""" $Id$ 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 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)