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# 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.
"""Talk to a DNS server."""
from __future__ import generators
import errno
import select
import socket
import struct
import sys
import time
import dns.exception
import dns.inet
import dns.name
import dns.message
import dns.rdataclass
import dns.rdatatype
from ._compat import long, string_types
if sys.version_info > (3,):
select_error = OSError
else:
select_error = select.error
# Function used to create a socket. Can be overridden if needed in special
# situations.
socket_factory = socket.socket
class UnexpectedSource(dns.exception.DNSException):
"""A DNS query response came from an unexpected address or port."""
class BadResponse(dns.exception.FormError):
"""A DNS query response does not respond to the question asked."""
def _compute_expiration(timeout):
if timeout is None:
return None
else:
return time.time() + timeout
def _poll_for(fd, readable, writable, error, timeout):
"""Poll polling backend.
@param fd: File descriptor
@type fd: int
@param readable: Whether to wait for readability
@type readable: bool
@param writable: Whether to wait for writability
@type writable: bool
@param timeout: Deadline timeout (expiration time, in seconds)
@type timeout: float
@return True on success, False on timeout
"""
event_mask = 0
if readable:
event_mask |= select.POLLIN
if writable:
event_mask |= select.POLLOUT
if error:
event_mask |= select.POLLERR
pollable = select.poll()
pollable.register(fd, event_mask)
if timeout:
event_list = pollable.poll(long(timeout * 1000))
else:
event_list = pollable.poll()
return bool(event_list)
def _select_for(fd, readable, writable, error, timeout):
"""Select polling backend.
@param fd: File descriptor
@type fd: int
@param readable: Whether to wait for readability
@type readable: bool
@param writable: Whether to wait for writability
@type writable: bool
@param timeout: Deadline timeout (expiration time, in seconds)
@type timeout: float
@return True on success, False on timeout
"""
rset, wset, xset = [], [], []
if readable:
rset = [fd]
if writable:
wset = [fd]
if error:
xset = [fd]
if timeout is None:
(rcount, wcount, xcount) = select.select(rset, wset, xset)
else:
(rcount, wcount, xcount) = select.select(rset, wset, xset, timeout)
return bool((rcount or wcount or xcount))
def _wait_for(fd, readable, writable, error, expiration):
done = False
while not done:
if expiration is None:
timeout = None
else:
timeout = expiration - time.time()
if timeout <= 0.0:
raise dns.exception.Timeout
try:
if not _polling_backend(fd, readable, writable, error, timeout):
raise dns.exception.Timeout
except select_error as e:
if e.args[0] != errno.EINTR:
raise e
done = True
def _set_polling_backend(fn):
"""
Internal API. Do not use.
"""
global _polling_backend
_polling_backend = fn
if hasattr(select, 'poll'):
# Prefer poll() on platforms that support it because it has no
# limits on the maximum value of a file descriptor (plus it will
# be more efficient for high values).
_polling_backend = _poll_for
else:
_polling_backend = _select_for
def _wait_for_readable(s, expiration):
_wait_for(s, True, False, True, expiration)
def _wait_for_writable(s, expiration):
_wait_for(s, False, True, True, expiration)
def _addresses_equal(af, a1, a2):
# Convert the first value of the tuple, which is a textual format
# address into binary form, so that we are not confused by different
# textual representations of the same address
n1 = dns.inet.inet_pton(af, a1[0])
n2 = dns.inet.inet_pton(af, a2[0])
return n1 == n2 and a1[1:] == a2[1:]
def _matches_destination(af, from_address, destination, ignore_unexpected):
# Check that from_address is appropriate for a response to a query
# sent to destination.
if not destination:
return True
if _addresses_equal(af, from_address, destination) or (
dns.inet.is_multicast(destination[0]) and from_address[1:] == destination[1:]
):
return True
elif ignore_unexpected:
return False
raise UnexpectedSource(
f"got a response from {from_address} instead of " f"{destination}"
)
def _destination_and_source(af, where, port, source, source_port):
# Apply defaults and compute destination and source tuples
# suitable for use in connect(), sendto(), or bind().
if af is None:
try:
af = dns.inet.af_for_address(where)
except Exception:
af = dns.inet.AF_INET
if af == dns.inet.AF_INET:
destination = (where, port)
if source is not None or source_port != 0:
if source is None:
source = '0.0.0.0'
source = (source, source_port)
elif af == dns.inet.AF_INET6:
destination = (where, port, 0, 0)
if source is not None or source_port != 0:
if source is None:
source = '::'
source = (source, source_port, 0, 0)
return (af, destination, source)
def udp(q, where, timeout=None, port=53, af=None, source=None, source_port=0,
ignore_unexpected=False, one_rr_per_rrset=False, ignore_errors=False):
"""Return the response obtained after sending a query via UDP.
@param q: the query
@type q: dns.message.Message
@param where: where to send the message
@type where: string containing an IPv4 or IPv6 address
@param timeout: The number of seconds to wait before the query times out.
If None, the default, wait forever.
@type timeout: float
@param port: The port to which to send the message. The default is 53.
@type port: int
@param af: the address family to use. The default is None, which
causes the address family to use to be inferred from the form of where.
If the inference attempt fails, AF_INET is used.
@type af: int
@rtype: dns.message.Message object
@param source: source address. The default is the wildcard address.
@type source: string
@param source_port: The port from which to send the message.
The default is 0.
@type source_port: int
@param ignore_unexpected: If True, ignore responses from unexpected
sources. The default is False.
@type ignore_unexpected: bool
@param one_rr_per_rrset: Put each RR into its own RRset
@type one_rr_per_rrset: bool
"""
wire = q.to_wire()
(af, destination, source) = _destination_and_source(af, where, port,
source, source_port)
s = socket_factory(af, socket.SOCK_DGRAM, 0)
begin_time = None
try:
expiration = _compute_expiration(timeout)
s.setblocking(0)
if source is not None:
s.bind(source)
_wait_for_writable(s, expiration)
begin_time = time.time()
s.sendto(wire, destination)
while 1:
_wait_for_readable(s, expiration)
(wire, from_address) = s.recvfrom(65535)
if not _matches_destination(
s.family, from_address, destination, ignore_unexpected
):
continue
response_time = time.time() - begin_time
try:
r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
one_rr_per_rrset=one_rr_per_rrset)
r.time = response_time
except Exception:
if ignore_errors:
continue
else:
raise
if q.is_response(r):
return r
else:
if ignore_errors:
continue
else:
raise BadResponse
finally:
s.close()
def _net_read(sock, count, expiration):
"""Read the specified number of bytes from sock. Keep trying until we
either get the desired amount, or we hit EOF.
A Timeout exception will be raised if the operation is not completed
by the expiration time.
"""
s = b''
while count > 0:
_wait_for_readable(sock, expiration)
n = sock.recv(count)
if n == b'':
raise EOFError
count = count - len(n)
s = s + n
return s
def _net_write(sock, data, expiration):
"""Write the specified data to the socket.
A Timeout exception will be raised if the operation is not completed
by the expiration time.
"""
current = 0
l = len(data)
while current < l:
_wait_for_writable(sock, expiration)
current += sock.send(data[current:])
def _connect(s, address):
try:
s.connect(address)
except socket.error:
(ty, v) = sys.exc_info()[:2]
if hasattr(v, 'errno'):
v_err = v.errno
else:
v_err = v[0]
if v_err not in [errno.EINPROGRESS, errno.EWOULDBLOCK, errno.EALREADY]:
raise v
def tcp(q, where, timeout=None, port=53, af=None, source=None, source_port=0,
one_rr_per_rrset=False):
"""Return the response obtained after sending a query via TCP.
@param q: the query
@type q: dns.message.Message object
@param where: where to send the message
@type where: string containing an IPv4 or IPv6 address
@param timeout: The number of seconds to wait before the query times out.
If None, the default, wait forever.
@type timeout: float
@param port: The port to which to send the message. The default is 53.
@type port: int
@param af: the address family to use. The default is None, which
causes the address family to use to be inferred from the form of where.
If the inference attempt fails, AF_INET is used.
@type af: int
@rtype: dns.message.Message object
@param source: source address. The default is the wildcard address.
@type source: string
@param source_port: The port from which to send the message.
The default is 0.
@type source_port: int
@param one_rr_per_rrset: Put each RR into its own RRset
@type one_rr_per_rrset: bool
"""
wire = q.to_wire()
(af, destination, source) = _destination_and_source(af, where, port,
source, source_port)
s = socket_factory(af, socket.SOCK_STREAM, 0)
begin_time = None
try:
expiration = _compute_expiration(timeout)
s.setblocking(0)
begin_time = time.time()
if source is not None:
s.bind(source)
_connect(s, destination)
l = len(wire)
# copying the wire into tcpmsg is inefficient, but lets us
# avoid writev() or doing a short write that would get pushed
# onto the net
tcpmsg = struct.pack("!H", l) + wire
_net_write(s, tcpmsg, expiration)
ldata = _net_read(s, 2, expiration)
(l,) = struct.unpack("!H", ldata)
wire = _net_read(s, l, expiration)
finally:
if begin_time is None:
response_time = 0
else:
response_time = time.time() - begin_time
s.close()
r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
one_rr_per_rrset=one_rr_per_rrset)
r.time = response_time
if not q.is_response(r):
raise BadResponse
return r
def xfr(where, zone, rdtype=dns.rdatatype.AXFR, rdclass=dns.rdataclass.IN,
timeout=None, port=53, keyring=None, keyname=None, relativize=True,
af=None, lifetime=None, source=None, source_port=0, serial=0,
use_udp=False, keyalgorithm=dns.tsig.default_algorithm):
"""Return a generator for the responses to a zone transfer.
@param where: where to send the message
@type where: string containing an IPv4 or IPv6 address
@param zone: The name of the zone to transfer
@type zone: dns.name.Name object or string
@param rdtype: The type of zone transfer. The default is
dns.rdatatype.AXFR.
@type rdtype: int or string
@param rdclass: The class of the zone transfer. The default is
dns.rdataclass.IN.
@type rdclass: int or string
@param timeout: The number of seconds to wait for each response message.
If None, the default, wait forever.
@type timeout: float
@param port: The port to which to send the message. The default is 53.
@type port: int
@param keyring: The TSIG keyring to use
@type keyring: dict
@param keyname: The name of the TSIG key to use
@type keyname: dns.name.Name object or string
@param relativize: If True, all names in the zone will be relativized to
the zone origin. It is essential that the relativize setting matches
the one specified to dns.zone.from_xfr().
@type relativize: bool
@param af: the address family to use. The default is None, which
causes the address family to use to be inferred from the form of where.
If the inference attempt fails, AF_INET is used.
@type af: int
@param lifetime: The total number of seconds to spend doing the transfer.
If None, the default, then there is no limit on the time the transfer may
take.
@type lifetime: float
@rtype: generator of dns.message.Message objects.
@param source: source address. The default is the wildcard address.
@type source: string
@param source_port: The port from which to send the message.
The default is 0.
@type source_port: int
@param serial: The SOA serial number to use as the base for an IXFR diff
sequence (only meaningful if rdtype == dns.rdatatype.IXFR).
@type serial: int
@param use_udp: Use UDP (only meaningful for IXFR)
@type use_udp: bool
@param keyalgorithm: The TSIG algorithm to use; defaults to
dns.tsig.default_algorithm
@type keyalgorithm: string
"""
if isinstance(zone, string_types):
zone = dns.name.from_text(zone)
if isinstance(rdtype, string_types):
rdtype = dns.rdatatype.from_text(rdtype)
q = dns.message.make_query(zone, rdtype, rdclass)
if rdtype == dns.rdatatype.IXFR:
rrset = dns.rrset.from_text(zone, 0, 'IN', 'SOA',
'. . %u 0 0 0 0' % serial)
q.authority.append(rrset)
if keyring is not None:
q.use_tsig(keyring, keyname, algorithm=keyalgorithm)
wire = q.to_wire()
(af, destination, source) = _destination_and_source(af, where, port,
source, source_port)
if use_udp:
if rdtype != dns.rdatatype.IXFR:
raise ValueError('cannot do a UDP AXFR')
s = socket_factory(af, socket.SOCK_DGRAM, 0)
else:
s = socket_factory(af, socket.SOCK_STREAM, 0)
s.setblocking(0)
if source is not None:
s.bind(source)
expiration = _compute_expiration(lifetime)
_connect(s, destination)
l = len(wire)
if use_udp:
_wait_for_writable(s, expiration)
s.send(wire)
else:
tcpmsg = struct.pack("!H", l) + wire
_net_write(s, tcpmsg, expiration)
done = False
delete_mode = True
expecting_SOA = False
soa_rrset = None
if relativize:
origin = zone
oname = dns.name.empty
else:
origin = None
oname = zone
tsig_ctx = None
first = True
while not done:
mexpiration = _compute_expiration(timeout)
if mexpiration is None or \
(expiration is not None and mexpiration > expiration):
mexpiration = expiration
if use_udp:
_wait_for_readable(s, expiration)
(wire, from_address) = s.recvfrom(65535)
else:
ldata = _net_read(s, 2, mexpiration)
(l,) = struct.unpack("!H", ldata)
wire = _net_read(s, l, mexpiration)
is_ixfr = (rdtype == dns.rdatatype.IXFR)
r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
xfr=True, origin=origin, tsig_ctx=tsig_ctx,
multi=True, first=first,
one_rr_per_rrset=is_ixfr)
tsig_ctx = r.tsig_ctx
first = False
answer_index = 0
if soa_rrset is None:
if not r.answer or r.answer[0].name != oname:
raise dns.exception.FormError(
"No answer or RRset not for qname")
rrset = r.answer[0]
if rrset.rdtype != dns.rdatatype.SOA:
raise dns.exception.FormError("first RRset is not an SOA")
answer_index = 1
soa_rrset = rrset.copy()
if rdtype == dns.rdatatype.IXFR:
if soa_rrset[0].serial <= serial:
#
# We're already up-to-date.
#
done = True
else:
expecting_SOA = True
#
# Process SOAs in the answer section (other than the initial
# SOA in the first message).
#
for rrset in r.answer[answer_index:]:
if done:
raise dns.exception.FormError("answers after final SOA")
if rrset.rdtype == dns.rdatatype.SOA and rrset.name == oname:
if expecting_SOA:
if rrset[0].serial != serial:
raise dns.exception.FormError(
"IXFR base serial mismatch")
expecting_SOA = False
elif rdtype == dns.rdatatype.IXFR:
delete_mode = not delete_mode
#
# If this SOA RRset is equal to the first we saw then we're
# finished. If this is an IXFR we also check that we're seeing
# the record in the expected part of the response.
#
if rrset == soa_rrset and \
(rdtype == dns.rdatatype.AXFR or
(rdtype == dns.rdatatype.IXFR and delete_mode)):
done = True
elif expecting_SOA:
#
# We made an IXFR request and are expecting another
# SOA RR, but saw something else, so this must be an
# AXFR response.
#
rdtype = dns.rdatatype.AXFR
expecting_SOA = False
if done and q.keyring and not r.had_tsig:
raise dns.exception.FormError("missing TSIG")
yield r
s.close()