001/*
002 * nimbus-jose-jwt
003 *
004 * Copyright 2012-2016, Connect2id Ltd.
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;
019
020
021import java.util.Collections;
022import java.util.LinkedHashSet;
023import java.util.Set;
024import javax.crypto.SecretKey;
025
026import com.nimbusds.jose.*;
027import com.nimbusds.jose.crypto.impl.AlgorithmSupportMessage;
028import com.nimbusds.jose.crypto.impl.HMAC;
029import com.nimbusds.jose.crypto.impl.MACProvider;
030import com.nimbusds.jose.jwk.OctetSequenceKey;
031import com.nimbusds.jose.util.Base64URL;
032import com.nimbusds.jose.util.ByteUtils;
033import com.nimbusds.jose.util.StandardCharset;
034import net.jcip.annotations.ThreadSafe;
035
036
037
038/**
039 * Message Authentication Code (MAC) signer of 
040 * {@link com.nimbusds.jose.JWSObject JWS objects}. Expects a secret key.
041 *
042 * <p>See RFC 7518
043 * <a href="https://tools.ietf.org/html/rfc7518#section-3.2">section 3.2</a>
044 * for more information.
045 *
046 * <p>This class is thread-safe.
047 *
048 * <p>Supports the following algorithms:
049 *
050 * <ul>
051 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#HS256}
052 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#HS384}
053 *     <li>{@link com.nimbusds.jose.JWSAlgorithm#HS512}
054 * </ul>
055 * 
056 * @author Vladimir Dzhuvinov
057 * @version 2016-07-27
058 */
059@ThreadSafe
060public class MACSigner extends MACProvider implements JWSSigner {
061
062
063        /**
064         * Returns the minimal required secret length for the specified HMAC
065         * JWS algorithm.
066         *
067         * @param alg The HMAC JWS algorithm. Must be
068         *            {@link #SUPPORTED_ALGORITHMS supported} and not
069         *            {@code null}.
070         *
071         * @return The minimal required secret length, in bits.
072         *
073         * @throws JOSEException If the algorithm is not supported.
074         */
075        public static int getMinRequiredSecretLength(final JWSAlgorithm alg)
076                throws JOSEException {
077
078                if (JWSAlgorithm.HS256.equals(alg)) {
079                        return 256;
080                } else if (JWSAlgorithm.HS384.equals(alg)) {
081                        return 384;
082                } else if (JWSAlgorithm.HS512.equals(alg)) {
083                        return 512;
084                } else {
085                        throw new JOSEException(AlgorithmSupportMessage.unsupportedJWSAlgorithm(
086                                alg,
087                                SUPPORTED_ALGORITHMS));
088                }
089        }
090
091
092        /**
093         * Returns the compatible JWS HMAC algorithms for the specified secret
094         * length.
095         *
096         * @param secretLength The secret length in bits. Must not be negative.
097         *
098         * @return The compatible HMAC algorithms, empty set if the secret
099         *         length is too short for any algorithm.
100         */
101        public static Set<JWSAlgorithm> getCompatibleAlgorithms(final int secretLength) {
102
103                Set<JWSAlgorithm> hmacAlgs = new LinkedHashSet<>();
104
105                if (secretLength >= 256)
106                        hmacAlgs.add(JWSAlgorithm.HS256);
107
108                if (secretLength >= 384)
109                        hmacAlgs.add(JWSAlgorithm.HS384);
110
111                if (secretLength >= 512)
112                        hmacAlgs.add(JWSAlgorithm.HS512);
113
114                return Collections.unmodifiableSet(hmacAlgs);
115        }
116
117
118        /**
119         * Creates a new Message Authentication (MAC) signer.
120         *
121         * @param secret The secret. Must be at least 256 bits long and not
122         *               {@code null}.
123         *
124         * @throws KeyLengthException If the secret length is shorter than the
125         *                            minimum 256-bit requirement.
126         */
127        public MACSigner(final byte[] secret)
128                throws KeyLengthException {
129
130                super(secret, getCompatibleAlgorithms(ByteUtils.bitLength(secret.length)));
131        }
132
133
134        /**
135         * Creates a new Message Authentication (MAC) signer.
136         *
137         * @param secretString The secret as a UTF-8 encoded string. Must be at
138         *                     least 256 bits long and not {@code null}.
139         *
140         * @throws KeyLengthException If the secret length is shorter than the
141         *                            minimum 256-bit requirement.
142         */
143        public MACSigner(final String secretString)
144                throws KeyLengthException {
145
146                this(secretString.getBytes(StandardCharset.UTF_8));
147        }
148
149
150        /**
151         * Creates a new Message Authentication (MAC) signer.
152         *
153         * @param secretKey The secret key. Must be at least 256 bits long and
154         *                  not {@code null}.
155         *
156         * @throws KeyLengthException If the secret length is shorter than the
157         *                            minimum 256-bit requirement.
158         */
159        public MACSigner(final SecretKey secretKey)
160                throws KeyLengthException {
161
162                this(secretKey.getEncoded());
163        }
164
165
166        /**
167         * Creates a new Message Authentication (MAC) signer.
168         *
169         * @param jwk The secret as a JWK. Must be at least 256 bits long and
170         *            not {@code null}.
171         *
172         * @throws KeyLengthException If the secret length is shorter than the
173         *                            minimum 256-bit requirement.
174         */
175        public MACSigner(final OctetSequenceKey jwk)
176                throws KeyLengthException {
177
178                this(jwk.toByteArray());
179        }
180
181
182        @Override
183        public Base64URL sign(final JWSHeader header, final byte[] signingInput)
184                throws JOSEException {
185
186                final int minRequiredLength = getMinRequiredSecretLength(header.getAlgorithm());
187
188                if (getSecret().length < ByteUtils.byteLength(minRequiredLength)) {
189                        throw new KeyLengthException("The secret length for " + header.getAlgorithm() + " must be at least " + minRequiredLength + " bits");
190                }
191
192                String jcaAlg = getJCAAlgorithmName(header.getAlgorithm());
193                byte[] hmac = HMAC.compute(jcaAlg, getSecret(), signingInput, getJCAContext().getProvider());
194                return Base64URL.encode(hmac);
195        }
196}