原文链接
前面两部分分别讲解了如何在.net程序中使用SSL实现安全通信以及SSL的通信过程，并通过抓包工具具体分析了ssl的握手过程，本文通过一个demo来模拟ssl协议，在TCP之上实现自己的安全通信。
创建证书
为了实现安全的通信，必须使用证书对传输的数据进行加密，有两种方法可以得到证书，一是安装CA服务器，使用CA来发放证书，二是通过makecert.exe工具自己创建。
创建服务器证书：
cmd>makecert.exe -r -pe -n "CN=MySslServer" -sky Exchange -ss My
创建客户端证书
cmd>makecert.exe -r -pe -n "CN=MySslClient" -sky Exchange -ss My
关于makecert.exe的更多信息可以操作这里。
建立TCP连接
使用普通的Socket类来建立TCP连接即可。后续的握手，传输数据都是在TCP之上的，在这里，定义每条信息的第一个字节是类型，0x01是整数，0x02是session key，0x03是应用层数据，0x04是错误信息，未使用。
我们知道TCP通信是stream的，消息没有边界，有可能发送方发送的数据，在接收方两次才能接收完，或者发送方连续发送两次数据，接收方一次就全部接受，这就要求应用层自己对消息的边界进行区分，常用的有3种方法，一是固定长度，所有消息长度一样，不够就填充，显然不够实用而且浪费带宽；二是定义消息边界，每条消息以固定字节流结尾如，如果传输的数据刚好含有这样的字节流，就必须进行转义；三是消息的起始处使用固定字节来描述本消息的长度。本文为方便起见，没有进行消息边界处理，每两次发送有个间隔。
交换证书
在TCP连接建立之后，开始进行握手过程，主要是交换证书，交换session key。
server与client各自将自己的证书发送给对方，证书被export成.cer格式，只含有public key。证书的作用一是交换session key，二是发送数据时签名。
1 byte [] certBytes = so.localCert.Export(X509ContentType.Cert); 2 byte [] sentBytes = AddType(certBytes, type); 3 so.workSocket.Send(sentBytes, 0 , sentBytes.Length, SocketFlags.None); 4 Console.WriteLine( " Send>>>>>>>>>>>>>>>>>>>>> " ); 5 PrintCert(so.localCert); 6 。。。。。。 7 byte [] data = RemoveType(so.buffer, read); 8 so.remoteCert = new X509Certificate2(data); 9 Console.WriteLine( " Recv<<<<<<<<<<<<<<<<<<<<<< " ); 10 PrintCert(so.remoteCert);
交换session key
本demo使用DES对称算法来加密，必须在发送应用层数据之前交换算法的key，使用双方约定固定的IV。
其中一方生成随机的key，用对方的证书加密，调用RSA的Encrypt方法，会使用Public key，将加密后的数据发送给对方，由于只有对方才有证书的private key，所以也只有对方才能解密出key，第三方即使中途截获了数据也不能破解出key。
生成session key 1 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)so.remoteCert.PublicKey.Key; 2 byte [] encrypedSessionKey = rsa.Encrypt(so.localSessionKey, false ); 3 byte [] sentBytes = AddType(encrypedSessionKey, type); 4 so.workSocket.Send(sentBytes, 0 , sentBytes.Length, SocketFlags.None); 5 Console.WriteLine( " Send>>>>>>>>>>>>>>>>>>>>> " ); 6 PrintSessionKey(so.localSessionKey);
解析session key 1 byte [] data = RemoveType(so.buffer, read); 2 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)so.localCert.PrivateKey; 3 so.remoteSessionKey = rsa.Decrypt(data, false ); 4 Console.WriteLine( " Recv<<<<<<<<<<<<<<<<<<<<<< " ); 5 PrintSessionKey(so.remoteSessionKey);
发送加密和签名数据
发送数据使用DES算法加密，防止被第三方截获；同时对发送的数据签名，让对方确认数据没有被篡改并且确认数据是自己发送的。
数据格式:
0x03
密文长度
密文
签名长度
签名
密文使用DES算法机密得到。 对原文使用hash算法，并使用自己的证明对hash进行签名，签名是使用的private key，接收方收到数据后，用DES解密出原文，对原文计算hash，然后对收到的签名使用对方的证书的public key还原，比较与hash是否一致。 加密数据并签名 1 MemoryStream memoryStream = new MemoryStream(); 2 3 // encrypt 4 DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 5 ICryptoTransform cTransform = des.CreateEncryptor(so.remoteSessionKey, new byte [ 8 ]); 6 MemoryStream ms = new MemoryStream(); 7 CryptoStream encStream = new CryptoStream(ms, cTransform, CryptoStreamMode.Write); 8 encStream.Write(so.sentData, 0 , so.sentData.Length); 9 encStream.FlushFinalBlock(); 10 11 byte [] temp = ms.ToArray(); 12 memoryStream.Write(BitConverter.GetBytes(temp.Length), 0 , 4 ); 13 memoryStream.Write(temp, 0 , temp.Length); 14 15 // hash 16 MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); 17 byte [] hash = md5.ComputeHash(so.sentData); 18 19 // sign 20 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider) so.localCert.PrivateKey; 21 byte [] sign = rsa.SignHash(hash, CryptoConfig.MapNameToOID( " MD5 " )); 22 23 memoryStream.Write(BitConverter.GetBytes(sign.Length), 0 , 4 ); 24 memoryStream.Write(sign, 0 , sign.Length); 25 26 byte [] sentBytes = AddType(memoryStream.ToArray(), type); 27 so.workSocket.Send(sentBytes, 0 , sentBytes.Length, SocketFlags.None); 28 Console.WriteLine( " Send>>>>>>>>>>>>>>>>>>>>> " ); 29 PrintData(so.sentData);解密数据并验证 1 byte [] data = RemoveType(so.buffer, read); 2 3 // Decrypt 4 DESCryptoServiceProvider des = new DESCryptoServiceProvider(); 5 ICryptoTransform cTransform = des.CreateDecryptor(so.localSessionKey, new byte [ 8 ]); 6 int len = BitConverter.ToInt32(data, 0 ); 7 byte [] cipherText = new byte [len]; 8 Array.Copy(data, 4 , cipherText, 0 , len); 9 MemoryStream ms2 = new MemoryStream(cipherText); 10 CryptoStream decStream = new CryptoStream(ms2, cTransform, CryptoStreamMode.Read); 11 12 Byte[] tempBuffer = new Byte[ 1024 ]; 13 Byte[] outputBytes = new byte [ 0 ]; 14 int nRead = decStream.Read(tempBuffer, 0 , tempBuffer.Length); 15 int nLength = 0 ; 16 while ( 0 != nRead) 17 { 18 nLength = outputBytes.Length; 19 Array.Resize( ref outputBytes, nLength + nRead); 20 Array.Copy(tempBuffer, 0 , outputBytes, nLength, nRead); 21 nRead = decStream.Read(tempBuffer, 0 , tempBuffer.Length); 22 } 23 so.recvData = outputBytes; 24 Console.WriteLine( " Recv<<<<<<<<<<<<<<<<<<<<<< " ); 25 PrintData(so.recvData); 26 27 // hash 28 MD5CryptoServiceProvider md5 = new MD5CryptoServiceProvider(); 29 byte [] hash = md5.ComputeHash(so.recvData); 30 31 // verify 32 int signlen = BitConverter.ToInt32(data, len + 4 ); 33 byte [] sign = new byte [signlen]; 34 Array.Copy(data, 4 + len + 4 ,sign, 0 , signlen); 35 RSACryptoServiceProvider rsa = (RSACryptoServiceProvider)so.remoteCert.PublicKey.Key; 36 try 37 { 38 bool verify = rsa.VerifyHash(hash, CryptoConfig.MapNameToOID( " MD5 " ), sign); 39 if (verify) 40 { 41 Console.WriteLine( " verify correct! " ); 42 } 43 else 44 { 45 Console.WriteLine( " verify error! " ); 46 } 47 } 48 catch 49 { 50 Console.WriteLine( " verify error! " ); 51 return PackageType.Error; 52 }
运行结果 1 C:\D\BACKUP\Projects\TestProject\MySSLServer\bin\Debug > MySSLServer.exe 2 Recv <<<<<<<<<<<<<<<<<<<<<< 3 ============================================ 4 cert 5 ============================================ 6 Subject: CN = MySslClient 7 Issuer: CN = MySslClient 8 Version: 3 9 Valid Date: 7 / 7 / 2010 11 : 25 : 28 AM 10 Expiry Date: 1 / 1 / 2040 7 : 59 : 59 AM 11 Thumbprint: D9AE7CF97A254FCA05EB7B704DDC90878FC56B0C 12 Serial Number: 2500552056343D874C0B714A71CB047B 13 Friendly Name: RSA 14 Public Key Format: 30 81 89 02 81 81 00 9f 6f 17 84 0f 03 a0 8c b7 86 45 49 ba 0c c5 ab 37 c9 30 24 32 b5 dc 90 31 e4 d6 15 ea 83 45 1f c8 2d dd 2f 81 3e da 09 44 7f 2a cf bb 18 9a 92 28 d3 79 f0 33 b8 04 f2 1a 1d f8 e0 b6 f9 cc da 36 16 2b e3 16 8b 8d 82 5f 9c 88 6a 79 54 53 4f 08 10 dc b9 53 f1 c8 d4 bd 3d c4 94 71 1d db a2 76 65 8c 37 a3 cd 88 0d a0 72 0e 93 3a 17 64 62 dc 90 cf 19 3f f7 58 59 d6 bd 4e 3f a4 15 30 5b 36 75 2f 02 03 01 00 01 18 Send >>>>>>>>>>>>>>>>>>>>> 19 ============================================ 20 cert 21 ============================================ 22 Subject: CN = MySslServer 23 Issuer: CN = MySslServer 24 Version: 3 25 Valid Date: 7 / 7 / 2010 11 : 25 : 32 AM 26 Expiry Date: 1 / 1 / 2040 7 : 59 : 59 AM 27 Thumbprint: 5B1CEC828E92A64950284E557477FDD7E2C05300 28 Serial Number: 907E95210C949144FD68342B32FD07 29 Friendly Name: RSA 30 Public Key Format: 30 81 89 02 81 81 00 a4 97 38 0d dd c7 fa 6b b3 e6 23 17 df cd bf 06 c7 40 e1 5e 9a 04 81 02 62 00 b5 31 52 82 c9 6d b0 fc 16 ce e8 72 be ae 31 80 85 44 75 6c 1d 6a 2c 33 55 ee 04 6a fd f8 f4 ff 3a e0 22 28 a7 4f f8 c4 ba 96 32 c7 e6 f0 27 aa 43 09 11 ce eb cb 5e fe 63 84 ef e0 74 11 99 91 5d a0 39 5b 54 e6 74 8d db c8 ce d2 bd 08 53 63 19 3d d6 33 4c 37 99 b1 28 6a 07 2b 0c 70 49 fa df 9e ed 8b 2d e0 ed bf 03 02 03 01 00 01 34 Send >>>>>>>>>>>>>>>>>>>>> 35 ============================================ 36 session key 37 ============================================ 38 Session Key: 44 97 AC 07 5E 41 27 0B[ 8 ] 39 Recv <<<<<<<<<<<<<<<<<<<<<< 40 ============================================ 41 session key 42 ============================================ 43 Session Key: BD 28 62 18 04 90 C9 57 [ 8 ] 44 Recv <<<<<<<<<<<<<<<<<<<<<< 45 ============================================ 46 data 47 ============================================ 48 It ' s just a text. 49 verify correct ! 50 Send >>>>>>>>>>>>>>>>>>>>> 51 ============================================ 52 data 53 ============================================ 54 Response to client.
1 C:\D\BACKUP\Projects\TestProject\MySSLClient\bin\Debug > MySSLClient.exe 10.175 . 13.77 2 Send >>>>>>>>>>>>>>>>>>>>> 3 ============================================ 4 cert 5 ============================================ 6 Subject: CN = MySslClient 7 Issuer: CN = MySslClient 8 Version: 3 9 Valid Date: 7 / 7 / 2010 11 : 25 : 28 AM 10 Expiry Date: 1 / 1 / 2040 7 : 59 : 59 AM 11 Thumbprint: D9AE7CF97A254FCA05EB7B704DDC90878FC56B0C 12 Serial Number: 2500552056343D874C0B714A71CB047B 13 Friendly Name: RSA 14 Public Key Format: 30 81 89 02 81 81 00 9f 6f 17 84 0f 03 a0 8c b7 86 45 49 ba 0c c5 ab 37 c9 30 24 32 b5 dc 90 31 e4 d6 15 ea 83 45 1f c8 2d dd 2f 81 3e da 09 44 7f 2a cf bb 18 9a 92 28 d3 79 f0 33 b8 04 f2 1a 1d f8 e0 b6 f9 cc da 36 16 2b e3 16 8b 8d 82 5f 9c 88 6a 79 54 53 4f 08 10 dc b9 53 f1 c8 d4 bd 3d c4 94 71 1d db a2 76 65 8c 37 a3 cd 88 0d a0 72 0e 93 3a 17 64 62 dc 90 cf 19 3f f7 58 59 d6 bd 4e 3f a4 15 30 5b 36 75 2f 02 03 01 00 01 18 Recv <<<<<<<<<<<<<<<<<<<<<< 19 ============================================ 20 cert 21 ============================================ 22 Subject: CN = MySslServer 23 Issuer: CN = MySslServer 24 Version: 3 25 Valid Date: 7 / 7 / 2010 11 : 25 : 32 AM 26 Expiry Date: 1 / 1 / 2040 7 : 59 : 59 AM 27 Thumbprint: 5B1CEC828E92A64950284E557477FDD7E2C05300 28 Serial Number: 907E95210C949144FD68342B32FD07 29 Friendly Name: RSA 30 Public Key Format: 30 81 89 02 81 81 00 a4 97 38 0d dd c7 fa 6b b3 e6 23 17 df cd bf 06 c7 40 e1 5e 9a 04 81 02 62 00 b5 31 52 82 c9 6d b0 fc 16 ce e8 72 be ae 31 80 85 44 75 6c 1d 6a 2c 33 55 ee 04 6a fd f8 f4 ff 3a e0 22 28 a7 4f f8 c4 ba 96 32 c7 e6 f0 27 aa 43 09 11 ce eb cb 5e fe 63 84 ef e0 74 11 99 91 5d a0 39 5b 54 e6 74 8d db c8 ce d2 bd 08 53 63 19 3d d6 33 4c 37 99 b1 28 6a 07 2b 0c 70 49 fa df 9e ed 8b 2d e0 ed bf 03 02 03 01 00 01 34 Send >>>>>>>>>>>>>>>>>>>>> 35 ============================================ 36 session key 37 ============================================ 38 Session Key: BD 28 62 18 04 90 C9 57 [ 8 ] 39 Recv <<<<<<<<<<<<<<<<<<<<<< 40 ============================================ 41 session key 42 ============================================ 43 Session Key: 44 97 AC 07 5E 41 27 0B[ 8 ] 44 Send >>>>>>>>>>>>>>>>>>>>> 45 ============================================ 46 data 47 ============================================ 48 It ' s just a text. 49 Recv <<<<<<<<<<<<<<<<<<<<<< 50 ============================================ 51 data 52 ============================================ 53 Response to client. 54 verify correct !
转载于:https://www.cnblogs.com/peapon/p/7052458.html
