Dynamically generate component names at runtime

app/src/main/java/com/topjohnwu/magisk/core/base/BaseActivity.kt

@@ -34,9 +34,11 @@ abstract class BaseActivity : AppCompatActivity() {
         permissionCallback?.invoke(it)
         permissionCallback = null
     }
+
+    private var installCallback: ((Boolean) -> Unit)? = null
     private val requestInstall = registerForActivityResult(RequestInstall()) {
-        permissionCallback?.invoke(it)
-        permissionCallback = null
+        installCallback?.invoke(it)
+        installCallback = null
     }
 
     private var contentCallback: ContentResultCallback? = null
@@ -93,10 +95,11 @@ abstract class BaseActivity : AppCompatActivity() {
             callback(true)
             return
         }
-        permissionCallback = callback
         if (permission == REQUEST_INSTALL_PACKAGES) {
+            installCallback = callback
             requestInstall.launch(Unit)
         } else {
+            permissionCallback = callback
             requestPermission.launch(permission)
         }
     }

app/src/main/java/com/topjohnwu/magisk/core/download/DownloadService.kt

@@ -101,15 +101,9 @@ class DownloadService : NotificationService() {
                     zf.getInputStream(zf.getEntry("assets/stub.apk")).writeTo(apk)
 
                     // Patch and install
-                    val session = APKInstall.startSession(this)
-                    session.openStream(this).use {
-                        val label = applicationInfo.nonLocalizedLabel
-                        if (!HideAPK.patch(this, apk, it, packageName, label)) {
-                            throw IOException("HideAPK patch error")
-                        }
-                    }
+                    subject.intent = HideAPK.upgrade(this, apk) ?:
+                        throw IOException("HideAPK patch error")
                     apk.delete()
-                    subject.intent = session.waitIntent()
                 } else {
                     ActivityTracker.foreground?.let {
                         // Relaunch the process if we are foreground

app/src/main/java/com/topjohnwu/magisk/core/tasks/HideAPK.kt

@@ -4,6 +4,7 @@ import android.app.Activity
 import android.content.Context
 import android.content.Intent
 import android.widget.Toast
+import androidx.annotation.WorkerThread
 import com.topjohnwu.magisk.BuildConfig.APPLICATION_ID
 import com.topjohnwu.magisk.R
 import com.topjohnwu.magisk.StubApk
@@ -28,6 +29,7 @@ import java.io.FileOutputStream
 import java.io.IOException
 import java.io.OutputStream
 import java.security.SecureRandom
+import kotlin.random.asKotlinRandom
 
 object HideAPK {
 
@@ -37,6 +39,7 @@ object HideAPK {
 
     // Some arbitrary limit
     const val MAX_LABEL_LENGTH = 32
+    const val PLACEHOLDER = "COMPONENT_PLACEHOLDER"
 
     private fun genPackageName(): String {
         val random = SecureRandom()
@@ -61,7 +64,61 @@ object HideAPK {
         return builder.toString()
     }
 
-    fun patch(
+    private fun classNameGenerator() = sequence {
+        val c1 = mutableListOf<String>()
+        val c2 = mutableListOf<String>()
+        val c3 = mutableListOf<String>()
+        val random = SecureRandom()
+        val kRandom = random.asKotlinRandom()
+
+        fun <T> chain(vararg iters: Iterable<T>) = sequence {
+            iters.forEach { it.forEach { v -> yield(v) } }
+        }
+
+        for (a in chain('a'..'z', 'A'..'Z')) {
+            if (a != 'a' && a != 'A') {
+                c1.add("$a")
+            }
+            for (b in chain('a'..'z', 'A'..'Z', '0'..'9')) {
+                c2.add("$a$b")
+                for (c in chain('a'..'z', 'A'..'Z', '0'..'9')) {
+                    c3.add("$a$b$c")
+                }
+            }
+        }
+
+        c1.shuffle(random)
+        c2.shuffle(random)
+        c3.shuffle(random)
+
+        fun notJavaKeyword(name: String) = when (name) {
+            "do", "if", "for", "int", "new", "try" -> false
+            else -> true
+        }
+
+        fun List<String>.process() = asSequence().filter(::notJavaKeyword)
+
+        val names = mutableListOf<String>()
+        names.addAll(c1)
+        names.addAll(c2.process().take(30))
+        names.addAll(c3.process().take(30))
+
+        while (true) {
+            val seg = 2 + random.nextInt(4)
+            val cls = StringBuilder()
+            for (i in 0 until seg) {
+                cls.append(names.random(kRandom))
+                if (i != seg - 1)
+                    cls.append('.')
+            }
+            // Old Android does not support capitalized package names
+            // Check Android 7.0.0 PackageParser#buildClassName
+            cls[0] = cls[0].lowercaseChar()
+            yield(cls.toString())
+        }
+    }.distinct().iterator()
+
+    private fun patch(
         context: Context,
         apk: File, out: OutputStream,
         pkg: String, label: CharSequence
@@ -72,12 +129,15 @@ object HideAPK {
             JarMap.open(apk, true).use { jar ->
                 val je = jar.getJarEntry(ANDROID_MANIFEST)
                 val xml = AXML(jar.getRawData(je))
+                val generator = classNameGenerator()
 
                 if (!xml.patchStrings {
                     for (i in it.indices) {
                         val s = it[i]
                         if (s.contains(APPLICATION_ID)) {
                             it[i] = s.replace(APPLICATION_ID, pkg)
+                        } else if (s.contains(PLACEHOLDER)) {
+                            it[i] = generator.next()
                         } else if (s == origLabel) {
                             it[i] = label.toString()
                         }
@@ -193,4 +253,17 @@ object HideAPK {
         }
         if (!success) onFailure.run()
     }
+
+    @WorkerThread
+    fun upgrade(context: Context, apk: File): Intent? {
+        val label = context.applicationInfo.nonLocalizedLabel
+        val pkg = context.packageName
+        val session = APKInstall.startSession(context)
+        session.openStream(context).use {
+            if (!patch(context, apk, it, pkg, label)) {
+                return null
+            }
+        }
+        return session.waitIntent()
+    }
 }

app/src/main/java/com/topjohnwu/magisk/ui/MainActivity.kt

@@ -12,6 +12,7 @@ import androidx.core.content.pm.ShortcutManagerCompat
 import androidx.core.view.forEach
 import androidx.core.view.isGone
 import androidx.core.view.isVisible
+import androidx.lifecycle.lifecycleScope
 import androidx.navigation.NavDirections
 import com.topjohnwu.magisk.MainDirections
 import com.topjohnwu.magisk.R
@@ -22,12 +23,15 @@ import com.topjohnwu.magisk.core.Const
 import com.topjohnwu.magisk.core.Info
 import com.topjohnwu.magisk.core.isRunningAsStub
 import com.topjohnwu.magisk.core.model.module.LocalModule
+import com.topjohnwu.magisk.core.tasks.HideAPK
 import com.topjohnwu.magisk.databinding.ActivityMainMd2Binding
 import com.topjohnwu.magisk.ktx.startAnimations
 import com.topjohnwu.magisk.ui.home.HomeFragmentDirections
 import com.topjohnwu.magisk.utils.Utils
 import com.topjohnwu.magisk.view.MagiskDialog
 import com.topjohnwu.magisk.view.Shortcuts
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
 import java.io.File
 
 class MainViewModel : BaseViewModel()
@@ -59,6 +63,7 @@ class MainActivity : SplashActivity<ActivityMainMd2Binding>() {
         setContentView()
         showUnsupportedMessage()
         askForHomeShortcut()
+        checkStubComponent()
 
         // Ask permission to post notifications for background update check
         if (Config.checkUpdate) {
@@ -227,4 +232,22 @@ class MainActivity : SplashActivity<ActivityMainMd2Binding>() {
             }.show()
         }
     }
+
+    @SuppressLint("InlinedApi")
+    private fun checkStubComponent() {
+        if (intent.component?.className?.contains(HideAPK.PLACEHOLDER) == true) {
+            // The stub APK was not properly patched, re-apply our changes
+            withPermission(Manifest.permission.REQUEST_INSTALL_PACKAGES) { granted ->
+                if (granted) {
+                    lifecycleScope.launch(Dispatchers.IO) {
+                        val apk = File(applicationInfo.sourceDir)
+                        HideAPK.upgrade(this@MainActivity, apk)?.let {
+                            startActivity(it)
+                        }
+                    }
+                }
+            }
+        }
+    }
+
 }