[GitHub] [mina-sshd] lgoldstein commented on a change in pull request #132: [SSHD-506] Add support for RFC 5647

[GitBox <gi...@apache.org>]

lgoldstein commented on a change in pull request #132:
URL: https://github.com/apache/mina-sshd/pull/132#discussion_r439844394



##########
File path: sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java
##########
@@ -0,0 +1,104 @@
+/*
+ * 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.buffer.BufferUtils;
+import org.apache.sshd.common.util.security.SecurityUtils;
+
+public class BaseGCMCipher extends BaseCipher {
+
+    private Mode mode;
+    private CounterGCMParameterSpec parameters;
+    private SecretKey secretKey;

Review comment:
       Let's make them `protected` in the spirit of open-source and allowing others to extend this class if they want/need to.

##########
File path: sshd-common/src/main/java/org/apache/sshd/common/cipher/BaseGCMCipher.java
##########
@@ -0,0 +1,104 @@
+/*
+ * 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.buffer.BufferUtils;
+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 {
+        updateWithAAD(input, inputOffset, 0, inputLen);
+    }
+
+    @Override
+    public void updateWithAAD(byte[] input, int offset, int aadLen, int inputLen) throws Exception {
+        Cipher cipher = getCipherInstance();
+        parameters.incrementCounter();
+        cipher.init(mode == Mode.Encrypt ? Cipher.ENCRYPT_MODE : Cipher.DECRYPT_MODE, secretKey, parameters);
+        if (aadLen > 0) {
+            cipher.updateAAD(input, offset, aadLen);
+        }
+        int inputOffset = offset + aadLen;
+        if (mode == Mode.Decrypt) {
+            inputLen += getAuthenticationTagSize();
+        }
+        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;

Review comment:
       Let's make it`protected` in the spirit of open-source and allowing others to extend this class if they want/need to.




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