Dart

Connect to an SFTP Server Through a Jump Host

Demonstrates the Chilkat SFtp.ConnectThroughSsh method, which connects to an SFTP 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 hostname and port.

Background: This is the "jump host" (bastion) pattern: the application connects to a reachable gateway, then tunnels onward to an SFTP server that is only accessible from inside the network. Each hop authenticates separately with its own credentials. The result is a normal SFtp object — still requiring its own authentication and InitializeSftp — that happens to be routed through the first connection.

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Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // Demonstrates the SFtp.ConnectThroughSsh method, which connects to an SFTP 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 hostname and port.

  final sshJump = CkSsh();

  // Connect and authenticate to the jump host first.
  final port = 22;
  try {
    sshJump.connect('jump.example.com', port);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // 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.
  final password = 'mySshPassword';

  try {
    sshJump.authenticatePw('myJumpLogin', password);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Connect to the SFTP server through the jump host.
  final sftp = CkSFtp();
  try {
    sftp.connectThroughSsh(sshJump, 'sftp.internal.example.com', port);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Authenticate to the SFTP server (its own credentials), then initialize SFTP.
  try {
    sftp.authenticatePw('mySshLogin', password);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  try {
    sftp.initializeSftp();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  print('Connected to the SFTP server through the jump host.');

  sftp.disconnect();
  sshJump.disconnect();
}