Merge pull request #55 from loki-project/session-restore

Session restore

res/layout/conversation_activity.xml

@@ -104,6 +104,11 @@
                 android:indeterminate="false"
                 android:progress="80" />
 
+            <org.thoughtcrime.securesms.loki.SessionRestoreBannerView
+                android:id="@+id/sessionRestoreBannerView"
+                android:layout_width="match_parent"
+                android:layout_height="wrap_content" />
+
             <ViewStub
                 android:id="@+id/group_share_profile_view_stub"
                 android:layout_width="match_parent"

res/layout/conversation_item_update.xml

@@ -53,7 +53,7 @@
             style="@style/Signal.Text.Preview"
             android:layout_width="wrap_content"
             android:layout_height="wrap_content"
-            android:autoLink="all"
+            android:autoLink="none"
             android:gravity="center"
             android:linksClickable="true"
             android:textSize="@dimen/small_font_size"

res/layout/session_restore_banner.xml

@@ -0,0 +1,73 @@
+<?xml version="1.0" encoding="utf-8"?>
+<LinearLayout
+    xmlns:android="http://schemas.android.com/apk/res/android"
+    android:id="@+id/sessionRestoreBanner"
+    android:layout_width="match_parent"
+    android:layout_height="wrap_content"
+    android:background="@color/dialog_background"
+    android:orientation="vertical"
+    android:elevation="10dp">
+
+    <View
+        android:layout_width="match_parent"
+        android:layout_height="1px"
+        android:background="@color/separator" />
+
+    <LinearLayout
+        android:layout_width="match_parent"
+        android:layout_height="wrap_content"
+        android:orientation="vertical"
+        android:padding="@dimen/medium_spacing"
+        android:gravity="center_horizontal">
+
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:text="Session Out of Sync"
+            android:textColor="@color/text"
+            android:textStyle="bold"
+            android:textSize="@dimen/medium_font_size" />
+
+        <TextView
+            android:id="@+id/messageTextView"
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="@dimen/small_spacing"
+            android:text="@string/session_restore_banner_message"
+            android:textColor="@color/text"
+            android:textSize="@dimen/small_font_size"
+            android:textAlignment="center" />
+
+        <LinearLayout
+            android:layout_width="match_parent"
+            android:layout_height="wrap_content"
+            android:layout_marginTop="@dimen/small_spacing"
+            android:orientation="horizontal">
+
+            <Button
+                style="@style/UnimportantDialogButton"
+                android:id="@+id/dismissButton"
+                android:layout_width="0dp"
+                android:layout_height="@dimen/small_button_height"
+                android:layout_weight="1"
+                android:text="@string/session_restore_banner_dismiss_button_title" />
+
+            <Button
+                style="@style/ProminentDialogButton"
+                android:id="@+id/restoreButton"
+                android:layout_width="0dp"
+                android:layout_height="@dimen/small_button_height"
+                android:layout_weight="1"
+                android:layout_marginLeft="@dimen/medium_spacing"
+                android:text="@string/session_restore_banner_restore_button_title" />
+
+        </LinearLayout>
+
+    </LinearLayout>
+
+    <View
+        android:layout_width="match_parent"
+        android:layout_height="1px"
+        android:background="@color/separator" />
+
+</LinearLayout>

res/values/strings.xml

@@ -735,6 +735,7 @@
     <!-- MessageDisplayHelper -->
     <string name="MessageDisplayHelper_bad_encrypted_message">Bad encrypted message</string>
     <string name="MessageDisplayHelper_message_encrypted_for_non_existing_session">Message encrypted for non-existing session</string>
+    <string name="MessageRecord_session_restore_sent">You have sent a session restoration request to %s</string>
 
     <!-- MmsMessageRecord -->
     <string name="MmsMessageRecord_bad_encrypted_mms_message">Bad encrypted MMS message</string>
@@ -1651,6 +1652,10 @@
     <!-- Device unlink dialog -->
     <string name="dialog_device_unlink_title">Device unlinked</string>
     <string name="dialog_device_unlink_message">This device has been successfully unlinked</string>
+    <!-- Session restore banner -->
+    <string name="session_restore_banner_message">Would you like to restore your session with %s?</string>
+    <string name="session_restore_banner_dismiss_button_title">Dismiss</string>
+    <string name="session_restore_banner_restore_button_title">Restore</string>
 
     <!-- Loki -->
 

src/org/thoughtcrime/securesms/conversation/ConversationActivity.java

@@ -141,6 +141,7 @@ import org.thoughtcrime.securesms.database.MessagingDatabase.MarkedMessageInfo;
 import org.thoughtcrime.securesms.database.MmsSmsColumns.Types;
 import org.thoughtcrime.securesms.database.RecipientDatabase;
 import org.thoughtcrime.securesms.database.RecipientDatabase.RegisteredState;
+import org.thoughtcrime.securesms.database.SmsDatabase;
 import org.thoughtcrime.securesms.database.ThreadDatabase;
 import org.thoughtcrime.securesms.database.identity.IdentityRecordList;
 import org.thoughtcrime.securesms.database.model.MessageRecord;
@@ -162,6 +163,7 @@ import org.thoughtcrime.securesms.loki.LokiThreadDatabase;
 import org.thoughtcrime.securesms.loki.LokiThreadDatabaseDelegate;
 import org.thoughtcrime.securesms.loki.LokiUserDatabase;
 import org.thoughtcrime.securesms.loki.MultiDeviceUtilities;
+import org.thoughtcrime.securesms.loki.SessionRestoreBannerView;
 import org.thoughtcrime.securesms.loki.redesign.activities.HomeActivity;
 import org.thoughtcrime.securesms.loki.redesign.views.FriendRequestViewDelegate;
 import org.thoughtcrime.securesms.loki.redesign.views.MentionCandidateSelectionView;
@@ -248,6 +250,7 @@ import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Locale;
+import java.util.Set;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.concurrent.atomic.AtomicInteger;
@@ -372,6 +375,9 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
   // Multi Device
   private   boolean isFriendsWithAnyDevice = false;
 
+  // Restoration
+  protected SessionRestoreBannerView sessionRestoreBannerView;
+
   @Override
   protected void onPreCreate() {
     dynamicTheme.onCreate(this);
@@ -446,6 +452,17 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
       }
     });
 
+    sessionRestoreBannerView.setOnRestore(() -> {
+      this.restoreSession();
+      return Unit.INSTANCE;
+    });
+    sessionRestoreBannerView.setOnDismiss(() -> {
+      // TODO: Maybe silence for x minutes?
+      DatabaseFactory.getLokiThreadDatabase(ConversationActivity.this).removeAllSessionRestoreDevices(threadId);
+      updateSessionRestoreBanner();
+      return Unit.INSTANCE;
+    });
+
     LokiAPIUtilities.INSTANCE.populateUserHexEncodedPublicKeyCacheIfNeeded(threadId, this);
 
     LokiPublicChat publicChat = DatabaseFactory.getLokiThreadDatabase(this).getPublicChat(threadId);
@@ -539,6 +556,8 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     DatabaseFactory.getLokiThreadDatabase(this).setDelegate(this);
     updateInputPanel();
 
+    updateSessionRestoreBanner();
+
     Log.i(TAG, "onResume() Finished: " + (System.currentTimeMillis() - getIntent().getLongExtra(TIMING_EXTRA, 0)));
   }
 
@@ -1542,6 +1561,16 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     }
   }
 
+  protected void updateSessionRestoreBanner() {
+    Set<String> devices = DatabaseFactory.getLokiThreadDatabase(this).getSessionRestoreDevices(threadId);
+    if (devices.size() > 0) {
+      sessionRestoreBannerView.update(recipient);
+      sessionRestoreBannerView.show();
+    } else {
+      sessionRestoreBannerView.hide();
+    }
+  }
+
   private void updateDefaultSubscriptionId(Optional<Integer> defaultSubscriptionId) {
     Log.i(TAG, "updateDefaultSubscriptionId(" + defaultSubscriptionId.orNull() + ")");
     sendButton.setDefaultSubscriptionId(defaultSubscriptionId);
@@ -1639,6 +1668,7 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     searchNav              = ViewUtil.findById(this, R.id.conversation_search_nav);
     mentionCandidateSelectionViewContainer = ViewUtil.findById(this, R.id.mentionCandidateSelectionViewContainer);
     mentionCandidateSelectionView = ViewUtil.findById(this, R.id.userSelectionView);
+    sessionRestoreBannerView = ViewUtil.findById(this, R.id.sessionRestoreBannerView);
     messageStatusProgressBar = ViewUtil.findById(this, R.id.messageStatusProgressBar);
     muteIndicatorImageView = ViewUtil.findById(this, R.id.muteIndicatorImageView);
     actionBarSubtitleTextView = ViewUtil.findById(this, R.id.subtitleTextView);
@@ -2257,6 +2287,13 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
       this.updateInputPanel();
   }
 
+  @Override
+  public void handleSessionRestoreDevicesChanged(long threadId) {
+    if (threadId == this.threadId) {
+      runOnUiThread(this::updateSessionRestoreBanner);
+    }
+  }
+
   private void updateInputPanel() {
     /*
       isFriendsWithAnyDevice caches whether we are friends with any of the other users device.
@@ -3262,4 +3299,19 @@ public class ConversationActivity extends PassphraseRequiredActionBarActivity
     return TextSecurePreferences.getLocalNumber(this).equals(recipient.getAddress().serialize());
   }
   // endregion
+
+  public void restoreSession() {
+    // Loki - User clicked restore session
+    if (recipient.isGroupRecipient()) { return; }
+    LokiThreadDatabase lokiThreadDatabase = DatabaseFactory.getLokiThreadDatabase(this);
+    SmsDatabase smsDatabase = DatabaseFactory.getSmsDatabase(this);
+    Set<String> devices = lokiThreadDatabase.getSessionRestoreDevices(threadId);
+    for (String device : devices) { MessageSender.sendRestoreSessionMessage(this, device); }
+    long messageId = smsDatabase.insertMessageOutbox(threadId, new OutgoingTextMessage(recipient,"", 0, 0), false, System.currentTimeMillis(), null);
+    if (messageId > -1) {
+      smsDatabase.markAsLokiSessionRestoreSent(messageId);
+    }
+    lokiThreadDatabase.removeAllSessionRestoreDevices(threadId);
+    updateSessionRestoreBanner();
+  }
 }

src/org/thoughtcrime/securesms/conversation/ConversationFragment.java

@@ -361,7 +361,7 @@ public class ConversationFragment extends Fragment
       if (messageRecord.isGroupAction() || messageRecord.isCallLog() ||
           messageRecord.isJoined() || messageRecord.isExpirationTimerUpdate() ||
           messageRecord.isEndSession() || messageRecord.isIdentityUpdate() ||
-          messageRecord.isIdentityVerified() || messageRecord.isIdentityDefault())
+          messageRecord.isIdentityVerified() || messageRecord.isIdentityDefault() || messageRecord.isLokiSessionRestoreSent())
       {
         actionMessage = true;
       }

src/org/thoughtcrime/securesms/conversation/ConversationUpdateItem.java

@@ -113,6 +113,7 @@ public class ConversationUpdateItem extends LinearLayout
     else if (messageRecord.isIdentityUpdate())        setIdentityRecord(messageRecord);
     else if (messageRecord.isIdentityVerified() ||
              messageRecord.isIdentityDefault())       setIdentityVerifyUpdate(messageRecord);
+    else if (messageRecord.isLokiSessionRestoreSent()) setTextMessageRecord(messageRecord);
     else                                              throw new AssertionError("Neither group nor log nor joined.");
 
     if (batchSelected.contains(messageRecord)) setSelected(true);
@@ -203,6 +204,15 @@ public class ConversationUpdateItem extends LinearLayout
     date.setVisibility(GONE);
   }
 
+  private  void setTextMessageRecord(MessageRecord messageRecord) {
+    body.setText(messageRecord.getDisplayBody(getContext()));
+
+    icon.setVisibility(GONE);
+    title.setVisibility(GONE);
+    body.setVisibility(VISIBLE);
+    date.setVisibility(GONE);
+  }
+  
   @Override
   public void onModified(Recipient recipient) {
     Util.runOnMain(() -> bind(messageRecord, locale));

src/org/thoughtcrime/securesms/database/MmsSmsColumns.java

@@ -82,6 +82,9 @@ public interface MmsSmsColumns {
     protected static final long ENCRYPTION_REMOTE_DUPLICATE_BIT  = 0x04000000;
     protected static final long ENCRYPTION_REMOTE_LEGACY_BIT     = 0x02000000;
 
+    // Loki
+    protected static final long ENCRYPTION_LOKI_SESSION_RESTORE_SENT_BIT = 0x01000000;
+
     public static boolean isDraftMessageType(long type) {
       return (type & BASE_TYPE_MASK) == BASE_DRAFT_TYPE;
     }
@@ -230,6 +233,10 @@ public interface MmsSmsColumns {
       return (type & ENCRYPTION_REMOTE_NO_SESSION_BIT) != 0;
     }
 
+    public static boolean isLokiSessionRestoreSentType(long type) {
+      return (type & ENCRYPTION_LOKI_SESSION_RESTORE_SENT_BIT) != 0;
+    }
+
     public static boolean isLegacyType(long type) {
       return (type & ENCRYPTION_REMOTE_LEGACY_BIT) != 0 ||
              (type & ENCRYPTION_REMOTE_BIT) != 0;

src/org/thoughtcrime/securesms/database/SmsDatabase.java

@@ -47,6 +47,7 @@ import org.whispersystems.libsignal.util.guava.Optional;
 
 import java.io.IOException;
 import java.security.SecureRandom;
+import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.LinkedList;
 import java.util.List;
@@ -251,6 +252,10 @@ public class SmsDatabase extends MessagingDatabase {
     updateTypeBitmask(id, Types.ENCRYPTION_MASK, Types.ENCRYPTION_REMOTE_NO_SESSION_BIT);
   }
 
+  public void markAsLokiSessionRestoreSent(long id) {
+    updateTypeBitmask(id, Types.ENCRYPTION_MASK, Types.ENCRYPTION_LOKI_SESSION_RESTORE_SENT_BIT);
+  }
+
   public void markAsLegacyVersion(long id) {
     updateTypeBitmask(id, Types.ENCRYPTION_MASK, Types.ENCRYPTION_REMOTE_LEGACY_BIT);
   }

src/org/thoughtcrime/securesms/database/model/DisplayRecord.java

@@ -103,9 +103,9 @@ public abstract class DisplayRecord {
     return SmsDatabase.Types.isKeyExchangeType(type);
   }
 
-  public boolean isEndSession() {
+  public boolean isEndSession() { return SmsDatabase.Types.isEndSessionType(type); }
-    return SmsDatabase.Types.isEndSessionType(type);
+
-  }
+  public boolean isLokiSessionRestoreSent() { return SmsDatabase.Types.isLokiSessionRestoreSentType(type); }
 
   public boolean isGroupUpdate() {
     return SmsDatabase.Types.isGroupUpdate(type);

src/org/thoughtcrime/securesms/database/model/MessageRecord.java

@@ -180,7 +180,7 @@ public abstract class MessageRecord extends DisplayRecord {
 
   public boolean isUpdate() {
     return isGroupAction() || isJoined() || isExpirationTimerUpdate() || isCallLog() ||
-           isEndSession()  || isIdentityUpdate() || isIdentityVerified() || isIdentityDefault();
+           isEndSession()  || isIdentityUpdate() || isIdentityVerified() || isIdentityDefault() || isLokiSessionRestoreSent();
   }
 
   public boolean isMediaPending() {

src/org/thoughtcrime/securesms/database/model/SmsMessageRecord.java

@@ -82,6 +82,7 @@ public class SmsMessageRecord extends MessageRecord {
 
   @Override
   public SpannableString getDisplayBody(@NonNull Context context) {
+    Recipient recipient = getRecipient();
     if (SmsDatabase.Types.isFailedDecryptType(type)) {
       return emphasisAdded(context.getString(R.string.MessageDisplayHelper_bad_encrypted_message));
     } else if (isCorruptedKeyExchange()) {
@@ -100,6 +101,8 @@ public class SmsMessageRecord extends MessageRecord {
       return emphasisAdded(context.getString(R.string.SmsMessageRecord_duplicate_message));
     } else if (SmsDatabase.Types.isNoRemoteSessionType(type)) {
       return emphasisAdded(context.getString(R.string.MessageDisplayHelper_message_encrypted_for_non_existing_session));
+    } else if (isLokiSessionRestoreSent()) {
+      return emphasisAdded(context.getString(R.string.MessageRecord_session_restore_sent, recipient.toShortString()));
     } else if (isEndSession() && isOutgoing()) {
       return emphasisAdded(context.getString(R.string.SmsMessageRecord_secure_session_reset));
     } else if (isEndSession()) {

src/org/thoughtcrime/securesms/database/model/ThreadRecord.java

@@ -71,6 +71,7 @@ public class ThreadRecord extends DisplayRecord {
 
   @Override
   public SpannableString getDisplayBody(@NonNull Context context) {
+    Recipient recipient = getRecipient();
     if (isGroupUpdate()) {
       return emphasisAdded(context.getString(R.string.ThreadRecord_group_updated));
     } else if (isGroupQuit()) {
@@ -81,6 +82,8 @@ public class ThreadRecord extends DisplayRecord {
       return emphasisAdded(context.getString(R.string.MessageDisplayHelper_bad_encrypted_message));
     } else if (SmsDatabase.Types.isNoRemoteSessionType(type)) {
       return emphasisAdded(context.getString(R.string.MessageDisplayHelper_message_encrypted_for_non_existing_session));
+    } else if (isLokiSessionRestoreSent()) {
+      return emphasisAdded(context.getString(R.string.MessageRecord_session_restore_sent, recipient.toShortString()));
     } else if (SmsDatabase.Types.isEndSessionType(type)) {
       return emphasisAdded(context.getString(R.string.ThreadRecord_secure_session_reset));
     } else if (MmsSmsColumns.Types.isLegacyType(type)) {

src/org/thoughtcrime/securesms/jobs/PushDecryptJob.java

@@ -56,6 +56,7 @@ import org.thoughtcrime.securesms.database.StickerDatabase;
 import org.thoughtcrime.securesms.database.ThreadDatabase;
 import org.thoughtcrime.securesms.database.model.MessageRecord;
 import org.thoughtcrime.securesms.database.model.MmsMessageRecord;
+import org.thoughtcrime.securesms.database.model.SmsMessageRecord;
 import org.thoughtcrime.securesms.database.model.StickerRecord;
 import org.thoughtcrime.securesms.dependencies.InjectableType;
 import org.thoughtcrime.securesms.groups.GroupMessageProcessor;
@@ -278,6 +279,12 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
         cipher.validateBackgroundMessage(envelope, envelope.getContent());
       }
 
+      // Loki - Ignore any friend requests that we got before restoration
+      if (envelope.isFriendRequest() && envelope.getTimestamp() < TextSecurePreferences.getRestorationTime(context)) {
+        Log.d("Loki", "Ignoring friend request received before restoration.");
+        return;
+      }
+
       SignalServiceContent content = cipher.decrypt(envelope);
 
       if (shouldIgnore(content)) {
@@ -331,6 +338,8 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
             MultiDeviceUtilities.checkForRevocation(context);
           }
         } else {
+          // Loki - Don't process session restore message any further
+          if (message.isSessionRestore()) { return; }
           if (message.isEndSession()) handleEndSessionMessage(content, smsMessageId);
           else if (message.isGroupUpdate()) handleGroupMessage(content, message, smsMessageId);
           else if (message.isExpirationUpdate())
@@ -530,21 +539,24 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
     }
 
     if (threadId != null) {
+      resetSession(content.getSender(), threadId);
+      MessageNotifier.updateNotification(context, threadId);
+    }
+  }
+
+  private void resetSession(String hexEncodedPublicKey, long threadId) {
       TextSecureSessionStore sessionStore = new TextSecureSessionStore(context);
       LokiThreadDatabase lokiThreadDatabase = DatabaseFactory.getLokiThreadDatabase(context);
 
-      Log.d("Loki", "Received a session reset request from: " + content.getSender() + "; archiving the session.");
+      Log.d("Loki", "Received a session reset request from: " + hexEncodedPublicKey + "; archiving the session.");
 
-      sessionStore.archiveAllSessions(content.getSender());
+      sessionStore.archiveAllSessions(hexEncodedPublicKey);
       lokiThreadDatabase.setSessionResetStatus(threadId, LokiThreadSessionResetStatus.REQUEST_RECEIVED);
 
-      Log.d("Loki", "Sending a ping back to " + content.getSender() + ".");
+      Log.d("Loki", "Sending a ping back to " + hexEncodedPublicKey + ".");
-      String contactID = DatabaseFactory.getThreadDatabase(context).getRecipientForThreadId(threadId).getAddress().toString();
+      MessageSender.sendBackgroundMessage(context, hexEncodedPublicKey);
-      MessageSender.sendBackgroundMessage(context, contactID);
 
       SecurityEvent.broadcastSecurityUpdateEvent(context);
-      MessageNotifier.updateNotification(context, threadId);
-    }
   }
 
   private long handleSynchronizeSentEndSessionMessage(@NonNull SentTranscriptMessage message)
@@ -1177,17 +1189,30 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
   }
 
   private void storePreKeyBundleIfNeeded(@NonNull SignalServiceEnvelope envelope, @NonNull SignalServiceContent content) {
-    if (content.lokiServiceMessage.isPresent()) {
+    Recipient sender = Recipient.from(context, Address.fromSerialized(content.getSender()), false);
+    if (!sender.isGroupRecipient() && content.lokiServiceMessage.isPresent()) {
       LokiServiceMessage lokiMessage = content.lokiServiceMessage.get();
       if (lokiMessage.getPreKeyBundleMessage() != null) {
         int registrationID = TextSecurePreferences.getLocalRegistrationId(context);
         LokiPreKeyBundleDatabase lokiPreKeyBundleDatabase = DatabaseFactory.getLokiPreKeyBundleDatabase(context);
+        ThreadDatabase threadDatabase = DatabaseFactory.getThreadDatabase(context);
+        LokiThreadDatabase lokiThreadDatabase = DatabaseFactory.getLokiThreadDatabase(context);
 
-        // Store the latest PreKeyBundle
+        // Loki - Store the latest pre key bundle
         if (registrationID > 0) {
-          Log.d("Loki", "Received a pre key bundle from: " + envelope.getSource() + ".");
+          Log.d("Loki", "Received a pre key bundle from: " + content.getSender() + ".");
           PreKeyBundle preKeyBundle = lokiMessage.getPreKeyBundleMessage().getPreKeyBundle(registrationID);
-          lokiPreKeyBundleDatabase.setPreKeyBundle(envelope.getSource(), preKeyBundle);
+          lokiPreKeyBundleDatabase.setPreKeyBundle(content.getSender(), preKeyBundle);
+
+          // Loki - If we received a friend request, but we were already friends with this user, then reset the session
+          if (envelope.isFriendRequest()) {
+            long threadID = threadDatabase.getThreadIdIfExistsFor(sender);
+            if (lokiThreadDatabase.getFriendRequestStatus(threadID) == LokiThreadFriendRequestStatus.FRIENDS) {
+              resetSession(content.getSender(), threadID);
+              // Let our other devices know that we have reset the session
+              MessageSender.syncContact(context, sender.getAddress());
+            }
+          }
         }
       }
     }
@@ -1357,21 +1382,40 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
     }
   }
 
+  private SmsMessageRecord getLastMessage(String sender) {
+    try {
+      SmsDatabase smsDatabase = DatabaseFactory.getSmsDatabase(context);
+      Recipient recipient = Recipient.from(context, Address.fromSerialized(sender), false);
+      long threadID = DatabaseFactory.getThreadDatabase(context).getThreadIdIfExistsFor(recipient);
+      if (threadID < 0) { return null; }
+      int messageCount = smsDatabase.getMessageCountForThread(threadID);
+      if (messageCount <= 0) { return null; }
+      long lastMessageID = smsDatabase.getIDForMessageAtIndex(threadID, messageCount - 1);
+      return smsDatabase.getMessage(lastMessageID);
+    } catch (Exception e) {
+      return null;
+    }
+  }
+
   private void handleCorruptMessage(@NonNull String sender, int senderDevice, long timestamp,
                                     @NonNull Optional<Long> smsMessageId)
   {
     SmsDatabase smsDatabase = DatabaseFactory.getSmsDatabase(context);
 
     if (!smsMessageId.isPresent()) {
+      SmsMessageRecord lastMessage = getLastMessage(sender);
+      if (lastMessage == null || !SmsDatabase.Types.isFailedDecryptType(lastMessage.getType())) {
         Optional<InsertResult> insertResult = insertPlaceholder(sender, senderDevice, timestamp);
 
         if (insertResult.isPresent()) {
           smsDatabase.markAsDecryptFailed(insertResult.get().getMessageId());
           MessageNotifier.updateNotification(context, insertResult.get().getThreadId());
         }
+      }
     } else {
       smsDatabase.markAsDecryptFailed(smsMessageId.get());
     }
+    triggerSessionRestorePrompt(sender);
   }
 
   private void handleNoSessionMessage(@NonNull String sender, int senderDevice, long timestamp,
@@ -1380,15 +1424,27 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
     SmsDatabase smsDatabase = DatabaseFactory.getSmsDatabase(context);
 
     if (!smsMessageId.isPresent()) {
+      SmsMessageRecord lastMessage = getLastMessage(sender);
+      if (lastMessage == null || !SmsDatabase.Types.isNoRemoteSessionType(lastMessage.getType())) {
         Optional<InsertResult> insertResult = insertPlaceholder(sender, senderDevice, timestamp);
 
         if (insertResult.isPresent()) {
           smsDatabase.markAsNoSession(insertResult.get().getMessageId());
           MessageNotifier.updateNotification(context, insertResult.get().getThreadId());
         }
+      }
     } else {
       smsDatabase.markAsNoSession(smsMessageId.get());
     }
+    triggerSessionRestorePrompt(sender);
+  }
+
+  private void triggerSessionRestorePrompt(@NonNull String sender) {
+    Recipient primaryRecipient = getPrimaryDeviceRecipient(sender);
+    if (!primaryRecipient.isGroupRecipient()) {
+      long threadID = DatabaseFactory.getThreadDatabase(context).getThreadIdFor(primaryRecipient);
+      DatabaseFactory.getLokiThreadDatabase(context).addSessionRestoreDevice(threadID, sender);
+    }
   }
 
   private void handleLegacyMessage(@NonNull String sender, int senderDevice, long timestamp,
@@ -1779,7 +1835,7 @@ public class PushDecryptJob extends BaseJob implements InjectableType {
   }
 
   private boolean isGroupChatMessage(SignalServiceContent content) {
-    return content.getDataMessage().isPresent() && content.getDataMessage().get().isGroupUpdate();
+    return content.getDataMessage().isPresent() && content.getDataMessage().get().getGroupInfo().isPresent();
   }
 
   private void resetRecipientToPush(@NonNull Recipient recipient) {

src/org/thoughtcrime/securesms/loki/FriendRequestHandler.kt

@@ -26,7 +26,12 @@ object FriendRequestHandler {
         ActionType.Failed -> LokiThreadFriendRequestStatus.NONE
         ActionType.Sent -> LokiThreadFriendRequestStatus.REQUEST_SENT
       }
-      DatabaseFactory.getLokiThreadDatabase(context).setFriendRequestStatus(threadId, threadFriendStatus)
+      val database = DatabaseFactory.getLokiThreadDatabase(context)
+      database.setFriendRequestStatus(threadId, threadFriendStatus)
+      // If we sent a friend request then we need to hide the session restore prompt
+      if (type == ActionType.Sent) {
+        database.removeAllSessionRestoreDevices(threadId)
+      }
     }
 
     // Update message status
@@ -56,6 +61,8 @@ object FriendRequestHandler {
   @JvmStatic
   fun updateLastFriendRequestMessage(context: Context, threadId: Long, status: LokiMessageFriendRequestStatus) {
     if (threadId < 0) { return }
+    val recipient = DatabaseFactory.getThreadDatabase(context).getRecipientForThreadId(threadId) ?: return
+    if (!recipient.address.isPhone) { return }
 
     val messages = DatabaseFactory.getSmsDatabase(context).getAllMessageIDs(threadId)
     val lokiMessageDatabase = DatabaseFactory.getLokiMessageDatabase(context)

src/org/thoughtcrime/securesms/loki/LokiThreadDatabase.kt

@@ -8,11 +8,13 @@ import org.thoughtcrime.securesms.database.Database
 import org.thoughtcrime.securesms.database.DatabaseFactory
 import org.thoughtcrime.securesms.database.helpers.SQLCipherOpenHelper
 import org.thoughtcrime.securesms.recipients.Recipient
+import org.thoughtcrime.securesms.util.TextSecurePreferences
 import org.whispersystems.signalservice.internal.util.JsonUtil
 import org.whispersystems.signalservice.loki.api.LokiPublicChat
 import org.whispersystems.signalservice.loki.messaging.LokiThreadDatabaseProtocol
 import org.whispersystems.signalservice.loki.messaging.LokiThreadFriendRequestStatus
 import org.whispersystems.signalservice.loki.messaging.LokiThreadSessionResetStatus
+import org.whispersystems.signalservice.loki.utilities.PublicKeyValidation
 
 class LokiThreadDatabase(context: Context, helper: SQLCipherOpenHelper) : Database(context, helper), LokiThreadDatabaseProtocol {
     var delegate: LokiThreadDatabaseDelegate? = null
@@ -140,4 +142,26 @@ class LokiThreadDatabase(context: Context, helper: SQLCipherOpenHelper) : Databa
     override fun removePublicChat(threadID: Long) {
         databaseHelper.writableDatabase.delete(publicChatTableName, "${Companion.threadID} = ?", arrayOf( threadID.toString() ))
     }
+
+    // region Session Restore
+    fun addSessionRestoreDevice(threadID: Long, hexEncodedPublicKey: String) {
+        val devices = getSessionRestoreDevices(threadID).toMutableSet()
+        if (devices.add(hexEncodedPublicKey)) {
+            TextSecurePreferences.setStringPreference(context, "session_restore_devices_$threadID", devices.joinToString(","))
+            delegate?.handleSessionRestoreDevicesChanged(threadID)
+        }
+    }
+
+    fun getSessionRestoreDevices(threadID: Long): Set<String> {
+        return TextSecurePreferences.getStringPreference(context, "session_restore_devices_$threadID", "")
+            .split(",")
+            .filter { PublicKeyValidation.isValid(it) }
+            .toSet()
+    }
+
+    fun removeAllSessionRestoreDevices(threadID: Long) {
+        TextSecurePreferences.setStringPreference(context, "session_restore_devices_$threadID", "")
+        delegate?.handleSessionRestoreDevicesChanged(threadID)
+    }
+    // endregion
 }

src/org/thoughtcrime/securesms/loki/LokiThreadDatabaseDelegate.kt

@@ -3,4 +3,5 @@ package org.thoughtcrime.securesms.loki
 interface LokiThreadDatabaseDelegate {
 
     fun handleThreadFriendRequestStatusChanged(threadID: Long)
+    fun handleSessionRestoreDevicesChanged(threadID: Long)
 }

src/org/thoughtcrime/securesms/loki/PushBackgroundMessageSendJob.kt

@@ -15,28 +15,34 @@ import org.whispersystems.signalservice.internal.util.JsonUtil
 import java.io.IOException
 import java.util.concurrent.TimeUnit
 
-data class BackgroundMessage private constructor(val recipient: String, val body: String?, val friendRequest: Boolean, val unpairingRequest: Boolean) {
+data class BackgroundMessage private constructor(val data: Map<String, Any>) {
+
   companion object {
+
     @JvmStatic
-    fun create(recipient: String) = BackgroundMessage(recipient, null, false, false)
+    fun create(recipient: String) = BackgroundMessage(mapOf("recipient" to recipient))
+
     @JvmStatic
-    fun createFriendRequest(recipient: String, messageBody: String) = BackgroundMessage(recipient, messageBody, true, false)
+    fun createFriendRequest(recipient: String, messageBody: String) = BackgroundMessage(mapOf( "recipient" to recipient, "body" to messageBody, "friendRequest" to true ))
+
     @JvmStatic
-    fun createUnpairingRequest(recipient: String) = BackgroundMessage(recipient, null, false, true)
+    fun createUnpairingRequest(recipient: String) = BackgroundMessage(mapOf( "recipient" to recipient, "unpairingRequest" to true ))
+
+    @JvmStatic
+    fun createSessionRestore(recipient: String) = BackgroundMessage(mapOf( "recipient" to recipient, "friendRequest" to true, "sessionRestore" to true ))
             
     internal fun parse(serialized: String): BackgroundMessage {
-      val node = JsonUtil.fromJson(serialized)
+      val data = JsonUtil.fromJson(serialized, Map::class.java) as? Map<String, Any> ?: throw AssertionError("JSON parsing failed")
-      val recipient = node.get("recipient").asText()
+      return BackgroundMessage(data)
-      val body = if (node.hasNonNull("body")) node.get("body").asText() else null
-      val friendRequest = node.get("friendRequest").asBoolean(false)
-      val unpairingRequest = node.get("unpairingRequest").asBoolean(false)
-      return BackgroundMessage(recipient, body, friendRequest, unpairingRequest)
     }
   }
 
+  fun <T> get(key: String, defaultValue: T): T {
+    return data[key] as? T ?: defaultValue
+  }
+
   fun serialize(): String {
-    val map = mapOf("recipient" to recipient, "body" to body, "friendRequest" to friendRequest, "unpairingRequest" to unpairingRequest)
+    return JsonUtil.toJson(data)
-    return JsonUtil.toJson(map)
   }
 }
 
@@ -71,24 +77,31 @@ class PushBackgroundMessageSendJob private constructor(
   }
 
   public override fun onRun() {
+    val recipient = message.get<String?>("recipient", null) ?: throw IllegalStateException()
     val dataMessage = SignalServiceDataMessage.newBuilder()
             .withTimestamp(System.currentTimeMillis())
-            .withBody(message.body)
+            .withBody(message.get<String?>("body", null))
 
-    if (message.friendRequest) {
+    if (message.get("friendRequest", false)) {
-      val bundle = DatabaseFactory.getLokiPreKeyBundleDatabase(context).generatePreKeyBundle(message.recipient)
+      val bundle = DatabaseFactory.getLokiPreKeyBundleDatabase(context).generatePreKeyBundle(recipient)
       dataMessage.withPreKeyBundle(bundle)
               .asFriendRequest(true)
-    } else if (message.unpairingRequest) {
+    }
+
+    if (message.get("unpairingRequest", false)) {
       dataMessage.asUnpairingRequest(true)
     }
 
+    if (message.get("sessionRestore", false)) {
+      dataMessage.asSessionRestore(true)
+    }
+
     val messageSender = ApplicationContext.getInstance(context).communicationModule.provideSignalMessageSender()
-    val address = SignalServiceAddress(message.recipient)
+    val address = SignalServiceAddress(recipient)
     try {
       messageSender.sendMessage(-1, address, Optional.absent<UnidentifiedAccessPair>(), dataMessage.build()) // The message ID doesn't matter
     } catch (e: Exception) {
-      Log.d("Loki", "Failed to send background message to: ${message.recipient}.")
+      Log.d("Loki", "Failed to send background message to: ${recipient}.")
       throw e
     }
   }

src/org/thoughtcrime/securesms/loki/SeedActivity.kt

@@ -206,6 +206,9 @@ class SeedActivity : BaseActionBarActivity(), DeviceLinkingDelegate, ScanListene
         DatabaseFactory.getIdentityDatabase(this).saveIdentity(Address.fromSerialized(userHexEncodedPublicKey), keyPair.publicKey,
             IdentityDatabase.VerifiedStatus.VERIFIED, true, System.currentTimeMillis(), true)
         TextSecurePreferences.setLocalNumber(this, userHexEncodedPublicKey)
+        if (mode == Mode.Restore) {
+            TextSecurePreferences.setRestorationTime(this, System.currentTimeMillis())
+        }
         when (mode) {
             Mode.Register -> Analytics.shared.track("Seed Created")
             Mode.Restore -> Analytics.shared.track("Seed Restored")

src/org/thoughtcrime/securesms/loki/SessionRestoreBannerView.kt

@@ -0,0 +1,40 @@
+package org.thoughtcrime.securesms.loki
+
+import android.content.Context
+import android.util.AttributeSet
+import android.view.LayoutInflater
+import android.view.View
+import android.widget.LinearLayout
+import kotlinx.android.synthetic.main.session_restore_banner.view.*
+
+import network.loki.messenger.R
+import org.thoughtcrime.securesms.recipients.Recipient
+
+class SessionRestoreBannerView : LinearLayout {
+  lateinit var recipient: Recipient
+  var onDismiss: (() -> Unit)? = null
+  var onRestore: (() -> Unit)? = null
+
+  constructor(context: Context) : super(context, null)
+  constructor(context: Context, attrs: AttributeSet?) : super(context, attrs, 0)
+  constructor(context: Context, attrs: AttributeSet?, defStyleAttr: Int) : super(context, attrs, defStyleAttr)
+
+  init {
+    LayoutInflater.from(context).inflate(R.layout.session_restore_banner, this, true)
+    restoreButton.setOnClickListener { onRestore?.invoke() }
+    dismissButton.setOnClickListener { onDismiss?.invoke() }
+  }
+
+  fun update(recipient: Recipient) {
+    this.recipient = recipient
+    messageTextView.text = context.getString(R.string.session_restore_banner_message, recipient.toShortString())
+  }
+
+  fun show() {
+    sessionRestoreBanner.visibility = View.VISIBLE
+  }
+
+  fun hide() {
+    sessionRestoreBanner.visibility = View.GONE
+  }
+}

src/org/thoughtcrime/securesms/loki/redesign/activities/RegisterActivity.kt

@@ -129,6 +129,7 @@ class RegisterActivity : BaseActionBarActivity() {
             IdentityKeyUtil.getIdentityKeyPair(this).publicKey, IdentityDatabase.VerifiedStatus.VERIFIED,
             true, System.currentTimeMillis(), true)
         TextSecurePreferences.setLocalNumber(this, userHexEncodedPublicKey)
+        TextSecurePreferences.setRestorationTime(this, 0)
         TextSecurePreferences.setHasViewedSeed(this, false)
         val intent = Intent(this, DisplayNameActivity::class.java)
         push(intent)

src/org/thoughtcrime/securesms/loki/redesign/activities/RestoreActivity.kt

@@ -87,6 +87,7 @@ class RestoreActivity : BaseActionBarActivity() {
                     IdentityKeyUtil.getIdentityKeyPair(this).publicKey, IdentityDatabase.VerifiedStatus.VERIFIED,
                     true, System.currentTimeMillis(), true)
             TextSecurePreferences.setLocalNumber(this, userHexEncodedPublicKey)
+            TextSecurePreferences.setRestorationTime(this, System.currentTimeMillis())
             TextSecurePreferences.setHasViewedSeed(this, true)
             val intent = Intent(this, DisplayNameActivity::class.java)
             push(intent)

src/org/thoughtcrime/securesms/sms/MessageSender.java

@@ -139,6 +139,10 @@ public class MessageSender {
   public static void sendUnpairRequest(Context context, String contactHexEncodedPublicKey) {
     ApplicationContext.getInstance(context).getJobManager().add(new PushBackgroundMessageSendJob(BackgroundMessage.createUnpairingRequest(contactHexEncodedPublicKey)));
   }
+
+  public static void sendRestoreSessionMessage(Context context, String contactHexEncodedPublicKey) {
+    ApplicationContext.getInstance(context).getJobManager().add(new PushBackgroundMessageSendJob(BackgroundMessage.createSessionRestore(contactHexEncodedPublicKey)));
+  }
   // endregion
 
   public static long send(final Context context,

src/org/thoughtcrime/securesms/util/TextSecurePreferences.java

@@ -1236,6 +1236,14 @@ public class TextSecurePreferences {
   public static boolean needsRevocationCheck(Context context) {
     return getBooleanPreference(context, "needs_revocation", false);
   }
+
+  public static void setRestorationTime(Context context, long time) {
+    setLongPreference(context, "restoration_time", time);
+  }
+
+  public static long getRestorationTime(Context context) {
+    return getLongPreference(context, "restoration_time", 0);
+  }
   // endregion
 
   public static void clearAll(Context context) {