sshuttle/ssh.py

import os, re, subprocess

def connect(rhost, subcmd):
    assert(not re.search(r'[^\w-]', subcmd))
    main_exe = sys.argv[0]
    nicedir = os.path.split(os.path.abspath(main_exe))[0]
    nicedir = re.sub(r':', "_", nicedir)
    if rhost == '-':
        rhost = None
    if not rhost:
        argv = ['sshuttle', subcmd]
    else:
        # WARNING: shell quoting security holes are possible here, so we
        # have to be super careful.  We have to use 'sh -c' because
        # csh-derived shells can't handle PATH= notation.  We can't
        # set PATH in advance, because ssh probably replaces it.  We
        # can't exec *safely* using argv, because *both* ssh and 'sh -c'
        # allow shellquoting.  So we end up having to double-shellquote
        # stuff here.
        escapedir = re.sub(r'([^\w/])', r'\\\\\\\1', nicedir)
        cmd = r"""
                   sh -c PATH=%s:'$PATH sshuttle %s'
               """ % (escapedir, subcmd)
        argv = ['ssh', rhost, '--', cmd.strip()]
    def setup():
        # runs in the child process
        if not rhost:
            os.environ['PATH'] = ':'.join([nicedir,
                                           os.environ.get('PATH', '')])
        os.setsid()
    return subprocess.Popen(argv, stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                            preexec_fn=setup)