fun setDeviceLinks(deviceLinks: Set<DeviceLink>): Promise<Unit, Exception> {
+        return Promise.of(Unit)
+        /*
+        val isMaster = deviceLinks.find { it.masterPublicKey == userPublicKey } != null
+        val deviceLinksAsJSON = deviceLinks.map { it.toJSON() }
+        val value = if (deviceLinks.isNotEmpty()) mapOf( "isPrimary" to isMaster, "authorisations" to deviceLinksAsJSON ) else null
+        val annotation = mapOf( "type" to deviceLinkType, "value" to value )
+        val parameters = mapOf( "annotations" to listOf( annotation ) )
+        return retryIfNeeded(maxRetryCount) {
+            execute(HTTPVerb.PATCH, server, "/users/me", parameters = parameters)
+        }.map { Unit }
+         */
+    }
+
+    fun addDeviceLink(deviceLink: DeviceLink): Promise<Unit, Exception> {
+        return Promise.of(Unit)
+        /*
+        Log.d("Loki", "Updating device links.")
+        return getDeviceLinks(userPublicKey, true).bind { deviceLinks ->
+            val mutableDeviceLinks = deviceLinks.toMutableSet()
+            mutableDeviceLinks.add(deviceLink)
+            setDeviceLinks(mutableDeviceLinks)
+        }.success {
+            database.addDeviceLink(deviceLink)
+        }.map { Unit }
+         */
+    }
+
+    fun removeDeviceLink(deviceLink: DeviceLink): Promise<Unit, Exception> {
+        return Promise.of(Unit)
+        /*
+        Log.d("Loki", "Updating device links.")
+        return getDeviceLinks(userPublicKey, true).bind { deviceLinks ->
+            val mutableDeviceLinks = deviceLinks.toMutableSet()
+            mutableDeviceLinks.remove(deviceLink)
+            setDeviceLinks(mutableDeviceLinks)
+        }.success {
+            database.removeDeviceLink(deviceLink)
+        }.map { Unit }
+         */
+    }
+    // endregion
+
+    // region Open Group Server Public Key
+    fun getPublicKeyForOpenGroupServer(openGroupServer: String): Promise<String, Exception> {
+        val publicKey = database.getOpenGroupPublicKey(openGroupServer)
+        if (publicKey != null && PublicKeyValidation.isValid(publicKey, 64, false)) {
+            return Promise.of(publicKey)
+        } else {
+            val url = "$server/loki/v1/getOpenGroupKey/${URL(openGroupServer).host}"
+            val request = Request.Builder().url(url)
+            request.addHeader("Content-Type", "application/json")
+            request.addHeader("Authorization", "Bearer loki") // Tokenless request; use a dummy token
+            return OnionRequestAPI.sendOnionRequest(request.build(), server, fileServerPublicKey).map { json ->
+                try {
+                    val bodyAsString = json["data"] as String
+                    val body = JsonUtil.fromJson(bodyAsString)
+                    val base64EncodedPublicKey = body.get("data").asText()
+                    val prefixedPublicKey = Base64.decode(base64EncodedPublicKey)
+                    val hexEncodedPrefixedPublicKey = prefixedPublicKey.toHexString()
+                    val result = hexEncodedPrefixedPublicKey.removing05PrefixIfNeeded()
+                    database.setOpenGroupPublicKey(openGroupServer, result)
+                    result
+                } catch (exception: Exception) {
+                    Log.d("Loki", "Couldn't parse open group public key from: $json.")
+                    throw exception
+                }
+            }
+        }
+    }
+}

libsession/src/main/java/org/session/libsession/messaging/jobs/AttachmentDownloadJob.kt

@@ -1,4 +1,17 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
 class AttachmentDownloadJob: Job {
+    override var delegate: JobDelegate? = null
+    override var id: String? = null
+    override var failureCount: Int = 0
+
+    // Settings
+    override val maxFailureCount: Int = 100
+    companion object {
+        val collection: String = "AttachmentDownloadJobCollection"
+    }
+
+    override fun execute() {
+        TODO("Not yet implemented")
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/AttachmentUploadJob.kt

@@ -1,4 +1,17 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
 class AttachmentUploadJob : Job {
+    override var delegate: JobDelegate? = null
+    override var id: String? = null
+    override var failureCount: Int = 0
+
+    // Settings
+    override val maxFailureCount: Int = 20
+    companion object {
+        val collection: String = "AttachmentUploadJobCollection"
+    }
+
+    override fun execute() {
+        TODO("Not yet implemented")
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/Job.kt

@@ -1,4 +1,11 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
 interface Job {
+    var delegate: JobDelegate?
+    var id: String?
+    var failureCount: Int
+
+    val maxFailureCount: Int
+
+    fun execute()
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/JobDelegate.kt

@@ -1,4 +1,7 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
 interface JobDelegate {
+    fun handleJobSucceeded(job: Job)
+    fun handleJobFailed(job: Job, error: Exception)
+    fun handleJobFailedPermanently(job: Job, error: Exception)
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/JobQueue.kt

@@ -1,4 +1,89 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
+
+import kotlin.math.min
+import kotlin.math.pow
+import java.util.Timer
+
+import org.session.libsession.messaging.Configuration
+
+import org.session.libsignal.libsignal.logging.Log
+import kotlin.concurrent.schedule
+import kotlin.math.roundToLong
+
 
 class JobQueue : JobDelegate {
+    private var hasResumedPendingJobs = false // Just for debugging
+
+    companion object {
+        val shared: JobQueue by lazy { JobQueue() }
+    }
+
+    fun add(job: Job) {
+        addWithoutExecuting(job)
+        job.execute()
+    }
+
+    fun addWithoutExecuting(job: Job) {
+        job.id = System.currentTimeMillis().toString()
+        Configuration.shared.storage.persist(job)
+        job.delegate = this
+    }
+
+    fun resumePendingJobs() {
+        if (hasResumedPendingJobs) {
+            Log.d("Loki", "resumePendingJobs() should only be called once.")
+            return
+        }
+        hasResumedPendingJobs = true
+        val allJobTypes = listOf(AttachmentDownloadJob.collection, AttachmentDownloadJob.collection, MessageReceiveJob.collection, MessageSendJob.collection, NotifyPNServerJob.collection)
+        allJobTypes.forEach { type ->
+            val allPendingJobs = Configuration.shared.storage.getAllPendingJobs(type)
+            allPendingJobs.sortedBy { it.id }.forEach { job ->
+                Log.i("Jobs", "Resuming pending job of type: ${job::class.simpleName}.")
+                job.delegate = this
+                job.execute()
+            }
+        }
+    }
+
+    override fun handleJobSucceeded(job: Job) {
+        Configuration.shared.storage.markJobAsSucceeded(job)
+    }
+
+    override fun handleJobFailed(job: Job, error: Exception) {
+        job.failureCount += 1
+        val storage = Configuration.shared.storage
+        if (storage.isJobCanceled(job)) { return Log.i("Jobs", "${job::class.simpleName} canceled.")}
+        storage.persist(job)
+        if (job.failureCount == job.maxFailureCount) {
+            storage.markJobAsFailed(job)
+        } else {
+            val retryInterval = getRetryInterval(job)
+            Log.i("Jobs", "${job::class.simpleName} failed; scheduling retry (failure count is ${job.failureCount}).")
+            Timer().schedule(delay = retryInterval) {
+                Log.i("Jobs", "Retrying ${job::class.simpleName}.")
+                job.execute()
+            }
+        }
+    }
+
+    override fun handleJobFailedPermanently(job: Job, error: Exception) {
+        job.failureCount += 1
+        val storage = Configuration.shared.storage
+        storage.persist(job)
+        storage.markJobAsFailed(job)
+    }
+
+    private fun getRetryInterval(job: Job): Long {
+        // Arbitrary backoff factor...
+        // try  1 delay:  0ms
+        // try  2 delay:  190ms
+        // ...
+        // try  5 delay:  1300ms
+        // ...
+        // try 11 delay: 61310ms
+        val backoffFactor = 1.9
+        val maxBackoff = (60 * 60 * 1000).toDouble()
+        return (100 * min(maxBackoff, backoffFactor.pow(job.failureCount))).roundToLong()
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/MessageReceiveJob.kt

@@ -1,4 +1,17 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
 class MessageReceiveJob : Job {
+    override var delegate: JobDelegate? = null
+    override var id: String? = null
+    override var failureCount: Int = 0
+
+    // Settings
+    override val maxFailureCount: Int = 10
+    companion object {
+        val collection: String = "MessageReceiveJobCollection"
+    }
+
+    override fun execute() {
+        TODO("Not yet implemented")
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/MessageSendJob.kt

@@ -1,4 +1,17 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
 class MessageSendJob : Job {
+    override var delegate: JobDelegate? = null
+    override var id: String? = null
+    override var failureCount: Int = 0
+
+    // Settings
+    override val maxFailureCount: Int = 10
+    companion object {
+        val collection: String = "MessageSendJobCollection"
+    }
+
+    override fun execute() {
+        TODO("Not yet implemented")
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/jobs/NotifyPNServerJob.kt

@@ -1,4 +1,57 @@
-package org.session.messaging.jobs
+package org.session.libsession.messaging.jobs
 
-class NotifyPNServerJob : Job {
+import nl.komponents.kovenant.functional.map
+import okhttp3.MediaType
+import okhttp3.Request
+import okhttp3.RequestBody
+
+import org.session.libsession.messaging.sending_receiving.notifications.PushNotificationAPI
+import org.session.libsession.snode.SnodeMessage
+import org.session.libsession.snode.OnionRequestAPI
+
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsignal.service.loki.utilities.retryIfNeeded
+
+class NotifyPNServerJob(val message: SnodeMessage) : Job {
+    override var delegate: JobDelegate? = null
+    override var id: String? = null
+    override var failureCount: Int = 0
+
+    // Settings
+    override val maxFailureCount: Int = 20
+    companion object {
+        val collection: String = "NotifyPNServerJobCollection"
+    }
+
+    // Running
+    override fun execute() {
+        val server = PushNotificationAPI.server
+        val parameters = mapOf( "data" to message.data, "send_to" to message.recipient )
+        val url = "${server}/notify"
+        val body = RequestBody.create(MediaType.get("application/json"), JsonUtil.toJson(parameters))
+        val request = Request.Builder().url(url).post(body)
+        retryIfNeeded(4) {
+            OnionRequestAPI.sendOnionRequest(request.build(), server, PushNotificationAPI.serverPublicKey, "/loki/v2/lsrpc").map { json ->
+                val code = json["code"] as? Int
+                if (code == null || code == 0) {
+                    Log.d("Loki", "[Loki] Couldn't notify PN server due to error: ${json["message"] as? String ?: "null"}.")
+                }
+            }.fail { exception ->
+                Log.d("Loki", "[Loki] Couldn't notify PN server due to error: $exception.")
+            }
+        }.success {
+            handleSuccess()
+        }. fail {
+            handleFailure(it)
+        }
+    }
+
+    private fun handleSuccess() {
+        delegate?.handleJobSucceeded(this)
+    }
+
+    private fun handleFailure(error: Exception) {
+        delegate?.handleJobFailed(this, error)
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/Destination.kt

@@ -1,5 +1,12 @@
-package org.session.messaging.messages
+package org.session.libsession.messaging.messages
 
-enum class Destination {
+sealed class Destination {
 
+    class Contact(val publicKey: String) : Destination()
+    class ClosedGroup(val groupPublicKey: String) : Destination()
+    class OpenGroup(val channel: Long, val server: String) : Destination()
+
+    companion object {
+        //TODO need to implement the equivalent to TSThread and then implement from(...)
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/Message.kt

@@ -1,5 +1,26 @@
-package org.session.messaging.messages
+package org.session.libsession.messaging.messages
 
-open class Message {
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+abstract class Message {
+
+    var id: String? = null
+    var threadID: String? = null
+    var sentTimestamp: Long? = null
+    var receivedTimestamp: Long? = null
+    var recipient: String? = null
+    var sender: String? = null
+    var groupPublicKey: String? = null
+    var openGroupServerMessageID: Long? = null
+    val ttl: Long = 2 * 24 * 60 * 60 * 1000
+
+    // validation
+    open fun isValid(): Boolean {
+        sentTimestamp = if (sentTimestamp!! > 0) sentTimestamp else return false
+        receivedTimestamp = if (receivedTimestamp!! > 0) receivedTimestamp else return false
+        return sender != null && recipient != null
+    }
+
+    abstract fun toProto(): SignalServiceProtos.Content?
 
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/ClosedGroupUpdate.kt

@@ -1,4 +1,154 @@
-package org.session.messaging.messages.control
+package org.session.libsession.messaging.messages.control
 
-class ClosedGroupUpdate : ControlMessage() {
+import com.google.protobuf.ByteString
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import org.session.libsignal.service.loki.protocol.closedgroups.ClosedGroupSenderKey
+
+class ClosedGroupUpdate() : ControlMessage() {
+
+    var kind: Kind? = null
+
+    // Kind enum
+    sealed class Kind {
+        class New(val groupPublicKey: ByteArray, val name: String, val groupPrivateKey: ByteArray, val senderKeys: Collection<org.session.libsignal.service.loki.protocol.closedgroups.ClosedGroupSenderKey>, val members: Collection<ByteArray>, val admins: Collection<ByteArray>) : Kind()
+        class Info(val groupPublicKey: ByteArray, val name: String, val senderKeys: Collection<org.session.libsignal.service.loki.protocol.closedgroups.ClosedGroupSenderKey>, val members: Collection<ByteArray>, val admins: Collection<ByteArray>) : Kind()
+        class SenderKeyRequest(val groupPublicKey: ByteArray) : Kind()
+        class SenderKey(val groupPublicKey: ByteArray, val senderKey: org.session.libsignal.service.loki.protocol.closedgroups.ClosedGroupSenderKey) : Kind()
+    }
+
+    companion object {
+        const val TAG = "ClosedGroupUpdate"
+
+        fun fromProto(proto: SignalServiceProtos.Content): ClosedGroupUpdate? {
+            val closedGroupUpdateProto = proto.dataMessage?.closedGroupUpdate ?: return null
+            val groupPublicKey = closedGroupUpdateProto.groupPublicKey
+            var kind: Kind
+            when(closedGroupUpdateProto.type) {
+                SignalServiceProtos.ClosedGroupUpdate.Type.NEW -> {
+                    val name = closedGroupUpdateProto.name ?: return null
+                    val groupPrivateKey = closedGroupUpdateProto.groupPrivateKey ?: return null
+                    val senderKeys = closedGroupUpdateProto.senderKeysList.map { ClosedGroupSenderKey.fromProto(it) }
+                    kind = Kind.New(
+                            groupPublicKey = groupPublicKey.toByteArray(),
+                            name = name,
+                            groupPrivateKey = groupPrivateKey.toByteArray(),
+                            senderKeys = senderKeys,
+                            members = closedGroupUpdateProto.membersList.map { it.toByteArray() },
+                            admins = closedGroupUpdateProto.adminsList.map { it.toByteArray() }
+                    )
+                }
+                SignalServiceProtos.ClosedGroupUpdate.Type.INFO -> {
+                    val name = closedGroupUpdateProto.name ?: return null
+                    val senderKeys = closedGroupUpdateProto.senderKeysList.map { ClosedGroupSenderKey.fromProto(it) }
+                    kind = Kind.Info(
+                            groupPublicKey = groupPublicKey.toByteArray(),
+                            name = name,
+                            senderKeys = senderKeys,
+                            members = closedGroupUpdateProto.membersList.map { it.toByteArray() },
+                            admins = closedGroupUpdateProto.adminsList.map { it.toByteArray() }
+                    )
+                }
+                SignalServiceProtos.ClosedGroupUpdate.Type.SENDER_KEY_REQUEST -> {
+                    kind = Kind.SenderKeyRequest(groupPublicKey = groupPublicKey.toByteArray())
+                }
+                SignalServiceProtos.ClosedGroupUpdate.Type.SENDER_KEY -> {
+                    val senderKeyProto = closedGroupUpdateProto.senderKeysList?.first() ?: return null
+                    kind = Kind.SenderKey(
+                            groupPublicKey = groupPublicKey.toByteArray(),
+                            senderKey = ClosedGroupSenderKey.fromProto(senderKeyProto)
+                    )
+                }
+            }
+            return ClosedGroupUpdate(kind)
+        }
+    }
+
+    // constructor
+    internal constructor(kind: Kind?) : this() {
+        this.kind = kind
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        val kind = kind ?: return false
+        when(kind) {
+            is Kind.New -> {
+                return !kind.groupPublicKey.isEmpty() && !kind.name.isEmpty() && !kind.groupPrivateKey.isEmpty() && !kind.members.isEmpty() && !kind.admins.isEmpty()
+            }
+            is Kind.Info -> {
+                return !kind.groupPublicKey.isEmpty() && !kind.name.isEmpty() && !kind.members.isEmpty() && !kind.admins.isEmpty()
+            }
+            is Kind.SenderKeyRequest -> {
+                return !kind.groupPublicKey.isEmpty()
+            }
+            is Kind.SenderKey -> {
+                return !kind.groupPublicKey.isEmpty()
+            }
+        }
+    }
+
+    override fun toProto(): SignalServiceProtos.Content? {
+        val kind = kind
+        if (kind == null) {
+            Log.w(TAG, "Couldn't construct closed group update proto from: $this")
+            return null
+        }
+        try {
+            val closedGroupUpdate: SignalServiceProtos.ClosedGroupUpdate.Builder = SignalServiceProtos.ClosedGroupUpdate.newBuilder()
+            when (kind) {
+                is Kind.New -> {
+                    closedGroupUpdate.groupPublicKey = ByteString.copyFrom(kind.groupPublicKey)
+                    closedGroupUpdate.type = SignalServiceProtos.ClosedGroupUpdate.Type.NEW
+                    closedGroupUpdate.name = kind.name
+                    closedGroupUpdate.groupPrivateKey = ByteString.copyFrom(kind.groupPrivateKey)
+                    closedGroupUpdate.addAllSenderKeys(kind.senderKeys.map { it.toProto() })
+                    closedGroupUpdate.addAllMembers(kind.members.map { ByteString.copyFrom(it) })
+                    closedGroupUpdate.addAllAdmins(kind.admins.map { ByteString.copyFrom(it) })
+                }
+                is Kind.Info -> {
+                    closedGroupUpdate.groupPublicKey = ByteString.copyFrom(kind.groupPublicKey)
+                    closedGroupUpdate.type = SignalServiceProtos.ClosedGroupUpdate.Type.INFO
+                    closedGroupUpdate.name = kind.name
+                    closedGroupUpdate.addAllSenderKeys(kind.senderKeys.map { it.toProto() })
+                    closedGroupUpdate.addAllMembers(kind.members.map { ByteString.copyFrom(it) })
+                    closedGroupUpdate.addAllAdmins(kind.admins.map { ByteString.copyFrom(it) })
+                }
+                is Kind.SenderKeyRequest -> {
+                    closedGroupUpdate.groupPublicKey = ByteString.copyFrom(kind.groupPublicKey)
+                    closedGroupUpdate.type = SignalServiceProtos.ClosedGroupUpdate.Type.SENDER_KEY_REQUEST
+                }
+                is Kind.SenderKey -> {
+                    closedGroupUpdate.groupPublicKey = ByteString.copyFrom(kind.groupPublicKey)
+                    closedGroupUpdate.type = SignalServiceProtos.ClosedGroupUpdate.Type.SENDER_KEY
+                    closedGroupUpdate.addAllSenderKeys(listOf( kind.senderKey.toProto() ))
+                }
+            }
+            val contentProto = SignalServiceProtos.Content.newBuilder()
+            val dataMessageProto = SignalServiceProtos.DataMessage.newBuilder()
+            dataMessageProto.closedGroupUpdate = closedGroupUpdate.build()
+            contentProto.dataMessage = dataMessageProto.build()
+            return contentProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct closed group update proto from: $this")
+            return null
+        }
+        return null
+    }
+
+}
+
+// extension functions to class ClosedGroupSenderKey
+
+private fun ClosedGroupSenderKey.Companion.fromProto(proto: SignalServiceProtos.ClosedGroupUpdate.SenderKey): ClosedGroupSenderKey {
+    return ClosedGroupSenderKey(chainKey = proto.chainKey.toByteArray(), keyIndex = proto.keyIndex, publicKey = proto.publicKey.toByteArray())
+}
+
+private fun ClosedGroupSenderKey.toProto(): SignalServiceProtos.ClosedGroupUpdate.SenderKey {
+    val proto = SignalServiceProtos.ClosedGroupUpdate.SenderKey.newBuilder()
+    proto.chainKey = ByteString.copyFrom(chainKey)
+    proto.keyIndex = keyIndex
+    proto.publicKey = ByteString.copyFrom(publicKey)
+    return proto.build()
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/ControlMessage.kt

@@ -1,6 +1,6 @@
-package org.session.messaging.messages.control
+package org.session.libsession.messaging.messages.control
 
-import org.session.messaging.messages.Message
+import org.session.libsession.messaging.messages.Message
 
-open class ControlMessage : Message() {
+abstract class ControlMessage : Message() {
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/ExpirationTimerUpdate.kt

@@ -1,4 +1,51 @@
-package org.session.messaging.messages.control
+package org.session.libsession.messaging.messages.control
 
-class ExpirationTimerUpdate : ControlMessage() {
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class ExpirationTimerUpdate() : ControlMessage() {
+
+    var duration: Int? = 0
+
+    companion object {
+        const val TAG = "ExpirationTimerUpdate"
+
+        fun fromProto(proto: SignalServiceProtos.Content): ExpirationTimerUpdate? {
+            val dataMessageProto = proto.dataMessage ?: return null
+            val isExpirationTimerUpdate = (dataMessageProto.flags and SignalServiceProtos.DataMessage.Flags.EXPIRATION_TIMER_UPDATE_VALUE) != 0 //TODO validate that 'and' operator equivalent to Swift '&'
+            if (!isExpirationTimerUpdate) return null
+            val duration = dataMessageProto.expireTimer
+            return ExpirationTimerUpdate(duration)
+        }
+    }
+
+    //constructor
+    internal constructor(duration: Int) : this() {
+        this.duration = duration
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        return duration != null
+    }
+
+    override fun toProto(): SignalServiceProtos.Content? {
+        val duration = duration
+        if (duration == null) {
+            Log.w(TAG, "Couldn't construct expiration timer update proto from: $this")
+            return null
+        }
+        val dataMessageProto = SignalServiceProtos.DataMessage.newBuilder()
+        dataMessageProto.flags = SignalServiceProtos.DataMessage.Flags.EXPIRATION_TIMER_UPDATE_VALUE
+        dataMessageProto.expireTimer = duration
+        val contentProto = SignalServiceProtos.Content.newBuilder()
+        try {
+            contentProto.dataMessage = dataMessageProto.build()
+            return contentProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct expiration timer update proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/ReadReceipt.kt

@@ -1,4 +1,53 @@
-package org.session.messaging.messages.control
+package org.session.libsession.messaging.messages.control
 
-class ReadReceipt : ControlMessage() {
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class ReadReceipt() : ControlMessage() {
+
+    var timestamps: LongArray? = null
+
+    companion object {
+        const val TAG = "ReadReceipt"
+
+        fun fromProto(proto: SignalServiceProtos.Content): ReadReceipt? {
+            val receiptProto = proto.receiptMessage ?: return null
+            if (receiptProto.type != SignalServiceProtos.ReceiptMessage.Type.READ) return null
+            val timestamps = receiptProto.timestampList
+            if (timestamps.isEmpty()) return null
+            return ReadReceipt(timestamps = timestamps.toLongArray())
+        }
+    }
+
+    //constructor
+    internal constructor(timestamps: LongArray?) : this() {
+        this.timestamps = timestamps
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        val timestamps = timestamps ?: return false
+        if (timestamps.isNotEmpty()) { return true }
+        return false
+    }
+
+    override fun toProto(): SignalServiceProtos.Content? {
+        val timestamps = timestamps
+        if (timestamps == null) {
+            Log.w(ExpirationTimerUpdate.TAG, "Couldn't construct read receipt proto from: $this")
+            return null
+        }
+        val receiptProto = SignalServiceProtos.ReceiptMessage.newBuilder()
+        receiptProto.type = SignalServiceProtos.ReceiptMessage.Type.READ
+        receiptProto.addAllTimestamp(timestamps.asIterable())
+        val contentProto = SignalServiceProtos.Content.newBuilder()
+        try {
+            contentProto.receiptMessage = receiptProto.build()
+            return contentProto.build()
+        } catch (e: Exception) {
+            Log.w(ExpirationTimerUpdate.TAG, "Couldn't construct read receipt proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/TypingIndicator.kt

@@ -1,4 +1,75 @@
-package org.session.messaging.messages.control
+package org.session.libsession.messaging.messages.control
 
-class TypingIndicator : ControlMessage() {
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class TypingIndicator() : ControlMessage() {
+
+    companion object {
+        const val TAG = "TypingIndicator"
+
+        //val ttl:  30 * 1000 //TODO
+
+        fun fromProto(proto: SignalServiceProtos.Content): TypingIndicator? {
+            val typingIndicatorProto = proto.typingMessage ?: return null
+            val kind = Kind.fromProto(typingIndicatorProto.action)
+            return TypingIndicator(kind = kind)
+        }
+    }
+
+    // Kind enum
+    enum class Kind {
+        STARTED,
+        STOPPED,
+        ;
+
+        companion object {
+            @JvmStatic
+            fun fromProto(proto: SignalServiceProtos.TypingMessage.Action): Kind =
+                when (proto) {
+                    SignalServiceProtos.TypingMessage.Action.STARTED -> STARTED
+                    SignalServiceProtos.TypingMessage.Action.STOPPED -> STOPPED
+                }
+        }
+
+        fun toProto(): SignalServiceProtos.TypingMessage.Action {
+            when (this) {
+                STARTED -> return SignalServiceProtos.TypingMessage.Action.STARTED
+                STOPPED -> return SignalServiceProtos.TypingMessage.Action.STOPPED
+            }
+        }
+    }
+
+    var kind: Kind? = null
+
+    //constructor
+    internal constructor(kind: Kind) : this() {
+        this.kind = kind
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        return kind != null
+    }
+
+    override fun toProto(): SignalServiceProtos.Content? {
+        val timestamp = sentTimestamp
+        val kind = kind
+        if (timestamp == null || kind == null) {
+            Log.w(TAG, "Couldn't construct typing indicator proto from: $this")
+            return null
+        }
+        val typingIndicatorProto = SignalServiceProtos.TypingMessage.newBuilder()
+        typingIndicatorProto.timestamp = timestamp
+        typingIndicatorProto.action = kind.toProto()
+        val contentProto = SignalServiceProtos.Content.newBuilder()
+        try {
+            contentProto.typingMessage = typingIndicatorProto.build()
+            return contentProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct typing indicator proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/unused/NullMessage.kt

@@ -1,6 +1,35 @@
-package org.session.messaging.messages.control.unused
+package org.session.libsession.messaging.messages.control.unused
 
-import org.session.messaging.messages.control.ControlMessage
+import com.google.protobuf.ByteString
+import org.session.libsession.messaging.messages.control.ControlMessage
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import java.security.SecureRandom
 
-class NullMessage : ControlMessage() {
+class NullMessage() : ControlMessage() {
+
+    companion object {
+        const val TAG = "NullMessage"
+
+        fun fromProto(proto: SignalServiceProtos.Content): NullMessage? {
+            if (proto.nullMessage == null) return null
+            return NullMessage()
+        }
+    }
+
+    override fun toProto(): SignalServiceProtos.Content? {
+        val nullMessageProto = SignalServiceProtos.NullMessage.newBuilder()
+        val sr = SecureRandom()
+        val paddingSize = sr.nextInt(512)
+        val padding = ByteArray(paddingSize)
+        nullMessageProto.padding = ByteString.copyFrom(padding)
+        val contentProto = SignalServiceProtos.Content.newBuilder()
+        try {
+            contentProto.nullMessage = nullMessageProto.build()
+            return contentProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct null message proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/control/unused/SessionRequest.kt

@@ -1,6 +1,83 @@
-package org.session.messaging.messages.control.unused
+package org.session.libsession.messaging.messages.control.unused
 
-import org.session.messaging.messages.control.ControlMessage
+import com.google.protobuf.ByteString
+import org.session.libsession.messaging.Configuration
+import org.session.libsession.messaging.messages.control.ControlMessage
+import org.session.libsignal.libsignal.IdentityKey
+import org.session.libsignal.libsignal.ecc.DjbECPublicKey
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.libsignal.state.PreKeyBundle
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import java.security.SecureRandom
 
-class SessionRequest : ControlMessage() {
+class SessionRequest() : ControlMessage() {
+
+    var preKeyBundle: PreKeyBundle? = null
+
+    companion object {
+        const val TAG = "SessionRequest"
+
+        fun fromProto(proto: SignalServiceProtos.Content): SessionRequest? {
+            if (proto.nullMessage == null) return null
+            val preKeyBundleProto = proto.preKeyBundleMessage ?: return null
+            var registrationID: Int = 0
+            registrationID = Configuration.shared.storage.getOrGenerateRegistrationID() //TODO no implementation for getOrGenerateRegistrationID yet
+            //TODO just confirm if the above code does the equivalent to swift below:
+            /*iOS code: Configuration.shared.storage.with { transaction in
+                    registrationID = Configuration.shared.storage.getOrGenerateRegistrationID(using: transaction)
+            }*/
+            val preKeyBundle = PreKeyBundle(
+                    registrationID,
+                    1,
+                    preKeyBundleProto.preKeyId,
+                    DjbECPublicKey(preKeyBundleProto.preKey.toByteArray()),
+                    preKeyBundleProto.signedKeyId,
+                    DjbECPublicKey(preKeyBundleProto.signedKey.toByteArray()),
+                    preKeyBundleProto.signature.toByteArray(),
+                    IdentityKey(DjbECPublicKey(preKeyBundleProto.identityKey.toByteArray()))
+            )
+            return SessionRequest(preKeyBundle)
+        }
+    }
+
+    //constructor
+    internal constructor(preKeyBundle: PreKeyBundle) : this() {
+        this.preKeyBundle = preKeyBundle
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        return preKeyBundle != null
+    }
+
+    override fun toProto(): SignalServiceProtos.Content? {
+        val preKeyBundle = preKeyBundle
+        if (preKeyBundle == null) {
+            Log.w(TAG, "Couldn't construct session request proto from: $this")
+            return null
+        }
+        val nullMessageProto = SignalServiceProtos.NullMessage.newBuilder()
+        val sr = SecureRandom()
+        val paddingSize = sr.nextInt(512)
+        val padding = ByteArray(paddingSize)
+        nullMessageProto.padding = ByteString.copyFrom(padding)
+        val preKeyBundleProto = SignalServiceProtos.PreKeyBundleMessage.newBuilder()
+        preKeyBundleProto.identityKey = ByteString.copyFrom(preKeyBundle.identityKey.publicKey.serialize())
+        preKeyBundleProto.deviceId = preKeyBundle.deviceId
+        preKeyBundleProto.preKeyId = preKeyBundle.preKeyId
+        preKeyBundleProto.preKey = ByteString.copyFrom(preKeyBundle.preKey.serialize())
+        preKeyBundleProto.signedKeyId = preKeyBundle.signedPreKeyId
+        preKeyBundleProto.signedKey = ByteString.copyFrom(preKeyBundle.signedPreKey.serialize())
+        preKeyBundleProto.signature = ByteString.copyFrom(preKeyBundle.signedPreKeySignature)
+        val contentProto = SignalServiceProtos.Content.newBuilder()
+        try {
+            contentProto.nullMessage = nullMessageProto.build()
+            contentProto.preKeyBundleMessage = preKeyBundleProto.build()
+            return contentProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct session request proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/visible/Attachment.kt

@@ -0,0 +1,69 @@
+package org.session.libsession.messaging.messages.visible
+
+import android.util.Size
+import android.webkit.MimeTypeMap
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import java.io.File
+
+class Attachment : VisibleMessageProto<SignalServiceProtos.AttachmentPointer?>() {
+
+    var fileName: String? = null
+    var contentType: String? = null
+    var key: ByteArray? = null
+    var digest: ByteArray? = null
+    var kind: Kind? = null
+    var caption: String? = null
+    var size: Size? = null
+    var sizeInBytes: Int? = 0
+    var url: String? = null
+
+    companion object {
+        fun fromProto(proto: SignalServiceProtos.AttachmentPointer): Attachment? {
+            val result = Attachment()
+            result.fileName = proto.fileName
+            fun inferContentType(): String {
+                val fileName = result.fileName ?: return "application/octet-stream" //TODO find equivalent to OWSMimeTypeApplicationOctetStream
+                val fileExtension = File(fileName).extension
+                val mimeTypeMap = MimeTypeMap.getSingleton()
+                return mimeTypeMap.getMimeTypeFromExtension(fileExtension) ?: "application/octet-stream" //TODO check that it's correct
+            }
+            result.contentType = proto.contentType ?: inferContentType()
+            result.key = proto.key.toByteArray()
+            result.digest = proto.digest.toByteArray()
+            val kind: Kind
+            if (proto.hasFlags() && (proto.flags and SignalServiceProtos.AttachmentPointer.Flags.VOICE_MESSAGE_VALUE) > 0) { //TODO validate that 'and' operator = swift '&'
+                kind = Kind.VOICEMESSAGE
+            } else {
+                kind = Kind.GENERIC
+            }
+            result.kind = kind
+            result.caption = if (proto.hasCaption()) proto.caption else null
+            val size: Size
+            if (proto.hasWidth() && proto.width > 0 && proto.hasHeight() && proto.height > 0) {
+                size = Size(proto.width, proto.height)
+            } else {
+                size = Size(0,0) //TODO check that it's equivalent to swift: CGSize.zero
+            }
+            result.size = size
+            result.sizeInBytes = if (proto.size > 0) proto.size else null
+            result. url = proto.url
+            return result
+        }
+    }
+
+    enum class Kind {
+        VOICEMESSAGE,
+        GENERIC
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        // key and digest can be nil for open group attachments
+        return (contentType != null && kind != null && size != null && sizeInBytes != null && url != null)
+    }
+
+    override fun toProto(transaction: String): SignalServiceProtos.AttachmentPointer? {
+        TODO("Not implemented")
+    }
+}

libsession/src/main/java/org/session/libsession/messaging/messages/visible/Contact.kt

@@ -1,4 +1,16 @@
-package org.session.messaging.messages.visible
+package org.session.libsession.messaging.messages.visible
 
-internal class Contact {
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class Contact : VisibleMessageProto<SignalServiceProtos.DataMessage.Contact?>() {
+
+    companion object {
+        fun fromProto(proto: SignalServiceProtos.Content): Contact? {
+            TODO("Not yet implemented")
+        }
+    }
+
+    override fun toProto(transaction: String): SignalServiceProtos.DataMessage.Contact? {
+        TODO("Not yet implemented")
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/visible/LinkPreview.kt

@@ -1,4 +1,57 @@
-package org.session.messaging.messages.visible
+package org.session.libsession.messaging.messages.visible
 
-internal class LinkPreview {
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class LinkPreview() : VisibleMessageProto<SignalServiceProtos.DataMessage.Preview?>(){
+
+    var title: String? = null
+    var url: String? = null
+    var attachmentID: String? = null
+
+    companion object {
+        const val TAG = "LinkPreview"
+
+        fun fromProto(proto: SignalServiceProtos.DataMessage.Preview): LinkPreview? {
+            val title = proto.title
+            val url = proto.url
+            return LinkPreview(title, url, null)
+        }
+    }
+
+    //constructor
+    internal constructor(title: String?, url: String, attachmentID: String?) : this() {
+        this.title = title
+        this.url = url
+        this.attachmentID = attachmentID
+    }
+
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        return (title != null && url != null && attachmentID != null)
+    }
+
+    override fun toProto(transaction: String): SignalServiceProtos.DataMessage.Preview? {
+        val url = url
+        if (url == null) {
+            Log.w(TAG, "Couldn't construct link preview proto from: $this")
+            return null
+        }
+        val linkPreviewProto = SignalServiceProtos.DataMessage.Preview.newBuilder()
+        linkPreviewProto.url = url
+        title?.let { linkPreviewProto.title = title }
+        val attachmentID = attachmentID
+        attachmentID?.let {
+            //TODO database stuff
+        }
+        // Build
+        try {
+            return linkPreviewProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct link preview proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/visible/Profile.kt

@@ -1,4 +1,64 @@
-package org.session.messaging.messages.visible
+package org.session.libsession.messaging.messages.visible
 
-internal class Profile {
+import com.google.protobuf.ByteString
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class Profile() : VisibleMessageProto<SignalServiceProtos.DataMessage?>() {
+
+    var displayName: String? = null
+    var profileKey: ByteArray? = null
+    var profilePictureURL: String? = null
+
+    companion object {
+        const val TAG = "Profile"
+
+        fun fromProto(proto: SignalServiceProtos.DataMessage): Profile? {
+            val profileProto = proto.profile ?: return null
+            val displayName = profileProto.displayName ?: return null
+            val profileKey = proto.profileKey
+            val profilePictureURL = profileProto.profilePictureURL
+            profileKey?.let {
+                val profilePictureURL = profilePictureURL
+                profilePictureURL?.let {
+                    return Profile(displayName = displayName, profileKey = profileKey.toByteArray(), profilePictureURL = profilePictureURL)
+                }
+            }
+            return Profile(displayName)
+        }
+    }
+
+    //constructor
+    internal constructor(displayName: String, profileKey: ByteArray? = null, profilePictureURL: String? = null) : this() {
+        this.displayName = displayName
+        this.profileKey = profileKey
+        this.profilePictureURL = profilePictureURL
+    }
+
+    fun toSSProto(): SignalServiceProtos.DataMessage? {
+        return this.toProto("")
+    }
+
+    override fun toProto(transaction: String): SignalServiceProtos.DataMessage? {
+        val displayName = displayName
+        if (displayName == null) {
+            Log.w(TAG, "Couldn't construct link preview proto from: $this")
+            return null
+        }
+        val dataMessageProto = SignalServiceProtos.DataMessage.newBuilder()
+        val profileProto = SignalServiceProtos.LokiUserProfile.newBuilder()
+        profileProto.displayName = displayName
+        val profileKey = profileKey
+        profileKey?.let { dataMessageProto.profileKey = ByteString.copyFrom(profileKey) }
+        val profilePictureURL = profilePictureURL
+        profilePictureURL?.let { profileProto.profilePictureURL = profilePictureURL }
+        // Build
+        try {
+            dataMessageProto.profile = profileProto.build()
+            return dataMessageProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct profile proto from: $this")
+            return null
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/visible/Quote.kt

@@ -1,4 +1,72 @@
-package org.session.messaging.messages.visible
+package org.session.libsession.messaging.messages.visible
 
-internal class Quote {
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class Quote() : VisibleMessageProto<SignalServiceProtos.DataMessage.Quote?>() {
+
+    var timestamp: Long? = 0
+    var publicKey: String? = null
+    var text: String? = null
+    var attachmentID: String? = null
+
+    companion object {
+        const val TAG = "Quote"
+
+        fun fromProto(proto: SignalServiceProtos.DataMessage.Quote): Quote? {
+            val timestamp = proto.id
+            val publicKey = proto.author
+            val text = proto.text
+            return Quote(timestamp, publicKey, text, null)
+        }
+    }
+
+    //constructor
+    internal constructor(timestamp: Long, publicKey: String, text: String?, attachmentID: String?) : this() {
+        this.timestamp = timestamp
+        this.publicKey = publicKey
+        this.text = text
+        this.attachmentID = attachmentID
+    }
+
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        return (timestamp != null && publicKey != null)
+    }
+
+    override fun toProto(transaction: String): SignalServiceProtos.DataMessage.Quote? {
+        val timestamp = timestamp
+        val publicKey = publicKey
+        if (timestamp == null || publicKey == null) {
+            Log.w(TAG, "Couldn't construct quote proto from: $this")
+            return null
+        }
+        val quoteProto = SignalServiceProtos.DataMessage.Quote.newBuilder()
+        quoteProto.id = timestamp
+        quoteProto.author = publicKey
+        text?.let { quoteProto.text = text }
+        addAttachmentsIfNeeded(quoteProto, transaction)
+        // Build
+        try {
+            return quoteProto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct quote proto from: $this")
+            return null
+        }
+    }
+
+    private fun addAttachmentsIfNeeded(quoteProto: SignalServiceProtos.DataMessage.Quote.Builder, transaction: String) {
+        val attachmentID = attachmentID ?: return
+        //TODO databas stuff
+        val quotedAttachmentProto = SignalServiceProtos.DataMessage.Quote.QuotedAttachment.newBuilder()
+        //TODO more database related stuff
+        //quotedAttachmentProto.contentType =
+        try {
+            quoteProto.addAttachments(quotedAttachmentProto.build())
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct quoted attachment proto from: $this")
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/messages/visible/VisibleMessage.kt

@@ -1,6 +1,102 @@
-package org.session.messaging.messages.visible
+package org.session.libsession.messaging.messages.visible
 
-import org.session.messaging.messages.Message
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+class VisibleMessage() : VisibleMessageProto<SignalServiceProtos.Content?>() {
+
+    var text: String? = null
+    var attachmentIDs = ArrayList<String>()
+    var quote: Quote? = null
+    var linkPreview: LinkPreview? = null
+    var contact: Contact? = null
+    var profile: Profile? = null
+
+    companion object {
+        const val TAG = "BaseVisibleMessage"
+
+        fun fromProto(proto: SignalServiceProtos.Content): VisibleMessage? {
+            val dataMessage = proto.dataMessage ?: return null
+            val result = VisibleMessage()
+            result.text = dataMessage.body
+            // Attachments are handled in MessageReceiver
+            val quoteProto = dataMessage.quote
+            quoteProto?.let {
+                val quote = Quote.fromProto(quoteProto)
+                quote?.let { result.quote = quote }
+            }
+            val linkPreviewProto = dataMessage.previewList.first()
+            linkPreviewProto?.let {
+                val linkPreview = LinkPreview.fromProto(linkPreviewProto)
+                linkPreview?.let { result.linkPreview = linkPreview }
+            }
+            // TODO Contact
+            val profile = Profile.fromProto(dataMessage)
+            profile?.let { result.profile = profile }
+            return  result
+        }
+    }
+
+    // validation
+    override fun isValid(): Boolean {
+        if (!super.isValid()) return false
+        if (attachmentIDs.isNotEmpty()) return true
+        val text = text?.trim() ?: return false
+        if (text.isNotEmpty()) return true
+        return false
+    }
+
+    override fun toProto(transaction: String): SignalServiceProtos.Content? {
+        val proto = SignalServiceProtos.Content.newBuilder()
+        var attachmentIDs = this.attachmentIDs
+        val dataMessage: SignalServiceProtos.DataMessage.Builder
+        // Profile
+        val profile = profile
+        val profileProto = profile?.toSSProto()
+        if (profileProto != null) {
+            dataMessage = profileProto.toBuilder()
+        } else {
+            dataMessage = SignalServiceProtos.DataMessage.newBuilder()
+        }
+        // Text
+        text?.let { dataMessage.body = text }
+        // Quote
+        val quotedAttachmentID = quote?.attachmentID
+        quotedAttachmentID?.let {
+            val index = attachmentIDs.indexOf(quotedAttachmentID)
+            if (index >= 0) { attachmentIDs.removeAt(index) }
+        }
+        val quote = quote
+        quote?.let {
+            val quoteProto = quote.toProto(transaction)
+            if (quoteProto != null) dataMessage.quote = quoteProto
+        }
+        //Link preview
+        val linkPreviewAttachmentID = linkPreview?.attachmentID
+        linkPreviewAttachmentID?.let {
+            val index = attachmentIDs.indexOf(quotedAttachmentID)
+            if (index >= 0) { attachmentIDs.removeAt(index) }
+        }
+        val linkPreview = linkPreview
+        linkPreview?.let {
+            val linkPreviewProto = linkPreview.toProto(transaction)
+            linkPreviewProto?.let {
+                dataMessage.addAllPreview(listOf(linkPreviewProto))
+            }
+        }
+        //Attachments
+        // TODO I'm blocking on that one...
+        //swift: let attachments = attachmentIDs.compactMap { TSAttachmentStream.fetch(uniqueId: $0, transaction: transaction) }
+
+        // TODO Contact
+        // Build
+        try {
+            proto.dataMessage = dataMessage.build()
+            return proto.build()
+        } catch (e: Exception) {
+            Log.w(TAG, "Couldn't construct visible message proto from: $this")
+            return null
+        }
+    }
 
-class VisibleMessage : Message() {
 }

libsession/src/main/java/org/session/libsession/messaging/messages/visible/VisibleMessageProto.kt

@@ -0,0 +1,15 @@
+package org.session.libsession.messaging.messages.visible
+
+import org.session.libsession.messaging.messages.Message
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+
+abstract class VisibleMessageProto<out T: com.google.protobuf.MessageOrBuilder?> : Message() {
+
+    abstract fun toProto(transaction: String): T
+
+    final override fun toProto(): SignalServiceProtos.Content? {
+        //we don't need to implement this method in subclasses
+        //TODO it just needs an equivalent to swift: preconditionFailure("Use toProto(using:) if that exists...
+        TODO("Not implemented")
+    }
+}

libsession/src/main/java/org/session/libsession/messaging/messages/visible/attachments/Attachment.kt

@@ -1,4 +0,0 @@
-package org.session.messaging.messages.visible.attachments
-
-internal class Attachment {
-}

libsession/src/main/java/org/session/libsession/messaging/opengroups/OpenGroup.kt

@@ -0,0 +1,37 @@
+package org.session.libsession.messaging.opengroups
+
+import org.session.libsignal.service.internal.util.JsonUtil
+
+public data class OpenGroup(
+    public val channel: Long,
+    private val serverURL: String,
+    public val displayName: String,
+    public val isDeletable: Boolean
+) {
+    public val server get() = serverURL.toLowerCase()
+    public val id get() = getId(channel, server)
+
+    companion object {
+
+        @JvmStatic fun getId(channel: Long, server: String): String {
+            return "$server.$channel"
+        }
+
+        @JvmStatic fun fromJSON(jsonAsString: String): OpenGroup? {
+            try {
+                val json = JsonUtil.fromJson(jsonAsString)
+                val channel = json.get("channel").asLong()
+                val server = json.get("server").asText().toLowerCase()
+                val displayName = json.get("displayName").asText()
+                val isDeletable = json.get("isDeletable").asBoolean()
+                return OpenGroup(channel, server, displayName, isDeletable)
+            } catch (e: Exception) {
+                return null
+            }
+        }
+    }
+
+    public fun toJSON(): Map<String, Any> {
+        return mapOf( "channel" to channel, "server" to server, "displayName" to displayName, "isDeletable" to isDeletable )
+    }
+}

libsession/src/main/java/org/session/libsession/messaging/opengroups/OpenGroupAPI.kt

@@ -0,0 +1,381 @@
+package org.session.libsession.messaging.opengroups
+
+import nl.komponents.kovenant.Kovenant
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.deferred
+import nl.komponents.kovenant.functional.map
+import nl.komponents.kovenant.then
+import org.session.libsession.messaging.Configuration
+
+import org.session.libsession.messaging.utilities.DotNetAPI
+import org.session.libsession.messaging.fileserver.FileServerAPI
+import org.session.libsession.snode.SnodeAPI
+
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.internal.util.Hex
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsignal.service.loki.utilities.DownloadUtilities
+import org.session.libsignal.service.loki.utilities.createContext
+import org.session.libsignal.service.loki.utilities.hexEncodedPublicKey
+import org.session.libsignal.service.loki.utilities.retryIfNeeded
+import java.io.ByteArrayOutputStream
+import java.text.SimpleDateFormat
+import java.util.*
+
+object OpenGroupAPI: DotNetAPI() {
+
+    private val moderators: HashMap<String, HashMap<Long, Set<String>>> = hashMapOf() // Server URL to (channel ID to set of moderator IDs)
+    val sharedContext = Kovenant.createContext("LokiPublicChatAPISharedContext")
+
+    // region Settings
+    private val fallbackBatchCount = 64
+    private val maxRetryCount = 8
+    // endregion
+
+    // region Convenience
+    private val channelInfoType = "net.patter-app.settings"
+    private val attachmentType = "net.app.core.oembed"
+    @JvmStatic
+    public val openGroupMessageType = "network.loki.messenger.publicChat"
+    @JvmStatic
+    public val profilePictureType = "network.loki.messenger.avatar"
+
+    fun getDefaultChats(): List<OpenGroup> {
+        return listOf() // Don't auto-join any open groups right now
+    }
+
+    public fun isUserModerator(hexEncodedPublicKey: String, channel: Long, server: String): Boolean {
+        if (moderators[server] != null && moderators[server]!![channel] != null) {
+            return moderators[server]!![channel]!!.contains(hexEncodedPublicKey)
+        }
+        return false
+    }
+    // endregion
+
+    // region Public API
+    public fun getMessages(channel: Long, server: String): Promise<List<OpenGroupMessage>, Exception> {
+        Log.d("Loki", "Getting messages for open group with ID: $channel on server: $server.")
+        val storage = Configuration.shared.storage
+        val parameters = mutableMapOf<String, Any>( "include_annotations" to 1 )
+        val lastMessageServerID = storage.getLastMessageServerID(channel, server)
+        if (lastMessageServerID != null) {
+            parameters["since_id"] = lastMessageServerID
+        } else {
+            parameters["count"] = fallbackBatchCount
+            parameters["include_deleted"] = 0
+        }
+        return execute(HTTPVerb.GET, server, "channels/$channel/messages", parameters = parameters).then(sharedContext) { json ->
+            try {
+                val data = json["data"] as List<Map<*, *>>
+                val messages = data.mapNotNull { message ->
+                    try {
+                        val isDeleted = message["is_deleted"] as? Boolean ?: false
+                        if (isDeleted) { return@mapNotNull null }
+                        // Ignore messages without annotations
+                        if (message["annotations"] == null) { return@mapNotNull null }
+                        val annotation = (message["annotations"] as List<Map<*, *>>).find {
+                            ((it["type"] as? String ?: "") == openGroupMessageType) && it["value"] != null
+                        } ?: return@mapNotNull null
+                        val value = annotation["value"] as Map<*, *>
+                        val serverID = message["id"] as? Long ?: (message["id"] as? Int)?.toLong() ?: (message["id"] as String).toLong()
+                        val user = message["user"] as Map<*, *>
+                        val publicKey = user["username"] as String
+                        val displayName = user["name"] as? String ?: "Anonymous"
+                        var profilePicture: OpenGroupMessage.ProfilePicture? = null
+                        if (user["annotations"] != null) {
+                            val profilePictureAnnotation = (user["annotations"] as List<Map< *, *>>).find {
+                                ((it["type"] as? String ?: "") == profilePictureType) && it["value"] != null
+                            }
+                            val profilePictureAnnotationValue = profilePictureAnnotation?.get("value") as? Map<*, *>
+                            if (profilePictureAnnotationValue != null && profilePictureAnnotationValue["profileKey"] != null && profilePictureAnnotationValue["url"] != null) {
+                                try {
+                                    val profileKey = Base64.decode(profilePictureAnnotationValue["profileKey"] as String)
+                                    val url = profilePictureAnnotationValue["url"] as String
+                                    profilePicture = OpenGroupMessage.ProfilePicture(profileKey, url)
+                                } catch (e: Exception) {}
+                            }
+                        }
+                        @Suppress("NAME_SHADOWING") val body = message["text"] as String
+                        val timestamp = value["timestamp"] as? Long ?: (value["timestamp"] as? Int)?.toLong() ?: (value["timestamp"] as String).toLong()
+                        var quote: OpenGroupMessage.Quote? = null
+                        if (value["quote"] != null) {
+                            val replyTo = message["reply_to"] as? Long ?: (message["reply_to"] as? Int)?.toLong() ?: (message["reply_to"] as String).toLong()
+                            val quoteAnnotation = value["quote"] as? Map<*, *>
+                            val quoteTimestamp = quoteAnnotation?.get("id") as? Long ?: (quoteAnnotation?.get("id") as? Int)?.toLong() ?: (quoteAnnotation?.get("id") as? String)?.toLong() ?: 0L
+                            val author = quoteAnnotation?.get("author") as? String
+                            val text = quoteAnnotation?.get("text") as? String
+                            quote = if (quoteTimestamp > 0L && author != null && text != null) OpenGroupMessage.Quote(quoteTimestamp, author, text, replyTo) else null
+                        }
+                        val attachmentsAsJSON = (message["annotations"] as List<Map<*, *>>).filter {
+                            ((it["type"] as? String ?: "") == attachmentType) && it["value"] != null
+                        }
+                        val attachments = attachmentsAsJSON.mapNotNull { it["value"] as? Map<*, *> }.mapNotNull { attachmentAsJSON ->
+                            try {
+                                val kindAsString = attachmentAsJSON["lokiType"] as String
+                                val kind = OpenGroupMessage.Attachment.Kind.values().first { it.rawValue == kindAsString }
+                                val id = attachmentAsJSON["id"] as? Long ?: (attachmentAsJSON["id"] as? Int)?.toLong() ?: (attachmentAsJSON["id"] as String).toLong()
+                                val contentType = attachmentAsJSON["contentType"] as String
+                                val size = attachmentAsJSON["size"] as? Int ?: (attachmentAsJSON["size"] as? Long)?.toInt() ?: (attachmentAsJSON["size"] as String).toInt()
+                                val fileName = attachmentAsJSON["fileName"] as String
+                                val flags = 0
+                                val url = attachmentAsJSON["url"] as String
+                                val caption = attachmentAsJSON["caption"] as? String
+                                val linkPreviewURL = attachmentAsJSON["linkPreviewUrl"] as? String
+                                val linkPreviewTitle = attachmentAsJSON["linkPreviewTitle"] as? String
+                                if (kind == OpenGroupMessage.Attachment.Kind.LinkPreview && (linkPreviewURL == null || linkPreviewTitle == null)) {
+                                    null
+                                } else {
+                                    OpenGroupMessage.Attachment(kind, server, id, contentType, size, fileName, flags, 0, 0, caption, url, linkPreviewURL, linkPreviewTitle)
+                                }
+                            } catch (e: Exception) {
+                                Log.d("Loki","Couldn't parse attachment due to error: $e.")
+                                null
+                            }
+                        }
+                        // Set the last message server ID here to avoid the situation where a message doesn't have a valid signature and this function is called over and over
+                        @Suppress("NAME_SHADOWING") val lastMessageServerID = storage.getLastMessageServerID(channel, server)
+                        if (serverID > lastMessageServerID ?: 0) { storage.setLastMessageServerID(channel, server, serverID) }
+                        val hexEncodedSignature = value["sig"] as String
+                        val signatureVersion = value["sigver"] as? Long ?: (value["sigver"] as? Int)?.toLong() ?: (value["sigver"] as String).toLong()
+                        val signature = OpenGroupMessage.Signature(Hex.fromStringCondensed(hexEncodedSignature), signatureVersion)
+                        val format = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US)
+                        format.timeZone = TimeZone.getTimeZone("GMT")
+                        val dateAsString = message["created_at"] as String
+                        val serverTimestamp = format.parse(dateAsString).time
+                        // Verify the message
+                        val groupMessage = OpenGroupMessage(serverID, publicKey, displayName, body, timestamp, openGroupMessageType, quote, attachments, profilePicture, signature, serverTimestamp)
+                        if (groupMessage.hasValidSignature()) groupMessage else null
+                    } catch (exception: Exception) {
+                        Log.d("Loki", "Couldn't parse message for open group with ID: $channel on server: $server from: ${JsonUtil.toJson(message)}. Exception: ${exception.message}")
+                        return@mapNotNull null
+                    }
+                }.sortedBy { it.serverTimestamp }
+                messages
+            } catch (exception: Exception) {
+                Log.d("Loki", "Couldn't parse messages for open group with ID: $channel on server: $server.")
+                throw exception
+            }
+        }
+    }
+
+    public fun getDeletedMessageServerIDs(channel: Long, server: String): Promise<List<Long>, Exception> {
+        Log.d("Loki", "Getting deleted messages for open group with ID: $channel on server: $server.")
+        val storage = Configuration.shared.storage
+        val parameters = mutableMapOf<String, Any>()
+        val lastDeletionServerID = storage.getLastDeletionServerID(channel, server)
+        if (lastDeletionServerID != null) {
+            parameters["since_id"] = lastDeletionServerID
+        } else {
+            parameters["count"] = fallbackBatchCount
+        }
+        return execute(HTTPVerb.GET, server, "loki/v1/channel/$channel/deletes", parameters = parameters).then(sharedContext) { json ->
+            try {
+                val deletedMessageServerIDs = (json["data"] as List<Map<*, *>>).mapNotNull { deletion ->
+                    try {
+                        val serverID = deletion["id"] as? Long ?: (deletion["id"] as? Int)?.toLong() ?: (deletion["id"] as String).toLong()
+                        val messageServerID = deletion["message_id"] as? Long ?: (deletion["message_id"] as? Int)?.toLong() ?: (deletion["message_id"] as String).toLong()
+                        @Suppress("NAME_SHADOWING") val lastDeletionServerID = storage.getLastDeletionServerID(channel, server)
+                        if (serverID > (lastDeletionServerID ?: 0)) { storage.setLastDeletionServerID(channel, server, serverID) }
+                        messageServerID
+                    } catch (exception: Exception) {
+                        Log.d("Loki", "Couldn't parse deleted message for open group with ID: $channel on server: $server. Exception: ${exception.message}")
+                        return@mapNotNull null
+                    }
+                }
+                deletedMessageServerIDs
+            } catch (exception: Exception) {
+                Log.d("Loki", "Couldn't parse deleted messages for open group with ID: $channel on server: $server.")
+                throw exception
+            }
+        }
+    }
+
+    public fun sendMessage(message: OpenGroupMessage, channel: Long, server: String): Promise<OpenGroupMessage, Exception> {
+        val deferred = deferred<OpenGroupMessage, Exception>()
+        val storage = Configuration.shared.storage
+        val userKeyPair = storage.getUserKeyPair() ?: throw Error.Generic
+        val userDisplayName = storage.getUserDisplayName() ?: throw Error.Generic
+        Thread {
+            val signedMessage = message.sign(userKeyPair.privateKey.serialize())
+            if (signedMessage == null) {
+                deferred.reject(Error.SigningFailed)
+            } else {
+                retryIfNeeded(maxRetryCount) {
+                    Log.d("Loki", "Sending message to open group with ID: $channel on server: $server.")
+                    val parameters = signedMessage.toJSON()
+                    execute(HTTPVerb.POST, server, "channels/$channel/messages", parameters = parameters).then(sharedContext) { json ->
+                        try {
+                            val data = json["data"] as Map<*, *>
+                            val serverID = (data["id"] as? Long) ?: (data["id"] as? Int)?.toLong() ?: (data["id"] as String).toLong()
+                            val text = data["text"] as String
+                            val format = SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSS'Z'", Locale.US)
+                            format.timeZone = TimeZone.getTimeZone("GMT")
+                            val dateAsString = data["created_at"] as String
+                            val timestamp = format.parse(dateAsString).time
+                            @Suppress("NAME_SHADOWING") val message = OpenGroupMessage(serverID, userKeyPair.hexEncodedPublicKey, userDisplayName, text, timestamp, openGroupMessageType, message.quote, message.attachments, null, signedMessage.signature, timestamp)
+                            message
+                        } catch (exception: Exception) {
+                            Log.d("Loki", "Couldn't parse message for open group with ID: $channel on server: $server.")
+                            throw exception
+                        }
+                    }
+                }.success {
+                    deferred.resolve(it)
+                }.fail {
+                    deferred.reject(it)
+                }
+            }
+        }.start()
+        return deferred.promise
+    }
+
+    public fun deleteMessage(messageServerID: Long, channel: Long, server: String, isSentByUser: Boolean): Promise<Long, Exception> {
+        return retryIfNeeded(maxRetryCount) {
+            val isModerationRequest = !isSentByUser
+            Log.d("Loki", "Deleting message with ID: $messageServerID from open group with ID: $channel on server: $server (isModerationRequest = $isModerationRequest).")
+            val endpoint = if (isSentByUser) "channels/$channel/messages/$messageServerID" else "loki/v1/moderation/message/$messageServerID"
+            execute(HTTPVerb.DELETE, server, endpoint, isJSONRequired = false).then {
+                Log.d("Loki", "Deleted message with ID: $messageServerID from open group with ID: $channel on server: $server.")
+                messageServerID
+            }
+        }
+    }
+
+    public fun deleteMessages(messageServerIDs: List<Long>, channel: Long, server: String, isSentByUser: Boolean): Promise<List<Long>, Exception> {
+        return retryIfNeeded(maxRetryCount) {
+            val isModerationRequest = !isSentByUser
+            val parameters = mapOf( "ids" to messageServerIDs.joinToString(",") )
+            Log.d("Loki", "Deleting messages with IDs: ${messageServerIDs.joinToString()} from open group with ID: $channel on server: $server (isModerationRequest = $isModerationRequest).")
+            val endpoint = if (isSentByUser) "loki/v1/messages" else "loki/v1/moderation/messages"
+            execute(HTTPVerb.DELETE, server, endpoint, parameters = parameters, isJSONRequired = false).then { json ->
+                Log.d("Loki", "Deleted messages with IDs: $messageServerIDs from open group with ID: $channel on server: $server.")
+                messageServerIDs
+            }
+        }
+    }
+
+    public fun getModerators(channel: Long, server: String): Promise<Set<String>, Exception> {
+        return execute(HTTPVerb.GET, server, "loki/v1/channel/$channel/get_moderators").then(sharedContext) { json ->
+            try {
+                @Suppress("UNCHECKED_CAST") val moderators = json["moderators"] as? List<String>
+                val moderatorsAsSet = moderators.orEmpty().toSet()
+                if (this.moderators[server] != null) {
+                    this.moderators[server]!![channel] = moderatorsAsSet
+                } else {
+                    this.moderators[server] = hashMapOf( channel to moderatorsAsSet )
+                }
+                moderatorsAsSet
+            } catch (exception: Exception) {
+                Log.d("Loki", "Couldn't parse moderators for open group with ID: $channel on server: $server.")
+                throw exception
+            }
+        }
+    }
+
+    public fun getChannelInfo(channel: Long, server: String): Promise<OpenGroupInfo, Exception> {
+        return retryIfNeeded(maxRetryCount) {
+            val parameters = mapOf( "include_annotations" to 1 )
+            execute(HTTPVerb.GET, server, "/channels/$channel", parameters = parameters).then(sharedContext) { json ->
+                try {
+                    val data = json["data"] as Map<*, *>
+                    val annotations = data["annotations"] as List<Map<*, *>>
+                    val annotation = annotations.find { (it["type"] as? String ?: "") == channelInfoType } ?: throw Error.ParsingFailed
+                    val info = annotation["value"] as Map<*, *>
+                    val displayName = info["name"] as String
+                    val countInfo = data["counts"] as Map<*, *>
+                    val memberCount = countInfo["subscribers"] as? Int ?: (countInfo["subscribers"] as? Long)?.toInt() ?: (countInfo["subscribers"] as String).toInt()
+                    val profilePictureURL = info["avatar"] as String
+                    val publicChatInfo = OpenGroupInfo(displayName, profilePictureURL, memberCount)
+                    Configuration.shared.storage.setUserCount(channel, server, memberCount)
+                    publicChatInfo
+                } catch (exception: Exception) {
+                    Log.d("Loki", "Couldn't parse info for open group with ID: $channel on server: $server.")
+                    throw exception
+                }
+            }
+        }
+    }
+
+    public fun updateProfileIfNeeded(channel: Long, server: String, groupID: String, info: OpenGroupInfo, isForcedUpdate: Boolean) {
+        val storage = Configuration.shared.storage
+        storage.setUserCount(channel, server, info.memberCount)
+        storage.updateTitle(groupID, info.displayName)
+        // Download and update profile picture if needed
+        val oldProfilePictureURL = storage.getOpenGroupProfilePictureURL(channel, server)
+        if (isForcedUpdate || oldProfilePictureURL != info.profilePictureURL) {
+            val profilePictureAsByteArray = downloadOpenGroupProfilePicture(server, info.profilePictureURL) ?: return
+            storage.updateProfilePicture(groupID, profilePictureAsByteArray)
+            storage.setOpenGroupProfilePictureURL(channel, server, info.profilePictureURL)
+        }
+    }
+
+    public fun downloadOpenGroupProfilePicture(server: String, endpoint: String): ByteArray? {
+        val url = "${server.removeSuffix("/")}/${endpoint.removePrefix("/")}"
+        Log.d("Loki", "Downloading open group profile picture from \"$url\".")
+        val outputStream = ByteArrayOutputStream()
+        try {
+            DownloadUtilities.downloadFile(outputStream, url, FileServerAPI.maxFileSize, null)
+            Log.d("Loki", "Open group profile picture was successfully loaded from \"$url\"")
+            return outputStream.toByteArray()
+        } catch (e: Exception) {
+            Log.d("Loki", "Failed to download open group profile picture from \"$url\" due to error: $e.")
+            return null
+        } finally {
+            outputStream.close()
+        }
+    }
+
+    public fun join(channel: Long, server: String): Promise<Unit, Exception> {
+        return retryIfNeeded(maxRetryCount) {
+            execute(HTTPVerb.POST, server, "/channels/$channel/subscribe").then {
+                Log.d("Loki", "Joined channel with ID: $channel on server: $server.")
+            }
+        }
+    }
+
+    public fun leave(channel: Long, server: String): Promise<Unit, Exception> {
+        return retryIfNeeded(maxRetryCount) {
+            execute(HTTPVerb.DELETE, server, "/channels/$channel/subscribe").then {
+                Log.d("Loki", "Left channel with ID: $channel on server: $server.")
+            }
+        }
+    }
+
+    public fun getDisplayNames(publicKeys: Set<String>, server: String): Promise<Map<String, String>, Exception> {
+        return getUserProfiles(publicKeys, server, false).map(sharedContext) { json ->
+            val mapping = mutableMapOf<String, String>()
+            for (user in json) {
+                if (user["username"] != null) {
+                    val publicKey = user["username"] as String
+                    val displayName = user["name"] as? String ?: "Anonymous"
+                    mapping[publicKey] = displayName
+                }
+            }
+            mapping
+        }
+    }
+
+    public fun setDisplayName(newDisplayName: String?, server: String): Promise<Unit, Exception> {
+        Log.d("Loki", "Updating display name on server: $server.")
+        val parameters = mapOf( "name" to (newDisplayName ?: "") )
+        return execute(HTTPVerb.PATCH, server, "users/me", parameters = parameters).map { Unit }
+    }
+
+    public fun setProfilePicture(server: String, profileKey: ByteArray, url: String?): Promise<Unit, Exception> {
+        return setProfilePicture(server, Base64.encodeBytes(profileKey), url)
+    }
+
+    public fun setProfilePicture(server: String, profileKey: String, url: String?): Promise<Unit, Exception> {
+        Log.d("Loki", "Updating profile picture on server: $server.")
+        val value = when (url) {
+            null -> null
+            else -> mapOf( "profileKey" to profileKey, "url" to url )
+        }
+        // TODO: This may actually completely replace the annotations, have to double check it
+        return setSelfAnnotation(server, profilePictureType, value).map { Unit }.fail {
+            Log.d("Loki", "Failed to update profile picture due to error: $it.")
+        }
+    }
+    // endregion
+}

libsession/src/main/java/org/session/libsession/messaging/opengroups/OpenGroupInfo.kt

@@ -0,0 +1,7 @@
+package org.session.libsession.messaging.opengroups
+
+public data class OpenGroupInfo (
+    public val displayName: String,
+    public val profilePictureURL: String,
+    public val memberCount: Int
+)

libsession/src/main/java/org/session/libsession/messaging/opengroups/OpenGroupMessage.kt

@@ -0,0 +1,242 @@
+package org.session.libsession.messaging.opengroups
+
+import org.session.libsession.messaging.Configuration
+import org.session.libsession.messaging.messages.visible.VisibleMessage
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.util.Hex
+import org.session.libsignal.service.loki.utilities.removing05PrefixIfNeeded
+import org.whispersystems.curve25519.Curve25519
+
+public data class OpenGroupMessage(
+        public val serverID: Long?,
+        public val senderPublicKey: String,
+        public val displayName: String,
+        public val body: String,
+        public val timestamp: Long,
+        public val type: String,
+        public val quote: Quote?,
+        public val attachments: List<Attachment>,
+        public val profilePicture: ProfilePicture?,
+        public val signature: Signature?,
+        public val serverTimestamp: Long,
+) {
+
+    // region Settings
+    companion object {
+        fun from(message: VisibleMessage, server: String): OpenGroupMessage? {
+            val storage = Configuration.shared.storage
+            val userPublicKey = storage.getUserPublicKey() ?: return null
+            // Validation
+            if (!message.isValid()) { return null } // Should be valid at this point
+            // Quote
+            val quote: Quote? = {
+                val quote = message.quote
+                if (quote != null && quote.isValid()) {
+                    val quotedMessageServerID = storage.getQuoteServerID(quote.id, quote.publicKey)
+                    Quote(quote.timestamp!!, quote.publicKey!!, quote.text!!, quotedMessageServerID)
+                } else {
+                    null
+                }
+            }()
+            // Message
+            val displayname = storage.getUserDisplayName() ?: "Anonymous"
+            val body = message.text ?: message.sentTimestamp.toString() // The back-end doesn't accept messages without a body so we use this as a workaround
+            val result = OpenGroupMessage(null, userPublicKey, displayname, body, message.sentTimestamp!!, OpenGroupAPI.openGroupMessageType, quote, mutableListOf(), null, null, 0)
+            // Link preview
+            val linkPreview = message.linkPreview
+            linkPreview?.let {
+                if (!linkPreview.isValid()) { return@let }
+                val attachment = linkPreview.getImage() ?: return@let
+                val openGroupLinkPreview = Attachment(
+                        Attachment.Kind.LinkPreview,
+                        server,
+                        attachment.getId(),
+                        attachment.getContentType(),
+                        attachment.getSize(),
+                        attachment.getFileName(),
+                        attachment.getFlags(),
+                        attachment.getWidth(),
+                        attachment.getHeight(),
+                        attachment.getCaption(),
+                        attachment.getUrl(),
+                        linkPreview.url,
+                        linkPreview.title)
+                result.attachments.add(openGroupLinkPreview)
+            }
+            // Attachments
+            val attachments = message.getAttachemnts().forEach {
+                val attachement = Attachment(
+                        Attachment.Kind.Attachment,
+                        server,
+                        it.getId(),
+                        it.getContentType(),
+                        it.getSize(),
+                        it.getFileName(),
+                        it.getFlags(),
+                        it.getWidth(),
+                        it.getHeight(),
+                        it.getCaption(),
+                        it.getUrl(),
+                        linkPreview.getUrl(),
+                        linkPreview.getTitle())
+                result.attachments.add(attachement)
+            }
+            // Return
+            return result
+        }
+
+        private val curve = Curve25519.getInstance(Curve25519.BEST)
+        private val signatureVersion: Long = 1
+        private val attachmentType = "net.app.core.oembed"
+    }
+    // endregion
+
+    // region Types
+    public data class ProfilePicture(
+            public val profileKey: ByteArray,
+            public val url: String,
+    )
+
+    public data class Quote(
+            public val quotedMessageTimestamp: Long,
+            public val quoteePublicKey: String,
+            public val quotedMessageBody: String,
+            public val quotedMessageServerID: Long? = null,
+    )
+
+    public data class Signature(
+            public val data: ByteArray,
+            public val version: Long,
+    )
+
+    public data class Attachment(
+            public val kind: Kind,
+            public val server: String,
+            public val serverID: Long,
+            public val contentType: String,
+            public val size: Int,
+            public val fileName: String,
+            public val flags: Int,
+            public val width: Int,
+            public val height: Int,
+            public val caption: String?,
+            public val url: String,
+            /**
+            Guaranteed to be non-`nil` if `kind` is `LinkPreview`.
+             */
+            public val linkPreviewURL: String?,
+            /**
+            Guaranteed to be non-`nil` if `kind` is `LinkPreview`.
+             */
+            public val linkPreviewTitle: String?,
+    ) {
+        public val dotNetAPIType = when {
+            contentType.startsWith("image") -> "photo"
+            contentType.startsWith("video") -> "video"
+            contentType.startsWith("audio") -> "audio"
+            else -> "other"
+        }
+
+        public enum class Kind(val rawValue: String) {
+            Attachment("attachment"), LinkPreview("preview")
+        }
+    }
+    // endregion
+
+    // region Initialization
+    constructor(hexEncodedPublicKey: String, displayName: String, body: String, timestamp: Long, type: String, quote: Quote?, attachments: List<Attachment>)
+        : this(null, hexEncodedPublicKey, displayName, body, timestamp, type, quote, attachments, null, null, 0)
+    // endregion
+
+    // region Crypto
+    internal fun sign(privateKey: ByteArray): OpenGroupMessage? {
+        val data = getValidationData(signatureVersion)
+        if (data == null) {
+            Log.d("Loki", "Failed to sign public chat message.")
+            return null
+        }
+        try {
+            val signatureData = curve.calculateSignature(privateKey, data)
+            val signature = Signature(signatureData, signatureVersion)
+            return copy(signature = signature)
+        } catch (e: Exception) {
+            Log.d("Loki", "Failed to sign public chat message due to error: ${e.message}.")
+            return null
+        }
+    }
+
+    internal fun hasValidSignature(): Boolean {
+        if (signature == null) { return false }
+        val data = getValidationData(signature.version) ?: return false
+        val publicKey = Hex.fromStringCondensed(senderPublicKey.removing05PrefixIfNeeded())
+        try {
+            return curve.verifySignature(publicKey, data, signature.data)
+        } catch (e: Exception) {
+            Log.d("Loki", "Failed to verify public chat message due to error: ${e.message}.")
+            return false
+        }
+    }
+    // endregion
+
+    // region Parsing
+    internal fun toJSON(): Map<String, Any> {
+        val value = mutableMapOf<String, Any>("timestamp" to timestamp)
+        if (quote != null) {
+            value["quote"] = mapOf("id" to quote.quotedMessageTimestamp, "author" to quote.quoteePublicKey, "text" to quote.quotedMessageBody)
+        }
+        if (signature != null) {
+            value["sig"] = Hex.toStringCondensed(signature.data)
+            value["sigver"] = signature.version
+        }
+        val annotation = mapOf("type" to type, "value" to value)
+        val annotations = mutableListOf(annotation)
+        attachments.forEach { attachment ->
+            val attachmentValue = mutableMapOf(
+                    // Fields required by the .NET API
+                    "version" to 1,
+                    "type" to attachment.dotNetAPIType,
+                    // Custom fields
+                    "lokiType" to attachment.kind.rawValue,
+                    "server" to attachment.server,
+                    "id" to attachment.serverID,
+                    "contentType" to attachment.contentType,
+                    "size" to attachment.size,
+                    "fileName" to attachment.fileName,
+                    "flags" to attachment.flags,
+                    "width" to attachment.width,
+                    "height" to attachment.height,
+                    "url" to attachment.url
+            )
+            if (attachment.caption != null) { attachmentValue["caption"] = attachment.caption }
+            if (attachment.linkPreviewURL != null) { attachmentValue["linkPreviewUrl"] = attachment.linkPreviewURL }
+            if (attachment.linkPreviewTitle != null) { attachmentValue["linkPreviewTitle"] = attachment.linkPreviewTitle }
+            val attachmentAnnotation = mapOf("type" to attachmentType, "value" to attachmentValue)
+            annotations.add(attachmentAnnotation)
+        }
+        val result = mutableMapOf("text" to body, "annotations" to annotations)
+        if (quote?.quotedMessageServerID != null) {
+            result["reply_to"] = quote.quotedMessageServerID
+        }
+        return result
+    }
+    // endregion
+
+    // region Convenience
+    private fun getValidationData(signatureVersion: Long): ByteArray? {
+        var string = "${body.trim()}$timestamp"
+        if (quote != null) {
+            string += "${quote.quotedMessageTimestamp}${quote.quoteePublicKey}${quote.quotedMessageBody.trim()}"
+            if (quote.quotedMessageServerID != null) {
+                string += "${quote.quotedMessageServerID}"
+            }
+        }
+        string += attachments.sortedBy { it.serverID }.map { it.serverID }.joinToString("")
+        string += "$signatureVersion"
+        try {
+            return string.toByteArray(Charsets.UTF_8)
+        } catch (exception: Exception) {
+            return null
+        }
+    }
+    // endregion
+}

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageReceiver.kt

@@ -1,4 +1,29 @@
-package org.session.messaging.sending_receiving
+package org.session.libsession.messaging.sending_receiving
 
 object MessageReceiver {
+    internal sealed class Error(val description: String) : Exception() {
+        object InvalidMessage: Error("Invalid message.")
+        object UnknownMessage: Error("Unknown message type.")
+        object UnknownEnvelopeType: Error("Unknown envelope type.")
+        object NoUserPublicKey: Error("Couldn't find user key pair.")
+        object NoData: Error("Received an empty envelope.")
+        object SenderBlocked: Error("Received a message from a blocked user.")
+        object NoThread: Error("Couldn't find thread for message.")
+        object SelfSend: Error("Message addressed at self.")
+        object ParsingFailed : Error("Couldn't parse ciphertext message.")
+        // Shared sender keys
+        object InvalidGroupPublicKey: Error("Invalid group public key.")
+        object NoGroupPrivateKey: Error("Missing group private key.")
+        object SharedSecretGenerationFailed: Error("Couldn't generate a shared secret.")
+
+        internal val isRetryable: Boolean = when (this) {
+            is InvalidMessage -> false
+            is UnknownMessage -> false
+            is UnknownEnvelopeType -> false
+            is NoData -> false
+            is SenderBlocked -> false
+            is SelfSend -> false
+            else -> true
+        }
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageReceiverDecryption.kt

@@ -1,4 +1,58 @@
-package org.session.messaging.sending_receiving
+package org.session.libsession.messaging.sending_receiving
+
+import org.session.libsession.messaging.Configuration
+import org.session.libsignal.service.api.push.SignalServiceAddress
+import org.session.libsignal.service.loki.crypto.LokiServiceCipher
+import org.session.libsession.messaging.sending_receiving.MessageReceiver.Error
+import org.session.libsession.utilities.AESGCM
+import org.whispersystems.curve25519.Curve25519
+import org.session.libsignal.libsignal.loki.ClosedGroupCiphertextMessage
+import org.session.libsignal.libsignal.util.Pair
+import org.session.libsignal.service.api.messages.SignalServiceEnvelope
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import org.session.libsignal.service.loki.protocol.closedgroups.SharedSenderKeysImplementation
+import org.session.libsignal.service.loki.utilities.toHexString
+import javax.crypto.Mac
+import javax.crypto.spec.SecretKeySpec
 
 object MessageReceiverDecryption {
+
+    internal fun decryptWithSignalProtocol(envelope: SignalServiceEnvelope): Pair<ByteArray, String> {
+        val storage = Configuration.shared.signalStorage
+        val certificateValidator = Configuration.shared.certificateValidator
+        val sskDatabase = Configuration.shared.sskDatabase
+        val sessionResetImp = Configuration.shared.sessionResetImp
+        val data = envelope.content
+        if (data.count() == 0) { throw Error.NoData }
+        val userPublicKey = Configuration.shared.storage.getUserPublicKey() ?: throw Error.NoUserPublicKey
+        val cipher = LokiServiceCipher(SignalServiceAddress(userPublicKey), storage, sskDatabase, sessionResetImp, certificateValidator)
+        val result = cipher.decrypt(envelope)
+    }
+
+    internal fun decryptWithSharedSenderKeys(envelope: SignalServiceEnvelope): Pair<ByteArray, String> {
+        // 1. ) Check preconditions
+        val groupPublicKey = envelope.source
+        if (!Configuration.shared.storage.isClosedGroup(groupPublicKey)) { throw Error.InvalidGroupPublicKey }
+        val data = envelope.content
+        if (data.count() == 0) { throw Error.NoData }
+        val groupPrivateKey = Configuration.shared.storage.getClosedGroupPrivateKey(groupPublicKey) ?: throw Error.NoGroupPrivateKey
+        // 2. ) Parse the wrapper
+        val wrapper = SignalServiceProtos.ClosedGroupCiphertextMessageWrapper.parseFrom(data)
+        val ivAndCiphertext = wrapper.ciphertext.toByteArray()
+        val ephemeralPublicKey = wrapper.ephemeralPublicKey.toByteArray()
+        // 3. ) Decrypt the data inside
+        val ephemeralSharedSecret = Curve25519.getInstance(Curve25519.BEST).calculateAgreement(ephemeralPublicKey, groupPrivateKey.serialize())
+        val mac = Mac.getInstance("HmacSHA256")
+        mac.init(SecretKeySpec("LOKI".toByteArray(), "HmacSHA256"))
+        val symmetricKey = mac.doFinal(ephemeralSharedSecret)
+        val closedGroupCiphertextMessageAsData = AESGCM.decrypt(ivAndCiphertext, symmetricKey)
+        // 4. ) Parse the closed group ciphertext message
+        val closedGroupCiphertextMessage = ClosedGroupCiphertextMessage.from(closedGroupCiphertextMessageAsData) ?: throw Error.ParsingFailed
+        val senderPublicKey = closedGroupCiphertextMessage.senderPublicKey.toHexString()
+        if (senderPublicKey == Configuration.shared.storage.getUserPublicKey()) { throw Error.SelfSend }
+        // 5. ) Use the info inside the closed group ciphertext message to decrypt the actual message content
+        val plaintext = SharedSenderKeysImplementation.shared.decrypt(closedGroupCiphertextMessage.ivAndCiphertext, groupPublicKey, senderPublicKey, closedGroupCiphertextMessage.keyIndex)
+        // 6. ) Return
+        return Pair(plaintext, senderPublicKey)
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageReceiverDelegate.kt

@@ -1,4 +1,4 @@
-package org.session.messaging.sending_receiving
+package org.session.libsession.messaging.sending_receiving
 
 interface MessageReceiverDelegate {
 }

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageSender.kt

@@ -1,4 +1,198 @@
-package org.session.messaging.sending_receiving
+package org.session.libsession.messaging.sending_receiving
+
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.deferred
+
+import org.session.libsession.messaging.Configuration
+import org.session.libsession.messaging.jobs.JobQueue
+import org.session.libsession.messaging.messages.Destination
+import org.session.libsession.messaging.messages.Message
+import org.session.libsession.messaging.messages.visible.VisibleMessage
+import org.session.libsession.messaging.jobs.NotifyPNServerJob
+import org.session.libsession.messaging.opengroups.OpenGroupAPI
+import org.session.libsession.messaging.opengroups.OpenGroupMessage
+import org.session.libsession.messaging.utilities.MessageWrapper
+import org.session.libsession.snode.RawResponsePromise
+import org.session.libsession.snode.SnodeAPI
+import org.session.libsession.snode.SnodeMessage
+
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.loki.api.crypto.ProofOfWork
+
 
 object MessageSender {
+
+    // Error
+    internal sealed class Error(val description: String) : Exception() {
+        object InvalidMessage : Error("Invalid message.")
+        object ProtoConversionFailed : Error("Couldn't convert message to proto.")
+        object ProofOfWorkCalculationFailed : Error("Proof of work calculation failed.")
+        object NoUserPublicKey : Error("Couldn't find user key pair.")
+
+        // Closed groups
+        object NoThread : Error("Couldn't find a thread associated with the given group public key.")
+        object NoPrivateKey : Error("Couldn't find a private key associated with the given group public key.")
+        object InvalidClosedGroupUpdate : Error("Invalid group update.")
+
+        internal val isRetryable: Boolean = when (this) {
+            is InvalidMessage -> false
+            is ProtoConversionFailed -> false
+            is ProofOfWorkCalculationFailed -> false
+            is InvalidClosedGroupUpdate -> false
+            else -> true
+        }
+    }
+
+    // Convenience
+    fun send(message: Message, destination: Destination): Promise<Unit, Exception> {
+        if (destination is Destination.OpenGroup) {
+            return sendToOpenGroupDestination(destination, message)
+        }
+        return sendToSnodeDestination(destination, message)
+    }
+
+    // One-on-One Chats & Closed Groups
+    fun sendToSnodeDestination(destination: Destination, message: Message): Promise<Unit, Exception> {
+        val deferred = deferred<Unit, Exception>()
+        val promise = deferred.promise
+        val storage = Configuration.shared.storage
+        val preconditionFailure = Exception("Destination should not be open groups!")
+        var snodeMessage: SnodeMessage? = null
+        message.sentTimestamp ?: run { message.sentTimestamp = System.currentTimeMillis() } /* Visible messages will already have their sent timestamp set */
+        message.sender = storage.getUserPublicKey()
+        try {
+            when (destination) {
+                is Destination.Contact -> message.recipient = destination.publicKey
+                is Destination.ClosedGroup -> message.recipient = destination.groupPublicKey
+                is Destination.OpenGroup -> throw preconditionFailure
+            }
+            // Validate the message
+            if (!message.isValid()) { throw Error.InvalidMessage }
+            // Convert it to protobuf
+            val proto = message.toProto() ?: throw Error.ProtoConversionFailed
+            // Serialize the protobuf
+            val plaintext = proto.toByteArray()
+            // Encrypt the serialized protobuf
+            val ciphertext: ByteArray
+            when (destination) {
+                is Destination.Contact -> ciphertext = MessageSenderEncryption.encryptWithSignalProtocol(plaintext, message, destination.publicKey)
+                is Destination.ClosedGroup -> ciphertext = MessageSenderEncryption.encryptWithSharedSenderKeys(plaintext, destination.groupPublicKey)
+                is Destination.OpenGroup -> throw preconditionFailure
+            }
+            // Wrap the result
+            val kind: SignalServiceProtos.Envelope.Type
+            val senderPublicKey: String
+            when (destination) {
+                is Destination.Contact -> {
+                    kind = SignalServiceProtos.Envelope.Type.UNIDENTIFIED_SENDER
+                    senderPublicKey = ""
+                }
+                is Destination.ClosedGroup -> {
+                    kind = SignalServiceProtos.Envelope.Type.CLOSED_GROUP_CIPHERTEXT
+                    senderPublicKey = destination.groupPublicKey
+                }
+                is Destination.OpenGroup -> throw preconditionFailure
+            }
+            val wrappedMessage = MessageWrapper.wrap(kind, message.sentTimestamp!!, senderPublicKey, ciphertext)
+            // Calculate proof of work
+            val recipient = message.recipient!!
+            val base64EncodedData = Base64.encodeBytes(wrappedMessage)
+            val timestamp = System.currentTimeMillis()
+            val nonce = ProofOfWork.calculate(base64EncodedData, recipient, timestamp, message.ttl.toInt()) ?: throw Error.ProofOfWorkCalculationFailed
+            // Send the result
+            snodeMessage = SnodeMessage(recipient, base64EncodedData, message.ttl, timestamp, nonce)
+            SnodeAPI.sendMessage(snodeMessage).success { promises: Set<RawResponsePromise> ->
+                var isSuccess = false
+                val promiseCount = promises.size
+                var errorCount = 0
+                promises.forEach { promise: RawResponsePromise ->
+                    promise.success {
+                        if (isSuccess) { return@success } // Succeed as soon as the first promise succeeds
+                        isSuccess = true
+                        deferred.resolve(Unit)
+                    }
+                    promise.fail {
+                        errorCount += 1
+                        if (errorCount != promiseCount) { return@fail } // Only error out if all promises failed
+                        deferred.reject(it)
+                    }
+                }
+            }.fail {
+                Log.d("Loki", "Couldn't send message due to error: $it.")
+                deferred.reject(it)
+            }
+        } catch (exception: Exception) {
+            deferred.reject(exception)
+        }
+        // Handle completion
+        promise.success {
+            handleSuccessfulMessageSend(message)
+            if (message is VisibleMessage && snodeMessage != null) {
+                val notifyPNServerJob = NotifyPNServerJob(snodeMessage)
+                JobQueue.shared.add(notifyPNServerJob)
+            }
+        }
+        promise.fail {
+            handleFailedMessageSend(message, it)
+        }
+
+        return promise
+    }
+
+    // Open Groups
+    fun sendToOpenGroupDestination(destination: Destination, message: Message): Promise<Unit, Exception> {
+        val deferred = deferred<Unit, Exception>()
+        val promise = deferred.promise
+        val storage = Configuration.shared.storage
+        val preconditionFailure = Exception("Destination should not be contacts or closed groups!")
+        message.sentTimestamp = System.currentTimeMillis()
+        message.sender = storage.getUserPublicKey()
+        try {
+            val server: String
+            val channel: Long
+            when (destination) {
+                is Destination.Contact -> throw preconditionFailure
+                is Destination.ClosedGroup -> throw preconditionFailure
+                is Destination.OpenGroup -> {
+                    message.recipient = "${destination.server}.${destination.channel}"
+                    server = destination.server
+                    channel = destination.channel
+                }
+            }
+            // Validate the message
+            if (message !is VisibleMessage || !message.isValid()) {
+                throw Error.InvalidMessage
+            }
+            // Convert the message to an open group message
+            val openGroupMessage = OpenGroupMessage.from(message, server) ?: throw Error.InvalidMessage
+            // Send the result
+            OpenGroupAPI.sendMessage(openGroupMessage, channel, server).success {
+                message.openGroupServerMessageID = it.serverID
+                deferred.resolve(Unit)
+            }.fail {
+                deferred.reject(it)
+            }
+        } catch (exception: Exception) {
+            deferred.reject(exception)
+        }
+        // Handle completion
+        promise.success {
+            handleSuccessfulMessageSend(message)
+        }
+        promise.fail {
+            handleFailedMessageSend(message, it)
+        }
+        return deferred.promise
+    }
+
+    // Result Handling
+    fun handleSuccessfulMessageSend(message: Message) {
+
+    }
+
+    fun handleFailedMessageSend(message: Message, error: Exception) {
+
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageSenderDelegate.kt

@@ -1,4 +1,4 @@
-package org.session.messaging.sending_receiving
+package org.session.libsession.messaging.sending_receiving
 
 interface MessageSenderDelegate {
 }

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/MessageSenderEncryption.kt

@@ -1,4 +1,52 @@
-package org.session.messaging.sending_receiving
+package org.session.libsession.messaging.sending_receiving
+
+import com.google.protobuf.ByteString
+import org.session.libsession.messaging.Configuration
+import org.session.libsession.messaging.messages.Message
+import org.session.libsession.messaging.sending_receiving.MessageSender.Error
+import org.session.libsession.messaging.utilities.UnidentifiedAccessUtil
+import org.session.libsession.utilities.AESGCM
+
+import org.session.libsignal.libsignal.SignalProtocolAddress
+import org.session.libsignal.libsignal.loki.ClosedGroupCiphertextMessage
+import org.session.libsignal.libsignal.util.Hex
+import org.session.libsignal.libsignal.util.guava.Optional
+import org.session.libsignal.service.api.crypto.SignalServiceCipher
+import org.session.libsignal.service.api.push.SignalServiceAddress
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.loki.protocol.closedgroups.SharedSenderKeysImplementation
+import org.session.libsignal.service.loki.utilities.removing05PrefixIfNeeded
 
 object MessageSenderEncryption {
+
+    internal fun encryptWithSignalProtocol(plaintext: ByteArray, message: Message, recipientPublicKey: String): ByteArray{
+        val storage = Configuration.shared.signalStorage
+        val sskDatabase = Configuration.shared.sskDatabase
+        val sessionResetImp = Configuration.shared.sessionResetImp
+        val localAddress = SignalServiceAddress(recipientPublicKey)
+        val certificateValidator = Configuration.shared.certificateValidator
+        val cipher = SignalServiceCipher(localAddress, storage, sskDatabase, sessionResetImp, certificateValidator)
+        val signalProtocolAddress = SignalProtocolAddress(recipientPublicKey, 1)
+        val unidentifiedAccessPair = UnidentifiedAccessUtil.getAccessFor(recipientPublicKey)
+        val unidentifiedAccess = if (unidentifiedAccessPair != null) unidentifiedAccessPair.targetUnidentifiedAccess else Optional.absent()
+        val encryptedMessage = cipher.encrypt(signalProtocolAddress, unidentifiedAccess, plaintext)
+        return Base64.decode(encryptedMessage.content)
+    }
+
+    internal fun encryptWithSharedSenderKeys(plaintext: ByteArray, groupPublicKey: String): ByteArray {
+        // 1. ) Encrypt the data with the user's sender key
+        val userPublicKey = Configuration.shared.storage.getUserPublicKey() ?: throw Error.NoUserPublicKey
+        val ciphertextAndKeyIndex = SharedSenderKeysImplementation.shared.encrypt(plaintext, groupPublicKey, userPublicKey)
+        val ivAndCiphertext = ciphertextAndKeyIndex.first
+        val keyIndex = ciphertextAndKeyIndex.second
+        val encryptedMessage = ClosedGroupCiphertextMessage(ivAndCiphertext, Hex.fromStringCondensed(userPublicKey), keyIndex);
+        // 2. ) Encrypt the result for the group's public key to hide the sender public key and key index
+        val intermediate = AESGCM.encrypt(encryptedMessage.serialize(), groupPublicKey.removing05PrefixIfNeeded())
+        // 3. ) Wrap the result
+        return SignalServiceProtos.ClosedGroupCiphertextMessageWrapper.newBuilder()
+                .setCiphertext(ByteString.copyFrom(intermediate.ciphertext))
+                .setEphemeralPublicKey(ByteString.copyFrom(intermediate.ephemeralPublicKey))
+                .build().toByteArray()
+    }
 }

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/Notification.kt

@@ -1,2 +0,0 @@
-package org.session.messaging.sending_receiving
-

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/notifications/Notification.kt

@@ -0,0 +1,2 @@
+package org.session.libsession.messaging.sending_receiving.notifications
+

libsession/src/main/java/org/session/libsession/messaging/sending_receiving/notifications/PushNotificationAPI.kt

@@ -0,0 +1,101 @@
+package org.session.libsession.messaging.sending_receiving.notifications
+
+import android.content.Context
+import nl.komponents.kovenant.functional.map
+import okhttp3.*
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsignal.service.loki.api.onionrequests.OnionRequestAPI
+import org.session.libsignal.service.loki.utilities.retryIfNeeded
+import java.io.IOException
+
+object PushNotificationAPI {
+    val server = "https://live.apns.getsession.org"
+    val serverPublicKey = "642a6585919742e5a2d4dc51244964fbcd8bcab2b75612407de58b810740d049"
+    private val maxRetryCount = 4
+    private val tokenExpirationInterval = 12 * 60 * 60 * 1000
+
+    enum class ClosedGroupOperation {
+        Subscribe, Unsubscribe;
+
+        val rawValue: String
+            get() {
+                return when (this) {
+                    Subscribe -> "subscribe_closed_group"
+                    Unsubscribe -> "unsubscribe_closed_group"
+                }
+            }
+    }
+
+    fun unregister(token: String, context: Context) {
+        val parameters = mapOf( "token" to token )
+        val url = "$server/unregister"
+        val body = RequestBody.create(MediaType.get("application/json"), JsonUtil.toJson(parameters))
+        val request = Request.Builder().url(url).post(body)
+        retryIfNeeded(maxRetryCount) {
+            OnionRequestAPI.sendOnionRequest(request.build(), server, serverPublicKey, "/loki/v2/lsrpc").map { json ->
+                val code = json["code"] as? Int
+                if (code != null && code != 0) {
+                    TextSecurePreferences.setIsUsingFCM(context, false)
+                } else {
+                    Log.d("Loki", "Couldn't disable FCM due to error: ${json["message"] as? String ?: "null"}.")
+                }
+            }.fail { exception ->
+                Log.d("Loki", "Couldn't disable FCM due to error: ${exception}.")
+            }
+        }
+        // Unsubscribe from all closed groups
+        val allClosedGroupPublicKeys = DatabaseFactory.getSSKDatabase(context).getAllClosedGroupPublicKeys()
+        val userPublicKey = TextSecurePreferences.getLocalNumber(context)
+        allClosedGroupPublicKeys.forEach { closedGroup ->
+            performOperation(context, ClosedGroupOperation.Unsubscribe, closedGroup, userPublicKey)
+        }
+    }
+
+    fun register(token: String, publicKey: String, context: Context, force: Boolean) {
+        val oldToken = TextSecurePreferences.getFCMToken(context)
+        val lastUploadDate = TextSecurePreferences.getLastFCMUploadTime(context)
+        if (!force && token == oldToken && System.currentTimeMillis() - lastUploadDate < tokenExpirationInterval) { return }
+        val parameters = mapOf( "token" to token, "pubKey" to publicKey )
+        val url = "$server/register"
+        val body = RequestBody.create(MediaType.get("application/json"), JsonUtil.toJson(parameters))
+        val request = Request.Builder().url(url).post(body)
+        retryIfNeeded(maxRetryCount) {
+            OnionRequestAPI.sendOnionRequest(request.build(), server, serverPublicKey, "/loki/v2/lsrpc").map { json ->
+                val code = json["code"] as? Int
+                if (code != null && code != 0) {
+                    TextSecurePreferences.setIsUsingFCM(context, true)
+                    TextSecurePreferences.setFCMToken(context, token)
+                    TextSecurePreferences.setLastFCMUploadTime(context, System.currentTimeMillis())
+                } else {
+                    Log.d("Loki", "Couldn't register for FCM due to error: ${json["message"] as? String ?: "null"}.")
+                }
+            }.fail { exception ->
+                Log.d("Loki", "Couldn't register for FCM due to error: ${exception}.")
+            }
+        }
+        // Subscribe to all closed groups
+        val allClosedGroupPublicKeys = DatabaseFactory.getSSKDatabase(context).getAllClosedGroupPublicKeys()
+        allClosedGroupPublicKeys.forEach { closedGroup ->
+            performOperation(context, ClosedGroupOperation.Subscribe, closedGroup, publicKey)
+        }
+    }
+
+    fun performOperation(context: Context, operation: ClosedGroupOperation, closedGroupPublicKey: String, publicKey: String) {
+        if (!TextSecurePreferences.isUsingFCM(context)) { return }
+        val parameters = mapOf( "closedGroupPublicKey" to closedGroupPublicKey, "pubKey" to publicKey )
+        val url = "$server/${operation.rawValue}"
+        val body = RequestBody.create(MediaType.get("application/json"), JsonUtil.toJson(parameters))
+        val request = Request.Builder().url(url).post(body)
+        retryIfNeeded(maxRetryCount) {
+            OnionRequestAPI.sendOnionRequest(request.build(), server, serverPublicKey, "/loki/v2/lsrpc").map { json ->
+                val code = json["code"] as? Int
+                if (code == null || code == 0) {
+                    Log.d("Loki", "Couldn't subscribe/unsubscribe closed group: $closedGroupPublicKey due to error: ${json["message"] as? String ?: "null"}.")
+                }
+            }.fail { exception ->
+                Log.d("Loki", "Couldn't subscribe/unsubscribe closed group: $closedGroupPublicKey due to error: ${exception}.")
+            }
+        }
+    }
+}

libsession/src/main/java/org/session/libsession/messaging/utilities/DotNetAPI.kt

@@ -0,0 +1,268 @@
+package org.session.libsession.messaging.utilities
+
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.functional.bind
+import nl.komponents.kovenant.functional.map
+import nl.komponents.kovenant.then
+import okhttp3.MediaType
+import okhttp3.MultipartBody
+import okhttp3.Request
+import okhttp3.RequestBody
+
+import org.session.libsession.messaging.Configuration
+import org.session.libsession.snode.OnionRequestAPI
+import org.session.libsession.snode.SnodeAPI
+import org.session.libsession.messaging.fileserver.FileServerAPI
+
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.libsignal.loki.DiffieHellman
+import org.session.libsignal.service.api.crypto.ProfileCipherOutputStream
+import org.session.libsignal.service.api.push.exceptions.NonSuccessfulResponseCodeException
+import org.session.libsignal.service.api.push.exceptions.PushNetworkException
+import org.session.libsignal.service.api.util.StreamDetails
+import org.session.libsignal.service.internal.push.ProfileAvatarData
+import org.session.libsignal.service.internal.push.PushAttachmentData
+import org.session.libsignal.service.internal.push.http.DigestingRequestBody
+import org.session.libsignal.service.internal.push.http.ProfileCipherOutputStreamFactory
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.internal.util.Hex
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsignal.service.loki.api.utilities.HTTP
+import org.session.libsignal.service.loki.utilities.*
+import java.util.*
+
+/**
+ * Base class that provides utilities for .NET based APIs.
+ */
+open class DotNetAPI {
+
+    internal enum class HTTPVerb { GET, PUT, POST, DELETE, PATCH }
+
+    // Error
+    internal sealed class Error(val description: String) : Exception() {
+        object Generic : Error("An error occurred.")
+        object InvalidURL : Error("Invalid URL.")
+        object ParsingFailed : Error("Invalid file server response.")
+        object SigningFailed : Error("Couldn't sign message.")
+        object EncryptionFailed : Error("Couldn't encrypt file.")
+        object DecryptionFailed : Error("Couldn't decrypt file.")
+        object MaxFileSizeExceeded : Error("Maximum file size exceeded.")
+        object TokenExpired: Error("Token expired.") // Session Android
+    }
+
+    companion object {
+        private val authTokenRequestCache = hashMapOf<String, Promise<String, Exception>>()
+    }
+
+    public data class UploadResult(val id: Long, val url: String, val digest: ByteArray?)
+
+    public fun getAuthToken(server: String): Promise<String, Exception> {
+        val storage = Configuration.shared.storage
+        val token = storage.getAuthToken(server)
+        if (token != null) { return Promise.of(token) }
+        // Avoid multiple token requests to the server by caching
+        var promise = authTokenRequestCache[server]
+        if (promise == null) {
+            promise = requestNewAuthToken(server).bind { submitAuthToken(it, server) }.then { newToken ->
+                storage.setAuthToken(server, newToken)
+                newToken
+            }.always {
+                authTokenRequestCache.remove(server)
+            }
+            authTokenRequestCache[server] = promise
+        }
+        return promise
+    }
+
+    private fun requestNewAuthToken(server: String): Promise<String, Exception> {
+        Log.d("Loki", "Requesting auth token for server: $server.")
+        val userKeyPair = Configuration.shared.storage.getUserKeyPair() ?: throw Error.Generic
+        val parameters: Map<String, Any> = mapOf( "pubKey" to userKeyPair.hexEncodedPublicKey )
+        return execute(HTTPVerb.GET, server, "loki/v1/get_challenge", false, parameters).map(SnodeAPI.sharedContext) { json ->
+            try {
+                val base64EncodedChallenge = json["cipherText64"] as String
+                val challenge = Base64.decode(base64EncodedChallenge)
+                val base64EncodedServerPublicKey = json["serverPubKey64"] as String
+                var serverPublicKey = Base64.decode(base64EncodedServerPublicKey)
+                // Discard the "05" prefix if needed
+                if (serverPublicKey.count() == 33) {
+                    val hexEncodedServerPublicKey = Hex.toStringCondensed(serverPublicKey)
+                    serverPublicKey = Hex.fromStringCondensed(hexEncodedServerPublicKey.removing05PrefixIfNeeded())
+                }
+                // The challenge is prefixed by the 16 bit IV
+                val tokenAsData = DiffieHellman.decrypt(challenge, serverPublicKey, userKeyPair.privateKey.serialize())
+                val token = tokenAsData.toString(Charsets.UTF_8)
+                token
+            } catch (exception: Exception) {
+                Log.d("Loki", "Couldn't parse auth token for server: $server.")
+                throw exception
+            }
+        }
+    }
+
+    private fun submitAuthToken(token: String, server: String): Promise<String, Exception> {
+        Log.d("Loki", "Submitting auth token for server: $server.")
+        val userPublicKey = Configuration.shared.storage.getUserPublicKey() ?: throw Error.Generic
+        val parameters = mapOf( "pubKey" to userPublicKey, "token" to token )
+        return execute(HTTPVerb.POST, server, "loki/v1/submit_challenge", false, parameters, isJSONRequired = false).map { token }
+    }
+
+    internal fun execute(verb: HTTPVerb, server: String, endpoint: String, isAuthRequired: Boolean = true, parameters: Map<String, Any> = mapOf(), isJSONRequired: Boolean = true): Promise<Map<*, *>, Exception> {
+        fun execute(token: String?): Promise<Map<*, *>, Exception> {
+            val sanitizedEndpoint = endpoint.removePrefix("/")
+            var url = "$server/$sanitizedEndpoint"
+            if (verb == HTTPVerb.GET || verb == HTTPVerb.DELETE) {
+                val queryParameters = parameters.map { "${it.key}=${it.value}" }.joinToString("&")
+                if (queryParameters.isNotEmpty()) { url += "?$queryParameters" }
+            }
+            var request = Request.Builder().url(url)
+            if (isAuthRequired) {
+                if (token == null) { throw IllegalStateException() }
+                request = request.header("Authorization", "Bearer $token")
+            }
+            when (verb) {
+                HTTPVerb.GET -> request = request.get()
+                HTTPVerb.DELETE -> request = request.delete()
+                else -> {
+                    val parametersAsJSON = JsonUtil.toJson(parameters)
+                    val body = RequestBody.create(MediaType.get("application/json"), parametersAsJSON)
+                    when (verb) {
+                        HTTPVerb.PUT -> request = request.put(body)
+                        HTTPVerb.POST -> request = request.post(body)
+                        HTTPVerb.PATCH -> request = request.patch(body)
+                        else -> throw IllegalStateException()
+                    }
+                }
+            }
+            val serverPublicKeyPromise = if (server == FileServerAPI.shared.server) Promise.of(FileServerAPI.fileServerPublicKey)
+                else FileServerAPI.shared.getPublicKeyForOpenGroupServer(server)
+            return serverPublicKeyPromise.bind { serverPublicKey ->
+                OnionRequestAPI.sendOnionRequest(request.build(), server, serverPublicKey, isJSONRequired = isJSONRequired).recover { exception ->
+                    if (exception is HTTP.HTTPRequestFailedException) {
+                        val statusCode = exception.statusCode
+                        if (statusCode == 401 || statusCode == 403) {
+                            Configuration.shared.storage.setAuthToken(server, null)
+                            throw Error.TokenExpired
+                        }
+                    }
+                    throw exception
+                }
+            }
+        }
+        return if (isAuthRequired) {
+            getAuthToken(server).bind { execute(it) }
+        } else {
+            execute(null)
+        }
+    }
+
+    internal fun getUserProfiles(publicKeys: Set<String>, server: String, includeAnnotations: Boolean): Promise<List<Map<*, *>>, Exception> {
+        val parameters = mapOf( "include_user_annotations" to includeAnnotations.toInt(), "ids" to publicKeys.joinToString { "@$it" } )
+        return execute(HTTPVerb.GET, server, "users", parameters = parameters).map { json ->
+            val data = json["data"] as? List<Map<*, *>>
+            if (data == null) {
+                Log.d("Loki", "Couldn't parse user profiles for: $publicKeys from: $json.")
+                throw Error.ParsingFailed
+            }
+            data!! // For some reason the compiler can't infer that this can't be null at this point
+        }
+    }
+
+    internal fun setSelfAnnotation(server: String, type: String, newValue: Any?): Promise<Map<*, *>, Exception> {
+        val annotation = mutableMapOf<String, Any>( "type" to type )
+        if (newValue != null) { annotation["value"] = newValue }
+        val parameters = mapOf( "annotations" to listOf( annotation ) )
+        return execute(HTTPVerb.PATCH, server, "users/me", parameters = parameters)
+    }
+
+    @Throws(PushNetworkException::class, NonSuccessfulResponseCodeException::class)
+    fun uploadAttachment(server: String, attachment: PushAttachmentData): UploadResult {
+        // This function mimics what Signal does in PushServiceSocket
+        val contentType = "application/octet-stream"
+        val file = DigestingRequestBody(attachment.data, attachment.outputStreamFactory, contentType, attachment.dataSize, attachment.listener)
+        Log.d("Loki", "File size: ${attachment.dataSize} bytes.")
+        val body = MultipartBody.Builder()
+            .setType(MultipartBody.FORM)
+            .addFormDataPart("type", "network.loki")
+            .addFormDataPart("Content-Type", contentType)
+            .addFormDataPart("content", UUID.randomUUID().toString(), file)
+            .build()
+        val request = Request.Builder().url("$server/files").post(body)
+        return upload(server, request) { json -> // Retrying is handled by AttachmentUploadJob
+            val data = json["data"] as? Map<*, *>
+            if (data == null) {
+                Log.d("Loki", "Couldn't parse attachment from: $json.")
+                throw Error.ParsingFailed
+            }
+            val id = data["id"] as? Long ?: (data["id"] as? Int)?.toLong() ?: (data["id"] as? String)?.toLong()
+            val url = data["url"] as? String
+            if (id == null || url == null || url.isEmpty()) {
+                Log.d("Loki", "Couldn't parse upload from: $json.")
+                throw Error.ParsingFailed
+            }
+            UploadResult(id, url, file.transmittedDigest)
+        }.get()
+    }
+
+    @Throws(PushNetworkException::class, NonSuccessfulResponseCodeException::class)
+    fun uploadProfilePicture(server: String, key: ByteArray, profilePicture: StreamDetails, setLastProfilePictureUpload: () -> Unit): UploadResult {
+        val profilePictureUploadData = ProfileAvatarData(profilePicture.stream, ProfileCipherOutputStream.getCiphertextLength(profilePicture.length), profilePicture.contentType, ProfileCipherOutputStreamFactory(key))
+        val file = DigestingRequestBody(profilePictureUploadData.data, profilePictureUploadData.outputStreamFactory,
+            profilePictureUploadData.contentType, profilePictureUploadData.dataLength, null)
+        val body = MultipartBody.Builder()
+            .setType(MultipartBody.FORM)
+            .addFormDataPart("type", "network.loki")
+            .addFormDataPart("Content-Type", "application/octet-stream")
+            .addFormDataPart("content", UUID.randomUUID().toString(), file)
+            .build()
+        val request = Request.Builder().url("$server/files").post(body)
+        return retryIfNeeded(4) {
+            upload(server, request) { json ->
+                val data = json["data"] as? Map<*, *>
+                if (data == null) {
+                    Log.d("Loki", "Couldn't parse profile picture from: $json.")
+                    throw Error.ParsingFailed
+                }
+                val id = data["id"] as? Long ?: (data["id"] as? Int)?.toLong() ?: (data["id"] as? String)?.toLong()
+                val url = data["url"] as? String
+                if (id == null || url == null || url.isEmpty()) {
+                    Log.d("Loki", "Couldn't parse profile picture from: $json.")
+                    throw Error.ParsingFailed
+                }
+                setLastProfilePictureUpload()
+                UploadResult(id, url, file.transmittedDigest)
+            }
+        }.get()
+    }
+
+    @Throws(PushNetworkException::class, NonSuccessfulResponseCodeException::class)
+    private fun upload(server: String, request: Request.Builder, parse: (Map<*, *>) -> UploadResult): Promise<UploadResult, Exception> {
+        val promise: Promise<Map<*, *>, Exception>
+        if (server == FileServerAPI.shared.server) {
+            request.addHeader("Authorization", "Bearer loki")
+            // Uploads to the Loki File Server shouldn't include any personally identifiable information, so use a dummy auth token
+            promise = OnionRequestAPI.sendOnionRequest(request.build(), FileServerAPI.shared.server, FileServerAPI.fileServerPublicKey)
+        } else {
+            promise = FileServerAPI.shared.getPublicKeyForOpenGroupServer(server).bind { openGroupServerPublicKey ->
+                getAuthToken(server).bind { token ->
+                    request.addHeader("Authorization", "Bearer $token")
+                    OnionRequestAPI.sendOnionRequest(request.build(), server, openGroupServerPublicKey)
+                }
+            }
+        }
+        return promise.map { json ->
+            parse(json)
+        }.recover { exception ->
+            if (exception is HTTP.HTTPRequestFailedException) {
+                val statusCode = exception.statusCode
+                if (statusCode == 401 || statusCode == 403) {
+                    Configuration.shared.storage.setAuthToken(server, null)
+                }
+                throw NonSuccessfulResponseCodeException("Request returned with status code ${exception.statusCode}.")
+            }
+            throw PushNetworkException(exception)
+        }
+    }
+}
+
+private fun Boolean.toInt(): Int { return if (this) 1 else 0 }

libsession/src/main/java/org/session/libsession/messaging/utilities/MessageWrapper.kt

@@ -0,0 +1,85 @@
+package org.session.libsession.messaging.utilities
+
+import com.google.protobuf.ByteString
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import org.session.libsignal.service.internal.push.SignalServiceProtos.Envelope
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.internal.websocket.WebSocketProtos.WebSocketMessage
+import org.session.libsignal.service.internal.websocket.WebSocketProtos.WebSocketRequestMessage
+import java.security.SecureRandom
+
+object MessageWrapper {
+
+    // region Types
+    sealed class Error(val description: String) : Exception() {
+        object FailedToWrapData : Error("Failed to wrap data.")
+        object FailedToWrapMessageInEnvelope : Error("Failed to wrap message in envelope.")
+        object FailedToWrapEnvelopeInWebSocketMessage : Error("Failed to wrap envelope in web socket message.")
+        object FailedToUnwrapData : Error("Failed to unwrap data.")
+    }
+    // endregion
+
+    // region Wrapping
+    /**
+     * Wraps `message` in a `SignalServiceProtos.Envelope` and then a `WebSocketProtos.WebSocketMessage` to match the desktop application.
+     */
+    fun wrap(type: Envelope.Type, timestamp: Long, senderPublicKey: String, content: ByteArray): ByteArray {
+        try {
+            val envelope = createEnvelope(type, timestamp, senderPublicKey, content)
+            val webSocketMessage = createWebSocketMessage(envelope)
+            return webSocketMessage.toByteArray()
+        } catch (e: Exception) {
+            throw if (e is Error) { e } else { Error.FailedToWrapData }
+        }
+    }
+
+    private fun createEnvelope(type: Envelope.Type, timestamp: Long, senderPublicKey: String, content: ByteArray): Envelope {
+        try {
+            val builder = Envelope.newBuilder()
+            builder.type = type
+            builder.timestamp = timestamp
+            builder.source = senderPublicKey
+            builder.sourceDevice = 1
+            builder.content = ByteString.copyFrom(content)
+            return builder.build()
+        } catch (e: Exception) {
+            Log.d("Loki", "Failed to wrap message in envelope: ${e.message}.")
+            throw Error.FailedToWrapMessageInEnvelope
+        }
+    }
+
+    private fun createWebSocketMessage(envelope: Envelope): WebSocketMessage {
+        try {
+            val requestBuilder = WebSocketRequestMessage.newBuilder()
+            requestBuilder.verb = "PUT"
+            requestBuilder.path = "/api/v1/message"
+            requestBuilder.id = SecureRandom.getInstance("SHA1PRNG").nextLong()
+            requestBuilder.body = envelope.toByteString()
+            val messageBuilder = WebSocketMessage.newBuilder()
+            messageBuilder.request = requestBuilder.build()
+            messageBuilder.type = WebSocketMessage.Type.REQUEST
+            return messageBuilder.build()
+        } catch (e: Exception) {
+            Log.d("Loki", "Failed to wrap envelope in web socket message: ${e.message}.")
+            throw Error.FailedToWrapEnvelopeInWebSocketMessage
+        }
+    }
+    // endregion
+
+    // region Unwrapping
+    /**
+     * `data` shouldn't be base 64 encoded.
+     */
+    fun unwrap(data: ByteArray): Envelope {
+        try {
+            val webSocketMessage = WebSocketMessage.parseFrom(data)
+            val envelopeAsData = webSocketMessage.request.body
+            return Envelope.parseFrom(envelopeAsData)
+        } catch (e: Exception) {
+            Log.d("Loki", "Failed to unwrap data: ${e.message}.")
+            throw Error.FailedToUnwrapData
+        }
+    }
+    // endregion
+}

libsession/src/main/java/org/session/libsession/messaging/utilities/UnidentifiedAccessUtil.kt

@@ -0,0 +1,60 @@
+package org.session.libsession.messaging.utilities
+
+import com.goterl.lazycode.lazysodium.LazySodiumAndroid
+import com.goterl.lazycode.lazysodium.SodiumAndroid
+
+import org.session.libsession.messaging.Configuration
+
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.metadata.SignalProtos
+import org.session.libsignal.metadata.certificate.InvalidCertificateException
+import org.session.libsignal.service.api.crypto.UnidentifiedAccess
+import org.session.libsignal.service.api.crypto.UnidentifiedAccessPair
+
+object UnidentifiedAccessUtil {
+    private val TAG = UnidentifiedAccessUtil::class.simpleName
+    private val sodium = LazySodiumAndroid(SodiumAndroid())
+
+    fun getAccessFor(recipientPublicKey: String): UnidentifiedAccessPair? {
+        try {
+            val theirUnidentifiedAccessKey = getTargetUnidentifiedAccessKey(recipientPublicKey)
+            val ourUnidentifiedAccessKey = getSelfUnidentifiedAccessKey()
+            val ourUnidentifiedAccessCertificate = getUnidentifiedAccessCertificate()
+
+            Log.i(TAG, "Their access key present? " + (theirUnidentifiedAccessKey != null) +
+                    " | Our access key present? " + (ourUnidentifiedAccessKey != null) +
+                    " | Our certificate present? " + (ourUnidentifiedAccessCertificate != null))
+
+            if (theirUnidentifiedAccessKey != null && ourUnidentifiedAccessKey != null && ourUnidentifiedAccessCertificate != null) {
+                return UnidentifiedAccessPair(UnidentifiedAccess(theirUnidentifiedAccessKey, ourUnidentifiedAccessCertificate),
+                        UnidentifiedAccess(ourUnidentifiedAccessKey, ourUnidentifiedAccessCertificate))
+            }
+            return null
+        } catch (e: InvalidCertificateException) {
+            Log.w(TAG, e)
+            return null
+        }
+    }
+
+    private fun getTargetUnidentifiedAccessKey(recipientPublicKey: String): ByteArray? {
+        val theirProfileKey = Configuration.shared.storage.getProfileKeyForRecipient(recipientPublicKey) ?: return sodium.randomBytesBuf(16)
+        return UnidentifiedAccess.deriveAccessKeyFrom(theirProfileKey)
+    }
+
+    private fun getSelfUnidentifiedAccessKey(): ByteArray? {
+        val userPublicKey = Configuration.shared.storage.getUserPublicKey()
+        if (userPublicKey != null) {
+            return sodium.randomBytesBuf(16)
+        }
+        return null
+    }
+
+    private fun getUnidentifiedAccessCertificate(): ByteArray? {
+        val userPublicKey = Configuration.shared.storage.getUserPublicKey()
+        if (userPublicKey != null) {
+            val certificate = SignalProtos.SenderCertificate.newBuilder().setSender(userPublicKey).setSenderDevice(1).build()
+            return certificate.toByteArray()
+        }
+        return null
+    }
+}

libsession/src/main/java/org/session/libsession/snode/Configuration.kt

@@ -0,0 +1,14 @@
+package org.session.libsession.snode
+
+import org.session.libsignal.service.loki.utilities.Broadcaster
+
+class Configuration(val storage: SnodeStorageProtocol, val broadcaster: Broadcaster) {
+    companion object {
+        lateinit var shared: Configuration
+
+        fun configure(storage: SnodeStorageProtocol, broadcaster: Broadcaster) {
+            if (Companion::shared.isInitialized) { return }
+            shared = Configuration(storage, broadcaster)
+        }
+    }
+}

libsession/src/main/java/org/session/libsession/snode/OnionRequestAPI.kt

@@ -0,0 +1,464 @@
+package org.session.libsession.snode
+
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.all
+import nl.komponents.kovenant.deferred
+import nl.komponents.kovenant.functional.bind
+import nl.komponents.kovenant.functional.map
+import okhttp3.Request
+import org.session.libsession.utilities.AESGCM
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsignal.service.loki.api.*
+import org.session.libsignal.service.loki.api.fileserver.FileServerAPI
+import org.session.libsignal.service.loki.api.utilities.*
+import org.session.libsession.utilities.AESGCM.EncryptionResult
+import org.session.libsession.utilities.getBodyForOnionRequest
+import org.session.libsession.utilities.getHeadersForOnionRequest
+import org.session.libsignal.service.loki.utilities.*
+
+private typealias Path = List<Snode>
+
+/**
+ * See the "Onion Requests" section of [The Session Whitepaper](https://arxiv.org/pdf/2002.04609.pdf) for more information.
+ */
+public object OnionRequestAPI {
+    private val pathFailureCount = mutableMapOf<Path, Int>()
+    private val snodeFailureCount = mutableMapOf<Snode, Int>()
+    public var guardSnodes = setOf<Snode>()
+    public var paths: List<Path> // Not a set to ensure we consistently show the same path to the user
+        get() = SnodeAPI.database.getOnionRequestPaths()
+        set(newValue) {
+            if (newValue.isEmpty()) {
+                SnodeAPI.database.clearOnionRequestPaths()
+            } else {
+                SnodeAPI.database.setOnionRequestPaths(newValue)
+            }
+        }
+
+    // region Settings
+    /**
+     * The number of snodes (including the guard snode) in a path.
+     */
+    private val pathSize = 3
+    /**
+     * The number of times a path can fail before it's replaced.
+     */
+    private val pathFailureThreshold = 2
+    /**
+     * The number of times a snode can fail before it's replaced.
+     */
+    private val snodeFailureThreshold = 2
+    /**
+     * The number of paths to maintain.
+     */
+    public val targetPathCount = 2 // A main path and a backup path for the case where the target snode is in the main path
+
+    /**
+     * The number of guard snodes required to maintain `targetPathCount` paths.
+     */
+    private val targetGuardSnodeCount
+        get() = targetPathCount // One per path
+    // endregion
+
+    class HTTPRequestFailedAtDestinationException(val statusCode: Int, val json: Map<*, *>)
+        : Exception("HTTP request failed at destination with status code $statusCode.")
+    class InsufficientSnodesException : Exception("Couldn't find enough snodes to build a path.")
+
+    private data class OnionBuildingResult(
+        internal val guardSnode: Snode,
+        internal val finalEncryptionResult: EncryptionResult,
+        internal val destinationSymmetricKey: ByteArray
+    )
+
+    internal sealed class Destination {
+        class Snode(val snode: org.session.libsession.snode.Snode) : Destination()
+        class Server(val host: String, val target: String, val x25519PublicKey: String) : Destination()
+    }
+
+    // region Private API
+    /**
+     * Tests the given snode. The returned promise errors out if the snode is faulty; the promise is fulfilled otherwise.
+     */
+    private fun testSnode(snode: Snode): Promise<Unit, Exception> {
+        val deferred = deferred<Unit, Exception>()
+        Thread { // No need to block the shared context for this
+            val url = "${snode.address}:${snode.port}/get_stats/v1"
+            try {
+                val json = HTTP.execute(HTTP.Verb.GET, url)
+                val version = json["version"] as? String
+                if (version == null) { deferred.reject(Exception("Missing snode version.")); return@Thread }
+                if (version >= "2.0.7") {
+                    deferred.resolve(Unit)
+                } else {
+                    val message = "Unsupported snode version: $version."
+                    Log.d("Loki", message)
+                    deferred.reject(Exception(message))
+                }
+            } catch (exception: Exception) {
+                deferred.reject(exception)
+            }
+        }.start()
+        return deferred.promise
+    }
+
+    /**
+     * Finds `targetGuardSnodeCount` guard snodes to use for path building. The returned promise errors out if not
+     * enough (reliable) snodes are available.
+     */
+    private fun getGuardSnodes(reusableGuardSnodes: List<Snode>): Promise<Set<Snode>, Exception> {
+        if (guardSnodes.count() >= targetGuardSnodeCount) {
+            return Promise.of(guardSnodes)
+        } else {
+            Log.d("Loki", "Populating guard snode cache.")
+            return SnodeAPI.getRandomSnode().bind(SnodeAPI.sharedContext) { // Just used to populate the snode pool
+                var unusedSnodes = SnodeAPI.snodePool.minus(reusableGuardSnodes)
+                val reusableGuardSnodeCount = reusableGuardSnodes.count()
+                if (unusedSnodes.count() < (targetGuardSnodeCount - reusableGuardSnodeCount)) { throw InsufficientSnodesException() }
+                fun getGuardSnode(): Promise<Snode, Exception> {
+                    val candidate = unusedSnodes.getRandomElementOrNull()
+                        ?: return Promise.ofFail(InsufficientSnodesException())
+                    unusedSnodes = unusedSnodes.minus(candidate)
+                    Log.d("Loki", "Testing guard snode: $candidate.")
+                    // Loop until a reliable guard snode is found
+                    val deferred = deferred<Snode, Exception>()
+                    testSnode(candidate).success {
+                        deferred.resolve(candidate)
+                    }.fail {
+                        getGuardSnode().success {
+                            deferred.resolve(candidate)
+                        }.fail { exception ->
+                            if (exception is InsufficientSnodesException) {
+                                deferred.reject(exception)
+                            }
+                        }
+                    }
+                    return deferred.promise
+                }
+                val promises = (0 until (targetGuardSnodeCount - reusableGuardSnodeCount)).map { getGuardSnode() }
+                all(promises).map(SnodeAPI.sharedContext) { guardSnodes ->
+                    val guardSnodesAsSet = (guardSnodes + reusableGuardSnodes).toSet()
+                    OnionRequestAPI.guardSnodes = guardSnodesAsSet
+                    guardSnodesAsSet
+                }
+            }
+        }
+    }
+
+    /**
+     * Builds and returns `targetPathCount` paths. The returned promise errors out if not
+     * enough (reliable) snodes are available.
+     */
+    private fun buildPaths(reusablePaths: List<Path>): Promise<List<Path>, Exception> {
+        Log.d("Loki", "Building onion request paths.")
+        SnodeAPI.broadcaster.broadcast("buildingPaths")
+        return SnodeAPI.getRandomSnode().bind(SnodeAPI.sharedContext) { // Just used to populate the snode pool
+            val reusableGuardSnodes = reusablePaths.map { it[0] }
+            getGuardSnodes(reusableGuardSnodes).map(SnodeAPI.sharedContext) { guardSnodes ->
+                var unusedSnodes = SnodeAPI.snodePool.minus(guardSnodes).minus(reusablePaths.flatten())
+                val reusableGuardSnodeCount = reusableGuardSnodes.count()
+                val pathSnodeCount = (targetGuardSnodeCount - reusableGuardSnodeCount) * pathSize - (targetGuardSnodeCount - reusableGuardSnodeCount)
+                if (unusedSnodes.count() < pathSnodeCount) { throw InsufficientSnodesException() }
+                // Don't test path snodes as this would reveal the user's IP to them
+                guardSnodes.minus(reusableGuardSnodes).map { guardSnode ->
+                    val result = listOf( guardSnode ) + (0 until (pathSize - 1)).map {
+                        val pathSnode = unusedSnodes.getRandomElement()
+                        unusedSnodes = unusedSnodes.minus(pathSnode)
+                        pathSnode
+                    }
+                    Log.d("Loki", "Built new onion request path: $result.")
+                    result
+                }
+            }.map { paths ->
+                OnionRequestAPI.paths = paths + reusablePaths
+                SnodeAPI.broadcaster.broadcast("pathsBuilt")
+                paths
+            }
+        }
+    }
+
+    /**
+     * Returns a `Path` to be used for building an onion request. Builds new paths as needed.
+     */
+    private fun getPath(snodeToExclude: Snode?): Promise<Path, Exception> {
+        if (pathSize < 1) { throw Exception("Can't build path of size zero.") }
+        val paths = this.paths
+        val guardSnodes = mutableSetOf<Snode>()
+        if (paths.isNotEmpty()) {
+            guardSnodes.add(paths[0][0])
+            if (paths.count() >= 2) {
+                guardSnodes.add(paths[1][0])
+            }
+        }
+        OnionRequestAPI.guardSnodes = guardSnodes
+        fun getPath(paths: List<Path>): Path {
+            if (snodeToExclude != null) {
+                return paths.filter { !it.contains(snodeToExclude) }.getRandomElement()
+            } else {
+                return paths.getRandomElement()
+            }
+        }
+        if (paths.count() >= targetPathCount) {
+            return Promise.of(getPath(paths))
+        } else if (paths.isNotEmpty()) {
+            if (paths.any { !it.contains(snodeToExclude) }) {
+                buildPaths(paths) // Re-build paths in the background
+                return Promise.of(getPath(paths))
+            } else {
+                return buildPaths(paths).map(SnodeAPI.sharedContext) { newPaths ->
+                    getPath(newPaths)
+                }
+            }
+        } else {
+            return buildPaths(listOf()).map(SnodeAPI.sharedContext) { newPaths ->
+                getPath(newPaths)
+            }
+        }
+    }
+
+    private fun dropGuardSnode(snode: Snode) {
+        guardSnodes = guardSnodes.filter { it != snode }.toSet()
+    }
+
+    private fun dropSnode(snode: Snode) {
+        // We repair the path here because we can do it sync. In the case where we drop a whole
+        // path we leave the re-building up to getPath() because re-building the path in that case
+        // is async.
+        snodeFailureCount[snode] = 0
+        val oldPaths = paths.toMutableList()
+        val pathIndex = oldPaths.indexOfFirst { it.contains(snode) }
+        if (pathIndex == -1) { return }
+        val path = oldPaths[pathIndex].toMutableList()
+        val snodeIndex = path.indexOf(snode)
+        if (snodeIndex == -1) { return }
+        path.removeAt(snodeIndex)
+        val unusedSnodes = SnodeAPI.snodePool.minus(oldPaths.flatten())
+        if (unusedSnodes.isEmpty()) { throw InsufficientSnodesException() }
+        path.add(unusedSnodes.getRandomElement())
+        // Don't test the new snode as this would reveal the user's IP
+        oldPaths.removeAt(pathIndex)
+        val newPaths = oldPaths + listOf( path )
+        paths = newPaths
+    }
+
+    private fun dropPath(path: Path) {
+        pathFailureCount[path] = 0
+        val paths = OnionRequestAPI.paths.toMutableList()
+        val pathIndex = paths.indexOf(path)
+        if (pathIndex == -1) { return }
+        paths.removeAt(pathIndex)
+        OnionRequestAPI.paths = paths
+    }
+
+    /**
+     * Builds an onion around `payload` and returns the result.
+     */
+    private fun buildOnionForDestination(payload: Map<*, *>, destination: Destination): Promise<OnionBuildingResult, Exception> {
+        lateinit var guardSnode: Snode
+        lateinit var destinationSymmetricKey: ByteArray // Needed by LokiAPI to decrypt the response sent back by the destination
+        lateinit var encryptionResult: EncryptionResult
+        val snodeToExclude = when (destination) {
+            is Destination.Snode -> destination.snode
+            is Destination.Server -> null
+        }
+        return getPath(snodeToExclude).bind(SnodeAPI.sharedContext) { path ->
+            guardSnode = path.first()
+            // Encrypt in reverse order, i.e. the destination first
+            OnionRequestEncryption.encryptPayloadForDestination(payload, destination).bind(SnodeAPI.sharedContext) { r ->
+                destinationSymmetricKey = r.symmetricKey
+                // Recursively encrypt the layers of the onion (again in reverse order)
+                encryptionResult = r
+                @Suppress("NAME_SHADOWING") var path = path
+                var rhs = destination
+                fun addLayer(): Promise<EncryptionResult, Exception> {
+                    if (path.isEmpty()) {
+                        return Promise.of(encryptionResult)
+                    } else {
+                        val lhs = Destination.Snode(path.last())
+                        path = path.dropLast(1)
+                        return OnionRequestEncryption.encryptHop(lhs, rhs, encryptionResult).bind(SnodeAPI.sharedContext) { r ->
+                            encryptionResult = r
+                            rhs = lhs
+                            addLayer()
+                        }
+                    }
+                }
+                addLayer()
+            }
+        }.map(SnodeAPI.sharedContext) { OnionBuildingResult(guardSnode, encryptionResult, destinationSymmetricKey) }
+    }
+
+    /**
+     * Sends an onion request to `destination`. Builds new paths as needed.
+     */
+    private fun sendOnionRequest(destination: Destination, payload: Map<*, *>, isJSONRequired: Boolean = true): Promise<Map<*, *>, Exception> {
+        val deferred = deferred<Map<*, *>, Exception>()
+        lateinit var guardSnode: Snode
+        buildOnionForDestination(payload, destination).success { result ->
+            guardSnode = result.guardSnode
+            val url = "${guardSnode.address}:${guardSnode.port}/onion_req/v2"
+            val finalEncryptionResult = result.finalEncryptionResult
+            val onion = finalEncryptionResult.ciphertext
+            if (destination is Destination.Server && onion.count().toDouble() > 0.75 * FileServerAPI.maxFileSize.toDouble()) {
+                Log.d("Loki", "Approaching request size limit: ~${onion.count()} bytes.")
+            }
+            @Suppress("NAME_SHADOWING") val parameters = mapOf(
+                "ephemeral_key" to finalEncryptionResult.ephemeralPublicKey.toHexString()
+            )
+            val body: ByteArray
+            try {
+                body = OnionRequestEncryption.encode(onion, parameters)
+            } catch (exception: Exception) {
+                return@success deferred.reject(exception)
+            }
+            val destinationSymmetricKey = result.destinationSymmetricKey
+            Thread {
+                try {
+                    val json = HTTP.execute(HTTP.Verb.POST, url, body)
+                    val base64EncodedIVAndCiphertext = json["result"] as? String ?: return@Thread deferred.reject(Exception("Invalid JSON"))
+                    val ivAndCiphertext = Base64.decode(base64EncodedIVAndCiphertext)
+                    try {
+                        val plaintext = AESGCM.decrypt(ivAndCiphertext, destinationSymmetricKey)
+                        try {
+                            @Suppress("NAME_SHADOWING") val json = JsonUtil.fromJson(plaintext.toString(Charsets.UTF_8), Map::class.java)
+                            val statusCode = json["status"] as Int
+                            if (statusCode == 406) {
+                                @Suppress("NAME_SHADOWING") val body = mapOf( "result" to "Your clock is out of sync with the service node network." )
+                                val exception = HTTPRequestFailedAtDestinationException(statusCode, body)
+                                return@Thread deferred.reject(exception)
+                            } else if (json["body"] != null) {
+                                @Suppress("NAME_SHADOWING") val body: Map<*, *>
+                                if (json["body"] is Map<*, *>) {
+                                    body = json["body"] as Map<*, *>
+                                } else {
+                                    val bodyAsString = json["body"] as String
+                                    if (!isJSONRequired) {
+                                        body = mapOf( "result" to bodyAsString )
+                                    } else {
+                                        body = JsonUtil.fromJson(bodyAsString, Map::class.java)
+                                    }
+                                }
+                                if (statusCode != 200) {
+                                    val exception = HTTPRequestFailedAtDestinationException(statusCode, body)
+                                    return@Thread deferred.reject(exception)
+                                }
+                                deferred.resolve(body)
+                            } else {
+                                if (statusCode != 200) {
+                                    val exception = HTTPRequestFailedAtDestinationException(statusCode, json)
+                                    return@Thread deferred.reject(exception)
+                                }
+                                deferred.resolve(json)
+                            }
+                        } catch (exception: Exception) {
+                            deferred.reject(Exception("Invalid JSON: ${plaintext.toString(Charsets.UTF_8)}."))
+                        }
+                    } catch (exception: Exception) {
+                        deferred.reject(exception)
+                    }
+                } catch (exception: Exception) {
+                    deferred.reject(exception)
+                }
+            }.start()
+        }.fail { exception ->
+            deferred.reject(exception)
+        }
+        val promise = deferred.promise
+        promise.fail { exception ->
+            val path = paths.firstOrNull { it.contains(guardSnode) }
+            if (exception is HTTP.HTTPRequestFailedException) {
+                fun handleUnspecificError() {
+                    if (path == null) { return }
+                    var pathFailureCount = OnionRequestAPI.pathFailureCount[path] ?: 0
+                    pathFailureCount += 1
+                    if (pathFailureCount >= pathFailureThreshold) {
+                        dropGuardSnode(guardSnode)
+                        path.forEach { snode ->
+                            @Suppress("ThrowableNotThrown")
+                            SnodeAPI.handleSnodeError(exception.statusCode, exception.json, snode, null) // Intentionally don't throw
+                        }
+                        dropPath(path)
+                    } else {
+                        OnionRequestAPI.pathFailureCount[path] = pathFailureCount
+                    }
+                }
+                val json = exception.json
+                val message = json?.get("result") as? String
+                val prefix = "Next node not found: "
+                if (message != null && message.startsWith(prefix)) {
+                    val ed25519PublicKey = message.substringAfter(prefix)
+                    val snode = path?.firstOrNull { it.publicKeySet!!.ed25519Key == ed25519PublicKey }
+                    if (snode != null) {
+                        var snodeFailureCount = OnionRequestAPI.snodeFailureCount[snode] ?: 0
+                        snodeFailureCount += 1
+                        if (snodeFailureCount >= snodeFailureThreshold) {
+                            @Suppress("ThrowableNotThrown")
+                            SnodeAPI.handleSnodeError(exception.statusCode, json, snode, null) // Intentionally don't throw
+                            try {
+                                dropSnode(snode)
+                            } catch (exception: Exception) {
+                                handleUnspecificError()
+                            }
+                        } else {
+                            OnionRequestAPI.snodeFailureCount[snode] = snodeFailureCount
+                        }
+                    } else {
+                        handleUnspecificError()
+                    }
+                } else if (message == "Loki Server error") {
+                    // Do nothing
+                } else {
+                    handleUnspecificError()
+                }
+            }
+        }
+        return promise
+    }
+    // endregion
+
+    // region Internal API
+    /**
+     * Sends an onion request to `snode`. Builds new paths as needed.
+     */
+    internal fun sendOnionRequest(method: Snode.Method, parameters: Map<*, *>, snode: Snode, publicKey: String): Promise<Map<*, *>, Exception> {
+        val payload = mapOf( "method" to method.rawValue, "params" to parameters )
+        return sendOnionRequest(Destination.Snode(snode), payload).recover { exception ->
+            val httpRequestFailedException = exception as? HTTP.HTTPRequestFailedException
+            if (httpRequestFailedException != null) {
+                val error = SnodeAPI.handleSnodeError(httpRequestFailedException.statusCode, httpRequestFailedException.json, snode, publicKey)
+                if (error != null) { throw error }
+            }
+            throw exception
+        }
+    }
+
+    /**
+     * Sends an onion request to `server`. Builds new paths as needed.
+     *
+     * `publicKey` is the hex encoded public key of the user the call is associated with. This is needed for swarm cache maintenance.
+     */
+    public fun sendOnionRequest(request: Request, server: String, x25519PublicKey: String, target: String = "/loki/v3/lsrpc", isJSONRequired: Boolean = true): Promise<Map<*, *>, Exception> {
+        val headers = request.getHeadersForOnionRequest()
+        val url = request.url()
+        val urlAsString = url.toString()
+        val host = url.host()
+        val endpoint = when {
+            server.count() < urlAsString.count() -> urlAsString.substringAfter("$server/")
+            else -> ""
+        }
+        val body = request.getBodyForOnionRequest() ?: "null"
+        val payload = mapOf(
+            "body" to body,
+            "endpoint" to endpoint,
+            "method" to request.method(),
+            "headers" to headers
+        )
+        val destination = Destination.Server(host, target, x25519PublicKey)
+        return sendOnionRequest(destination, payload, isJSONRequired).recover { exception ->
+            Log.d("Loki", "Couldn't reach server: $urlAsString due to error: $exception.")
+            throw exception
+        }
+    }
+    // endregion
+}

libsession/src/main/java/org/session/libsession/snode/OnionRequestEncryption.kt

@@ -0,0 +1,94 @@
+package org.session.libsession.snode
+
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.deferred
+import org.session.libsignal.service.internal.util.JsonUtil
+import org.session.libsession.utilities.AESGCM.EncryptionResult
+import org.session.libsession.utilities.AESGCM
+import org.session.libsignal.service.loki.utilities.toHexString
+import java.nio.Buffer
+import java.nio.ByteBuffer
+import java.nio.ByteOrder
+
+object OnionRequestEncryption {
+
+    internal fun encode(ciphertext: ByteArray, json: Map<*, *>): ByteArray {
+        // The encoding of V2 onion requests looks like: | 4 bytes: size N of ciphertext | N bytes: ciphertext | json as utf8 |
+        val jsonAsData = JsonUtil.toJson(json).toByteArray()
+        val ciphertextSize = ciphertext.size
+        val buffer = ByteBuffer.allocate(Int.SIZE_BYTES)
+        buffer.order(ByteOrder.LITTLE_ENDIAN)
+        buffer.putInt(ciphertextSize)
+        val ciphertextSizeAsData = ByteArray(buffer.capacity())
+        // Casting here avoids an issue where this gets compiled down to incorrect byte code. See
+        // https://github.com/eclipse/jetty.project/issues/3244 for more info
+        (buffer as Buffer).position(0)
+        buffer.get(ciphertextSizeAsData)
+        return ciphertextSizeAsData + ciphertext + jsonAsData
+    }
+
+    /**
+     * Encrypts `payload` for `destination` and returns the result. Use this to build the core of an onion request.
+     */
+    internal fun encryptPayloadForDestination(payload: Map<*, *>, destination: OnionRequestAPI.Destination): Promise<EncryptionResult, Exception> {
+        val deferred = deferred<EncryptionResult, Exception>()
+        Thread {
+            try {
+                // Wrapping isn't needed for file server or open group onion requests
+                when (destination) {
+                    is OnionRequestAPI.Destination.Snode -> {
+                        val snodeX25519PublicKey = destination.snode.publicKeySet!!.x25519Key
+                        val payloadAsData = JsonUtil.toJson(payload).toByteArray()
+                        val plaintext = encode(payloadAsData, mapOf( "headers" to "" ))
+                        val result = AESGCM.encrypt(plaintext, snodeX25519PublicKey)
+                        deferred.resolve(result)
+                    }
+                    is OnionRequestAPI.Destination.Server -> {
+                        val plaintext = JsonUtil.toJson(payload).toByteArray()
+                        val result = AESGCM.encrypt(plaintext, destination.x25519PublicKey)
+                        deferred.resolve(result)
+                    }
+                }
+            } catch (exception: Exception) {
+                deferred.reject(exception)
+            }
+        }.start()
+        return deferred.promise
+    }
+
+    /**
+     * Encrypts the previous encryption result (i.e. that of the hop after this one) for this hop. Use this to build the layers of an onion request.
+     */
+    internal fun encryptHop(lhs: OnionRequestAPI.Destination, rhs: OnionRequestAPI.Destination, previousEncryptionResult: EncryptionResult): Promise<EncryptionResult, Exception> {
+        val deferred = deferred<EncryptionResult, Exception>()
+        Thread {
+            try {
+                val payload: MutableMap<String, Any>
+                when (rhs) {
+                    is OnionRequestAPI.Destination.Snode -> {
+                        payload = mutableMapOf( "destination" to rhs.snode.publicKeySet!!.ed25519Key )
+                    }
+                    is OnionRequestAPI.Destination.Server -> {
+                        payload = mutableMapOf( "host" to rhs.host, "target" to rhs.target, "method" to "POST" )
+                    }
+                }
+                payload["ephemeral_key"] = previousEncryptionResult.ephemeralPublicKey.toHexString()
+                val x25519PublicKey: String
+                when (lhs) {
+                    is OnionRequestAPI.Destination.Snode -> {
+                        x25519PublicKey = lhs.snode.publicKeySet!!.x25519Key
+                    }
+                    is OnionRequestAPI.Destination.Server -> {
+                        x25519PublicKey = lhs.x25519PublicKey
+                    }
+                }
+                val plaintext = encode(previousEncryptionResult.ciphertext, payload)
+                val result = AESGCM.encrypt(plaintext, x25519PublicKey)
+                deferred.resolve(result)
+            } catch (exception: Exception) {
+                deferred.reject(exception)
+            }
+        }.start()
+        return deferred.promise
+    }
+}

libsession/src/main/java/org/session/libsession/snode/Snode.kt

@@ -0,0 +1,34 @@
+package org.session.libsession.snode
+
+public class Snode(val address: String, val port: Int, val publicKeySet: KeySet?) {
+
+    val ip: String get() = address.removePrefix("https://")
+
+    internal enum class Method(val rawValue: String) {
+        /**
+         * Only supported by snode targets.
+         */
+        GetSwarm("get_snodes_for_pubkey"),
+        /**
+         * Only supported by snode targets.
+         */
+        GetMessages("retrieve"),
+        SendMessage("store")
+    }
+
+    data class KeySet(val ed25519Key: String, val x25519Key: String)
+
+    override fun equals(other: Any?): Boolean {
+        return if (other is Snode) {
+            address == other.address && port == other.port
+        } else {
+            false
+        }
+    }
+
+    override fun hashCode(): Int {
+        return address.hashCode() xor port.hashCode()
+    }
+
+    override fun toString(): String { return "$address:$port" }
+}

libsession/src/main/java/org/session/libsession/snode/SnodeAPI.kt

@@ -0,0 +1,370 @@
+@file:Suppress("NAME_SHADOWING")
+
+package org.session.libsession.snode
+
+import nl.komponents.kovenant.Kovenant
+import nl.komponents.kovenant.Promise
+import nl.komponents.kovenant.deferred
+import nl.komponents.kovenant.functional.bind
+import nl.komponents.kovenant.functional.map
+import nl.komponents.kovenant.task
+
+import org.session.libsession.snode.utilities.getRandomElement
+
+import org.session.libsignal.libsignal.logging.Log
+import org.session.libsignal.service.internal.push.SignalServiceProtos
+import org.session.libsignal.service.internal.util.Base64
+import org.session.libsignal.service.loki.api.MessageWrapper
+import org.session.libsignal.service.loki.api.utilities.HTTP
+import org.session.libsignal.service.loki.utilities.createContext
+import org.session.libsignal.service.loki.utilities.prettifiedDescription
+import org.session.libsignal.service.loki.utilities.retryIfNeeded
+import org.session.libsignal.service.internal.push.SignalServiceProtos.Envelope
+
+import java.security.SecureRandom
+
+object SnodeAPI {
+    val database = Configuration.shared.storage
+    val broadcaster = Configuration.shared.broadcaster
+    val sharedContext = Kovenant.createContext("LokiAPISharedContext")
+    val messageSendingContext = Kovenant.createContext("LokiAPIMessageSendingContext")
+    val messagePollingContext = Kovenant.createContext("LokiAPIMessagePollingContext")
+
+    internal var snodeFailureCount: MutableMap<Snode, Int> = mutableMapOf()
+    internal var snodePool: Set<Snode>
+        get() = database.getSnodePool()
+        set(newValue) { database.setSnodePool(newValue) }
+
+    // Settings
+    private val maxRetryCount = 6
+    private val minimumSnodePoolCount = 64
+    private val minimumSwarmSnodeCount = 2
+    private val seedNodePool: Set<String> = setOf( "https://storage.seed1.loki.network", "https://storage.seed3.loki.network", "https://public.loki.foundation" )
+    internal val snodeFailureThreshold = 4
+    private val targetSwarmSnodeCount = 2
+
+    private val useOnionRequests = true
+
+    internal var powDifficulty = 1
+
+    // Error
+    internal sealed class Error(val description: String) : Exception() {
+        object Generic : Error("An error occurred.")
+        object ClockOutOfSync : Error("The user's clock is out of sync with the service node network.")
+        object RandomSnodePoolUpdatingFailed : Error("Failed to update random service node pool.")
+    }
+
+    // Internal API
+    internal fun invoke(method: Snode.Method, snode: Snode, publicKey: String, parameters: Map<String, String>): RawResponsePromise {
+        val url = "${snode.address}:${snode.port}/storage_rpc/v1"
+        if (useOnionRequests) {
+            return OnionRequestAPI.sendOnionRequest(method, parameters, snode, publicKey)
+        } else {
+            val deferred = deferred<Map<*, *>, Exception>()
+            Thread {
+                val payload = mapOf( "method" to method.rawValue, "params" to parameters )
+                try {
+                    val json = HTTP.execute(HTTP.Verb.POST, url, payload)
+                    deferred.resolve(json)
+                } catch (exception: Exception) {
+                    val httpRequestFailedException = exception as? HTTP.HTTPRequestFailedException
+                    if (httpRequestFailedException != null) {
+                        val error = handleSnodeError(httpRequestFailedException.statusCode, httpRequestFailedException.json, snode, publicKey)
+                        if (error != null) { return@Thread deferred.reject(exception) }
+                    }
+                    Log.d("Loki", "Unhandled exception: $exception.")
+                    deferred.reject(exception)
+                }
+            }.start()
+            return deferred.promise
+        }
+    }
+
+    internal fun getRandomSnode(): Promise<Snode, Exception> {
+        val snodePool = this.snodePool
+        if (snodePool.count() < minimumSnodePoolCount) {
+            val target = seedNodePool.random()
+            val url = "$target/json_rpc"
+            Log.d("Loki", "Populating snode pool using: $target.")
+            val parameters = mapOf(
+                    "method" to "get_n_service_nodes",
+                    "params" to mapOf(
+                            "active_only" to true,
+                            "fields" to mapOf( "public_ip" to true, "storage_port" to true, "pubkey_x25519" to true, "pubkey_ed25519" to true )
+                    )
+            )
+            val deferred = deferred<Snode, Exception>()
+            deferred<org.session.libsignal.service.loki.api.Snode, Exception>(SnodeAPI.sharedContext)
+            Thread {
+                try {
+                    val json = HTTP.execute(HTTP.Verb.POST, url, parameters, useSeedNodeConnection = true)
+                    val intermediate = json["result"] as? Map<*, *>
+                    val rawSnodes = intermediate?.get("service_node_states") as? List<*>
+                    if (rawSnodes != null) {
+                        val snodePool = rawSnodes.mapNotNull { rawSnode ->
+                            val rawSnodeAsJSON = rawSnode as? Map<*, *>
+                            val address = rawSnodeAsJSON?.get("public_ip") as? String
+                            val port = rawSnodeAsJSON?.get("storage_port") as? Int
+                            val ed25519Key = rawSnodeAsJSON?.get("pubkey_ed25519") as? String
+                            val x25519Key = rawSnodeAsJSON?.get("pubkey_x25519") as? String
+                            if (address != null && port != null && ed25519Key != null && x25519Key != null && address != "0.0.0.0") {
+                                Snode("https://$address", port, Snode.KeySet(ed25519Key, x25519Key))
+                            } else {
+                                Log.d("Loki", "Failed to parse: ${rawSnode?.prettifiedDescription()}.")
+                                null
+                            }
+                        }.toMutableSet()
+                        Log.d("Loki", "Persisting snode pool to database.")
+                        this.snodePool = snodePool
+                        try {
+                            deferred.resolve(snodePool.getRandomElement())
+                        } catch (exception: Exception) {
+                            Log.d("Loki", "Got an empty snode pool from: $target.")
+                            deferred.reject(SnodeAPI.Error.Generic)
+                        }
+                    } else {
+                        Log.d("Loki", "Failed to update snode pool from: ${(rawSnodes as List<*>?)?.prettifiedDescription()}.")
+                        deferred.reject(SnodeAPI.Error.Generic)
+                    }
+                } catch (exception: Exception) {
+                    deferred.reject(exception)
+                }
+            }.start()
+            return deferred.promise
+        } else {
+            return Promise.of(snodePool.getRandomElement())
+        }
+    }
+
+    internal fun dropSnodeFromSwarmIfNeeded(snode: Snode, publicKey: String) {
+        val swarm = database.getSwarm(publicKey)?.toMutableSet()
+        if (swarm != null && swarm.contains(snode)) {
+            swarm.remove(snode)
+            database.setSwarm(publicKey, swarm)
+        }
+    }
+
+    internal fun getSingleTargetSnode(publicKey: String): Promise<Snode, Exception> {
+        // SecureRandom() should be cryptographically secure
+        return getSwarm(publicKey).map { it.shuffled(SecureRandom()).random() }
+    }
+
+    // Public API
+    fun getTargetSnodes(publicKey: String): Promise<List<Snode>, Exception> {
+        // SecureRandom() should be cryptographically secure
+        return getSwarm(publicKey).map { it.shuffled(SecureRandom()).take(targetSwarmSnodeCount) }
+    }
+
+    fun getSwarm(publicKey: String): Promise<Set<Snode>, Exception> {
+        val cachedSwarm = database.getSwarm(publicKey)
+        if (cachedSwarm != null && cachedSwarm.size >= minimumSwarmSnodeCount) {
+            val cachedSwarmCopy = mutableSetOf<Snode>() // Workaround for a Kotlin compiler issue
+            cachedSwarmCopy.addAll(cachedSwarm)
+            return task { cachedSwarmCopy }
+        } else {
+            val parameters = mapOf( "pubKey" to publicKey )
+            return getRandomSnode().bind {
+                invoke(Snode.Method.GetSwarm, it, publicKey, parameters)
+            }.map(SnodeAPI.sharedContext) {
+                parseSnodes(it).toSet()
+            }.success {
+                database.setSwarm(publicKey, it)
+            }
+        }
+    }
+
+    fun getRawMessages(snode: Snode, publicKey: String): RawResponsePromise {
+        val lastHashValue = database.getLastMessageHashValue(snode, publicKey) ?: ""
+        val parameters = mapOf( "pubKey" to publicKey, "lastHash" to lastHashValue )
+        return invoke(Snode.Method.GetMessages, snode, publicKey, parameters)
+    }
+
+    fun getMessages(publicKey: String): MessageListPromise {
+        return retryIfNeeded(maxRetryCount) {
+           getSingleTargetSnode(publicKey).bind(messagePollingContext) { snode ->
+                getRawMessages(snode, publicKey).map(messagePollingContext) { parseRawMessagesResponse(it, snode, publicKey) }
+            }
+        }
+    }
+
+    fun sendMessage(message: SnodeMessage): Promise<Set<RawResponsePromise>, Exception> {
+        val destination = message.recipient
+        fun broadcast(event: String) {
+            val dayInMs: Long = 86400000
+            if (message.ttl != dayInMs && message.ttl != 4 * dayInMs) { return }
+            broadcaster.broadcast(event, message.timestamp)
+        }
+        broadcast("calculatingPoW")
+        return retryIfNeeded(maxRetryCount) {
+            getTargetSnodes(destination).map(messageSendingContext) { swarm ->
+                swarm.map { snode ->
+                    broadcast("sendingMessage")
+                    val parameters = message.toJSON()
+                    retryIfNeeded(maxRetryCount) {
+                        invoke(Snode.Method.SendMessage, snode, destination, parameters).map(messageSendingContext) { rawResponse ->
+                            val json = rawResponse as? Map<*, *>
+                            val powDifficulty = json?.get("difficulty") as? Int
+                            if (powDifficulty != null) {
+                                if (powDifficulty != SnodeAPI.powDifficulty && powDifficulty < 100) {
+                                    Log.d("Loki", "Setting proof of work difficulty to $powDifficulty (snode: $snode).")
+                                    SnodeAPI.powDifficulty = powDifficulty
+                                }
+                            } else {
+                                Log.d("Loki", "Failed to update proof of work difficulty from: ${rawResponse.prettifiedDescription()}.")
+                            }
+                            rawResponse
+                        }
+                    }
+                }.toSet()
+            }
+        }
+    }
+
+    // Parsing
+    private fun parseSnodes(rawResponse: Any): List<Snode> {
+        val json = rawResponse as? Map<*, *>
+        val rawSnodes = json?.get("snodes") as? List<*>
+        if (rawSnodes != null) {
+            return rawSnodes.mapNotNull { rawSnode ->
+                val rawSnodeAsJSON = rawSnode as? Map<*, *>
+                val address = rawSnodeAsJSON?.get("ip") as? String
+                val portAsString = rawSnodeAsJSON?.get("port") as? String
+                val port = portAsString?.toInt()
+                val ed25519Key = rawSnodeAsJSON?.get("pubkey_ed25519") as? String
+                val x25519Key = rawSnodeAsJSON?.get("pubkey_x25519") as? String
+                if (address != null && port != null && ed25519Key != null && x25519Key != null && address != "0.0.0.0") {
+                    Snode("https://$address", port, Snode.KeySet(ed25519Key, x25519Key))
+                } else {
+                    Log.d("Loki", "Failed to parse snode from: ${rawSnode?.prettifiedDescription()}.")
+                    null
+                }
+            }
+        } else {
+            Log.d("Loki", "Failed to parse snodes from: ${rawResponse.prettifiedDescription()}.")
+            return listOf()
+        }
+    }
+
+    private fun parseRawMessagesResponse(rawResponse: RawResponse, snode: Snode, publicKey: String): List<Envelope> {
+        val messages = rawResponse["messages"] as? List<*>
+        return if (messages != null) {
+            updateLastMessageHashValueIfPossible(snode, publicKey, messages)
+            val newRawMessages = removeDuplicates(publicKey, messages)
+            parseEnvelopes(newRawMessages)
+        } else {
+            listOf()
+        }
+    }
+
+    private fun updateLastMessageHashValueIfPossible(snode: Snode, publicKey: String, rawMessages: List<*>) {
+        val lastMessageAsJSON = rawMessages.lastOrNull() as? Map<*, *>
+        val hashValue = lastMessageAsJSON?.get("hash") as? String
+        val expiration = lastMessageAsJSON?.get("expiration") as? Int
+        if (hashValue != null) {
+            database.setLastMessageHashValue(snode, publicKey, hashValue)
+        } else if (rawMessages.isNotEmpty()) {
+            Log.d("Loki", "Failed to update last message hash value from: ${rawMessages.prettifiedDescription()}.")
+        }
+    }
+
+    private fun removeDuplicates(publicKey: String, rawMessages: List<*>): List<*> {
+        val receivedMessageHashValues = database.getReceivedMessageHashValues(publicKey)?.toMutableSet() ?: mutableSetOf()
+        return rawMessages.filter { rawMessage ->
+            val rawMessageAsJSON = rawMessage as? Map<*, *>
+            val hashValue = rawMessageAsJSON?.get("hash") as? String
+            if (hashValue != null) {
+                val isDuplicate = receivedMessageHashValues.contains(hashValue)
+                receivedMessageHashValues.add(hashValue)
+                database.setReceivedMessageHashValues(publicKey, receivedMessageHashValues)
+                !isDuplicate
+            } else {
+                Log.d("Loki", "Missing hash value for message: ${rawMessage?.prettifiedDescription()}.")
+                false
+            }
+        }
+    }
+
+    private fun parseEnvelopes(rawMessages: List<*>): List<Envelope> {
+        return rawMessages.mapNotNull { rawMessage ->
+            val rawMessageAsJSON = rawMessage as? Map<*, *>
+            val base64EncodedData = rawMessageAsJSON?.get("data") as? String
+            val data = base64EncodedData?.let { Base64.decode(it) }
+            if (data != null) {
+                try {
+                    MessageWrapper.unwrap(data)
+                } catch (e: Exception) {
+                    Log.d("Loki", "Failed to unwrap data for message: ${rawMessage.prettifiedDescription()}.")
+                    null
+                }
+            } else {
+                Log.d("Loki", "Failed to decode data for message: ${rawMessage?.prettifiedDescription()}.")
+                null
+            }
+        }
+    }
+
+    // Error Handling
+    internal fun handleSnodeError(statusCode: Int, json: Map<*, *>?, snode: Snode, publicKey: String? = null): Exception? {
+        fun handleBadSnode() {
+            val oldFailureCount = snodeFailureCount[snode] ?: 0
+            val newFailureCount = oldFailureCount + 1
+            snodeFailureCount[snode] = newFailureCount
+            Log.d("Loki", "Couldn't reach snode at $snode; setting failure count to $newFailureCount.")
+            if (newFailureCount >= snodeFailureThreshold) {
+                Log.d("Loki", "Failure threshold reached for: $snode; dropping it.")
+                if (publicKey != null) {
+                    dropSnodeFromSwarmIfNeeded(snode, publicKey)
+                }
+                snodePool = snodePool.toMutableSet().minus(snode).toSet()
+                Log.d("Loki", "Snode pool count: ${snodePool.count()}.")
+                snodeFailureCount[snode] = 0
+            }
+        }
+        when (statusCode) {
+            400, 500, 503 -> { // Usually indicates that the snode isn't up to date
+                handleBadSnode()
+            }
+            406 -> {
+                Log.d("Loki", "The user's clock is out of sync with the service node network.")
+                broadcaster.broadcast("clockOutOfSync")
+                return Error.ClockOutOfSync
+            }
+            421 -> {
+                // The snode isn't associated with the given public key anymore
+                if (publicKey != null) {
+                    Log.d("Loki", "Invalidating swarm for: $publicKey.")
+                    dropSnodeFromSwarmIfNeeded(snode, publicKey)
+                } else {
+                    Log.d("Loki", "Got a 421 without an associated public key.")
+                }
+            }
+            432 -> {
+                // The PoW difficulty is too low
+                val powDifficulty = json?.get("difficulty") as? Int
+                if (powDifficulty != null) {
+                    if (powDifficulty < 100) {
+                        Log.d("Loki", "Setting proof of work difficulty to $powDifficulty (snode: $snode).")
+                        SnodeAPI.powDifficulty = powDifficulty
+                    } else {
+                        handleBadSnode()
+                    }
+                } else {
+                    Log.d("Loki", "Failed to update proof of work difficulty.")
+                }
+            }
+            else -> {
+                handleBadSnode()
+                Log.d("Loki", "Unhandled response code: ${statusCode}.")
+                return Error.Generic
+            }
+        }
+        return null
+    }
+
+
+}
+
+// Type Aliases
+typealias RawResponse = Map<*, *>
+typealias MessageListPromise = Promise<List<Envelope>, Exception>
+typealias RawResponsePromise = Promise<RawResponse, Exception>

libsession/src/main/java/org/session/libsession/snode/SnodeMessage.kt

@@ -0,0 +1,23 @@
+package org.session.libsession.snode
+
+data class SnodeMessage(
+    // The hex encoded public key of the recipient.
+    val recipient: String,
+    // The content of the message.
+    val data: String,
+    // The time to live for the message in milliseconds.
+    val ttl: Long,
+    // When the proof of work was calculated.
+    val timestamp: Long,
+    // The base 64 encoded proof of work.
+    val nonce: String
+) {
+    internal fun toJSON(): Map<String, String> {
+        return mutableMapOf(
+                "pubKey" to recipient,
+                "data" to data,
+                "ttl" to ttl.toString(),
+                "timestamp" to timestamp.toString(),
+                "nonce" to nonce)
+    }
+}

libsession/src/main/java/org/session/libsession/snode/StorageProtocol.kt

@@ -0,0 +1,15 @@
+package org.session.libsession.snode
+
+interface SnodeStorageProtocol {
+    fun getSnodePool(): Set<Snode>
+    fun setSnodePool(newValue: Set<Snode>)
+    fun getOnionRequestPaths(): List<List<Snode>>
+    fun clearOnionRequestPaths()
+    fun setOnionRequestPaths(newValue: List<List<Snode>>)
+    fun getSwarm(publicKey: String): Set<Snode>?
+    fun setSwarm(publicKey: String, newValue: Set<Snode>)
+    fun getLastMessageHashValue(snode: Snode, publicKey: String): String?
+    fun setLastMessageHashValue(snode: Snode, publicKey: String, newValue: String)
+    fun getReceivedMessageHashValues(publicKey: String): Set<String>?
+    fun setReceivedMessageHashValues(publicKey: String, newValue: Set<String>)
+}

libsession/src/main/java/org/session/libsession/snode/utilities/OKHTTPUtilities.kt

@@ -0,0 +1,49 @@
+package org.session.libsession.utilities
+
+import okhttp3.MultipartBody
+import okhttp3.Request
+import okio.Buffer
+import org.session.libsignal.service.internal.util.Base64
+import java.io.IOException
+import java.util.*
+
+internal fun Request.getHeadersForOnionRequest(): Map<String, Any> {
+    val result = mutableMapOf<String, Any>()
+    val contentType = body()?.contentType()
+    if (contentType != null) {
+        result["content-type"] = contentType.toString()
+    }
+    val headers = headers()
+    for (name in headers.names()) {
+        val value = headers.get(name)
+        if (value != null) {
+            if (value.toLowerCase(Locale.US) == "true" || value.toLowerCase(Locale.US) == "false") {
+                result[name] = value.toBoolean()
+            } else if (value.toIntOrNull() != null) {
+                result[name] = value.toInt()
+            } else {
+                result[name] = value
+            }
+        }
+    }
+    return result
+}
+
+internal fun Request.getBodyForOnionRequest(): Any? {
+    try {
+        val copyOfThis = newBuilder().build()
+        val buffer = Buffer()
+        val body = copyOfThis.body() ?: return null
+        body.writeTo(buffer)
+        val bodyAsData = buffer.readByteArray()
+        if (body is MultipartBody) {
+            val base64EncodedBody: String = Base64.encodeBytes(bodyAsData)
+            return mapOf( "fileUpload" to base64EncodedBody )
+        } else {
+            val charset = body.contentType()?.charset() ?: Charsets.UTF_8
+            return bodyAsData?.toString(charset)
+        }
+    } catch (e: IOException) {
+        return null
+    }
+}

libsession/src/main/java/org/session/libsession/snode/utilities/Random.kt

@@ -0,0 +1,18 @@
+package org.session.libsession.snode.utilities
+
+import java.security.SecureRandom
+
+/**
+ * Uses `SecureRandom` to pick an element from this collection.
+ */
+fun <T> Collection<T>.getRandomElementOrNull(): T? {
+    val index = SecureRandom().nextInt(size) // SecureRandom() should be cryptographically secure
+    return elementAtOrNull(index)
+}
+
+/**
+ * Uses `SecureRandom` to pick an element from this collection.
+ */
+fun <T> Collection<T>.getRandomElement(): T {
+    return getRandomElementOrNull()!!
+}

libsession/src/main/java/org/session/libsession/utilities/AESGCM.kt

@@ -0,0 +1,58 @@
+package org.session.libsession.utilities
+
+import org.whispersystems.curve25519.Curve25519
+import org.session.libsignal.libsignal.util.ByteUtil
+import org.session.libsignal.libsignal.util.Hex
+import org.session.libsignal.service.internal.util.Util
+import javax.crypto.Cipher
+import javax.crypto.Mac
+import javax.crypto.spec.GCMParameterSpec
+import javax.crypto.spec.SecretKeySpec
+
+internal object AESGCM {
+
+    internal data class EncryptionResult(
+            internal val ciphertext: ByteArray,
+            internal val symmetricKey: ByteArray,
+            internal val ephemeralPublicKey: ByteArray
+    )
+
+    internal val gcmTagSize = 128
+    internal val ivSize = 12
+
+    /**
+     * Sync. Don't call from the main thread.
+     */
+    internal fun decrypt(ivAndCiphertext: ByteArray, symmetricKey: ByteArray): ByteArray {
+        val iv = ivAndCiphertext.sliceArray(0 until ivSize)
+        val ciphertext = ivAndCiphertext.sliceArray(ivSize until ivAndCiphertext.count())
+        val cipher = Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(Cipher.DECRYPT_MODE, SecretKeySpec(symmetricKey, "AES"), GCMParameterSpec(gcmTagSize, iv))
+        return cipher.doFinal(ciphertext)
+    }
+
+    /**
+     * Sync. Don't call from the main thread.
+     */
+    internal fun encrypt(plaintext: ByteArray, symmetricKey: ByteArray): ByteArray {
+        val iv = Util.getSecretBytes(ivSize)
+        val cipher = Cipher.getInstance("AES/GCM/NoPadding")
+        cipher.init(Cipher.ENCRYPT_MODE, SecretKeySpec(symmetricKey, "AES"), GCMParameterSpec(gcmTagSize, iv))
+        return ByteUtil.combine(iv, cipher.doFinal(plaintext))
+    }
+
+    /**
+     * Sync. Don't call from the main thread.
+     */
+    internal fun encrypt(plaintext: ByteArray, hexEncodedX25519PublicKey: String): EncryptionResult {
+        val x25519PublicKey = Hex.fromStringCondensed(hexEncodedX25519PublicKey)
+        val ephemeralKeyPair = Curve25519.getInstance(Curve25519.BEST).generateKeyPair()
+        val ephemeralSharedSecret = Curve25519.getInstance(Curve25519.BEST).calculateAgreement(x25519PublicKey, ephemeralKeyPair.privateKey)
+        val mac = Mac.getInstance("HmacSHA256")
+        mac.init(SecretKeySpec("LOKI".toByteArray(), "HmacSHA256"))
+        val symmetricKey = mac.doFinal(ephemeralSharedSecret)
+        val ciphertext = encrypt(plaintext, symmetricKey)
+        return EncryptionResult(ciphertext, symmetricKey, ephemeralKeyPair.publicKey)
+    }
+
+}