307 lines
10 KiB
Python
307 lines
10 KiB
Python
# -*- encoding: utf-8 -*-
|
|
|
|
"""
|
|
sleekxmpp.xmlstream.dns
|
|
~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
:copyright: (c) 2012 Nathanael C. Fritz
|
|
:license: MIT, see LICENSE for more details
|
|
"""
|
|
|
|
import socket
|
|
import logging
|
|
import random
|
|
|
|
|
|
log = logging.getLogger(__name__)
|
|
|
|
|
|
#: Global flag indicating the availability of the ``dnspython`` package.
|
|
#: Installing ``dnspython`` can be done via:
|
|
#:
|
|
#: .. code-block:: sh
|
|
#:
|
|
#: pip install dnspython
|
|
#:
|
|
#: For Python3, installation may require installing from source using
|
|
#: the ``python3`` branch:
|
|
#:
|
|
#: .. code-block:: sh
|
|
#:
|
|
#: git clone http://github.com/rthalley/dnspython
|
|
#: cd dnspython
|
|
#: git checkout python3
|
|
#: python3 setup.py install
|
|
USE_DNSPYTHON = False
|
|
try:
|
|
import dns.resolver
|
|
USE_DNSPYTHON = True
|
|
except ImportError as e:
|
|
log.debug("Could not find dnspython package. " + \
|
|
"Not all features will be available")
|
|
|
|
|
|
def default_resolver():
|
|
"""Return a basic DNS resolver object.
|
|
|
|
:returns: A :class:`dns.resolver.Resolver` object if dnspython
|
|
is available. Otherwise, ``None``.
|
|
"""
|
|
if USE_DNSPYTHON:
|
|
return dns.resolver.get_default_resolver()
|
|
return None
|
|
|
|
|
|
def resolve(host, port=None, service=None, proto='tcp',
|
|
resolver=None, use_ipv6=True):
|
|
"""Peform DNS resolution for a given hostname.
|
|
|
|
Resolution may perform SRV record lookups if a service and protocol
|
|
are specified. The returned addresses will be sorted according to
|
|
the SRV priorities and weights.
|
|
|
|
If no resolver is provided, the dnspython resolver will be used if
|
|
available. Otherwise the built-in socket facilities will be used,
|
|
but those do not provide SRV support.
|
|
|
|
If SRV records were used, queries to resolve alternative hosts will
|
|
be made as needed instead of all at once.
|
|
|
|
:param host: The hostname to resolve.
|
|
:param port: A default port to connect with. SRV records may
|
|
dictate use of a different port.
|
|
:param service: Optional SRV service name without leading underscore.
|
|
:param proto: Optional SRV protocol name without leading underscore.
|
|
:param resolver: Optionally provide a DNS resolver object that has
|
|
been custom configured.
|
|
:param use_ipv6: Optionally control the use of IPv6 in situations
|
|
where it is either not available, or performance
|
|
is degraded. Defaults to ``True``.
|
|
|
|
:type host: string
|
|
:type port: int
|
|
:type service: string
|
|
:type proto: string
|
|
:type resolver: :class:`dns.resolver.Resolver`
|
|
:type use_ipv6: bool
|
|
|
|
:return: An iterable of IP address, port pairs in the order
|
|
dictated by SRV priorities and weights, if applicable.
|
|
"""
|
|
if not use_ipv6:
|
|
log.debug("DNS: Use of IPv6 has been disabled.")
|
|
|
|
if resolver is None and USE_DNSPYTHON:
|
|
resolver = dns.resolver.get_default_resolver()
|
|
|
|
# An IPv6 literal is allowed to be enclosed in square brackets, but
|
|
# the brackets must be stripped in order to process the literal;
|
|
# otherwise, things break.
|
|
host = host.strip('[]')
|
|
|
|
try:
|
|
# If `host` is an IPv4 literal, we can return it immediately.
|
|
ipv4 = socket.inet_aton(host)
|
|
yield (host, host, port)
|
|
except socket.error:
|
|
pass
|
|
|
|
if use_ipv6:
|
|
try:
|
|
# Likewise, If `host` is an IPv6 literal, we can return
|
|
# it immediately.
|
|
if hasattr(socket, 'inet_pton'):
|
|
ipv6 = socket.inet_pton(socket.AF_INET6, host)
|
|
yield (host, host, port)
|
|
except (socket.error, ValueError):
|
|
pass
|
|
|
|
# If no service was provided, then we can just do A/AAAA lookups on the
|
|
# provided host. Otherwise we need to get an ordered list of hosts to
|
|
# resolve based on SRV records.
|
|
if not service:
|
|
hosts = [(host, port)]
|
|
else:
|
|
hosts = get_SRV(host, port, service, proto, resolver=resolver)
|
|
|
|
for host, port in hosts:
|
|
results = []
|
|
if host == 'localhost':
|
|
if use_ipv6:
|
|
results.append((host, '::1', port))
|
|
results.append((host, '127.0.0.1', port))
|
|
if use_ipv6:
|
|
for address in get_AAAA(host, resolver=resolver):
|
|
results.append((host, address, port))
|
|
for address in get_A(host, resolver=resolver):
|
|
results.append((host, address, port))
|
|
|
|
for host, address, port in results:
|
|
yield host, address, port
|
|
|
|
|
|
def get_A(host, resolver=None):
|
|
"""Lookup DNS A records for a given host.
|
|
|
|
If ``resolver`` is not provided, or is ``None``, then resolution will
|
|
be performed using the built-in :mod:`socket` module.
|
|
|
|
:param host: The hostname to resolve for A record IPv4 addresses.
|
|
:param resolver: Optional DNS resolver object to use for the query.
|
|
|
|
:type host: string
|
|
:type resolver: :class:`dns.resolver.Resolver` or ``None``
|
|
|
|
:return: A list of IPv4 literals.
|
|
"""
|
|
log.debug("DNS: Querying %s for A records." % host)
|
|
|
|
# If not using dnspython, attempt lookup using the OS level
|
|
# getaddrinfo() method.
|
|
if resolver is None:
|
|
try:
|
|
recs = socket.getaddrinfo(host, None, socket.AF_INET,
|
|
socket.SOCK_STREAM)
|
|
return [rec[4][0] for rec in recs]
|
|
except socket.gaierror:
|
|
log.debug("DNS: Error retreiving A address info for %s." % host)
|
|
return []
|
|
|
|
# Using dnspython:
|
|
try:
|
|
recs = resolver.query(host, dns.rdatatype.A)
|
|
return [rec.to_text() for rec in recs]
|
|
except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
|
|
log.debug("DNS: No A records for %s" % host)
|
|
return []
|
|
except dns.exception.Timeout:
|
|
log.debug("DNS: A record resolution timed out for %s" % host)
|
|
return []
|
|
except dns.exception.DNSException as e:
|
|
log.debug("DNS: Error querying A records for %s" % host)
|
|
log.exception(e)
|
|
return []
|
|
|
|
|
|
def get_AAAA(host, resolver=None):
|
|
"""Lookup DNS AAAA records for a given host.
|
|
|
|
If ``resolver`` is not provided, or is ``None``, then resolution will
|
|
be performed using the built-in :mod:`socket` module.
|
|
|
|
:param host: The hostname to resolve for AAAA record IPv6 addresses.
|
|
:param resolver: Optional DNS resolver object to use for the query.
|
|
|
|
:type host: string
|
|
:type resolver: :class:`dns.resolver.Resolver` or ``None``
|
|
|
|
:return: A list of IPv6 literals.
|
|
"""
|
|
log.debug("DNS: Querying %s for AAAA records." % host)
|
|
|
|
# If not using dnspython, attempt lookup using the OS level
|
|
# getaddrinfo() method.
|
|
if resolver is None:
|
|
try:
|
|
recs = socket.getaddrinfo(host, None, socket.AF_INET6,
|
|
socket.SOCK_STREAM)
|
|
return [rec[4][0] for rec in recs]
|
|
except socket.gaierror:
|
|
log.debug("DNS: Error retreiving AAAA address " + \
|
|
"info for %s." % host)
|
|
return []
|
|
|
|
# Using dnspython:
|
|
try:
|
|
recs = resolver.query(host, dns.rdatatype.AAAA)
|
|
return [rec.to_text() for rec in recs]
|
|
except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
|
|
log.debug("DNS: No AAAA records for %s" % host)
|
|
return []
|
|
except dns.exception.Timeout:
|
|
log.debug("DNS: AAAA record resolution timed out for %s" % host)
|
|
return []
|
|
except dns.exception.DNSException as e:
|
|
log.debug("DNS: Error querying AAAA records for %s" % host)
|
|
log.exception(e)
|
|
return []
|
|
|
|
|
|
def get_SRV(host, port, service, proto='tcp', resolver=None):
|
|
"""Perform SRV record resolution for a given host.
|
|
|
|
.. note::
|
|
|
|
This function requires the use of the ``dnspython`` package. Calling
|
|
:func:`get_SRV` without ``dnspython`` will return the provided host
|
|
and port without performing any DNS queries.
|
|
|
|
:param host: The hostname to resolve.
|
|
:param port: A default port to connect with. SRV records may
|
|
dictate use of a different port.
|
|
:param service: Optional SRV service name without leading underscore.
|
|
:param proto: Optional SRV protocol name without leading underscore.
|
|
:param resolver: Optionally provide a DNS resolver object that has
|
|
been custom configured.
|
|
|
|
:type host: string
|
|
:type port: int
|
|
:type service: string
|
|
:type proto: string
|
|
:type resolver: :class:`dns.resolver.Resolver`
|
|
|
|
:return: A list of hostname, port pairs in the order dictacted
|
|
by SRV priorities and weights.
|
|
"""
|
|
if resolver is None:
|
|
log.warning("DNS: dnspython not found. Can not use SRV lookup.")
|
|
return [(host, port)]
|
|
|
|
log.debug("DNS: Querying SRV records for %s" % host)
|
|
try:
|
|
recs = resolver.query('_%s._%s.%s' % (service, proto, host),
|
|
dns.rdatatype.SRV)
|
|
except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
|
|
log.debug("DNS: No SRV records for %s." % host)
|
|
return [(host, port)]
|
|
except dns.exception.Timeout:
|
|
log.debug("DNS: SRV record resolution timed out for %s." % host)
|
|
return [(host, port)]
|
|
except dns.exception.DNSException as e:
|
|
log.debug("DNS: Error querying SRV records for %s." % host)
|
|
log.exception(e)
|
|
return [(host, port)]
|
|
|
|
if len(recs) == 1 and recs[0].target == '.':
|
|
return [(host, port)]
|
|
|
|
answers = {}
|
|
for rec in recs:
|
|
if rec.priority not in answers:
|
|
answers[rec.priority] = []
|
|
if rec.weight == 0:
|
|
answers[rec.priority].insert(0, rec)
|
|
else:
|
|
answers[rec.priority].append(rec)
|
|
|
|
sorted_recs = []
|
|
for priority in sorted(answers.keys()):
|
|
while answers[priority]:
|
|
running_sum = 0
|
|
sums = {}
|
|
for rec in answers[priority]:
|
|
running_sum += rec.weight
|
|
sums[running_sum] = rec
|
|
|
|
selected = random.randint(0, running_sum + 1)
|
|
for running_sum in sums:
|
|
if running_sum >= selected:
|
|
rec = sums[running_sum]
|
|
host = rec.target.to_text()
|
|
if host.endswith('.'):
|
|
host = host[:-1]
|
|
sorted_recs.append((host, rec.port))
|
|
answers[priority].remove(rec)
|
|
break
|
|
|
|
return sorted_recs
|