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Lidgren.Network/Encryption/NetRC2Encryption.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Security.Cryptography;
+using System.Text;
+
+namespace Lidgren.Network
+{
+	/// <summary>
+	/// RC2 encryption
+	/// </summary>
+	public class NetRC2Encryption : INetEncryption
+	{
+		private readonly byte[] m_key;
+		private readonly byte[] m_iv;
+		private readonly int m_bitSize;
+		private static readonly List<int> m_keysizes;
+		private static readonly List<int> m_blocksizes;
+
+		static NetRC2Encryption()
+		{
+
+			RC2CryptoServiceProvider rc2 = new RC2CryptoServiceProvider();
+			List<int> temp = new List<int>();
+			foreach (KeySizes keysize in rc2.LegalKeySizes)
+			{
+				for (int i = keysize.MinSize; i <= keysize.MaxSize; i += keysize.SkipSize)
+				{
+					if (!temp.Contains(i))
+						temp.Add(i);
+					if (i == keysize.MaxSize)
+						break;
+				}
+			}
+			m_keysizes = temp;
+			temp = new List<int>();
+			foreach (KeySizes keysize in rc2.LegalBlockSizes)
+			{
+				for (int i = keysize.MinSize; i <= keysize.MaxSize; i += keysize.SkipSize)
+				{
+
+					if (!temp.Contains(i))
+						temp.Add(i);
+					if (i == keysize.MaxSize)
+						break;
+				}
+			}
+			m_blocksizes = temp;
+		}
+
+		/// <summary>
+		/// NetRC2Encryption constructor
+		/// </summary>
+		public NetRC2Encryption(byte[] key, byte[] iv)
+		{
+			if (!m_keysizes.Contains(key.Length * 8))
+				throw new NetException(string.Format("Not a valid key size. (Valid values are: {0})", NetUtility.MakeCommaDelimitedList(m_keysizes)));
+
+			if (!m_blocksizes.Contains(iv.Length * 8))
+				throw new NetException(string.Format("Not a valid iv size. (Valid values are: {0})", NetUtility.MakeCommaDelimitedList(m_blocksizes)));
+
+			m_key = key;
+			m_iv = iv;
+			m_bitSize = m_key.Length * 8;
+		}
+
+		/// <summary>
+		/// NetRC2Encryption constructor
+		/// </summary>
+		public NetRC2Encryption(string key, int bitsize)
+		{
+			if (!m_keysizes.Contains(bitsize))
+				throw new NetException(string.Format("Not a valid key size. (Valid values are: {0})", NetUtility.MakeCommaDelimitedList(m_keysizes)));
+				
+			byte[] entropy = Encoding.UTF32.GetBytes(key);
+			// I know hardcoding salts is bad, but in this case I think it is acceptable.
+			HMACSHA512 hmacsha512 = new HMACSHA512(Convert.FromBase64String("i88NEiez3c50bHqr3YGasDc4p8jRrxJAaiRiqixpvp4XNAStP5YNoC2fXnWkURtkha6M8yY901Gj07IRVIRyGL=="));
+			hmacsha512.Initialize();
+			for (int i = 0; i < 1000; i++)
+			{
+				entropy = hmacsha512.ComputeHash(entropy);
+			}
+			int keylen = bitsize / 8;
+			m_key = new byte[keylen];
+			Buffer.BlockCopy(entropy, 0, m_key, 0, keylen);
+			m_iv = new byte[m_blocksizes[0] / 8];
+
+			Buffer.BlockCopy(entropy, entropy.Length - m_iv.Length - 1, m_iv, 0, m_iv.Length);
+			m_bitSize = bitsize;
+		}
+
+		/// <summary>
+		/// NetRC2Encryption constructor
+		/// </summary>
+		/// <param name="key"></param>
+		public NetRC2Encryption(string key)
+			: this(key, m_keysizes[0])
+		{
+		}
+
+		/// <summary>
+		/// Encrypt outgoing message
+		/// </summary>
+		public bool Encrypt(NetOutgoingMessage msg)
+		{
+			try
+			{
+				// nested usings are fun!
+				using (RC2CryptoServiceProvider rc2CryptoServiceProvider = new RC2CryptoServiceProvider { KeySize = m_bitSize, Mode = CipherMode.CBC })
+				{
+					using (ICryptoTransform cryptoTransform = rc2CryptoServiceProvider.CreateEncryptor(m_key, m_iv))
+					{
+						using (MemoryStream memoryStream = new MemoryStream())
+						{
+							using (CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoTransform,
+																			 CryptoStreamMode.Write))
+							{
+								cryptoStream.Write(msg.m_data, 0, msg.m_data.Length);
+							}
+							msg.m_data = memoryStream.ToArray();
+						}
+					}
+				}
+
+			}
+			catch
+			{
+				return false;
+			}
+			return true;
+		}
+
+		/// <summary>
+		/// Decrypt incoming message
+		/// </summary>
+		public bool Decrypt(NetIncomingMessage msg)
+		{
+			try
+			{
+				// nested usings are fun!
+				using (RC2CryptoServiceProvider rc2CryptoServiceProvider = new RC2CryptoServiceProvider { KeySize = m_bitSize, Mode = CipherMode.CBC })
+				{
+					using (ICryptoTransform cryptoTransform = rc2CryptoServiceProvider.CreateDecryptor(m_key, m_iv))
+					{
+						using (MemoryStream memoryStream = new MemoryStream())
+						{
+							using (CryptoStream cryptoStream = new CryptoStream(memoryStream, cryptoTransform,
+																			 CryptoStreamMode.Write))
+							{
+								cryptoStream.Write(msg.m_data, 0, msg.m_data.Length);
+							}
+							msg.m_data = memoryStream.ToArray();
+						}
+					}
+				}
+
+			}
+			catch
+			{
+				return false;
+			}
+			return true;
+		}
+	}
+}