DartSSH 2

SSH and SFTP client written in pure Dart, aiming to be feature-rich as well as easy to use.

dartssh2 is now a complete rewrite of dartssh.

✨ Features

  • Pure Dart: Working with both Dart VM and Flutter.
  • SSH Session: Executing commands, spawning shells, setting environment variables, pseudo terminals, etc.
  • Authentication: Supports password, private key and interactive authentication method.
  • Forwarding: Supports local forwarding and remote forwarding.
  • SFTP: Supports all operations defined in SFTPv3 protocol including upload, download, list, link, remove, rename, etc.

🧬 Built with dartssh2

ServerBox Ssh! No Ports DartShell
ServerBox interface displaying connection management options ServerBox user interface for server control and monitoring Ssh! No Ports demo showcasing SSH connectivity without open ports dartShell displaying terminal and session information for SSH operations

Feel free to add your own app here by opening a pull request.

🧪 Try

# Install the `dartssh` command.
dart pub global activate dartssh2_cli

# Then use `dartssh` as regular `ssh` command.
dartssh user@example.com

# Example: execute a command on remote host.
dartssh user@example.com ls -al

# Example: connect to a non-standard port.
dartssh user@example.com:<port>

# Transfer files via SFTP.
dartsftp user@example.com

If the dartssh command can't be found after installation, you might need to set up your path.

🚀 Quick start

Connect to a remote host

final client = SSHClient(
  await SSHSocket.connect('localhost', 22),
  username: '<username>',
  onPasswordRequest: () => '<password>',
);

SSHSocket is an interface and it's possible to implement your own SSHSocket if you want to use a different underlying transport rather than standard TCP socket. For example WebSocket or Unix domain socket.

Spawn a shell on remote host

final shell = await client.shell();
stdout.addStream(shell.stdout); // listening for stdout
stderr.addStream(shell.stderr); // listening for stderr
stdin.cast<Uint8List>().listen(shell.write); // writing to stdin

await shell.done; // wait for shell to exit
client.close();

Execute a command on remote host

final uptime = await client.run('uptime');
print(utf8.decode(uptime));

Ignoring stderr:

final uptime = await client.run('uptime', stderr: false);
print(utf8.decode(uptime));

client.run() is a convenience method that wraps client.execute() for running non-interactive commands.

Start a process on remote host

final session = await client.execute('cat > file.txt');
await session.stdin.addStream(File('local_file.txt').openRead().cast());
await session.stdin.close(); // Close the sink to send EOF to the remote process.

await session.done; // Wait for session to exit to ensure all data is flushed to the remote process.
print(session.exitCode); // You can get the exit code after the session is done

session.write() is a shorthand for session.stdin.add(). It's recommended to use session.stdin.addStream() instead of session.write() when you want to stream large amount of data to the remote process.

Killing a remote process by sending signal

session.kill(SSHSignal.KILL);
await session.done;
print('exitCode: ${session.exitCode}'); // -> exitCode: null
print('signal: ${session.exitSignal?.signalName}'); // -> signal: KILL

Processes killed by signals do not have an exit code, instead they have an exit signal property.

Forward connections on local port 8080 to the server

final serverSocket = await ServerSocket.bind('localhost', 8080);
await for (final socket in serverSocket) {
  final forward = await client.forwardLocal('httpbin.org', 80);
  forward.stream.cast<List<int>>().pipe(socket);
  socket.pipe(forward.sink);
}

Forward connections to port 2222 on the server to local port 22

final forward = await client.forwardRemote(port: 2222);

if (forward == null) {
  print('Failed to forward remote port');
  return;
}

await for (final connection in forward.connections) {
  final socket = await Socket.connect('localhost', 22);
  connection.stream.cast<List<int>>().pipe(socket);
  socket.pipe(connection.sink);
}

Authenticate with public keys

final client = SSHClient(
  socket,
  username: '<username>',
  identities: [
    // A single private key file may contain multiple keys.
    ...SSHKeyPair.fromPem(await File('path/to/id_rsa').readAsString())
  ],
);

Use encrypted PEM files

// Test whether the private key is encrypted.
final encrypted = SSHKeyPair.isEncrypted(await File('path/to/id_rsa').readAsString());
print(encrypted);

// If the private key is encrypted, you need to provide the passphrase.
final keys = SSHKeyPair.fromPem('<pem text>', '<passphrase>');
print(keys);

Decrypt PEM file with compute in Flutter

List<SSHKeyPair> decryptKeyPairs(List<String> args) {
  return SSHKeyPair.fromPem(args[0], args[1]);
}

final keypairs = await compute(decryptKeyPairs, ['<pem text>', '<passphrase>']);

Get the version of SSH server

await client.authenticated;
print(client.remoteVersion); // SSH-2.0-OpenSSH_7.4p1

Connect through a jump server

final jumpServer = SSHClient(
  await SSHSocket.connect('<jump server>', 22),
  username: '...',
  onPasswordRequest: () => '...',
);

final client = SSHClient(
  await jumpServer.forwardLocal('<target server>', 22),
  username: '...',
  onPasswordRequest: () => '...',
);

print(utf8.decode(await client.run('hostname'))); // -> hostname of  <target server>

}

SFTP

List remote directory

final sftp = await client.sftp();
final items = await sftp.listdir('/');
for (final item in items) {
  print(item.longname);
}

Read remote file

final sftp = await client.sftp();
final file = await sftp.open('/etc/passwd');
final content = await file.readBytes();
print(latin1.decode(content));

Write remote file

final sftp = await client.sftp();
final file = await sftp.open('file.txt', mode: SftpFileOpenMode.write);
await file.writeBytes(utf8.encode('hello there!') as Uint8List);

Write at specific offset

final data = utf8.encode('world') as Uint8List
await file.writeBytes(data, offset: 6);

File upload

final sftp = await client.sftp();
final file = await sftp.open('file.txt', mode: SftpFileOpenMode.create | SftpFileOpenMode.write);
await file.write(File('local_file.txt').openRead().cast());

Pause and resume file upload

final uploader = await file.write(File('local_file.txt').openRead().cast());
// ...
await uploader.pause();
// ...
await uploader.resume();
await uploader.done;

Clear the remote file before opening it

final file = await sftp.open('file.txt',
  mode: SftpFileOpenMode.create | SftpFileOpenMode.truncate | SftpFileOpenMode.write
);

Directory operations

final sftp = await client.sftp();
await sftp.mkdir('/path/to/dir');
await sftp.rmdir('/path/to/dir');

Get/Set attributes from/to remote file/directory

await sftp.stat('/path/to/file');
await sftp.setStat(
  '/path/to/file',
  SftpFileAttrs(mode: SftpFileMode(userRead: true)),
);

Get the type of a remote file

final stat = await sftp.stat('/path/to/file');
print(stat.type);
// or
print(stat.isDirectory);
print(stat.isSocket);
print(stat.isSymbolicLink);
// ...

final sftp = await client.sftp();
sftp.link('/from', '/to');

Get (estimated) total and free space on the remote filesystem

final sftp = await client.sftp();
final statvfs = await sftp.statvfs('/root');
print('total: ${statvfs.blockSize * statvfs.totalBlocks}');
print('free: ${statvfs.blockSize * statvfs.freeBlocks}');

🪜 Example

SSH client:

SFTP:

🔐 Supported algorithms

Host key:

  • ssh-rsa
  • rsa-sha2-[256|512]
  • ecdsa-sha2-nistp[256|384|521]
  • ssh-ed25519

Key exchange:

  • curve25519-sha256
  • ecdh-sha2-nistp[256|384|521]
  • diffie-hellman-group-exchange-sha[1|256]
  • diffie-hellman-group14-sha[1|256]
  • diffie-hellman-group1-sha1

Cipher:

  • aes[128|192|256]-ctr
  • aes[128|192|256]-cbc

Integrity:

  • hmac-md5
  • hmac-sha1
  • hmac-sha2-[256|512]

Private key:

Type Decode Decrypt Encode Encrypt
RSA ✔️ ✔️ ✔️ WIP
OpenSSH RSA ✔️ ✔️ ✔️ WIP
OpenSSH ECDSA ✔️ ✔️ ✔️ WIP
OpenSSH Ed25519 ✔️ ✔️ ✔️ WIP

⏳ Roadmap

  • x Fix broken tests.
  • x Sound null safety.
  • x Redesign API to allow starting multiple sessions.
  • x Full SFTP.
  • Server.

References

  • RFC 4250 The Secure Shell (SSH) Protocol Assigned Numbers.
  • RFC 4251 The Secure Shell (SSH) Protocol Architecture.
  • RFC 4252 The Secure Shell (SSH) Authentication Protocol.
  • RFC 4253 The Secure Shell (SSH) Transport Layer Protocol.
  • RFC 4254 The Secure Shell (SSH) Connection Protocol.
  • RFC 4255 Using DNS to Securely Publish Secure Shell (SSH) Key Fingerprints.
  • RFC 4256 Generic Message Exchange Authentication for the Secure Shell Protocol (SSH).
  • RFC 4419 Diffie-Hellman Group Exchange for the Secure Shell (SSH) Transport Layer Protocol.
  • RFC 4716 The Secure Shell (SSH) Public Key File Format.
  • RFC 5656 Elliptic Curve Algorithm Integration in the Secure Shell Transport Layer.
  • RFC 8332 Use of RSA Keys with SHA-256 and SHA-512 in the Secure Shell (SSH) Protocol.
  • RFC 8731 Secure Shell (SSH) Key Exchange Method Using Curve25519 and Curve448.
  • draft-miller-ssh-agent-03 SSH Agent Protocol.
  • draft-ietf-secsh-filexfer-02 SSH File Transfer Protocol.
  • draft-dbider-sha2-mac-for-ssh-06 SHA-2 Data Integrity Verification for the Secure Shell (SSH) Transport Layer Protocol.

Credits

License

dartssh is released under the terms of the MIT license. See LICENSE.

Libraries

dartssh2