90 lines
2.7 KiB
C#
90 lines
2.7 KiB
C#
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using System;
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using System.Collections.Generic;
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namespace Lidgren.Network
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{
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/// <summary>
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/// Base for a non-threadsafe encryption class
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/// </summary>
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public abstract class NetBlockEncryptionBase : NetEncryption
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{
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// temporary space for one block to avoid reallocating every time
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private byte[] m_tmp;
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/// <summary>
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/// Block size in bytes for this cipher
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/// </summary>
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public abstract int BlockSize { get; }
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/// <summary>
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/// NetBlockEncryptionBase constructor
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/// </summary>
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public NetBlockEncryptionBase(NetPeer peer)
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: base(peer)
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{
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m_tmp = new byte[BlockSize];
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}
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/// <summary>
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/// Encrypt am outgoing message with this algorithm; no writing can be done to the message after encryption, or message will be corrupted
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/// </summary>
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public override bool Encrypt(NetOutgoingMessage msg)
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{
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int payloadBitLength = msg.LengthBits;
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int numBytes = msg.LengthBytes;
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int blockSize = BlockSize;
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int numBlocks = (int)Math.Ceiling((double)numBytes / (double)blockSize);
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int dstSize = numBlocks * blockSize;
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msg.EnsureBufferSize(dstSize * 8 + (4 * 8)); // add 4 bytes for payload length at end
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msg.LengthBits = dstSize * 8; // length will automatically adjust +4 bytes when payload length is written
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for(int i=0;i<numBlocks;i++)
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{
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EncryptBlock(msg.m_data, (i * blockSize), m_tmp);
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Buffer.BlockCopy(m_tmp, 0, msg.m_data, (i * blockSize), m_tmp.Length);
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}
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// add true payload length last
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msg.Write((UInt32)payloadBitLength);
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return true;
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}
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/// <summary>
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/// Decrypt an incoming message encrypted with corresponding Encrypt
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/// </summary>
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/// <param name="msg">message to decrypt</param>
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/// <returns>true if successful; false if failed</returns>
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public override bool Decrypt(NetIncomingMessage msg)
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{
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int numEncryptedBytes = msg.LengthBytes - 4; // last 4 bytes is true bit length
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int blockSize = BlockSize;
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int numBlocks = numEncryptedBytes / blockSize;
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if (numBlocks * blockSize != numEncryptedBytes)
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return false;
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for (int i = 0; i < numBlocks; i++)
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{
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DecryptBlock(msg.m_data, (i * blockSize), m_tmp);
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Buffer.BlockCopy(m_tmp, 0, msg.m_data, (i * blockSize), m_tmp.Length);
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}
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// read 32 bits of true payload length
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uint realSize = NetBitWriter.ReadUInt32(msg.m_data, 32, (numEncryptedBytes * 8));
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msg.m_bitLength = (int)realSize;
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return true;
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}
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/// <summary>
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/// Encrypt a block of bytes
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/// </summary>
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protected abstract void EncryptBlock(byte[] source, int sourceOffset, byte[] destination);
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/// <summary>
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/// Decrypt a block of bytes
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/// </summary>
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protected abstract void DecryptBlock(byte[] source, int sourceOffset, byte[] destination);
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}
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}
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