X25519Encrypter.java
/*
* nimbus-jose-jwt
*
* Copyright 2012-2016, Connect2id Ltd.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use
* this file except in compliance with the License. You may obtain a copy of the
* License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed
* under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
* CONDITIONS OF ANY KIND, either express or implied. See the License for the
* specific language governing permissions and limitations under the License.
*/
package com.nimbusds.jose.crypto;
import java.security.*;
import java.util.Arrays;
import java.util.Collections;
import java.util.Set;
import javax.crypto.SecretKey;
import com.google.crypto.tink.subtle.X25519;
import com.nimbusds.jose.*;
import com.nimbusds.jose.crypto.impl.AAD;
import com.nimbusds.jose.crypto.impl.ECDH;
import com.nimbusds.jose.crypto.impl.ECDHCryptoProvider;
import com.nimbusds.jose.jwk.Curve;
import com.nimbusds.jose.jwk.OctetKeyPair;
import com.nimbusds.jose.util.Base64URL;
import net.jcip.annotations.ThreadSafe;
/**
* Curve25519 Elliptic Curve Diffie-Hellman encrypter of
* {@link com.nimbusds.jose.JWEObject JWE objects}.
* Expects a public {@link OctetKeyPair} key with {@code "crv"} X25519.
*
* <p>See <a href="https://tools.ietf.org/html/rfc8037">RFC 8037</a>
* for more information.
*
* <p>See also {@link ECDHEncrypter} for ECDH on other curves.
*
* <p>This class is thread-safe.
*
* <p>Supports the following key management algorithms:
*
* <ul>
* <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES}
* <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES_A128KW}
* <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES_A192KW}
* <li>{@link com.nimbusds.jose.JWEAlgorithm#ECDH_ES_A256KW}
* </ul>
*
* <p>Supports the following elliptic curve:
*
* <ul>
* <li>{@link com.nimbusds.jose.jwk.Curve#X25519} (Curve25519)
* </ul>
*
* <p>Supports the following content encryption algorithms:
*
* <ul>
* <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A192CBC_HS384}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A128GCM}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A192GCM}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A256GCM}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A128CBC_HS256_DEPRECATED}
* <li>{@link com.nimbusds.jose.EncryptionMethod#A256CBC_HS512_DEPRECATED}
* <li>{@link com.nimbusds.jose.EncryptionMethod#XC20P}
* </ul>
*
* @author Tim McLean
* @author Egor Puzanov
* @version 2023-03-26
*/
@ThreadSafe
public class X25519Encrypter extends ECDHCryptoProvider implements JWEEncrypter {
/**
* The public key.
*/
private final OctetKeyPair publicKey;
/**
* Creates a new Curve25519 Elliptic Curve Diffie-Hellman encrypter.
*
* @param publicKey The public key. Must not be {@code null}.
*
* @throws JOSEException If the key subtype is not supported.
*/
public X25519Encrypter(final OctetKeyPair publicKey)
throws JOSEException {
this(publicKey, null);
}
/**
* Creates a new Curve25519 Elliptic Curve Diffie-Hellman encrypter.
*
* @param publicKey The public key. Must not be {@code null}.
* @param contentEncryptionKey The content encryption key (CEK) to use.
* If specified its algorithm must be "AES"
* or "ChaCha20" and its length must match
* the expected for the JWE encryption
* method ("enc"). If {@code null} a CEK
* will be generated for each JWE.
*
* @throws JOSEException If the key subtype is not supported.
*/
public X25519Encrypter(final OctetKeyPair publicKey, final SecretKey contentEncryptionKey)
throws JOSEException {
super(publicKey.getCurve(), contentEncryptionKey);
if (! Curve.X25519.equals(publicKey.getCurve())) {
throw new JOSEException("X25519Encrypter only supports OctetKeyPairs with crv=X25519");
}
if (publicKey.isPrivate()) {
throw new JOSEException("X25519Encrypter requires a public key, use OctetKeyPair.toPublicJWK()");
}
this.publicKey = publicKey;
}
@Override
public Set<Curve> supportedEllipticCurves() {
return Collections.singleton(Curve.X25519);
}
/**
* Returns the public key.
*
* @return The public key.
*/
public OctetKeyPair getPublicKey() {
return publicKey;
}
/**
* Encrypts the specified clear text of a {@link JWEObject JWE object}.
*
* @param header The JSON Web Encryption (JWE) header. Must specify
* a supported JWE algorithm and method. Must not be
* {@code null}.
* @param clearText The clear text to encrypt. Must not be {@code null}.
*
* @return The resulting JWE crypto parts.
*
* @throws JOSEException If the JWE algorithm or method is not
* supported or if encryption failed for some
* other internal reason.
*/
@Deprecated
public JWECryptoParts encrypt(final JWEHeader header, final byte[] clearText)
throws JOSEException {
return encrypt(header, clearText, AAD.compute(header));
}
@Override
public JWECryptoParts encrypt(final JWEHeader header, final byte[] clearText, final byte[] aad)
throws JOSEException {
// Generate ephemeral X25519 key pair
final byte[] ephemeralPrivateKeyBytes = X25519.generatePrivateKey();
final byte[] ephemeralPublicKeyBytes;
try {
ephemeralPublicKeyBytes = X25519.publicFromPrivate(ephemeralPrivateKeyBytes);
} catch (InvalidKeyException e) {
// Should never happen since we just generated this private key
throw new JOSEException(e.getMessage(), e);
}
final OctetKeyPair ephemeralPrivateKey =
new OctetKeyPair.Builder(getCurve(), Base64URL.encode(ephemeralPublicKeyBytes)).
d(Base64URL.encode(ephemeralPrivateKeyBytes)).
build();
final OctetKeyPair ephemeralPublicKey = ephemeralPrivateKey.toPublicJWK();
// Add the ephemeral public EC key to the header
JWEHeader updatedHeader = new JWEHeader.Builder(header).
ephemeralPublicKey(ephemeralPublicKey).
build();
// Derive 'Z'
SecretKey Z = ECDH.deriveSharedSecret(publicKey, ephemeralPrivateKey);
// for JWEObject we need update the AAD as well
final byte[] updatedAAD = Arrays.equals(AAD.compute(header), aad) ? AAD.compute(updatedHeader) : aad;
return encryptWithZ(updatedHeader, Z, clearText, updatedAAD);
}
}