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bazarr/libs/dns/resolver.py

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update deps
2018-10-31 16:08:29 +00:00
# Copyright (C) 2003-2007, 2009-2011 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.
@var default_resolver: The default resolver object
@type default_resolver: dns.resolver.Resolver object"""
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 = set(['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 = self.__doc__[:-1]
qnames = ', '.join(map(str, qnames))
return "%s: %s" % (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)
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 = set(['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 = set(['request', 'errors'])
def _fmt_kwargs(self, **kwargs):
srv_msgs = []
for err in kwargs['errors']:
srv_msgs.append('Server %s %s port %s answered %s' % (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. 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
node's name might not be the query name.
@ivar qname: The query name
@type qname: dns.name.Name object
@ivar rdtype: The query type
@type rdtype: int
@ivar rdclass: The query class
@type rdclass: int
@ivar response: The response message
@type response: dns.message.Message object
@ivar rrset: The answer
@type rrset: dns.rrset.RRset object
@ivar expiration: The time when the answer expires
@type expiration: float (seconds since the epoch)
@ivar canonical_name: The canonical name of the query name
@type canonical_name: dns.name.Name object
"""
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):
return self.rrset[i]
def __delitem__(self, i):
del self.rrset[i]
class Cache(object):
"""Simple DNS answer cache.
@ivar data: A dictionary of cached data
@type data: dict
@ivar cleaning_interval: The number of seconds between cleanings. The
default is 300 (5 minutes).
@type cleaning_interval: float
@ivar next_cleaning: The time the cache should next be cleaned (in seconds
since the epoch.)
@type next_cleaning: float
"""
def __init__(self, cleaning_interval=300.0):
"""Initialize a DNS cache.
@param cleaning_interval: the number of seconds between periodic
cleanings. The default is 300.0
@type cleaning_interval: float.
"""
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 I{key}. Returns None if
no answer is cached for the key.
@param key: the key
@type key: (dns.name.Name, int, int) tuple whose values are the
query name, rdtype, and rdclass.
@rtype: dns.resolver.Answer object 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.
@param key: the key
@type key: (dns.name.Name, int, int) tuple whose values are the
query name, rdtype, and rdclass.
@param value: The answer being cached
@type value: dns.resolver.Answer object
"""
try:
self.lock.acquire()
self._maybe_clean()
self.data[key] = value
finally:
self.lock.release()
def flush(self, key=None):
"""Flush the cache.
If I{key} is specified, only that item is flushed. Otherwise
the entire cache is flushed.
@param key: the key to flush
@type key: (dns.name.Name, int, int) tuple or None
"""
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):
"""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.
@ivar data: A dictionary of cached data
@type data: dict
@ivar sentinel: sentinel node for circular doubly linked list of nodes
@type sentinel: LRUCacheNode object
@ivar max_size: The maximum number of nodes
@type max_size: int
"""
def __init__(self, max_size=100000):
"""Initialize a DNS cache.
@param max_size: The maximum number of nodes to cache; the default is
100,000. Must be greater than 1.
@type max_size: int
"""
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 I{key}. Returns None if
no answer is cached for the key.
@param key: the key
@type key: (dns.name.Name, int, int) tuple whose values are the
query name, rdtype, and rdclass.
@rtype: dns.resolver.Answer object 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.
@param key: the key
@type key: (dns.name.Name, int, int) tuple whose values are the
query name, rdtype, and rdclass.
@param value: The answer being cached
@type value: dns.resolver.Answer object
"""
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 I{key} is specified, only that item is flushed. Otherwise
the entire cache is flushed.
@param key: the key to flush
@type key: (dns.name.Name, int, int) tuple or None
"""
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
@ivar domain: The domain of this host
@type domain: dns.name.Name object
@ivar nameservers: A list of nameservers to query. Each nameserver is
a string which contains the IP address of a nameserver.
@type nameservers: list of strings
@ivar search: The search list. If the query name is a relative name,
the resolver will construct an absolute query name by appending the search
names one by one to the query name.
@type search: list of dns.name.Name objects
@ivar port: The port to which to send queries. The default is 53.
@type port: int
@ivar timeout: The number of seconds to wait for a response from a
server, before timing out.
@type timeout: float
@ivar lifetime: The total number of seconds to spend trying to get an
answer to the question. If the lifetime expires, a Timeout exception
will occur.
@type lifetime: float
@ivar keyring: The TSIG keyring to use. The default is None.
@type keyring: dict
@ivar keyname: The TSIG keyname to use. The default is None.
@type keyname: dns.name.Name object
@ivar keyalgorithm: The TSIG key algorithm to use. The default is
dns.tsig.default_algorithm.
@type keyalgorithm: string
@ivar edns: The EDNS level to use. The default is -1, no Edns.
@type edns: int
@ivar ednsflags: The EDNS flags
@type ednsflags: int
@ivar payload: The EDNS payload size. The default is 0.
@type payload: int
@ivar flags: The message flags to use. The default is None (i.e. not
overwritten)
@type flags: int
@ivar cache: The cache to use. The default is None.
@type cache: dns.resolver.Cache object
@ivar retry_servfail: should we retry a nameserver if it says SERVFAIL?
The default is 'false'.
@type retry_servfail: bool
"""
def __init__(self, filename='/etc/resolv.conf', configure=True):
"""Initialize a resolver instance.
@param filename: The filename of a configuration file in
standard /etc/resolv.conf format. This parameter is meaningful
only when I{configure} is true and the platform is POSIX.
@type filename: string or file object
@param configure: If True (the default), the resolver instance
is configured in the normal fashion for the operating system
the resolver is running on. (I.e. a /etc/resolv.conf file on
POSIX systems and from the registry on Windows systems.)
@type configure: bool"""
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 string, 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):
"""Configure a NameServer registry entry."""
# 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):
"""Configure a Domain registry entry."""
# 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):
"""Configure a Search registry entry."""
# 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):
"""Extract DNS info from a registry key."""
try:
servers, rtype = _winreg.QueryValueEx(key, 'NameServer')
except WindowsError: # pylint: disable=undefined-variable
servers = None
if servers:
self._config_win32_nameservers(servers)
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)
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)
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):
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 >= self.lifetime:
raise Timeout(timeout=duration)
return min(self.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):
"""Query nameservers to find the answer to the question.
The I{qname}, I{rdtype}, and I{rdclass} parameters may be objects
of the appropriate type, or strings that can be converted into objects
of the appropriate type. E.g. For I{rdtype} the integer 2 and the
the string 'NS' both mean to query for records with DNS rdata type NS.
@param qname: the query name
@type qname: dns.name.Name object or string
@param rdtype: the query type
@type rdtype: int or string
@param rdclass: the query class
@type rdclass: int or string
@param tcp: use TCP to make the query (default is False).
@type tcp: bool
@param source: bind to this IP address (defaults to machine default
IP).
@type source: IP address in dotted quad notation
@param raise_on_no_answer: raise NoAnswer if there's no answer
(defaults is True).
@type raise_on_no_answer: bool
@param source_port: The port from which to send the message.
The default is 0.
@type source_port: int
@rtype: dns.resolver.Answer instance
@raises Timeout: no answers could be found in the specified lifetime
@raises NXDOMAIN: the query name does not exist
@raises YXDOMAIN: the query name is too long after DNAME substitution
@raises NoAnswer: the response did not contain an answer and
raise_on_no_answer is True.
@raises NoNameservers: no non-broken nameservers are available to
answer the question."""
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)
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)
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)
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.
@param keyring: The TSIG keyring to use; defaults to None.
@type keyring: dict
@param keyname: The name of the TSIG key to use; defaults to None.
The key must be defined in the keyring. 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.
@param algorithm: The TSIG key algorithm to use. The default
is dns.tsig.default_algorithm.
@type algorithm: string"""
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.
@param edns: The EDNS level to use. The default is -1, no Edns.
@type edns: int
@param ednsflags: The EDNS flags
@type ednsflags: int
@param payload: The EDNS payload size. The default is 0.
@type payload: int"""
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
@param flags: The flags to overwrite the default with
@type flags: int"""
self.flags = flags
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.
resolv.conf will be re-read immediatelly.
"""
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):
"""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: L{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)
def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False, resolver=None):
"""Find the name of the zone which contains the specified name.
@param name: the query name
@type name: absolute dns.name.Name object or string
@param rdclass: The query class
@type rdclass: int
@param tcp: use TCP to make the query (default is False).
@type tcp: bool
@param resolver: the resolver to use
@type resolver: dns.resolver.Resolver object or None
@rtype: 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:
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.
@param resolver: the resolver to use
@type resolver: dns.resolver.Resolver object or None
"""
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 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