Dart FFI libssh with private key auth

gistfile1.txt

import 'dart:ffi';
import 'dart:io';
import 'package:ffi/ffi.dart';
import 'package:libssh_binding/libssh_binding.dart';
import 'dart:ffi' as ffi;
import 'package:path/path.dart' as path;

void main() async {
// Some vars (change to suit)
  String remoteFile = "/home/cconstab/testfile";
  String localFile = "./testfile";
  String sshKeyFile = "/home/cconstab/.ssh/GitHub_rsa";
  var host = "192.168.1.149";
  var port = 22;
  var username = "cconstab";

  // Open the dynamic library
  var libraryPath = path.join('/lib/x86_64-linux-gnu/', 'libssh.so.4');
  final dll = ffi.DynamicLibrary.open(libraryPath);
  var libssh = LibsshBinding(dll);


  // Set up session
  var mySshSession = libssh.ssh_new();
  libssh.ssh_options_set(mySshSession, ssh_options_e.SSH_OPTIONS_HOST, stringToNativeVoid(host));
  libssh.ssh_options_set(mySshSession, ssh_options_e.SSH_OPTIONS_PORT, intToNativeVoid(port));
  libssh.ssh_options_set(mySshSession, ssh_options_e.SSH_OPTIONS_USER, stringToNativeVoid(username));
  
  // Connect to server 
  var rc = libssh.ssh_connect(mySshSession);
  if (rc != SSH_OK) {
    print('Error connecting to host: $host\n');
  }

  ffi.Pointer<ffi.Pointer<ssh_key_struct>> sshKey = calloc();

  rc = libssh.ssh_pki_import_privkey_file(
      stringToNativeInt8(sshKeyFile), nullptr, nullptr, nullptr, sshKey);

  rc = libssh.ssh_userauth_publickey(mySshSession, stringToNativeInt8(username), sshKey[0]);
  if (rc != ssh_auth_e.SSH_AUTH_SUCCESS) {
    var error = libssh.ssh_get_error(mySshSession.cast());
    print("Error authenticating with Keys:$error\n");
    libssh.ssh_disconnect(mySshSession);
    libssh.ssh_free(mySshSession);
    exit(-1);
  }

  await libssh.sftpDownloadFileTo(
      mySshSession, stringToNativeInt8(remoteFile), path.join(Directory.current.path, localFile));

  libssh.ssh_disconnect(mySshSession);
  libssh.ssh_free(mySshSession);

  exit(0);
}