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"""Basic ssh tunnel utilities, and convenience functions for tunneling
zeromq connections.
"""
# Copyright (C) 2010-2011 IPython Development Team
# Copyright (C) 2011- PyZMQ Developers
#
# Redistributed from IPython under the terms of the BSD License.
import atexit
import os
import re
import signal
import socket
import sys
import warnings
from getpass import getpass, getuser
from multiprocessing import Process
try:
with warnings.catch_warnings():
warnings.simplefilter('ignore', DeprecationWarning)
import paramiko
SSHException = paramiko.ssh_exception.SSHException
except ImportError:
paramiko = None # type: ignore
class SSHException(Exception): # type: ignore
pass
else:
from .forward import forward_tunnel
try:
import pexpect
except ImportError:
pexpect = None
def select_random_ports(n):
"""Select and return n random ports that are available."""
ports = []
sockets = []
for i in range(n):
sock = socket.socket()
sock.bind(('', 0))
ports.append(sock.getsockname()[1])
sockets.append(sock)
for sock in sockets:
sock.close()
return ports
# -----------------------------------------------------------------------------
# Check for passwordless login
# -----------------------------------------------------------------------------
_password_pat = re.compile(rb'pass(word|phrase):', re.IGNORECASE)
def try_passwordless_ssh(server, keyfile, paramiko=None):
"""Attempt to make an ssh connection without a password.
This is mainly used for requiring password input only once
when many tunnels may be connected to the same server.
If paramiko is None, the default for the platform is chosen.
"""
if paramiko is None:
paramiko = sys.platform == 'win32'
if not paramiko:
f = _try_passwordless_openssh
else:
f = _try_passwordless_paramiko
return f(server, keyfile)
def _try_passwordless_openssh(server, keyfile):
"""Try passwordless login with shell ssh command."""
if pexpect is None:
raise ImportError("pexpect unavailable, use paramiko")
cmd = 'ssh -f ' + server
if keyfile:
cmd += ' -i ' + keyfile
cmd += ' exit'
# pop SSH_ASKPASS from env
env = os.environ.copy()
env.pop('SSH_ASKPASS', None)
ssh_newkey = 'Are you sure you want to continue connecting'
p = pexpect.spawn(cmd, env=env)
while True:
try:
i = p.expect([ssh_newkey, _password_pat], timeout=0.1)
if i == 0:
raise SSHException(
'The authenticity of the host can\'t be established.'
)
except pexpect.TIMEOUT:
continue
except pexpect.EOF:
return True
else:
return False
def _try_passwordless_paramiko(server, keyfile):
"""Try passwordless login with paramiko."""
if paramiko is None:
msg = "Paramiko unavailable, "
if sys.platform == 'win32':
msg += "Paramiko is required for ssh tunneled connections on Windows."
else:
msg += "use OpenSSH."
raise ImportError(msg)
username, server, port = _split_server(server)
client = paramiko.SSHClient()
known_hosts = os.path.expanduser("~/.ssh/known_hosts")
try:
client.load_host_keys(known_hosts)
except FileNotFoundError:
pass
policy_name = os.environ.get("PYZMQ_PARAMIKO_HOST_KEY_POLICY", None)
if policy_name:
policy = getattr(paramiko, f"{policy_name}Policy")
client.set_missing_host_key_policy(policy())
try:
client.connect(
server, port, username=username, key_filename=keyfile, look_for_keys=True
)
except paramiko.AuthenticationException:
return False
else:
client.close()
return True
def tunnel_connection(
socket, addr, server, keyfile=None, password=None, paramiko=None, timeout=60
):
"""Connect a socket to an address via an ssh tunnel.
This is a wrapper for socket.connect(addr), when addr is not accessible
from the local machine. It simply creates an ssh tunnel using the remaining args,
and calls socket.connect('tcp://localhost:lport') where lport is the randomly
selected local port of the tunnel.
"""
new_url, tunnel = open_tunnel(
addr,
server,
keyfile=keyfile,
password=password,
paramiko=paramiko,
timeout=timeout,
)
socket.connect(new_url)
return tunnel
def open_tunnel(addr, server, keyfile=None, password=None, paramiko=None, timeout=60):
"""Open a tunneled connection from a 0MQ url.
For use inside tunnel_connection.
Returns
-------
(url, tunnel) : (str, object)
The 0MQ url that has been forwarded, and the tunnel object
"""
lport = select_random_ports(1)[0]
transport, addr = addr.split('://')
ip, rport = addr.split(':')
rport = int(rport)
if paramiko is None:
paramiko = sys.platform == 'win32'
if paramiko:
tunnelf = paramiko_tunnel
else:
tunnelf = openssh_tunnel
tunnel = tunnelf(
lport,
rport,
server,
remoteip=ip,
keyfile=keyfile,
password=password,
timeout=timeout,
)
return 'tcp://127.0.0.1:%i' % lport, tunnel
def openssh_tunnel(
lport, rport, server, remoteip='127.0.0.1', keyfile=None, password=None, timeout=60
):
"""Create an ssh tunnel using command-line ssh that connects port lport
on this machine to localhost:rport on server. The tunnel
will automatically close when not in use, remaining open
for a minimum of timeout seconds for an initial connection.
This creates a tunnel redirecting `localhost:lport` to `remoteip:rport`,
as seen from `server`.
keyfile and password may be specified, but ssh config is checked for defaults.
Parameters
----------
lport : int
local port for connecting to the tunnel from this machine.
rport : int
port on the remote machine to connect to.
server : str
The ssh server to connect to. The full ssh server string will be parsed.
user@server:port
remoteip : str [Default: 127.0.0.1]
The remote ip, specifying the destination of the tunnel.
Default is localhost, which means that the tunnel would redirect
localhost:lport on this machine to localhost:rport on the *server*.
keyfile : str; path to public key file
This specifies a key to be used in ssh login, default None.
Regular default ssh keys will be used without specifying this argument.
password : str;
Your ssh password to the ssh server. Note that if this is left None,
you will be prompted for it if passwordless key based login is unavailable.
timeout : int [default: 60]
The time (in seconds) after which no activity will result in the tunnel
closing. This prevents orphaned tunnels from running forever.
"""
if pexpect is None:
raise ImportError("pexpect unavailable, use paramiko_tunnel")
ssh = "ssh "
if keyfile:
ssh += "-i " + keyfile
if ':' in server:
server, port = server.split(':')
ssh += " -p %s" % port
cmd = f"{ssh} -O check {server}"
(output, exitstatus) = pexpect.run(cmd, withexitstatus=True)
if not exitstatus:
pid = int(output[output.find(b"(pid=") + 5 : output.find(b")")])
cmd = "%s -O forward -L 127.0.0.1:%i:%s:%i %s" % (
ssh,
lport,
remoteip,
rport,
server,
)
(output, exitstatus) = pexpect.run(cmd, withexitstatus=True)
if not exitstatus:
atexit.register(_stop_tunnel, cmd.replace("-O forward", "-O cancel", 1))
return pid
cmd = "%s -f -S none -L 127.0.0.1:%i:%s:%i %s sleep %i" % (
ssh,
lport,
remoteip,
rport,
server,
timeout,
)
# pop SSH_ASKPASS from env
env = os.environ.copy()
env.pop('SSH_ASKPASS', None)
ssh_newkey = 'Are you sure you want to continue connecting'
tunnel = pexpect.spawn(cmd, env=env)
failed = False
while True:
try:
i = tunnel.expect([ssh_newkey, _password_pat], timeout=0.1)
if i == 0:
raise SSHException(
'The authenticity of the host can\'t be established.'
)
except pexpect.TIMEOUT:
continue
except pexpect.EOF:
if tunnel.exitstatus:
print(tunnel.exitstatus)
print(tunnel.before)
print(tunnel.after)
raise RuntimeError("tunnel '%s' failed to start" % (cmd))
else:
return tunnel.pid
else:
if failed:
print("Password rejected, try again")
password = None
if password is None:
password = getpass("%s's password: " % (server))
tunnel.sendline(password)
failed = True
def _stop_tunnel(cmd):
pexpect.run(cmd)
def _split_server(server):
if '@' in server:
username, server = server.split('@', 1)
else:
username = getuser()
if ':' in server:
server, port = server.split(':')
port = int(port)
else:
port = 22
return username, server, port
def paramiko_tunnel(
lport, rport, server, remoteip='127.0.0.1', keyfile=None, password=None, timeout=60
):
"""launch a tunner with paramiko in a subprocess. This should only be used
when shell ssh is unavailable (e.g. Windows).
This creates a tunnel redirecting `localhost:lport` to `remoteip:rport`,
as seen from `server`.
If you are familiar with ssh tunnels, this creates the tunnel:
ssh server -L localhost:lport:remoteip:rport
keyfile and password may be specified, but ssh config is checked for defaults.
Parameters
----------
lport : int
local port for connecting to the tunnel from this machine.
rport : int
port on the remote machine to connect to.
server : str
The ssh server to connect to. The full ssh server string will be parsed.
user@server:port
remoteip : str [Default: 127.0.0.1]
The remote ip, specifying the destination of the tunnel.
Default is localhost, which means that the tunnel would redirect
localhost:lport on this machine to localhost:rport on the *server*.
keyfile : str; path to public key file
This specifies a key to be used in ssh login, default None.
Regular default ssh keys will be used without specifying this argument.
password : str;
Your ssh password to the ssh server. Note that if this is left None,
you will be prompted for it if passwordless key based login is unavailable.
timeout : int [default: 60]
The time (in seconds) after which no activity will result in the tunnel
closing. This prevents orphaned tunnels from running forever.
"""
if paramiko is None:
raise ImportError("Paramiko not available")
if password is None:
if not _try_passwordless_paramiko(server, keyfile):
password = getpass("%s's password: " % (server))
p = Process(
target=_paramiko_tunnel,
args=(lport, rport, server, remoteip),
kwargs=dict(keyfile=keyfile, password=password),
)
p.daemon = True
p.start()
return p
def _paramiko_tunnel(lport, rport, server, remoteip, keyfile=None, password=None):
"""Function for actually starting a paramiko tunnel, to be passed
to multiprocessing.Process(target=this), and not called directly.
"""
username, server, port = _split_server(server)
client = paramiko.SSHClient()
client.load_system_host_keys()
client.set_missing_host_key_policy(paramiko.WarningPolicy())
try:
client.connect(
server,
port,
username=username,
key_filename=keyfile,
look_for_keys=True,
password=password,
)
# except paramiko.AuthenticationException:
# if password is None:
# password = getpass("%s@%s's password: "%(username, server))
# client.connect(server, port, username=username, password=password)
# else:
# raise
except Exception as e:
print('*** Failed to connect to %s:%d: %r' % (server, port, e))
sys.exit(1)
# Don't let SIGINT kill the tunnel subprocess
signal.signal(signal.SIGINT, signal.SIG_IGN)
try:
forward_tunnel(lport, remoteip, rport, client.get_transport())
except KeyboardInterrupt:
print('SIGINT: Port forwarding stopped cleanly')
sys.exit(0)
except Exception as e:
print("Port forwarding stopped uncleanly: %s" % e)
sys.exit(255)
if sys.platform == 'win32':
ssh_tunnel = paramiko_tunnel
else:
ssh_tunnel = openssh_tunnel
__all__ = [
'tunnel_connection',
'ssh_tunnel',
'openssh_tunnel',
'paramiko_tunnel',
'try_passwordless_ssh',
]