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Ganymed SSH-2: Java based SSH-2 Protocol Implementation
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/*
* Copyright (c) 2006-2011 Christian Plattner. All rights reserved.
* Please refer to the LICENSE.txt for licensing details.
*/
package ch.ethz.ssh2;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.security.SecureRandom;
import ch.ethz.ssh2.channel.Channel;
import ch.ethz.ssh2.channel.ChannelManager;
import ch.ethz.ssh2.channel.X11ServerData;
/**
* A Session is a remote execution of a program. "Program" means
* in this context either a shell, an application or a system command. The
* program may or may not have a tty. Only one single program can be started on
* a session. However, multiple sessions can be active simultaneously.
*
* @author Christian Plattner
* @version $Id: Session.java 96 2014-04-08 15:14:37Z [email protected] $
*/
public class Session
{
private ChannelManager cm;
private Channel cn;
private boolean flag_pty_requested = false;
private boolean flag_x11_requested = false;
private boolean flag_execution_started = false;
private boolean flag_closed = false;
private String x11FakeCookie = null;
private final SecureRandom rnd;
protected Session(ChannelManager cm, SecureRandom rnd) throws IOException
{
this.cm = cm;
this.cn = cm.openSessionChannel();
this.rnd = rnd;
}
/**
* Basically just a wrapper for lazy people - identical to calling
* requestPTY("dumb", 0, 0, 0, 0, null).
*
* @throws IOException
*/
public void requestDumbPTY() throws IOException
{
requestPTY("dumb", 0, 0, 0, 0, null);
}
/**
* Basically just another wrapper for lazy people - identical to calling
* requestPTY(term, 0, 0, 0, 0, null).
*
* @throws IOException
*/
public void requestPTY(String term) throws IOException
{
requestPTY(term, 0, 0, 0, 0, null);
}
/**
* Allocate a pseudo-terminal for this session.
*
* This method may only be called before a program or shell is started in
* this session.
*
* Different aspects can be specified:
*
*
* - The TERM environment variable value (e.g., vt100)
* - The terminal's dimensions.
* - The encoded terminal modes.
*
* Zero dimension parameters are ignored. The character/row dimensions
* override the pixel dimensions (when nonzero). Pixel dimensions refer to
* the drawable area of the window. The dimension parameters are only
* informational. The encoding of terminal modes (parameter
* terminal_modes) is described in RFC4254.
*
* @param term The TERM environment variable value (e.g., vt100)
* @param term_width_characters terminal width, characters (e.g., 80)
* @param term_height_characters terminal height, rows (e.g., 24)
* @param term_width_pixels terminal width, pixels (e.g., 640)
* @param term_height_pixels terminal height, pixels (e.g., 480)
* @param terminal_modes encoded terminal modes (may be null)
* @throws IOException
*/
public void requestPTY(String term, int term_width_characters, int term_height_characters, int term_width_pixels,
int term_height_pixels, byte[] terminal_modes) throws IOException
{
if (term == null)
throw new IllegalArgumentException("TERM cannot be null.");
if ((terminal_modes != null) && (terminal_modes.length > 0))
{
if (terminal_modes[terminal_modes.length - 1] != 0)
throw new IOException("Illegal terminal modes description, does not end in zero byte");
}
else
terminal_modes = new byte[]{0};
synchronized (this)
{
/* The following is just a nicer error, we would catch it anyway later in the channel code */
if (flag_closed)
throw new IOException("This session is closed.");
if (flag_pty_requested)
throw new IOException("A PTY was already requested.");
if (flag_execution_started)
throw new IOException(
"Cannot request PTY at this stage anymore, a remote execution has already started.");
flag_pty_requested = true;
}
cm.requestPTY(cn, term, term_width_characters, term_height_characters, term_width_pixels, term_height_pixels,
terminal_modes);
}
/**
* Tells the server that the size of the terminal has changed.
*
* See {@link #requestPTY(String, int, int, int, int, byte[])} for more details about how parameters are interpreted.
*
* @param term_width_characters
* terminal width, characters (e.g., 80)
* @param term_height_characters
* terminal height, rows (e.g., 24)
* @param term_width_pixels
* terminal width, pixels (e.g., 640)
* @param term_height_pixels
* terminal height, pixels (e.g., 480)
* @throws IOException
*/
public void requestWindowChange(int term_width_characters, int term_height_characters, int term_width_pixels,
int term_height_pixels) throws IOException
{
synchronized (this)
{
/* The following is just a nicer error, we would catch it anyway later in the channel code */
if (flag_closed)
throw new IOException("This session is closed.");
if (!flag_pty_requested)
throw new IOException("A PTY was not requested.");
}
cm.requestWindowChange(cn, term_width_characters, term_height_characters, term_width_pixels, term_height_pixels);
}
/**
* Request X11 forwarding for the current session.
*
* You have to supply the name and port of your X-server.
*
* This method may only be called before a program or shell is started in
* this session.
*
* @param hostname the hostname of the real (target) X11 server (e.g., 127.0.0.1)
* @param port the port of the real (target) X11 server (e.g., 6010)
* @param cookie if non-null, then present this cookie to the real X11 server
* @param singleConnection if true, then the server is instructed to only forward one single
* connection, no more connections shall be forwarded after first, or after the session
* channel has been closed
* @throws IOException
*/
public void requestX11Forwarding(String hostname, int port, byte[] cookie, boolean singleConnection)
throws IOException
{
if (hostname == null)
throw new IllegalArgumentException("hostname argument may not be null");
synchronized (this)
{
/* The following is just a nicer error, we would catch it anyway later in the channel code */
if (flag_closed)
throw new IOException("This session is closed.");
if (flag_x11_requested)
throw new IOException("X11 forwarding was already requested.");
if (flag_execution_started)
throw new IOException(
"Cannot request X11 forwarding at this stage anymore, a remote execution has already started.");
flag_x11_requested = true;
}
/* X11ServerData - used to store data about the target X11 server */
X11ServerData x11data = new X11ServerData();
x11data.hostname = hostname;
x11data.port = port;
x11data.x11_magic_cookie = cookie; /* if non-null, then present this cookie to the real X11 server */
/* Generate fake cookie - this one is used between remote clients and the ganymed proxy */
byte[] fakeCookie = new byte[16];
String hexEncodedFakeCookie;
/* Make sure that this fake cookie is unique for this connection */
while (true)
{
rnd.nextBytes(fakeCookie);
/* Generate also hex representation of fake cookie */
StringBuilder tmp = new StringBuilder(32);
for (int i = 0; i < fakeCookie.length; i++)
{
String digit2 = Integer.toHexString(fakeCookie[i] & 0xff);
tmp.append((digit2.length() == 2) ? digit2 : "0" + digit2);
}
hexEncodedFakeCookie = tmp.toString();
/* Well, yes, chances are low, but we want to be on the safe side */
if (cm.checkX11Cookie(hexEncodedFakeCookie) == null)
break;
}
/* Ask for X11 forwarding */
cm.requestX11(cn, singleConnection, "MIT-MAGIC-COOKIE-1", hexEncodedFakeCookie, 0);
/* OK, that went fine, get ready to accept X11 connections... */
/* ... but only if the user has not called close() in the meantime =) */
synchronized (this)
{
if (flag_closed == false)
{
this.x11FakeCookie = hexEncodedFakeCookie;
cm.registerX11Cookie(hexEncodedFakeCookie, x11data);
}
}
/* Now it is safe to start remote X11 programs */
}
/**
* Execute a command on the remote machine.
*
* @param cmd The command to execute on the remote host.
* @throws IOException
*/
public void execCommand(String cmd) throws IOException
{
this.execCommand(cmd, null);
}
/**
* Execute a command on the remote machine.
*
* @param cmd The command to execute on the remote host.
* @param charsetName The charset used to convert between Java Unicode Strings and byte encodings
* @throws IOException
*/
public void execCommand(String cmd, String charsetName) throws IOException
{
if (cmd == null)
throw new IllegalArgumentException("cmd argument may not be null");
synchronized (this)
{
/* The following is just a nicer error, we would catch it anyway later in the channel code */
if (flag_closed)
throw new IOException("This session is closed.");
if (flag_execution_started)
throw new IOException("A remote execution has already started.");
flag_execution_started = true;
}
cm.requestExecCommand(cn, cmd, charsetName);
}
/**
* Start a shell on the remote machine.
*
* @throws IOException
*/
public void startShell() throws IOException
{
synchronized (this)
{
/* The following is just a nicer error, we would catch it anyway later in the channel code */
if (flag_closed)
throw new IOException("This session is closed.");
if (flag_execution_started)
throw new IOException("A remote execution has already started.");
flag_execution_started = true;
}
cm.requestShell(cn);
}
/**
* Start a subsystem on the remote machine.
* Unless you know what you are doing, you will never need this.
*
* @param name the name of the subsystem.
* @throws IOException
*/
public void startSubSystem(String name) throws IOException
{
if (name == null)
throw new IllegalArgumentException("name argument may not be null");
synchronized (this)
{
/* The following is just a nicer error, we would catch it anyway later in the channel code */
if (flag_closed)
throw new IOException("This session is closed.");
if (flag_execution_started)
throw new IOException("A remote execution has already started.");
flag_execution_started = true;
}
cm.requestSubSystem(cn, name);
}
public int getState()
{
return cn.getState();
}
public InputStream getStdout()
{
return cn.getStdoutStream();
}
public InputStream getStderr()
{
return cn.getStderrStream();
}
public OutputStream getStdin()
{
return cn.getStdinStream();
}
/**
* This method blocks until there is more data available on either the
* stdout or stderr InputStream of this Session. Very useful
* if you do not want to use two parallel threads for reading from the two
* InputStreams. One can also specify a timeout. NOTE: do NOT call this
* method if you use concurrent threads that operate on either of the two
* InputStreams of this Session (otherwise this method may
* block, even though more data is available).
*
* @param timeout The (non-negative) timeout in ms. 0 means no
* timeout, the call may block forever.
* @return
* 0 if no more data will arrive.1 if more data is available.-1 if a timeout occurred.
* @throws IOException
* @deprecated This method has been replaced with a much more powerful wait-for-condition
* interface and therefore acts only as a wrapper.
*/
public int waitUntilDataAvailable(long timeout) throws IOException
{
if (timeout < 0)
throw new IllegalArgumentException("timeout must not be negative!");
int conditions = cm.waitForCondition(cn, timeout, ChannelCondition.STDOUT_DATA | ChannelCondition.STDERR_DATA
| ChannelCondition.EOF);
if ((conditions & ChannelCondition.TIMEOUT) != 0)
return -1;
if ((conditions & (ChannelCondition.STDOUT_DATA | ChannelCondition.STDERR_DATA)) != 0)
return 1;
/* Here we do not need to check separately for CLOSED, since CLOSED implies EOF */
if ((conditions & ChannelCondition.EOF) != 0)
return 0;
throw new IllegalStateException("Unexpected condition result (" + conditions + ")");
}
/**
* This method blocks until certain conditions hold true on the underlying SSH-2 channel.
*
* This method returns as soon as one of the following happens:
*
* - at least of the specified conditions (see {@link ChannelCondition}) holds true
* - timeout > 0 and a timeout occured (TIMEOUT will be set in result conditions)
*
- the underlying channel was closed (CLOSED will be set in result conditions)
*
*
* In any case, the result value contains ALL current conditions, which may be more
* than the specified condition set (i.e., never use the "==" operator to test for conditions
* in the bitmask, see also comments in {@link ChannelCondition}).
*
* Note: do NOT call this method if you want to wait for STDOUT_DATA or STDERR_DATA and
* there are concurrent threads (e.g., StreamGobblers) that operate on either of the two
* InputStreams of this Session (otherwise this method may
* block, even though more data is available in the StreamGobblers).
*
* @param condition_set a bitmask based on {@link ChannelCondition} values
* @param timeout non-negative timeout in ms, 0 means no timeout
* @return all bitmask specifying all current conditions that are true
*/
public int waitForCondition(int condition_set, long timeout) throws IOException {
if (timeout < 0)
throw new IllegalArgumentException("timeout must be non-negative!");
return cm.waitForCondition(cn, timeout, condition_set);
}
/**
* Get the exit code/status from the remote command - if available. Be
* careful - not all server implementations return this value. It is
* generally a good idea to call this method only when all data from the
* remote side has been consumed (see also the method).
*
* @return An Integer holding the exit code, or
* null if no exit code is (yet) available.
*/
public Integer getExitStatus()
{
return cn.getExitStatus();
}
/**
* Get the name of the signal by which the process on the remote side was
* stopped - if available and applicable. Be careful - not all server
* implementations return this value.
*
* @return An String holding the name of the signal, or
* null if the process exited normally or is still
* running (or if the server forgot to send this information).
*/
public String getExitSignal()
{
return cn.getExitSignal();
}
/**
* Close this session. NEVER forget to call this method to free up resources -
* even if you got an exception from one of the other methods (or when
* getting an Exception on the Input- or OutputStreams). Sometimes these other
* methods may throw an exception, saying that the underlying channel is
* closed (this can happen, e.g., if the other server sent a close message.)
* However, as long as you have not called the close()
* method, you may be wasting (local) resources.
*/
public void close()
{
synchronized (this)
{
if (flag_closed)
return;
flag_closed = true;
if (x11FakeCookie != null)
cm.unRegisterX11Cookie(x11FakeCookie, true);
try
{
cm.closeChannel(cn, "Closed due to user request", true);
}
catch (IOException ignored)
{
}
}
}
}