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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.
from datetime import datetime
import os
from shlex import split as shlsplit
import signal
from subprocess import Popen, PIPE
from select import select
import socket
from paramiko.ssh_exception import ProxyCommandFailure
from paramiko.util import ClosingContextManager
class ProxyCommand(ClosingContextManager):
"""
Wraps a subprocess running ProxyCommand-driven programs.
This class implements a the socket-like interface needed by the
`.Transport` and `.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.
Instances of this class may be used as context managers.
"""
def __init__(self, command_line):
"""
Create a new CommandProxy instance. The instance created by this
class can be passed as an argument to the `.Transport` class.
:param str command_line:
the command that should be executed and used as the proxy.
"""
self.cmd = shlsplit(command_line)
self.process = Popen(self.cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE)
self.timeout = None
self.buffer = []
def send(self, content):
"""
Write the content received from the SSH client to the standard
input of the forked command.
:param str content: string to be sent to the forked command
"""
try:
self.process.stdin.write(content)
except IOError as 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 ProxyCommandFailure(' '.join(self.cmd), e.strerror)
return len(content)
def recv(self, size):
"""
Read from the standard output of the forked program.
:param int size: how many chars should be read
:return: the length of the read content, as an `int`
"""
try:
start = datetime.now()
while len(self.buffer) < size:
if self.timeout is not None:
elapsed = (datetime.now() - start).microseconds
timeout = self.timeout * 1000 * 1000 # to microseconds
if elapsed >= timeout:
raise socket.timeout()
r, w, x = select([self.process.stdout], [], [], 0.0)
if r and r[0] == self.process.stdout:
b = os.read(self.process.stdout.fileno(), 1)
# Store in class-level buffer for persistence across
# timeouts; this makes us act more like a real socket
# (where timeouts don't actually drop data.)
self.buffer.append(b)
result = ''.join(self.buffer)
self.buffer = []
return result
except socket.timeout:
raise # socket.timeout is a subclass of IOError
except IOError as e:
raise ProxyCommandFailure(' '.join(self.cmd), e.strerror)
def close(self):
os.kill(self.process.pid, signal.SIGTERM)
def settimeout(self, timeout):
self.timeout = timeout
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