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 base64
import contextlib
import enum
import errno
import os
import os.path
import random
import selectors
import socket
import struct
import time
import urllib.parse
from typing import Any, Dict, Optional, Tuple, Union, cast

import dns._features
import dns.exception
import dns.inet
import dns.message
import dns.name
import dns.quic
import dns.rcode
import dns.rdataclass
import dns.rdatatype
import dns.serial
import dns.transaction
import dns.tsig
import dns.xfr


def _remaining(expiration):
    if expiration is None:
        return None
    timeout = expiration - time.time()
    if timeout <= 0.0:
        raise dns.exception.Timeout
    return timeout


def _expiration_for_this_attempt(timeout, expiration):
    if expiration is None:
        return None
    return min(time.time() + timeout, expiration)


_have_httpx = dns._features.have("doh")
if _have_httpx:
    import httpcore._backends.sync
    import httpx

    _CoreNetworkBackend = httpcore.NetworkBackend
    _CoreSyncStream = httpcore._backends.sync.SyncStream

    class _NetworkBackend(_CoreNetworkBackend):
        def __init__(self, resolver, local_port, bootstrap_address, family):
            super().__init__()
            self._local_port = local_port
            self._resolver = resolver
            self._bootstrap_address = bootstrap_address
            self._family = family

        def connect_tcp(
            self, host, port, timeout, local_address, socket_options=None
        ):  # pylint: disable=signature-differs
            addresses = []
            _, expiration = _compute_times(timeout)
            if dns.inet.is_address(host):
                addresses.append(host)
            elif self._bootstrap_address is not None:
                addresses.append(self._bootstrap_address)
            else:
                timeout = _remaining(expiration)
                family = self._family
                if local_address:
                    family = dns.inet.af_for_address(local_address)
                answers = self._resolver.resolve_name(
                    host, family=family, lifetime=timeout
                )
                addresses = answers.addresses()
            for address in addresses:
                af = dns.inet.af_for_address(address)
                if local_address is not None or self._local_port != 0:
                    source = dns.inet.low_level_address_tuple(
                        (local_address, self._local_port), af
                    )
                else:
                    source = None
                sock = _make_socket(af, socket.SOCK_STREAM, source)
                attempt_expiration = _expiration_for_this_attempt(2.0, expiration)
                try:
                    _connect(
                        sock,
                        dns.inet.low_level_address_tuple((address, port), af),
                        attempt_expiration,
                    )
                    return _CoreSyncStream(sock)
                except Exception:
                    pass
            raise httpcore.ConnectError

        def connect_unix_socket(
            self, path, timeout, socket_options=None
        ):  # pylint: disable=signature-differs
            raise NotImplementedError

    class _HTTPTransport(httpx.HTTPTransport):
        def __init__(
            self,
            *args,
            local_port=0,
            bootstrap_address=None,
            resolver=None,
            family=socket.AF_UNSPEC,
            **kwargs,
        ):
            if resolver is None:
                # pylint: disable=import-outside-toplevel,redefined-outer-name
                import dns.resolver

                resolver = dns.resolver.Resolver()
            super().__init__(*args, **kwargs)
            self._pool._network_backend = _NetworkBackend(
                resolver, local_port, bootstrap_address, family
            )

else:

    class _HTTPTransport:  # type: ignore
        def connect_tcp(self, host, port, timeout, local_address):
            raise NotImplementedError


have_doh = _have_httpx

try:
    import ssl
except ImportError:  # pragma: no cover

    class ssl:  # type: ignore
        CERT_NONE = 0

        class WantReadException(Exception):
            pass

        class WantWriteException(Exception):
            pass

        class SSLContext:
            pass

        class SSLSocket:
            pass

        @classmethod
        def create_default_context(cls, *args, **kwargs):
            raise Exception("no ssl support")  # pylint: disable=broad-exception-raised


# 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 httpx module is not available."""
class NoDOQ(dns.exception.DNSException): """DNS over QUIC (DOQ) was requested but the aioquic 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 = selectors.DefaultSelector() 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 _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. try: source = dns.inet.any_for_af(af) except Exception: # we catch this and raise ValueError for backwards compatibility 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: # LGTM gets a false positive here, as our default context is OK return ssl_context.wrap_socket( s, do_handshake_on_connect=False, # lgtm[py/insecure-protocol] server_hostname=server_hostname, ) else: return s except Exception: s.close() raise def _maybe_get_resolver( resolver: Optional["dns.resolver.Resolver"], ) -> "dns.resolver.Resolver": # We need a separate method for this to avoid overriding the global # variable "dns" with the as-yet undefined local variable "dns" # in https(). if resolver is None: # pylint: disable=import-outside-toplevel,redefined-outer-name import dns.resolver resolver = dns.resolver.Resolver() return resolver class HTTPVersion(enum.IntEnum): """Which version of HTTP should be used? DEFAULT will select the first version from the list [2, 1.1, 3] that is available. """ DEFAULT = 0 HTTP_1 = 1 H1 = 1 HTTP_2 = 2 H2 = 2 HTTP_3 = 3 H3 = 3
[docs] def https( q: dns.message.Message, where: str, timeout: Optional[float] = None, port: int = 443, source: Optional[str] = None, source_port: int = 0, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, session: Optional[Any] = None, path: str = "/dns-query", post: bool = True, bootstrap_address: Optional[str] = None, verify: Union[bool, str] = True, resolver: Optional["dns.resolver.Resolver"] = None, family: int = socket.AF_UNSPEC, http_version: HTTPVersion = HTTPVersion.DEFAULT, ) -> dns.message.Message: """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``. 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 resolution. *verify*, a ``bool`` or ``str``. If a ``True``, then TLS certificate verification of the server is done using the default CA bundle; if ``False``, then no verification is done; if a `str` then it specifies the path to a certificate file or directory which will be used for verification. *resolver*, a ``dns.resolver.Resolver`` or ``None``, the resolver to use for resolution of hostnames in URLs. If not specified, a new resolver with a default configuration will be used; note this is *not* the default resolver as that resolver might have been configured to use DoH causing a chicken-and-egg problem. This parameter only has an effect if the HTTP library is httpx. *family*, an ``int``, the address family. If socket.AF_UNSPEC (the default), both A and AAAA records will be retrieved. *http_version*, a ``dns.query.HTTPVersion``, indicating which HTTP version to use. Returns a ``dns.message.Message``. """ (af, _, the_source) = _destination_and_source( where, port, source, source_port, False ) if af is not None and dns.inet.is_address(where): if af == socket.AF_INET: url = "https://{}:{}{}".format(where, port, path) elif af == socket.AF_INET6: url = "https://[{}]:{}{}".format(where, port, path) else: url = where if http_version == HTTPVersion.H3 or (http_version == HTTPVersion.DEFAULT and not have_doh): if bootstrap_address is None: parsed = urllib.parse.urlparse(url) resolver = _maybe_get_resolver(resolver) if parsed.hostname is None: raise ValueError("no hostname in URL") if dns.inet.is_address(parsed.hostname): bootstrap_address = parsed.hostname else: answers = resolver.resolve_name(parsed.hostname, family) bootstrap_address = random.choice(list(answers.addresses())) if parsed.port is not None: port = parsed.port return _http3( q, bootstrap_address, url, timeout, port, source, source_port, one_rr_per_rrset, ignore_trailing, verify=verify, post=post, ) if not have_doh: raise NoDOH # pragma: no cover if session and not isinstance(session, httpx.Client): raise ValueError("session parameter must be an httpx.Client") wire = q.to_wire() transport = None headers = {"accept": "application/dns-message"} h1 = http_version in (HTTPVersion.H1, HTTPVersion.DEFAULT) h2 = http_version in (HTTPVersion.H2, HTTPVersion.DEFAULT) # set source port and source address if the_source is None: local_address = None local_port = 0 else: local_address = the_source[0] local_port = the_source[1] transport = _HTTPTransport( local_address=local_address, http1=h1, http2=h2, verify=verify, local_port=local_port, bootstrap_address=bootstrap_address, resolver=resolver, family=family, ) if session: cm: contextlib.AbstractContextManager = contextlib.nullcontext(session) else: cm = httpx.Client(http1=h1, http2=h2, verify=verify, transport=transport) with cm as session: # 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)), } ) response = session.post(url, headers=headers, content=wire, timeout=timeout) else: wire = base64.urlsafe_b64encode(wire).rstrip(b"=") twire = wire.decode() # httpx does a repr() if we give it bytes response = session.get( url, headers=headers, timeout=timeout, params={"dns": twire} ) # 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.total_seconds() if not q.is_response(r): raise BadResponse return r
def _find_header(headers: dns.quic.Headers, name: bytes) -> bytes: if headers is None: raise KeyError for header, value in headers: if header == name: return value raise KeyError def _check_status(headers: dns.quic.Headers, peer: str, wire: bytes) -> None: value = _find_header(headers, b":status") if value is None: raise SyntaxError("no :status header in response") status = int(value) if status < 0: raise SyntaxError("status is negative") if status < 200 or status > 299: error = "" if len(wire) > 0: try: error = ": " + wire.decode() except Exception: pass raise ValueError(f"{peer} responded with status code {status}{error}") def _http3( q: dns.message.Message, where: str, url: str, timeout: Optional[float] = None, port: int = 853, source: Optional[str] = None, source_port: int = 0, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, verify: Union[bool, str] = True, hostname: Optional[str] = None, post: bool = True, ) -> dns.message.Message: if not dns.quic.have_quic: raise NoDOH("DNS-over-HTTP3 is not available.") # pragma: no cover url_parts = urllib.parse.urlparse(url) hostname = url_parts.hostname q.id = 0 wire = q.to_wire() manager = dns.quic.SyncQuicManager( verify_mode=verify, server_name=hostname, h3=True ) with manager: connection = manager.connect(where, port, source, source_port) (start, expiration) = _compute_times(timeout) with connection.make_stream(timeout) as stream: stream.send_h3(url, wire, post) wire = stream.receive(_remaining(expiration)) _check_status(stream.headers(), where, wire) finish = time.time() r = dns.message.from_wire( wire, keyring=q.keyring, request_mac=q.request_mac, one_rr_per_rrset=one_rr_per_rrset, ignore_trailing=ignore_trailing, ) r.time = max(finish - start, 0.0) 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: Any, what: Union[dns.message.Message, bytes], destination: Any, expiration: Optional[float] = None, ) -> Tuple[int, float]: """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: Any, destination: Optional[Any] = None, expiration: Optional[float] = None, ignore_unexpected: bool = False, one_rr_per_rrset: bool = False, keyring: Optional[Dict[dns.name.Name, dns.tsig.Key]] = None, request_mac: Optional[bytes] = b"", ignore_trailing: bool = False, raise_on_truncation: bool = False, ignore_errors: bool = False, query: Optional[dns.message.Message] = None, ) -> Any: """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`` or ``None``, 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. *ignore_errors*, a ``bool``. If various format errors or response mismatches occur, ignore them and keep listening for a valid response. The default is ``False``. *query*, a ``dns.message.Message`` or ``None``. If not ``None`` and *ignore_errors* is ``True``, check that the received message is a response to this query, and if not keep listening for a valid response. """ wire = b"" while True: (wire, from_address) = _udp_recv(sock, 65535, expiration) if not _matches_destination( sock.family, from_address, destination, ignore_unexpected ): continue received_time = time.time() try: 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, ) except dns.message.Truncated as e: # If we got Truncated and not FORMERR, we at least got the header with TC # set, and very likely the question section, so we'll re-raise if the # message seems to be a response as we need to know when truncation happens. # We need to check that it seems to be a response as we don't want a random # injected message with TC set to cause us to bail out. if ( ignore_errors and query is not None and not query.is_response(e.message()) ): continue else: raise except Exception: if ignore_errors: continue else: raise if ignore_errors and query is not None and not query.is_response(r): continue if destination: return (r, received_time) else: return (r, received_time, from_address)
[docs] def udp( q: dns.message.Message, where: str, timeout: Optional[float] = None, port: int = 53, source: Optional[str] = None, source_port: int = 0, ignore_unexpected: bool = False, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, raise_on_truncation: bool = False, sock: Optional[Any] = None, ignore_errors: bool = False, ) -> dns.message.Message: """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. *ignore_errors*, a ``bool``. If various format errors or response mismatches occur, ignore them and keep listening for a valid response. The default is ``False``. 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) if sock: cm: contextlib.AbstractContextManager = contextlib.nullcontext(sock) else: cm = _make_socket(af, socket.SOCK_DGRAM, source) with cm as s: 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, ignore_errors, q, ) r.time = received_time - begin_time # We don't need to check q.is_response() if we are in ignore_errors mode # as receive_udp() will have checked it. if not (ignore_errors or q.is_response(r)): raise BadResponse return r assert ( False # help mypy figure out we can't get here lgtm[py/unreachable-statement] )
[docs] def udp_with_fallback( q: dns.message.Message, where: str, timeout: Optional[float] = None, port: int = 53, source: Optional[str] = None, source_port: int = 0, ignore_unexpected: bool = False, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, udp_sock: Optional[Any] = None, tcp_sock: Optional[Any] = None, ignore_errors: bool = False, ) -> Tuple[dns.message.Message, bool]: """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. *ignore_errors*, a ``bool``. If various format errors or response mismatches occur while listening for UDP, ignore them and keep listening for a valid response. The default is ``False``. 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, ignore_errors, ) 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: Any, what: Union[dns.message.Message, bytes], expiration: Optional[float] = None, ) -> Tuple[int, float]: """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): tcpmsg = what.to_wire(prepend_length=True) else: # 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 = len(what).to_bytes(2, "big") + what sent_time = time.time() _net_write(sock, tcpmsg, expiration) return (len(tcpmsg), sent_time)
[docs] def receive_tcp( sock: Any, expiration: Optional[float] = None, one_rr_per_rrset: bool = False, keyring: Optional[Dict[dns.name.Name, dns.tsig.Key]] = None, request_mac: Optional[bytes] = b"", ignore_trailing: bool = False, ) -> Tuple[dns.message.Message, float]: """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`` or ``None``, 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: dns.message.Message, where: str, timeout: Optional[float] = None, port: int = 53, source: Optional[str] = None, source_port: int = 0, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, sock: Optional[Any] = None, ) -> dns.message.Message: """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) if sock: cm: contextlib.AbstractContextManager = contextlib.nullcontext(sock) else: (af, destination, source) = _destination_and_source( where, port, source, source_port ) cm = _make_socket(af, socket.SOCK_STREAM, source) with cm as s: if not sock: _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 assert ( False # help mypy figure out we can't get here lgtm[py/unreachable-statement] )
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) def _make_dot_ssl_context( server_hostname: Optional[str], verify: Union[bool, str] ) -> ssl.SSLContext: cafile: Optional[str] = None capath: Optional[str] = None if isinstance(verify, str): if os.path.isfile(verify): cafile = verify elif os.path.isdir(verify): capath = verify else: raise ValueError("invalid verify string") ssl_context = ssl.create_default_context(cafile=cafile, capath=capath) ssl_context.minimum_version = ssl.TLSVersion.TLSv1_2 if server_hostname is None: ssl_context.check_hostname = False ssl_context.set_alpn_protocols(["dot"]) if verify is False: ssl_context.verify_mode = ssl.CERT_NONE return ssl_context
[docs] def tls( q: dns.message.Message, where: str, timeout: Optional[float] = None, port: int = 853, source: Optional[str] = None, source_port: int = 0, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, sock: Optional[ssl.SSLSocket] = None, ssl_context: Optional[ssl.SSLContext] = None, server_hostname: Optional[str] = None, verify: Union[bool, str] = True, ) -> dns.message.Message: """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. *verify*, a ``bool`` or ``str``. If a ``True``, then TLS certificate verification of the server is done using the default CA bundle; if ``False``, then no verification is done; if a `str` then it specifies the path to a certificate file or directory which will be used for verification. 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 = _make_dot_ssl_context(server_hostname, verify) 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 assert ( False # help mypy figure out we can't get here lgtm[py/unreachable-statement] )
def quic( q: dns.message.Message, where: str, timeout: Optional[float] = None, port: int = 853, source: Optional[str] = None, source_port: int = 0, one_rr_per_rrset: bool = False, ignore_trailing: bool = False, connection: Optional[dns.quic.SyncQuicConnection] = None, verify: Union[bool, str] = True, hostname: Optional[str] = None, server_hostname: Optional[str] = None, ) -> dns.message.Message: """Return the response obtained after sending a query via DNS-over-QUIC. *q*, a ``dns.message.Message``, the query to send. *where*, a ``str``, the nameserver IP address. *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 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. *connection*, a ``dns.quic.SyncQuicConnection``. If provided, the connection to use to send the query. *verify*, a ``bool`` or ``str``. If a ``True``, then TLS certificate verification of the server is done using the default CA bundle; if ``False``, then no verification is done; if a `str` then it specifies the path to a certificate file or directory which will be used for verification. *hostname*, a ``str`` containing the server's hostname or ``None``. The default is ``None``, which means that no hostname is known, and if an SSL context is created, hostname checking will be disabled. This value is ignored if *url* is not ``None``. *server_hostname*, a ``str`` or ``None``. This item is for backwards compatibility only, and has the same meaning as *hostname*. Returns a ``dns.message.Message``. """ if not dns.quic.have_quic: raise NoDOQ("DNS-over-QUIC is not available.") # pragma: no cover if server_hostname is not None and hostname is None: hostname = server_hostname q.id = 0 wire = q.to_wire() the_connection: dns.quic.SyncQuicConnection the_manager: dns.quic.SyncQuicManager if connection: manager: contextlib.AbstractContextManager = contextlib.nullcontext(None) the_connection = connection else: manager = dns.quic.SyncQuicManager(verify_mode=verify, server_name=hostname) the_manager = manager # for type checking happiness with manager: if not connection: the_connection = the_manager.connect(where, port, source, source_port) (start, expiration) = _compute_times(timeout) with the_connection.make_stream(timeout) as stream: stream.send(wire, True) wire = stream.receive(_remaining(expiration)) finish = time.time() r = dns.message.from_wire( wire, keyring=q.keyring, request_mac=q.request_mac, one_rr_per_rrset=one_rr_per_rrset, ignore_trailing=ignore_trailing, ) r.time = max(finish - start, 0.0) if not q.is_response(r): raise BadResponse return 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
def _inbound_xfr( where: str, txn_manager: dns.transaction.TransactionManager, query: Optional[dns.message.Message] = None, port: int = 53, timeout: Optional[float] = None, lifetime: Optional[float] = None, source: Optional[str] = None, source_port: int = 0, udp_mode: UDPMode = UDPMode.NEVER, ) -> Any: """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 yield r tsig_ctx = r.tsig_ctx if not retry and query.keyring and not r.had_tsig: raise dns.exception.FormError("missing TSIG")
[docs] def xfr( where: str, zone: Union[dns.name.Name, str], rdtype: Union[dns.rdatatype.RdataType, str] = dns.rdatatype.AXFR, rdclass: Union[dns.rdataclass.RdataClass, str] = dns.rdataclass.IN, timeout: Optional[float] = None, port: int = 53, keyring: Optional[Dict[dns.name.Name, dns.tsig.Key]] = None, keyname: Optional[Union[dns.name.Name, str]] = None, relativize: bool = True, lifetime: Optional[float] = None, source: Optional[str] = None, source_port: int = 0, serial: int = 0, use_udp: bool = False, keyalgorithm: Union[dns.name.Name, str] = dns.tsig.default_algorithm, ) -> Any: """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. """ class DummyTransactionManager(dns.transaction.TransactionManager): def __init__(self, origin, relativize): self.info = (origin, relativize, dns.name.empty if relativize else origin) def origin_information(self): return self.info def get_class(self) -> dns.rdataclass.RdataClass: raise NotImplementedError # pragma: no cover def reader(self): raise NotImplementedError # pragma: no cover def writer(self, replacement: bool = False) -> dns.transaction.Transaction: class DummyTransaction(object): def nop(self, *args, **kw): pass def __getattr__(self, _): return self.nop return cast(dns.transaction.Transaction, DummyTransaction()) 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 = q.find_rrset( q.authority, zone, dns.rdataclass.IN, dns.rdatatype.SOA, create=True ) soa = dns.rdata.from_text("IN", "SOA", ". . %u 0 0 0 0" % serial) rrset.add(soa, 0) if keyring is not None: q.use_tsig(keyring, keyname, algorithm=keyalgorithm) tm = DummyTransactionManager(zone, relativize) if use_udp and rdtype != dns.rdatatype.IXFR: raise ValueError("cannot do a UDP AXFR") udp_mode = UDPMode.ONLY if use_udp else UDPMode.NEVER yield from _inbound_xfr( where, tm, q, port, timeout, lifetime, source, source_port, udp_mode )
[docs] def inbound_xfr( where: str, txn_manager: dns.transaction.TransactionManager, query: Optional[dns.message.Message] = None, port: int = 53, timeout: Optional[float] = None, lifetime: Optional[float] = None, source: Optional[str] = None, source_port: int = 0, udp_mode: UDPMode = UDPMode.NEVER, ) -> None: """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. """ for _ in _inbound_xfr( where, txn_manager, query, port, timeout, lifetime, source, source_port, udp_mode, ): pass