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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 java.security.Provider;
import javax.crypto.SecretKey;
import javax.crypto.spec.SecretKeySpec;
import com.nimbusds.jose.JOSEException;
import com.nimbusds.jose.KeyLengthException;
import com.nimbusds.jose.util.ByteUtils;
import com.nimbusds.jose.util.Container;
import net.jcip.annotations.ThreadSafe;
/**
* AES GCM methods for Content Encryption Key (CEK) encryption and
* decryption. This class is thread-safe.
*
* See RFC 7518 (JWA), section 4.7.
*
* @author Melisa Halsband
* @author Vladimir Dzhuvinov
* @version 2017-06-01
*/
@ThreadSafe
public class AESGCMKW {
/**
* Encrypts the specified Content Encryption Key (CEK).
*
* @param cek The Content Encryption Key (CEK) to encrypt. Must
* not be {@code null}.
* @param iv The initialisation vector (IV). Must not be
* {@code null}. The contained IV must not be
* {@code null} either.
* @param kek The AES Key Encryption Key (KEK). Must not be
* {@code null}.
* @param provider The JCA provider to use, {@code null} implies the
* default.
*
* @return The encrypted Content Encryption Key (CEK).
*
* @throws JOSEException If encryption failed.
*/
public static AuthenticatedCipherText encryptCEK(final SecretKey cek,
final Container iv,
final SecretKey kek,
Provider provider)
throws JOSEException {
return AESGCM.encrypt(kek, iv, cek.getEncoded(), new byte[0], provider);
}
/**
* Decrypts the specified encrypted Content Encryption Key (CEK).
*
* @param kek The AES Key Encription Key. Must not be
* {@code null}.
* @param iv The initialisation vector (IV). Must not be
* {@code null}.
* @param authEncrCEK The encrypted Content Encryption Key (CEK) to
* decrypt and authentication tag. Must not be
* {@code null}.
* @param keyLength The expected key length, in bits.
* @param provider The JCA provider, {@code null} to use the
* default.
*
* @return The decrypted Content Encryption Key (CEK).
*
* @throws JOSEException If decryption failed.
*/
public static SecretKey decryptCEK(final SecretKey kek,
final byte[] iv,
final AuthenticatedCipherText authEncrCEK,
final int keyLength,
final Provider provider)
throws JOSEException {
byte[] keyBytes = AESGCM.decrypt(kek, iv, authEncrCEK.getCipherText(), new byte[0], authEncrCEK.getAuthenticationTag(), provider);
if (ByteUtils.safeBitLength(keyBytes) != keyLength) {
throw new KeyLengthException("CEK key length mismatch: " + ByteUtils.safeBitLength(keyBytes) + " != " + keyLength);
}
return new SecretKeySpec(keyBytes, "AES");
}
/**
* Prevents public instantiation.
*/
private AESGCMKW() { }
}