Pascal (Lazarus/Delphi)

SSH Tunnel Authenticate with Secure Strings

Demonstrates SSH tunnel password authentication using SecureString objects, with the credentials read from an encrypted JSON config file and decrypted directly into secure strings rather than being hard-coded in source.

Background: The SshTunnel class runs the tunnel on a background thread, so it authenticates once and then serves connections until closed — which makes protecting the stored credential especially worthwhile. Decrypting straight into a SecureString avoids ever holding the password in an ordinary string, and the value stays encrypted in memory under a randomly generated session key. In production the decryption key itself would come from a key vault or OS keystore rather than a literal.

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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,
  Chilkat.SecureString,
  Chilkat.JsonObject,
  Chilkat.Crypt2;

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

procedure RunDemo;
var
  success: Boolean;
  json: TJsonObject;
  crypt: TCrypt2;
  ssLogin: TSecureString;
  ssPassword: TSecureString;
  tunnel: TSshTunnel;
  port: Integer;
  waitForThreadExit: Boolean;

begin
  success := False;

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

  //  Demonstrates SSH tunnel password authentication using SecureString objects, with the
  //  credentials read from an encrypted config file rather than hard-coded in source.

  //  Imagine the login and password were previously encrypted and saved in a JSON config file:
  //  {
  //    "ssh_login": "2+qylFfC56Ck7OQQt/U2/w==",
  //    "ssh_password": "5neIq9Jmn0E3p71N6Yc8TA=="
  //  }
  json := TJsonObject.Create;
  success := json.LoadFile('qa_data/passwords/ssh.json');
  if (success = False) then
    begin
      WriteLn(json.LastErrorText);
      Exit;
    end;

  //  These are the encryption settings used when the credentials were encrypted.  In a real
  //  application the key would come from a secure source, not a literal.
  crypt := TCrypt2.Create;
  crypt.CryptAlgorithm := 'aes';
  crypt.CipherMode := 'cbc';
  crypt.KeyLength := 128;
  crypt.SetEncodedKey('000102030405060708090A0B0C0D0E0F','hex');
  crypt.SetEncodedIV('000102030405060708090A0B0C0D0E0F','hex');
  crypt.EncodingMode := 'base64';

  //  Decrypt directly into SecureString objects.  The values stay encrypted in memory, now under
  //  a randomly generated session key.
  ssLogin := TSecureString.Create;
  ssPassword := TSecureString.Create;
  crypt.DecryptSecureENC(json.StringOf('ssh_login'),ssLogin);
  crypt.DecryptSecureENC(json.StringOf('ssh_password'),ssPassword);

  tunnel := TSshTunnel.Create;

  port := 22;
  success := tunnel.Connect('ssh.example.com',port);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  //  Authenticate using the secure strings.
  success := tunnel.AuthenticateSecPw(ssLogin,ssPassword);
  if (success = False) then
    begin
      WriteLn(tunnel.LastErrorText);
      Exit;
    end;

  WriteLn('SSH tunnel authentication successful.');

  //  ... use the tunnel ...

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


  json.Free;
  crypt.Free;
  ssLogin.Free;
  ssPassword.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.