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# 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.
"""Talk to a DNS server."""
import socket
import struct
import time
import dns.asyncbackend
import dns.exception
import dns.inet
import dns.name
import dns.message
import dns.rcode
import dns.rdataclass
import dns.rdatatype
from dns.query import _compute_times, _matches_destination, BadResponse, ssl
# for brevity
_lltuple = dns.inet.low_level_address_tuple
def _source_tuple(af, address, port):
# Make a high level source tuple, or return None if address and port
# are both None
if address or port:
if address is None:
if af == socket.AF_INET:
address = '0.0.0.0'
elif af == socket.AF_INET6:
address = '::'
else:
raise NotImplementedError(f'unknown address family {af}')
return (address, port)
else:
return None
def _timeout(expiration, now=None):
if expiration:
if not now:
now = time.time()
return max(expiration - now, 0)
else:
return None
async def send_udp(sock, what, destination, expiration=None):
"""Send a DNS message to the specified UDP socket.
*sock*, a ``dns.asyncbackend.DatagramSocket``.
*what*, a ``bytes`` or ``dns.message.Message``, the message to send.
*destination*, a destination tuple appropriate for the address family
of the socket, specifying where to send the query.
*expiration*, a ``float`` or ``None``, the absolute time at which
a timeout exception should be raised. If ``None``, no timeout will
occur.
Returns an ``(int, float)`` tuple of bytes sent and the sent time.
"""
if isinstance(what, dns.message.Message):
what = what.to_wire()
sent_time = time.time()
n = await sock.sendto(what, destination, _timeout(expiration, sent_time))
return (n, sent_time)
async def receive_udp(sock, destination=None, expiration=None,
ignore_unexpected=False, one_rr_per_rrset=False,
keyring=None, request_mac=b'', ignore_trailing=False,
raise_on_truncation=False):
"""Read a DNS message from a UDP socket.
*sock*, a ``dns.asyncbackend.DatagramSocket``.
*destination*, a destination tuple appropriate for the address family
of the socket, specifying where the message is expected to arrive from.
When receiving a response, this would be where the associated query was
sent.
*expiration*, a ``float`` or ``None``, the absolute time at which
a timeout exception should be raised. If ``None``, no timeout will
occur.
*ignore_unexpected*, a ``bool``. If ``True``, ignore responses from
unexpected sources.
*one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
RRset.
*keyring*, a ``dict``, the keyring to use for TSIG.
*request_mac*, a ``bytes``, the MAC of the request (for TSIG).
*ignore_trailing*, a ``bool``. If ``True``, ignore trailing
junk at end of the received message.
*raise_on_truncation*, a ``bool``. If ``True``, raise an exception if
the TC bit is set.
Raises if the message is malformed, if network errors occur, of if
there is a timeout.
Returns a ``(dns.message.Message, float, tuple)`` tuple of the received
message, the received time, and the address where the message arrived from.
"""
wire = b''
while 1:
(wire, from_address) = await sock.recvfrom(65535, _timeout(expiration))
if _matches_destination(sock.family, from_address, destination,
ignore_unexpected):
break
received_time = time.time()
r = dns.message.from_wire(wire, keyring=keyring, request_mac=request_mac,
one_rr_per_rrset=one_rr_per_rrset,
ignore_trailing=ignore_trailing,
raise_on_truncation=raise_on_truncation)
return (r, received_time, from_address)
async def udp(q, where, timeout=None, port=53, source=None, source_port=0,
ignore_unexpected=False, one_rr_per_rrset=False,
ignore_trailing=False, raise_on_truncation=False, sock=None,
backend=None):
"""Return the response obtained after sending a query via UDP.
*q*, a ``dns.message.Message``, the query to send
*where*, a ``str`` containing an IPv4 or IPv6 address, where
to send the message.
*timeout*, a ``float`` or ``None``, the number of seconds to wait before the
query times out. If ``None``, the default, wait forever.
*port*, an ``int``, the port send the message to. The default is 53.
*source*, a ``str`` containing an IPv4 or IPv6 address, specifying
the source address. The default is the wildcard address.
*source_port*, an ``int``, the port from which to send the message.
The default is 0.
*ignore_unexpected*, a ``bool``. If ``True``, ignore responses from
unexpected sources.
*one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
RRset.
*ignore_trailing*, a ``bool``. If ``True``, ignore trailing
junk at end of the received message.
*raise_on_truncation*, a ``bool``. If ``True``, raise an exception if
the TC bit is set.
*sock*, a ``dns.asyncbackend.DatagramSocket``, or ``None``,
the socket to use for the query. If ``None``, the default, a
socket is created. Note that if a socket is provided, the
*source*, *source_port*, and *backend* are ignored.
*backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``,
the default, then dnspython will use the default backend.
Returns a ``dns.message.Message``.
"""
wire = q.to_wire()
(begin_time, expiration) = _compute_times(timeout)
s = None
# After 3.6 is no longer supported, this can use an AsyncExitStack.
try:
af = dns.inet.af_for_address(where)
destination = _lltuple((where, port), af)
if sock:
s = sock
else:
if not backend:
backend = dns.asyncbackend.get_default_backend()
stuple = _source_tuple(af, source, source_port)
s = await backend.make_socket(af, socket.SOCK_DGRAM, 0, stuple)
await send_udp(s, wire, destination, expiration)
(r, received_time, _) = await receive_udp(s, destination, expiration,
ignore_unexpected,
one_rr_per_rrset,
q.keyring, q.mac,
ignore_trailing,
raise_on_truncation)
r.time = received_time - begin_time
if not q.is_response(r):
raise BadResponse
return r
finally:
if not sock and s:
await s.close()
async def udp_with_fallback(q, where, timeout=None, port=53, source=None,
source_port=0, ignore_unexpected=False,
one_rr_per_rrset=False, ignore_trailing=False,
udp_sock=None, tcp_sock=None, backend=None):
"""Return the response to the query, trying UDP first and falling back
to TCP if UDP results in a truncated response.
*q*, a ``dns.message.Message``, the query to send
*where*, a ``str`` containing an IPv4 or IPv6 address, where
to send the message.
*timeout*, a ``float`` or ``None``, the number of seconds to wait before the
query times out. If ``None``, the default, wait forever.
*port*, an ``int``, the port send the message to. The default is 53.
*source*, a ``str`` containing an IPv4 or IPv6 address, specifying
the source address. The default is the wildcard address.
*source_port*, an ``int``, the port from which to send the message.
The default is 0.
*ignore_unexpected*, a ``bool``. If ``True``, ignore responses from
unexpected sources.
*one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
RRset.
*ignore_trailing*, a ``bool``. If ``True``, ignore trailing
junk at end of the received message.
*udp_sock*, a ``dns.asyncbackend.DatagramSocket``, or ``None``,
the socket to use for the UDP query. If ``None``, the default, a
socket is created. Note that if a socket is provided the *source*,
*source_port*, and *backend* are ignored for the UDP query.
*tcp_sock*, a ``dns.asyncbackend.StreamSocket``, or ``None``, the
socket to use for the TCP query. If ``None``, the default, a
socket is created. Note that if a socket is provided *where*,
*source*, *source_port*, and *backend* are ignored for the TCP query.
*backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``,
the default, then dnspython will use the default backend.
Returns a (``dns.message.Message``, tcp) tuple where tcp is ``True``
if and only if TCP was used.
"""
try:
response = await udp(q, where, timeout, port, source, source_port,
ignore_unexpected, one_rr_per_rrset,
ignore_trailing, True, udp_sock, backend)
return (response, False)
except dns.message.Truncated:
response = await tcp(q, where, timeout, port, source, source_port,
one_rr_per_rrset, ignore_trailing, tcp_sock,
backend)
return (response, True)
async def send_tcp(sock, what, expiration=None):
"""Send a DNS message to the specified TCP socket.
*sock*, a ``socket``.
*what*, a ``bytes`` or ``dns.message.Message``, the message to send.
*expiration*, a ``float`` or ``None``, the absolute time at which
a timeout exception should be raised. If ``None``, no timeout will
occur.
Returns an ``(int, float)`` tuple of bytes sent and the sent time.
"""
if isinstance(what, dns.message.Message):
what = what.to_wire()
l = len(what)
# 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) + what
sent_time = time.time()
await sock.sendall(tcpmsg, expiration)
return (len(tcpmsg), sent_time)
async def _read_exactly(sock, count, expiration):
"""Read the specified number of bytes from stream. Keep trying until we
either get the desired amount, or we hit EOF.
"""
s = b''
while count > 0:
n = await sock.recv(count, _timeout(expiration))
if n == b'':
raise EOFError
count = count - len(n)
s = s + n
return s
async def receive_tcp(sock, expiration=None, one_rr_per_rrset=False,
keyring=None, request_mac=b'', ignore_trailing=False):
"""Read a DNS message from a TCP socket.
*sock*, a ``socket``.
*expiration*, a ``float`` or ``None``, the absolute time at which
a timeout exception should be raised. If ``None``, no timeout will
occur.
*one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
RRset.
*keyring*, a ``dict``, the keyring to use for TSIG.
*request_mac*, a ``bytes``, the MAC of the request (for TSIG).
*ignore_trailing*, a ``bool``. If ``True``, ignore trailing
junk at end of the received message.
Raises if the message is malformed, if network errors occur, of if
there is a timeout.
Returns a ``(dns.message.Message, float)`` tuple of the received message
and the received time.
"""
ldata = await _read_exactly(sock, 2, expiration)
(l,) = struct.unpack("!H", ldata)
wire = await _read_exactly(sock, l, expiration)
received_time = time.time()
r = dns.message.from_wire(wire, keyring=keyring, request_mac=request_mac,
one_rr_per_rrset=one_rr_per_rrset,
ignore_trailing=ignore_trailing)
return (r, received_time)
async def tcp(q, where, timeout=None, port=53, source=None, source_port=0,
one_rr_per_rrset=False, ignore_trailing=False, sock=None,
backend=None):
"""Return the response obtained after sending a query via TCP.
*q*, a ``dns.message.Message``, the query to send
*where*, a ``str`` containing an IPv4 or IPv6 address, where
to send the message.
*timeout*, a ``float`` or ``None``, the number of seconds to wait before the
query times out. If ``None``, the default, wait forever.
*port*, an ``int``, the port send the message to. The default is 53.
*source*, a ``str`` containing an IPv4 or IPv6 address, specifying
the source address. The default is the wildcard address.
*source_port*, an ``int``, the port from which to send the message.
The default is 0.
*one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
RRset.
*ignore_trailing*, a ``bool``. If ``True``, ignore trailing
junk at end of the received message.
*sock*, a ``dns.asyncbacket.StreamSocket``, or ``None``, the
socket to use for the query. If ``None``, the default, a socket
is created. Note that if a socket is provided
*where*, *port*, *source*, *source_port*, and *backend* are ignored.
*backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``,
the default, then dnspython will use the default backend.
Returns a ``dns.message.Message``.
"""
wire = q.to_wire()
(begin_time, expiration) = _compute_times(timeout)
s = None
# After 3.6 is no longer supported, this can use an AsyncExitStack.
try:
if sock:
# Verify that the socket is connected, as if it's not connected,
# it's not writable, and the polling in send_tcp() will time out or
# hang forever.
await sock.getpeername()
s = sock
else:
# These are simple (address, port) pairs, not
# family-dependent tuples you pass to lowlevel socket
# code.
af = dns.inet.af_for_address(where)
stuple = _source_tuple(af, source, source_port)
dtuple = (where, port)
if not backend:
backend = dns.asyncbackend.get_default_backend()
s = await backend.make_socket(af, socket.SOCK_STREAM, 0, stuple,
dtuple, timeout)
await send_tcp(s, wire, expiration)
(r, received_time) = await receive_tcp(s, expiration, one_rr_per_rrset,
q.keyring, q.mac,
ignore_trailing)
r.time = received_time - begin_time
if not q.is_response(r):
raise BadResponse
return r
finally:
if not sock and s:
await s.close()
async def tls(q, where, timeout=None, port=853, source=None, source_port=0,
one_rr_per_rrset=False, ignore_trailing=False, sock=None,
backend=None, ssl_context=None, server_hostname=None):
"""Return the response obtained after sending a query via TLS.
*q*, a ``dns.message.Message``, the query to send
*where*, a ``str`` containing an IPv4 or IPv6 address, where
to send the message.
*timeout*, a ``float`` or ``None``, the number of seconds to wait before the
query times out. If ``None``, the default, wait forever.
*port*, an ``int``, the port send the message to. The default is 853.
*source*, a ``str`` containing an IPv4 or IPv6 address, specifying
the source address. The default is the wildcard address.
*source_port*, an ``int``, the port from which to send the message.
The default is 0.
*one_rr_per_rrset*, a ``bool``. If ``True``, put each RR into its own
RRset.
*ignore_trailing*, a ``bool``. If ``True``, ignore trailing
junk at end of the received message.
*sock*, an ``asyncbackend.StreamSocket``, or ``None``, the socket
to use for the query. If ``None``, the default, a socket is
created. Note that if a socket is provided, it must be a
connected SSL stream socket, and *where*, *port*,
*source*, *source_port*, *backend*, *ssl_context*, and *server_hostname*
are ignored.
*backend*, a ``dns.asyncbackend.Backend``, or ``None``. If ``None``,
the default, then dnspython will use the default backend.
*ssl_context*, an ``ssl.SSLContext``, the context to use when establishing
a TLS connection. If ``None``, the default, creates one with the default
configuration.
*server_hostname*, a ``str`` containing the server's hostname. The
default is ``None``, which means that no hostname is known, and if an
SSL context is created, hostname checking will be disabled.
Returns a ``dns.message.Message``.
"""
# After 3.6 is no longer supported, this can use an AsyncExitStack.
(begin_time, expiration) = _compute_times(timeout)
if not sock:
if ssl_context is None:
ssl_context = ssl.create_default_context()
if server_hostname is None:
ssl_context.check_hostname = False
else:
ssl_context = None
server_hostname = None
af = dns.inet.af_for_address(where)
stuple = _source_tuple(af, source, source_port)
dtuple = (where, port)
if not backend:
backend = dns.asyncbackend.get_default_backend()
s = await backend.make_socket(af, socket.SOCK_STREAM, 0, stuple,
dtuple, timeout, ssl_context,
server_hostname)
else:
s = sock
try:
timeout = _timeout(expiration)
response = await tcp(q, where, timeout, port, source, source_port,
one_rr_per_rrset, ignore_trailing, s, backend)
end_time = time.time()
response.time = end_time - begin_time
return response
finally:
if not sock and s:
await s.close()