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/*
* Copyright (C) 2017 The Android Open Source Project
*
* 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 org.conscrypt;
import java.security.InvalidAlgorithmParameterException;
import java.security.InvalidKeyException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.security.spec.AlgorithmParameterSpec;
import javax.crypto.BadPaddingException;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.ShortBufferException;
import javax.crypto.spec.IvParameterSpec;
/**
* Implementation of the ChaCha20 stream cipher.
*
* @hide
*/
@Internal
public class OpenSSLCipherChaCha20 extends OpenSSLCipher {
private static final int BLOCK_SIZE_BYTES = 64;
private static final int NONCE_SIZE_BYTES = 12;
// BoringSSL's interface encrypts by the block, so we need to keep track of whether we
// had unused keystream bytes at the end of the previous encryption operation, so that
// we can use them before moving on to the next block.
private int currentBlockConsumedBytes = 0;
private int blockCounter = 0;
public OpenSSLCipherChaCha20() {}
@Override
void engineInitInternal(byte[] encodedKey, AlgorithmParameterSpec params, SecureRandom random)
throws InvalidKeyException, InvalidAlgorithmParameterException {
if (params instanceof IvParameterSpec) {
IvParameterSpec ivParams = (IvParameterSpec) params;
if (ivParams.getIV().length != NONCE_SIZE_BYTES) {
throw new InvalidAlgorithmParameterException("IV must be 12 bytes long");
}
iv = ivParams.getIV();
} else {
if (!isEncrypting()) {
throw new InvalidAlgorithmParameterException(
"IV must be specified when decrypting");
}
iv = new byte[NONCE_SIZE_BYTES];
if (random != null) {
random.nextBytes(iv);
} else {
NativeCrypto.RAND_bytes(iv);
}
}
}
@Override
int updateInternal(byte[] input, int inputOffset, int inputLen, byte[] output, int outputOffset,
int maximumLen) throws ShortBufferException {
if (inputLen > output.length - outputOffset) {
throw new ShortBufferException("Insufficient output space");
}
int inputLenRemaining = inputLen;
if (currentBlockConsumedBytes > 0) {
// A previous operation ended with a partial block, so we need to encrypt using
// the remainder of that block before beginning to use the next block
int len = Math.min(BLOCK_SIZE_BYTES - currentBlockConsumedBytes, inputLenRemaining);
byte[] singleBlock = new byte[BLOCK_SIZE_BYTES];
byte[] singleBlockOut = new byte[BLOCK_SIZE_BYTES];
System.arraycopy(input, inputOffset, singleBlock, currentBlockConsumedBytes, len);
NativeCrypto.chacha20_encrypt_decrypt(singleBlock, 0, singleBlockOut, 0,
BLOCK_SIZE_BYTES, encodedKey, iv, blockCounter);
System.arraycopy(singleBlockOut, currentBlockConsumedBytes, output, outputOffset, len);
currentBlockConsumedBytes += len;
if (currentBlockConsumedBytes < BLOCK_SIZE_BYTES) {
// We still didn't finish this block, so we're done.
return len;
}
assert currentBlockConsumedBytes == BLOCK_SIZE_BYTES;
currentBlockConsumedBytes = 0;
inputOffset += len;
outputOffset += len;
inputLenRemaining -= len;
blockCounter++;
}
NativeCrypto.chacha20_encrypt_decrypt(input, inputOffset, output,
outputOffset, inputLenRemaining, encodedKey, iv, blockCounter);
currentBlockConsumedBytes = inputLenRemaining % BLOCK_SIZE_BYTES;
blockCounter += inputLenRemaining / BLOCK_SIZE_BYTES;
return inputLen;
}
@Override
int doFinalInternal(byte[] output, int outputOffset, int maximumLen)
throws IllegalBlockSizeException, BadPaddingException, ShortBufferException {
reset();
return 0;
}
private void reset() {
blockCounter = 0;
currentBlockConsumedBytes = 0;
}
@Override
String getBaseCipherName() {
return "ChaCha20";
}
@Override
void checkSupportedKeySize(int keySize) throws InvalidKeyException {
if (keySize != 32) {
throw new InvalidKeyException("Unsupported key size: " + keySize
+ " bytes (must be 32)");
}
}
@Override
void checkSupportedMode(Mode mode) throws NoSuchAlgorithmException {
if (mode != Mode.NONE) {
throw new NoSuchAlgorithmException("Mode must be NONE");
}
}
@Override
void checkSupportedPadding(Padding padding) throws NoSuchPaddingException {
if (padding != Padding.NOPADDING) {
throw new NoSuchPaddingException("Must be NoPadding");
}
}
@Override
int getCipherBlockSize() {
return 0;
}
@Override
int getOutputSizeForFinal(int inputLen) {
return inputLen;
}
@Override
int getOutputSizeForUpdate(int inputLen) {
return inputLen;
}
}
