Fix downgrade wallpaper restore bug

Add a check in TarBackupReader to enable the restore of packages in the V_To_U_Allowlist in the V to U downgrade scenario

Bug: 341732443
Test: atest -v TarBackupReaderTest, manual test (details: https://b.corp.google.com/issues/341732443#comment18)
Change-Id: I12a1f272b17a12abb532a98c0d93f0a9854fcb51

3 files changed, 199 insertions, 4 deletions

diff --git a/services/backup/java/com/android/server/backup/restore/FullRestoreEngine.java b/services/backup/java/com/android/server/backup/restore/FullRestoreEngine.java
index b414b252cc37..2d99c96452da 100644
--- a/services/backup/java/com/android/server/backup/restore/FullRestoreEngine.java
+++ b/services/backup/java/com/android/server/backup/restore/FullRestoreEngine.java
@@ -270,7 +270,8 @@ public class FullRestoreEngine extends RestoreEngine {
                             PackageManagerInternal.class);
                     RestorePolicy restorePolicy = tarBackupReader.chooseRestorePolicy(
                             mBackupManagerService.getPackageManager(), allowApks, info, signatures,
-                            pmi, mUserId, mBackupEligibilityRules);
+                            pmi, mUserId, mBackupEligibilityRules,
+                            mBackupManagerService.getContext());
                     mManifestSignatures.put(info.packageName, signatures);
                     mPackagePolicies.put(pkg, restorePolicy);
                     mPackageInstallers.put(pkg, info.installerPackageName);
diff --git a/services/backup/java/com/android/server/backup/utils/TarBackupReader.java b/services/backup/java/com/android/server/backup/utils/TarBackupReader.java
index 78a9952d066d..4860a274cfa8 100644
--- a/services/backup/java/com/android/server/backup/utils/TarBackupReader.java
+++ b/services/backup/java/com/android/server/backup/utils/TarBackupReader.java
@@ -31,6 +31,7 @@ import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_FULL_RESTORE_
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_MISSING_SIGNATURE;
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_RESTORE_ANY_VERSION;
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_SYSTEM_APP_NO_AGENT;
+import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_V_TO_U_RESTORE_PKG_ELIGIBLE;
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_VERSIONS_MATCH;
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_VERSION_OF_BACKUP_OLDER;
 
@@ -53,17 +54,22 @@ import android.content.pm.PackageInfo;
 import android.content.pm.PackageManager;
 import android.content.pm.PackageManagerInternal;
 import android.content.pm.Signature;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.UserHandle;
+import android.provider.Settings;
 import android.util.Slog;
 
 import com.android.server.backup.FileMetadata;
+import com.android.server.backup.Flags;
 import com.android.server.backup.restore.RestorePolicy;
 
 import java.io.ByteArrayInputStream;
 import java.io.DataInputStream;
 import java.io.IOException;
 import java.io.InputStream;
+import java.util.Arrays;
+import java.util.List;
 
 /**
  * Utility methods to read backup tar file.
@@ -390,7 +396,7 @@ public class TarBackupReader {
             boolean allowApks, FileMetadata info, Signature[] signatures,
             PackageManagerInternal pmi, int userId, Context context) {
         return chooseRestorePolicy(packageManager, allowApks, info, signatures, pmi, userId,
-                BackupEligibilityRules.forBackup(packageManager, pmi, userId, context));
+                BackupEligibilityRules.forBackup(packageManager, pmi, userId, context), context);
     }
 
     /**
@@ -406,7 +412,8 @@ public class TarBackupReader {
      */
     public RestorePolicy chooseRestorePolicy(PackageManager packageManager,
             boolean allowApks, FileMetadata info, Signature[] signatures,
-            PackageManagerInternal pmi, int userId, BackupEligibilityRules eligibilityRules) {
+            PackageManagerInternal pmi, int userId, BackupEligibilityRules eligibilityRules,
+            Context context) {
         if (signatures == null) {
             return RestorePolicy.IGNORE;
         }
@@ -448,6 +455,16 @@ public class TarBackupReader {
                                     pkgInfo,
                                     LOG_EVENT_CATEGORY_BACKUP_MANAGER_POLICY,
                                     null);
+                        } else if (isAllowlistedForVToURestore(info, pkgInfo, userId, context)) {
+                            Slog.i(TAG, "Performing a V to U downgrade; package: "
+                                            + info.packageName
+                                            + " is allowlisted");
+                            policy = RestorePolicy.ACCEPT;
+                            mBackupManagerMonitorEventSender.monitorEvent(
+                                    LOG_EVENT_ID_V_TO_U_RESTORE_PKG_ELIGIBLE,
+                                    pkgInfo,
+                                    LOG_EVENT_CATEGORY_BACKUP_MANAGER_POLICY,
+                                    null);
                         } else {
                             // The data is from a newer version of the app than
                             // is presently installed.  That means we can only
@@ -751,6 +768,36 @@ public class TarBackupReader {
         return true;
     }
 
+    // checks the sdk of the target/source device for a B&R operation.
+    // system components can opt in of V->U restore via allowlist.
+    @SuppressWarnings("AndroidFrameworkCompatChange")
+    private boolean isAllowlistedForVToURestore(FileMetadata backupFileInfo,
+            PackageInfo installedPackageInfo,
+            int userId, Context context) {
+        // We assume that the package version matches the sdk (e.g. version 35 means V).
+        // This is true for most of the system components ( and it is specifically true for those
+        // that are in the allowlist)
+        // In order to check if this is a V to U transfer we check if the package version from the
+        // backup is 35 and on the target is 34.
+        // We don't need to check the  V to U denylist here since a package can only make it
+        // to TarBackupReader if allowed and not denied (from PerformUnifiedRestoreTask)
+
+        String vToUAllowlist = getVToUAllowlist(context, userId);
+        List<String> mVToUAllowlist = Arrays.asList(vToUAllowlist.split(","));
+        return Flags.enableVToURestoreForSystemComponentsInAllowlist()
+                && (installedPackageInfo.getLongVersionCode()
+                == Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
+                && (backupFileInfo.version > Build.VERSION_CODES.UPSIDE_DOWN_CAKE)
+                && (mVToUAllowlist.contains(installedPackageInfo.packageName));
+    }
+
+    private String getVToUAllowlist(Context context, int userId) {
+        return Settings.Secure.getStringForUser(
+                context.getContentResolver(),
+                Settings.Secure.V_TO_U_RESTORE_ALLOWLIST,
+                userId);
+    }
+
     private static long extractRadix(byte[] data, int offset, int maxChars, int radix)
             throws IOException {
         long value = 0;
diff --git a/services/tests/mockingservicestests/src/com/android/server/backup/utils/TarBackupReaderTest.java b/services/tests/mockingservicestests/src/com/android/server/backup/utils/TarBackupReaderTest.java
index 33995653870e..396f4da75172 100644
--- a/services/tests/mockingservicestests/src/com/android/server/backup/utils/TarBackupReaderTest.java
+++ b/services/tests/mockingservicestests/src/com/android/server/backup/utils/TarBackupReaderTest.java
@@ -25,6 +25,7 @@ import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_RESTORE_ANY_V
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_SYSTEM_APP_NO_AGENT;
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_VERSIONS_MATCH;
 import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_VERSION_OF_BACKUP_OLDER;
+import static android.app.backup.BackupManagerMonitor.LOG_EVENT_ID_V_TO_U_RESTORE_PKG_ELIGIBLE;
 
 import static com.google.common.truth.Truth.assertThat;
 
@@ -42,17 +43,23 @@ import android.content.pm.PackageManagerInternal;
 import android.content.pm.Signature;
 import android.content.pm.SigningDetails;
 import android.content.pm.SigningInfo;
+import android.os.Build;
 import android.os.Bundle;
 import android.os.Process;
 import android.os.UserHandle;
 import android.platform.test.annotations.Presubmit;
+import android.platform.test.flag.junit.SetFlagsRule;
+import android.provider.Settings;
+import android.testing.TestableContext;
 
 import androidx.test.InstrumentationRegistry;
+import androidx.test.core.app.ApplicationProvider;
 import androidx.test.filters.SmallTest;
 import androidx.test.runner.AndroidJUnit4;
 
 import com.android.frameworks.mockingservicestests.R;
 import com.android.server.backup.FileMetadata;
+import com.android.server.backup.Flags;
 import com.android.server.backup.UserBackupManagerService;
 import com.android.server.backup.restore.PerformAdbRestoreTask;
 import com.android.server.backup.restore.RestorePolicy;
@@ -61,6 +68,7 @@ import com.android.server.backup.testutils.PackageManagerStub;
 import com.google.common.hash.Hashing;
 
 import org.junit.Before;
+import org.junit.Rule;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.ArgumentCaptor;
@@ -86,6 +94,8 @@ public class TarBackupReaderTest {
     @Mock private BytesReadListener mBytesReadListenerMock;
     @Mock private IBackupManagerMonitor mBackupManagerMonitorMock;
     @Mock private PackageManagerInternal mMockPackageManagerInternal;
+    @Rule
+    public final SetFlagsRule mSetFlagsRule = new SetFlagsRule();
 
     private final PackageManagerStub mPackageManagerStub = new PackageManagerStub();
     private Context mContext;
@@ -95,7 +105,7 @@ public class TarBackupReaderTest {
     public void setUp() throws Exception {
         MockitoAnnotations.initMocks(this);
 
-        mContext = InstrumentationRegistry.getContext();
+        mContext = new TestableContext(ApplicationProvider.getApplicationContext());
         mUserId = UserHandle.USER_SYSTEM;
     }
 
@@ -515,6 +525,107 @@ public class TarBackupReaderTest {
 
     @Test
     public void
+    chooseRestorePolicy_flagOnNotRestoreAnyVersionVToURestoreAndInAllowlist_returnsIgnore()
+            throws Exception {
+
+        mSetFlagsRule.enableFlags(
+                Flags.FLAG_ENABLE_V_TO_U_RESTORE_FOR_SYSTEM_COMPONENTS_IN_ALLOWLIST);
+
+        TarBackupReader tarBackupReader = createTarBackupReader();
+
+        Settings.Secure.putString(mContext.getContentResolver(),
+                Settings.Secure.V_TO_U_RESTORE_ALLOWLIST, "test");
+
+        Signature[] signatures = new Signature[]{FAKE_SIGNATURE_1};
+        FileMetadata info = new FileMetadata();
+        info.version = Build.VERSION_CODES.UPSIDE_DOWN_CAKE + 1;
+
+        PackageInfo packageInfo = createNonRestoreAnyVersionUPackage();
+        PackageManagerStub.sPackageInfo = packageInfo;
+
+        doReturn(true).when(mMockPackageManagerInternal).isDataRestoreSafe(FAKE_SIGNATURE_1,
+                packageInfo.packageName);
+        RestorePolicy policy = tarBackupReader.chooseRestorePolicy(mPackageManagerStub,
+                false /* allowApks */, info, signatures, mMockPackageManagerInternal,
+                mUserId, mContext);
+
+        assertThat(policy).isEqualTo(RestorePolicy.ACCEPT);
+        ArgumentCaptor<Bundle> bundleCaptor = ArgumentCaptor.forClass(Bundle.class);
+        verify(mBackupManagerMonitorMock).onEvent(bundleCaptor.capture());
+        assertThat(bundleCaptor.getValue().get(EXTRA_LOG_EVENT_ID)).isEqualTo(
+                LOG_EVENT_ID_V_TO_U_RESTORE_PKG_ELIGIBLE);
+    }
+
+
+    @Test
+    public void
+    chooseRestorePolicy_flagOffNotRestoreAnyVersionVToURestoreAndInAllowlist_returnsAccept()
+            throws Exception {
+
+        mSetFlagsRule.disableFlags(
+                Flags.FLAG_ENABLE_V_TO_U_RESTORE_FOR_SYSTEM_COMPONENTS_IN_ALLOWLIST);
+
+        TarBackupReader tarBackupReader = createTarBackupReader();
+
+        Settings.Secure.putString(mContext.getContentResolver(),
+                Settings.Secure.V_TO_U_RESTORE_ALLOWLIST, "test");
+
+        Signature[] signatures = new Signature[]{FAKE_SIGNATURE_1};
+        FileMetadata info = new FileMetadata();
+        info.version = Build.VERSION_CODES.UPSIDE_DOWN_CAKE + 1;
+
+        PackageInfo packageInfo = createNonRestoreAnyVersionUPackage();
+        PackageManagerStub.sPackageInfo = packageInfo;
+
+        doReturn(true).when(mMockPackageManagerInternal).isDataRestoreSafe(FAKE_SIGNATURE_1,
+                packageInfo.packageName);
+        RestorePolicy policy = tarBackupReader.chooseRestorePolicy(mPackageManagerStub,
+                false /* allowApks */, info, signatures, mMockPackageManagerInternal,
+                mUserId, mContext);
+
+        assertThat(policy).isEqualTo(RestorePolicy.IGNORE);
+        ArgumentCaptor<Bundle> bundleCaptor = ArgumentCaptor.forClass(Bundle.class);
+        verify(mBackupManagerMonitorMock).onEvent(bundleCaptor.capture());
+        assertThat(bundleCaptor.getValue().get(EXTRA_LOG_EVENT_ID)).isEqualTo(
+                LOG_EVENT_ID_VERSION_OF_BACKUP_OLDER);
+
+    }
+
+    @Test
+    public void
+    chooseRestorePolicy_flagOnNotRestoreAnyVersionVToURestoreAndNotInAllowlist_returnsIgnore()
+            throws Exception {
+
+        mSetFlagsRule.enableFlags(
+                Flags.FLAG_ENABLE_V_TO_U_RESTORE_FOR_SYSTEM_COMPONENTS_IN_ALLOWLIST);
+
+        TarBackupReader tarBackupReader = createTarBackupReader();
+
+        Settings.Secure.putString(mContext.getContentResolver(),
+                Settings.Secure.V_TO_U_RESTORE_ALLOWLIST, "pkg");
+
+        Signature[] signatures = new Signature[]{FAKE_SIGNATURE_1};
+        FileMetadata info = new FileMetadata();
+        info.version = Build.VERSION_CODES.UPSIDE_DOWN_CAKE + 1;
+
+        PackageInfo packageInfo = createNonRestoreAnyVersionUPackage();
+        PackageManagerStub.sPackageInfo = packageInfo;
+
+        doReturn(true).when(mMockPackageManagerInternal).isDataRestoreSafe(FAKE_SIGNATURE_1,
+                packageInfo.packageName);
+        RestorePolicy policy = tarBackupReader.chooseRestorePolicy(mPackageManagerStub,
+                false /* allowApks */, info, signatures, mMockPackageManagerInternal,
+                mUserId, mContext);
+
+        assertThat(policy).isEqualTo(RestorePolicy.IGNORE);
+        ArgumentCaptor<Bundle> bundleCaptor = ArgumentCaptor.forClass(Bundle.class);
+        verify(mBackupManagerMonitorMock).onEvent(bundleCaptor.capture());
+        assertThat(bundleCaptor.getValue().get(EXTRA_LOG_EVENT_ID)).isEqualTo(
+                LOG_EVENT_ID_VERSION_OF_BACKUP_OLDER);
+    }
+
+    @Test
+    public void
     chooseRestorePolicy_notRestoreAnyVersionAndVersionMismatchButAllowApksAndHasApk_returnsAcceptIfApk()
             throws Exception {
         InputStream inputStream = mContext.getResources().openRawResource(
@@ -523,6 +634,10 @@ public class TarBackupReaderTest {
                 inputStream, null);
         TarBackupReader tarBackupReader = new TarBackupReader(tarInputStream,
                 mBytesReadListenerMock, mBackupManagerMonitorMock);
+
+        Settings.Secure.putString(mContext.getContentResolver(),
+                Settings.Secure.V_TO_U_RESTORE_ALLOWLIST, "pkg");
+
         Signature[] signatures = new Signature[]{FAKE_SIGNATURE_1};
         FileMetadata info = new FileMetadata();
         info.version = 2;
@@ -564,6 +679,10 @@ public class TarBackupReaderTest {
                 inputStream, null);
         TarBackupReader tarBackupReader = new TarBackupReader(tarInputStream,
                 mBytesReadListenerMock, mBackupManagerMonitorMock);
+
+        Settings.Secure.putString(mContext.getContentResolver(),
+                Settings.Secure.V_TO_U_RESTORE_ALLOWLIST, "pkg");
+
         Signature[] signatures = new Signature[]{FAKE_SIGNATURE_1};
         FileMetadata info = new FileMetadata();
         info.version = 2;
@@ -596,5 +715,33 @@ public class TarBackupReaderTest {
         assertThat(bundleCaptor.getValue().get(EXTRA_LOG_EVENT_ID)).isEqualTo(
                 LOG_EVENT_ID_VERSION_OF_BACKUP_OLDER);
     }
+
+    private TarBackupReader createTarBackupReader() throws Exception {
+        InputStream inputStream = mContext.getResources().openRawResource(
+                R.raw.backup_telephony_no_password);
+        InputStream tarInputStream = PerformAdbRestoreTask.parseBackupFileHeaderAndReturnTarStream(
+                inputStream, null);
+        TarBackupReader tarBackupReader = new TarBackupReader(tarInputStream,
+                mBytesReadListenerMock, mBackupManagerMonitorMock);
+        return tarBackupReader;
+    }
+
+    private PackageInfo createNonRestoreAnyVersionUPackage(){
+        PackageInfo packageInfo = new PackageInfo();
+        packageInfo.packageName = "test";
+        packageInfo.applicationInfo = new ApplicationInfo();
+        packageInfo.applicationInfo.flags |= ApplicationInfo.FLAG_ALLOW_BACKUP;
+        packageInfo.applicationInfo.flags &= ~ApplicationInfo.FLAG_RESTORE_ANY_VERSION;
+        packageInfo.applicationInfo.uid = Process.FIRST_APPLICATION_UID;
+        packageInfo.applicationInfo.backupAgentName = null;
+        packageInfo.signingInfo = new SigningInfo(
+                new SigningDetails(
+                        new Signature[]{FAKE_SIGNATURE_1},
+                        SigningDetails.SignatureSchemeVersion.SIGNING_BLOCK_V3,
+                        null,
+                        null));
+        packageInfo.versionCode = Build.VERSION_CODES.UPSIDE_DOWN_CAKE;
+        return packageInfo;
+    }
 }