net.schmizz.sshj

Class SSHClient

java.lang.Object

net.schmizz.sshj.SocketClient

net.schmizz.sshj.SSHClient

All Implemented Interfaces:

Closeable, AutoCloseable, SessionFactory

public class SSHClient
extends SocketClient
implements Closeable, SessionFactory

Secure SHell client API.

Before connection is established, host key verification needs to be accounted for. This is done by specifying one or more HostKeyVerifier objects. Database of known hostname-key pairs in the OpenSSH "known_hosts" format can be loaded for host key verification.

User authentication can be performed by any of the auth*() method.

startSession() caters to the most typical use case of starting a session channel and executing a remote command, starting a subsystem, etc. If you wish to request X11 forwarding for some session, first register a ConnectListener for x11 channels.

Local and remote port forwarding is possible. There are also utility method for easily creating SCP and SFTP implementations.

A simple example:

 final SSHClient client = new SSHClient();
 client.loadKnownHosts();
 client.connect("hostname");
 try {
     client.authPassword("username", "password");
     final Session session = client.startSession();
     try {
          final Command cmd = session.exec("true");
          cmd.join(1, TimeUnit.SECONDS);
     } finally {
          session.close();
     }
 } finally {
      client.disconnect();
 }
 

Where a password or passphrase is required, if you're extra-paranoid use the char[] based method. The char[] will be blanked out after use.

Field Summary

Fields

Modifier and Type	Field and Description
protected UserAuth	auth ssh-userauth service
protected Connection	conn ssh-connection service
static int	DEFAULT_PORT Default port for SSH
protected org.slf4j.Logger	log Logger
protected Transport	trans Transport layer

Constructor Summary

Constructors

Constructor and Description
SSHClient() Default constructor.
SSHClient(Config config) Constructor that allows specifying a config to be used.

Method Summary

Methods

Modifier and Type	Method and Description
void	addHostKeyVerifier(HostKeyVerifier hostKeyVerifier) Add a HostKeyVerifier which will be invoked for verifying host key during connection establishment and future key exchanges.
void	addHostKeyVerifier(String fingerprint) Add a HostKeyVerifier that will verify any host that's able to claim a host key with the given fingerprint, e.g.
void	auth(String username, AuthMethod... methods) Authenticate username using the supplied methods.
void	auth(String username, Iterable<AuthMethod> methods) Authenticate username using the supplied methods.
void	authPassword(String username, char[] password) Authenticate username using the "password" authentication method and as a fallback basic challenge-response authentication..
void	authPassword(String username, PasswordFinder pfinder) Authenticate username using the "password" authentication method and as a fallback basic challenge-response authentication.
void	authPassword(String username, String password) Authenticate username using the "password" authentication method and as a fallback basic challenge-response authentication.
void	authPublickey(String username) Authenticate username using the "publickey" authentication method, with keys from some common locations on the file system.
void	authPublickey(String username, Iterable<KeyProvider> keyProviders) Authenticate username using the "publickey" authentication method.
void	authPublickey(String username, KeyProvider... keyProviders) Authenticate username using the "publickey" authentication method.
void	authPublickey(String username, String... locations) Authenticate username using the "publickey" authentication method, with keys from one or more locations in the file system.
void	close() Same as disconnect().
void	disconnect() Disconnects from the connected SSH server.
protected void	doKex() Do key exchange.
Connection	getConnection()
RemotePortForwarder	getRemotePortForwarder()
Transport	getTransport()
UserAuth	getUserAuth()
boolean	isAuthenticated()
boolean	isConnected()
KeyProvider	loadKeys(KeyPair kp) Creates a KeyProvider from supplied KeyPair.
KeyProvider	loadKeys(String location) Returns a KeyProvider instance created from a location on the file system where an unencrypted private key file (does not require a passphrase) can be found.
KeyProvider	loadKeys(String location, char[] passphrase) Utility function for createing a KeyProvider instance from given location on the file system.
KeyProvider	loadKeys(String location, PasswordFinder passwordFinder) Creates a KeyProvider instance from given location on the file system.
KeyProvider	loadKeys(String location, String passphrase) Convenience method for creating a KeyProvider instance from a location where an encrypted key file is located.
KeyProvider	loadKeys(String privateKey, String publicKey, PasswordFinder passwordFinder) Creates a KeyProvider instance from passed strings.
void	loadKnownHosts() Attempts loading the user's known_hosts file from the default locations, i.e.
void	loadKnownHosts(File location) Adds a OpenSSHKnownHosts object created from the specified location as a host key verifier.
LocalPortForwarder	newLocalPortForwarder(LocalPortForwarder.Parameters parameters, ServerSocket serverSocket) Create a LocalPortForwarder that will listen based on parameters using the bound serverSocket and forward incoming connections to the server; which will further forward them to host:port.
SCPFileTransfer	newSCPFileTransfer()
SFTPClient	newSFTPClient()
protected void	onConnect() On connection establishment, also initializes the SSH transport via Transport.init(java.lang.String, int, java.io.InputStream, java.io.OutputStream) and doKex().
X11Forwarder	registerX11Forwarder(ConnectListener listener) Register a listener for handling forwarded X11 channels.
void	rekey() Does key re-exchange.
Session	startSession() Opens a session channel.
void	useCompression() Adds zlib compression to preferred compression algorithms.

Methods inherited from class net.schmizz.sshj.SocketClient

connect, connect, connect, connect, connect, connect, getConnectTimeout, getLocalAddress, getLocalPort, getRemoteAddress, getRemoteHostname, getRemotePort, getSocket, getSocketFactory, getTimeout, setConnectTimeout, setSocketFactory, setTimeout

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

DEFAULT_PORT

public static final int DEFAULT_PORT

Default port for SSH

See Also:

Constant Field Values

log

protected final org.slf4j.Logger log

Logger

trans

protected final Transport trans

Transport layer

auth

protected final UserAuth auth

ssh-userauth service

conn

protected final Connection conn

ssh-connection service

Constructor Detail

SSHClient

public SSHClient()

Default constructor. Initializes this object using DefaultConfig.

SSHClient

public SSHClient(Config config)

Constructor that allows specifying a config to be used.

Parameters:

config - Config instance

Method Detail

addHostKeyVerifier

public void addHostKeyVerifier(HostKeyVerifier hostKeyVerifier)

Add a HostKeyVerifier which will be invoked for verifying host key during connection establishment and future key exchanges.

Parameters:

hostKeyVerifier - HostKeyVerifier instance

addHostKeyVerifier

public void addHostKeyVerifier(String fingerprint)

Add a HostKeyVerifier that will verify any host that's able to claim a host key with the given fingerprint, e.g. "4b:69:6c:72:6f:79:20:77:61:73:20:68:65:72:65:21"

Parameters:

fingerprint - expected fingerprint in colon-delimited format (16 octets in hex delimited by a colon)

See Also:

SecurityUtils.getFingerprint(java.security.PublicKey)

auth

public void auth(String username,
        AuthMethod... methods)
          throws UserAuthException,
                 TransportException

Authenticate username using the supplied methods.

Parameters:

username - user to authenticate

methods - one or more authentication method

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

auth

public void auth(String username,
        Iterable<AuthMethod> methods)
          throws UserAuthException,
                 TransportException

Authenticate username using the supplied methods.

Parameters:

username - user to authenticate

methods - one or more authentication method

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPassword

public void authPassword(String username,
                String password)
                  throws UserAuthException,
                         TransportException

Authenticate username using the "password" authentication method and as a fallback basic challenge-response authentication.

Parameters:

username - user to authenticate

password - the password to use for authentication

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPassword

public void authPassword(String username,
                char[] password)
                  throws UserAuthException,
                         TransportException

Authenticate username using the "password" authentication method and as a fallback basic challenge-response authentication.. The password array is blanked out after use.

Parameters:

username - user to authenticate

password - the password to use for authentication

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPassword

public void authPassword(String username,
                PasswordFinder pfinder)
                  throws UserAuthException,
                         TransportException

Authenticate username using the "password" authentication method and as a fallback basic challenge-response authentication.

Parameters:

username - user to authenticate

pfinder - the PasswordFinder to use for authentication

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPublickey

public void authPublickey(String username)
                   throws UserAuthException,
                          TransportException

Authenticate username using the "publickey" authentication method, with keys from some common locations on the file system. This method relies on ~/.ssh/id_rsa and ~/.ssh/id_dsa.

This method does not provide a way to specify a passphrase.

Parameters:

username - user to authenticate

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPublickey

public void authPublickey(String username,
                 Iterable<KeyProvider> keyProviders)
                   throws UserAuthException,
                          TransportException

Authenticate username using the "publickey" authentication method.

KeyProvider instances can be created using any of the of the loadKeys() method provided in this class. In case multiple keyProviders are specified; authentication is attempted in order as long as the "publickey" authentication method is available.

Parameters:

username - user to authenticate

keyProviders - one or more KeyProvider instances

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPublickey

public void authPublickey(String username,
                 KeyProvider... keyProviders)
                   throws UserAuthException,
                          TransportException

Authenticate username using the "publickey" authentication method.

KeyProvider instances can be created using any of the loadKeys() method provided in this class. In case multiple keyProviders are specified; authentication is attempted in order as long as the "publickey" authentication method is available.

Parameters:

username - user to authenticate

keyProviders - one or more KeyProvider instances

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

authPublickey

public void authPublickey(String username,
                 String... locations)
                   throws UserAuthException,
                          TransportException

Authenticate username using the "publickey" authentication method, with keys from one or more locations in the file system.

In case multiple locations are specified; authentication is attempted in order as long as the "publickey" authentication method is available. If there is an error loading keys from any of them (e.g. file could not be read, file format not recognized) that key file it is ignored.

This method does not provide a way to specify a passphrase.

Parameters:

username - user to authenticate

locations - one or more locations in the file system containing the private key

Throws:

UserAuthException - in case of authentication failure

TransportException - if there was a transport-layer error

disconnect

public void disconnect()
                throws IOException

Disconnects from the connected SSH server. SSHClient objects are not reusable therefore it is incorrect to attempt connection after this method has been called.

This method should be called from a finally construct after connection is established; so that proper cleanup is done and the thread spawned by the transport layer for dealing with incoming packets is stopped.

Overrides:

disconnect in class SocketClient

Throws:

IOException

getConnection

public Connection getConnection()

Returns:

the associated Connection instance.

getRemotePortForwarder

public RemotePortForwarder getRemotePortForwarder()

Returns:

a RemotePortForwarder that allows requesting remote forwarding over this connection.

getTransport

public Transport getTransport()

Returns:

the associated Transport instance.

getUserAuth

public UserAuth getUserAuth()

Returns:

the associated UserAuth instance. This allows access to information like the authentication banner, whether authentication was at least partially successful, and any saved exceptions that were ignored because there were more authentication method that could be tried.

isAuthenticated

public boolean isAuthenticated()

Returns:

whether authenticated.

isConnected

public boolean isConnected()

Overrides:

isConnected in class SocketClient

Returns:

whether connected.

loadKeys

public KeyProvider loadKeys(KeyPair kp)

Creates a KeyProvider from supplied KeyPair.

Parameters:

kp - the key pair

Returns:

the key provider ready for use in authentication

loadKeys

public KeyProvider loadKeys(String location)
                     throws IOException

Returns a KeyProvider instance created from a location on the file system where an unencrypted private key file (does not require a passphrase) can be found. Simply calls loadKeys(String, PasswordFinder) with the PasswordFinder argument as null.

Parameters:

location - the location for the key file

Returns:

the key provider ready for use in authentication

Throws:

SSHException - if there was no suitable key provider available for the file format; typically because BouncyCastle is not in the classpath

IOException - if the key file format is not known, if the file could not be read, etc.

loadKeys

public KeyProvider loadKeys(String location,
                   char[] passphrase)
                     throws IOException

Utility function for createing a KeyProvider instance from given location on the file system. Creates a one-off PasswordFinder using PasswordUtils.createOneOff(char[]), and calls loadKeys(String, PasswordFinder).

Parameters:

location - location of the key file

passphrase - passphrase as a char-array

Returns:

the key provider ready for use in authentication

Throws:

SSHException - if there was no suitable key provider available for the file format; typically because BouncyCastle is not in the classpath

IOException - if the key file format is not known, if the file could not be read, etc.

loadKeys

public KeyProvider loadKeys(String location,
                   PasswordFinder passwordFinder)
                     throws IOException

Creates a KeyProvider instance from given location on the file system. Currently only PKCS8 format private key files are supported (OpenSSH uses this format).

Parameters:

location - the location of the key file

passwordFinder - the PasswordFinder that can supply the passphrase for decryption (may be null in case keyfile is not encrypted)

Returns:

the key provider ready for use in authentication

Throws:

SSHException - if there was no suitable key provider available for the file format; typically because BouncyCastle is not in the classpath

IOException - if the key file format is not known, if the file could not be read, etc.

loadKeys

public KeyProvider loadKeys(String location,
                   String passphrase)
                     throws IOException

Convenience method for creating a KeyProvider instance from a location where an encrypted key file is located. Calls loadKeys(String, char[]) with a character array created from the supplied passphrase string.

Parameters:

location - location of the key file

passphrase - passphrase as a string

Returns:

the key provider for use in authentication

Throws:

IOException - if the key file format is not known, if the file could not be read etc.

loadKeys

public KeyProvider loadKeys(String privateKey,
                   String publicKey,
                   PasswordFinder passwordFinder)
                     throws IOException

Creates a KeyProvider instance from passed strings. Currently only PKCS8 format private key files are supported (OpenSSH uses this format).

Parameters:

privateKey - the private key as a string

publicKey - the public key as a string if it's not included with the private key

passwordFinder - the PasswordFinder that can supply the passphrase for decryption (may be null in case keyfile is not encrypted)

Returns:

the key provider ready for use in authentication

Throws:

SSHException - if there was no suitable key provider available for the file format; typically because BouncyCastle is not in the classpath

IOException - if the key file format is not known, etc.

loadKnownHosts

public void loadKnownHosts()
                    throws IOException

Attempts loading the user's known_hosts file from the default locations, i.e. ~/.ssh/known_hosts and ~/.ssh/known_hosts2 on most platforms. Adds the resulting OpenSSHKnownHosts object as a host key verifier.

For finer control over which file is used, see loadKnownHosts(File).

Throws:

IOException - if there is an error loading from both locations

loadKnownHosts

public void loadKnownHosts(File location)
                    throws IOException

Adds a OpenSSHKnownHosts object created from the specified location as a host key verifier.

Parameters:

location - location for known_hosts file

Throws:

IOException - if there is an error loading from any of these locations

newLocalPortForwarder

public LocalPortForwarder newLocalPortForwarder(LocalPortForwarder.Parameters parameters,
                                       ServerSocket serverSocket)

Create a LocalPortForwarder that will listen based on parameters using the bound serverSocket and forward incoming connections to the server; which will further forward them to host:port.

The returned forwarder's listen() method should be called to actually start listening, this method just creates an instance.

Parameters:

parameters - parameters for the forwarding setup

serverSocket - bound server socket

Returns:

a LocalPortForwarder

registerX11Forwarder

public X11Forwarder registerX11Forwarder(ConnectListener listener)

Register a listener for handling forwarded X11 channels. Without having done this, an incoming X11 forwarding will be summarily rejected.

It should be clarified that multiple listeners for X11 forwarding over a single SSH connection are not supported (and don't make much sense). So a subsequent call to this method is only going to replace the registered listener.

Parameters:

listener - the ConnectListener that should be delegated the responsibility of handling forwarded X11Forwarder.X11Channel 's

Returns:

an X11Forwarder that allows to stop acting on X11 requests from server

newSCPFileTransfer

public SCPFileTransfer newSCPFileTransfer()

Returns:

Instantiated SCPFileTransfer implementation.

newSFTPClient

public SFTPClient newSFTPClient()
                         throws IOException

Returns:

Instantiated SFTPClient implementation.

Throws:

IOException - if there is an error starting the sftp subsystem

See Also:

StatefulSFTPClient

rekey

public void rekey()
           throws TransportException

Does key re-exchange.

Throws:

TransportException - if an error occurs during key exchange

startSession

public Session startSession()
                     throws ConnectionException,
                            TransportException

Description copied from interface: SessionFactory

Opens a session channel. The returned Session instance allows executing a remote command, starting a subsystem, or starting a shell.

Specified by:

startSession in interface SessionFactory

Returns:

the opened session channel

Throws:

ConnectionException

TransportException

See Also:

Session

useCompression

public void useCompression()
                    throws TransportException

Adds zlib compression to preferred compression algorithms. There is no guarantee that it will be successfully negotiatied.

If the client is already connected renegotiation is done; otherwise this method simply returns (and compression will be negotiated during connection establishment).

Throws:

ClassNotFoundException - if JZlib is not in classpath

TransportException - if an error occurs during renegotiation

onConnect

protected void onConnect()
                  throws IOException

On connection establishment, also initializes the SSH transport via Transport.init(java.lang.String, int, java.io.InputStream, java.io.OutputStream) and doKex().

Throws:

IOException

doKex

protected void doKex()
              throws TransportException

Do key exchange.

Throws:

TransportException - if error during kex

close

public void close()
           throws IOException

Same as disconnect().

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Throws:

IOException