Class SshClient

java.lang.Object
com.sshtools.j2ssh.SshClient

public class SshClient extends Object

Implements an SSH client with methods to connect to a remote server and perform all necersary SSH functions such as SCP, SFTP, executing commands, starting the users shell and perform port forwarding.

There are several steps to perform prior to performing the desired task. This involves the making the initial connection, authenticating the user and creating a session to execute a command, shell or subsystem and/or configuring the port forwarding manager.

To create a connection use the following code:

 // Create a instance and connect SshClient
 ssh = new SshClient();
 ssh.connect("hostname");
 
Once this code has executed and returned the connection is ready for authentication:
 PasswordAuthenticationClient pwd = new PasswordAuthenticationClient();
 pwd.setUsername("foo");
 pwd.setPassword("xxxxx");
 // Authenticate the user
 int result = ssh.authenticate(pwd);
 if(result==AuthenticationProtocolState.COMPLETED) {
    // Authentication complete
 }
 
Once authenticated the user's shell can be started:
 // Open a session channel
 SessionChannelClient session =
                      ssh.openSessionChannel();

 // Request a pseudo terminal, if you do not you may not see the prompt
 if(session.requestPseudoTerminal("ansi", 80, 24, 0, 0, "") {
      // Start the users shell
      if(session.startShell()) {
         // Do something with the session output
         session.getOutputStream().write("echo message\n");
         ....
       }
 }
 

Since:
0.2.0
Version:
$Revision: 1.75 $
Author:
Lee David Painter
  • Field Details

    • authentication

      protected AuthenticationProtocolClient authentication
      The SSH Authentication protocol implementation for this SSH client. The SSH Authentication protocol runs over the SSH Transport protocol as a transport protocol service.
    • connection

      protected ConnectionProtocol connection
      The SSH Connection protocol implementation for this SSH client. The connection protocol runs over the SSH Transport protocol as a transport protocol service and is started by the authentication protocol after a successful authentication.
    • forwarding

      protected ForwardingClient forwarding
      Provides a high level management interface for SSH port forwarding.
    • transport

      protected TransportProtocolClient transport
      The SSH Transport protocol implementation for this SSH Client.
    • authenticationState

      protected int authenticationState
      The current state of the authentication for the current connection.
    • socketTimeout

      protected int socketTimeout
      The timeout in milliseconds for the underlying transport provider (typically a Socket).
    • eventHandler

      protected SshEventAdapter eventHandler
      A Transport protocol event handler instance that receives notifications of transport layer events such as Socket timeouts and disconnection.
    • activeChannels

      protected Vector activeChannels
      The currently active channels for this SSH Client connection.
    • activeChannelListener

      protected com.sshtools.j2ssh.SshClient.ActiveChannelEventListener activeChannelListener
      An channel event listener implemention to maintain the active channel list.
    • useDefaultForwarding

      protected boolean useDefaultForwarding
      Flag indicating whether the forwarding instance is created when the connection is made.
  • Constructor Details

    • SshClient

      public SshClient()

      Contructs an unitilialized SshClient ready for connecting.

  • Method Details

    • getAuthenticationBanner

      public String getAuthenticationBanner(int timeout) throws IOException

      Returns the server's authentication banner.

      In some jurisdictions, sending a warning message before authentication may be relevant for getting legal protection. Many UNIX machines, for example, normally display text from `/etc/issue', or use "tcp wrappers" or similar software to display a banner before issuing a login prompt.

      The server may or may not send this message. Call this method to retrieve the message, specifying a timeout limit to wait for the message.

      Parameters:
      timeout - The number of milliseconds to wait for the banner message before returning
      Returns:
      The server's banner message
      Throws:
      IOException - If an IO error occurs reading the message
      Since:
      0.2.0
    • getAvailableAuthMethods

      public List getAvailableAuthMethods(String username) throws IOException

      Returns the list of available authentication methods for a given user.

      A client may request a list of authentication methods that may continue by using the "none" authentication method.This method calls the "none" method and returns the available authentication methods.

      Parameters:
      username - The name of the account for which you require the available authentication methods
      Returns:
      A list of Strings, for example "password", "publickey" & "keyboard-interactive"
      Throws:
      IOException - If an IO error occurs during the operation
      Since:
      0.2.0
    • isConnected

      public boolean isConnected()

      Returns the connection state of the client.

      Returns:
      true if the client is connected, false otherwise
      Since:
      0.2.0
    • isAuthenticated

      public boolean isAuthenticated()

      Evaluate whether the client has successfully authenticated.

      Returns:
      true if the client is authenticated, otherwise false
    • getServerId

      public String getServerId()

      Returns the identification string sent by the server during protocol negotiation. For example "SSH-2.0-OpenSSH_p3.4".

      Returns:
      The server's identification string.
      Since:
      0.2.0
    • getServerHostKey

      public SshPublicKey getServerHostKey()

      Returns the server's public key supplied during key exchange.

      Returns:
      the server's public key
      Since:
      0.2.0
    • getConnectionState

      public TransportProtocolState getConnectionState()

      Returns the transport protocol's connection state.

      Returns:
      The transport protocol's state
      Since:
      0.2.0
    • getForwardingClient

      public ForwardingClient getForwardingClient()

      Returns the default port forwarding manager.

      Returns:
      This connection's forwarding client
      Since:
      0.2.0
    • getRemoteEOL

      public int getRemoteEOL()

      Return's a rough guess at the server's EOL setting. This is simply derived from the identification string and should not be used as a cast iron proof on the EOL setting.

      Returns:
      The transport protocol's EOL constant
      Since:
      0.2.0
    • addEventHandler

      public void addEventHandler(SshEventAdapter eventHandler)

      Set the event handler for the underlying transport protocol.

       ssh.setEventHandler(new TransportProtocolEventHandler() {
      
         public void onSocketTimeout(TransportProtocol transport) {
      // Do something to handle the socket timeout
      } public void onDisconnect(TransportProtocol transport) { // Perhaps some clean up? } });
      Parameters:
      eventHandler - The event handler instance to receive transport protocol events
      Since:
      0.2.0
      See Also:
    • setSocketTimeout

      public void setSocketTimeout(int milliseconds)

      Set's the socket timeout (in milliseconds) for the underlying transport provider. This MUST be called prior to connect.

      SshClient ssh = new SshClient(); ssh.setSocketTimeout(30000); ssh.connect("hostname");
      Parameters:
      milliseconds - The number of milliseconds without activity before the timeout event occurs
      Since:
      0.2.0
    • getRemoteEOLString

      public String getRemoteEOLString()

      Return's a rough guess at the server's EOL setting. This is simply derived from the identification string and should not be used as a cast iron proof on the EOL setting.

      Returns:
      The EOL string
      Since:
      0.2.0
    • getConnectionProperties

      public SshConnectionProperties getConnectionProperties()
      Get the connection properties for this connection.
      Returns:
    • authenticate

      public int authenticate(SshAuthenticationClient auth) throws IOException

      Authenticate the user on the remote host.

      To authenticate the user, create an SshAuthenticationClient instance and configure it with the authentication details.

      PasswordAuthenticationClient pwd = new PasswordAuthenticationClient(); pwd.setUsername("root"); pwd.setPassword("xxxxxxxxx"); int result = ssh.authenticate(pwd);

      The method returns a result value will one of the public static values defined in AuthenticationProtocolState. These are

      COMPLETED - The authentication succeeded.
      PARTIAL - The authentication succeeded but a further authentication method is required.
      FAILED - The authentication failed.
      CANCELLED - The user cancelled authentication (can only be returned when the user is prompted for information.

      Parameters:
      auth - A configured SshAuthenticationClient instance ready for authentication
      Returns:
      The authentication result
      Throws:
      IOException - If an IO error occurs during authentication
      Since:
      0.2.0
    • acceptsKey

      public boolean acceptsKey(String username, SshPublicKey key) throws IOException

      Determine whether a private/public key pair will be accepted for public key authentication.

      When using public key authentication, the signing of data could take some time depending upon the available machine resources. By calling this method, you can determine whether the server will accept a key for authentication by providing the public key. The server will verify the key against the user's authorized keys and return true should the public key be authorized. The caller can then proceed with the private key operation.

      Parameters:
      username - The username for authentication
      key - The public key for which authentication will be attempted
      Returns:
      true if the server will accept the key, otherwise false
      Throws:
      IOException - If an IO error occurs during the operation
      SshException
      Since:
      0.2.0
    • connect

      public void connect(String hostname) throws IOException

      Connect the client to the server using default connection properties.

      This call attempts to connect to the hostname specified on the standard SSH port of 22 and uses all the default connection properties. This call is the equivilent of calling:

       SshConnectionProperties properties = new
                                 SshConnectionProperties();
       properties.setHostname("hostname");
       ssh.connect(properties);
       
      Parameters:
      hostname - The hostname of the server to connect
      Throws:
      IOException - If an IO error occurs during the connect operation
      Since:
      0.2.0
      See Also:
    • connect

      public void connect(String hostname, HostKeyVerification hosts) throws IOException

      Connect the client to the server using the default connection properties.

      This call attempts to connect to the hostname specified on the standard SSH port of 22 and uses all the default connection properties. When this method returns the connection has been established, the server's identity been verified and the connection is ready for user authentication. Host key verification will be performed using the host key verification instance provided:

       // Connect and consult $HOME/.ssh/known_hosts
       ssh.connect("hostname", new ConsoleKnownHostsKeyVerification());
       // Connect and allow any host
       ssh.connect("hostname", new
                       IgnoreHostKeyVerification());
       

      You can provide your own host key verification process by implementing the HostKeyVerification interface.

      Parameters:
      hostname - The hostname of the server to connect
      hosts - The host key verification instance to consult for host key validation
      Throws:
      IOException - If an IO error occurs during the connect operation
      Since:
      0.2.0
      See Also:
    • connect

      public void connect(String hostname, int port) throws IOException

      Connect the client to the server on a specified port with default connection properties.

      This call attempts to connect to the hostname and port specified. This call is the equivilent of calling:

      SshConnectionProperties properties = new SshConnectionProperties(); properties.setHostname("hostname"); properties.setPort(10022); ssh.connect(properties);
      Parameters:
      hostname - The hostname of the server to connect
      port - The port to connect
      Throws:
      IOException - If an IO error occurs during the connect operation
      Since:
      0.2.0
      See Also:
    • connect

      public void connect(String hostname, int port, HostKeyVerification hosts) throws IOException

      Connect the client to the server on a specified port with default connection properties.

      This call attempts to connect to the hostname and port specified. When this method returns the connection has been established, the server's identity been verified and the connection is ready for user authentication. Host key verification will be performed using the host key verification instance provided:

       // Connect and consult $HOME/.ssh/known_hosts
       ssh.connect("hostname", new ConsoleKnownHostsKeyVerification());
       // Connect and allow any host
       ssh.connect("hostname", new
                       IgnoreHostKeyVerification());
       

      You can provide your own host key verification process by implementing the HostKeyVerification interface.

      Parameters:
      hostname - The hostname of the server to connect
      port - The port to connect
      hosts - The host key verification instance to consult for host key validation
      Throws:
      IOException - If an IO error occurs during the connect operation
      Since:
      0.2.0
      See Also:
    • connect

      public void connect(SshConnectionProperties properties) throws IOException

      Connect the client to the server with the specified properties.

      This call attempts to connect to using the connection properties specified. When this method returns the connection has been established, the server's identity been verified and the connection is ready for user authentication. To use this method first create a properties instance and set the required fields.

       SshConnectionProperties properties = new
                               SshConnectionProperties();
       properties.setHostname("hostname");
       properties.setPort(10022);
       properties.setPrefCSEncryption("blowfish-cbc");
       ssh.connect(properties);
       

      Host key verification will be performed using ConsoleKnownHostsKeyVerification and so this call is the equivilent of calling:

       ssh.connect("hostname", new ConsoleKnownHostsKeyVerification());
       

      If the key is not matched to any keys already in the $HOME/.ssh/known_hosts file, the user will be prompted via the console to confirm the identity of the remote server. The user will receive the following prompt.

      The host shell.sourceforge.net is currently unknown to the system The host key fingerprint is: 1024: 4c 68 3 d4 5c 58 a6 1d 9d 17 13 24 14 48 ba 99 Do you want to allow this host key? [Yes|No|Always]:

      Selecting the "always" option will write the key to the known_hosts file.

      Parameters:
      properties - The connection properties
      Throws:
      IOException - If an IO error occurs during the connect operation
      Since:
      0.2.0
    • connect

      public void connect(SshConnectionProperties properties, HostKeyVerification hostVerification) throws UnknownHostException, IOException

      Connect the client to the server with the specified properties.

      This call attempts to connect to using the connection properties specified. When this method returns the connection has been established, the server's identity been verified and the connection is ready for user authentication. To use this method first create a properties instance and set the required fields.

       SshConnectionProperties properties = new
                                   SshConnectionProperties();
       properties.setHostname("hostname");
       properties.setPort(22);             // Defaults to 22
       // Set the prefered client->server encryption
       ssh.setPrefCSEncryption("blowfish-cbc");
       // Set the prefered server->client encrpytion
       ssh.setPrefSCEncrpyion("3des-cbc");
       ssh.connect(properties);
       

      Host key verification will be performed using the host key verification instance provided:

       // Connect and consult $HOME/.ssh/known_hosts
       ssh.connect("hostname", new ConsoleKnownHostsKeyVerification());
       // Connect and allow any host
       ssh.connect("hostname", new
                       IgnoreHostKeyVerification());
       
      You can provide your own host key verification process by implementing the HostKeyVerification interface.

      Parameters:
      properties - The connection properties
      hostVerification - The host key verification instance to consult for host key validation
      Throws:
      UnknownHostException - If the host is unknown
      IOException - If an IO error occurs during the connect operation
      Since:
      0.2.0
    • setKexTimeout

      public void setKexTimeout(long seconds) throws IOException

      Sets the timeout value for the key exchange.

      When this time limit is reached the transport protocol will initiate a key re-exchange. The default value is one hour with the minumin timeout being 60 seconds.

      Parameters:
      seconds - The number of seconds beofre key re-exchange
      Throws:
      IOException - If the timeout value is invalid
      Since:
      0.2.0
    • setKexTransferLimit

      public void setKexTransferLimit(long kilobytes) throws IOException

      Sets the key exchance transfer limit in kilobytes.

      Once this amount of data has been transfered the transport protocol will initiate a key re-exchange. The default value is one gigabyte of data with the mimimun value of 10 kilobytes.

      Parameters:
      kilobytes - The data transfer limit in kilobytes
      Throws:
      IOException - If the data transfer limit is invalid
    • setSendIgnore

      public void setSendIgnore(boolean sendIgnore)

      Set's the send ignore flag to send random data packets.

      If this flag is set to true, then the transport protocol will send additional SSH_MSG_IGNORE packets with random data.

      Parameters:
      sendIgnore - true if you want to turn on random packet data, otherwise false
      Since:
      0.2.0
    • setUseDefaultForwarding

      public void setUseDefaultForwarding(boolean useDefaultForwarding)

      Turn the default forwarding manager on/off.

      If this flag is set to false before connection, the client will not create a port forwarding manager. Use this to provide you own forwarding implementation.

      Parameters:
      useDefaultForwarding - Set to false if you not wish to use the default forwarding manager.
      Since:
      0.2.0
    • disconnect

      public void disconnect()

      Disconnect the client.

      Since:
      0.2.0
    • getOutgoingByteCount

      public long getOutgoingByteCount()

      Returns the number of bytes transmitted to the remote server.

      Returns:
      The number of bytes transmitted
      Since:
      0.2.0
    • getIncomingByteCount

      public long getIncomingByteCount()

      Returns the number of bytes received from the remote server.

      Returns:
      The number of bytes received
      Since:
      0.2.0
    • getActiveChannelCount

      public int getActiveChannelCount()

      Returns the number of active channels for this client.

      This is the total count of sessions, port forwarding, sftp, scp and custom channels currently open.

      Returns:
      The number of active channels
      Since:
      0.2.0
    • getActiveChannels

      public List getActiveChannels()

      Returns the list of active channels.

      Returns:
      The list of active channels
      Since:
      0.2.0
    • hasActiveSession

      public boolean hasActiveSession(String type)

      Returns true if there is an active session channel of the specified type.

      When a session is created, it is assigned a default type. For instance, when a session is created it as a type of "uninitialized"; however when a shell is started on the session, the type is set to "shell". This also occurs for commands where the type is set to the command which is executed and subsystems where the type is set to the subsystem name. This allows each session to be saved in the active session channel's list and recalled later. It is also possible to set the session channel's type using the setSessionType method of the SessionChannelClient class.

       if(ssh.hasActiveSession("shell")) {
            SessionChannelClient session =
                 ssh.getActiveSession("shell");
       }
       
      Parameters:
      type - The string specifying the channel type
      Returns:
      true if an active session channel exists, otherwise false
      Since:
      0.2.0
    • getActiveSession

      public SessionChannelClient getActiveSession(String type) throws IOException

      Returns the active session channel of the given type.

      Parameters:
      type - The type fo session channel
      Returns:
      The session channel instance
      Throws:
      IOException - If the session type does not exist
      Since:
      0.2.0
    • isActiveChannel

      public boolean isActiveChannel(Channel channel)
      Determine whether the channel supplied is an active channel
      Parameters:
      channel -
      Returns:
    • openSessionChannel

      public SessionChannelClient openSessionChannel() throws IOException

      Open's a session channel on the remote server.

      A session channel may be used to start the user's shell, execute a command or start a subsystem such as SFTP.

      Returns:
      An new session channel
      Throws:
      IOException - If authentication has not been completed, the server refuses to open the channel or a general IO error occurs
      Since:
      0.2.0
      See Also:
    • openSessionChannel

      public SessionChannelClient openSessionChannel(ChannelEventListener eventListener) throws IOException

      Open's a session channel on the remote server.

      A session channel may be used to start the user's shell, execute a command or start a subsystem such as SFTP.

      Parameters:
      eventListener - an event listner interface to add to the channel
      Returns:
      Throws:
      IOException
      SshException
    • openSftpClient

      public SftpClient openSftpClient() throws IOException

      Open an SFTP client for file transfer operations.

       SftpClient sftp = ssh.openSftpClient();
       sftp.cd("foo");
       sftp.put("somefile.txt");
       sftp.quit();
       
      Returns:
      Returns an initialized SFTP client
      Throws:
      IOException - If an IO error occurs during the operation
      Since:
      0.2.0
      See Also:
    • openSftpClient

      public SftpClient openSftpClient(ChannelEventListener eventListener) throws IOException

      Open an SFTP client for file transfer operations. Adds the supplied event listener to the underlying channel.

      Parameters:
      eventListener -
      Returns:
      Throws:
      IOException
    • hasActiveSftpClient

      public boolean hasActiveSftpClient()
      Determine if there are existing sftp clients open
      Returns:
    • getActiveSftpClient

      public SftpClient getActiveSftpClient() throws IOException
      Get an active sftp client
      Returns:
      Throws:
      IOException
      SshException
    • openScpClient

      public ScpClient openScpClient() throws IOException

      Open an SCP client for file transfer operations where SFTP is not supported.

      Sets the local working directory to the user's home directory

       ScpClient scp = ssh.openScpClient();
       scp.put("somefile.txt");
       
      Returns:
      An initialized SCP client
      Throws:
      IOException - If an IO error occurs during the operation
      Since:
      0.2.0
      See Also:
    • openScpClient

      public ScpClient openScpClient(File cwd) throws IOException

      Open an SCP client for file transfer operations where SFTP is not supported.

      This method sets a local current working directory.

       ScpClient scp = ssh.openScpClient("foo");
       scp.put("somefile.txt");
       
      Parameters:
      cwd - The local directory as the base for all local files
      Returns:
      An intialized SCP client
      Throws:
      IOException - If an IO error occurs during the operation
      Since:
      0.2.0
      See Also:
    • openSftpChannel

      public SftpSubsystemClient openSftpChannel() throws IOException

      Open's an Sftp channel.

      Use this sftp channel if you require a lower level api into the SFTP protocol.

      Returns:
      an initialized sftp subsystem instance
      Throws:
      IOException - if an IO error occurs or the channel cannot be opened
      Since:
      0.2.0
    • openSftpChannel

      public SftpSubsystemClient openSftpChannel(ChannelEventListener eventListener) throws IOException
      Open an SftpSubsystemChannel. For advanced use only
      Parameters:
      eventListener -
      Returns:
      Throws:
      IOException
      SshException
    • openChannel

      public boolean openChannel(Channel channel) throws IOException

      Open's a channel.

      Call this method to open a custom channel. This method is used by all other channel opening methods. For example the openSessionChannel method could be implemented as:

       SessionChannelClient session =
                       new SessionChannelClient();
       if(ssh.openChannel(session)) {
          // Channel is now open
       }
       

      Parameters:
      channel -
      Returns:
      true if the channel was opened, otherwise false
      Throws:
      IOException - if an IO error occurs
      SshException
      Since:
      0.2.0
    • allowChannelOpen

      public void allowChannelOpen(String channelName, ChannelFactory cf) throws IOException

      Instructs the underlying connection protocol to allow channels of the given type to be opened by the server.

      The client does not allow channels to be opened by default. Call this method to allow the server to open channels by providing a ChannelFactory implementation to create instances upon request.

      Parameters:
      channelName - The channel type name
      cf - The factory implementation that will create instances of the channel when a channel open request is recieved.
      Throws:
      IOException - if an IO error occurs
      Since:
      0.2.0
    • denyChannelOpen

      public void denyChannelOpen(String channelName) throws IOException

      Stops the specified channel type from being opended.

      Parameters:
      channelName - The channel type name
      Throws:
      IOException - if an IO error occurs
      Since:
      0.2.1
    • sendGlobalRequest

      public byte[] sendGlobalRequest(String requestName, boolean wantReply, byte[] requestData) throws IOException

      Send a global request to the server.

      The SSH specification provides a global request mechanism which is used for starting/stopping remote forwarding. This is a general mechanism which can be used for other purposes if the server supports the global requests.

      Parameters:
      requestName - The name of the global request
      wantReply - true if the server should send an explict reply
      requestData - the global request data
      Returns:
      true if the global request succeeded or wantReply==false, otherwise false
      Throws:
      IOException - if an IO error occurs
      Since:
      0.2.0