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/*
* nimbus-jose-jwt
*
* Copyright 2012-2016, Connect2id Ltd and contributors.
*
* 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.nimbusds.jose.crypto.impl;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import com.nimbusds.jose.KeyLengthException;
import net.jcip.annotations.Immutable;
/**
* Composite key used in AES/CBC/PKCS5Padding/HMAC-SHA2 encryption. This class
* is immutable.
*
* See RFC 7518 (JWA), section 5.2.
*
*
See draft-mcgrew-aead-aes-cbc-hmac-sha2-01
*
* @author Vladimir Dzhuvinov
* @version 2015-06-29
*/
@Immutable
public 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, 384 or 512 bits long.
* Must not be {@code null}.
*
* @throws KeyLengthException If the input key length is not supported.
*/
public CompositeKey(final SecretKey inputKey)
throws KeyLengthException {
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 == 48) {
// AES_192_CBC_HMAC_SHA_384
// 384 bit key -> 129 bit MAC key + 192 bit AES key
macKey = new SecretKeySpec(secretKeyBytes, 0, 24, "HMACSHA384");
encKey = new SecretKeySpec(secretKeyBytes, 24, 24, "AES");
truncatedMacLength = 24;
} 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 KeyLengthException("Unsupported AES/CBC/PKCS5Padding/HMAC-SHA2 key length, must be 256, 384 or 512 bits");
}
}
/**
* 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;
}
}