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.security.*; 022import java.util.Collections; 023import java.util.Set; 024import javax.crypto.SecretKey; 025 026import com.google.crypto.tink.subtle.X25519; 027import com.nimbusds.jose.*; 028import com.nimbusds.jose.crypto.impl.ECDH; 029import com.nimbusds.jose.crypto.impl.ECDHCryptoProvider; 030import com.nimbusds.jose.jwk.Curve; 031import com.nimbusds.jose.jwk.OctetKeyPair; 032import com.nimbusds.jose.util.Base64URL; 033import net.jcip.annotations.ThreadSafe; 034 035 036/** 037 * Curve25519 Elliptic Curve Diffie-Hellman encrypter of 038 * {@link com.nimbusds.jose.JWEObject JWE objects}. 039 * Expects a public {@link OctetKeyPair} key with {@code "crv"} X25519. 040 * 041 * <p>See <a href="https://tools.ietf.org/html/rfc8037">RFC 8037</a> 042 * for more information. 043 * 044 * <p>See also {@link ECDHEncrypter} for ECDH on other curves. 045 * 046 * <p>This class is thread-safe. 047 * 048 * <p>Supports the following key management algorithms: 049 * 050 * <ul> 051 * <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES} 052 * <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES_A128KW} 053 * <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES_A192KW} 054 * <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES_A256KW} 055 * </ul> 056 * 057 * <p>Supports the following elliptic curve: 058 * 059 * <ul> 060 * <li>{@link com.nimbusds.jose.jwk.Curve#X25519} (Curve25519) 061 * </ul> 062 * 063 * <p>Supports the following content encryption algorithms: 064 * 065 * <ul> 066 * <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256} 067 * <li>{@link com.nimbusds.jose.EncryptionMethod#A192CBC_HS384} 068 * <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512} 069 * <li>{@link com.nimbusds.jose.EncryptionMethod#A128GCM} 070 * <li>{@link com.nimbusds.jose.EncryptionMethod#A192GCM} 071 * <li>{@link com.nimbusds.jose.EncryptionMethod#A256GCM} 072 * <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256_DEPRECATED} 073 * <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512_DEPRECATED} 074 * </ul> 075 * 076 * @author Tim McLean 077 * @version 2018-07-12 078 */ 079@ThreadSafe 080public class X25519Encrypter extends ECDHCryptoProvider implements JWEEncrypter { 081 082 083 /** 084 * The public key. 085 */ 086 private final OctetKeyPair publicKey; 087 088 089 /** 090 * Creates a new Curve25519 Elliptic Curve Diffie-Hellman encrypter. 091 * 092 * @param publicKey The public key. Must not be {@code null}. 093 * 094 * @throws JOSEException If the key subtype is not supported. 095 */ 096 public X25519Encrypter(final OctetKeyPair publicKey) 097 throws JOSEException { 098 099 super(publicKey.getCurve()); 100 101 if (! Curve.X25519.equals(publicKey.getCurve())) { 102 throw new JOSEException("X25519Encrypter only supports OctetKeyPairs with crv=X25519"); 103 } 104 105 if (publicKey.isPrivate()) { 106 throw new JOSEException("X25519Encrypter requires a public key, use OctetKeyPair.toPublicJWK()"); 107 } 108 109 this.publicKey = publicKey; 110 } 111 112 113 @Override 114 public Set<Curve> supportedEllipticCurves() { 115 116 return Collections.singleton(Curve.X25519); 117 } 118 119 120 /** 121 * Returns the public key. 122 * 123 * @return The public key. 124 */ 125 public OctetKeyPair getPublicKey() { 126 127 return publicKey; 128 } 129 130 131 @Override 132 public JWECryptoParts encrypt(final JWEHeader header, final byte[] clearText) 133 throws JOSEException { 134 135 // Generate ephemeral X25519 key pair 136 final byte[] ephemeralPrivateKeyBytes = X25519.generatePrivateKey(); 137 final byte[] ephemeralPublicKeyBytes; 138 try { 139 ephemeralPublicKeyBytes = X25519.publicFromPrivate(ephemeralPrivateKeyBytes); 140 141 } catch (InvalidKeyException e) { 142 // Should never happen since we just generated this private key 143 throw new JOSEException(e.getMessage(), e); 144 } 145 146 final OctetKeyPair ephemeralPrivateKey = 147 new OctetKeyPair.Builder(getCurve(), Base64URL.encode(ephemeralPublicKeyBytes)). 148 d(Base64URL.encode(ephemeralPrivateKeyBytes)). 149 build(); 150 final OctetKeyPair ephemeralPublicKey = ephemeralPrivateKey.toPublicJWK(); 151 152 // Add the ephemeral public EC key to the header 153 JWEHeader updatedHeader = new JWEHeader.Builder(header). 154 ephemeralPublicKey(ephemeralPublicKey). 155 build(); 156 157 // Derive 'Z' 158 SecretKey Z = ECDH.deriveSharedSecret(publicKey, ephemeralPrivateKey); 159 160 return encryptWithZ(updatedHeader, Z, clearText); 161 } 162}