# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license # Copyright (C) 2003-2017 Nominum, Inc. # # Permission to use, copy, modify, and distribute this software and its # documentation for any purpose with or without fee is hereby granted, # provided that the above copyright notice and this permission notice # appear in all copies. # # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. """DNS stub resolver.""" import socket import sys import time import random try: import threading as _threading except ImportError: import dummy_threading as _threading import dns.exception import dns.flags import dns.ipv4 import dns.ipv6 import dns.message import dns.name import dns.query import dns.rcode import dns.rdataclass import dns.rdatatype import dns.reversename import dns.tsig from ._compat import xrange, string_types if sys.platform == 'win32': try: import winreg as _winreg except ImportError: import _winreg # pylint: disable=import-error class NXDOMAIN(dns.exception.DNSException): """The DNS query name does not exist.""" supp_kwargs = {'qnames', 'responses'} fmt = None # we have our own __str__ implementation def _check_kwargs(self, qnames, responses=None): if not isinstance(qnames, (list, tuple, set)): raise AttributeError("qnames must be a list, tuple or set") if len(qnames) == 0: raise AttributeError("qnames must contain at least one element") if responses is None: responses = {} elif not isinstance(responses, dict): raise AttributeError("responses must be a dict(qname=response)") kwargs = dict(qnames=qnames, responses=responses) return kwargs def __str__(self): if 'qnames' not in self.kwargs: return super(NXDOMAIN, self).__str__() qnames = self.kwargs['qnames'] if len(qnames) > 1: msg = 'None of DNS query names exist' else: msg = 'The DNS query name does not exist' qnames = ', '.join(map(str, qnames)) return "{}: {}".format(msg, qnames) def canonical_name(self): if not 'qnames' in self.kwargs: raise TypeError("parametrized exception required") IN = dns.rdataclass.IN CNAME = dns.rdatatype.CNAME cname = None for qname in self.kwargs['qnames']: response = self.kwargs['responses'][qname] for answer in response.answer: if answer.rdtype != CNAME or answer.rdclass != IN: continue cname = answer.items[0].target.to_text() if cname is not None: return dns.name.from_text(cname) return self.kwargs['qnames'][0] canonical_name = property(canonical_name, doc=( "Return the unresolved canonical name.")) def __add__(self, e_nx): """Augment by results from another NXDOMAIN exception.""" qnames0 = list(self.kwargs.get('qnames', [])) responses0 = dict(self.kwargs.get('responses', {})) responses1 = e_nx.kwargs.get('responses', {}) for qname1 in e_nx.kwargs.get('qnames', []): if qname1 not in qnames0: qnames0.append(qname1) if qname1 in responses1: responses0[qname1] = responses1[qname1] return NXDOMAIN(qnames=qnames0, responses=responses0) def qnames(self): """All of the names that were tried. Returns a list of ``dns.name.Name``. """ return self.kwargs['qnames'] def responses(self): """A map from queried names to their NXDOMAIN responses. Returns a dict mapping a ``dns.name.Name`` to a ``dns.message.Message``. """ return self.kwargs['responses'] def response(self, qname): """The response for query *qname*. Returns a ``dns.message.Message``. """ return self.kwargs['responses'][qname] class YXDOMAIN(dns.exception.DNSException): """The DNS query name is too long after DNAME substitution.""" # The definition of the Timeout exception has moved from here to the # dns.exception module. We keep dns.resolver.Timeout defined for # backwards compatibility. Timeout = dns.exception.Timeout class NoAnswer(dns.exception.DNSException): """The DNS response does not contain an answer to the question.""" fmt = 'The DNS response does not contain an answer ' + \ 'to the question: {query}' supp_kwargs = {'response'} def _fmt_kwargs(self, **kwargs): return super(NoAnswer, self)._fmt_kwargs( query=kwargs['response'].question) class NoNameservers(dns.exception.DNSException): """All nameservers failed to answer the query. errors: list of servers and respective errors The type of errors is [(server IP address, any object convertible to string)]. Non-empty errors list will add explanatory message () """ msg = "All nameservers failed to answer the query." fmt = "%s {query}: {errors}" % msg[:-1] supp_kwargs = {'request', 'errors'} def _fmt_kwargs(self, **kwargs): srv_msgs = [] for err in kwargs['errors']: srv_msgs.append('Server {} {} port {} answered {}'.format(err[0], 'TCP' if err[1] else 'UDP', err[2], err[3])) return super(NoNameservers, self)._fmt_kwargs( query=kwargs['request'].question, errors='; '.join(srv_msgs)) class NotAbsolute(dns.exception.DNSException): """An absolute domain name is required but a relative name was provided.""" class NoRootSOA(dns.exception.DNSException): """There is no SOA RR at the DNS root name. This should never happen!""" class NoMetaqueries(dns.exception.DNSException): """DNS metaqueries are not allowed.""" class Answer(object): """DNS stub resolver answer. Instances of this class bundle up the result of a successful DNS resolution. For convenience, the answer object implements much of the sequence protocol, forwarding to its ``rrset`` attribute. E.g. ``for a in answer`` is equivalent to ``for a in answer.rrset``. ``answer[i]`` is equivalent to ``answer.rrset[i]``, and ``answer[i:j]`` is equivalent to ``answer.rrset[i:j]``. Note that CNAMEs or DNAMEs in the response may mean that answer RRset's name might not be the query name. """ def __init__(self, qname, rdtype, rdclass, response, raise_on_no_answer=True): self.qname = qname self.rdtype = rdtype self.rdclass = rdclass self.response = response min_ttl = -1 rrset = None for count in xrange(0, 15): try: rrset = response.find_rrset(response.answer, qname, rdclass, rdtype) if min_ttl == -1 or rrset.ttl < min_ttl: min_ttl = rrset.ttl break except KeyError: if rdtype != dns.rdatatype.CNAME: try: crrset = response.find_rrset(response.answer, qname, rdclass, dns.rdatatype.CNAME) if min_ttl == -1 or crrset.ttl < min_ttl: min_ttl = crrset.ttl for rd in crrset: qname = rd.target break continue except KeyError: if raise_on_no_answer: raise NoAnswer(response=response) if raise_on_no_answer: raise NoAnswer(response=response) if rrset is None and raise_on_no_answer: raise NoAnswer(response=response) self.canonical_name = qname self.rrset = rrset if rrset is None: while 1: # Look for a SOA RR whose owner name is a superdomain # of qname. try: srrset = response.find_rrset(response.authority, qname, rdclass, dns.rdatatype.SOA) if min_ttl == -1 or srrset.ttl < min_ttl: min_ttl = srrset.ttl if srrset[0].minimum < min_ttl: min_ttl = srrset[0].minimum break except KeyError: try: qname = qname.parent() except dns.name.NoParent: break self.expiration = time.time() + min_ttl def __getattr__(self, attr): if attr == 'name': return self.rrset.name elif attr == 'ttl': return self.rrset.ttl elif attr == 'covers': return self.rrset.covers elif attr == 'rdclass': return self.rrset.rdclass elif attr == 'rdtype': return self.rrset.rdtype else: raise AttributeError(attr) def __len__(self): return self.rrset and len(self.rrset) or 0 def __iter__(self): return self.rrset and iter(self.rrset) or iter(tuple()) def __getitem__(self, i): if self.rrset is None: raise IndexError return self.rrset[i] def __delitem__(self, i): if self.rrset is None: raise IndexError del self.rrset[i] class Cache(object): """Simple thread-safe DNS answer cache.""" def __init__(self, cleaning_interval=300.0): """*cleaning_interval*, a ``float`` is the number of seconds between periodic cleanings. """ self.data = {} self.cleaning_interval = cleaning_interval self.next_cleaning = time.time() + self.cleaning_interval self.lock = _threading.Lock() def _maybe_clean(self): """Clean the cache if it's time to do so.""" now = time.time() if self.next_cleaning <= now: keys_to_delete = [] for (k, v) in self.data.items(): if v.expiration <= now: keys_to_delete.append(k) for k in keys_to_delete: del self.data[k] now = time.time() self.next_cleaning = now + self.cleaning_interval def get(self, key): """Get the answer associated with *key*. Returns None if no answer is cached for the key. *key*, a ``(dns.name.Name, int, int)`` tuple whose values are the query name, rdtype, and rdclass respectively. Returns a ``dns.resolver.Answer`` or ``None``. """ try: self.lock.acquire() self._maybe_clean() v = self.data.get(key) if v is None or v.expiration <= time.time(): return None return v finally: self.lock.release() def put(self, key, value): """Associate key and value in the cache. *key*, a ``(dns.name.Name, int, int)`` tuple whose values are the query name, rdtype, and rdclass respectively. *value*, a ``dns.resolver.Answer``, the answer. """ try: self.lock.acquire() self._maybe_clean() self.data[key] = value finally: self.lock.release() def flush(self, key=None): """Flush the cache. If *key* is not ``None``, only that item is flushed. Otherwise the entire cache is flushed. *key*, a ``(dns.name.Name, int, int)`` tuple whose values are the query name, rdtype, and rdclass respectively. """ try: self.lock.acquire() if key is not None: if key in self.data: del self.data[key] else: self.data = {} self.next_cleaning = time.time() + self.cleaning_interval finally: self.lock.release() class LRUCacheNode(object): """LRUCache node.""" def __init__(self, key, value): self.key = key self.value = value self.prev = self self.next = self def link_before(self, node): self.prev = node.prev self.next = node node.prev.next = self node.prev = self def link_after(self, node): self.prev = node self.next = node.next node.next.prev = self node.next = self def unlink(self): self.next.prev = self.prev self.prev.next = self.next class LRUCache(object): """Thread-safe, bounded, least-recently-used DNS answer cache. This cache is better than the simple cache (above) if you're running a web crawler or other process that does a lot of resolutions. The LRUCache has a maximum number of nodes, and when it is full, the least-recently used node is removed to make space for a new one. """ def __init__(self, max_size=100000): """*max_size*, an ``int``, is the maximum number of nodes to cache; it must be greater than 0. """ self.data = {} self.set_max_size(max_size) self.sentinel = LRUCacheNode(None, None) self.lock = _threading.Lock() def set_max_size(self, max_size): if max_size < 1: max_size = 1 self.max_size = max_size def get(self, key): """Get the answer associated with *key*. Returns None if no answer is cached for the key. *key*, a ``(dns.name.Name, int, int)`` tuple whose values are the query name, rdtype, and rdclass respectively. Returns a ``dns.resolver.Answer`` or ``None``. """ try: self.lock.acquire() node = self.data.get(key) if node is None: return None # Unlink because we're either going to move the node to the front # of the LRU list or we're going to free it. node.unlink() if node.value.expiration <= time.time(): del self.data[node.key] return None node.link_after(self.sentinel) return node.value finally: self.lock.release() def put(self, key, value): """Associate key and value in the cache. *key*, a ``(dns.name.Name, int, int)`` tuple whose values are the query name, rdtype, and rdclass respectively. *value*, a ``dns.resolver.Answer``, the answer. """ try: self.lock.acquire() node = self.data.get(key) if node is not None: node.unlink() del self.data[node.key] while len(self.data) >= self.max_size: node = self.sentinel.prev node.unlink() del self.data[node.key] node = LRUCacheNode(key, value) node.link_after(self.sentinel) self.data[key] = node finally: self.lock.release() def flush(self, key=None): """Flush the cache. If *key* is not ``None``, only that item is flushed. Otherwise the entire cache is flushed. *key*, a ``(dns.name.Name, int, int)`` tuple whose values are the query name, rdtype, and rdclass respectively. """ try: self.lock.acquire() if key is not None: node = self.data.get(key) if node is not None: node.unlink() del self.data[node.key] else: node = self.sentinel.next while node != self.sentinel: next = node.next node.prev = None node.next = None node = next self.data = {} finally: self.lock.release() class Resolver(object): """DNS stub resolver.""" def __init__(self, filename='/etc/resolv.conf', configure=True): """*filename*, a ``text`` or file object, specifying a file in standard /etc/resolv.conf format. This parameter is meaningful only when *configure* is true and the platform is POSIX. *configure*, a ``bool``. If True (the default), the resolver instance is configured in the normal fashion for the operating system the resolver is running on. (I.e. by reading a /etc/resolv.conf file on POSIX systems and from the registry on Windows systems.) """ self.domain = None self.nameservers = None self.nameserver_ports = None self.port = None self.search = None self.timeout = None self.lifetime = None self.keyring = None self.keyname = None self.keyalgorithm = None self.edns = None self.ednsflags = None self.payload = None self.cache = None self.flags = None self.retry_servfail = False self.rotate = False self.reset() if configure: if sys.platform == 'win32': self.read_registry() elif filename: self.read_resolv_conf(filename) def reset(self): """Reset all resolver configuration to the defaults.""" self.domain = \ dns.name.Name(dns.name.from_text(socket.gethostname())[1:]) if len(self.domain) == 0: self.domain = dns.name.root self.nameservers = [] self.nameserver_ports = {} self.port = 53 self.search = [] self.timeout = 2.0 self.lifetime = 30.0 self.keyring = None self.keyname = None self.keyalgorithm = dns.tsig.default_algorithm self.edns = -1 self.ednsflags = 0 self.payload = 0 self.cache = None self.flags = None self.retry_servfail = False self.rotate = False def read_resolv_conf(self, f): """Process *f* as a file in the /etc/resolv.conf format. If f is a ``text``, it is used as the name of the file to open; otherwise it is treated as the file itself.""" if isinstance(f, string_types): try: f = open(f, 'r') except IOError: # /etc/resolv.conf doesn't exist, can't be read, etc. # We'll just use the default resolver configuration. self.nameservers = ['127.0.0.1'] return want_close = True else: want_close = False try: for l in f: if len(l) == 0 or l[0] == '#' or l[0] == ';': continue tokens = l.split() # Any line containing less than 2 tokens is malformed if len(tokens) < 2: continue if tokens[0] == 'nameserver': self.nameservers.append(tokens[1]) elif tokens[0] == 'domain': self.domain = dns.name.from_text(tokens[1]) elif tokens[0] == 'search': for suffix in tokens[1:]: self.search.append(dns.name.from_text(suffix)) elif tokens[0] == 'options': if 'rotate' in tokens[1:]: self.rotate = True finally: if want_close: f.close() if len(self.nameservers) == 0: self.nameservers.append('127.0.0.1') def _determine_split_char(self, entry): # # The windows registry irritatingly changes the list element # delimiter in between ' ' and ',' (and vice-versa) in various # versions of windows. # if entry.find(' ') >= 0: split_char = ' ' elif entry.find(',') >= 0: split_char = ',' else: # probably a singleton; treat as a space-separated list. split_char = ' ' return split_char def _config_win32_nameservers(self, nameservers): # we call str() on nameservers to convert it from unicode to ascii nameservers = str(nameservers) split_char = self._determine_split_char(nameservers) ns_list = nameservers.split(split_char) for ns in ns_list: if ns not in self.nameservers: self.nameservers.append(ns) def _config_win32_domain(self, domain): # we call str() on domain to convert it from unicode to ascii self.domain = dns.name.from_text(str(domain)) def _config_win32_search(self, search): # we call str() on search to convert it from unicode to ascii search = str(search) split_char = self._determine_split_char(search) search_list = search.split(split_char) for s in search_list: if s not in self.search: self.search.append(dns.name.from_text(s)) def _config_win32_fromkey(self, key, always_try_domain): try: servers, rtype = _winreg.QueryValueEx(key, 'NameServer') except WindowsError: # pylint: disable=undefined-variable servers = None if servers: self._config_win32_nameservers(servers) if servers or always_try_domain: try: dom, rtype = _winreg.QueryValueEx(key, 'Domain') if dom: self._config_win32_domain(dom) except WindowsError: # pylint: disable=undefined-variable pass else: try: servers, rtype = _winreg.QueryValueEx(key, 'DhcpNameServer') except WindowsError: # pylint: disable=undefined-variable servers = None if servers: self._config_win32_nameservers(servers) try: dom, rtype = _winreg.QueryValueEx(key, 'DhcpDomain') if dom: self._config_win32_domain(dom) except WindowsError: # pylint: disable=undefined-variable pass try: search, rtype = _winreg.QueryValueEx(key, 'SearchList') except WindowsError: # pylint: disable=undefined-variable search = None if search: self._config_win32_search(search) def read_registry(self): """Extract resolver configuration from the Windows registry.""" lm = _winreg.ConnectRegistry(None, _winreg.HKEY_LOCAL_MACHINE) want_scan = False try: try: # XP, 2000 tcp_params = _winreg.OpenKey(lm, r'SYSTEM\CurrentControlSet' r'\Services\Tcpip\Parameters') want_scan = True except EnvironmentError: # ME tcp_params = _winreg.OpenKey(lm, r'SYSTEM\CurrentControlSet' r'\Services\VxD\MSTCP') try: self._config_win32_fromkey(tcp_params, True) finally: tcp_params.Close() if want_scan: interfaces = _winreg.OpenKey(lm, r'SYSTEM\CurrentControlSet' r'\Services\Tcpip\Parameters' r'\Interfaces') try: i = 0 while True: try: guid = _winreg.EnumKey(interfaces, i) i += 1 key = _winreg.OpenKey(interfaces, guid) if not self._win32_is_nic_enabled(lm, guid, key): continue try: self._config_win32_fromkey(key, False) finally: key.Close() except EnvironmentError: break finally: interfaces.Close() finally: lm.Close() def _win32_is_nic_enabled(self, lm, guid, interface_key): # Look in the Windows Registry to determine whether the network # interface corresponding to the given guid is enabled. # # (Code contributed by Paul Marks, thanks!) # try: # This hard-coded location seems to be consistent, at least # from Windows 2000 through Vista. connection_key = _winreg.OpenKey( lm, r'SYSTEM\CurrentControlSet\Control\Network' r'\{4D36E972-E325-11CE-BFC1-08002BE10318}' r'\%s\Connection' % guid) try: # The PnpInstanceID points to a key inside Enum (pnp_id, ttype) = _winreg.QueryValueEx( connection_key, 'PnpInstanceID') if ttype != _winreg.REG_SZ: raise ValueError device_key = _winreg.OpenKey( lm, r'SYSTEM\CurrentControlSet\Enum\%s' % pnp_id) try: # Get ConfigFlags for this device (flags, ttype) = _winreg.QueryValueEx( device_key, 'ConfigFlags') if ttype != _winreg.REG_DWORD: raise ValueError # Based on experimentation, bit 0x1 indicates that the # device is disabled. return not flags & 0x1 finally: device_key.Close() finally: connection_key.Close() except (EnvironmentError, ValueError): # Pre-vista, enabled interfaces seem to have a non-empty # NTEContextList; this was how dnspython detected enabled # nics before the code above was contributed. We've retained # the old method since we don't know if the code above works # on Windows 95/98/ME. try: (nte, ttype) = _winreg.QueryValueEx(interface_key, 'NTEContextList') return nte is not None except WindowsError: # pylint: disable=undefined-variable return False def _compute_timeout(self, start, lifetime=None): lifetime = self.lifetime if lifetime is None else lifetime now = time.time() duration = now - start if duration < 0: if duration < -1: # Time going backwards is bad. Just give up. raise Timeout(timeout=duration) else: # Time went backwards, but only a little. This can # happen, e.g. under vmware with older linux kernels. # Pretend it didn't happen. now = start if duration >= lifetime: raise Timeout(timeout=duration) return min(lifetime - duration, self.timeout) def query(self, qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, raise_on_no_answer=True, source_port=0, lifetime=None): """Query nameservers to find the answer to the question. The *qname*, *rdtype*, and *rdclass* parameters may be objects of the appropriate type, or strings that can be converted into objects of the appropriate type. *qname*, a ``dns.name.Name`` or ``text``, the query name. *rdtype*, an ``int`` or ``text``, the query type. *rdclass*, an ``int`` or ``text``, the query class. *tcp*, a ``bool``. If ``True``, use TCP to make the query. *source*, a ``text`` or ``None``. If not ``None``, bind to this IP address when making queries. *raise_on_no_answer*, a ``bool``. If ``True``, raise ``dns.resolver.NoAnswer`` if there's no answer to the question. *source_port*, an ``int``, the port from which to send the message. *lifetime*, a ``float``, how long query should run before timing out. Raises ``dns.exception.Timeout`` if no answers could be found in the specified lifetime. Raises ``dns.resolver.NXDOMAIN`` if the query name does not exist. Raises ``dns.resolver.YXDOMAIN`` if the query name is too long after DNAME substitution. Raises ``dns.resolver.NoAnswer`` if *raise_on_no_answer* is ``True`` and the query name exists but has no RRset of the desired type and class. Raises ``dns.resolver.NoNameservers`` if no non-broken nameservers are available to answer the question. Returns a ``dns.resolver.Answer`` instance. """ if isinstance(qname, string_types): qname = dns.name.from_text(qname, None) if isinstance(rdtype, string_types): rdtype = dns.rdatatype.from_text(rdtype) if dns.rdatatype.is_metatype(rdtype): raise NoMetaqueries if isinstance(rdclass, string_types): rdclass = dns.rdataclass.from_text(rdclass) if dns.rdataclass.is_metaclass(rdclass): raise NoMetaqueries qnames_to_try = [] if qname.is_absolute(): qnames_to_try.append(qname) else: if len(qname) > 1: qnames_to_try.append(qname.concatenate(dns.name.root)) if self.search: for suffix in self.search: qnames_to_try.append(qname.concatenate(suffix)) else: qnames_to_try.append(qname.concatenate(self.domain)) all_nxdomain = True nxdomain_responses = {} start = time.time() _qname = None # make pylint happy for _qname in qnames_to_try: if self.cache: answer = self.cache.get((_qname, rdtype, rdclass)) if answer is not None: if answer.rrset is None and raise_on_no_answer: raise NoAnswer(response=answer.response) else: return answer request = dns.message.make_query(_qname, rdtype, rdclass) if self.keyname is not None: request.use_tsig(self.keyring, self.keyname, algorithm=self.keyalgorithm) request.use_edns(self.edns, self.ednsflags, self.payload) if self.flags is not None: request.flags = self.flags response = None # # make a copy of the servers list so we can alter it later. # nameservers = self.nameservers[:] errors = [] if self.rotate: random.shuffle(nameservers) backoff = 0.10 while response is None: if len(nameservers) == 0: raise NoNameservers(request=request, errors=errors) for nameserver in nameservers[:]: timeout = self._compute_timeout(start, lifetime) port = self.nameserver_ports.get(nameserver, self.port) try: tcp_attempt = tcp if tcp: response = dns.query.tcp(request, nameserver, timeout, port, source=source, source_port=source_port) else: response = dns.query.udp(request, nameserver, timeout, port, source=source, source_port=source_port) if response.flags & dns.flags.TC: # Response truncated; retry with TCP. tcp_attempt = True timeout = self._compute_timeout(start, lifetime) response = \ dns.query.tcp(request, nameserver, timeout, port, source=source, source_port=source_port) except (socket.error, dns.exception.Timeout) as ex: # # Communication failure or timeout. Go to the # next server # errors.append((nameserver, tcp_attempt, port, ex, response)) response = None continue except dns.query.UnexpectedSource as ex: # # Who knows? Keep going. # errors.append((nameserver, tcp_attempt, port, ex, response)) response = None continue except dns.exception.FormError as ex: # # We don't understand what this server is # saying. Take it out of the mix and # continue. # nameservers.remove(nameserver) errors.append((nameserver, tcp_attempt, port, ex, response)) response = None continue except EOFError as ex: # # We're using TCP and they hung up on us. # Probably they don't support TCP (though # they're supposed to!). Take it out of the # mix and continue. # nameservers.remove(nameserver) errors.append((nameserver, tcp_attempt, port, ex, response)) response = None continue rcode = response.rcode() if rcode == dns.rcode.YXDOMAIN: ex = YXDOMAIN() errors.append((nameserver, tcp_attempt, port, ex, response)) raise ex if rcode == dns.rcode.NOERROR or \ rcode == dns.rcode.NXDOMAIN: break # # We got a response, but we're not happy with the # rcode in it. Remove the server from the mix if # the rcode isn't SERVFAIL. # if rcode != dns.rcode.SERVFAIL or not self.retry_servfail: nameservers.remove(nameserver) errors.append((nameserver, tcp_attempt, port, dns.rcode.to_text(rcode), response)) response = None if response is not None: break # # All nameservers failed! # if len(nameservers) > 0: # # But we still have servers to try. Sleep a bit # so we don't pound them! # timeout = self._compute_timeout(start, lifetime) sleep_time = min(timeout, backoff) backoff *= 2 time.sleep(sleep_time) if response.rcode() == dns.rcode.NXDOMAIN: nxdomain_responses[_qname] = response continue all_nxdomain = False break if all_nxdomain: raise NXDOMAIN(qnames=qnames_to_try, responses=nxdomain_responses) answer = Answer(_qname, rdtype, rdclass, response, raise_on_no_answer) if self.cache: self.cache.put((_qname, rdtype, rdclass), answer) return answer def use_tsig(self, keyring, keyname=None, algorithm=dns.tsig.default_algorithm): """Add a TSIG signature to the query. See the documentation of the Message class for a complete description of the keyring dictionary. *keyring*, a ``dict``, the TSIG keyring to use. If a *keyring* is specified but a *keyname* is not, then the key used will be the first key in the *keyring*. Note that the order of keys in a dictionary is not defined, so applications should supply a keyname when a keyring is used, unless they know the keyring contains only one key. *keyname*, a ``dns.name.Name`` or ``None``, the name of the TSIG key to use; defaults to ``None``. The key must be defined in the keyring. *algorithm*, a ``dns.name.Name``, the TSIG algorithm to use. """ self.keyring = keyring if keyname is None: self.keyname = list(self.keyring.keys())[0] else: self.keyname = keyname self.keyalgorithm = algorithm def use_edns(self, edns, ednsflags, payload): """Configure EDNS behavior. *edns*, an ``int``, is the EDNS level to use. Specifying ``None``, ``False``, or ``-1`` means "do not use EDNS", and in this case the other parameters are ignored. Specifying ``True`` is equivalent to specifying 0, i.e. "use EDNS0". *ednsflags*, an ``int``, the EDNS flag values. *payload*, an ``int``, is the EDNS sender's payload field, which is the maximum size of UDP datagram the sender can handle. I.e. how big a response to this message can be. """ if edns is None: edns = -1 self.edns = edns self.ednsflags = ednsflags self.payload = payload def set_flags(self, flags): """Overrides the default flags with your own. *flags*, an ``int``, the message flags to use. """ self.flags = flags #: The default resolver. default_resolver = None def get_default_resolver(): """Get the default resolver, initializing it if necessary.""" if default_resolver is None: reset_default_resolver() return default_resolver def reset_default_resolver(): """Re-initialize default resolver. Note that the resolver configuration (i.e. /etc/resolv.conf on UNIX systems) will be re-read immediately. """ global default_resolver default_resolver = Resolver() def query(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, raise_on_no_answer=True, source_port=0, lifetime=None): """Query nameservers to find the answer to the question. This is a convenience function that uses the default resolver object to make the query. See ``dns.resolver.Resolver.query`` for more information on the parameters. """ return get_default_resolver().query(qname, rdtype, rdclass, tcp, source, raise_on_no_answer, source_port, lifetime) def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False, resolver=None): """Find the name of the zone which contains the specified name. *name*, an absolute ``dns.name.Name`` or ``text``, the query name. *rdclass*, an ``int``, the query class. *tcp*, a ``bool``. If ``True``, use TCP to make the query. *resolver*, a ``dns.resolver.Resolver`` or ``None``, the resolver to use. If ``None``, the default resolver is used. Raises ``dns.resolver.NoRootSOA`` if there is no SOA RR at the DNS root. (This is only likely to happen if you're using non-default root servers in your network and they are misconfigured.) Returns a ``dns.name.Name``. """ if isinstance(name, string_types): name = dns.name.from_text(name, dns.name.root) if resolver is None: resolver = get_default_resolver() if not name.is_absolute(): raise NotAbsolute(name) while 1: try: answer = resolver.query(name, dns.rdatatype.SOA, rdclass, tcp) if answer.rrset.name == name: return name # otherwise we were CNAMEd or DNAMEd and need to look higher except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer): pass try: name = name.parent() except dns.name.NoParent: raise NoRootSOA # # Support for overriding the system resolver for all python code in the # running process. # _protocols_for_socktype = { socket.SOCK_DGRAM: [socket.SOL_UDP], socket.SOCK_STREAM: [socket.SOL_TCP], } _resolver = None _original_getaddrinfo = socket.getaddrinfo _original_getnameinfo = socket.getnameinfo _original_getfqdn = socket.getfqdn _original_gethostbyname = socket.gethostbyname _original_gethostbyname_ex = socket.gethostbyname_ex _original_gethostbyaddr = socket.gethostbyaddr def _getaddrinfo(host=None, service=None, family=socket.AF_UNSPEC, socktype=0, proto=0, flags=0): if flags & (socket.AI_ADDRCONFIG | socket.AI_V4MAPPED) != 0: raise NotImplementedError if host is None and service is None: raise socket.gaierror(socket.EAI_NONAME) v6addrs = [] v4addrs = [] canonical_name = None try: # Is host None or a V6 address literal? if host is None: canonical_name = 'localhost' if flags & socket.AI_PASSIVE != 0: v6addrs.append('::') v4addrs.append('0.0.0.0') else: v6addrs.append('::1') v4addrs.append('127.0.0.1') else: parts = host.split('%') if len(parts) == 2: ahost = parts[0] else: ahost = host addr = dns.ipv6.inet_aton(ahost) v6addrs.append(host) canonical_name = host except Exception: try: # Is it a V4 address literal? addr = dns.ipv4.inet_aton(host) v4addrs.append(host) canonical_name = host except Exception: if flags & socket.AI_NUMERICHOST == 0: try: if family == socket.AF_INET6 or family == socket.AF_UNSPEC: v6 = _resolver.query(host, dns.rdatatype.AAAA, raise_on_no_answer=False) # Note that setting host ensures we query the same name # for A as we did for AAAA. host = v6.qname canonical_name = v6.canonical_name.to_text(True) if v6.rrset is not None: for rdata in v6.rrset: v6addrs.append(rdata.address) if family == socket.AF_INET or family == socket.AF_UNSPEC: v4 = _resolver.query(host, dns.rdatatype.A, raise_on_no_answer=False) host = v4.qname canonical_name = v4.canonical_name.to_text(True) if v4.rrset is not None: for rdata in v4.rrset: v4addrs.append(rdata.address) except dns.resolver.NXDOMAIN: raise socket.gaierror(socket.EAI_NONAME) except Exception: raise socket.gaierror(socket.EAI_SYSTEM) port = None try: # Is it a port literal? if service is None: port = 0 else: port = int(service) except Exception: if flags & socket.AI_NUMERICSERV == 0: try: port = socket.getservbyname(service) except Exception: pass if port is None: raise socket.gaierror(socket.EAI_NONAME) tuples = [] if socktype == 0: socktypes = [socket.SOCK_DGRAM, socket.SOCK_STREAM] else: socktypes = [socktype] if flags & socket.AI_CANONNAME != 0: cname = canonical_name else: cname = '' if family == socket.AF_INET6 or family == socket.AF_UNSPEC: for addr in v6addrs: for socktype in socktypes: for proto in _protocols_for_socktype[socktype]: tuples.append((socket.AF_INET6, socktype, proto, cname, (addr, port, 0, 0))) if family == socket.AF_INET or family == socket.AF_UNSPEC: for addr in v4addrs: for socktype in socktypes: for proto in _protocols_for_socktype[socktype]: tuples.append((socket.AF_INET, socktype, proto, cname, (addr, port))) if len(tuples) == 0: raise socket.gaierror(socket.EAI_NONAME) return tuples def _getnameinfo(sockaddr, flags=0): host = sockaddr[0] port = sockaddr[1] if len(sockaddr) == 4: scope = sockaddr[3] family = socket.AF_INET6 else: scope = None family = socket.AF_INET tuples = _getaddrinfo(host, port, family, socket.SOCK_STREAM, socket.SOL_TCP, 0) if len(tuples) > 1: raise socket.error('sockaddr resolved to multiple addresses') addr = tuples[0][4][0] if flags & socket.NI_DGRAM: pname = 'udp' else: pname = 'tcp' qname = dns.reversename.from_address(addr) if flags & socket.NI_NUMERICHOST == 0: try: answer = _resolver.query(qname, 'PTR') hostname = answer.rrset[0].target.to_text(True) except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer): if flags & socket.NI_NAMEREQD: raise socket.gaierror(socket.EAI_NONAME) hostname = addr if scope is not None: hostname += '%' + str(scope) else: hostname = addr if scope is not None: hostname += '%' + str(scope) if flags & socket.NI_NUMERICSERV: service = str(port) else: service = socket.getservbyport(port, pname) return (hostname, service) def _getfqdn(name=None): if name is None: name = socket.gethostname() try: return _getnameinfo(_getaddrinfo(name, 80)[0][4])[0] except Exception: return name def _gethostbyname(name): return _gethostbyname_ex(name)[2][0] def _gethostbyname_ex(name): aliases = [] addresses = [] tuples = _getaddrinfo(name, 0, socket.AF_INET, socket.SOCK_STREAM, socket.SOL_TCP, socket.AI_CANONNAME) canonical = tuples[0][3] for item in tuples: addresses.append(item[4][0]) # XXX we just ignore aliases return (canonical, aliases, addresses) def _gethostbyaddr(ip): try: dns.ipv6.inet_aton(ip) sockaddr = (ip, 80, 0, 0) family = socket.AF_INET6 except Exception: sockaddr = (ip, 80) family = socket.AF_INET (name, port) = _getnameinfo(sockaddr, socket.NI_NAMEREQD) aliases = [] addresses = [] tuples = _getaddrinfo(name, 0, family, socket.SOCK_STREAM, socket.SOL_TCP, socket.AI_CANONNAME) canonical = tuples[0][3] for item in tuples: addresses.append(item[4][0]) # XXX we just ignore aliases return (canonical, aliases, addresses) def override_system_resolver(resolver=None): """Override the system resolver routines in the socket module with versions which use dnspython's resolver. This can be useful in testing situations where you want to control the resolution behavior of python code without having to change the system's resolver settings (e.g. /etc/resolv.conf). The resolver to use may be specified; if it's not, the default resolver will be used. resolver, a ``dns.resolver.Resolver`` or ``None``, the resolver to use. """ if resolver is None: resolver = get_default_resolver() global _resolver _resolver = resolver socket.getaddrinfo = _getaddrinfo socket.getnameinfo = _getnameinfo socket.getfqdn = _getfqdn socket.gethostbyname = _gethostbyname socket.gethostbyname_ex = _gethostbyname_ex socket.gethostbyaddr = _gethostbyaddr def restore_system_resolver(): """Undo the effects of prior override_system_resolver().""" global _resolver _resolver = None socket.getaddrinfo = _original_getaddrinfo socket.getnameinfo = _original_getnameinfo socket.getfqdn = _original_getfqdn socket.gethostbyname = _original_gethostbyname socket.gethostbyname_ex = _original_gethostbyname_ex socket.gethostbyaddr = _original_gethostbyaddr