StrandHogg detection

vector/build.gradle

@@ -91,6 +91,11 @@ static def getFdroidVersionSuffix() {
     }
 }
 
+static def generateTaskAffinitySuffix() {
+    String charset = (('A'..'Z') + ('a'..'z')).join()
+    return new Random().with { (1..8).collect { charset[nextInt(charset.length())] }.join() }
+}
+
 project.android.buildTypes.all { buildType ->
     buildType.javaCompileOptions.annotationProcessorOptions.arguments =
             [
@@ -131,6 +136,9 @@ android {
         // Required for sonar analysis
         versionName "${versionMajor}.${versionMinor}.${versionPatch}-sonar"
 
+        // Generate a random app task affinity
+        manifestPlaceholders = [appTaskAffinitySuffix:"${generateTaskAffinitySuffix()}"]
+
         buildConfigField "String", "GIT_REVISION", "\"${gitRevision()}\""
         resValue "string", "git_revision", "\"${gitRevision()}\""
 

vector/src/main/AndroidManifest.xml

@@ -84,6 +84,7 @@
         android:roundIcon="@mipmap/ic_launcher_round"
         android:supportsRtl="true"
         android:theme="@style/Theme.Vector.Light"
+        android:taskAffinity="${applicationId}.${appTaskAffinitySuffix}"
         tools:replace="android:allowBackup">
 
         <!-- No limit for screen ratio: avoid black strips -->
@@ -294,7 +295,7 @@
             android:excludeFromRecents="true"
             android:launchMode="singleTask"
             android:supportsPictureInPicture="true"
-            android:taskAffinity=".features.call.VectorCallActivity" />
+            android:taskAffinity=".features.call.VectorCallActivity.${appTaskAffinitySuffix}" />
         <!-- PIP Support https://developer.android.com/guide/topics/ui/picture-in-picture -->
         <activity
             android:name=".features.call.conference.VectorJitsiActivity"

vector/src/main/java/im/vector/app/core/extensions/Activity.kt

@@ -18,6 +18,7 @@ package im.vector.app.core.extensions
 
 import android.app.Activity
 import android.content.Intent
+import android.os.Build
 import android.os.Parcelable
 import android.view.ViewGroup
 import android.view.WindowManager
@@ -29,6 +30,7 @@ import androidx.appcompat.app.AppCompatActivity
 import androidx.fragment.app.Fragment
 import androidx.fragment.app.FragmentTransaction
 import im.vector.app.R
+import timber.log.Timber
 
 fun ComponentActivity.registerStartForActivityResult(onResult: (ActivityResult) -> Unit): ActivityResultLauncher<Intent> {
     return registerForActivityResult(ActivityResultContracts.StartActivityForResult(), onResult)
@@ -114,9 +116,25 @@ fun AppCompatActivity.hideKeyboard() {
     currentFocus?.hideKeyboard()
 }
 
+/**
+ * The current activity must be the root of a task to call onBackPressed, otherwise finish activities with the same task affinity.
+ */
+fun AppCompatActivity.validateBackPressed(onBackPressed: () -> Unit) {
+    if (Build.VERSION.SDK_INT < Build.VERSION_CODES.R && supportFragmentManager.backStackEntryCount == 0) {
+        if (isTaskRoot) {
+            onBackPressed()
+        } else {
+            Timber.e("Application is potentially corrupted by an unknown activity")
+            finishAffinity()
+        }
+    } else {
+        onBackPressed()
+    }
+}
+
 fun Activity.restart() {
-    startActivity(intent)
     finish()
+    startActivity(intent)
 }
 
 fun Activity.keepScreenOn() {

vector/src/main/java/im/vector/app/features/home/HomeActivity.kt

@@ -42,6 +42,7 @@ import im.vector.app.core.extensions.exhaustive
 import im.vector.app.core.extensions.hideKeyboard
 import im.vector.app.core.extensions.registerStartForActivityResult
 import im.vector.app.core.extensions.replaceFragment
+import im.vector.app.core.extensions.validateBackPressed
 import im.vector.app.core.platform.VectorBaseActivity
 import im.vector.app.core.pushers.PushersManager
 import im.vector.app.databinding.ActivityHomeBinding
@@ -515,7 +516,7 @@ class HomeActivity :
         if (views.drawerLayout.isDrawerOpen(GravityCompat.START)) {
             views.drawerLayout.closeDrawer(GravityCompat.START)
         } else {
-            super.onBackPressed()
+            validateBackPressed { super.onBackPressed() }
         }
     }
 

vector/src/main/java/im/vector/app/features/lifecycle/VectorActivityLifecycleCallbacks.kt

@@ -16,31 +16,128 @@
 
 package im.vector.app.features.lifecycle
 
+import android.annotation.SuppressLint
 import android.app.Activity
+import android.app.ActivityManager
 import android.app.Application
+import android.content.ComponentName
+import android.content.pm.ActivityInfo
+import android.content.pm.PackageManager
+import android.os.Build
 import android.os.Bundle
+import androidx.core.content.getSystemService
+import im.vector.app.features.MainActivity
+import im.vector.app.features.MainActivityArgs
 import im.vector.app.features.popup.PopupAlertManager
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.SupervisorJob
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.withContext
+import timber.log.Timber
 
 class VectorActivityLifecycleCallbacks constructor(private val popupAlertManager: PopupAlertManager) : Application.ActivityLifecycleCallbacks {
-    override fun onActivityPaused(activity: Activity) {
-    }
+    /**
+     * The activities information collected from the app manifest.
+     */
+    private var activitiesInfo: Array<ActivityInfo> = emptyArray()
+
+    private val coroutineScope = CoroutineScope(SupervisorJob())
+
+    override fun onActivityPaused(activity: Activity) {}
 
     override fun onActivityResumed(activity: Activity) {
         popupAlertManager.onNewActivityDisplayed(activity)
     }
 
-    override fun onActivityStarted(activity: Activity) {
-    }
+    override fun onActivityStarted(activity: Activity) {}
 
-    override fun onActivityDestroyed(activity: Activity) {
-    }
+    override fun onActivityDestroyed(activity: Activity) {}
 
-    override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {
-    }
+    override fun onActivitySaveInstanceState(activity: Activity, outState: Bundle) {}
 
-    override fun onActivityStopped(activity: Activity) {
-    }
+    override fun onActivityStopped(activity: Activity) {}
 
     override fun onActivityCreated(activity: Activity, savedInstanceState: Bundle?) {
+        // restart the app if the task contains an unknown activity
+        coroutineScope.launch {
+            val isTaskCorrupted = try {
+                isTaskCorrupted(activity)
+            } catch (failure: Throwable) {
+                when (failure) {
+                    // The task was not found. We can ignore it.
+                    is IllegalArgumentException             -> {
+                        Timber.e("The task was not found: ${failure.localizedMessage}")
+                        false
+                    }
+                    is PackageManager.NameNotFoundException -> {
+                        Timber.e("Package manager error: ${failure.localizedMessage}")
+                        true
+                    }
+                    else                                    -> throw failure
+                }
+            }
+
+            if (isTaskCorrupted) {
+                Timber.e("Application is potentially corrupted by an unknown activity")
+                MainActivity.restartApp(activity, MainActivityArgs())
+                return@launch
+            }
+        }
     }
+
+    /**
+     * Check if all activities running on the task with package name affinity are safe.
+     *
+     * @return true if an app task is corrupted by a potentially malicious activity
+     */
+    @SuppressLint("NewApi")
+    @Suppress("DEPRECATION")
+    private suspend fun isTaskCorrupted(activity: Activity): Boolean = withContext(Dispatchers.Default) {
+        val context = activity.applicationContext
+        val packageManager: PackageManager = context.packageManager
+
+        // Get all activities from app manifest
+        if (activitiesInfo.isEmpty()) {
+            activitiesInfo = packageManager.getPackageInfo(context.packageName, PackageManager.GET_ACTIVITIES).activities
+        }
+
+        // Get all running activities on app task
+        // and compare to activities declared in manifest
+        val manager = context.getSystemService<ActivityManager>() ?: return@withContext false
+
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
+            // Android lint may return an error on topActivity field.
+            // This field was added in ActivityManager.RecentTaskInfo class since Android M (API level 23)
+            // and it is inherited from TaskInfo since Android Q (API level 29).
+            // API 23 changes : https://developer.android.com/sdk/api_diff/23/changes/android.app.ActivityManager.RecentTaskInfo
+            // API 29 changes : https://developer.android.com/sdk/api_diff/29/changes/android.app.ActivityManager.RecentTaskInfo
+            manager.appTasks.any { appTask ->
+                appTask.taskInfo.topActivity?.let { isPotentialMaliciousActivity(it) } ?: false
+            }
+        } else {
+            // Android lint may return an error on topActivity field.
+            // This was present in ActivityManager.RunningTaskInfo class since API level 1!
+            // and it is inherited from TaskInfo since Android Q (API level 29).
+            // API 29 changes : https://developer.android.com/sdk/api_diff/29/changes/android.app.ActivityManager.RunningTaskInfo
+            manager.getRunningTasks(10).any { runningTaskInfo ->
+                runningTaskInfo.topActivity?.let {
+                    // Check whether the activity task affinity matches with app task affinity.
+                    // The activity is considered safe when its task affinity doesn't correspond to app task affinity.
+                    if (packageManager.getActivityInfo(it, 0).taskAffinity == context.applicationInfo.taskAffinity) {
+                        isPotentialMaliciousActivity(it)
+                    } else false
+                } ?: false
+            }
+        }
+    }
+
+    /**
+     * Detect potential malicious activity.
+     * Check if the activity running in app task is declared in app manifest.
+     *
+     * @param activity      the activity of the task
+     * @return true if the activity is potentially malicious
+     */
+    private fun isPotentialMaliciousActivity(activity: ComponentName): Boolean = activitiesInfo.none { it.name == activity.className }
 }

vector/src/main/java/im/vector/app/features/login/LoginActivity.kt

@@ -36,6 +36,7 @@ import im.vector.app.core.extensions.POP_BACK_STACK_EXCLUSIVE
 import im.vector.app.core.extensions.addFragment
 import im.vector.app.core.extensions.addFragmentToBackstack
 import im.vector.app.core.extensions.exhaustive
+import im.vector.app.core.extensions.validateBackPressed
 import im.vector.app.core.platform.VectorBaseActivity
 import im.vector.app.databinding.ActivityLoginBinding
 import im.vector.app.features.analytics.plan.MobileScreen
@@ -279,6 +280,10 @@ open class LoginActivity : VectorBaseActivity<ActivityLoginBinding>(), UnlockedA
                 ?.let { loginViewModel.handle(LoginAction.LoginWithToken(it)) }
     }
 
+    override fun onBackPressed() {
+        validateBackPressed { super.onBackPressed() }
+    }
+
     private fun onRegistrationStageNotSupported() {
         MaterialAlertDialogBuilder(this)
                 .setTitle(R.string.app_name)

vector/src/main/java/im/vector/app/features/onboarding/OnboardingActivity.kt

@@ -21,6 +21,7 @@ import android.content.Intent
 import android.net.Uri
 import dagger.hilt.android.AndroidEntryPoint
 import im.vector.app.core.extensions.lazyViewModel
+import im.vector.app.core.extensions.validateBackPressed
 import im.vector.app.core.platform.VectorBaseActivity
 import im.vector.app.core.platform.lifecycleAwareLazy
 import im.vector.app.databinding.ActivityLoginBinding
@@ -46,6 +47,10 @@ class OnboardingActivity : VectorBaseActivity<ActivityLoginBinding>(), UnlockedA
         onboardingVariant.onNewIntent(intent)
     }
 
+    override fun onBackPressed() {
+        validateBackPressed { super.onBackPressed() }
+    }
+
     override fun initUiAndData() {
         onboardingVariant.initUiAndData(isFirstCreation())
     }