Restore CbcCipherMode

Author: scott-xu

src/Renci.SshNet/Security/Cryptography/Ciphers/Modes/CbcCipherMode.cs

@@ -0,0 +1,100 @@
+using System;
+using System.Globalization;
+
+namespace Renci.SshNet.Security.Cryptography.Ciphers.Modes
+{
+    /// <summary>
+    /// Implements CBC cipher mode.
+    /// </summary>
+    public class CbcCipherMode : CipherMode
+    {
+        /// <summary>
+        /// Initializes a new instance of the <see cref="CbcCipherMode"/> class.
+        /// </summary>
+        /// <param name="iv">The iv.</param>
+        public CbcCipherMode(byte[] iv)
+            : base(iv)
+        {
+        }
+
+        /// <summary>
+        /// Encrypts the specified region of the input byte array and copies the encrypted data to the specified region of the output byte array.
+        /// </summary>
+        /// <param name="inputBuffer">The input data to encrypt.</param>
+        /// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
+        /// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
+        /// <param name="outputBuffer">The output to which to write encrypted data.</param>
+        /// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
+        /// <returns>
+        /// The number of bytes encrypted.
+        /// </returns>
+        public override int EncryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
+        {
+            if (inputBuffer.Length - inputOffset < _blockSize)
+            {
+                throw new ArgumentException("Invalid input buffer");
+            }
+
+            if (outputBuffer.Length - outputOffset < _blockSize)
+            {
+                throw new ArgumentException("Invalid output buffer");
+            }
+
+            if (inputCount != _blockSize)
+            {
+                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "inputCount must be {0}.", _blockSize));
+            }
+
+            for (var i = 0; i < _blockSize; i++)
+            {
+                IV[i] ^= inputBuffer[inputOffset + i];
+            }
+
+            _ = Cipher.EncryptBlock(IV, 0, inputCount, outputBuffer, outputOffset);
+
+            Buffer.BlockCopy(outputBuffer, outputOffset, IV, 0, IV.Length);
+
+            return _blockSize;
+        }
+
+        /// <summary>
+        /// Decrypts the specified region of the input byte array and copies the decrypted data to the specified region of the output byte array.
+        /// </summary>
+        /// <param name="inputBuffer">The input data to decrypt.</param>
+        /// <param name="inputOffset">The offset into the input byte array from which to begin using data.</param>
+        /// <param name="inputCount">The number of bytes in the input byte array to use as data.</param>
+        /// <param name="outputBuffer">The output to which to write decrypted data.</param>
+        /// <param name="outputOffset">The offset into the output byte array from which to begin writing data.</param>
+        /// <returns>
+        /// The number of bytes decrypted.
+        /// </returns>
+        public override int DecryptBlock(byte[] inputBuffer, int inputOffset, int inputCount, byte[] outputBuffer, int outputOffset)
+        {
+            if (inputBuffer.Length - inputOffset < _blockSize)
+            {
+                throw new ArgumentException("Invalid input buffer");
+            }
+
+            if (outputBuffer.Length - outputOffset < _blockSize)
+            {
+                throw new ArgumentException("Invalid output buffer");
+            }
+
+            if (inputCount != _blockSize)
+            {
+                throw new ArgumentException(string.Format(CultureInfo.CurrentCulture, "inputCount must be {0}.", _blockSize));
+            }
+
+            _ = Cipher.DecryptBlock(inputBuffer, inputOffset, inputCount, outputBuffer, outputOffset);
+
+            for (var i = 0; i < _blockSize; i++)
+            {
+                outputBuffer[outputOffset + i] ^= IV[i];
+            }
+
+            Buffer.BlockCopy(inputBuffer, inputOffset, IV, 0, IV.Length);
+
+            return _blockSize;
+        }
+    }
+}