374 lines
12 KiB
Python
374 lines
12 KiB
Python
# Copyright 2014 Hewlett-Packard Development Company, L.P.
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#
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# Author: Endre Karlson <endre.karlson@hpe.com>
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import random
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import socket
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import base64
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import time
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from threading import Lock
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import six
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import dns
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import dns.exception
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import dns.zone
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import eventlet
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from dns import rdatatype
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from oslo_log import log as logging
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from oslo_config import cfg
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from designate import context
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from designate import exceptions
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from designate import objects
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LOG = logging.getLogger(__name__)
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util_opts = [
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cfg.IntOpt('xfr_timeout', help="Timeout in seconds for XFR's.", default=10)
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]
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cfg.CONF.register_opts(util_opts)
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class DNSMiddleware(object):
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"""Base DNS Middleware class with some utility methods"""
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def __init__(self, application):
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self.application = application
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def process_request(self, request):
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"""Called on each request.
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If this returns None, the next application down the stack will be
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executed. If it returns a response then that response will be returned
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and execution will stop here.
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"""
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return None
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def process_response(self, response):
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"""Do whatever you'd like to the response."""
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return response
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def __call__(self, request):
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response = self.process_request(request)
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if response:
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return response
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response = self.application(request)
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return self.process_response(response)
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def _build_error_response(self):
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response = dns.message.make_response(
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dns.message.make_query('unknown', dns.rdatatype.A))
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response.set_rcode(dns.rcode.FORMERR)
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return response
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class SerializationMiddleware(DNSMiddleware):
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"""DNS Middleware to serialize/deserialize DNS Packets"""
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def __init__(self, application, tsig_keyring=None):
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self.application = application
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self.tsig_keyring = tsig_keyring
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def __call__(self, request):
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# Generate the initial context. This may be updated by other middleware
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# as we learn more information about the Request.
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ctxt = context.DesignateContext.get_admin_context(all_tenants=True)
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try:
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message = dns.message.from_wire(request['payload'],
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self.tsig_keyring)
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if message.had_tsig:
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LOG.debug('Request signed with TSIG key: %s', message.keyname)
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# Create + Attach the initial "environ" dict. This is similar to
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# the environ dict used in typical WSGI middleware.
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message.environ = {
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'context': ctxt,
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'addr': request['addr'],
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}
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except dns.message.UnknownTSIGKey:
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LOG.error("Unknown TSIG key from %(host)s:%(port)d",
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{'host': request['addr'][0], 'port': request['addr'][1]})
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response = self._build_error_response()
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except dns.tsig.BadSignature:
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LOG.error("Invalid TSIG signature from %(host)s:%(port)d",
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{'host': request['addr'][0], 'port': request['addr'][1]})
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response = self._build_error_response()
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except dns.exception.DNSException:
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LOG.error("Failed to deserialize packet from %(host)s:%(port)d",
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{'host': request['addr'][0], 'port': request['addr'][1]})
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response = self._build_error_response()
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except Exception:
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LOG.exception("Unknown exception deserializing packet "
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"from %(host)s %(port)d",
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{'host': request['addr'][0],
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'port': request['addr'][1]})
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response = self._build_error_response()
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else:
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# Hand the Deserialized packet onto the Application
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for response in self.application(message):
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# Serialize and return the response if present
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if isinstance(response, dns.message.Message):
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yield response.to_wire(max_size=65535)
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elif isinstance(response, dns.renderer.Renderer):
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yield response.get_wire()
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else:
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LOG.error("Unexpected response %r", response)
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class TsigInfoMiddleware(DNSMiddleware):
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"""Middleware which looks up the information available for a TsigKey"""
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def __init__(self, application, storage):
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super(TsigInfoMiddleware, self).__init__(application)
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self.storage = storage
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def process_request(self, request):
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if not request.had_tsig:
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return None
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try:
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criterion = {'name': request.keyname.to_text(True).decode('utf-8')}
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tsigkey = self.storage.find_tsigkey(
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context.get_current(), criterion)
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request.environ['tsigkey'] = tsigkey
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request.environ['context'].tsigkey_id = tsigkey.id
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except exceptions.TsigKeyNotFound:
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# This should never happen, as we just validated the key.. Except
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# for race conditions..
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return self._build_error_response()
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return None
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class TsigKeyring(object):
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"""Implements the DNSPython KeyRing API, backed by the Designate DB"""
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def __init__(self, storage):
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self.storage = storage
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def __getitem__(self, key):
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return self.get(key)
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def get(self, key, default=None):
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try:
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criterion = {'name': key.to_text(True).decode('utf-8')}
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tsigkey = self.storage.find_tsigkey(
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context.get_current(), criterion)
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return base64.decodestring(tsigkey.secret)
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except exceptions.TsigKeyNotFound:
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return default
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class ZoneLock(object):
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"""A Lock across all zones that enforces a rate limit on NOTIFYs"""
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def __init__(self, delay):
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self.lock = Lock()
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self.data = {}
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self.delay = delay
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def acquire(self, zone):
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with self.lock:
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# If no one holds the lock for the zone, grant it
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if zone not in self.data:
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self.data[zone] = time.time()
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return True
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# Otherwise, get the time that it was locked
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locktime = self.data[zone]
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now = time.time()
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period = now - locktime
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# If it has been locked for longer than the allowed period
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# give the lock to the new requester
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if period > self.delay:
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self.data[zone] = now
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return True
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LOG.debug('Lock for %(zone)s can\'t be released for %(period)s'
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'seconds' % {'zone': zone,
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'period': str(self.delay - period)})
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# Don't grant the lock for the zone
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return False
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def release(self, zone):
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# Release the lock
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with self.lock:
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try:
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self.data.pop(zone)
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except KeyError:
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pass
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class LimitNotifyMiddleware(DNSMiddleware):
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"""Middleware that rate limits NOTIFYs to the Agent"""
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def __init__(self, application):
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super(LimitNotifyMiddleware, self).__init__(application)
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self.delay = cfg.CONF['service:agent'].notify_delay
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self.locker = ZoneLock(self.delay)
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def process_request(self, request):
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opcode = request.opcode()
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if opcode != dns.opcode.NOTIFY:
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return None
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zone_name = request.question[0].name.to_text().decode('utf-8')
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if self.locker.acquire(zone_name):
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time.sleep(self.delay)
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self.locker.release(zone_name)
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return None
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else:
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LOG.debug('Threw away NOTIFY for %(zone)s, already '
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'working on an update.' % {'zone': zone_name})
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response = dns.message.make_response(request)
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# Provide an authoritative answer
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response.flags |= dns.flags.AA
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return (response,)
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def from_dnspython_zone(dnspython_zone):
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# dnspython never builds a zone with more than one SOA, even if we give
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# it a zonefile that contains more than one
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soa = dnspython_zone.get_rdataset(dnspython_zone.origin, 'SOA')
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if soa is None:
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raise exceptions.BadRequest('An SOA record is required')
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if soa.ttl == 0:
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soa.ttl = cfg.CONF['service:central'].min_ttl
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email = soa[0].rname.to_text(omit_final_dot=True).decode('utf-8')
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email = email.replace('.', '@', 1)
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values = {
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'name': dnspython_zone.origin.to_text().decode('utf-8'),
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'email': email,
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'ttl': soa.ttl,
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'serial': soa[0].serial,
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'retry': soa[0].retry,
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'expire': soa[0].expire
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}
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zone = objects.Zone(**values)
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rrsets = dnspyrecords_to_recordsetlist(dnspython_zone.nodes)
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zone.recordsets = rrsets
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return zone
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def dnspyrecords_to_recordsetlist(dnspython_records):
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rrsets = objects.RecordSetList()
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for rname in six.iterkeys(dnspython_records):
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for rdataset in dnspython_records[rname]:
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rrset = dnspythonrecord_to_recordset(rname, rdataset)
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if rrset is None:
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continue
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rrsets.append(rrset)
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return rrsets
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def dnspythonrecord_to_recordset(rname, rdataset):
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record_type = rdatatype.to_text(rdataset.rdtype)
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# Create the other recordsets
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values = {
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'name': rname.to_text().decode('utf-8'),
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'type': record_type
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}
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if rdataset.ttl != 0:
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values['ttl'] = rdataset.ttl
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rrset = objects.RecordSet(**values)
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rrset.records = objects.RecordList()
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for rdata in rdataset:
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rr = objects.Record(data=rdata.to_text())
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rrset.records.append(rr)
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return rrset
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def do_axfr(zone_name, servers, timeout=None, source=None):
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"""
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Requests an AXFR for a given zone name and process the response
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:returns: Zone instance from dnspython
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"""
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random.shuffle(servers)
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timeout = timeout or cfg.CONF["service:mdns"].xfr_timeout
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xfr = None
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for srv in servers:
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to = eventlet.Timeout(timeout)
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log_info = {'name': zone_name, 'host': srv}
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try:
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LOG.info("Doing AXFR for %(name)s from %(host)s", log_info)
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xfr = dns.query.xfr(srv['host'], zone_name, relativize=False,
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timeout=1, port=srv['port'], source=source)
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raw_zone = dns.zone.from_xfr(xfr, relativize=False)
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break
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except eventlet.Timeout as t:
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if t == to:
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LOG.error("AXFR timed out for %(name)s from %(host)s",
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log_info)
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continue
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except dns.exception.FormError:
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LOG.error("Zone %(name)s is not present on %(host)s."
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"Trying next server.", log_info)
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except socket.error:
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LOG.error("Connection error when doing AXFR for %(name)s from "
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"%(host)s", log_info)
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except Exception:
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LOG.exception("Problem doing AXFR %(name)s from %(host)s. "
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"Trying next server.", log_info)
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finally:
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to.cancel()
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continue
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else:
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raise exceptions.XFRFailure(
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"XFR failed for %(name)s. No servers in %(servers)s was reached." %
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{"name": zone_name, "servers": servers})
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LOG.debug("AXFR Successful for %s", raw_zone.origin.to_text())
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return raw_zone
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