lgoldstein commented on a change in pull request #132: URL: https://github.com/apache/mina-sshd/pull/132#discussion_r429651878
########## File path: sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java ########## @@ -0,0 +1,102 @@ +/* + * Licensed to the Apache Software Foundation (ASF) under one + * or more contributor license agreements. See the NOTICE file + * distributed with this work for additional information + * regarding copyright ownership. The ASF licenses this file + * to you 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.apache.sshd.common.cipher; + +import javax.crypto.Cipher; +import javax.crypto.SecretKey; +import javax.crypto.spec.GCMParameterSpec; +import javax.crypto.spec.SecretKeySpec; + +import org.apache.sshd.common.util.security.SecurityUtils; + +public class BaseGCMCipher extends BaseCipher { + + private Mode mode; + private CounterGCMParameterSpec parameters; + private SecretKey secretKey; + + public BaseGCMCipher( + int ivsize, int authSize, int kdfSize, String algorithm, int keySize, String transformation, + int blkSize) { + super(ivsize, authSize, kdfSize, algorithm, keySize, transformation, blkSize); + } + + @Override + protected Cipher createCipherInstance(Mode mode, byte[] key, byte[] iv) throws Exception { + this.mode = mode; + secretKey = new SecretKeySpec(key, getAlgorithm()); + parameters = new CounterGCMParameterSpec(getAuthenticationTagSize() * Byte.SIZE, iv); + parameters.decrementCounter(); + return SecurityUtils.getCipher(getTransformation()); + } + + @Override + public void update(byte[] input, int inputOffset, int inputLen) throws Exception { + Cipher cipher = getCipherInstance(); + parameters.incrementCounter(); + cipher.init(mode == Mode.Encrypt ? Cipher.ENCRYPT_MODE : Cipher.DECRYPT_MODE, secretKey, parameters); + cipher.doFinal(input, inputOffset, inputLen, input, inputOffset); + } + + @Override + public void updateWithAAD(byte[] input, int aadOffset, int aadLen, int inputOffset, int inputLen) throws Exception { + Cipher cipher = getCipherInstance(); + parameters.incrementCounter(); + cipher.init(mode == Mode.Encrypt ? Cipher.ENCRYPT_MODE : Cipher.DECRYPT_MODE, secretKey, parameters); + cipher.updateAAD(input, aadOffset, aadLen); + cipher.doFinal(input, inputOffset, inputLen, input, inputOffset); + } + + /** + * Algorithm parameters for AES/GCM that assumes the IV uses an 8-byte counter field as its most significant bytes. + */ + protected static class CounterGCMParameterSpec extends GCMParameterSpec { + private final byte[] iv; + + protected CounterGCMParameterSpec(int tLen, byte[] src) { + super(tLen, src); + iv = src; + } + + protected void incrementCounter() { + for (int i = iv.length - 1; i >= iv.length - Long.BYTES; i--) { + iv[i]++; + if (iv[i] != 0) { + break; // no carry + } + } + } Review comment: Looks pretty dangerous 2's complement arithmetic - I would rather use a `decodeLong/encodeLong` method... ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: us...@infra.apache.org --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@mina.apache.org For additional commands, e-mail: dev-h...@mina.apache.org
