Pascal (Lazarus/Delphi)

Connect an SSH Tunnel Through a Jump Host

Demonstrates the Chilkat SshTunnel.ConnectThroughSsh method, which connects to an SSH server through an already connected and authenticated Ssh object. The first argument is the jump-host Ssh object, and the second and third are the destination SSH hostname and port.

Background: This chains the tunnel through a "jump host" (bastion): the application reaches a gateway server, then tunnels onward to an SSH server that is only accessible from inside the network. Each hop authenticates separately with its own credentials. The result is a normal SshTunnel — still requiring its own authentication and BeginAccepting — whose transport is routed through the first connection.

Chilkat Pascal (Lazarus/Delphi) Downloads

Download Chilkat for Pascal (Lazarus/Delphi)

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,
  Chilkat.Ssh;

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

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

begin
  success := False;

  //  Demonstrates the SshTunnel.ConnectThroughSsh method, which connects to an SSH server through
  //  an already connected and authenticated Ssh object (a jump host).  The 1st argument is the Ssh
  //  object, and the 2nd and 3rd are the destination SSH hostname and port.

  sshJump := TSsh.Create;

  //  Connect and authenticate to the jump host first.
  sshPort := 22;
  success := sshJump.Connect('jump.example.com',sshPort);
  if (success = False) then
    begin
      WriteLn(sshJump.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 := sshJump.AuthenticatePw('myJumpLogin',password);
  if (success = False) then
    begin
      WriteLn(sshJump.LastErrorText);
      Exit;
    end;

  //  Set up the tunnel and connect to the target SSH server through the jump host.
  tunnel := TSshTunnel.Create;
  tunnel.DestHostname := 'db.internal.example.com';
  tunnel.DestPort := 5432;

  success := tunnel.ConnectThroughSsh(sshJump,'ssh.internal.example.com',sshPort);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  Authenticate to the target SSH server (its own credentials).
  success := tunnel.AuthenticatePw('mySshLogin',password);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  After authenticating, call BeginAccepting to start listening for local connections to forward.

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

  sshJump.Disconnect();


  sshJump.Free;
  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.