Support cipher chacha20-poly1305@openssh.com (#682)

* Added cipher chacha20-poly1305@openssh.com

* Small refactoring and remove mutable static buffer

Co-authored-by: Jeroen van Erp <jeroen@hierynomus.com>

src/main/java/net/schmizz/sshj/transport/Decoder.java

@@ -145,6 +145,7 @@ final class Decoder
     }
 
     private int decryptLengthAAD() throws TransportException {
+        cipher.setSequenceNumber(seq + 1 & 0xffffffffL);
         cipher.updateAAD(inputBuffer.array(), 0, 4);
 
         final int len;
@@ -185,10 +186,6 @@ final class Decoder
         }
     }
 
-//    private void decryptPayload(final byte[] data, int offset, int length) {
-//        cipher.update(data, cipherSize, packetLength + 4 - cipherSize);
-//    }
-
     /**
      * Adds {@code len} bytes from {@code b} to the decoder buffer. When a packet has been successfully decoded, hooks
      * in to {@link SSHPacketHandler#handle} of the {@link SSHPacketHandler} this decoder was initialized with.

src/main/java/net/schmizz/sshj/transport/Encoder.java

@@ -57,8 +57,6 @@ final class Encoder
      * @param buffer the buffer to encode
      *
      * @return the sequence no. of encoded packet
-     *
-     * @throws TransportException
      */
     long encode(SSHPacket buffer) {
         encodeLock.lock();
@@ -140,11 +138,12 @@ final class Encoder
         }
     }
 
-    protected void aeadOutgoingBuffer(Buffer buf, int offset, int len) {
+    protected void aeadOutgoingBuffer(Buffer<?> buf, int offset, int len) {
         if (cipher == null || cipher.getAuthenticationTagSize() == 0) {
             throw new IllegalArgumentException("AEAD mode requires an AEAD cipher");
         }
         byte[] data = buf.array();
+        cipher.setSequenceNumber(seq);
         cipher.updateWithAAD(data, offset, 4, len);
     }
 

src/main/java/net/schmizz/sshj/transport/cipher/BaseCipher.java

@@ -113,4 +113,9 @@ public abstract class BaseCipher
         updateAAD(input, offset, aadLen);
         update(input, offset + aadLen, inputLen);
     }
+
+    @Override
+    public void setSequenceNumber(long seq) {
+
+    }
 }

src/main/java/net/schmizz/sshj/transport/cipher/Cipher.java

@@ -78,4 +78,6 @@ public interface Cipher {
      * @param  inputLen  The number of bytes to update - starting at offset + aadLen
      */
     void updateWithAAD(byte[] input, int offset, int aadLen, int inputLen);
+
+    void setSequenceNumber(long seq);
 }

src/main/java/net/schmizz/sshj/transport/cipher/NoneCipher.java

@@ -73,4 +73,9 @@ public class NoneCipher
     public void updateWithAAD(byte[] input, int offset, int aadLen, int inputLen) {
 
     }
+
+    @Override
+    public void setSequenceNumber(long seq) {
+
+    }
 }