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/*
* Copyright (C) 2019 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.server.backup.encryption.tasks;
import android.content.Context;
import android.util.Slog;
import com.android.internal.annotations.VisibleForTesting;
import com.android.server.backup.encryption.StreamUtils;
import com.android.server.backup.encryption.chunking.ProtoStore;
import com.android.server.backup.encryption.chunking.cdc.FingerprintMixer;
import com.android.server.backup.encryption.client.CryptoBackupServer;
import com.android.server.backup.encryption.keys.RecoverableKeyStoreSecondaryKey;
import com.android.server.backup.encryption.keys.TertiaryKeyManager;
import com.android.server.backup.encryption.keys.TertiaryKeyRotationScheduler;
import com.android.server.backup.encryption.protos.nano.ChunksMetadataProto.ChunkListing;
import com.android.server.backup.encryption.protos.nano.WrappedKeyProto;
import java.io.IOException;
import java.io.InputStream;
import java.security.SecureRandom;
import java.util.Arrays;
import java.util.Optional;
import java.util.concurrent.Callable;
import javax.crypto.SecretKey;
/**
* Task which reads a stream of plaintext full backup data, chunks it, encrypts it and uploads it to
* the server.
*
* <p>Once the backup completes or fails, closes the input stream.
*/
public class EncryptedFullBackupTask implements Callable<Void> {
private static final String TAG = "EncryptedFullBackupTask";
private static final int MIN_CHUNK_SIZE_BYTES = 2 * 1024;
private static final int MAX_CHUNK_SIZE_BYTES = 64 * 1024;
private static final int AVERAGE_CHUNK_SIZE_BYTES = 4 * 1024;
// TODO(b/69350270): Remove this hard-coded salt and related logic once we feel confident that
// incremental backup has happened at least once for all existing packages/users since we moved
// to
// using a randomly generated salt.
//
// The hard-coded fingerprint mixer salt was used for a short time period before replaced by one
// that is randomly generated on initial non-incremental backup and stored in ChunkListing to be
// reused for succeeding incremental backups. If an old ChunkListing does not have a
// fingerprint_mixer_salt, we assume that it was last backed up before a randomly generated salt
// is used so we use the hardcoded salt and set ChunkListing#fingerprint_mixer_salt to this
// value.
// Eventually all backup ChunkListings will have this field set and then we can remove the
// default
// value in the code.
static final byte[] DEFAULT_FINGERPRINT_MIXER_SALT =
Arrays.copyOf(new byte[] {20, 23}, FingerprintMixer.SALT_LENGTH_BYTES);
private final ProtoStore<ChunkListing> mChunkListingStore;
private final TertiaryKeyManager mTertiaryKeyManager;
private final InputStream mInputStream;
private final EncryptedBackupTask mTask;
private final String mPackageName;
private final SecureRandom mSecureRandom;
/** Creates a new instance with the default min, max and average chunk sizes. */
public static EncryptedFullBackupTask newInstance(
Context context,
CryptoBackupServer cryptoBackupServer,
SecureRandom secureRandom,
RecoverableKeyStoreSecondaryKey secondaryKey,
String packageName,
InputStream inputStream)
throws IOException {
EncryptedBackupTask encryptedBackupTask =
new EncryptedBackupTask(
cryptoBackupServer,
secureRandom,
packageName,
new BackupStreamEncrypter(
inputStream,
MIN_CHUNK_SIZE_BYTES,
MAX_CHUNK_SIZE_BYTES,
AVERAGE_CHUNK_SIZE_BYTES));
TertiaryKeyManager tertiaryKeyManager =
new TertiaryKeyManager(
context,
secureRandom,
TertiaryKeyRotationScheduler.getInstance(context),
secondaryKey,
packageName);
return new EncryptedFullBackupTask(
ProtoStore.createChunkListingStore(context),
tertiaryKeyManager,
encryptedBackupTask,
inputStream,
packageName,
new SecureRandom());
}
@VisibleForTesting
EncryptedFullBackupTask(
ProtoStore<ChunkListing> chunkListingStore,
TertiaryKeyManager tertiaryKeyManager,
EncryptedBackupTask task,
InputStream inputStream,
String packageName,
SecureRandom secureRandom) {
mChunkListingStore = chunkListingStore;
mTertiaryKeyManager = tertiaryKeyManager;
mInputStream = inputStream;
mTask = task;
mPackageName = packageName;
mSecureRandom = secureRandom;
}
@Override
public Void call() throws Exception {
try {
Optional<ChunkListing> maybeOldChunkListing =
mChunkListingStore.loadProto(mPackageName);
if (maybeOldChunkListing.isPresent()) {
Slog.i(TAG, "Found previous chunk listing for " + mPackageName);
}
// If the key has been rotated then we must re-encrypt all of the backup data.
if (mTertiaryKeyManager.wasKeyRotated()) {
Slog.i(
TAG,
"Key was rotated or newly generated for "
+ mPackageName
+ ", so performing a full backup.");
maybeOldChunkListing = Optional.empty();
mChunkListingStore.deleteProto(mPackageName);
}
SecretKey tertiaryKey = mTertiaryKeyManager.getKey();
WrappedKeyProto.WrappedKey wrappedTertiaryKey = mTertiaryKeyManager.getWrappedKey();
ChunkListing newChunkListing;
if (!maybeOldChunkListing.isPresent()) {
byte[] fingerprintMixerSalt = new byte[FingerprintMixer.SALT_LENGTH_BYTES];
mSecureRandom.nextBytes(fingerprintMixerSalt);
newChunkListing =
mTask.performNonIncrementalBackup(
tertiaryKey, wrappedTertiaryKey, fingerprintMixerSalt);
} else {
ChunkListing oldChunkListing = maybeOldChunkListing.get();
if (oldChunkListing.fingerprintMixerSalt == null
|| oldChunkListing.fingerprintMixerSalt.length == 0) {
oldChunkListing.fingerprintMixerSalt = DEFAULT_FINGERPRINT_MIXER_SALT;
}
newChunkListing =
mTask.performIncrementalBackup(
tertiaryKey, wrappedTertiaryKey, oldChunkListing);
}
mChunkListingStore.saveProto(mPackageName, newChunkListing);
Slog.v(TAG, "Saved chunk listing for " + mPackageName);
} catch (IOException e) {
Slog.e(TAG, "Storage exception, wiping state");
mChunkListingStore.deleteProto(mPackageName);
throw e;
} finally {
StreamUtils.closeQuietly(mInputStream);
}
return null;
}
/**
* Signals to the task that the backup has been cancelled. If the upload has not yet started
* then the task will not upload any data to the server or save the new chunk listing.
*
* <p>You must then terminate the input stream.
*/
public void cancel() {
mTask.cancel();
}
}
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