1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
|
/*
* 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.chunking;
import static com.android.internal.util.Preconditions.checkState;
import android.annotation.Nullable;
import com.android.internal.annotations.VisibleForTesting;
import com.android.server.backup.encryption.tasks.DecryptedChunkOutput;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
/** Writes plaintext chunks to a file, building a digest of the plaintext of the resulting file. */
public class DecryptedChunkFileOutput implements DecryptedChunkOutput {
@VisibleForTesting static final String DIGEST_ALGORITHM = "SHA-256";
private final File mOutputFile;
private final MessageDigest mMessageDigest;
@Nullable private FileOutputStream mFileOutputStream;
private boolean mClosed;
@Nullable private byte[] mDigest;
/**
* Constructs a new instance which writes chunks to the given file and uses the default message
* digest algorithm.
*/
public DecryptedChunkFileOutput(File outputFile) {
mOutputFile = outputFile;
try {
mMessageDigest = MessageDigest.getInstance(DIGEST_ALGORITHM);
} catch (NoSuchAlgorithmException e) {
throw new AssertionError(
"Impossible condition: JCE thinks it does not support AES.", e);
}
}
@Override
public DecryptedChunkOutput open() throws IOException {
checkState(mFileOutputStream == null, "Cannot open twice");
mFileOutputStream = new FileOutputStream(mOutputFile);
return this;
}
@Override
public void processChunk(byte[] plaintextBuffer, int length) throws IOException {
checkState(mFileOutputStream != null, "Must open before processing chunks");
mFileOutputStream.write(plaintextBuffer, /*off=*/ 0, length);
mMessageDigest.update(plaintextBuffer, /*offset=*/ 0, length);
}
@Override
public byte[] getDigest() {
checkState(mClosed, "Must close before getting mDigest");
// After the first call to mDigest() the MessageDigest is reset, thus we must store the
// result.
if (mDigest == null) {
mDigest = mMessageDigest.digest();
}
return mDigest;
}
@Override
public void close() throws IOException {
mFileOutputStream.close();
mClosed = true;
}
}
|
