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forward.py

#!/usr/bin/python

# Copyright (C) 2003-2005 Robey Pointer <robey@lag.net>
#
# 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.

"""
Sample script showing how to do local port forwarding over paramiko.

This script connects to the requested SSH server and sets up local port
forwarding (the openssh -L option) from a local port through a tunneled
connection to a destination reachable from the SSH server machine.
"""

import sys
import os
import socket
import select
import SocketServer
import getpass
import base64
from optparse import OptionParser

import paramiko

DEFAULT_PORT = 4000
SSH_PORT = 22
VERBOSE = True
READPASS = False


class ForwardServer (SocketServer.ThreadingTCPServer):
    daemon_threads = True
    allow_reuse_address = True
    

class Handler (SocketServer.BaseRequestHandler):

    def handle(self):
        try:
            chan = self.ssh_transport.open_channel('direct-tcpip',
                                                   (self.chain_host, self.chain_port),
                                                   self.request.getpeername())
        except Exception, e:
            verbose('Incoming request to %s:%d failed: %s' % (self.chain_host,
                                                              self.chain_port,
                                                              repr(e)))
            return

        verbose('Connected!  Tunnel open.')
        while True:
            r, w, x = select.select([self.request, chan], [], [])
            if self.request in r:
                data = self.request.recv(1024)
                if len(data) == 0:
                    break
                chan.send(data)
            if chan in r:
                data = chan.recv(1024)
                if len(data) == 0:
                    break
                self.request.send(data)
        chan.close()
        self.request.close()
        verbose('Tunnel closed.')


def forward_tunnel(local_port, remote_host, remote_port, transport):
    # this is a little convoluted, but lets me configure things for the Handler
    # object.  (SocketServer doesn't give Handlers any way to access the outer
    # server normally.)
    class SubHander (Handler):
        chain_host = remote_host
        chain_port = remote_port
        ssh_transport = transport
    ForwardServer(('', local_port), SubHander).serve_forever()

def find_default_key_file():
    filename = os.path.expanduser('~/.ssh/id_rsa')
    if os.access(filename, os.R_OK):
        return filename
    filename = os.path.expanduser('~/ssh/id_rsa')
    if os.access(filename, os.R_OK):
        return filename
    filename = os.path.expanduser('~/.ssh/id_dsa')
    if os.access(filename, os.R_OK):
        return filename
    filename = os.path.expanduser('~/ssh/id_dsa')
    if os.access(filename, os.R_OK):
        return filename
    return ''

def verbose(s):
    if VERBOSE:
        print s


#####


parser = OptionParser(usage='usage: %prog [options] <remote-addr>:<remote-port>',
                      version='%prog 1.0')
parser.add_option('-q', '--quiet', action='store_false', dest='verbose', default=VERBOSE,
                  help='squelch all informational output')
parser.add_option('-l', '--local-port', action='store', type='int', dest='port',
                  default=DEFAULT_PORT,
                  help='local port to forward (default: %d)' % DEFAULT_PORT)
parser.add_option('-r', '--host', action='store', type='string', dest='ssh_host',
                  help='SSH host to tunnel through (required)')
parser.add_option('-p', '--port', action='store', type='int', dest='ssh_port', default=SSH_PORT,
                  help='SSH port to tunnel through (default: %d)' % SSH_PORT)
parser.add_option('-u', '--user', action='store', type='string', dest='user',
                  default=getpass.getuser(),
                  help='username for SSH authentication (default: %s)' % getpass.getuser())
parser.add_option('-K', '--key', action='store', type='string', dest='keyfile',
                  default=find_default_key_file(),
                  help='private key file to use for SSH authentication')
parser.add_option('', '--no-key', action='store_false', dest='use_key', default=True,
                  help='don\'t look for or use a private key file')
parser.add_option('-P', '--password', action='store_true', dest='readpass', default=READPASS,
                  help='read password (for key or password auth) from stdin')
options, args = parser.parse_args()

VERBOSE = options.verbose
READPASS = options.readpass


if len(args) != 1:
    parser.error('Incorrect number of arguments.')
remote_host = args[0]
if ':' not in remote_host:
    parser.error('Remote port missing.')
remote_host, remote_port = remote_host.split(':', 1)
try:
    remote_port = int(remote_port)
except:
    parser.error('Remote port must be a number.')

if not options.ssh_host:
    parser.error('SSH host is required.')
if ':' in options.ssh_host:
    options.ssh_host, options.ssh_port = options.ssh_host.split(':', 1)
    try:
        options.ssh_port = int(options.ssh_port)
    except:
        parser.error('SSH port must be a number.')

try:
    host_keys = paramiko.util.load_host_keys(os.path.expanduser('~/.ssh/known_hosts'))
except IOError:
    try:
        host_keys = paramiko.util.load_host_keys(os.path.expanduser('~/ssh/known_hosts'))
    except IOError:
        print '*** Unable to open host keys file'
        host_keys = {}

if not host_keys.has_key(options.ssh_host):
    print '*** Warning: no host key for %s' % options.ssh_host
    expected_host_key_type = None
    expected_host_key = None
else:
    expected_host_key_type = host_keys[options.ssh_host].keys()[0]
    expected_host_key = host_keys[options.ssh_host][expected_host_key_type]

key = None
password = None
if options.use_key:
    try:
        key = paramiko.RSAKey.from_private_key_file(options.keyfile)
    except paramiko.PasswordRequiredException:
        if not READPASS:
            print '*** Password needed for keyfile (use -P): %s' % options.keyfile
            sys.exit(1)
        key_password = getpass.getpass('Enter password for key: ')
        try:
            key = paramiko.RSAKey.from_private_key_file(options.keyfile, key_password)
        except:
            print '*** Unable to read keyfile: %s' % options.keyfile
            sys.exit(1)
    except:
        pass

if key is None:
    # try reading a password then
    if not READPASS:
        print '*** Either a valid private key or password is required (use -K or -P).'
        sys.exit(1)
    password = getpass.getpass('Enter password: ')

verbose('Connecting to ssh host %s:%d ...' % (options.ssh_host, options.ssh_port))

transport = paramiko.Transport((options.ssh_host, options.ssh_port))
transport.connect(hostkeytype=expected_host_key_type,
                  hostkey=expected_host_key,
                  username=options.user,
                  password=password,
                  pkey=key)

verbose('Now forwarding port %d to %s:%d ...' % (options.port, remote_host, remote_port))

try:
    forward_tunnel(options.port, remote_host, remote_port, transport)
except KeyboardInterrupt:
    print 'Port forwarding stopped.'
    sys.exit(0)

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