package org.jboss.resteasy.jose.jwe.crypto;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import org.jboss.resteasy.jose.i18n.Messages;
/**
* Composite key used in AES/CBC/PKCS5Padding/HMAC-SHA2 encryption. This class
* is immutable.
*
* <p>See draft-ietf-jose-json-web-algorithms-10, section 4.8.2.
*
* <p>See draft-mcgrew-aead-aes-cbc-hmac-sha2-01
*
* @author Vladimir Dzhuvinov
* @version $version$ (2013-05-06)
*/
final class CompositeKey
{
/**
* The input key.
*/
private final SecretKey inputKey;
/**
* The extracted MAC key.
*/
private final SecretKey macKey;
/**
* The extracted AES key.
*/
private final SecretKey encKey;
/**
* The expected truncated MAC output length.
*/
private final int truncatedMacLength;
/**
* Creates a new composite key from the specified secret key.
*
* @param inputKey The input key. Must be 256 or 512 bits long. Must
* not be {@code null}.
*
* @throws RuntimeException If the input key length is not supported.
*/
public CompositeKey(final SecretKey inputKey)
throws RuntimeException {
this.inputKey = inputKey;
byte[] secretKeyBytes = inputKey.getEncoded();
if (secretKeyBytes.length == 32) {
// AES_128_CBC_HMAC_SHA_256
// 256 bit key -> 128 bit MAC key + 128 bit AES key
macKey = new SecretKeySpec(secretKeyBytes, 0, 16, "HMACSHA256");
encKey = new SecretKeySpec(secretKeyBytes, 16, 16, "AES");
truncatedMacLength = 16;
} else if (secretKeyBytes.length == 64) {
// AES_256_CBC_HMAC_SHA_512
// 512 bit key -> 256 bit MAC key + 256 bit AES key
macKey = new SecretKeySpec(secretKeyBytes, 0, 32, "HMACSHA512");
encKey = new SecretKeySpec(secretKeyBytes, 32, 32, "AES");
truncatedMacLength = 32;
} else {
throw new RuntimeException(Messages.MESSAGES.unsupportedKeyLength());
}
}
/**
* Gets the input key.
*
* @return The input key.
*/
public SecretKey getInputKey() {
return inputKey;
}
/**
* Gets the extracted MAC key.
*
* @return The extracted MAC key.
*/
public SecretKey getMACKey() {
return macKey;
}
/**
* Gets the expected truncated MAC length.
*
* @return The expected truncated MAC length, in bytes.
*/
public int getTruncatedMACByteLength() {
return truncatedMacLength;
}
/**
* Gets the extracted encryption key.
*
* @return The extracted encryption key.
*/
public SecretKey getAESKey() {
return encKey;
}
}