Preserve backups when disabling "Backup my apps"

Ignore AOSP's attempt to wipe backup data when backups are disabled.

Remaining quirks:
* When backups are re-enabled and another backup is started, the system
  will call initializeDevice, and Seedvault will generate a new backup
  salt and start the backup from scratch. This was already the case,
  and this patch does not change that.

Issue: seedvault-app/seedvault#476
Change-Id: I6ab41a885fcf7c4143814ebe849b8263a4f6e595

app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinator.kt

@@ -10,6 +10,7 @@ import android.app.backup.BackupTransport.TRANSPORT_NOT_INITIALIZED
 import android.app.backup.BackupTransport.TRANSPORT_OK
 import android.app.backup.BackupTransport.TRANSPORT_PACKAGE_REJECTED
 import android.app.backup.BackupTransport.TRANSPORT_QUOTA_EXCEEDED
+import android.app.backup.IBackupManager
 import android.app.backup.RestoreSet
 import android.content.Context
 import android.content.pm.PackageInfo
@@ -72,6 +73,7 @@ internal class BackupCoordinator(
     private val metadataManager: MetadataManager,
     private val settingsManager: SettingsManager,
     private val nm: BackupNotificationManager,
+    private val backupManager: IBackupManager,
 ) {
 
     private val state = CoordinatorState(
@@ -115,7 +117,10 @@ internal class BackupCoordinator(
      * @return One of [TRANSPORT_OK] (OK so far) or
      * [TRANSPORT_ERROR] (to retry following network error or other failure).
      */
-    suspend fun initializeDevice(): Int = try {
+    suspend fun initializeDevice(): Int {
+        if (shouldIgnoreBackupManager("initializeDevice")) return TRANSPORT_OK
+
+        return try {
             val token = settingsManager.getToken()
             if (token == null) {
                 Log.i(TAG, "No RestoreSet started, initialization is no-op.")
@@ -134,9 +139,12 @@ internal class BackupCoordinator(
         } catch (e: IOException) {
             Log.e(TAG, "Error initializing device", e)
             // Show error notification if we needed init or were ready for backups
-        if (metadataManager.requiresInit || settingsManager.canDoBackupNow()) nm.onBackupError()
+            if (metadataManager.requiresInit || settingsManager.canDoBackupNow()) {
+                nm.onBackupError()
+            }
             TRANSPORT_ERROR
         }
+    }
 
     fun isAppEligibleForBackup(
         targetPackage: PackageInfo,
@@ -232,6 +240,8 @@ internal class BackupCoordinator(
         data: ParcelFileDescriptor,
         flags: Int,
     ): Int {
+        if (shouldIgnoreBackupManager("performIncrementalBackup")) return TRANSPORT_OK
+
         state.cancelReason = UNKNOWN_ERROR
         if (metadataManager.requiresInit) {
             // start a new restore set to upgrade from legacy format
@@ -282,6 +292,8 @@ internal class BackupCoordinator(
         fileDescriptor: ParcelFileDescriptor,
         flags: Int,
     ): Int {
+        if (shouldIgnoreBackupManager("performFullBackup")) return TRANSPORT_OK
+
         state.cancelReason = UNKNOWN_ERROR
         val token = settingsManager.getToken() ?: error("no token in performFullBackup")
         val salt = metadataManager.salt
@@ -304,6 +316,8 @@ internal class BackupCoordinator(
      * It needs to tear down any ongoing backup state here.
      */
     suspend fun cancelFullBackup() {
+        if (shouldIgnoreBackupManager("cancelFullBackup")) return
+
         val packageInfo = full.getCurrentPackage()
             ?: throw AssertionError("Cancelling full backup, but no current package")
         Log.i(
@@ -359,6 +373,7 @@ internal class BackupCoordinator(
      * @return the same error codes as [performIncrementalBackup] or [performFullBackup].
      */
     suspend fun finishBackup(): Int = when {
+        shouldIgnoreBackupManager("finishBackup") -> TRANSPORT_OK
         kv.hasState() -> {
             check(!full.hasState()) {
                 "K/V backup has state, but full backup has dangling state as well"
@@ -510,4 +525,20 @@ internal class BackupCoordinator(
         return getOutputStream(t, FILE_BACKUP_METADATA)
     }
 
+    /**
+     * Check whether or not backup is enabled, logging a warning if it is not.
+     * When backup is disabled, the system treats this as an opt out and attempts to start
+     * a wipe of backup data. (See frameworks/base/services/backup/java/com/android/server/backup/
+     * UserBackupManagerService.java, lines 3195-3197, tag android-13.0.0_r8.)
+     * This check exists to ensure that backups are not altered when backup is turned off.
+     *
+     * @param methodName the calling method to be included in logging.
+     * @return true if the backup service is disabled, and false if it is not.
+     */
+    private fun shouldIgnoreBackupManager(methodName: String): Boolean =
+        if (!backupManager.isBackupEnabled) {
+            Log.w(TAG, "Ignoring call to $methodName while backup is not enabled")
+            true
+        } else false
+
 }

app/src/main/java/com/stevesoltys/seedvault/transport/backup/BackupModule.kt

@@ -48,7 +48,8 @@ val backupModule = module {
             packageService = get(),
             metadataManager = get(),
             settingsManager = get(),
-            nm = get()
+            nm = get(),
+            backupManager = get(),
         )
     }
 }

app/src/test/java/com/stevesoltys/seedvault/transport/CoordinatorIntegrationTest.kt

@@ -4,6 +4,7 @@ import android.app.backup.BackupDataInput
 import android.app.backup.BackupDataOutput
 import android.app.backup.BackupTransport.NO_MORE_DATA
 import android.app.backup.BackupTransport.TRANSPORT_OK
+import android.app.backup.IBackupManager
 import android.app.backup.RestoreDescription
 import android.app.backup.RestoreDescription.TYPE_FULL_STREAM
 import android.os.ParcelFileDescriptor
@@ -68,6 +69,12 @@ internal class CoordinatorIntegrationTest : TransportTest() {
     private val fullBackup = FullBackup(backupPlugin, settingsManager, inputFactory, cryptoImpl)
     private val apkBackup = mockk<ApkBackup>()
     private val packageService: PackageService = mockk()
+    private val backupManager: IBackupManager = mockk()
+
+    init {
+        every { backupManager.isBackupEnabled } returns true
+    }
+
     private val backup = BackupCoordinator(
         context,
         backupPlugin,
@@ -78,7 +85,8 @@ internal class CoordinatorIntegrationTest : TransportTest() {
         packageService,
         metadataManager,
         settingsManager,
-        notificationManager
+        notificationManager,
+        backupManager,
     )
 
     private val kvRestore = KVRestore(

app/src/test/java/com/stevesoltys/seedvault/transport/backup/BackupCoordinatorTest.kt

@@ -5,6 +5,7 @@ import android.app.backup.BackupTransport.TRANSPORT_NOT_INITIALIZED
 import android.app.backup.BackupTransport.TRANSPORT_OK
 import android.app.backup.BackupTransport.TRANSPORT_PACKAGE_REJECTED
 import android.app.backup.BackupTransport.TRANSPORT_QUOTA_EXCEEDED
+import android.app.backup.IBackupManager
 import android.content.pm.ApplicationInfo.FLAG_STOPPED
 import android.content.pm.PackageInfo
 import android.net.Uri
@@ -48,6 +49,11 @@ internal class BackupCoordinatorTest : BackupTest() {
     private val apkBackup = mockk<ApkBackup>()
     private val packageService: PackageService = mockk()
     private val notificationManager = mockk<BackupNotificationManager>()
+    private val backupManager = mockk<IBackupManager>()
+
+    init {
+        every { backupManager.isBackupEnabled } returns true
+    }
 
     private val backup = BackupCoordinator(
         context,
@@ -59,7 +65,8 @@ internal class BackupCoordinatorTest : BackupTest() {
         packageService,
         metadataManager,
         settingsManager,
-        notificationManager
+        notificationManager,
+        backupManager,
     )
 
     private val metadataOutputStream = mockk<OutputStream>()