Pascal (Lazarus/Delphi)

TLS Connection within SSH Tunnel (Port Forwarding)

See more Socket/SSL/TLS Examples

Demonstrates using Chilkat Socket to communicate to a TLS service through an SSH tunnel. This example will connect (through a port-forwarded SSH tunnel) to the GMAIL IMAP server via TLS and will receive the greeting.

Note: The Chilkat IMAP API provides direct support for using SSH tunneling with the IMAP protocol. This example serves only to demonstrate that, in general, TLS connections can be tunneled through SSH.

Pascal (Lazarus/Delphi)

program ChilkatDemo;

// Demonstrates using the Chilkat Pascal wrapper via the C bridge DLL.
// Builds as a console application under Lazarus (FPC) or Delphi.

{$IFDEF FPC}
  {$MODE DELPHI}
{$ENDIF}
{$APPTYPE CONSOLE}

uses
  {$IFDEF UNIX}
  cthreads,
  {$ENDIF}
  SysUtils,
  CkDllLoader,
  Chilkat.Socket;

// ---------------------------------------------------------------------------

procedure RunDemo;
var
  success: Boolean;
  tunnel: TSocket;
  sshHostname: string;
  sshPort: Integer;
  channel: TSocket;
  maxWaitMs: Integer;
  useTls: Boolean;
  imapGreeting: string;

begin
  success := False;

  //  This example requires the Chilkat API to have been previously unlocked.
  //  See Global Unlock Sample for sample code.

  tunnel := TSocket.Create;

  sshHostname := 'sftp.example.com';
  sshPort := 22;

  //  Connect to an SSH server and establish the SSH tunnel:
  success := tunnel.SshOpenTunnel(sshHostname,sshPort);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  Authenticate with the SSH server via a login/password
  //  or with a public key.
  //  This example demonstrates SSH password authentication.
  success := tunnel.SshAuthenticatePw('mySshLogin','mySshPassword');
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //   OK, the SSH tunnel is setup.  Now open a channel within the tunnel.
  //   Once the channel is obtained, the Socket API may
  //   be used exactly the same as usual, except all communications
  //   are sent through the channel in the SSH tunnel.
  //   Any number of channels may be created from the same SSH tunnel.
  //   Multiple channels may coexist at the same time.

  //  Connect to the GMAIL IMAP server via TLS (through the port-forwarded SSH tunnel)
  channel := TSocket.Create;
  maxWaitMs := 4000;
  useTls := True;
  success := tunnel.SshNewChannel('imap.gmail.com',993,useTls,maxWaitMs,channel);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  If desired, visually inspect the LastErrorText to see that indeed the TLS
  //  protocol was run inside the SSH tunnel:
  WriteLn(tunnel.LastErrorText);

  //  The first thing an IMAP server does is to send a greeting terminated with a CRLF.
  imapGreeting := channel.ReceiveToCRLF();
  if (channel.LastMethodSuccess <> True) then
    begin
      WriteLn(channel.LastErrorText);
      Exit;
    end;

  WriteLn(imapGreeting);

  //  Close the connection to imap.gmail.com.  This is actually closing our channel
  //  within the SSH tunnel, but keeps the tunnel open for the next port-forwarded connection.
  success := channel.Close(maxWaitMs);
  if (success = False) then
    begin
      WriteLn(channel.LastErrorText);
      Exit;
    end;

  //  Finally, close the SSH tunnel.
  success := tunnel.SshCloseTunnel();
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  WriteLn('TLS SSH tunneling example completed.');


  tunnel.Free;
  channel.Free;

end;

// ---------------------------------------------------------------------------

begin

  try
    RunDemo;
  except
    on E: Exception do
      WriteLn('Unhandled exception: ', E.ClassName, ': ', E.Message);
  end;

  WriteLn;
  {$IFDEF MSWINDOWS}
  WriteLn('Press Enter to exit...');
  ReadLn;
  {$ENDIF}
end.