使用C#實現SSLSocket加密通訊

SSL Socket通訊是對socket的擴展，增加Socket通訊的數據安全性，SSL認證分為單向和雙向認證。單向認證只認證服務器端的合法性而不認證客戶端的合法性。雙向認證是同時認證服務端和客戶端。下面我分別說說使用C#實現單向認證和雙向認證的過程，並用代碼實現。

一、 單向認證

第1步：准備一個數字證書，可以使用如下腳本生成
先進入到vs2005的命令行狀態，即:
開始–>程序–>Microsoft Visual Studio 2005–>Visual Studio Tools–>Visual Studio 2005 命令提示
鍵入: makecert -r -pe -n “CN=TestServer” -ss Root -sky exchange
說明：上面的指令將在創建一個受信任的根證書，
第2步創建服務器端程序，代碼如下：

using System;
using System.ServiceModel;
using System.Net;
using System.Net.Sockets;
using System.Net.Security;
using System.Text;
using System.Security.Authentication;
using System.Security.Cryptography.X509Certificates;
using System.IdentityModel.Tokens;
using System.IdentityModel.Selectors;

namespace ConsoleApp
{
public class Program
{
static X509Certificate serverCertificate = null;
 public static void RunServer()
    {
        TcpListener listener = new TcpListener(IPAddress.Parse("192.168.1.25"), 901);
        listener.Start();
        while (true)
        {
            try
            {
                Console.WriteLine("Waiting for a client to connect...");
                TcpClient client = listener.AcceptTcpClient();
                ProcessClient(client);
            }
            catch
            {
            }
        }
    }

    static void ProcessClient(TcpClient client)
    {
        SslStream sslStream = new SslStream(client.GetStream(), false);
        try
        {
            sslStream.AuthenticateAsServer(serverCertificate, false, SslProtocols.Tls, true);
            DisplaySecurityLevel(sslStream);
            DisplaySecurityServices(sslStream);
            DisplayCertificateInformation(sslStream);
            DisplayStreamProperties(sslStream);

            sslStream.ReadTimeout = 5000;
            sslStream.WriteTimeout = 5000;
            byte[] message = Encoding.UTF8.GetBytes("Hello from the server.");
            Console.WriteLine("Sending hello message.");
            sslStream.Write(message);
            Console.WriteLine("Waiting for client message...");
            while (true)
            {
                string messageData = ReadMessage(sslStream);
                Console.WriteLine("Received: {0}", messageData);
                if (messageData.ToUpper() == "EXIT")
                    break;
            } 
        }
        catch (AuthenticationException e)
        {
            Console.WriteLine("Exception: {0}", e.Message);
            if (e.InnerException != null)
            {
                Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
            }
            Console.WriteLine("Authentication failed - closing the connection.");
            sslStream.Close();
            client.Close();
            return;
        }
        finally
        {
            sslStream.Close();
            client.Close();
        }
    }

    static string ReadMessage(SslStream sslStream)
    {
        byte[] buffer = new byte[2048];
        StringBuilder messageData = new StringBuilder();
        int bytes = -1;
        do
        {
            bytes = sslStream.Read(buffer, 0, buffer.Length);
            Decoder decoder = Encoding.UTF8.GetDecoder();
            char[] chars = new char[decoder.GetCharCount(buffer, 0, bytes)];
            decoder.GetChars(buffer, 0, bytes, chars, 0);
            messageData.Append(chars);
            if (messageData.ToString().IndexOf("") != -1)
            {
                break;
            }
        }
        while (bytes != 0);

        return messageData.ToString();
    }

    static void DisplaySecurityLevel(SslStream stream)
    {
        Console.WriteLine("Cipher: {0} strength {1}", stream.CipherAlgorithm, stream.CipherStrength);
        Console.WriteLine("Hash: {0} strength {1}", stream.HashAlgorithm, stream.HashStrength);
        Console.WriteLine("Key exchange: {0} strength {1}", stream.KeyExchangeAlgorithm, stream.KeyExchangeStrength);
        Console.WriteLine("Protocol: {0}", stream.SslProtocol);
    }

    static void DisplaySecurityServices(SslStream stream)
    {
        Console.WriteLine("Is authenticated: {0} as server? {1}", stream.IsAuthenticated, stream.IsServer);
        Console.WriteLine("IsSigned: {0}", stream.IsSigned);
        Console.WriteLine("Is Encrypted: {0}", stream.IsEncrypted);
    }

    static void DisplayStreamProperties(SslStream stream)
    {
        Console.WriteLine("Can read: {0}, write {1}", stream.CanRead, stream.CanWrite);
        Console.WriteLine("Can timeout: {0}", stream.CanTimeout);
    }

    static void DisplayCertificateInformation(SslStream stream)
    {
        Console.WriteLine("Certificate revocation list checked: {0}", stream.CheckCertRevocationStatus);

        X509Certificate localCertificate = stream.LocalCertificate;
        if (stream.LocalCertificate != null)
        {
            Console.WriteLine("Local cert was issued to {0} and is valid from {1} until {2}.",
            localCertificate.Subject,
                localCertificate.GetEffectiveDateString(),
                localCertificate.GetExpirationDateString());
        }
        else
        {
            Console.WriteLine("Local certificate is null.");
        }
        X509Certificate remoteCertificate = stream.RemoteCertificate;
        if (stream.RemoteCertificate != null)
        {
            Console.WriteLine("Remote cert was issued to {0} and is valid from {1} until {2}.",
                remoteCertificate.Subject,
                remoteCertificate.GetEffectiveDateString(),
                remoteCertificate.GetExpirationDateString());
        }
        else
        {
            Console.WriteLine("Remote certificate is null.");
        }
    }

    private static void DisplayUsage()
    {
        Console.WriteLine("To start the server specify:");
        Console.WriteLine("serverSync certificateFile.cer");
    }

    public static void Main(string[] args)
    {
        try
        {
            X509Store store = new X509Store(StoreName.Root);
            store.Open(OpenFlags.ReadWrite);
            // 檢索證書 
            X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindBySubjectName, "TestServer", false); // vaildOnly = true時搜索無結果。
            if (certs.Count == 0) return;

            serverCertificate = certs[0];
            RunServer();
            store.Close(); // 關閉存儲區。
        }
        catch (Exception ex)
        {
            Console.WriteLine(ex.Message);
        }
        Console.ReadLine();
    }
}
}

第3步，創建客戶端代碼

namespace ConsoleAppClient
{
using System;
using System.Collections;
using System.Net.Security;
using System.Net.Sockets;
using System.Security.Authentication;
using System.Text;
using System.Security.Cryptography.X509Certificates;
namespace Examples.System.Net
{
    public class SslTcpClient
    {
        private static Hashtable certificateErrors = new Hashtable();
        // The following method is invoked by the RemoteCertificateValidationDelegate.
        public static bool ValidateServerCertificate(
              object sender,
              X509Certificate certificate,
              X509Chain chain,
              SslPolicyErrors sslPolicyErrors)
        {
            if (sslPolicyErrors == SslPolicyErrors.None)
                return true;
            Console.WriteLine("Certificate error: {0}", sslPolicyErrors);
            // Do not allow this client to communicate with unauthenticated servers.
            return false;
        }

        public static void RunClient(string machineName)
        {
            // Create a TCP/IP client socket.
            // machineName is the host running the server application.
            TcpClient client = new TcpClient(machineName, 901);
            Console.WriteLine("Client connected.");
            // Create an SSL stream that will close the client's stream.
            SslStream sslStream = new SslStream(client.GetStream(), false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);
            try
            {
                sslStream.AuthenticateAsClient("TestServer");
            }
            catch (AuthenticationException e)
            {
                Console.WriteLine("Exception: {0}", e.Message);
                if (e.InnerException != null)
                {
                    Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
                }
                Console.WriteLine("Authentication failed - closing the connection.");
                client.Close();
                return;
            }
            // Encode a test message into a byte array.
            // Signal the end of the message using the "<EOF>".
            byte[] messsage = Encoding.UTF8.GetBytes("Hello from the client.<EOF>");
            // Send hello message to the server. 
            sslStream.Write(messsage);
            sslStream.Flush();
            // Read message from the server.
            string serverMessage = ReadMessage(sslStream);
            Console.WriteLine("Server says: {0}", serverMessage);

            messsage = Encoding.UTF8.GetBytes("exit");
            sslStream.Write(messsage);
            sslStream.Flush();
            // Close the client connection.
            client.Close();
            Console.WriteLine("Client closed.");
        }

        static string ReadMessage(SslStream sslStream)
        {
            // Read the  message sent by the server.
            // The end of the message is signaled using the
            // "<EOF>" marker.
            byte[] buffer = new byte[2048];
            StringBuilder messageData = new StringBuilder();
            int bytes = -1;
            do
            {
                bytes = sslStream.Read(buffer, 0, buffer.Length);

                // Use Decoder class to convert from bytes to UTF8
                // in case a character spans two buffers.
                Decoder decoder = Encoding.UTF8.GetDecoder();
                char[] chars = new char[decoder.GetCharCount(buffer, 0, bytes)];
                decoder.GetChars(buffer, 0, bytes, chars, 0);
                messageData.Append(chars);
                // Check for EOF.
                if (messageData.ToString().IndexOf("<EOF>") != -1)
                {
                    break;
                }
            } while (bytes != 0);

            return messageData.ToString();
        }

        private static void DisplayUsage()
        {
            Console.WriteLine("To start the client specify:");
            Console.WriteLine("clientSync machineName [serverName]");
            Environment.Exit(1);
        }

        public static void Main(string[] args)
        {
            string machineName = null;
            machineName = "192.168.1.25";
            try
            {
                RunClient(machineName);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.ReadLine();
        }
    }
}
}

運行效果如下圖：
導致通訊失敗可能問題如下：
1）證書沒有導入到受信任的根證書列表中；2）證書失效；3）客戶端在使用AuthenticateAsClient注冊時沒有正確使用服務器端證書名稱。

二、 雙向認證

第1步：創建所需證書，服務器端所需證書同單向認證中的創建過程
先進入到vs2005的命令行狀態，即:
開始–>程序–>Microsoft Visual Studio 2005–>Visual Studio Tools–>Visual Studio 2005 命令提示
鍵入:
makecert -r -pe -n “CN=TestClient” -ss Root -sky exchange
第2步：創建服務端程序
服務端的程序同單向認證的服務器端代碼
第3步：創建客戶端程序

namespace ConsoleAppClient
{
using System;
using System.Collections;
using System.Net.Security;
using System.Net.Sockets;
using System.Security.Authentication;
using System.Text;
using System.Security.Cryptography.X509Certificates;
namespace Examples.System.Net
{
    public class SslTcpClient
    {
        private static Hashtable certificateErrors = new Hashtable();
        // The following method is invoked by the RemoteCertificateValidationDelegate.
        public static bool ValidateServerCertificate(
              object sender,
              X509Certificate certificate,
              X509Chain chain,
              SslPolicyErrors sslPolicyErrors)
        {
            if (sslPolicyErrors == SslPolicyErrors.None)
                return true;

            Console.WriteLine("Certificate error: {0}", sslPolicyErrors);

            // Do not allow this client to communicate with unauthenticated servers.
            return false;
        }

        public static void RunClient(string machineName)
        {
            // Create a TCP/IP client socket.
            // machineName is the host running the server application.
            TcpClient client = new TcpClient(machineName, 901);
            Console.WriteLine("Client connected.");
            // Create an SSL stream that will close the client's stream.
            SslStream sslStream = new SslStream(client.GetStream(), false, new RemoteCertificateValidationCallback(ValidateServerCertificate), null);
            // The server name must match the name on the server certificate.

            X509Store store = new X509Store(StoreName.Root);
            store.Open(OpenFlags.ReadWrite);

            //// 檢索證書 
            X509Certificate2Collection certs = store.Certificates.Find(X509FindType.FindBySubjectName, "TestClient", false);                
            try
            {
                sslStream.AuthenticateAsClient("TestServer", certs, SslProtocols.Tls, false);
            }
            catch (AuthenticationException e)
            {
                Console.WriteLine("Exception: {0}", e.Message);
                if (e.InnerException != null)
                {
                    Console.WriteLine("Inner exception: {0}", e.InnerException.Message);
                }
                Console.WriteLine("Authentication failed - closing the connection.");
                client.Close();
                return;
            }
            // Encode a test message into a byte array.
            // Signal the end of the message using the "<EOF>".
            byte[] messsage = Encoding.UTF8.GetBytes("Hello from the client.<EOF>");
            // Send hello message to the server. 
            sslStream.Write(messsage);
            sslStream.Flush();
            // Read message from the server.
            string serverMessage = ReadMessage(sslStream);
            Console.WriteLine("Server says: {0}", serverMessage);

            messsage = Encoding.UTF8.GetBytes("exit");
            sslStream.Write(messsage);
            sslStream.Flush();

            // Close the client connection.
            client.Close();
            Console.WriteLine("Client closed.");
        }

        static string ReadMessage(SslStream sslStream)
        {
            // Read the  message sent by the server.
            // The end of the message is signaled using the
            // "<EOF>" marker.
            byte[] buffer = new byte[2048];
            StringBuilder messageData = new StringBuilder();
            int bytes = -1;
            do
            {
                bytes = sslStream.Read(buffer, 0, buffer.Length);

                // Use Decoder class to convert from bytes to UTF8
                // in case a character spans two buffers.
                Decoder decoder = Encoding.UTF8.GetDecoder();
                char[] chars = new char[decoder.GetCharCount(buffer, 0, bytes)];
                decoder.GetChars(buffer, 0, bytes, chars, 0);
                messageData.Append(chars);
                // Check for EOF.
                if (messageData.ToString().IndexOf("<EOF>") != -1)
                {
                    break;
                }
            } while (bytes != 0);

            return messageData.ToString();
        }

        private static void DisplayUsage()
        {
            Console.WriteLine("To start the client specify:");
            Console.WriteLine("clientSync machineName [serverName]");
            Environment.Exit(1);
        }

        public static void Main(string[] args)
        {
            string machineName = null;
            machineName = "192.168.1.25";
            try
            {
                RunClient(machineName);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.Message);
            }
            Console.ReadLine();
        }
    }
}
}