Initial Commit

iTechSharp/srcbc/crypto/tls/TlsMac.cs

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+using System;
+using System.IO;
+
+using Org.BouncyCastle.Crypto.Digests;
+using Org.BouncyCastle.Crypto.Macs;
+using Org.BouncyCastle.Crypto.Parameters;
+
+namespace Org.BouncyCastle.Crypto.Tls
+{
+	/// <remarks>
+	/// A generic TLS MAC implementation, which can be used with any kind of
+	/// IDigest to act as an HMAC.
+	/// </remarks>
+	public class TlsMac
+	{
+		private long seqNo;
+		private HMac mac;
+
+		/**
+		* Generate a new instance of an TlsMac.
+		*
+		* @param digest    The digest to use.
+		* @param key_block A byte-array where the key for this mac is located.
+		* @param offset    The number of bytes to skip, before the key starts in the buffer.
+		* @param len       The length of the key.
+		*/
+		internal TlsMac(
+			IDigest	digest,
+			byte[]	key_block,
+			int		offset,
+			int		len)
+		{
+			this.mac = new HMac(digest);
+			KeyParameter param = new KeyParameter(key_block, offset, len);
+			this.mac.Init(param);
+			this.seqNo = 0;
+		}
+
+		/**
+		* @return The Keysize of the mac.
+		*/
+		internal int Size
+		{
+			get { return mac.GetMacSize(); }
+		}
+
+		/**
+		* Calculate the mac for some given data.
+		* <p/>
+		* TlsMac will keep track of the sequence number internally.
+		*
+		* @param type    The message type of the message.
+		* @param message A byte-buffer containing the message.
+		* @param offset  The number of bytes to skip, before the message starts.
+		* @param len     The length of the message.
+		* @return A new byte-buffer containing the mac value.
+		*/
+		internal byte[] CalculateMac(
+			short	type,
+			byte[]	message,
+			int		offset,
+			int		len)
+		{
+			try
+			{
+				MemoryStream bosMac = new MemoryStream(13 + len);
+				TlsUtilities.WriteUint64(seqNo++, bosMac);
+				TlsUtilities.WriteUint8(type, bosMac);
+				TlsUtilities.WriteVersion(bosMac);
+				TlsUtilities.WriteUint16(len, bosMac);
+				bosMac.Write(message, offset, len);
+				byte[] macData = bosMac.ToArray();
+				mac.BlockUpdate(macData, 0, macData.Length);
+				byte[] result = new byte[mac.GetMacSize()];
+				mac.DoFinal(result, 0);
+				mac.Reset();
+				return result;
+			}
+			catch (IOException)
+			{
+				// This should never happen
+				throw new InvalidOperationException("Internal error during mac calculation");
+			}
+		}
+	}
+}