I have recently been trying to make a SSL encrypted Server/Client in C#.
I have followed this tutorial on MSDN, however, it required a certificate to be created for the server and client usage using makecert.exe so I found an example and it created the certificate fine:
makecert -sr LocalMachine -ss My -n "CN=Test" -sky exchange -sk 123456 c:/Test.cer
but now the problem is the server starts and waits for clients, when the client connects it uses the machine name which as far as I can gather is my IP in this case:
127.0.0.1
, and then it requires the servers name which must match the servers name on the certificate (Test.cer). I have tried multiple combinations (such as "Test" "LocalMachine","127.0.0.1" but cant seem to get the clients given server name to match thus allowing the connection. The error I get is:
Certificate error: RemoteCertificateNameMismatch, RemoteCertificateChainErrors Exception: the remote certificate is invalid according to the validation procedure
here is the code I'm using it differs from the MSDN example only in the fact that I assign the certificate path for the server in the app and the machine name and server name of the client too:
SslTcpServer.cs
using System;
using System.Collections;
using System.Net;
using System.Net.Sockets;
using System.Net.Security;
using System.Security.Authentication;
using System.Text;
using System.Security.Cryptography.X509Certificates;
using System.IO;
namespace Examples.System.Net
{
public sealed class SslTcpServer
{
static X509Certificate serverCertificate = null;
// The certificate parameter specifies the name of the file
// containing the machine certificate.
public static void RunServer(string certificate)
{
serverCertificate = X509Certificate.CreateFromCertFile(certificate);
// Create a TCP/IP (IPv4) socket and listen for incoming connections.
TcpListener listener = new TcpListener(IPAddress.Any, 8080);
listener.Start();
while (true)
{
Console.WriteLine("Waiting for a client to connect...");
// Application blocks while waiting for an incoming connection.
// Type CNTL-C to terminate the server.
TcpClient client = listener.AcceptTcpClient();
ProcessClient(client);
}
}
static void ProcessClient(TcpClient client)
{
// A client has connected. Create the
// SslStream using the client's network stream.
SslStream sslStream = new SslStream(
client.GetStream(), false);
// Authenticate the server but don't require the client to authenticate.
try
{
sslStream.AuthenticateAsServer(serverCertificate,
false, SslProtocols.Tls, true);
// Display the properties and settings for the authenticated stream.
DisplaySecurityLevel(sslStream);
DisplaySecurityServices(sslStream);
DisplayCertificateInformation(sslStream);
DisplayStreamProperties(sslStream);
// Set timeouts for the read and write to 5 seconds.
sslStream.ReadTimeout = 5000;
sslStream.WriteTimeout = 5000;
// Read a message from the client.
Console.WriteLine("Waiting for client message...");
string messageData = ReadMessage(sslStream);
Console.WriteLine("Received: {0}", messageData);
// Write a message to the client.
byte[] message = Encoding.UTF8.GetBytes("Hello from the server.<EOF>");
Console.WriteLine("Sending hello message.");
sslStream.Write(message);
}
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
{
// The client stream will be closed with the sslStream
// because we specified this behavior when creating
// the sslStream.
sslStream.Close();
client.Close();
}
}
static string ReadMessage(SslStream sslStream)
{
// Read the message sent by the client.
// The client signals the end of the message using the
// "<EOF>" marker.
byte[] buffer = new byte[2048];
StringBuilder messageData = new StringBuilder();
int bytes = -1;
do
{
// Read the client's test message.
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 or an empty message.
if (messageData.ToString().IndexOf("<EOF>") != -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.");
}
// Display the properties of the client's certificate.
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.");
}
}
public static void Main(string[] args)
{
string certificate = "c:/Test.cer";
SslTcpServer.RunServer(certificate);
}
}
}
SslTcpClient.cs
using System;
using System.Collections;
using System.Net;
using System.Net.Security;
using System.Net.Sockets;
using System.Security.Authentication;
using System.Text;
using System.Security.Cryptography.X509Certificates;
using System.IO;
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, string serverName)
{
// Create a TCP/IP client socket.
// machineName is the host running the server application.
TcpClient client = new TcpClient(machineName, 8080);
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.
try
{
sslStream.AuthenticateAsClient(serverName);
}
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);
// 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();
}
public static void Main(string[] args)
{
string serverCertificateName = null;
string machineName = null;
/*
// User can specify the machine name and server name.
// Server name must match the name on the server's certificate.
machineName = args[0];
if (args.Length < 2)
{
serverCertificateName = machineName;
}
else
{
serverCertificateName = args[1];
}*/
machineName = "127.0.0.1";
serverCertificateName = "David-PC";// tried Test, LocalMachine and 127.0.0.1
SslTcpClient.RunClient(machineName, serverCertificateName);
Console.ReadKey();
}
}
}
EDIT:
The server accepts the clients connection and everything but it times out while waiting for the client to send a message. (The client wont authenticate with server due to the server name in the certificate being different from the one I supplied in the client) well thats my thoughts on it just to clarify
UPDATE:
According to an answer I have changed the certficiate maker to:
makecert -sr LocalMachine -ss My -n "CN=localhost" -sky exchange -sk 123456 c:/Test.cer and in my client I have:
machineName = "127.0.0.1";
serverCertificateName = "localhost";// tried Test, LocalMachine and 127.0.0.1
SslTcpClient.RunClient(machineName, serverCertificateName);
now I get the exception:
RemoteCertificateChainErrors Exception: the remote certificate is invalid according to the validation procedure
which is occuring here:
// The server name must match the name on the server certificate.
try
{
sslStream.AuthenticateAsClient(serverName);
}
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. "+ e.Message);
client.Close();
return;
}
