# 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.""" from urllib.parse import urlparse import contextlib import socket import sys import time import random import warnings try: import threading as _threading except ImportError: # pragma: no cover import dummy_threading as _threading # type: ignore import dns.exception import dns.flags import dns.inet 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 if sys.platform == 'win32': import winreg # pragma: no cover 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().__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) @property def canonical_name(self): """Return the unresolved canonical name.""" if 'qnames' not 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[0].target.to_text() if cname is not None: return dns.name.from_text(cname) return self.kwargs['qnames'][0] 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()._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()._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 NoResolverConfiguration(dns.exception.DNSException): """Resolver configuration could not be read or specified no nameservers.""" class Answer: """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, nameserver=None, port=None): self.qname = qname self.rdtype = rdtype self.rdclass = rdclass self.response = response self.nameserver = nameserver self.port = port min_ttl = -1 rrset = None for count in range(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: # Exit the chaining loop break 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): # pragma: no cover 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: """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``. """ with self.lock: self._maybe_clean() v = self.data.get(key) if v is None or v.expiration <= time.time(): return None return v 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. """ with self.lock: self._maybe_clean() self.data[key] = value 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. """ with self.lock: 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 class LRUCacheNode: """LRUCache node.""" def __init__(self, key, value): self.key = key self.value = value self.prev = self self.next = 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: """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.sentinel.prev = self.sentinel self.sentinel.next = self.sentinel 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``. """ with self.lock: 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 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. """ with self.lock: 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 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. """ with self.lock: 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.unlink() node = next self.data = {} class _Resolution: """Helper class for dns.resolver.Resolver.resolve(). All of the "business logic" of resolution is encapsulated in this class, allowing us to have multiple resolve() implementations using different I/O schemes without copying all of the complicated logic. This class is a "friend" to dns.resolver.Resolver and manipulates resolver data structures directly. """ def __init__(self, resolver, qname, rdtype, rdclass, tcp, raise_on_no_answer, search): if isinstance(qname, str): qname = dns.name.from_text(qname, None) rdtype = dns.rdatatype.RdataType.make(rdtype) if dns.rdatatype.is_metatype(rdtype): raise NoMetaqueries rdclass = dns.rdataclass.RdataClass.make(rdclass) if dns.rdataclass.is_metaclass(rdclass): raise NoMetaqueries self.resolver = resolver self.qnames_to_try = resolver._get_qnames_to_try(qname, search) self.qnames = self.qnames_to_try[:] self.rdtype = rdtype self.rdclass = rdclass self.tcp = tcp self.raise_on_no_answer = raise_on_no_answer self.nxdomain_responses = {} # # Initialize other things to help analysis tools self.qname = dns.name.empty self.nameservers = [] self.current_nameservers = [] self.errors = [] self.nameserver = None self.port = 0 self.tcp_attempt = False self.retry_with_tcp = False self.request = None self.backoff = 0 def next_request(self): """Get the next request to send, and check the cache. Returns a (request, answer) tuple. At most one of request or answer will not be None. """ # We return a tuple instead of Union[Message,Answer] as it lets # the caller avoid isinstance(). while len(self.qnames) > 0: self.qname = self.qnames.pop(0) # Do we know the answer? if self.resolver.cache: answer = self.resolver.cache.get((self.qname, self.rdtype, self.rdclass)) if answer is not None: if answer.rrset is None and self.raise_on_no_answer: raise NoAnswer(response=answer.response) else: return (None, answer) answer = self.resolver.cache.get((self.qname, dns.rdatatype.ANY, self.rdclass)) if answer is not None and \ answer.response.rcode() == dns.rcode.NXDOMAIN: # cached NXDOMAIN; record it and continue to next # name. self.nxdomain_responses[self.qname] = answer.response continue # Build the request request = dns.message.make_query(self.qname, self.rdtype, self.rdclass) if self.resolver.keyname is not None: request.use_tsig(self.resolver.keyring, self.resolver.keyname, algorithm=self.resolver.keyalgorithm) request.use_edns(self.resolver.edns, self.resolver.ednsflags, self.resolver.payload) if self.resolver.flags is not None: request.flags = self.resolver.flags self.nameservers = self.resolver.nameservers[:] if self.resolver.rotate: random.shuffle(self.nameservers) self.current_nameservers = self.nameservers[:] self.errors = [] self.nameserver = None self.tcp_attempt = False self.retry_with_tcp = False self.request = request self.backoff = 0.10 return (request, None) # # We've tried everything and only gotten NXDOMAINs. (We know # it's only NXDOMAINs as anything else would have returned # before now.) # raise NXDOMAIN(qnames=self.qnames_to_try, responses=self.nxdomain_responses) def next_nameserver(self): if self.retry_with_tcp: assert self.nameserver is not None self.tcp_attempt = True self.retry_with_tcp = False return (self.nameserver, self.port, True, 0) backoff = 0 if not self.current_nameservers: if len(self.nameservers) == 0: # Out of things to try! raise NoNameservers(request=self.request, errors=self.errors) self.current_nameservers = self.nameservers[:] backoff = self.backoff self.backoff = min(self.backoff * 2, 2) self.nameserver = self.current_nameservers.pop(0) self.port = self.resolver.nameserver_ports.get(self.nameserver, self.resolver.port) self.tcp_attempt = self.tcp return (self.nameserver, self.port, self.tcp_attempt, backoff) def query_result(self, response, ex): # # returns an (answer: Answer, end_loop: bool) tuple. # if ex: # Exception during I/O or from_wire() assert response is None self.errors.append((self.nameserver, self.tcp_attempt, self.port, ex, response)) if isinstance(ex, dns.exception.FormError) or \ isinstance(ex, EOFError) or \ isinstance(ex, OSError) or \ isinstance(ex, NotImplementedError): # This nameserver is no good, take it out of the mix. self.nameservers.remove(self.nameserver) elif isinstance(ex, dns.message.Truncated): if self.tcp_attempt: # Truncation with TCP is no good! self.nameservers.remove(self.nameserver) else: self.retry_with_tcp = True return (None, False) # We got an answer! assert response is not None rcode = response.rcode() if rcode == dns.rcode.NOERROR: answer = Answer(self.qname, self.rdtype, self.rdclass, response, self.nameserver, self.port) if self.resolver.cache: self.resolver.cache.put((self.qname, self.rdtype, self.rdclass), answer) if answer.rrset is None and self.raise_on_no_answer: raise NoAnswer(response=answer.response) return (answer, True) elif rcode == dns.rcode.NXDOMAIN: self.nxdomain_responses[self.qname] = response # Make next_nameserver() return None, so caller breaks its # inner loop and calls next_request(). if self.resolver.cache: answer = Answer(self.qname, dns.rdatatype.ANY, dns.rdataclass.IN, response) self.resolver.cache.put((self.qname, dns.rdatatype.ANY, self.rdclass), answer) return (None, True) elif rcode == dns.rcode.YXDOMAIN: yex = YXDOMAIN() self.errors.append((self.nameserver, self.tcp_attempt, self.port, yex, response)) raise yex else: # # We got a response, but we're not happy with the # rcode in it. # if rcode != dns.rcode.SERVFAIL or not self.resolver.retry_servfail: self.nameservers.remove(self.nameserver) self.errors.append((self.nameserver, self.tcp_attempt, self.port, dns.rcode.to_text(rcode), response)) return (None, False) class Resolver: """DNS stub resolver.""" # We initialize in reset() # # pylint: disable=attribute-defined-outside-init def __init__(self, filename='/etc/resolv.conf', configure=True): """*filename*, a ``str`` 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.reset() if configure: if sys.platform == 'win32': self.read_registry() # pragma: no cover 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.use_search_by_default = False self.timeout = 2.0 self.lifetime = 5.0 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 self.ndots = None def read_resolv_conf(self, f): """Process *f* as a file in the /etc/resolv.conf format. If f is a ``str``, it is used as the name of the file to open; otherwise it is treated as the file itself. Interprets the following items: - nameserver - name server IP address - domain - local domain name - search - search list for host-name lookup - options - supported options are rotate, timeout, edns0, and ndots """ with contextlib.ExitStack() as stack: if isinstance(f, str): try: f = stack.enter_context(open(f)) except OSError: # /etc/resolv.conf doesn't exist, can't be read, etc. raise NoResolverConfiguration 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': for opt in tokens[1:]: if opt == 'rotate': self.rotate = True elif opt == 'edns0': self.use_edns(0, 0, 0) elif 'timeout' in opt: try: self.timeout = int(opt.split(':')[1]) except (ValueError, IndexError): pass elif 'ndots' in opt: try: self.ndots = int(opt.split(':')[1]) except (ValueError, IndexError): pass if len(self.nameservers) == 0: raise NoResolverConfiguration 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: # pragma: no cover split_char = ' ' elif entry.find(',') >= 0: # pragma: no cover 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): # pragma: no cover # 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): # pragma: no cover # 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: # pragma: no cover pass else: try: servers, rtype = winreg.QueryValueEx(key, 'DhcpNameServer') except WindowsError: # pragma: no cover servers = None if servers: # pragma: no cover self._config_win32_nameservers(servers) try: dom, rtype = winreg.QueryValueEx(key, 'DhcpDomain') if dom: # pragma: no cover self._config_win32_domain(dom) except WindowsError: # pragma: no cover pass try: search, rtype = winreg.QueryValueEx(key, 'SearchList') except WindowsError: # pylint: disable=undefined-variable search = None if search: # pragma: no cover self._config_win32_search(search) def read_registry(self): """Extract resolver configuration from the Windows registry.""" lm = winreg.ConnectRegistry(None, winreg.HKEY_LOCAL_MACHINE) try: tcp_params = winreg.OpenKey(lm, r'SYSTEM\CurrentControlSet' r'\Services\Tcpip\Parameters') try: self._config_win32_fromkey(tcp_params, True) finally: tcp_params.Close() 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: # pragma: no cover 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: # pragma: no cover 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: # pragma: no cover 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 Exception: # pragma: no cover 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 _get_qnames_to_try(self, qname, search): # This is a separate method so we can unit test the search # rules without requiring the Internet. if search is None: search = self.use_search_by_default qnames_to_try = [] if qname.is_absolute(): qnames_to_try.append(qname) else: if len(qname) > 1 or not search: qnames_to_try.append(qname.concatenate(dns.name.root)) if search and self.search: for suffix in self.search: if self.ndots is None or len(qname.labels) >= self.ndots: qnames_to_try.append(qname.concatenate(suffix)) elif search: qnames_to_try.append(qname.concatenate(self.domain)) return qnames_to_try def resolve(self, qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, raise_on_no_answer=True, source_port=0, lifetime=None, search=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 ``str``, the query name. *rdtype*, an ``int`` or ``str``, the query type. *rdclass*, an ``int`` or ``str``, the query class. *tcp*, a ``bool``. If ``True``, use TCP to make the query. *source*, a ``str`` 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 many seconds a query should run before timing out. *search*, a ``bool`` or ``None``, determines whether the search list configured in the system's resolver configuration are used for relative names, and whether the resolver's domain may be added to relative names. The default is ``None``, which causes the value of the resolver's ``use_search_by_default`` attribute to be used. 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. """ resolution = _Resolution(self, qname, rdtype, rdclass, tcp, raise_on_no_answer, search) start = time.time() while True: (request, answer) = resolution.next_request() # Note we need to say "if answer is not None" and not just # "if answer" because answer implements __len__, and python # will call that. We want to return if we have an answer # object, including in cases where its length is 0. if answer is not None: # cache hit! return answer done = False while not done: (nameserver, port, tcp, backoff) = resolution.next_nameserver() if backoff: time.sleep(backoff) timeout = self._compute_timeout(start, lifetime) try: if dns.inet.is_address(nameserver): if tcp: response = dns.query.tcp(request, nameserver, timeout=timeout, port=port, source=source, source_port=source_port) else: response = dns.query.udp(request, nameserver, timeout=timeout, port=port, source=source, source_port=source_port, raise_on_truncation=True) else: protocol = urlparse(nameserver).scheme if protocol != 'https': raise NotImplementedError response = dns.query.https(request, nameserver, timeout=timeout) except Exception as ex: (_, done) = resolution.query_result(None, ex) continue (answer, done) = resolution.query_result(response, None) # Note we need to say "if answer is not None" and not just # "if answer" because answer implements __len__, and python # will call that. We want to return if we have an answer # object, including in cases where its length is 0. if answer is not None: return answer 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): # pragma: no cover """Query nameservers to find the answer to the question. This method calls resolve() with ``search=True``, and is provided for backwards compatbility with prior versions of dnspython. See the documentation for the resolve() method for further details. """ warnings.warn('please use dns.resolver.Resolver.resolve() instead', DeprecationWarning, stacklevel=2) return self.resolve(qname, rdtype, rdclass, tcp, source, raise_on_no_answer, source_port, lifetime, True) def resolve_address(self, ipaddr, *args, **kwargs): """Use a resolver to run a reverse query for PTR records. This utilizes the resolve() method to perform a PTR lookup on the specified IP address. *ipaddr*, a ``str``, the IPv4 or IPv6 address you want to get the PTR record for. All other arguments that can be passed to the resolve() function except for rdtype and rdclass are also supported by this function. """ return self.resolve(dns.reversename.from_address(ipaddr), rdtype=dns.rdatatype.PTR, rdclass=dns.rdataclass.IN, *args, **kwargs) def use_tsig(self, keyring, keyname=None, algorithm=dns.tsig.default_algorithm): """Add a TSIG signature to each query. The parameters are passed to ``dns.message.Message.use_tsig()``; see its documentation for details. """ self.keyring = keyring 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 @property def nameservers(self): return self._nameservers @nameservers.setter def nameservers(self, nameservers): """ *nameservers*, a ``list`` of nameservers. Raises ``ValueError`` if *nameservers* is anything other than a ``list``. """ if isinstance(nameservers, list): self._nameservers = nameservers else: raise ValueError('nameservers must be a list' ' (not a {})'.format(type(nameservers))) #: 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 resolve(qname, rdtype=dns.rdatatype.A, rdclass=dns.rdataclass.IN, tcp=False, source=None, raise_on_no_answer=True, source_port=0, lifetime=None, search=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.resolve`` for more information on the parameters. """ return get_default_resolver().resolve(qname, rdtype, rdclass, tcp, source, raise_on_no_answer, source_port, lifetime, search) 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): # pragma: no cover """Query nameservers to find the answer to the question. This method calls resolve() with ``search=True``, and is provided for backwards compatbility with prior versions of dnspython. See the documentation for the resolve() method for further details. """ warnings.warn('please use dns.resolver.resolve() instead', DeprecationWarning, stacklevel=2) return resolve(qname, rdtype, rdclass, tcp, source, raise_on_no_answer, source_port, lifetime, True) def resolve_address(ipaddr, *args, **kwargs): """Use a resolver to run a reverse query for PTR records. See ``dns.resolver.Resolver.resolve_address`` for more information on the parameters. """ return get_default_resolver().resolve_address(ipaddr, *args, **kwargs) 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 ``str``, 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, str): 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.resolve(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_NUMERICHOST != 0: # Short circuit directly into the system's getaddrinfo(). We're # not adding any value in this case, and this avoids infinite loops # because dns.query.* needs to call getaddrinfo() for IPv6 scoping # reasons. We will also do this short circuit below if we # discover that the host is an address literal. return _original_getaddrinfo(host, service, family, socktype, proto, flags) if flags & (socket.AI_ADDRCONFIG | socket.AI_V4MAPPED) != 0: # Not implemented. We raise a gaierror as opposed to a # NotImplementedError as it helps callers handle errors more # appropriately. [Issue #316] # # We raise EAI_FAIL as opposed to EAI_SYSTEM because there is # no EAI_SYSTEM on Windows [Issue #416]. We didn't go for # EAI_BADFLAGS as the flags aren't bad, we just don't # implement them. raise socket.gaierror(socket.EAI_FAIL, 'Non-recoverable failure in name resolution') if host is None and service is None: raise socket.gaierror(socket.EAI_NONAME, 'Name or service not known') v6addrs = [] v4addrs = [] canonical_name = None # Is host None or an address literal? If so, use the system's # getaddrinfo(). if host is None: return _original_getaddrinfo(host, service, family, socktype, proto, flags) try: # We don't care about the result of af_for_address(), we're just # calling it so it raises an exception if host is not an IPv4 or # IPv6 address. dns.inet.af_for_address(host) return _original_getaddrinfo(host, service, family, socktype, proto, flags) except Exception: pass # Something needs resolution! try: if family == socket.AF_INET6 or family == socket.AF_UNSPEC: v6 = _resolver.resolve(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.resolve(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, 'Name or service not known') except Exception as e: print(e) # We raise EAI_AGAIN here as the failure may be temporary # (e.g. a timeout) and EAI_SYSTEM isn't defined on Windows. # [Issue #416] raise socket.gaierror(socket.EAI_AGAIN, 'Temporary failure in name resolution') 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, 'Name or service not known') 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, 'Name or service not known') 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.resolve(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, 'Name or service not known') 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: (name, _, _) = _gethostbyaddr(name) # Python's version checks aliases too, but our gethostbyname # ignores them, so we do so here as well. except Exception: pass 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: try: dns.ipv4.inet_aton(ip) except Exception: raise socket.gaierror(socket.EAI_NONAME, 'Name or service not known') 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] # We only want to include an address from the tuples if it's the # same as the one we asked about. We do this comparison in binary # to avoid any differences in text representations. bin_ip = dns.inet.inet_pton(family, ip) for item in tuples: addr = item[4][0] bin_addr = dns.inet.inet_pton(family, addr) if bin_ip == bin_addr: addresses.append(addr) # 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