1 files changed, 104 insertions, 0 deletions
diff --git a/crypto/src/tls/crypto/impl/TlsNullCipher.cs b/crypto/src/tls/crypto/impl/TlsNullCipher.cs
new file mode 100644
index 000000000..3ca4951a6
--- /dev/null
+++ b/crypto/src/tls/crypto/impl/TlsNullCipher.cs
@@ -0,0 +1,104 @@
+using System;
+using System.IO;
+
+namespace Org.BouncyCastle.Tls.Crypto.Impl
+{
+    /// <summary>The NULL cipher.</summary>
+    public class TlsNullCipher
+        : TlsCipher
+    {
+        protected readonly TlsCryptoParameters m_cryptoParams;
+        protected readonly TlsSuiteHmac m_readMac, m_writeMac;
+
+        /// <exception cref="IOException"/>
+        public TlsNullCipher(TlsCryptoParameters cryptoParams, TlsHmac clientMac, TlsHmac serverMac)
+        {
+            if (TlsImplUtilities.IsTlsV13(cryptoParams))
+                throw new TlsFatalAlert(AlertDescription.internal_error);
+
+            this.m_cryptoParams = cryptoParams;
+
+            int key_block_size = clientMac.MacLength + serverMac.MacLength;
+            byte[] key_block = TlsImplUtilities.CalculateKeyBlock(cryptoParams, key_block_size);
+
+            int offset = 0;
+
+            clientMac.SetKey(key_block, offset, clientMac.MacLength);
+            offset += clientMac.MacLength;
+            serverMac.SetKey(key_block, offset, serverMac.MacLength);
+            offset += serverMac.MacLength;
+
+            if (offset != key_block_size)
+                throw new TlsFatalAlert(AlertDescription.internal_error);
+
+            if (cryptoParams.IsServer)
+            {
+                this.m_writeMac = new TlsSuiteHmac(cryptoParams, serverMac);
+                this.m_readMac = new TlsSuiteHmac(cryptoParams, clientMac);
+            }
+            else
+            {
+                this.m_writeMac = new TlsSuiteHmac(cryptoParams, clientMac);
+                this.m_readMac = new TlsSuiteHmac(cryptoParams, serverMac);
+            }
+        }
+
+        public virtual int GetCiphertextDecodeLimit(int plaintextLimit)
+        {
+            return plaintextLimit + m_writeMac.Size;
+        }
+
+        public virtual int GetCiphertextEncodeLimit(int plaintextLength, int plaintextLimit)
+        {
+            return plaintextLength + m_writeMac.Size;
+        }
+
+        public virtual int GetPlaintextLimit(int ciphertextLimit)
+        {
+            return ciphertextLimit - m_writeMac.Size;
+        }
+
+        public virtual TlsEncodeResult EncodePlaintext(long seqNo, short contentType, ProtocolVersion recordVersion,
+            int headerAllocation, byte[] plaintext, int offset, int len)
+        {
+            byte[] mac = m_writeMac.CalculateMac(seqNo, contentType, plaintext, offset, len);
+            byte[] ciphertext = new byte[headerAllocation + len + mac.Length];
+            Array.Copy(plaintext, offset, ciphertext, headerAllocation, len);
+            Array.Copy(mac, 0, ciphertext, headerAllocation + len, mac.Length);
+            return new TlsEncodeResult(ciphertext, 0, ciphertext.Length, contentType);
+        }
+
+        public virtual TlsDecodeResult DecodeCiphertext(long seqNo, short recordType, ProtocolVersion recordVersion,
+            byte[] ciphertext, int offset, int len)
+        {
+            int macSize = m_readMac.Size;
+            if (len < macSize)
+                throw new TlsFatalAlert(AlertDescription.decode_error);
+
+            int macInputLen = len - macSize;
+
+            byte[] expectedMac = m_readMac.CalculateMac(seqNo, recordType, ciphertext, offset, macInputLen);
+
+            bool badMac = !TlsUtilities.ConstantTimeAreEqual(macSize, expectedMac, 0, ciphertext, offset + macInputLen);
+            if (badMac)
+                throw new TlsFatalAlert(AlertDescription.bad_record_mac);
+
+            return new TlsDecodeResult(ciphertext, offset, macInputLen, recordType);
+        }
+
+        public virtual void RekeyDecoder()
+        {
+            throw new TlsFatalAlert(AlertDescription.internal_error);
+        }
+
+        public virtual void RekeyEncoder()
+        {
+            throw new TlsFatalAlert(AlertDescription.internal_error);
+        }
+
+        public virtual bool UsesOpaqueRecordType
+        {
+            get { return false; }
+        }
+    }
+}