001/*
002 * nimbus-jose-jwt
003 *
004 * Copyright 2012-2016, Connect2id Ltd and contributors.
005 *
006 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use
007 * this file except in compliance with the License. You may obtain a copy of the
008 * License at
009 *
010 *    http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software distributed
013 * under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
014 * CONDITIONS OF ANY KIND, either express or implied. See the License for the
015 * specific language governing permissions and limitations under the License.
016 */
017
018package com.nimbusds.jose.crypto.impl;
019
020
021import java.security.PrivateKey;
022import java.security.Provider;
023import java.security.interfaces.RSAPublicKey;
024import javax.crypto.Cipher;
025import javax.crypto.IllegalBlockSizeException;
026import javax.crypto.SecretKey;
027import javax.crypto.spec.SecretKeySpec;
028
029import com.nimbusds.jose.JOSEException;
030import com.nimbusds.jose.util.ByteUtils;
031import net.jcip.annotations.ThreadSafe;
032
033
034/**
035 * RSAES-PKCS1-V1_5 methods for Content Encryption Key (CEK) encryption and
036 * decryption. This class is thread-safe.
037 *
038 * @author Vladimir Dzhuvinov
039 * @version 2017-06-01
040 */
041@ThreadSafe
042public class RSA1_5 {
043
044
045        /**
046         * Encrypts the specified Content Encryption Key (CEK).
047         *
048         * @param pub      The public RSA key. Must not be {@code null}.
049         * @param cek      The Content Encryption Key (CEK) to encrypt. Must
050         *                 not be {@code null}.
051         * @param provider The JCA provider, or {@code null} to use the default
052         *                 one.
053         *
054         * @return The encrypted Content Encryption Key (CEK).
055         *
056         * @throws JOSEException If encryption failed.
057         */
058        public static byte[] encryptCEK(final RSAPublicKey pub, final SecretKey cek, Provider provider)
059                throws JOSEException {
060
061                try {
062                        Cipher cipher = CipherHelper.getInstance("RSA/ECB/PKCS1Padding", provider);
063                        cipher.init(Cipher.ENCRYPT_MODE, pub);
064                        return cipher.doFinal(cek.getEncoded());
065                        
066                } catch (IllegalBlockSizeException e) {
067                        throw new JOSEException("RSA block size exception: The RSA key is too short, try a longer one", e);
068                } catch (Exception e) {
069                        // java.security.NoSuchAlgorithmException
070                        // java.security.InvalidKeyException
071                        throw new JOSEException("Couldn't encrypt Content Encryption Key (CEK): " + e.getMessage(), e);
072                }
073        }
074
075
076        /**
077         * Decrypts the specified encrypted Content Encryption Key (CEK).
078         *
079         * @param priv         The private RSA key. Must not be {@code null}.
080         * @param encryptedCEK The encrypted Content Encryption Key (CEK) to
081         *                     decrypt. Must not be {@code null}.
082         * @param provider     The JCA provider, or {@code null} to use the
083         *                     default one.
084         *
085         * @return The decrypted Content Encryption Key (CEK), {@code null} if
086         *         there was a CEK key length mismatch.
087         *
088         * @throws JOSEException If decryption failed.
089         */
090        public static SecretKey decryptCEK(final PrivateKey priv,
091                                           final byte[] encryptedCEK,
092                                           final int keyLength,
093                                           final Provider provider)
094                throws JOSEException {
095
096                try {
097                        Cipher cipher = CipherHelper.getInstance("RSA/ECB/PKCS1Padding", provider);
098                        cipher.init(Cipher.DECRYPT_MODE, priv);
099                        byte[] secretKeyBytes = cipher.doFinal(encryptedCEK);
100
101                        if (ByteUtils.safeBitLength(secretKeyBytes) != keyLength) {
102                                // CEK key length mismatch
103                                return null;
104                        }
105
106                        return new SecretKeySpec(secretKeyBytes, "AES");
107
108                } catch (Exception e) {
109
110                        // java.security.NoSuchAlgorithmException
111                        // java.security.InvalidKeyException
112                        // javax.crypto.IllegalBlockSizeException
113                        // javax.crypto.BadPaddingException
114                        throw new JOSEException("Couldn't decrypt Content Encryption Key (CEK): " + e.getMessage(), e);
115                }
116        }
117
118
119        /**
120         * Prevents public instantiation.
121         */
122        private RSA1_5() { }
123}