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/*
* nimbus-jose-jwt
*
* Copyright 2012-2021, Connect2id Ltd and contributors.
*
* 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.impl;
import com.google.crypto.tink.subtle.XChaCha20Poly1305;
import com.nimbusds.jose.JOSEException;
import com.nimbusds.jose.util.ByteUtils;
import com.nimbusds.jose.util.Container;
import net.jcip.annotations.ThreadSafe;
import javax.crypto.*;
import java.security.*;
/**
* This class defines the XChaCha20 stream cipher as well as the use of the Poly1305 authenticator.
*
* The eXtended-nonce ChaCha cipher construction (XChaCha) allows for
* ChaCha-based cipher suites to accept a 192-bit nonce with similar guarantees
* to the original construction, except with a much lower probability of nonce
* misuse occurring.
*
* This class is thread-safe.
*
* @see XChaCha:
* eXtended-nonce ChaCha and AEAD_XChaCha20_Poly1305
*
*
* @author Alexander Martynov
* @version 2021-08-04
*/
@ThreadSafe
public class XC20P {
/**
* The standard authentication tag length (128 bits).
*/
public static final int AUTH_TAG_BIT_LENGTH = 128;
/**
* The standard Initialisation Vector (IV) length (192 bits).
*/
public static final int IV_BIT_LENGTH = 192;
/**
* Encrypts the specified plain text using XChaCha20_Poly1305.
*
* @param secretKey The AES key. Must not be {@code null}.
* @param plainText The plain text. Must not be {@code null}.
* @param ivContainer The initialisation vector (IV).
* This is output parameter. On output, it carries
* the nonce the cipher actually used.
* @param authData The authenticated data. Must not be {@code null}.
*
* @return The authenticated cipher text.
*
* @throws JOSEException If encryption failed.
*/
public static AuthenticatedCipherText encryptAuthenticated(final SecretKey secretKey,
final Container ivContainer,
final byte[] plainText,
final byte[] authData)
throws JOSEException {
final XChaCha20Poly1305 aead;
try {
aead = new XChaCha20Poly1305(secretKey.getEncoded());
} catch (InvalidKeyException e) {
throw new JOSEException("Invalid XChaCha20Poly1305 key: " + e.getMessage(), e);
}
final byte[] cipherOutput;
try {
cipherOutput = aead.encrypt(plainText, authData);
} catch (GeneralSecurityException e) {
throw new JOSEException("Couldn't encrypt with XChaCha20Poly1305: " + e.getMessage(), e);
}
final int tagPos = cipherOutput.length - ByteUtils.byteLength(AUTH_TAG_BIT_LENGTH);
final int cipherTextPos = ByteUtils.byteLength(IV_BIT_LENGTH);
byte[] iv = ByteUtils.subArray(cipherOutput, 0, cipherTextPos);
byte[] cipherText = ByteUtils.subArray(cipherOutput, cipherTextPos, tagPos - cipherTextPos);
byte[] authTag = ByteUtils.subArray(cipherOutput, tagPos, ByteUtils.byteLength(AUTH_TAG_BIT_LENGTH));
// set nonce
ivContainer.set(iv);
return new AuthenticatedCipherText(cipherText, authTag);
}
/**
* Decrypts the specified cipher text using XChaCha20_Poly1305.
*
* @param secretKey The AES key. Must not be {@code null}.
* @param iv The initialisation vector (IV). Must not be
* {@code null}.
* @param cipherText The cipher text. Must not be {@code null}.
* @param authData The authenticated data. Must not be {@code null}.
* @param authTag The authentication tag. Must not be {@code null}.
*
* @return The decrypted plain text.
*
* @throws JOSEException If decryption failed.
*/
public static byte[] decryptAuthenticated(final SecretKey secretKey,
final byte[] iv,
final byte[] cipherText,
final byte[] authData,
final byte[] authTag)
throws JOSEException {
final XChaCha20Poly1305 aead;
try {
aead = new XChaCha20Poly1305(secretKey.getEncoded());
} catch (InvalidKeyException e) {
throw new JOSEException("Invalid XChaCha20Poly1305 key: " + e.getMessage(), e);
}
final byte[] cipherInput = ByteUtils.concat(iv, cipherText, authTag);
try {
return aead.decrypt(cipherInput, authData);
} catch (GeneralSecurityException e) {
throw new JOSEException("XChaCha20Poly1305decryption failed: " + e.getMessage(), e);
}
}
}