Edit File: query.py
# Copyright (C) 2003-2007, 2009-2011 Nominum, Inc. # # Permission to use, copy, modify, and distribute this software and its # documentation for any purpose with or without fee is hereby granted, # provided that the above copyright notice and this permission notice # appear in all copies. # # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. """Talk to a DNS server.""" from __future__ import generators import errno import select import socket import struct import sys import time import dns.exception import dns.inet import dns.name import dns.message import dns.rdataclass import dns.rdatatype from ._compat import long, string_types if sys.version_info > (3,): select_error = OSError else: select_error = select.error # Function used to create a socket. Can be overridden if needed in special # situations. socket_factory = socket.socket class UnexpectedSource(dns.exception.DNSException): """A DNS query response came from an unexpected address or port.""" class BadResponse(dns.exception.FormError): """A DNS query response does not respond to the question asked.""" def _compute_expiration(timeout): if timeout is None: return None else: return time.time() + timeout def _poll_for(fd, readable, writable, error, timeout): """Poll polling backend. @param fd: File descriptor @type fd: int @param readable: Whether to wait for readability @type readable: bool @param writable: Whether to wait for writability @type writable: bool @param timeout: Deadline timeout (expiration time, in seconds) @type timeout: float @return True on success, False on timeout """ event_mask = 0 if readable: event_mask |= select.POLLIN if writable: event_mask |= select.POLLOUT if error: event_mask |= select.POLLERR pollable = select.poll() pollable.register(fd, event_mask) if timeout: event_list = pollable.poll(long(timeout * 1000)) else: event_list = pollable.poll() return bool(event_list) def _select_for(fd, readable, writable, error, timeout): """Select polling backend. @param fd: File descriptor @type fd: int @param readable: Whether to wait for readability @type readable: bool @param writable: Whether to wait for writability @type writable: bool @param timeout: Deadline timeout (expiration time, in seconds) @type timeout: float @return True on success, False on timeout """ rset, wset, xset = [], [], [] if readable: rset = [fd] if writable: wset = [fd] if error: xset = [fd] if timeout is None: (rcount, wcount, xcount) = select.select(rset, wset, xset) else: (rcount, wcount, xcount) = select.select(rset, wset, xset, timeout) return bool((rcount or wcount or xcount)) def _wait_for(fd, readable, writable, error, expiration): done = False while not done: if expiration is None: timeout = None else: timeout = expiration - time.time() if timeout <= 0.0: raise dns.exception.Timeout try: if not _polling_backend(fd, readable, writable, error, timeout): raise dns.exception.Timeout except select_error as e: if e.args[0] != errno.EINTR: raise e done = True def _set_polling_backend(fn): """ Internal API. Do not use. """ global _polling_backend _polling_backend = fn if hasattr(select, 'poll'): # Prefer poll() on platforms that support it because it has no # limits on the maximum value of a file descriptor (plus it will # be more efficient for high values). _polling_backend = _poll_for else: _polling_backend = _select_for def _wait_for_readable(s, expiration): _wait_for(s, True, False, True, expiration) def _wait_for_writable(s, expiration): _wait_for(s, False, True, True, expiration) def _addresses_equal(af, a1, a2): # Convert the first value of the tuple, which is a textual format # address into binary form, so that we are not confused by different # textual representations of the same address n1 = dns.inet.inet_pton(af, a1[0]) n2 = dns.inet.inet_pton(af, a2[0]) return n1 == n2 and a1[1:] == a2[1:] def _matches_destination(af, from_address, destination, ignore_unexpected): # Check that from_address is appropriate for a response to a query # sent to destination. if not destination: return True if _addresses_equal(af, from_address, destination) or ( dns.inet.is_multicast(destination[0]) and from_address[1:] == destination[1:] ): return True elif ignore_unexpected: return False raise UnexpectedSource( f"got a response from {from_address} instead of " f"{destination}" ) def _destination_and_source(af, where, port, source, source_port): # Apply defaults and compute destination and source tuples # suitable for use in connect(), sendto(), or bind(). if af is None: try: af = dns.inet.af_for_address(where) except Exception: af = dns.inet.AF_INET if af == dns.inet.AF_INET: destination = (where, port) if source is not None or source_port != 0: if source is None: source = '0.0.0.0' source = (source, source_port) elif af == dns.inet.AF_INET6: destination = (where, port, 0, 0) if source is not None or source_port != 0: if source is None: source = '::' source = (source, source_port, 0, 0) return (af, destination, source) def udp(q, where, timeout=None, port=53, af=None, source=None, source_port=0, ignore_unexpected=False, one_rr_per_rrset=False, ignore_errors=False): """Return the response obtained after sending a query via UDP. @param q: the query @type q: dns.message.Message @param where: where to send the message @type where: string containing an IPv4 or IPv6 address @param timeout: The number of seconds to wait before the query times out. If None, the default, wait forever. @type timeout: float @param port: The port to which to send the message. The default is 53. @type port: int @param af: the address family to use. The default is None, which causes the address family to use to be inferred from the form of where. If the inference attempt fails, AF_INET is used. @type af: int @rtype: dns.message.Message object @param source: source address. The default is the wildcard address. @type source: string @param source_port: The port from which to send the message. The default is 0. @type source_port: int @param ignore_unexpected: If True, ignore responses from unexpected sources. The default is False. @type ignore_unexpected: bool @param one_rr_per_rrset: Put each RR into its own RRset @type one_rr_per_rrset: bool """ wire = q.to_wire() (af, destination, source) = _destination_and_source(af, where, port, source, source_port) s = socket_factory(af, socket.SOCK_DGRAM, 0) begin_time = None try: expiration = _compute_expiration(timeout) s.setblocking(0) if source is not None: s.bind(source) _wait_for_writable(s, expiration) begin_time = time.time() s.sendto(wire, destination) while 1: _wait_for_readable(s, expiration) (wire, from_address) = s.recvfrom(65535) if not _matches_destination( s.family, from_address, destination, ignore_unexpected ): continue response_time = time.time() - begin_time try: r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac, one_rr_per_rrset=one_rr_per_rrset) r.time = response_time except Exception: if ignore_errors: continue else: raise if q.is_response(r): return r else: if ignore_errors: continue else: raise BadResponse finally: s.close() def _net_read(sock, count, expiration): """Read the specified number of bytes from sock. Keep trying until we either get the desired amount, or we hit EOF. A Timeout exception will be raised if the operation is not completed by the expiration time. """ s = b'' while count > 0: _wait_for_readable(sock, expiration) n = sock.recv(count) if n == b'': raise EOFError count = count - len(n) s = s + n return s def _net_write(sock, data, expiration): """Write the specified data to the socket. A Timeout exception will be raised if the operation is not completed by the expiration time. """ current = 0 l = len(data) while current < l: _wait_for_writable(sock, expiration) current += sock.send(data[current:]) def _connect(s, address): try: s.connect(address) except socket.error: (ty, v) = sys.exc_info()[:2] if hasattr(v, 'errno'): v_err = v.errno else: v_err = v[0] if v_err not in [errno.EINPROGRESS, errno.EWOULDBLOCK, errno.EALREADY]: raise v def tcp(q, where, timeout=None, port=53, af=None, source=None, source_port=0, one_rr_per_rrset=False): """Return the response obtained after sending a query via TCP. @param q: the query @type q: dns.message.Message object @param where: where to send the message @type where: string containing an IPv4 or IPv6 address @param timeout: The number of seconds to wait before the query times out. If None, the default, wait forever. @type timeout: float @param port: The port to which to send the message. The default is 53. @type port: int @param af: the address family to use. The default is None, which causes the address family to use to be inferred from the form of where. If the inference attempt fails, AF_INET is used. @type af: int @rtype: dns.message.Message object @param source: source address. The default is the wildcard address. @type source: string @param source_port: The port from which to send the message. The default is 0. @type source_port: int @param one_rr_per_rrset: Put each RR into its own RRset @type one_rr_per_rrset: bool """ wire = q.to_wire() (af, destination, source) = _destination_and_source(af, where, port, source, source_port) s = socket_factory(af, socket.SOCK_STREAM, 0) begin_time = None try: expiration = _compute_expiration(timeout) s.setblocking(0) begin_time = time.time() if source is not None: s.bind(source) _connect(s, destination) l = len(wire) # copying the wire into tcpmsg is inefficient, but lets us # avoid writev() or doing a short write that would get pushed # onto the net tcpmsg = struct.pack("!H", l) + wire _net_write(s, tcpmsg, expiration) ldata = _net_read(s, 2, expiration) (l,) = struct.unpack("!H", ldata) wire = _net_read(s, l, expiration) finally: if begin_time is None: response_time = 0 else: response_time = time.time() - begin_time s.close() r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac, one_rr_per_rrset=one_rr_per_rrset) r.time = response_time if not q.is_response(r): raise BadResponse return r def xfr(where, zone, rdtype=dns.rdatatype.AXFR, rdclass=dns.rdataclass.IN, timeout=None, port=53, keyring=None, keyname=None, relativize=True, af=None, lifetime=None, source=None, source_port=0, serial=0, use_udp=False, keyalgorithm=dns.tsig.default_algorithm): """Return a generator for the responses to a zone transfer. @param where: where to send the message @type where: string containing an IPv4 or IPv6 address @param zone: The name of the zone to transfer @type zone: dns.name.Name object or string @param rdtype: The type of zone transfer. The default is dns.rdatatype.AXFR. @type rdtype: int or string @param rdclass: The class of the zone transfer. The default is dns.rdataclass.IN. @type rdclass: int or string @param timeout: The number of seconds to wait for each response message. If None, the default, wait forever. @type timeout: float @param port: The port to which to send the message. The default is 53. @type port: int @param keyring: The TSIG keyring to use @type keyring: dict @param keyname: The name of the TSIG key to use @type keyname: dns.name.Name object or string @param relativize: If True, all names in the zone will be relativized to the zone origin. It is essential that the relativize setting matches the one specified to dns.zone.from_xfr(). @type relativize: bool @param af: the address family to use. The default is None, which causes the address family to use to be inferred from the form of where. If the inference attempt fails, AF_INET is used. @type af: int @param lifetime: The total number of seconds to spend doing the transfer. If None, the default, then there is no limit on the time the transfer may take. @type lifetime: float @rtype: generator of dns.message.Message objects. @param source: source address. The default is the wildcard address. @type source: string @param source_port: The port from which to send the message. The default is 0. @type source_port: int @param serial: The SOA serial number to use as the base for an IXFR diff sequence (only meaningful if rdtype == dns.rdatatype.IXFR). @type serial: int @param use_udp: Use UDP (only meaningful for IXFR) @type use_udp: bool @param keyalgorithm: The TSIG algorithm to use; defaults to dns.tsig.default_algorithm @type keyalgorithm: string """ if isinstance(zone, string_types): zone = dns.name.from_text(zone) if isinstance(rdtype, string_types): rdtype = dns.rdatatype.from_text(rdtype) q = dns.message.make_query(zone, rdtype, rdclass) if rdtype == dns.rdatatype.IXFR: rrset = dns.rrset.from_text(zone, 0, 'IN', 'SOA', '. . %u 0 0 0 0' % serial) q.authority.append(rrset) if keyring is not None: q.use_tsig(keyring, keyname, algorithm=keyalgorithm) wire = q.to_wire() (af, destination, source) = _destination_and_source(af, where, port, source, source_port) if use_udp: if rdtype != dns.rdatatype.IXFR: raise ValueError('cannot do a UDP AXFR') s = socket_factory(af, socket.SOCK_DGRAM, 0) else: s = socket_factory(af, socket.SOCK_STREAM, 0) s.setblocking(0) if source is not None: s.bind(source) expiration = _compute_expiration(lifetime) _connect(s, destination) l = len(wire) if use_udp: _wait_for_writable(s, expiration) s.send(wire) else: tcpmsg = struct.pack("!H", l) + wire _net_write(s, tcpmsg, expiration) done = False delete_mode = True expecting_SOA = False soa_rrset = None if relativize: origin = zone oname = dns.name.empty else: origin = None oname = zone tsig_ctx = None first = True while not done: mexpiration = _compute_expiration(timeout) if mexpiration is None or \ (expiration is not None and mexpiration > expiration): mexpiration = expiration if use_udp: _wait_for_readable(s, expiration) (wire, from_address) = s.recvfrom(65535) else: ldata = _net_read(s, 2, mexpiration) (l,) = struct.unpack("!H", ldata) wire = _net_read(s, l, mexpiration) is_ixfr = (rdtype == dns.rdatatype.IXFR) r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac, xfr=True, origin=origin, tsig_ctx=tsig_ctx, multi=True, first=first, one_rr_per_rrset=is_ixfr) tsig_ctx = r.tsig_ctx first = False answer_index = 0 if soa_rrset is None: if not r.answer or r.answer[0].name != oname: raise dns.exception.FormError( "No answer or RRset not for qname") rrset = r.answer[0] if rrset.rdtype != dns.rdatatype.SOA: raise dns.exception.FormError("first RRset is not an SOA") answer_index = 1 soa_rrset = rrset.copy() if rdtype == dns.rdatatype.IXFR: if soa_rrset[0].serial <= serial: # # We're already up-to-date. # done = True else: expecting_SOA = True # # Process SOAs in the answer section (other than the initial # SOA in the first message). # for rrset in r.answer[answer_index:]: if done: raise dns.exception.FormError("answers after final SOA") if rrset.rdtype == dns.rdatatype.SOA and rrset.name == oname: if expecting_SOA: if rrset[0].serial != serial: raise dns.exception.FormError( "IXFR base serial mismatch") expecting_SOA = False elif rdtype == dns.rdatatype.IXFR: delete_mode = not delete_mode # # If this SOA RRset is equal to the first we saw then we're # finished. If this is an IXFR we also check that we're seeing # the record in the expected part of the response. # if rrset == soa_rrset and \ (rdtype == dns.rdatatype.AXFR or (rdtype == dns.rdatatype.IXFR and delete_mode)): done = True elif expecting_SOA: # # We made an IXFR request and are expecting another # SOA RR, but saw something else, so this must be an # AXFR response. # rdtype = dns.rdatatype.AXFR expecting_SOA = False if done and q.keyring and not r.had_tsig: raise dns.exception.FormError("missing TSIG") yield r s.close()
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