i am fairly new to Network Programming and i need help with connecting a TCP Client via TLS. I was given a project that was coded already and it came with both the certificate and the public key provided. I have installed the pfx certificate on my local machine and have coded a new TCP Listener/Server and TCP Client pointing to local host as below:
The Client
static void Main(string[] args)
{
string server = "localhost";
TcpClient client = new TcpClient(server, 5997);
ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls;
//client.Connect(server, 5997);//connection without TLS - authenticating properly
using (SslStream sslStream = new SslStream(client.GetStream(), false,
new RemoteCertificateValidationCallback(ValidateServerCertificate), null))
{
try
{
var servername = "myAuthenticatingServerName";//the server name must be the same as the one on the server certificate
sslStream.AuthenticateAsClient(servername);
try
{
Console.WriteLine("Client Connected...");
// 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.");
}
catch (Exception e)
{
Console.WriteLine("Error..... " + e.StackTrace);
}
}
catch (AuthenticationException e)
{
Console.WriteLine($"Error: { e.Message}");
if (e.InnerException != null)
{
Console.WriteLine($"Inner exception: {e.InnerException.Message}");
}
Console.WriteLine("Authentication failed - closing the connection.");
client.Close();
}
catch (Exception ex)
{
Console.WriteLine($"Error: {ex.Message}");
Console.WriteLine("Authentication failed - closing the connection.");
client.Close();
}
}
client.Close();
Console.WriteLine($"Connection closed at {DateTime.Now}.");
Console.ReadLine();
}
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
{
try
{
bytes = sslStream.Read(buffer, 0, buffer.Length);
}
catch (Exception ex)
{
throw ex;
}
// 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 bool ValidateServerCertificate(object sender, X509Certificate certificate,
X509Chain chain, SslPolicyErrors sslPolicyErrors)
{
if (sslPolicyErrors == SslPolicyErrors.None)
return true;
Console.WriteLine($"Certificate error: {sslPolicyErrors}");
// Do not allow this client to communicate with unauthenticated servers.
return false;
}
The Server
public sealed class SslTcpServer
{
static X509Certificate2 serverCertificate = null;
// The certificate parameter specifies the name of the file
// containing the machine certificate.
public static void RunServer(X509Certificate2 certificate)
{
serverCertificate = 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, clientCertificateRequired: false, enabledSslProtocols: SslProtocols.Tls, checkCertificateRevocation: 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.");
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 int Main(string[] args)
{
RunServer(Certificate.GetCertificate());
return 0;
}
}
public class Certificate
{
public static X509Certificate2 GetCertificate()
{
string certificatePath = ConfigurationManager.AppSettings["certificatePath"].ToString();
var stream = File.OpenRead(certificatePath);
return new X509Certificate2(ReadStream(stream), "mypassword");
}
private static byte[] ReadStream(Stream input)
{
byte[] buffer = new byte[16 * 1024];
using (MemoryStream ms = new MemoryStream())
{
int read;
while ((read = input.Read(buffer, 0, buffer.Length)) > 0)
{
ms.Write(buffer, 0, read);
}
return ms.ToArray();
}
}
}
My problem is that the client runs properly and even Authenticates on
sslStream.AuthenticateAsClient(servername);
but the server does not pick up any connection on
TcpClient client = listener.AcceptTcpClient(); ProcessClient(client);
Am i missing something, or doing something wrong? Also, is it worth starting afresh, getting a new certificate etc?
On the server-side you are listening to port 8080 and on the client-side your are connecting to port 5997. To be more specific your server is hosting [YourIP]:8080 and your client is trying to connect to [YourIP]:5997