sshuttle/sshuttle/hostwatch.py

import time
import socket
import re
import select
import errno
import os
import sys
import platform

import subprocess as ssubprocess
import sshuttle.helpers as helpers
from sshuttle.helpers import log, debug1, debug2, debug3

POLL_TIME = 60 * 15
NETSTAT_POLL_TIME = 30
CACHEFILE = os.path.expanduser('~/.sshuttle.hosts')


_nmb_ok = True
_smb_ok = True
hostnames = {}
queue = {}
try:
    null = open(os.devnull, 'wb')
except IOError:
    _, e = sys.exc_info()[:2]
    log('warning: %s\n' % e)
    null = os.popen("sh -c 'while read x; do :; done'", 'wb', 4096)


def _is_ip(s):
    return re.match(r'\d+\.\d+\.\d+\.\d+$', s)


def write_host_cache():
    tmpname = '%s.%d.tmp' % (CACHEFILE, os.getpid())
    try:
        f = open(tmpname, 'wb')
        for name, ip in sorted(hostnames.items()):
            f.write(('%s,%s\n' % (name, ip)).encode("ASCII"))
        f.close()
        os.chmod(tmpname, 384)  # 600 in octal, 'rw-------'
        os.rename(tmpname, CACHEFILE)
    finally:
        try:
            os.unlink(tmpname)
        except BaseException:
            pass


def read_host_cache():
    try:
        f = open(CACHEFILE)
    except IOError:
        _, e = sys.exc_info()[:2]
        if e.errno == errno.ENOENT:
            return
        else:
            raise
    for line in f:
        words = line.strip().split(',')
        if len(words) == 2:
            (name, ip) = words
            name = re.sub(r'[^-\w\.]', '-', name).strip()
            ip = re.sub(r'[^0-9.]', '', ip).strip()
            if name and ip:
                found_host(name, ip)


def found_host(name, ip):
    hostname = re.sub(r'\..*', '', name)
    hostname = re.sub(r'[^-\w\.]', '_', hostname)
    if (ip.startswith('127.') or ip.startswith('255.') or
            hostname == 'localhost'):
        return

    if hostname != name:
        found_host(hostname, ip)

    oldip = hostnames.get(name)
    if oldip != ip:
        hostnames[name] = ip
        debug1('Found: %s: %s\n' % (name, ip))
        sys.stdout.write('%s,%s\n' % (name, ip))
        write_host_cache()


def _check_etc_hosts():
    debug2(' > hosts\n')
    for line in open('/etc/hosts'):
        line = re.sub(r'#.*', '', line)
        words = line.strip().split()
        if not words:
            continue
        ip = words[0]
        names = words[1:]
        if _is_ip(ip):
            debug3('<    %s %r\n' % (ip, names))
            for n in names:
                check_host(n)
                found_host(n, ip)


def _check_revdns(ip):
    debug2(' > rev: %s\n' % ip)
    try:
        r = socket.gethostbyaddr(ip)
        debug3('<    %s\n' % r[0])
        check_host(r[0])
        found_host(r[0], ip)
    except socket.herror:
        pass


def _check_dns(hostname):
    debug2(' > dns: %s\n' % hostname)
    try:
        ip = socket.gethostbyname(hostname)
        debug3('<    %s\n' % ip)
        check_host(ip)
        found_host(hostname, ip)
    except socket.gaierror:
        pass


def _check_netstat():
    debug2(' > netstat\n')
    argv = ['netstat', '-n']
    try:
        p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE, stderr=null)
        content = p.stdout.read().decode("ASCII")
        p.wait()
    except OSError:
        _, e = sys.exc_info()[:2]
        log('%r failed: %r\n' % (argv, e))
        return

    for ip in re.findall(r'\d+\.\d+\.\d+\.\d+', content):
        debug3('<    %s\n' % ip)
        check_host(ip)


def _check_smb(hostname):
    return
    global _smb_ok
    if not _smb_ok:
        return
    argv = ['smbclient', '-U', '%', '-L', hostname]
    debug2(' > smb: %s\n' % hostname)
    try:
        p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE, stderr=null)
        lines = p.stdout.readlines()
        p.wait()
    except OSError:
        _, e = sys.exc_info()[:2]
        log('%r failed: %r\n' % (argv, e))
        _smb_ok = False
        return

    lines.reverse()

    # junk at top
    while lines:
        line = lines.pop().strip()
        if re.match(r'Server\s+', line):
            break

    # server list section:
    #    Server   Comment
    #    ------   -------
    while lines:
        line = lines.pop().strip()
        if not line or re.match(r'-+\s+-+', line):
            continue
        if re.match(r'Workgroup\s+Master', line):
            break
        words = line.split()
        hostname = words[0].lower()
        debug3('<    %s\n' % hostname)
        check_host(hostname)

    # workgroup list section:
    #   Workgroup  Master
    #   ---------  ------
    while lines:
        line = lines.pop().strip()
        if re.match(r'-+\s+', line):
            continue
        if not line:
            break
        words = line.split()
        (workgroup, hostname) = (words[0].lower(), words[1].lower())
        debug3('<    group(%s) -> %s\n' % (workgroup, hostname))
        check_host(hostname)
        check_workgroup(workgroup)

    if lines:
        assert(0)


def _check_nmb(hostname, is_workgroup, is_master):
    return
    global _nmb_ok
    if not _nmb_ok:
        return
    argv = ['nmblookup'] + ['-M'] * is_master + ['--', hostname]
    debug2(' > n%d%d: %s\n' % (is_workgroup, is_master, hostname))
    try:
        p = ssubprocess.Popen(argv, stdout=ssubprocess.PIPE, stderr=null)
        lines = p.stdout.readlines()
        rv = p.wait()
    except OSError:
        _, e = sys.exc_info()[:2]
        log('%r failed: %r\n' % (argv, e))
        _nmb_ok = False
        return
    if rv:
        log('%r returned %d\n' % (argv, rv))
        return
    for line in lines:
        m = re.match(r'(\d+\.\d+\.\d+\.\d+) (\w+)<\w\w>\n', line)
        if m:
            g = m.groups()
            (ip, name) = (g[0], g[1].lower())
            debug3('<    %s -> %s\n' % (name, ip))
            if is_workgroup:
                _enqueue(_check_smb, ip)
            else:
                found_host(name, ip)
                check_host(name)


def check_host(hostname):
    if _is_ip(hostname):
        _enqueue(_check_revdns, hostname)
    else:
        _enqueue(_check_dns, hostname)
    _enqueue(_check_smb, hostname)
    _enqueue(_check_nmb, hostname, False, False)


def check_workgroup(hostname):
    _enqueue(_check_nmb, hostname, True, False)
    _enqueue(_check_nmb, hostname, True, True)


def _enqueue(op, *args):
    t = (op, args)
    if queue.get(t) is None:
        queue[t] = 0


def _stdin_still_ok(timeout):
    r, _, _ = select.select([sys.stdin.fileno()], [], [], timeout)
    if r:
        b = os.read(sys.stdin.fileno(), 4096)
        if not b:
            return False
    return True


def hw_main(seed_hosts, auto_hosts):
    if helpers.verbose >= 2:
        helpers.logprefix = 'HH: '
    else:
        helpers.logprefix = 'hostwatch: '

    debug1('Starting hostwatch with Python version %s\n'
           % platform.python_version())

    for h in seed_hosts:
        check_host(h)

    if auto_hosts:
        read_host_cache()
        _enqueue(_check_etc_hosts)
        _enqueue(_check_netstat)
        check_host('localhost')
        check_host(socket.gethostname())
        check_workgroup('workgroup')
        check_workgroup('-')

    while 1:
        now = time.time()
        for t, last_polled in list(queue.items()):
            (op, args) = t
            if not _stdin_still_ok(0):
                break
            maxtime = POLL_TIME
            if op == _check_netstat:
                maxtime = NETSTAT_POLL_TIME
            if now - last_polled > maxtime:
                queue[t] = time.time()
                op(*args)
            try:
                sys.stdout.flush()
            except IOError:
                break

        # FIXME: use a smarter timeout based on oldest last_polled
        if not _stdin_still_ok(1):
            break