001/*
002 * nimbus-jose-jwt
003 *
004 * Copyright 2012-2021, 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;
019
020
021import com.nimbusds.jose.JOSEException;
022import com.nimbusds.jose.JWECryptoParts;
023import com.nimbusds.jose.JWEEncrypter;
024import com.nimbusds.jose.JWEHeader;
025import com.nimbusds.jose.crypto.impl.ECDH1PU;
026import com.nimbusds.jose.crypto.impl.ECDH1PUCryptoProvider;
027import com.nimbusds.jose.jwk.Curve;
028import com.nimbusds.jose.jwk.ECKey;
029import net.jcip.annotations.ThreadSafe;
030
031import javax.crypto.SecretKey;
032import java.security.*;
033import java.security.interfaces.ECPrivateKey;
034import java.security.interfaces.ECPublicKey;
035import java.security.spec.ECParameterSpec;
036import java.util.Collections;
037import java.util.LinkedHashSet;
038import java.util.Set;
039
040
041/**
042 * Elliptic Curve Diffie-Hellman encrypter of
043 * {@link com.nimbusds.jose.JWEObject JWE objects} for curves using an EC JWK.
044 * Expects a public EC key (with a P-256, P-384, or P-521 curve).
045 *
046 * <p>Public Key Authenticated Encryption for JOSE
047 * <a href="https://datatracker.ietf.org/doc/html/draft-madden-jose-ecdh-1pu-04">ECDH-1PU</a>
048 * for more information.
049 *
050 * <p>For Curve25519/X25519, see {@link ECDH1PUX25519Encrypter} instead.
051 *
052 * <p>This class is thread-safe.
053 *
054 * <p>Supports the following key management algorithms:
055 *
056 * <ul>
057 *     <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_1PU}
058 *     <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_1PU_A128KW}
059 *     <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_1PU_A192KW}
060 *     <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_1PU_A256KW}
061 * </ul>
062 *
063 * <p>Supports the following elliptic curves:
064 *
065 * <ul>
066 *     <li>{@link Curve#P_256}
067 *     <li>{@link Curve#P_384}
068 *     <li>{@link Curve#P_521}
069 * </ul>
070 *
071 * <p>Supports the following content encryption algorithms for Direct key agreement mode:
072 *
073 * <ul>
074 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256}
075 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192CBC_HS384}
076 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512}
077 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128GCM}
078 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192GCM}
079 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256GCM}
080 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256_DEPRECATED}
081 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512_DEPRECATED}
082 *     <li>{@link com.nimbusds.jose.EncryptionMethod#XC20P}
083 * </ul>
084 *
085 * <p>Supports the following content encryption algorithms for Key wrapping mode:
086 *
087 * <ul>
088 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256}
089 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A192CBC_HS384}
090 *     <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512}
091 * </ul>
092 *
093 * @author Alexander Martynov
094 * @version 2021-08-03
095 */
096@ThreadSafe
097public class ECDH1PUEncrypter extends ECDH1PUCryptoProvider implements JWEEncrypter {
098
099
100    /**
101     * The supported EC JWK curves by the ECDH crypto provider class.
102     */
103    public static final Set<Curve> SUPPORTED_ELLIPTIC_CURVES;
104
105
106    static {
107        Set<Curve> curves = new LinkedHashSet<>();
108        curves.add(Curve.P_256);
109        curves.add(Curve.P_384);
110        curves.add(Curve.P_521);
111        SUPPORTED_ELLIPTIC_CURVES = Collections.unmodifiableSet(curves);
112    }
113
114
115    /**
116     * The public EC key.
117     */
118    private final ECPublicKey publicKey;
119
120    /**
121     * The private EC key;
122     */
123    private final ECPrivateKey privateKey;
124
125    /**
126     * The externally supplied AES content encryption key (CEK) to use,
127     * {@code null} to generate a CEK for each JWE.
128     */
129    private final SecretKey contentEncryptionKey;
130
131    /**
132     * Creates a new Elliptic Curve Diffie-Hellman encrypter.
133     *
134     * @param privateKey The private EC key. Must not be {@code null}.
135     * @param publicKey  The public EC key. Must not be {@code null}.
136     *
137     * @throws JOSEException If the elliptic curve is not supported.
138     */
139    public ECDH1PUEncrypter(final ECPrivateKey privateKey, final ECPublicKey publicKey)
140        throws JOSEException {
141
142        this(privateKey, publicKey, null);
143    }
144
145
146    /**
147     * Creates a new Elliptic Curve Diffie-Hellman encrypter with an
148     * optionally specified content encryption key (CEK).
149     *
150     * @param privateKey           The private EC key. Must not be
151     *                             {@code null}.
152     * @param publicKey            The public EC key. Must not be
153     *                             {@code null}.
154     * @param contentEncryptionKey The content encryption key (CEK) to use.
155     *                             If specified its algorithm must be "AES"
156     *                             and its length must match the expected
157     *                             for the JWE encryption method ("enc").
158     *                             If {@code null} a CEK will be generated
159     *                             for each JWE.
160     * @throws JOSEException       If the elliptic curve is not supported.
161     */
162    public ECDH1PUEncrypter(final ECPrivateKey privateKey,
163                            final ECPublicKey publicKey,
164                            final SecretKey contentEncryptionKey)
165            throws JOSEException {
166
167        super(Curve.forECParameterSpec(publicKey.getParams()));
168
169        this.privateKey = privateKey;
170        this.publicKey = publicKey;
171
172        if (contentEncryptionKey != null && (contentEncryptionKey.getAlgorithm() == null || !contentEncryptionKey.getAlgorithm().equals("AES")))
173            throw new IllegalArgumentException("The algorithm of the content encryption key (CEK) must be AES");
174
175        this.contentEncryptionKey = contentEncryptionKey;
176    }
177
178
179    /**
180     * Returns the public EC key.
181     *
182     * @return The public EC key.
183     */
184    public ECPublicKey getPublicKey() {
185
186        return publicKey;
187    }
188
189
190    /**
191     * Returns the private EC key.
192     *
193     * @return The private EC key.
194     */
195    public ECPrivateKey getPrivateKey() {
196
197        return privateKey;
198    }
199
200
201    @Override
202    public Set<Curve> supportedEllipticCurves() {
203
204        return SUPPORTED_ELLIPTIC_CURVES;
205    }
206
207
208    @Override
209    public JWECryptoParts encrypt(final JWEHeader header, final byte[] clearText)
210        throws JOSEException {
211
212        // Generate ephemeral EC key pair on the same curve as the consumer's public key
213        KeyPair ephemeralKeyPair = generateEphemeralKeyPair(publicKey.getParams());
214        ECPublicKey ephemeralPublicKey = (ECPublicKey)ephemeralKeyPair.getPublic();
215        ECPrivateKey ephemeralPrivateKey = (ECPrivateKey)ephemeralKeyPair.getPrivate();
216
217        // Add the ephemeral public EC key to the header
218        JWEHeader updatedHeader = new JWEHeader.Builder(header).
219            ephemeralPublicKey(new ECKey.Builder(getCurve(), ephemeralPublicKey).build()).
220            build();
221
222        SecretKey Z = ECDH1PU.deriveSenderZ(
223                privateKey,
224                publicKey,
225                ephemeralPrivateKey,
226                getJCAContext().getKeyEncryptionProvider()
227        );
228
229        return encryptWithZ(updatedHeader, Z, clearText, contentEncryptionKey);
230    }
231
232
233    /**
234     * Generates a new ephemeral EC key pair with the specified curve.
235     *
236     * @param ecParameterSpec The EC key spec. Must not be {@code null}.
237     *
238     * @return The EC key pair.
239     *
240     * @throws JOSEException If the EC key pair couldn't be generated.
241     */
242    private KeyPair generateEphemeralKeyPair(final ECParameterSpec ecParameterSpec)
243        throws JOSEException {
244
245        Provider keProvider = getJCAContext().getKeyEncryptionProvider();
246
247        try {
248            KeyPairGenerator generator;
249
250            if (keProvider != null) {
251                generator = KeyPairGenerator.getInstance("EC", keProvider);
252            } else {
253                generator = KeyPairGenerator.getInstance("EC");
254            }
255
256            generator.initialize(ecParameterSpec);
257            return generator.generateKeyPair();
258        } catch (NoSuchAlgorithmException | InvalidAlgorithmParameterException e) {
259            throw new JOSEException("Couldn't generate ephemeral EC key pair: " + e.getMessage(), e);
260        }
261    }
262}