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/*
* Copyright (C) 2016 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 org.mozilla.thirdparty.com.google.android.exoplayer2.upstream.crypto;
import static org.mozilla.thirdparty.com.google.android.exoplayer2.util.Util.castNonNull;
import androidx.annotation.Nullable;
import org.mozilla.thirdparty.com.google.android.exoplayer2.upstream.DataSink;
import org.mozilla.thirdparty.com.google.android.exoplayer2.upstream.DataSpec;
import java.io.IOException;
import javax.crypto.Cipher;
/**
* A wrapping {@link DataSink} that encrypts the data being consumed.
*/
public final class AesCipherDataSink implements DataSink {
private final DataSink wrappedDataSink;
private final byte[] secretKey;
@Nullable private final byte[] scratch;
@Nullable private AesFlushingCipher cipher;
/**
* Create an instance whose {@code write} methods have the side effect of overwriting the input
* {@code data}. Use this constructor for maximum efficiency in the case that there is no
* requirement for the input data arrays to remain unchanged.
*
* @param secretKey The key data.
* @param wrappedDataSink The wrapped {@link DataSink}.
*/
public AesCipherDataSink(byte[] secretKey, DataSink wrappedDataSink) {
this(secretKey, wrappedDataSink, null);
}
/**
* Create an instance whose {@code write} methods are free of side effects. Use this constructor
* when the input data arrays are required to remain unchanged.
*
* @param secretKey The key data.
* @param wrappedDataSink The wrapped {@link DataSink}.
* @param scratch Scratch space. Data is encrypted into this array before being written to the
* wrapped {@link DataSink}. It should be of appropriate size for the expected writes. If a
* write is larger than the size of this array the write will still succeed, but multiple
* cipher calls will be required to complete the operation. If {@code null} then encryption
* will overwrite the input {@code data}.
*/
public AesCipherDataSink(byte[] secretKey, DataSink wrappedDataSink, @Nullable byte[] scratch) {
this.wrappedDataSink = wrappedDataSink;
this.secretKey = secretKey;
this.scratch = scratch;
}
@Override
public void open(DataSpec dataSpec) throws IOException {
wrappedDataSink.open(dataSpec);
long nonce = CryptoUtil.getFNV64Hash(dataSpec.key);
cipher = new AesFlushingCipher(Cipher.ENCRYPT_MODE, secretKey, nonce,
dataSpec.absoluteStreamPosition);
}
@Override
public void write(byte[] data, int offset, int length) throws IOException {
if (scratch == null) {
// In-place mode. Writes over the input data.
castNonNull(cipher).updateInPlace(data, offset, length);
wrappedDataSink.write(data, offset, length);
} else {
// Use scratch space. The original data remains intact.
int bytesProcessed = 0;
while (bytesProcessed < length) {
int bytesToProcess = Math.min(length - bytesProcessed, scratch.length);
castNonNull(cipher)
.update(data, offset + bytesProcessed, bytesToProcess, scratch, /* outOffset= */ 0);
wrappedDataSink.write(scratch, /* offset= */ 0, bytesToProcess);
bytesProcessed += bytesToProcess;
}
}
}
@Override
public void close() throws IOException {
cipher = null;
wrappedDataSink.close();
}
}
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