Pascal (Lazarus/Delphi)

SSH Tunnel Through an Outbound SOCKS Proxy

Demonstrates reaching the SSH server through an outbound SOCKS proxy using the SocksVersion, SocksHostname, SocksPort, SocksUsername, and SocksPassword properties.

Background: This is the reverse direction from dynamic forwarding: here a SOCKS proxy is used to reach the SSH server, for networks where outbound connections must pass through one. SocksVersion is the switch — 0 means no SOCKS, while 4 or 5 selects the protocol. SOCKS5 supports username/password authentication and remote DNS; SOCKS4 supports only a username.

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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.SshTunnel;

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

procedure RunDemo;
var
  success: Boolean;
  tunnel: TSshTunnel;
  sshPort: Integer;
  password: string;
  listenPort: Integer;
  waitForThreadExit: Boolean;

begin
  success := False;

  //  Demonstrates reaching the SSH server through an outbound SOCKS proxy using the SshTunnel
  //  properties SocksVersion, SocksHostname, SocksPort, SocksUsername, and SocksPassword.

  tunnel := TSshTunnel.Create;

  //  Set SocksVersion to 4 or 5 to route the outbound connection to the SSH server through a SOCKS
  //  proxy.  A value of 0 (the default) means no SOCKS proxy.
  tunnel.SocksVersion := 5;
  tunnel.SocksHostname := 'socks.example.com';
  tunnel.SocksPort := 1080;

  //  SOCKS4 supports only a username; SOCKS5 supports username and password.
  tunnel.SocksUsername := 'myProxyLogin';
  tunnel.SocksPassword := 'myProxyPassword';

  tunnel.DestHostname := 'db.internal.example.com';
  tunnel.DestPort := 5432;

  //  Connect to the SSH server through the SOCKS proxy configured above.
  sshPort := 22;
  success := tunnel.Connect('ssh.example.com',sshPort);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  Normally you would not hard-code the password in source.  You should instead obtain it
  //  from an interactive prompt, environment variable, or a secrets vault.
  password := 'mySshPassword';

  success := tunnel.AuthenticatePw('mySshLogin',password);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  listenPort := 1080;
  success := tunnel.BeginAccepting(listenPort);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;
  WriteLn('Tunnel established through the SOCKS proxy.');

  waitForThreadExit := True;
  success := tunnel.CloseTunnel(waitForThreadExit);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;


  tunnel.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.