001package com.nimbusds.jose.crypto;
002
003
004import java.util.HashSet;
005import java.util.Set;
006import javax.crypto.SecretKey;
007
008import com.nimbusds.jose.EncryptionMethod;
009import com.nimbusds.jose.JOSEException;
010import com.nimbusds.jose.JWEAlgorithm;
011import com.nimbusds.jose.JWEDecrypter;
012import com.nimbusds.jose.ReadOnlyJWEHeader;
013import com.nimbusds.jose.util.Base64URL;
014import com.nimbusds.jose.util.StringUtils;
015
016
017/**
018 * Direct decrypter of {@link com.nimbusds.jose.JWEObject JWE objects} with a
019 * shared symmetric key. This class is thread-safe.
020 *
021 * <p>Supports the following JWE algorithms:
022 *
023 * <ul>
024 *     <li>{@link com.nimbusds.jose.JWEAlgorithm#DIR}
025 * </ul>
026 *
027 * <p>Supports the following encryption methods:
028 *
029 * <ul>
030 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256}
031 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192CBC_HS384}
032 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512}
033 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128GCM}
034 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192GCM}
035 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256GCM}
036 * </ul>
037 *
038 * <p>Accepts all {@link com.nimbusds.jose.JWEHeader#getRegisteredParameterNames
039 * registered JWE header parameters}. Use {@link #setAcceptedAlgorithms} and
040 * {@link #setAcceptedEncryptionMethods} to restrict the acceptable JWE
041 * algorithms and encryption methods.
042 * 
043 * @author Vladimir Dzhuvinov
044 * @version $version$ (2014-04-22)
045 */
046public class DirectDecrypter extends DirectCryptoProvider implements JWEDecrypter {
047
048
049        /**
050         * The accepted JWE algorithms.
051         */
052        private Set<JWEAlgorithm> acceptedAlgs =
053                new HashSet<JWEAlgorithm>(supportedAlgorithms());
054
055
056        /**
057         * The accepted encryption methods.
058         */
059        private Set<EncryptionMethod> acceptedEncs =
060                new HashSet<EncryptionMethod>(supportedEncryptionMethods());
061
062
063        /**
064         * The critical header parameter checker.
065         */
066        private final CriticalHeaderParameterChecker critParamChecker =
067                new CriticalHeaderParameterChecker();
068
069
070        /**
071         * Creates a new direct decrypter.
072         *
073         * @param key The shared symmetric key. Its algorithm must be "AES".
074         *            Must be 128 bits (16 bytes), 256 bits (32 bytes) or 512 
075         *            bits (64 bytes) long. Must not be {@code null}.
076         *
077         * @throws JOSEException If the key length is unexpected.
078         */
079        public DirectDecrypter(final SecretKey key)
080                throws JOSEException {
081
082                super(key);
083        }
084
085
086        /**
087         * Creates a new direct decrypter.
088         *
089         * @param keyBytes The shared symmetric key, as a byte array. Must be 
090         *                 128 bits (16 bytes), 256 bits (32 bytes) or 512 bits
091         *                 (64 bytes) long. Must not be {@code null}.
092         *
093         * @throws JOSEException If the key length is unexpected.
094         */
095        public DirectDecrypter(final byte[] keyBytes)
096                throws JOSEException {
097
098                super(keyBytes);
099        }
100
101
102        @Override
103        public Set<JWEAlgorithm> getAcceptedAlgorithms() {
104
105                return acceptedAlgs;
106        }
107
108
109        @Override
110        public void setAcceptedAlgorithms(final Set<JWEAlgorithm> acceptedAlgs) {
111
112                if (acceptedAlgs == null) {
113                        throw new IllegalArgumentException("The accepted JWE algorithms must not be null");
114                }
115
116                if (! supportedAlgorithms().containsAll(acceptedAlgs)) {
117                        throw new IllegalArgumentException("Unsupported JWE algorithm(s)");
118                }
119
120                this.acceptedAlgs = acceptedAlgs;
121        }
122
123
124        @Override
125        public Set<EncryptionMethod> getAcceptedEncryptionMethods() {
126
127                return acceptedEncs;
128        }
129
130
131        @Override
132        public void setAcceptedEncryptionMethods(final Set<EncryptionMethod> acceptedEncs) {
133
134                if (acceptedEncs == null)
135                        throw new IllegalArgumentException("The accepted encryption methods must not be null");
136
137                if (!supportedEncryptionMethods().containsAll(acceptedEncs)) {
138                        throw new IllegalArgumentException("Unsupported encryption method(s)");
139                }
140
141                this.acceptedEncs = acceptedEncs;
142        }
143
144
145        @Override
146        public Set<String> getIgnoredCriticalHeaderParameters() {
147
148                return critParamChecker.getIgnoredCriticalHeaders();
149        }
150
151
152        @Override
153        public void setIgnoredCriticalHeaderParameters(final Set<String> headers) {
154
155                critParamChecker.setIgnoredCriticalHeaders(headers);
156        }
157
158
159        @Override
160        public byte[] decrypt(final ReadOnlyJWEHeader header,
161                              final Base64URL encryptedKey,
162                              final Base64URL iv,
163                              final Base64URL cipherText,
164                              final Base64URL authTag) 
165                throws JOSEException {
166
167                // Validate required JWE parts
168                if (encryptedKey != null) {
169
170                        throw new JOSEException("Unexpected encrypted key, must be omitted");
171                }       
172
173                if (iv == null) {
174
175                        throw new JOSEException("The initialization vector (IV) must not be null");
176                }
177
178                if (authTag == null) {
179
180                        throw new JOSEException("The authentication tag must not be null");
181                }
182                
183
184                JWEAlgorithm alg = header.getAlgorithm();
185
186                if (! alg.equals(JWEAlgorithm.DIR)) {
187
188                        throw new JOSEException("Unsupported algorithm, must be \"dir\"");
189                }
190
191                if (! critParamChecker.headerPasses(header)) {
192
193                        throw new JOSEException("Unsupported critical header parameter");
194                }
195
196                // Compose the AAD
197                byte[] aad = StringUtils.toByteArray(header.toBase64URL().toString());
198
199                // Decrypt the cipher text according to the JWE enc
200                EncryptionMethod enc = header.getEncryptionMethod();
201
202                byte[] plainText;
203
204                if (enc.equals(EncryptionMethod.A128CBC_HS256) || enc.equals(EncryptionMethod.A192CBC_HS384) || enc.equals(EncryptionMethod.A256CBC_HS512)) {
205
206                        plainText = AESCBC.decryptAuthenticated(getKey(), iv.decode(), cipherText.decode(), aad, authTag.decode(), contentEncryptionProvider, macProvider);
207
208                } else if (enc.equals(EncryptionMethod.A128GCM) || enc.equals(EncryptionMethod.A192GCM) || enc.equals(EncryptionMethod.A256GCM)) {
209
210                        plainText = AESGCM.decrypt(getKey(), iv.decode(), cipherText.decode(), aad, authTag.decode(), contentEncryptionProvider);
211
212                } else {
213
214                        throw new JOSEException("Unsupported encryption method, must be A128CBC_HS256, A192CBC_HS384, A256CBC_HS512, A128GCM, A192GCM or A128GCM");
215                }
216
217
218                // Apply decompression if requested
219                return DeflateHelper.applyDecompression(header, plainText);
220        }
221}
222