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Commit 1a67da88 authored by Joël Stemmer's avatar Joël Stemmer
Browse files

Avoid entering an infinite loop in PackageManagerBackupAgent#onRestore 

When the PackageManagerBackupAgent restores an old backup that does not
have an ancestral record version and the backup contains a package that
does not have any signatures it will enter an infinite loop. This
happens because it calls `continue` without reading the next key/value
pair in the backup.

Test: atest PackageManagerBackupAgentTest
Bug: 330708733
Change-Id: Ifb71293b75ccb68dc7e721593f04128417360491
parent 0c43ad7b

services/backup/java/com/android/server/backup/PackageManagerBackupAgent.java

+8 −8
Original line number Original line Diff line number Diff line
@@ -781,6 +781,9 @@ public class PackageManagerBackupAgent extends BackupAgent { 
                                "Not restoring package "

                                "Not restoring package "

                                        + key

                                        + key

                                        + " since it appears to have no signatures.");

                                        + " since it appears to have no signatures.");

                        if (!data.readNextHeader()) {

                            break;

                        }

                        continue;

                        continue;

                    }

                    }
@@ -790,18 +793,15 @@ public class PackageManagerBackupAgent extends BackupAgent { 
                    sigMap.put(key, new Metadata(versionCode, sigs));

                    sigMap.put(key, new Metadata(versionCode, sigs));

                }

                }





                boolean readNextHeader = data.readNextHeader();

                if (!data.readNextHeader()) {

                if (!readNextHeader) {

                    if (DEBUG) {

                        Slog.v(

                                TAG,

                                "LegacyRestoreDataConsumer:"

                                        + " we're done reading all the headers");

                    }

                    break;

                    break;

                }

                }

            }

            }





            if (DEBUG) {

                Slog.v(TAG, "LegacyRestoreDataConsumer:" + " we're done reading all the headers");

            }



            // On successful completion, cache the signature map for the Backup Manager to use

            // On successful completion, cache the signature map for the Backup Manager to use

            mRestoredSignatures = sigMap;

            mRestoredSignatures = sigMap;

        }

        }

services/tests/mockingservicestests/src/com/android/server/backup/PackageManagerBackupAgentTest.java

+24 −0
Original line number Original line Diff line number Diff line
@@ -211,6 +211,30 @@ public class PackageManagerBackupAgentTest { 
        assertThat(mNewState.length()).isEqualTo(0);

        assertThat(mNewState.length()).isEqualTo(0);

    }

    }





    @Test

    public void onRestore_legacyBackupWithMissingSignature_restoresBackup() throws Exception {

        PackageInfo pkgWithoutSigs = createPackage("pkg.no.sigs", 1);

        pkgWithoutSigs.signingInfo =

                new SigningInfo(new SigningDetails(new Signature[0], 1, null, null));

        when(mPackageManager.getPackageInfoAsUser(

                        eq(pkgWithoutSigs.packageName), anyInt(), anyInt()))

                .thenReturn(pkgWithoutSigs);

        ImmutableList<PackageInfo> packages =

                ImmutableList.<PackageInfo>builder().addAll(mPackages).add(pkgWithoutSigs).build();

        mPackageManagerBackupAgent =

                new PackageManagerBackupAgent(mPackageManager, packages, USER_ID);

        // A legacy backup is one without an ancestral record version. Ancestral record versions

        // are always written however, so we'll need to delete it from the backup data before

        // restoring.

        runBackupAgentOnBackup();

        deleteKeyFromBackupData(mBackupData, PackageManagerBackupAgent.ANCESTRAL_RECORD_KEY);



        runBackupAgentOnRestore(); // should not fail or timeout



        assertThat(mPackageManagerBackupAgent.getRestoredPackages())

                .containsExactly(EXISTING_PACKAGE_NAME);

    }



    private void runBackupAgentOnBackup() throws Exception {

    private void runBackupAgentOnBackup() throws Exception {

        try (ParcelFileDescriptor oldStateDescriptor = openForReading(mOldState);

        try (ParcelFileDescriptor oldStateDescriptor = openForReading(mOldState);

                ParcelFileDescriptor backupDataDescriptor = openForWriting(mBackupData);

                ParcelFileDescriptor backupDataDescriptor = openForWriting(mBackupData);