DartSSH 4

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

dartssh4 is a fork of dartssh4 with a fresh start.

✨ 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 dartssh4

ServerBox Ssh! No Ports

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

🧪 Try

# Install the `dartssh` command.
dart pub global activate dartssh4_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

https://github.com/GreenAppers/dartssh by GreenAppers

License

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

Libraries

dartssh4