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* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
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package org.apache.cayenne.crypto.transformer.bytes;
import java.security.Key;
import java.util.Arrays;
import org.apache.cayenne.crypto.CayenneCryptoException;
/**
* This class not only parse HMAC but also verifies it
* and throws {@link org.apache.cayenne.crypto.CayenneCryptoException} in case it is invalid.
*
* @since 4.0
*/
class HmacDecryptor extends HmacCreator implements BytesDecryptor {
BytesDecryptor delegate;
HmacDecryptor(BytesDecryptor delegate, Header header, Key key) {
super(header, key);
this.delegate = delegate;
}
@Override
public byte[] decrypt(byte[] input, int inputOffset, Key key) {
byte hmacLength = input[inputOffset++];
if(hmacLength <= 0) {
throw new CayenneCryptoException("Input is corrupted: invalid HMAC length.");
}
byte[] receivedHmac = new byte[hmacLength];
byte[] decrypted = delegate.decrypt(input, inputOffset + hmacLength, key);
byte[] realHmac = createHmac(decrypted);
System.arraycopy(input, inputOffset, receivedHmac, 0, hmacLength);
if(!Arrays.equals(receivedHmac, realHmac)) {
throw new CayenneCryptoException("Input is corrupted: wrong HMAC.");
}
return decrypted;
}
}