Creating an SSL Client

Creating an SSL Client is quite simple. The Tcp component communicates with remote hosts via a SegmentedStream object (which adds "enhanced" reading/writing capability) returned by Stream (see the topic PowerTCP Secure Implementation Explained for a more in-depth explanation of the inner-workings). Simply call the methods of the Tcp component to communicate securely.

Communicate securely with the Tcp component.

This example demonstrates communicating securely with the Tcp component. In this example, the UseAuthentication property is set to false, meaning the certificate the server sends will be accepted no matter if it is valid or invalid. Doing this simplifies things but also reduces certificate control. This is addressed later in this topic.

[C#]
private void SecureTest()
{               
   // "Disable" certificate authentication (accept any certificate the server sends)
   tcp1.UseAuthentication = false;

   // Connect to a secure server.
   tcp1.Connect("myserver", 443);

   // Send secure data
   tcp1.Send("Test");

   // Close the connection
   tcp1.Close();
}  

[Visual Basic]
Private Sub SecureTest()            
   ' "Disable" certificate authentication (accept any certificate the server sends)
   Tcp1.UseAuthentication = False

   ' Connect to a secure server.
   Tcp1.Connect("myserver", 443)

   ' Send secure data
   Tcp1.Send("Test")

   ' Close the connection
   Tcp1.Close()
End Sub

Receiving certificates.

The example above demonstrates receiving certificates but is flawed, mainly because all certificates are automatically accepted. To remedy this, set UseAuthentication = true and handle which certificates are accepted/rejected in the CertificateReceived event.

[C#]
private void SecureTest()
{
   //Allow component to negotiate best security option
   tcp1.SecureProtocol = SecureProtocol.Auto;

   // Connect to a secure echo server.
   tcp1.Connect("mysecureserver", 7);

   // Send secure data
   tcp1.Send("Test");

   // Receive and display secure data
   System.Diagnostics.Debug.WriteLine(tcp1.Receive().ToString());

   // Close the connection
   tcp1.Close();
}               

private void tcp1_CertificateRequested(object sender, System.EventArgs e)
{
   //The server has requested client authentication
   //Allow the user to select a certificate
   CertificateListForm certform = new CertificateListForm(true, true);
   if(certform.ShowDialog(this) == DialogResult.OK)
      tcp1.Certificate = certform.SelectedCertificate;
}

private void tcp1_CertificateReceived(object sender, CertificateReceivedEventArgs e)
{
   //If the server's certificate is invalid for any reason,
   //the user can decide whether to proceed
   string msg = "The certificate was invalid for the following reason(s)\n";

   // Check to see if the certificate is from a trusted root.
   if(!e.TrustedRoot)
      msg+= "This certificate is not from a trusted root\n";

   // Check to see if the certificate has a valid date.
   if(!e.ValidDate)
      msg+= "This certificate does not have a valid date\n";

   // Check to see if the certificate has a valid name.
   if(!e.ValidName)
      msg+= "This certificate does not have a valid name\n";

   if(!e.Accept)
   {
      msg += "Would you like to accept this certificate anyway?";
      if(MessageBox.Show(msg, "Invalid Cert Received", MessageBoxButtons.YesNo) == DialogResult.Yes)
      e.Accept = true;
   }
}

[Visual Basic]
Private Sub SecureTest()

   'Allow component to negotiate best security option
   Tcp1.SecureProtocol = SecureProtocol.Auto

   ' Connect to a secure echo server.
   Tcp1.Connect("mysecureserver", 7)

   ' Send secure data
   Tcp1.Send("Test")

   ' Receive and display secure data
   System.Diagnostics.Debug.WriteLine(Tcp1.Receive().ToString())

   ' Close the connection
   Tcp1.Close()
End Sub

Private Sub Tcp1_CertificateRequested(ByVal sender As Object, ByVal e As System.EventArgs) Handles Tcp1.CertificateRequested
   'The server has requested client authentication
   'Allow the user to select a certificate
   Dim certform As New CertificateListForm(True, True)
   If (certform.ShowDialog(Me) = DialogResult.OK) Then
      Tcp1.Certificate = certform.SelectedCertificate
   End If
End Sub

Private Sub Tcp1_CertificateReceived(ByVal sender As Object, ByVal e As Dart.PowerTCP.SslSockets.CertificateReceivedEventArgs) Handles Tcp1.CertificateReceived
   'If the server's certificate is invalid for any reason,
   'the user can decide whether to proceed
   Dim msg As String = "The certificate was invalid for the following reason(s)" + vbLf

   ' Check to see if the certificate is from a trusted root.
   If (Not e.TrustedRoot) Then
      msg += "This certificate is not from a trusted root" + vbLf
   End If

   ' Check to see if the certificate has a valid date.
   If (Not e.ValidDate) Then
      msg += "This certificate does not have a valid date" + vbLf
   End If

   ' Check to see if the certificate has a valid name.
   If (Not e.ValidName) Then
      msg += "This certificate does not have a valid name" + vbLf
   End If

   If (Not e.Accept) Then
      msg += "Would you like to accept this certificate anyway?"
      If (MessageBox.Show(msg, "Invalid Cert Received", MessageBoxButtons.YesNo) = DialogResult.Yes) Then
         e.Accept = True
      End If
   End If
End Sub

In This Section

Security Overview: Provides an overview of basic security concepts such as digital certificates and authentication.
PowerTCP Secure Implementation Explained: Discusses how security is implemented in PowerTCP SSL Sockets for .NET
Creating an SSL Client: Discusses how to create an SSL Client using the Tcp component.
Creating an SSL Server: Discusses how to create an SSL Server using the Server component.
Using the CertificateListForm Object: Demonstrates how to use the CertificateListForm to assist users in selecting a certificate.
Using MMC to Manage SSL Certificates: Discusses how to use the Microsoft Management Console to manage SSL certificates.
Simple Encryption/Decryption: Demonstrates how to use the SymmetricCryptoStream to encrypt/decrypt stream-based data.
Windows 95/98 Security Compatibility: Discusses compatibility issues with Windows 95 and 98.

Send comments on this topic.

Documentation version 1.1.2.0.