Python port of ShadowsocksR
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#!/usr/bin/env python
# -*- coding: utf-8 -*-
# Copyright (c) 2014 clowwindy
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
import time
import os
import socket
import struct
import re
import logging
import common
import lru_cache
import eventloop
CACHE_SWEEP_INTERVAL = 30
VALID_HOSTNAME = re.compile("(?!-)[A-Z\d-]{1,63}(?<!-)$", re.IGNORECASE)
common.patch_socket()
# rfc1035
# format
# +---------------------+
# | Header |
# +---------------------+
# | Question | the question for the name server
# +---------------------+
# | Answer | RRs answering the question
# +---------------------+
# | Authority | RRs pointing toward an authority
# +---------------------+
# | Additional | RRs holding additional information
# +---------------------+
#
# header
# 1 1 1 1 1 1
# 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | ID |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# |QR| Opcode |AA|TC|RD|RA| Z | RCODE |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | QDCOUNT |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | ANCOUNT |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | NSCOUNT |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | ARCOUNT |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
QTYPE_ANY = 255
QTYPE_A = 1
QTYPE_AAAA = 28
QTYPE_CNAME = 5
QTYPE_NS = 2
QCLASS_IN = 1
def build_address(address):
address = address.strip('.')
labels = address.split('.')
results = []
for label in labels:
l = len(label)
if l > 63:
return None
results.append(chr(l))
results.append(label)
results.append('\0')
return ''.join(results)
def build_request(address, qtype, request_id):
header = struct.pack('!HBBHHHH', request_id, 1, 0, 1, 0, 0, 0)
addr = build_address(address)
qtype_qclass = struct.pack('!HH', qtype, QCLASS_IN)
return header + addr + qtype_qclass
def parse_ip(addrtype, data, length, offset):
if addrtype == QTYPE_A:
return socket.inet_ntop(socket.AF_INET, data[offset:offset + length])
elif addrtype == QTYPE_AAAA:
return socket.inet_ntop(socket.AF_INET6, data[offset:offset + length])
elif addrtype in [QTYPE_CNAME, QTYPE_NS]:
return parse_name(data, offset)[1]
else:
return data[offset:offset + length]
def parse_name(data, offset):
p = offset
labels = []
l = ord(data[p])
while l > 0:
if (l & (128 + 64)) == (128 + 64):
# pointer
pointer = struct.unpack('!H', data[p:p + 2])[0]
pointer &= 0x3FFF
r = parse_name(data, pointer)
labels.append(r[1])
p += 2
# pointer is the end
return p - offset, '.'.join(labels)
else:
labels.append(data[p + 1:p + 1 + l])
p += 1 + l
l = ord(data[p])
return p - offset + 1, '.'.join(labels)
# rfc1035
# record
# 1 1 1 1 1 1
# 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | |
# / /
# / NAME /
# | |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | TYPE |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | CLASS |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | TTL |
# | |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
# | RDLENGTH |
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
# / RDATA /
# / /
# +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
def parse_record(data, offset, question=False):
nlen, name = parse_name(data, offset)
if not question:
record_type, record_class, record_ttl, record_rdlength = struct.unpack(
'!HHiH', data[offset + nlen:offset + nlen + 10]
)
ip = parse_ip(record_type, data, record_rdlength, offset + nlen + 10)
return nlen + 10 + record_rdlength, \
(name, ip, record_type, record_class, record_ttl)
else:
record_type, record_class = struct.unpack(
'!HH', data[offset + nlen:offset + nlen + 4]
)
return nlen + 4, (name, None, record_type, record_class, None, None)
def parse_header(data):
if len(data) >= 12:
header = struct.unpack('!HBBHHHH', data[:12])
res_id = header[0]
res_qr = header[1] & 128
res_tc = header[1] & 2
res_ra = header[2] & 128
res_rcode = header[2] & 15
# assert res_tc == 0
# assert res_rcode in [0, 3]
res_qdcount = header[3]
res_ancount = header[4]
res_nscount = header[5]
res_arcount = header[6]
return (res_id, res_qr, res_tc, res_ra, res_rcode, res_qdcount,
res_ancount, res_nscount, res_arcount)
return None
def parse_response(data):
try:
if len(data) >= 12:
header = parse_header(data)
if not header:
return None
res_id, res_qr, res_tc, res_ra, res_rcode, res_qdcount, \
res_ancount, res_nscount, res_arcount = header
qds = []
ans = []
offset = 12
for i in xrange(0, res_qdcount):
l, r = parse_record(data, offset, True)
offset += l
if r:
qds.append(r)
for i in xrange(0, res_ancount):
l, r = parse_record(data, offset)
offset += l
if r:
ans.append(r)
for i in xrange(0, res_nscount):
l, r = parse_record(data, offset)
offset += l
for i in xrange(0, res_arcount):
l, r = parse_record(data, offset)
offset += l
response = DNSResponse()
if qds:
response.hostname = qds[0][0]
for an in ans:
response.answers.append((an[1], an[2], an[3]))
return response
except Exception as e:
import traceback
traceback.print_exc()
logging.error(e)
return None
def is_ip(address):
for family in (socket.AF_INET, socket.AF_INET6):
try:
socket.inet_pton(family, address)
return family
except (TypeError, ValueError, OSError, IOError):
pass
return False
def is_valid_hostname(hostname):
if len(hostname) > 255:
return False
if hostname[-1] == ".":
hostname = hostname[:-1]
return all(VALID_HOSTNAME.match(x) for x in hostname.split("."))
class DNSResponse(object):
def __init__(self):
self.hostname = None
self.answers = [] # each: (addr, type, class)
def __str__(self):
return '%s: %s' % (self.hostname, str(self.answers))
STATUS_IPV4 = 0
STATUS_IPV6 = 1
class DNSResolver(object):
def __init__(self):
self._loop = None
self._request_id = 1
self._hosts = {}
self._hostname_status = {}
self._hostname_to_cb = {}
self._cb_to_hostname = {}
self._cache = lru_cache.LRUCache(timeout=300)
self._last_time = time.time()
self._sock = None
self._servers = None
self._parse_resolv()
self._parse_hosts()
# TODO monitor hosts change and reload hosts
# TODO parse /etc/gai.conf and follow its rules
def _parse_resolv(self):
self._servers = []
try:
with open('/etc/resolv.conf', 'rb') as f:
content = f.readlines()
for line in content:
line = line.strip()
if line:
if line.startswith('nameserver'):
parts = line.split()
if len(parts) >= 2:
server = parts[1]
if is_ip(server) == socket.AF_INET:
self._servers.append(server)
except IOError:
pass
if not self._servers:
self._servers = ['8.8.4.4', '8.8.8.8']
def _parse_hosts(self):
etc_path = '/etc/hosts'
if os.environ.__contains__('WINDIR'):
etc_path = os.environ['WINDIR'] + '/system32/drivers/etc/hosts'
try:
with open(etc_path, 'rb') as f:
for line in f.readlines():
line = line.strip()
parts = line.split()
if len(parts) >= 2:
ip = parts[0]
if is_ip(ip):
for i in xrange(1, len(parts)):
hostname = parts[i]
if hostname:
self._hosts[hostname] = ip
except IOError:
self._hosts['localhost'] = '127.0.0.1'
def add_to_loop(self, loop):
if self._loop:
raise Exception('already add to loop')
self._loop = loop
# TODO when dns server is IPv6
self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM,
socket.SOL_UDP)
self._sock.setblocking(False)
loop.add(self._sock, eventloop.POLL_IN)
loop.add_handler(self.handle_events)
def _call_callback(self, hostname, ip, error=None):
callbacks = self._hostname_to_cb.get(hostname, [])
for callback in callbacks:
if self._cb_to_hostname.__contains__(callback):
del self._cb_to_hostname[callback]
if ip or error:
callback((hostname, ip), error)
else:
callback((hostname, None),
Exception('unknown hostname %s' % hostname))
if self._hostname_to_cb.__contains__(hostname):
del self._hostname_to_cb[hostname]
if self._hostname_status.__contains__(hostname):
del self._hostname_status[hostname]
def _handle_data(self, data):
response = parse_response(data)
if response and response.hostname:
hostname = response.hostname
ip = None
for answer in response.answers:
if answer[1] in (QTYPE_A, QTYPE_AAAA) and \
answer[2] == QCLASS_IN:
ip = answer[0]
break
if not ip and self._hostname_status.get(hostname, STATUS_IPV6) \
== STATUS_IPV4:
self._hostname_status[hostname] = STATUS_IPV6
self._send_req(hostname, QTYPE_AAAA)
else:
if ip:
self._cache[hostname] = ip
self._call_callback(hostname, ip)
def handle_events(self, events):
for sock, fd, event in events:
if sock != self._sock:
continue
if event & eventloop.POLL_ERR:
logging.error('dns socket err')
self._loop.remove(self._sock)
self._sock.close()
# TODO when dns server is IPv6
self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM,
socket.SOL_UDP)
self._sock.setblocking(False)
self._loop.add(self._sock, eventloop.POLL_IN)
else:
data, addr = sock.recvfrom(1024)
if addr[0] not in self._servers:
logging.warn('received a packet other than our dns')
break
self._handle_data(data)
break
now = time.time()
if now - self._last_time > CACHE_SWEEP_INTERVAL:
self._cache.sweep()
self._last_time = now
def remove_callback(self, callback):
hostname = self._cb_to_hostname.get(callback)
if hostname:
del self._cb_to_hostname[callback]
arr = self._hostname_to_cb.get(hostname, None)
if arr:
arr.remove(callback)
if not arr:
del self._hostname_to_cb[hostname]
if self._hostname_status.__contains__(hostname):
del self._hostname_status[hostname]
def _send_req(self, hostname, qtype):
self._request_id += 1
if self._request_id > 32768:
self._request_id = 1
req = build_request(hostname, qtype, self._request_id)
for server in self._servers:
logging.debug('resolving %s with type %d using server %s',
hostname, qtype, server)
self._sock.sendto(req, (server, 53))
def resolve(self, hostname, callback):
if not hostname:
callback(None, Exception('empty hostname'))
elif is_ip(hostname):
callback((hostname, hostname), None)
elif self._hosts.__contains__(hostname):
logging.debug('hit hosts: %s', hostname)
ip = self._hosts[hostname]
callback((hostname, ip), None)
elif self._cache.__contains__(hostname):
logging.debug('hit cache: %s', hostname)
ip = self._cache[hostname]
callback((hostname, ip), None)
else:
if not is_valid_hostname(hostname):
callback(None, Exception('invalid hostname: %s' % hostname))
return
arr = self._hostname_to_cb.get(hostname, None)
if not arr:
self._hostname_status[hostname] = STATUS_IPV4
self._send_req(hostname, QTYPE_A)
self._hostname_to_cb[hostname] = [callback]
self._cb_to_hostname[callback] = hostname
else:
arr.append(callback)
# TODO send again only if waited too long
self._send_req(hostname, QTYPE_A)
def close(self):
if self._sock:
self._sock.close()
self._sock = None
def test():
logging.getLogger('').handlers = []
logging.basicConfig(level=logging.DEBUG,
format='%(asctime)s %(levelname)-8s %(message)s',
datefmt='%Y-%m-%d %H:%M:%S', filemode='a+')
def _callback(address, error):
print error, address
loop = eventloop.EventLoop()
resolver = DNSResolver()
resolver.add_to_loop(loop)
for hostname in ['www.google.com',
'8.8.8.8',
'localhost',
'activate.adobe.com',
'www.twitter.com',
'ipv6.google.com',
'ipv6.l.google.com',
'www.gmail.com',
'r4---sn-3qqp-ioql.googlevideo.com',
'www.baidu.com',
'www.a.shifen.com',
'm.baidu.jp',
'www.youku.com',
'www.twitter.com',
'ipv6.google.com']:
resolver.resolve(hostname, _callback)
loop.run()
if __name__ == '__main__':
test()