Source code for dns.query

# 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 contextlib
import enum
import errno
import os
import selectors
import socket
import struct
import time
import base64
import urllib.parse

import dns.exception
import dns.inet
import dns.name
import dns.message
import dns.rcode
import dns.rdataclass
import dns.rdatatype
import dns.serial
import dns.xfr

try:
    import requests
    from requests_toolbelt.adapters.source import SourceAddressAdapter
    from requests_toolbelt.adapters.host_header_ssl import HostHeaderSSLAdapter
    _have_requests = True
except ImportError:  # pragma: no cover
    _have_requests = False

_have_httpx = False
_have_http2 = False
try:
    import httpx
    _have_httpx = True
    try:
        # See if http2 support is available.
        with httpx.Client(http2=True):
            _have_http2 = True
    except Exception:
        pass
except ImportError:  # pragma: no cover
    pass

have_doh = _have_requests or _have_httpx

try:
    import ssl
except ImportError:  # pragma: no cover
    class ssl:    # type: ignore

        class WantReadException(Exception):
            pass

        class WantWriteException(Exception):
            pass

        class SSLSocket:
            pass

        def create_default_context(self, *args, **kwargs):
            raise Exception('no ssl support')

# Function used to create a socket.  Can be overridden if needed in special
# situations.
socket_factory = socket.socket

[docs]class UnexpectedSource(dns.exception.DNSException): """A DNS query response came from an unexpected address or port."""
[docs]class BadResponse(dns.exception.FormError): """A DNS query response does not respond to the question asked."""
[docs]class NoDOH(dns.exception.DNSException): """DNS over HTTPS (DOH) was requested but the requests module is not available."""
# for backwards compatibility TransferError = dns.xfr.TransferError def _compute_times(timeout): now = time.time() if timeout is None: return (now, None) else: return (now, now + timeout) def _wait_for(fd, readable, writable, _, expiration): # Use the selected selector class to wait for any of the specified # events. An "expiration" absolute time is converted into a relative # timeout. # # The unused parameter is 'error', which is always set when # selecting for read or write, and we have no error-only selects. if readable and isinstance(fd, ssl.SSLSocket) and fd.pending() > 0: return True sel = _selector_class() events = 0 if readable: events |= selectors.EVENT_READ if writable: events |= selectors.EVENT_WRITE if events: sel.register(fd, events) if expiration is None: timeout = None else: timeout = expiration - time.time() if timeout <= 0.0: raise dns.exception.Timeout if not sel.select(timeout): raise dns.exception.Timeout def _set_selector_class(selector_class): # Internal API. Do not use. global _selector_class _selector_class = selector_class if hasattr(selectors, 'PollSelector'): # 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). _selector_class = selectors.PollSelector else: _selector_class = selectors.SelectSelector # pragma: no cover 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 try: n1 = dns.inet.inet_pton(af, a1[0]) n2 = dns.inet.inet_pton(af, a2[0]) except dns.exception.SyntaxError: return False 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(where, port, source, source_port, where_must_be_address=True): # Apply defaults and compute destination and source tuples # suitable for use in connect(), sendto(), or bind(). af = None destination = None try: af = dns.inet.af_for_address(where) destination = where except Exception: if where_must_be_address: raise # URLs are ok so eat the exception if source: saf = dns.inet.af_for_address(source) if af: # We know the destination af, so source had better agree! if saf != af: raise ValueError('different address families for source ' + 'and destination') else: # We didn't know the destination af, but we know the source, # so that's our af. af = saf if source_port and not source: # Caller has specified a source_port but not an address, so we # need to return a source, and we need to use the appropriate # wildcard address as the address. if af == socket.AF_INET: source = '0.0.0.0' elif af == socket.AF_INET6: source = '::' else: raise ValueError('source_port specified but address family is ' 'unknown') # Convert high-level (address, port) tuples into low-level address # tuples. if destination: destination = dns.inet.low_level_address_tuple((destination, port), af) if source: source = dns.inet.low_level_address_tuple((source, source_port), af) return (af, destination, source) def _make_socket(af, type, source, ssl_context=None, server_hostname=None): s = socket_factory(af, type) try: s.setblocking(False) if source is not None: s.bind(source) if ssl_context: return ssl_context.wrap_socket(s, do_handshake_on_connect=False, server_hostname=server_hostname) else: return s except Exception: s.close() raise
[docs]def https(q, where, timeout=None, port=443, source=None, source_port=0, one_rr_per_rrset=False, ignore_trailing=False, session=None, path='/dns-query', post=True, bootstrap_address=None, verify=True): """Return the response obtained after sending a query via DNS-over-HTTPS. *q*, a ``dns.message.Message``, the query to send. *where*, a ``str``, the nameserver IP address or the full URL. If an IP address is given, the URL will be constructed using the following schema: https://<IP-address>:<port>/<path>. *timeout*, a ``float`` or ``None``, the number of seconds to wait before the query times out. If ``None``, the default, wait forever. *port*, a ``int``, the port to send the query to. The default is 443. *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. *session*, an ``httpx.Client`` or ``requests.session.Session``. If provided, the client/session to use to send the queries. *path*, a ``str``. If *where* is an IP address, then *path* will be used to construct the URL to send the DNS query to. *post*, a ``bool``. If ``True``, the default, POST method will be used. *bootstrap_address*, a ``str``, the IP address to use to bypass the system's DNS resolver. *verify*, a ``str``, containing a path to a certificate file or directory. Returns a ``dns.message.Message``. """ if not have_doh: raise NoDOH('Neither httpx nor requests is available.') # pragma: no cover _httpx_ok = _have_httpx wire = q.to_wire() (af, _, source) = _destination_and_source(where, port, source, source_port, False) transport_adapter = None transport = None headers = { "accept": "application/dns-message" } if af is not None: if af == socket.AF_INET: url = 'https://{}:{}{}'.format(where, port, path) elif af == socket.AF_INET6: url = 'https://[{}]:{}{}'.format(where, port, path) elif bootstrap_address is not None: _httpx_ok = False split_url = urllib.parse.urlsplit(where) headers['Host'] = split_url.hostname url = where.replace(split_url.hostname, bootstrap_address) if _have_requests: transport_adapter = HostHeaderSSLAdapter() else: url = where if source is not None: # set source port and source address if _have_httpx: if source_port == 0: transport = httpx.HTTPTransport(local_address=source[0]) else: _httpx_ok = False if _have_requests: transport_adapter = SourceAddressAdapter(source) if session: if _have_httpx: _is_httpx = isinstance(session, httpx.Client) else: _is_httpx = False if _is_httpx and not _httpx_ok: raise NoDOH('Session is httpx, but httpx cannot be used for ' 'the requested operation.') else: _is_httpx = _httpx_ok if not _httpx_ok and not _have_requests: raise NoDOH('Cannot use httpx for this operation, and ' 'requests is not available.') with contextlib.ExitStack() as stack: if not session: if _is_httpx: session = stack.enter_context(httpx.Client(http1=True, http2=_have_http2, verify=verify, transport=transport)) else: session = stack.enter_context(requests.sessions.Session()) if transport_adapter: session.mount(url, transport_adapter) # see https://tools.ietf.org/html/rfc8484#section-4.1.1 for DoH # GET and POST examples if post: headers.update({ "content-type": "application/dns-message", "content-length": str(len(wire)) }) if _is_httpx: response = session.post(url, headers=headers, content=wire, timeout=timeout) else: response = session.post(url, headers=headers, data=wire, timeout=timeout, verify=verify) else: wire = base64.urlsafe_b64encode(wire).rstrip(b"=") if _is_httpx: wire = wire.decode() # httpx does a repr() if we give it bytes response = session.get(url, headers=headers, timeout=timeout, params={"dns": wire}) else: response = session.get(url, headers=headers, timeout=timeout, verify=verify, params={"dns": wire}) # see https://tools.ietf.org/html/rfc8484#section-4.2.1 for info about DoH # status codes if response.status_code < 200 or response.status_code > 299: raise ValueError('{} responded with status code {}' '\nResponse body: {}'.format(where, response.status_code, response.content)) r = dns.message.from_wire(response.content, keyring=q.keyring, request_mac=q.request_mac, one_rr_per_rrset=one_rr_per_rrset, ignore_trailing=ignore_trailing) r.time = response.elapsed if not q.is_response(r): raise BadResponse return r
def _udp_recv(sock, max_size, expiration): """Reads a datagram from the socket. A Timeout exception will be raised if the operation is not completed by the expiration time. """ while True: try: return sock.recvfrom(max_size) except BlockingIOError: _wait_for_readable(sock, expiration) def _udp_send(sock, data, destination, expiration): """Sends the specified datagram to destination over the socket. A Timeout exception will be raised if the operation is not completed by the expiration time. """ while True: try: if destination: return sock.sendto(data, destination) else: return sock.send(data) except BlockingIOError: # pragma: no cover _wait_for_writable(sock, expiration)
[docs]def send_udp(sock, what, destination, expiration=None): """Send a DNS message to the specified UDP socket. *sock*, a ``socket``. *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 = _udp_send(sock, what, destination, expiration) return (n, sent_time)
[docs]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 ``socket``. *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. If *destination* is not ``None``, returns a ``(dns.message.Message, float)`` tuple of the received message and the received time. If *destination* is ``None``, 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 True: (wire, from_address) = _udp_recv(sock, 65535, 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) if destination: return (r, received_time) else: return (r, received_time, from_address)
[docs]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): """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 ``socket.socket``, 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 nonblocking datagram socket, and the *source* and *source_port* are ignored. Returns a ``dns.message.Message``. """ wire = q.to_wire() (af, destination, source) = _destination_and_source(where, port, source, source_port) (begin_time, expiration) = _compute_times(timeout) with contextlib.ExitStack() as stack: if sock: s = sock else: s = stack.enter_context(_make_socket(af, socket.SOCK_DGRAM, source)) send_udp(s, wire, destination, expiration) (r, received_time) = 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
[docs]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): """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 ``socket.socket``, 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, it must be a nonblocking datagram socket, and the *source* and *source_port* are ignored for the UDP query. *tcp_sock*, a ``socket.socket``, or ``None``, the connected socket to use for the TCP query. If ``None``, the default, a socket is created. Note that if a socket is provided, it must be a nonblocking connected stream socket, and *where*, *source* and *source_port* are ignored for the TCP query. Returns a (``dns.message.Message``, tcp) tuple where tcp is ``True`` if and only if TCP was used. """ try: response = udp(q, where, timeout, port, source, source_port, ignore_unexpected, one_rr_per_rrset, ignore_trailing, True, udp_sock) return (response, False) except dns.message.Truncated: response = tcp(q, where, timeout, port, source, source_port, one_rr_per_rrset, ignore_trailing, tcp_sock) return (response, True)
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: try: n = sock.recv(count) if n == b'': raise EOFError count -= len(n) s += n except (BlockingIOError, ssl.SSLWantReadError): _wait_for_readable(sock, expiration) except ssl.SSLWantWriteError: # pragma: no cover _wait_for_writable(sock, expiration) 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: try: current += sock.send(data[current:]) except (BlockingIOError, ssl.SSLWantWriteError): _wait_for_writable(sock, expiration) except ssl.SSLWantReadError: # pragma: no cover _wait_for_readable(sock, expiration)
[docs]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() _net_write(sock, tcpmsg, expiration) return (len(tcpmsg), sent_time)
[docs]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 = _net_read(sock, 2, expiration) (l,) = struct.unpack("!H", ldata) wire = _net_read(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)
def _connect(s, address, expiration): err = s.connect_ex(address) if err == 0: return if err in (errno.EINPROGRESS, errno.EWOULDBLOCK, errno.EALREADY): _wait_for_writable(s, expiration) err = s.getsockopt(socket.SOL_SOCKET, socket.SO_ERROR) if err != 0: raise OSError(err, os.strerror(err))
[docs]def tcp(q, where, timeout=None, port=53, source=None, source_port=0, one_rr_per_rrset=False, ignore_trailing=False, sock=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 ``socket.socket``, or ``None``, the connected 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 nonblocking connected stream socket, and *where*, *port*, *source* and *source_port* are ignored. Returns a ``dns.message.Message``. """ wire = q.to_wire() (begin_time, expiration) = _compute_times(timeout) with contextlib.ExitStack() as stack: if sock: s = sock else: (af, destination, source) = _destination_and_source(where, port, source, source_port) s = stack.enter_context(_make_socket(af, socket.SOCK_STREAM, source)) _connect(s, destination, expiration) send_tcp(s, wire, expiration) (r, received_time) = 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
def _tls_handshake(s, expiration): while True: try: s.do_handshake() return except ssl.SSLWantReadError: _wait_for_readable(s, expiration) except ssl.SSLWantWriteError: # pragma: no cover _wait_for_writable(s, expiration)
[docs]def tls(q, where, timeout=None, port=853, source=None, source_port=0, one_rr_per_rrset=False, ignore_trailing=False, sock=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 ``ssl.SSLSocket``, 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 nonblocking connected SSL stream socket, and *where*, *port*, *source*, *source_port*, and *ssl_context* are ignored. *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``. """ if sock: # # If a socket was provided, there's no special TLS handling needed. # return tcp(q, where, timeout, port, source, source_port, one_rr_per_rrset, ignore_trailing, sock) wire = q.to_wire() (begin_time, expiration) = _compute_times(timeout) (af, destination, source) = _destination_and_source(where, port, source, source_port) if ssl_context is None and not sock: ssl_context = ssl.create_default_context() if server_hostname is None: ssl_context.check_hostname = False with _make_socket(af, socket.SOCK_STREAM, source, ssl_context=ssl_context, server_hostname=server_hostname) as s: _connect(s, destination, expiration) _tls_handshake(s, expiration) send_tcp(s, wire, expiration) (r, received_time) = 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
[docs]def xfr(where, zone, rdtype=dns.rdatatype.AXFR, rdclass=dns.rdataclass.IN, timeout=None, port=53, keyring=None, keyname=None, relativize=True, 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. *where*, a ``str`` containing an IPv4 or IPv6 address, where to send the message. *zone*, a ``dns.name.Name`` or ``str``, the name of the zone to transfer. *rdtype*, an ``int`` or ``str``, the type of zone transfer. The default is ``dns.rdatatype.AXFR``. ``dns.rdatatype.IXFR`` can be used to do an incremental transfer instead. *rdclass*, an ``int`` or ``str``, the class of the zone transfer. The default is ``dns.rdataclass.IN``. *timeout*, a ``float``, the number of seconds to wait for each response message. If None, the default, wait forever. *port*, an ``int``, the port send the message to. The default is 53. *keyring*, a ``dict``, the keyring to use for TSIG. *keyname*, a ``dns.name.Name`` or ``str``, the name of the TSIG key to use. *relativize*, a ``bool``. 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()`` if using this generator to make a zone. *lifetime*, a ``float``, 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. *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. *serial*, an ``int``, the SOA serial number to use as the base for an IXFR diff sequence (only meaningful if *rdtype* is ``dns.rdatatype.IXFR``). *use_udp*, a ``bool``. If ``True``, use UDP (only meaningful for IXFR). *keyalgorithm*, a ``dns.name.Name`` or ``str``, the TSIG algorithm to use. Raises on errors, and so does the generator. Returns a generator of ``dns.message.Message`` objects. """ if isinstance(zone, str): zone = dns.name.from_text(zone) rdtype = dns.rdatatype.RdataType.make(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(where, port, source, source_port) if use_udp and rdtype != dns.rdatatype.IXFR: raise ValueError('cannot do a UDP AXFR') sock_type = socket.SOCK_DGRAM if use_udp else socket.SOCK_STREAM with _make_socket(af, sock_type, source) as s: (_, expiration) = _compute_times(lifetime) _connect(s, destination, expiration) l = len(wire) if use_udp: _udp_send(s, wire, None, expiration) 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 while not done: (_, mexpiration) = _compute_times(timeout) if mexpiration is None or \ (expiration is not None and mexpiration > expiration): mexpiration = expiration if use_udp: (wire, _) = _udp_recv(s, 65535, mexpiration) 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, one_rr_per_rrset=is_ixfr) rcode = r.rcode() if rcode != dns.rcode.NOERROR: raise TransferError(rcode) tsig_ctx = r.tsig_ctx 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 dns.serial.Serial(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
[docs]class UDPMode(enum.IntEnum): """How should UDP be used in an IXFR from :py:func:`inbound_xfr()`? NEVER means "never use UDP; always use TCP" TRY_FIRST means "try to use UDP but fall back to TCP if needed" ONLY means "raise ``dns.xfr.UseTCP`` if trying UDP does not succeed" """ NEVER = 0 TRY_FIRST = 1 ONLY = 2
[docs]def inbound_xfr(where, txn_manager, query=None, port=53, timeout=None, lifetime=None, source=None, source_port=0, udp_mode=UDPMode.NEVER): """Conduct an inbound transfer and apply it via a transaction from the txn_manager. *where*, a ``str`` containing an IPv4 or IPv6 address, where to send the message. *txn_manager*, a ``dns.transaction.TransactionManager``, the txn_manager for this transfer (typically a ``dns.zone.Zone``). *query*, the query to send. If not supplied, a default query is constructed using information from the *txn_manager*. *port*, an ``int``, the port send the message to. The default is 53. *timeout*, a ``float``, the number of seconds to wait for each response message. If None, the default, wait forever. *lifetime*, a ``float``, 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. *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. *udp_mode*, a ``dns.query.UDPMode``, determines how UDP is used for IXFRs. The default is ``dns.UDPMode.NEVER``, i.e. only use TCP. Other possibilities are ``dns.UDPMode.TRY_FIRST``, which means "try UDP but fallback to TCP if needed", and ``dns.UDPMode.ONLY``, which means "try UDP and raise ``dns.xfr.UseTCP`` if it does not succeed. Raises on errors. """ if query is None: (query, serial) = dns.xfr.make_query(txn_manager) else: serial = dns.xfr.extract_serial_from_query(query) rdtype = query.question[0].rdtype is_ixfr = rdtype == dns.rdatatype.IXFR origin = txn_manager.from_wire_origin() wire = query.to_wire() (af, destination, source) = _destination_and_source(where, port, source, source_port) (_, expiration) = _compute_times(lifetime) retry = True while retry: retry = False if is_ixfr and udp_mode != UDPMode.NEVER: sock_type = socket.SOCK_DGRAM is_udp = True else: sock_type = socket.SOCK_STREAM is_udp = False with _make_socket(af, sock_type, source) as s: _connect(s, destination, expiration) if is_udp: _udp_send(s, wire, None, expiration) else: tcpmsg = struct.pack("!H", len(wire)) + wire _net_write(s, tcpmsg, expiration) with dns.xfr.Inbound(txn_manager, rdtype, serial, is_udp) as inbound: done = False tsig_ctx = None while not done: (_, mexpiration) = _compute_times(timeout) if mexpiration is None or \ (expiration is not None and mexpiration > expiration): mexpiration = expiration if is_udp: (rwire, _) = _udp_recv(s, 65535, mexpiration) else: ldata = _net_read(s, 2, mexpiration) (l,) = struct.unpack("!H", ldata) rwire = _net_read(s, l, mexpiration) r = dns.message.from_wire(rwire, keyring=query.keyring, request_mac=query.mac, xfr=True, origin=origin, tsig_ctx=tsig_ctx, multi=(not is_udp), one_rr_per_rrset=is_ixfr) try: done = inbound.process_message(r) except dns.xfr.UseTCP: assert is_udp # should not happen if we used TCP! if udp_mode == UDPMode.ONLY: raise done = True retry = True udp_mode = UDPMode.NEVER continue tsig_ctx = r.tsig_ctx if not retry and query.keyring and not r.had_tsig: raise dns.exception.FormError("missing TSIG")