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+# Copyright (C) 2012 Yipit, Inc <coders@yipit.com>
+#
+# This file is part of paramiko.
+#
+# Paramiko is free software; you can redistribute it and/or modify it under the
+# terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation; either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
+# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+# A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+# details.
+#
+# You should have received a copy of the GNU Lesser General Public License
+# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
+# 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+
+"""
+L{ProxyCommand}.
+"""
+
+import os
+from shlex import split as shlsplit
+import signal
+from subprocess import Popen, PIPE
+
+from paramiko.ssh_exception import ProxyCommandFailure
+
+
+class ProxyCommand(object):
+ """
+ Wraps a subprocess running ProxyCommand-driven programs.
+
+ This class implements a the socket-like interface needed by the
+ L{Transport} and L{Packetizer} classes. Using this class instead of a
+ regular socket makes it possible to talk with a Popen'd command that will
+ proxy traffic between the client and a server hosted in another machine.
+ """
+ def __init__(self, command_line):
+ """
+ Create a new CommandProxy instance. The instance created by this
+ class can be passed as an argument to the L{Transport} class.
+
+ @param command_line: the command that should be executed and
+ used as the proxy.
+ @type command_line: str
+ """
+ self.cmd = shlsplit(command_line)
+ self.process = Popen(self.cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
+
+ def send(self, content):
+ """
+ Write the content received from the SSH client to the standard
+ input of the forked command.
+
+ @param content: string to be sent to the forked command
+ @type content: str
+ """
+ try:
+ self.process.stdin.write(content)
+ except IOError, e:
+ # There was a problem with the child process. It probably
+ # died and we can't proceed. The best option here is to
+ # raise an exception informing the user that the informed
+ # ProxyCommand is not working.
+ raise BadProxyCommand(' '.join(self.cmd), e.strerror)
+ return len(content)
+
+ def recv(self, size):
+ """
+ Read from the standard output of the forked program.
+
+ @param size: how many chars should be read
+ @type size: int
+
+ @return: the length of the read content
+ @rtype: int
+ """
+ try:
+ return os.read(self.process.stdout.fileno(), size)
+ except IOError, e:
+ raise BadProxyCommand(' '.join(self.cmd), e.strerror)
+
+ def close(self):
+ os.kill(self.process.pid, signal.SIGTERM)
+
+ def settimeout(self, timeout):
+ # Timeouts are meaningless for this implementation, but are part of the
+ # spec, so must be present.
+ pass