"""
$Id$
This file is part of the py3dns project.
Homepage: https://launchpad.net/py3dns
This code is covered by the standard Python License. See LICENSE for details.
Changes for Python3 port © 2011-14 Scott Kitterman <scott@kitterman.com>
Base functionality. Request and Response classes, that sort of thing.
"""
import socket, string, types, time, select, warnings
import errno
from . import Type,Class,Opcode
import asyncore
#
# This random generator is used for transaction ids and port selection. This
# is important to prevent spurious results from lost packets, and malicious
# cache poisoning. This doesn't matter if you are behind a caching nameserver
# or your app is a primary DNS server only. To install your own generator,
# replace DNS.Base.random. SystemRandom uses /dev/urandom or similar source.
#
try:
from random import SystemRandom
random = SystemRandom()
except:
import random
class DNSError(Exception): pass
class ArgumentError(DNSError): pass
class SocketError(DNSError): pass
class TimeoutError(DNSError): pass
class ServerError(DNSError):
def __init__(self, message, rcode):
DNSError.__init__(self, message, rcode)
self.message = message
self.rcode = rcode
class IncompleteReplyError(DNSError): pass
# Lib uses some of the above exception classes, so import after defining.
from . import Lib
defaults= { 'protocol':'udp', 'port':53, 'opcode':Opcode.QUERY,
'qtype':Type.A, 'rd':1, 'timing':1, 'timeout': 30, 'server_rotate': 0,
'server': [] }
def ParseResolvConf(resolv_path="/etc/resolv.conf"):
"parses the /etc/resolv.conf file and sets defaults for name servers"
try:
with open(resolv_path, 'r') as stream:
return ParseResolvConfFromIterable(stream)
except FileNotFoundError as e:
warnings.warn(str(e))
return
def ParseResolvConfFromIterable(lines):
"parses a resolv.conf formatted stream and sets defaults for name servers"
global defaults
for line in lines:
line = line.strip()
if not line or line[0]==';' or line[0]=='#':
continue
fields=line.split()
if len(fields) < 2:
continue
if fields[0]=='domain' and len(fields) > 1:
defaults['domain']=fields[1]
if fields[0]=='search':
pass
if fields[0]=='options':
pass
if fields[0]=='sortlist':
pass
if fields[0]=='nameserver':
defaults['server'].append(fields[1])
def _DiscoverNameServers():
import sys
if sys.platform in ('win32', 'nt'):
from . import win32dns
defaults['server']=win32dns.RegistryResolve()
elif sys.platform == 'darwin':
ParseOSXSysConfig()
else:
return ParseResolvConf()
def DiscoverNameServers():
"""Don't call, only here for backward compatability. We do discovery for
you automatically.
"""
pass
class DnsRequest:
""" high level Request object """
def __init__(self,*name,**args):
self.donefunc=None
self.py3async=None
self.defaults = {}
self.argparse(name,args)
self.defaults = self.args
self.tid = 0
self.resulttype = ''
if len(self.defaults['server']) == 0:
raise DNSError('No working name servers discovered')
def argparse(self,name,args):
if not name and 'name' in self.defaults:
args['name'] = self.defaults['name']
if type(name) is bytes or type(name) is str:
args['name']=name
else:
if len(name) == 1:
if name[0]:
args['name']=name[0]
if defaults['server_rotate'] and \
type(defaults['server']) == types.ListType:
defaults['server'] = defaults['server'][1:]+defaults['server'][:1]
for i in list(defaults.keys()):
if i not in args:
if i in self.defaults:
args[i]=self.defaults[i]
else:
args[i]=defaults[i]
if type(args['server']) == bytes or type(args['server']) == str:
args['server'] = [args['server']]
self.args=args
def socketInit(self,a,b):
self.s = socket.socket(a,b)
def processUDPReply(self):
if self.timeout > 0:
r,w,e = select.select([self.s],[],[],self.timeout)
if not len(r):
raise TimeoutError('Timeout')
(self.reply, self.from_address) = self.s.recvfrom(65535)
self.time_finish=time.time()
self.args['server']=self.ns
return self.processReply()
def _readall(self,f,count):
res = f.read(count)
while len(res) < count:
if self.timeout > 0:
# should we restart timeout everytime we get a dribble of data?
rem = self.time_start + self.timeout - time.time()
if rem <= 0: raise DNSError('Timeout')
self.s.settimeout(rem)
buf = f.read(count - len(res))
if not buf:
raise DNSError('incomplete reply - %d of %d read' % (len(res),count))
res += buf
return res
def processTCPReply(self):
if self.timeout > 0:
self.s.settimeout(self.timeout)
else:
self.s.settimeout(None)
f = self.s.makefile('rb')
try:
header = self._readall(f,2)
count = Lib.unpack16bit(header)
self.reply = self._readall(f,count)
finally:
f.close()
self.time_finish=time.time()
self.args['server']=self.ns
return self.processReply()
def processReply(self):
self.args['elapsed']=(self.time_finish-self.time_start)*1000
if not self.resulttype:
u = Lib.Munpacker(self.reply)
elif self.resulttype == 'default':
u = Lib.MunpackerDefault(self.reply)
elif self.resulttype == 'binary':
u = Lib.MunpackerBinary(self.reply)
elif self.resulttype == 'text':
u = Lib.MunpackerText(self.reply)
elif self.resulttype == 'integer':
u = Lib.MunpackerInteger(self.reply)
else:
raise SyntaxError('Unknown resulttype: ' + self.resulttype)
r=Lib.DnsResult(u,self.args)
r.args=self.args
#self.args=None # mark this DnsRequest object as used.
return r
#### TODO TODO TODO ####
# if protocol == 'tcp' and qtype == Type.AXFR:
# while 1:
# header = f.read(2)
# if len(header) < 2:
# print '========== EOF =========='
# break
# count = Lib.unpack16bit(header)
# if not count:
# print '========== ZERO COUNT =========='
# break
# print '========== NEXT =========='
# reply = f.read(count)
# if len(reply) != count:
# print '*** Incomplete reply ***'
# break
# u = Lib.Munpacker(reply)
# Lib.dumpM(u)
def getSource(self):
"Pick random source port to avoid DNS cache poisoning attack."
while True:
try:
source_port = random.randint(1024,65535)
self.s.bind(('', source_port))
break
except socket.error as msg:
# errno.EADDRINUSE, 'Address already in use'
if msg.errno != errno.EADDRINUSE: raise
def conn(self):
self.getSource()
self.s.connect((self.ns,self.port))
def qry(self,*name,**args):
'''
Request function for the DnsRequest class. In addition to standard
DNS args, the special pydns arg 'resulttype' can optionally be passed.
Valid resulttypes are 'default', 'text', 'decimal', and 'binary'.
Defaults are configured to be compatible with pydns:
AAAA: decimal
Others: text
'''
" needs a refactoring "
self.argparse(name,args)
#if not self.args:
# raise ArgumentError, 'reinitialize request before reuse'
protocol = self.args['protocol']
self.port = self.args['port']
self.tid = random.randint(0,65535)
self.timeout = self.args['timeout'];
opcode = self.args['opcode']
rd = self.args['rd']
server=self.args['server']
if 'resulttype' in self.args:
self.resulttype = self.args['resulttype']
else:
self.resulttype = 'default'
if type(self.args['qtype']) == bytes or type(self.args['qtype']) == str:
try:
qtype = getattr(Type, str(self.args['qtype'].upper()))
except AttributeError:
raise ArgumentError('unknown query type')
else:
qtype = self.args['qtype']
if 'name' not in self.args:
print((self.args))
raise ArgumentError('nothing to lookup')
qname = self.args['name']
if qtype == Type.AXFR and protocol != 'tcp':
print('Query type AXFR, protocol forced to TCP')
protocol = 'tcp'
#print('QTYPE %d(%s)' % (qtype, Type.typestr(qtype)))
m = Lib.Mpacker()
# jesus. keywords and default args would be good. TODO.
m.addHeader(self.tid,
0, opcode, 0, 0, rd, 0, 0, 0,
1, 0, 0, 0)
m.addQuestion(qname, qtype, Class.IN)
self.request = m.getbuf()
try:
if protocol == 'udp':
self.sendUDPRequest(server)
else:
self.sendTCPRequest(server)
except socket.error as reason:
raise SocketError(reason)
if self.py3async:
return None
else:
return self.response
def req(self,*name,**args):
" needs a refactoring "
self.argparse(name,args)
#if not self.args:
# raise ArgumentError, 'reinitialize request before reuse'
try:
if self.args['resulttype']:
raise ArgumentError('Restulttype {0} set with DNS.req, use DNS.qry to specify result type.'.format(self.args['resulttype']))
except:
# resulttype isn't set and that's what we want for DNS.req
pass
protocol = self.args['protocol']
self.port = self.args['port']
self.tid = random.randint(0,65535)
self.timeout = self.args['timeout'];
opcode = self.args['opcode']
rd = self.args['rd']
server=self.args['server']
if type(self.args['qtype']) == bytes or type(self.args['qtype']) == str:
try:
qtype = getattr(Type, str(self.args['qtype'].upper()))
except AttributeError:
raise ArgumentError('unknown query type')
else:
qtype = self.args['qtype']
if 'name' not in self.args:
print((self.args))
raise ArgumentError('nothing to lookup')
qname = self.args['name']
if qtype == Type.AXFR and protocol != 'tcp':
print('Query type AXFR, protocol forced to TCP')
protocol = 'tcp'
#print('QTYPE %d(%s)' % (qtype, Type.typestr(qtype)))
m = Lib.Mpacker()
# jesus. keywords and default args would be good. TODO.
m.addHeader(self.tid,
0, opcode, 0, 0, rd, 0, 0, 0,
1, 0, 0, 0)
m.addQuestion(qname, qtype, Class.IN)
self.request = m.getbuf()
try:
if protocol == 'udp':
self.sendUDPRequest(server)
else:
self.sendTCPRequest(server)
except socket.error as reason:
raise SocketError(reason)
if self.py3async:
return None
else:
return self.response
def sendUDPRequest(self, server):
"refactor me"
first_socket_error = None
self.response=None
for self.ns in server:
try:
if self.ns.count(':'):
if hasattr(socket,'has_ipv6') and socket.has_ipv6:
self.socketInit(socket.AF_INET6, socket.SOCK_DGRAM)
else: continue
else:
self.socketInit(socket.AF_INET, socket.SOCK_DGRAM)
try:
# TODO. Handle timeouts &c correctly (RFC)
self.time_start=time.time()
self.conn()
if not self.py3async:
self.s.send(self.request)
r=self.processUDPReply()
# Since we bind to the source port and connect to the
# destination port, we don't need to check that here,
# but do make sure it's actually a DNS request that the
# packet is in reply to.
while r.header['id'] != self.tid \
or self.from_address[1] != self.port:
r=self.processUDPReply()
self.response = r
# FIXME: check waiting async queries
finally:
if not self.py3async:
self.s.close()
except socket.error as e:
# Keep trying more nameservers, but preserve the first error
# that occurred so it can be reraised in case none of the
# servers worked:
first_socket_error = first_socket_error or e
continue
except TimeoutError as t:
first_socket_error = first_socket_error or t
continue
if self.response:
break
if not self.response and first_socket_error:
raise first_socket_error
def sendTCPRequest(self, server):
" do the work of sending a TCP request "
first_socket_error = None
self.response=None
for self.ns in server:
#print "trying tcp",self.ns
try:
if self.ns.count(':'):
if hasattr(socket,'has_ipv6') and socket.has_ipv6:
self.socketInit(socket.AF_INET6, socket.SOCK_STREAM)
else: continue
else:
self.socketInit(socket.AF_INET, socket.SOCK_STREAM)
try:
# TODO. Handle timeouts &c correctly (RFC)
self.time_start=time.time()
self.conn()
buf = Lib.pack16bit(len(self.request))+self.request
# Keep server from making sendall hang
self.s.setblocking(0)
# FIXME: throws WOULDBLOCK if request too large to fit in
# system buffer
self.s.sendall(buf)
# SHUT_WR breaks blocking IO with google DNS (8.8.8.8)
#self.s.shutdown(socket.SHUT_WR)
r=self.processTCPReply()
if r.header['id'] == self.tid:
self.response = r
break
finally:
self.s.close()
except socket.error as e:
first_socket_error = first_socket_error or e
continue
except TimeoutError as t:
first_socket_error = first_socket_error or t
continue
if self.response:
break
if not self.response and first_socket_error:
raise first_socket_error
#class DnsAsyncRequest(DnsRequest):
class DnsAsyncRequest(DnsRequest,asyncore.dispatcher_with_send):
" an asynchronous request object. out of date, probably broken "
def __init__(self,*name,**args):
DnsRequest.__init__(self, *name, **args)
# XXX todo
if 'done' in args and args['done']:
self.donefunc=args['done']
else:
self.donefunc=self.showResult
#self.realinit(name,args) # XXX todo
self.py3async=1
def conn(self):
self.getSource()
self.connect((self.ns,self.port))
self.time_start=time.time()
if 'start' in self.args and self.args['start']:
asyncore.dispatcher.go(self)
def socketInit(self,a,b):
self.create_socket(a,b)
asyncore.dispatcher.__init__(self)
self.s=self
def handle_read(self):
if self.args['protocol'] == 'udp':
self.response=self.processUDPReply()
if self.donefunc:
self.donefunc(*(self,))
def handle_connect(self):
self.send(self.request)
def handle_write(self):
pass
def showResult(self,*s):
self.response.show()
def ParseOSXSysConfig():
"Retrieves the current Mac OS X resolver settings using the scutil(8) command."
import os, re
scutil = os.popen('/usr/sbin/scutil --dns', 'r')
res_re = re.compile('^\s+nameserver[]0-9[]*\s*\:\s*(\S+)$')
sets = [ ]
currentset = None
while True:
l = scutil.readline()
if not l:
break
l = l.rstrip()
if len(l) < 1 or l[0] not in string.whitespace:
currentset = None
continue
m = res_re.match(l)
if m:
if currentset is None:
currentset = [ ]
sets.append(currentset)
currentset.append(m.group(1))
scutil.close()
# Someday: Figure out if we should do something other than simply concatenate the sets.
for currentset in sets:
defaults['server'].extend(currentset)
|