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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 static java.util.Collections.unmodifiableList;
import android.annotation.Nullable;
import com.android.server.backup.encryption.chunk.ChunkHash;
import com.android.server.backup.encryption.chunking.EncryptedChunk;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import javax.crypto.SecretKey;
/** Task which reads data from some source, splits it into chunks and encrypts new chunks. */
public interface BackupEncrypter {
/** The algorithm which we use to compute the digest of the backup file plaintext. */
String MESSAGE_DIGEST_ALGORITHM = "SHA-256";
/**
* Splits the backup input into encrypted chunks and encrypts new chunks.
*
* @param secretKey Key used to encrypt backup.
* @param fingerprintMixerSalt Fingerprint mixer salt used for content-defined chunking during a
* full backup. Should be {@code null} for a key-value backup.
* @param existingChunks Set of the SHA-256 Macs of chunks the server already has.
* @return a result containing an array of new encrypted chunks to upload, and an ordered
* listing of the chunks in the backup file.
* @throws IOException if a problem occurs reading from the backup data.
* @throws GeneralSecurityException if there is a problem encrypting the data.
*/
Result backup(
SecretKey secretKey,
@Nullable byte[] fingerprintMixerSalt,
Set<ChunkHash> existingChunks)
throws IOException, GeneralSecurityException;
/**
* The result of an incremental backup. Contains new encrypted chunks to upload, and an ordered
* list of the chunks in the backup file.
*/
class Result {
private final List<ChunkHash> mAllChunks;
private final List<EncryptedChunk> mNewChunks;
private final byte[] mDigest;
public Result(List<ChunkHash> allChunks, List<EncryptedChunk> newChunks, byte[] digest) {
mAllChunks = unmodifiableList(new ArrayList<>(allChunks));
mDigest = digest;
mNewChunks = unmodifiableList(new ArrayList<>(newChunks));
}
/**
* Returns an unmodifiable list of the hashes of all the chunks in the backup, in the order
* they appear in the plaintext.
*/
public List<ChunkHash> getAllChunks() {
return mAllChunks;
}
/** Returns an unmodifiable list of the new chunks in the backup. */
public List<EncryptedChunk> getNewChunks() {
return mNewChunks;
}
/** Returns the message digest of the backup. */
public byte[] getDigest() {
return mDigest;
}
}
}
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