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**vngx-jsch** (beta) is an updated version of the popular JSch SSH library
written in pure Java. It has been updated to Java 6 with all the latest
language features and improved code clarity.
/*
* Copyright (c) 2002-2010 Atsuhiko Yamanaka, JCraft,Inc. All rights reserved.
* Copyright (c) 2010-2011 Michael Laudati, N1 Concepts LLC.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
*
* 3. The names of the authors may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED WARRANTIES,
* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
* FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL JCRAFT,
* INC. OR ANY CONTRIBUTORS TO THIS SOFTWARE BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA,
* OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
package org.vngx.jsch;
import static org.vngx.jsch.constants.ConnectionProtocol.*;
import static org.vngx.jsch.constants.TransportLayerProtocol.*;
import org.vngx.jsch.exception.JSchException;
import org.vngx.jsch.util.Logger.Level;
import java.io.PipedInputStream;
import java.io.PipedOutputStream;
import java.io.InputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.util.concurrent.atomic.AtomicInteger;
/**
* Default base implementation of a SSH channel and provides a centralized pool
* for tracking all channel instances.
*
* The connection protocol specifies a mechanism to multiplex multiple streams
* (channels) of data over the confidential and authenticated transport. It
* also specifies channels for accessing an interactive shell, for
* proxy-forwarding various external protocols over the secure transport
* (including arbitrary TCP/IP protocols), and for accessing secure subsystems
* on the server host.
*
* All terminal sessions, forwarded connections, etc., are channels. Either side
* may open a channel. Multiple channels are multiplexed into a single
* connection.
*
* Channels are identified by numbers at each end. The number referring to a
* channel may be different on each side. Requests to open a channel contain
* the sender's channel number. Any other channel-related messages contain the
* recipient's channel number for the channel.
*
* Channels are flow-controlled. No data may be sent to a channel until a
* message is received to indicate that window space is available.
*
* The initial assignments for the 'reason code' values and 'description' values
* are given in the table below. Note that the values for the 'reason code' are
* given in decimal format for readability, but they are actually uint32 values.
*
* Symbolic Name reason code
* ------------- -----------
* SSH_OPEN_ADMINISTRATIVELY_PROHIBITED 1
* SSH_OPEN_CONNECT_FAILED 2
* SSH_OPEN_UNKNOWN_CHANNEL_TYPE 3
* SSH_OPEN_RESOURCE_SHORTAGE 4
*
* TODO Once a channel has failed connecting or has disconnected, it cannot be
* reused to connect again. Calling connect() methods should throw an exception
* if the state is closed.
*
* @author Atsuhiko Yamanaka
* @author Michael Laudati
*/
public abstract class Channel implements Runnable {
/** Generator used to create unique IDs for each channel. */
private final static AtomicInteger ID_GENERATOR = new AtomicInteger();
/** Session instance channel belongs to. */
final Session _session;
/** Unique ID for this channel instance. */
final int _id;
/** Type of channel instance. */
final ChannelType _channelType;
/** Channel type name in bytes to send to server when opening channel. */
final byte[] _type;
/** True if the channel is connected. */
boolean _connected = false;
/** Connection timeout in milliseconds (zero indicates no timeout). */
int _connectTimeout = 0;
/** Thread which is running the channel instance while connected. */
Thread _thread;
/** Channel ID assigned by SSH server to delegate packets. */
int _recipient = -1;
/** Local maximum window size. */
int _localWindowMaxSize = 0x100000;
/** Local initial window size. */
int _localWindowSize = _localWindowMaxSize;
/** Local maximum packet size. */
int _localMaxPacketSize = 0x4000;
/** Remote initial window size; */
long _remoteWindowSize = 0;
/** Remote maximum packet size. */
int _remoteMaxPacketSize = 0;
/** Input/output helper for channel. */
IO _io;
/** True if the local output has reached EOF. */
boolean _eofLocal = false;
/** True if the remote output has reached EOF. */
boolean _eofRemote = false;
/** True if the channel is closed. */
boolean _closed = false;
/** Exit status of channel (determined by remote host). */
int _exitstatus = -1;
/** Reply status from a channel request (-1 waiting, 0 failure, 1 success). */
int _reply = 0;
/** The number of outstanding global requests waiting to be notified for this channel. */
int _notifyMe = 0;
/**
* Creates a new instance of Channel of the specified type and
* adds the instance to the internally maintained pool, incrementing the
* pool index and setting the unique ID of this channel.
*
* @param session to create channel on
* @param channelType
*/
Channel(Session session, ChannelType channelType) {
this(session, channelType, channelType._typeName);
}
/**
* Creates a new instance of Channel of the specified type and
* adds the instance to the session's internal channel pool and set the
* globally unique ID of this channel.
*
* Constructor should remain with default access since only Session should
* be creating instances.
*
* @param session the to create channel on
* @param channelType of specific channel instance
* @param type of channel to send when connecting channel
*/
Channel(Session session, ChannelType channelType, String type) {
_id = ID_GENERATOR.getAndIncrement(); // Generate globally unique ID for channel
// Set the session of channel and add to session's channel pool
_session = session;
_session.addChannel(this);
// Set channel type and type name sent to SSH server in connect request
_channelType = channelType;
_type = Util.str2byte(type);
}
/**
* Initializes the channel. Specific implementations can override this
* method to perform any initialization before the channel connects. By
* default the method does nothing.
*
* @throws JSchException if any errors occur
*/
void init() throws JSchException { }
/**
* Connects the channel through the current session without any timeout.
* This is the equivalent of calling connect(0).
*
* @throws JSchException if any errors occur
*/
public void connect() throws JSchException {
connect(0);
}
/**
* Connects the channel through the current session with the specified
* timeout in milliseconds.
*
* @param connectTimeout in milliseconds
* @throws JSchException if any errors occur
*/
public void connect(int connectTimeout) throws JSchException {
if( isConnected() ) {
throw new JSchException("Channel is already connected");
} else if( !_session.isConnected() ) {
throw new JSchException("Session is not connected");
}
_connectTimeout = connectTimeout; // Set connection timeout
try {
Buffer buffer = new Buffer(100);
Packet packet = new Packet(buffer);
// send
// byte SSH_MSG_CHANNEL_OPEN(90)
// string channel type //
// uint32 sender channel // 0
// uint32 initial window size // 0x100000(65536)
// uint32 maxmum packet size // 0x4000(16384)
packet.reset();
buffer.putByte(SSH_MSG_CHANNEL_OPEN);
buffer.putString(_type);
buffer.putInt(_id);
buffer.putInt(_localWindowSize);
buffer.putInt(_localMaxPacketSize);
_session.write(packet);
int retry = 1000; // Note: Max timeout is 50 seconds (1000 retries * 50ms sleep)
long start = System.currentTimeMillis();
while( _recipient == -1 && _session.isConnected() && retry-- > 0 ) {
if( _connectTimeout > 0L && (System.currentTimeMillis() - start) > _connectTimeout ) {
throw new JSchException("Failed to open channel: connection timeout after " + _connectTimeout + " ms");
}
try { Thread.sleep(50); } catch(Exception ee) { /* Ignore error. */ }
}
if( !_session.isConnected() ) {
throw new JSchException("Failed to open channel: session is not connected");
} else if( retry == 0 ) {
throw new JSchException("Failed to open channel: no response");
}
/*
* At the failure in opening the channel on the sshd,
* 'SSH_MSG_CHANNEL_OPEN_FAILURE' will be sent from sshd and it will
* be processed in Session#run().
*/
if( isClosed() ) {
throw new JSchException("Failed to open channel: "+_exitstatus);
}
_connected = true;
start();
} catch(JSchException je) {
_connected = false;
disconnect();
throw je;
} catch(Exception e) {
_connected = false;
disconnect();
throw new JSchException("Failed to open channel "+getClass().getSimpleName()+": "+_exitstatus, e);
}
}
/**
* Starts the channel after connection through the session. Implementations
* can override this method to define specific behavior.
*
* TODO Should this method be publicly exposed? It's always called after
* a successful connection... should external code ever need to call it?
*
* @throws JSchException
*/
public void start() throws JSchException { }
/**
* Sets the InputStream to read channel input from SSH server.
*
* @param in stream to read channel data
*/
public void setInputStream(InputStream in) {
_io.setInputStream(in, false);
}
/**
* Sets the InputStream to read channel input from SSH server
* and does not close the stream if specified.
*
* @param in stream to read channel data
* @param dontClose true to not close stream when channel closes
*/
public void setInputStream(InputStream in, boolean dontClose) {
_io.setInputStream(in, dontClose);
}
/**
* Sets the OutputStream to write channel output to SSH server.
*
* @param out stream to send channel data
*/
public void setOutputStream(OutputStream out) {
_io.setOutputStream(out, false);
}
/**
* Sets the OutputStream to write channel output to SSH server
* and does not close the stream if specified.
*
* @param out stream to send channel data
* @param dontClose true to not close stream when channel closes
*/
public void setOutputStream(OutputStream out, boolean dontClose) {
_io.setOutputStream(out, dontClose);
}
/**
* Sets the OutputStream to write extended channel output to
* the SSH server.
*
* @param out stream to send extended output data
*/
public void setExtOutputStream(OutputStream out) {
_io.setExtOutputStream(out, false);
}
/**
* Sets the OutputStream to write extended channel output to
* the SSH server and does not close the stream if specified.
*
* @param out stream to send extended output data
* @param dontClose true to not close stream when channel closes
*/
public void setExtOutputStream(OutputStream out, boolean dontClose) {
_io.setExtOutputStream(out, dontClose);
}
/**
* Returns a new instance of InputStream for reading channel
* output.
*
* @return new instance of InputStream for reading channel output
* @throws IOException if any errors occur
*/
public InputStream getInputStream() throws IOException {
PipedInputStream in = new PipedInputStream(32 * 1024); // TODO this value should be customizable
_io.setOutputStream(new PipedOutputStream(in), false);
return in;
}
/**
* Returns a new instance of InputStream for reading the
* extended data of the channel.
*
* @return new instance of InputStream for reading extended data output
* @throws IOException if any errors occur
*/
public InputStream getExtInputStream() throws IOException {
PipedInputStream in = new PipedInputStream(32 * 1024); // TODO this value should be customizable
_io.setExtOutputStream(new PipedOutputStream(in), false);
return in;
}
/**
* Returns a new instance of OutputStream for writing output to
* the channel. A new instance is returned for each invocation rather than
* the same instance for use in a multi-threaded environment to preclude the
* need for external synchronization. (Two threads could be writing data to
* the channel concurrently)
*
* @return new instance of OutputStream to write output to channel
* @throws IOException if any errors occur
*/
public OutputStream getOutputStream() throws IOException {
return new ChannelOutputStream();
}
/**
* Returns true if the remote output has reached EOF.
*
* @return true if remote output is EOF
*/
public final boolean isEOF() {
return _eofRemote;
}
/**
* Sets the recipient ID sent by the server for the channel instance.
*
* @param recipient id
*/
final void setRecipient(int recipient) {
_recipient = recipient;
}
/**
* Returns the recipient ID set by the server for this channel instance.
*
* @return recipient ID
*/
final int getRecipient() {
return _recipient;
}
/**
* Sets the local maximum window size in bytes.
*
* @param localWindowMaxSize in bytes
*/
final void setLocalWindowSizeMax(int localWindowMaxSize) {
_localWindowMaxSize = localWindowMaxSize;
}
/**
* Sets the local window size in bytes.
*
* @param localWindowSize in bytes
*/
final void setLocalWindowSize(int localWindowSize) {
_localWindowSize = localWindowSize;
}
/**
* Sets the local maximum packet size in bytes.
*
* @param localPacketSize in bytes
*/
final void setLocalPacketSize(int localPacketSize) {
_localMaxPacketSize = localPacketSize;
}
/**
* Sets the remote window size in bytes.
*
* @param remoteWindowSize in bytes
*/
synchronized final void setRemoteWindowSize(long remoteWindowSize) {
_remoteWindowSize = remoteWindowSize;
}
/**
* Adds the specified amount in bytes to the remote window size.
*
* @param addRemoteWindowSize in bytes
*/
synchronized final void addRemoteWindowSize(int addRemoteWindowSize) {
_remoteWindowSize += addRemoteWindowSize;
if( _notifyMe > 0 ) {
notifyAll();
}
}
/**
* Sets the remote maximum packet size in bytes.
*
* @param remotePacketSize in bytes
*/
final void setRemotePacketSize(int remotePacketSize) {
_remoteMaxPacketSize = remotePacketSize;
}
/**
* Initializes the channel with its recipient ID, the remote window size
* and the remote packet size.
*
* @param buf from session (open channel confirmation response)
*/
void initChannel(Buffer buffer) {
setRecipient(buffer.getInt());
setRemoteWindowSize(buffer.getUInt());
setRemotePacketSize(buffer.getInt());
}
/**
* Writes the specified data to the channel's output stream.
*
* @param buffer data to write
* @param offset
* @param length
* @throws IOException if any errors occur
*/
void write(byte[] buffer, int offset, int length) throws IOException {
try { // Only catch null pointer in case IO is null from being closed
_io.put(buffer, offset, length);
} catch(NullPointerException e) { /* Ignore error. */ }
}
/**
* Writes the specified data to the channel's extended data output stream.
*
* @param buffer data to write
* @param offset
* @param length
* @throws IOException if any errors occur
*/
final void writeExt(byte[] buffer, int offset, int length) throws IOException {
try { // Only catch null pointer in case IO is null from being closed
_io.putExt(buffer, offset, length);
} catch(NullPointerException e) { /* Ignore error. */ }
}
/**
* Notifies the channel that the remote stream has reached EOF (end of
* file) and closes the channel's output stream.
*/
final void eofRemote() {
_eofRemote = true;
if( _io != null ) {
_io.closeOut(); // Close output stream since no more data will come
}
}
/**
* Sends an EOF (end of file) message for the local stream and sets the
* state as EOF locally.
*/
final void eof() {
if( _eofLocal ) {
return;
}
_eofLocal = true;
try {
synchronized( this ) {
if( !_closed ) {
Buffer buffer = new Buffer(100);
Packet packet = new Packet(buffer);
packet.reset();
buffer.putByte(SSH_MSG_CHANNEL_EOF);
buffer.putInt(_recipient);
_session.write(packet);
}
}
} catch(Exception e) {
/* Ignore error, don't bubble exception. */
JSch.getLogger().log(Level.DEBUG, "Failed to send channel EOF local", e);
}
}
/**
* Closes the channel. When a party will no longer send more data to a
* channel, it should send SSH_MSG_CHANNEL_EOF.
*
* byte SSH_MSG_CHANNEL_EOF
* uint32 recipient_channel
*
* No explicit response is sent to this message. However, the application
* may send EOF to whatever is at the other end of the channel. Note that
* the channel remains open after this message, and more data may still be
* sent in the other direction. This message does not consume window space
* and can be sent even if no window space is available.
*
* When either party wishes to terminate the channel, it sends
* SSH_MSG_CHANNEL_CLOSE. Upon receiving this message, a party MUST send
* back a SSH_MSG_CHANNEL_CLOSE unless it has already sent this message for
* the channel. The channel is considered closed for a party when it has
* both sent and received SSH_MSG_CHANNEL_CLOSE, and the party may then
* reuse the channel number. A party MAY send SSH_MSG_CHANNEL_CLOSE without
* having sent or received SSH_MSG_CHANNEL_EOF.
*
* byte SSH_MSG_CHANNEL_CLOSE
* uint32 recipient_channel
*
* This message does not consume window space and can be sent even if no
* window space is available. It is recommended that any data sent before
* this message is delivered to the actual destination, if possible.
*/
private void close() {
if( _closed ) {
return;
}
_closed = _eofLocal = _eofRemote = true;
try { // Notify SSH server channel is being closed!
synchronized( this ) {
Buffer buffer = new Buffer(100);
Packet packet = new Packet(buffer);
packet.reset();
buffer.putByte(SSH_MSG_CHANNEL_CLOSE);
buffer.putInt(_recipient);
_session.write(packet);
}
} catch(Exception e) {
/* Ignore error, don't bubble exception. */
JSch.getLogger().log(Level.DEBUG, "Failed to send channel close", e);
}
}
/**
* Returns true if this channel is closed.
*
* @return channel is closed for input/output
*/
public final boolean isClosed() {
return _closed;
}
/**
* Disconnects the channel from the SSH server and cleans up any open
* resources. Calling this method when the channel is not connected has no
* effect.
*/
public final void disconnect() {
try {
synchronized( this ) {
if( !_connected ) {
return;
}
_connected = false;
}
close(); // Switch close/eof flags and send close message to server
_thread = null; // Exits any run() loops dependent on thread being not null
if( _io != null ) {
_io.close(); // Close any open IO streams for this channel
}
} finally {
// Remove channel from session's pool after closing it
_session.removeChannel(this);
}
}
/**
* Returns true if the channel is currently connected to the SSH server.
*
* @return true if session and channel are connected to SSH server
*/
public final boolean isConnected() {
return _session != null && _session.isConnected() && _connected;
}
/**
* Sends the specified signal for this channel to the SSH server. A signal
* can be delivered to the remote process/service using the following
* message. Some systems may not implement signals, in which case they
* should ignore this message.
*
* @param signal to send
* @throws Exception if any errors occur
*/
public final void sendSignal(String signal) throws Exception {
RequestSignal request = new RequestSignal();
request.setSignal(signal);
request.request(_session, this);
}
/**
* Sets the exit status code returned by the SSH server for the channel.
* This method should only be called by the parent Session when an exit
* status message is returned for the channel.
*
* @param status code
*/
final void setExitStatus(int status) {
_exitstatus = status;
}
/**
* Returns the exit status code returned by the SSH server for the channel.
* When the command running at the other end terminates, the following
* message can be sent to return the exit status of the command. Returning
* the status is recommended. No acknowledgement is sent for this message.
* The channel needs to be closed with SSH_MSG_CHANNEL_CLOSE after this
* message.
*
* The remote command may also terminate violently due to a signal. Such a
* condition can be indicated by the following message. A zero
* 'exit_status' usually means that the command terminated successfully.
*
* @return exit status code
*/
public final int getExitStatus() {
return _exitstatus;
}
/**
* Returns the Session instance this channel is opened on.
*
* @return session instance
*/
public final Session getSession() {
return _session;
}
/**
* Returns the unique ID for this channel.
*
* @return unique ID for channel
*/
public final int getId() {
return _id;
}
/**
* Returns the channel type.
*
* @return channel type
*/
public final ChannelType getType() {
return _channelType;
}
/**
* Sends a channel open confirmation message to the SSH server indicating
* the channel was successfully opened.
*
* @throws Exception if any errors occur
*/
final void sendOpenConfirmation() throws Exception {
// byte SSH_MSG_CHANNEL_OPEN_CONFIRMATION
// uint32 recipient channel
// uint32 sender channel
// uint32 initial window size
// uint32 maximum packet size
// .... channel type specific data follows
Buffer buffer = new Buffer(100);
Packet packet = new Packet(buffer);
packet.reset();
buffer.putByte(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
buffer.putInt(_recipient);
buffer.putInt(_id);
buffer.putInt(_localWindowSize);
buffer.putInt(_localMaxPacketSize);
_session.write(packet);
}
/**
* Sends a channel open failure message to the SSH server with the specified
* reason code. A channel open failure message should be sent whenever a
* channel fails to open.
*
* @param reasonCode to send to server
*/
final void sendOpenFailure(int reasonCode) {
/* Wrap the send in a try/catch to prevent any errors from stopping the
* channel from completing it's disconnect clean up.
*/
try {
// byte SSH_MSG_CHANNEL_OPEN_FAILURE
// uint32 recipient channel
// uint32 reason code
// string description in ISO-10646 UTF-8 encoding [RFC3629]
// string language tag [RFC3066]
Buffer buffer = new Buffer(100);
Packet packet = new Packet(buffer);
packet.reset();
buffer.putByte(SSH_MSG_CHANNEL_OPEN_FAILURE);
buffer.putInt(_recipient);
buffer.putInt(reasonCode);
buffer.putString("open failed");
buffer.putString("");
_session.write(packet);
} catch(Exception e) {
/* Ignore error, don't bubble exception. */
JSch.getLogger().log(Level.WARN, "Failed to send channel open failure", e);
}
}
/**
* Implementation of OutputStream for writing output to this
* channel.
*
* @author Atsuhiko Yamanaka
* @author Michael Laudati
*/
final class ChannelOutputStream extends OutputStream {
/** Current length of data in stream ready to be sent/flushed. */
private int __dataLen = 0;
/** Buffer for sending output through channel. */
private Buffer __outBuffer;
/** Packet for sending output through channel. */
private Packet __outPacket;
/** True if this output stream is currently closed. */
private boolean __closed = false;
/** Temporary buffer for writing single byte of data. */
private final byte[] __b = new byte[1];
/**
* Initializes the stream for sending output over channel.
*
* @throws IOException
*/
private synchronized void init() throws IOException {
// Initialize the buffer and packet instances
__outBuffer = new Buffer(_remoteMaxPacketSize);
__outPacket = new Packet(__outBuffer);
// Check if output buffer is too small for writing data (based on remote packet size)
if( __outBuffer.buffer.length - (14 + 0) - 32 - 20 <= 0 ) {
__outBuffer = null;
__outPacket = null;
throw new IOException("Failed to initialize output of channel, remote packet size too small");
}
}
@Override
public void write(int b) throws IOException {
__b[0] = (byte) b;
write(__b, 0, 1);
}
@Override
public void write(byte[] buffer, int offset, int length) throws IOException {
if( __closed ) {
throw new IOException("Channel OutputStream already closed");
} else if( __outPacket == null ) {
init();
}
while( length > 0 ) {
int writeLen = length;
if( length > __outBuffer.buffer.length - (14 + __dataLen) - 32 - 20 ) {
writeLen = __outBuffer.buffer.length - (14 + __dataLen) - 32 - 20;
}
if( writeLen <= 0 ) {
flush();
continue;
}
System.arraycopy(buffer, offset, __outBuffer.buffer, 14 + __dataLen, writeLen);
__dataLen += writeLen;
offset += writeLen;
length -= writeLen;
}
}
@Override
public void flush() throws IOException {
if( __closed ) {
throw new IOException("Channel OutputStream already closed");
} else if( __dataLen == 0 ) {
return; // Nothing to write
}
__outPacket.reset();
__outBuffer.putByte(SSH_MSG_CHANNEL_DATA);
__outBuffer.putInt(_recipient);
__outBuffer.putInt(__dataLen);
__outBuffer.skip(__dataLen);
try {
int len = __dataLen;
__dataLen = 0; // Reset data length
_session.write(__outPacket, Channel.this, len);
} catch(Exception e) {
close(); // Close the stream if an error has occurred
throw new IOException("Failed to flush channel data: "+e, e);
}
}
@Override
public void close() throws IOException {
if( __closed ) {
return;
}
// If there's data, flush it before closing
if( __dataLen > 0 ) {
if( __outPacket == null ) {
try {
init();
} catch(IOException e) {
return; // close should finish silently
}
}
flush();
}
Channel.this.eof(); // Notify SSH server end of file for channel
__closed = true;
}
}
}