sshuttle/sshuttle/ssh.py

import sys
import os
import re
import socket
import zlib
import importlib
import importlib.util
import subprocess as ssubprocess
import shlex
from shlex import quote
import ipaddress
from urllib.parse import urlparse

import sshuttle.helpers as helpers
from sshuttle.helpers import debug2, which, get_path, Fatal


def get_module_source(name):
    spec = importlib.util.find_spec(name)
    with open(spec.origin, "rt") as f:
        return f.read().encode("utf-8")


def empackage(z, name, data=None):
    if not data:
        data = get_module_source(name)
    content = z.compress(data)
    content += z.flush(zlib.Z_SYNC_FLUSH)

    return b'%s\n%d\n%s' % (name.encode("ASCII"), len(content), content)


def parse_hostport(rhostport):
    """
    parses the given rhostport variable, looking like this:

            [username[:password]@]host[:port]

    if only host is given, can be a hostname, IPv4/v6 address or a ssh alias
    from ~/.ssh/config

    and returns a tuple (username, password, port, host)
    """
    # leave use of default port to ssh command to prevent overwriting
    # ports configured in ~/.ssh/config when no port is given
    if rhostport is None or len(rhostport) == 0:
        return None, None, None, None
    port = None
    username = None
    password = None
    host = rhostport

    if "@" in host:
        # split username (and possible password) from the host[:port]
        username, host = host.rsplit("@", 1)
        # Fix #410 bad username error detect
        if ":" in username:
            # this will even allow for the username to be empty
            username, password = username.split(":")

    if ":" in host:
        # IPv6 address and/or got a port specified

        # If it is an IPv6 adress with port specification,
        # then it will look like: [::1]:22

        try:
            # try to parse host as an IP adress,
            # if that works it is an IPv6 address
            host = str(ipaddress.ip_address(host))
        except ValueError:
            # if that fails parse as URL to get the port
            parsed = urlparse('//{}'.format(host))
            try:
                host = str(ipaddress.ip_address(parsed.hostname))
            except ValueError:
                # else if both fails, we have a hostname with port
                host = parsed.hostname
            port = parsed.port

    if password is None or len(password) == 0:
        password = None

    return username, password, port, host


def connect(ssh_cmd, rhostport, python, stderr, options):
    username, password, port, host = parse_hostport(rhostport)
    if username:
        rhost = "{}@{}".format(username, host)
    else:
        rhost = host

    z = zlib.compressobj(1)
    content = get_module_source('sshuttle.assembler')
    optdata = ''.join("%s=%r\n" % (k, v) for (k, v) in list(options.items()))
    optdata = optdata.encode("UTF8")
    content2 = (empackage(z, 'sshuttle') +
                empackage(z, 'sshuttle.cmdline_options', optdata) +
                empackage(z, 'sshuttle.helpers') +
                empackage(z, 'sshuttle.ssnet') +
                empackage(z, 'sshuttle.hostwatch') +
                empackage(z, 'sshuttle.server') +
                b"\n")

    pyscript = r"""
                import sys, os;
                verbosity=%d;
                sys.stdin = os.fdopen(0, "rb");
                exec(compile(sys.stdin.read(%d), "assembler.py", "exec"))
                """ % (helpers.verbose or 0, len(content))
    pyscript = re.sub(r'\s+', ' ', pyscript.strip())

    if not rhost:
        # ignore the --python argument when running locally; we already know
        # which python version works.
        argv = [sys.executable, '-c', pyscript]
    else:
        if ssh_cmd:
            sshl = shlex.split(ssh_cmd)
        else:
            sshl = ['ssh']
        if port is not None:
            portl = ["-p", str(port)]
        else:
            portl = []
        if python:
            pycmd = "'%s' -c '%s'" % (python, pyscript)
        else:
            pycmd = ("P=python3; $P -V 2>%s || P=python; "
                     "exec \"$P\" -c %s") % (os.devnull, quote(pyscript))
            pycmd = ("/bin/sh -c {}".format(quote(pycmd)))

        if password is not None:
            os.environ['SSHPASS'] = str(password)
            argv = (["sshpass", "-e"] + sshl +
                    portl +
                    [rhost, '--', pycmd])

        else:
            argv = (sshl +
                    portl +
                    [rhost, '--', pycmd])

    # Our which() function searches for programs in get_path()
    # directories (which include PATH). This step isn't strictly
    # necessary if ssh is already in the user's PATH, but it makes the
    # error message friendlier if the user incorrectly passes in a
    # custom ssh command that we cannot find.
    abs_path = which(argv[0])
    if abs_path is None:
        raise Fatal("Failed to find '%s' in path %s" % (argv[0], get_path()))
    argv[0] = abs_path

    (s1, s2) = socket.socketpair()

    def setup():
        # runs in the child process
        s2.close()
    s1a, s1b = os.dup(s1.fileno()), os.dup(s1.fileno())
    s1.close()

    debug2('executing: %r' % argv)
    p = ssubprocess.Popen(argv, stdin=s1a, stdout=s1b, preexec_fn=setup,
                          close_fds=True, stderr=stderr)
    os.close(s1a)
    os.close(s1b)
    s2.sendall(content)
    s2.sendall(content2)
    return p, s2