| 1 | # Copyright (C) 2003-2007, 2009, 2010 Nominum, Inc.
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| 2 | #
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| 3 | # Permission to use, copy, modify, and distribute this software and its
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| 4 | # documentation for any purpose with or without fee is hereby granted,
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| 5 | # provided that the above copyright notice and this permission notice
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| 6 | # appear in all copies.
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| 7 | #
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| 8 | # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
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| 9 | # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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| 10 | # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
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| 11 | # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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| 12 | # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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| 13 | # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
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| 14 | # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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| 15 |
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| 16 | """Talk to a DNS server."""
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| 17 |
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| 18 | from __future__ import generators
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| 19 |
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| 20 | import errno
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| 21 | import select
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| 22 | import socket
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| 23 | import struct
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| 24 | import sys
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| 25 | import time
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| 26 |
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| 27 | import dns.exception
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| 28 | import dns.inet
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| 29 | import dns.name
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| 30 | import dns.message
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| 31 | import dns.rdataclass
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| 32 | import dns.rdatatype
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| 33 |
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| 34 | class UnexpectedSource(dns.exception.DNSException):
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| 35 | """Raised if a query response comes from an unexpected address or port."""
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| 36 | pass
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| 37 |
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| 38 | class BadResponse(dns.exception.FormError):
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| 39 | """Raised if a query response does not respond to the question asked."""
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| 40 | pass
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| 41 |
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| 42 | def _compute_expiration(timeout):
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| 43 | if timeout is None:
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| 44 | return None
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| 45 | else:
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| 46 | return time.time() + timeout
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| 47 |
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| 48 | def _poll_for(fd, readable, writable, error, timeout):
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| 49 | """
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| 50 | @param fd: File descriptor (int).
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| 51 | @param readable: Whether to wait for readability (bool).
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| 52 | @param writable: Whether to wait for writability (bool).
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| 53 | @param expiration: Deadline timeout (expiration time, in seconds (float)).
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| 54 |
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| 55 | @return True on success, False on timeout
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| 56 | """
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| 57 | event_mask = 0
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| 58 | if readable:
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| 59 | event_mask |= select.POLLIN
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| 60 | if writable:
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| 61 | event_mask |= select.POLLOUT
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| 62 | if error:
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| 63 | event_mask |= select.POLLERR
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| 64 |
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| 65 | pollable = select.poll()
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| 66 | pollable.register(fd, event_mask)
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| 67 |
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| 68 | if timeout:
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| 69 | event_list = pollable.poll(long(timeout * 1000))
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| 70 | else:
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| 71 | event_list = pollable.poll()
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| 72 |
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| 73 | return bool(event_list)
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| 74 |
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| 75 | def _select_for(fd, readable, writable, error, timeout):
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| 76 | """
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| 77 | @param fd: File descriptor (int).
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| 78 | @param readable: Whether to wait for readability (bool).
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| 79 | @param writable: Whether to wait for writability (bool).
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| 80 | @param expiration: Deadline timeout (expiration time, in seconds (float)).
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| 81 |
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| 82 | @return True on success, False on timeout
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| 83 | """
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| 84 | rset, wset, xset = [], [], []
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| 85 |
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| 86 | if readable:
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| 87 | rset = [fd]
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| 88 | if writable:
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| 89 | wset = [fd]
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| 90 | if error:
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| 91 | xset = [fd]
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| 92 |
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| 93 | if timeout is None:
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| 94 | (rcount, wcount, xcount) = select.select(rset, wset, xset)
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| 95 | else:
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| 96 | (rcount, wcount, xcount) = select.select(rset, wset, xset, timeout)
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| 97 |
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| 98 | return bool((rcount or wcount or xcount))
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| 99 |
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| 100 | def _wait_for(fd, readable, writable, error, expiration):
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| 101 | done = False
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| 102 | while not done:
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| 103 | if expiration is None:
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| 104 | timeout = None
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| 105 | else:
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| 106 | timeout = expiration - time.time()
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| 107 | if timeout <= 0.0:
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| 108 | raise dns.exception.Timeout
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| 109 | try:
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| 110 | if not _polling_backend(fd, readable, writable, error, timeout):
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| 111 | raise dns.exception.Timeout
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| 112 | except select.error, e:
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| 113 | if e.args[0] != errno.EINTR:
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| 114 | raise e
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| 115 | done = True
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| 116 |
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| 117 | def _set_polling_backend(fn):
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| 118 | """
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| 119 | Internal API. Do not use.
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| 120 | """
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| 121 | global _polling_backend
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| 122 |
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| 123 | _polling_backend = fn
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| 124 |
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| 125 | if hasattr(select, 'poll'):
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| 126 | # Prefer poll() on platforms that support it because it has no
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| 127 | # limits on the maximum value of a file descriptor (plus it will
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| 128 | # be more efficient for high values).
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| 129 | _polling_backend = _poll_for
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| 130 | else:
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| 131 | _polling_backend = _select_for
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| 132 |
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| 133 | def _wait_for_readable(s, expiration):
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| 134 | _wait_for(s, True, False, True, expiration)
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| 135 |
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| 136 | def _wait_for_writable(s, expiration):
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| 137 | _wait_for(s, False, True, True, expiration)
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| 138 |
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| 139 | def _addresses_equal(af, a1, a2):
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| 140 | # Convert the first value of the tuple, which is a textual format
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| 141 | # address into binary form, so that we are not confused by different
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| 142 | # textual representations of the same address
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| 143 | n1 = dns.inet.inet_pton(af, a1[0])
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| 144 | n2 = dns.inet.inet_pton(af, a2[0])
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| 145 | return n1 == n2 and a1[1:] == a2[1:]
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| 146 |
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| 147 | def udp(q, where, timeout=None, port=53, af=None, source=None, source_port=0,
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| 148 | ignore_unexpected=False, one_rr_per_rrset=False):
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| 149 | """Return the response obtained after sending a query via UDP.
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| 150 |
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| 151 | @param q: the query
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| 152 | @type q: dns.message.Message
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| 153 | @param where: where to send the message
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| 154 | @type where: string containing an IPv4 or IPv6 address
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| 155 | @param timeout: The number of seconds to wait before the query times out.
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| 156 | If None, the default, wait forever.
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| 157 | @type timeout: float
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| 158 | @param port: The port to which to send the message. The default is 53.
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| 159 | @type port: int
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| 160 | @param af: the address family to use. The default is None, which
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| 161 | causes the address family to use to be inferred from the form of of where.
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| 162 | If the inference attempt fails, AF_INET is used.
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| 163 | @type af: int
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| 164 | @rtype: dns.message.Message object
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| 165 | @param source: source address. The default is the IPv4 wildcard address.
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| 166 | @type source: string
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| 167 | @param source_port: The port from which to send the message.
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| 168 | The default is 0.
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| 169 | @type source_port: int
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| 170 | @param ignore_unexpected: If True, ignore responses from unexpected
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| 171 | sources. The default is False.
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| 172 | @type ignore_unexpected: bool
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| 173 | @param one_rr_per_rrset: Put each RR into its own RRset
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| 174 | @type one_rr_per_rrset: bool
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| 175 | """
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| 176 |
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| 177 | wire = q.to_wire()
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| 178 | if af is None:
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| 179 | try:
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| 180 | af = dns.inet.af_for_address(where)
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| 181 | except:
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| 182 | af = dns.inet.AF_INET
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| 183 | if af == dns.inet.AF_INET:
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| 184 | destination = (where, port)
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| 185 | if source is not None:
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| 186 | source = (source, source_port)
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| 187 | elif af == dns.inet.AF_INET6:
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| 188 | destination = (where, port, 0, 0)
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| 189 | if source is not None:
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| 190 | source = (source, source_port, 0, 0)
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| 191 | s = socket.socket(af, socket.SOCK_DGRAM, 0)
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| 192 | try:
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| 193 | expiration = _compute_expiration(timeout)
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| 194 | s.setblocking(0)
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| 195 | if source is not None:
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| 196 | s.bind(source)
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| 197 | _wait_for_writable(s, expiration)
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| 198 | s.sendto(wire, destination)
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| 199 | while 1:
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| 200 | _wait_for_readable(s, expiration)
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| 201 | (wire, from_address) = s.recvfrom(65535)
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| 202 | if _addresses_equal(af, from_address, destination) or \
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| 203 | (dns.inet.is_multicast(where) and \
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| 204 | from_address[1:] == destination[1:]):
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| 205 | break
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| 206 | if not ignore_unexpected:
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| 207 | raise UnexpectedSource('got a response from '
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| 208 | '%s instead of %s' % (from_address,
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| 209 | destination))
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| 210 | finally:
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| 211 | s.close()
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| 212 | r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
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| 213 | one_rr_per_rrset=one_rr_per_rrset)
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| 214 | if not q.is_response(r):
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| 215 | raise BadResponse
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| 216 | return r
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| 217 |
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| 218 | def _net_read(sock, count, expiration):
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| 219 | """Read the specified number of bytes from sock. Keep trying until we
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| 220 | either get the desired amount, or we hit EOF.
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| 221 | A Timeout exception will be raised if the operation is not completed
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| 222 | by the expiration time.
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| 223 | """
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| 224 | s = ''
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| 225 | while count > 0:
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| 226 | _wait_for_readable(sock, expiration)
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| 227 | n = sock.recv(count)
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| 228 | if n == '':
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| 229 | raise EOFError
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| 230 | count = count - len(n)
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| 231 | s = s + n
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| 232 | return s
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| 233 |
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| 234 | def _net_write(sock, data, expiration):
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| 235 | """Write the specified data to the socket.
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| 236 | A Timeout exception will be raised if the operation is not completed
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| 237 | by the expiration time.
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| 238 | """
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| 239 | current = 0
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| 240 | l = len(data)
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| 241 | while current < l:
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| 242 | _wait_for_writable(sock, expiration)
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| 243 | current += sock.send(data[current:])
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| 244 |
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| 245 | def _connect(s, address):
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| 246 | try:
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| 247 | s.connect(address)
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| 248 | except socket.error:
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| 249 | (ty, v) = sys.exc_info()[:2]
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| 250 | if v[0] != errno.EINPROGRESS and \
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| 251 | v[0] != errno.EWOULDBLOCK and \
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| 252 | v[0] != errno.EALREADY:
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| 253 | raise v
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| 254 |
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| 255 | def tcp(q, where, timeout=None, port=53, af=None, source=None, source_port=0,
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| 256 | one_rr_per_rrset=False):
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| 257 | """Return the response obtained after sending a query via TCP.
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| 258 |
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| 259 | @param q: the query
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| 260 | @type q: dns.message.Message object
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| 261 | @param where: where to send the message
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| 262 | @type where: string containing an IPv4 or IPv6 address
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| 263 | @param timeout: The number of seconds to wait before the query times out.
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| 264 | If None, the default, wait forever.
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| 265 | @type timeout: float
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| 266 | @param port: The port to which to send the message. The default is 53.
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| 267 | @type port: int
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| 268 | @param af: the address family to use. The default is None, which
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| 269 | causes the address family to use to be inferred from the form of of where.
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| 270 | If the inference attempt fails, AF_INET is used.
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| 271 | @type af: int
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| 272 | @rtype: dns.message.Message object
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| 273 | @param source: source address. The default is the IPv4 wildcard address.
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| 274 | @type source: string
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| 275 | @param source_port: The port from which to send the message.
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| 276 | The default is 0.
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| 277 | @type source_port: int
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| 278 | @param one_rr_per_rrset: Put each RR into its own RRset
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| 279 | @type one_rr_per_rrset: bool
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| 280 | """
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| 281 |
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| 282 | wire = q.to_wire()
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| 283 | if af is None:
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| 284 | try:
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| 285 | af = dns.inet.af_for_address(where)
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| 286 | except:
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| 287 | af = dns.inet.AF_INET
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| 288 | if af == dns.inet.AF_INET:
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| 289 | destination = (where, port)
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| 290 | if source is not None:
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| 291 | source = (source, source_port)
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| 292 | elif af == dns.inet.AF_INET6:
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| 293 | destination = (where, port, 0, 0)
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| 294 | if source is not None:
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| 295 | source = (source, source_port, 0, 0)
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| 296 | s = socket.socket(af, socket.SOCK_STREAM, 0)
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| 297 | try:
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| 298 | expiration = _compute_expiration(timeout)
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| 299 | s.setblocking(0)
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| 300 | if source is not None:
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| 301 | s.bind(source)
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| 302 | _connect(s, destination)
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| 303 |
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| 304 | l = len(wire)
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| 305 |
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| 306 | # copying the wire into tcpmsg is inefficient, but lets us
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| 307 | # avoid writev() or doing a short write that would get pushed
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| 308 | # onto the net
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| 309 | tcpmsg = struct.pack("!H", l) + wire
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| 310 | _net_write(s, tcpmsg, expiration)
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| 311 | ldata = _net_read(s, 2, expiration)
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| 312 | (l,) = struct.unpack("!H", ldata)
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| 313 | wire = _net_read(s, l, expiration)
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| 314 | finally:
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| 315 | s.close()
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| 316 | r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
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| 317 | one_rr_per_rrset=one_rr_per_rrset)
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| 318 | if not q.is_response(r):
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| 319 | raise BadResponse
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| 320 | return r
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| 321 |
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| 322 | def xfr(where, zone, rdtype=dns.rdatatype.AXFR, rdclass=dns.rdataclass.IN,
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| 323 | timeout=None, port=53, keyring=None, keyname=None, relativize=True,
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| 324 | af=None, lifetime=None, source=None, source_port=0, serial=0,
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| 325 | use_udp=False, keyalgorithm=dns.tsig.default_algorithm):
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| 326 | """Return a generator for the responses to a zone transfer.
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| 327 |
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| 328 | @param where: where to send the message
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| 329 | @type where: string containing an IPv4 or IPv6 address
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| 330 | @param zone: The name of the zone to transfer
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| 331 | @type zone: dns.name.Name object or string
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| 332 | @param rdtype: The type of zone transfer. The default is
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| 333 | dns.rdatatype.AXFR.
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| 334 | @type rdtype: int or string
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| 335 | @param rdclass: The class of the zone transfer. The default is
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| 336 | dns.rdatatype.IN.
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| 337 | @type rdclass: int or string
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| 338 | @param timeout: The number of seconds to wait for each response message.
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| 339 | If None, the default, wait forever.
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| 340 | @type timeout: float
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| 341 | @param port: The port to which to send the message. The default is 53.
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| 342 | @type port: int
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| 343 | @param keyring: The TSIG keyring to use
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| 344 | @type keyring: dict
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| 345 | @param keyname: The name of the TSIG key to use
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| 346 | @type keyname: dns.name.Name object or string
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| 347 | @param relativize: If True, all names in the zone will be relativized to
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| 348 | the zone origin. It is essential that the relativize setting matches
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| 349 | the one specified to dns.zone.from_xfr().
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| 350 | @type relativize: bool
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| 351 | @param af: the address family to use. The default is None, which
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| 352 | causes the address family to use to be inferred from the form of of where.
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| 353 | If the inference attempt fails, AF_INET is used.
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| 354 | @type af: int
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| 355 | @param lifetime: The total number of seconds to spend doing the transfer.
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| 356 | If None, the default, then there is no limit on the time the transfer may
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| 357 | take.
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| 358 | @type lifetime: float
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| 359 | @rtype: generator of dns.message.Message objects.
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| 360 | @param source: source address. The default is the IPv4 wildcard address.
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| 361 | @type source: string
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| 362 | @param source_port: The port from which to send the message.
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| 363 | The default is 0.
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| 364 | @type source_port: int
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| 365 | @param serial: The SOA serial number to use as the base for an IXFR diff
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| 366 | sequence (only meaningful if rdtype == dns.rdatatype.IXFR).
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| 367 | @type serial: int
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| 368 | @param use_udp: Use UDP (only meaningful for IXFR)
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| 369 | @type use_udp: bool
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| 370 | @param keyalgorithm: The TSIG algorithm to use; defaults to
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| 371 | dns.tsig.default_algorithm
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| 372 | @type keyalgorithm: string
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| 373 | """
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| 374 |
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| 375 | if isinstance(zone, (str, unicode)):
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| 376 | zone = dns.name.from_text(zone)
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| 377 | if isinstance(rdtype, (str, unicode)):
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| 378 | rdtype = dns.rdatatype.from_text(rdtype)
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| 379 | q = dns.message.make_query(zone, rdtype, rdclass)
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| 380 | if rdtype == dns.rdatatype.IXFR:
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| 381 | rrset = dns.rrset.from_text(zone, 0, 'IN', 'SOA',
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| 382 | '. . %u 0 0 0 0' % serial)
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| 383 | q.authority.append(rrset)
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| 384 | if not keyring is None:
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| 385 | q.use_tsig(keyring, keyname, algorithm=keyalgorithm)
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| 386 | wire = q.to_wire()
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| 387 | if af is None:
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| 388 | try:
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| 389 | af = dns.inet.af_for_address(where)
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| 390 | except:
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| 391 | af = dns.inet.AF_INET
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| 392 | if af == dns.inet.AF_INET:
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| 393 | destination = (where, port)
|
|---|
| 394 | if source is not None:
|
|---|
| 395 | source = (source, source_port)
|
|---|
| 396 | elif af == dns.inet.AF_INET6:
|
|---|
| 397 | destination = (where, port, 0, 0)
|
|---|
| 398 | if source is not None:
|
|---|
| 399 | source = (source, source_port, 0, 0)
|
|---|
| 400 | if use_udp:
|
|---|
| 401 | if rdtype != dns.rdatatype.IXFR:
|
|---|
| 402 | raise ValueError('cannot do a UDP AXFR')
|
|---|
| 403 | s = socket.socket(af, socket.SOCK_DGRAM, 0)
|
|---|
| 404 | else:
|
|---|
| 405 | s = socket.socket(af, socket.SOCK_STREAM, 0)
|
|---|
| 406 | s.setblocking(0)
|
|---|
| 407 | if source is not None:
|
|---|
| 408 | s.bind(source)
|
|---|
| 409 | expiration = _compute_expiration(lifetime)
|
|---|
| 410 | _connect(s, destination)
|
|---|
| 411 | l = len(wire)
|
|---|
| 412 | if use_udp:
|
|---|
| 413 | _wait_for_writable(s, expiration)
|
|---|
| 414 | s.send(wire)
|
|---|
| 415 | else:
|
|---|
| 416 | tcpmsg = struct.pack("!H", l) + wire
|
|---|
| 417 | _net_write(s, tcpmsg, expiration)
|
|---|
| 418 | done = False
|
|---|
| 419 | soa_rrset = None
|
|---|
| 420 | soa_count = 0
|
|---|
| 421 | if relativize:
|
|---|
| 422 | origin = zone
|
|---|
| 423 | oname = dns.name.empty
|
|---|
| 424 | else:
|
|---|
| 425 | origin = None
|
|---|
| 426 | oname = zone
|
|---|
| 427 | tsig_ctx = None
|
|---|
| 428 | first = True
|
|---|
| 429 | while not done:
|
|---|
| 430 | mexpiration = _compute_expiration(timeout)
|
|---|
| 431 | if mexpiration is None or mexpiration > expiration:
|
|---|
| 432 | mexpiration = expiration
|
|---|
| 433 | if use_udp:
|
|---|
| 434 | _wait_for_readable(s, expiration)
|
|---|
| 435 | (wire, from_address) = s.recvfrom(65535)
|
|---|
| 436 | else:
|
|---|
| 437 | ldata = _net_read(s, 2, mexpiration)
|
|---|
| 438 | (l,) = struct.unpack("!H", ldata)
|
|---|
| 439 | wire = _net_read(s, l, mexpiration)
|
|---|
| 440 | r = dns.message.from_wire(wire, keyring=q.keyring, request_mac=q.mac,
|
|---|
| 441 | xfr=True, origin=origin, tsig_ctx=tsig_ctx,
|
|---|
| 442 | multi=True, first=first,
|
|---|
| 443 | one_rr_per_rrset=(rdtype==dns.rdatatype.IXFR))
|
|---|
| 444 | tsig_ctx = r.tsig_ctx
|
|---|
| 445 | first = False
|
|---|
| 446 | answer_index = 0
|
|---|
| 447 | delete_mode = False
|
|---|
| 448 | expecting_SOA = False
|
|---|
| 449 | if soa_rrset is None:
|
|---|
| 450 | if not r.answer or r.answer[0].name != oname:
|
|---|
| 451 | raise dns.exception.FormError
|
|---|
| 452 | rrset = r.answer[0]
|
|---|
| 453 | if rrset.rdtype != dns.rdatatype.SOA:
|
|---|
| 454 | raise dns.exception.FormError("first RRset is not an SOA")
|
|---|
| 455 | answer_index = 1
|
|---|
| 456 | soa_rrset = rrset.copy()
|
|---|
| 457 | if rdtype == dns.rdatatype.IXFR:
|
|---|
| 458 | if soa_rrset[0].serial == serial:
|
|---|
| 459 | #
|
|---|
| 460 | # We're already up-to-date.
|
|---|
| 461 | #
|
|---|
| 462 | done = True
|
|---|
| 463 | else:
|
|---|
| 464 | expecting_SOA = True
|
|---|
| 465 | #
|
|---|
| 466 | # Process SOAs in the answer section (other than the initial
|
|---|
| 467 | # SOA in the first message).
|
|---|
| 468 | #
|
|---|
| 469 | for rrset in r.answer[answer_index:]:
|
|---|
| 470 | if done:
|
|---|
| 471 | raise dns.exception.FormError("answers after final SOA")
|
|---|
| 472 | if rrset.rdtype == dns.rdatatype.SOA and rrset.name == oname:
|
|---|
| 473 | if expecting_SOA:
|
|---|
| 474 | if rrset[0].serial != serial:
|
|---|
| 475 | raise dns.exception.FormError("IXFR base serial mismatch")
|
|---|
| 476 | expecting_SOA = False
|
|---|
| 477 | elif rdtype == dns.rdatatype.IXFR:
|
|---|
| 478 | delete_mode = not delete_mode
|
|---|
| 479 | if rrset == soa_rrset and not delete_mode:
|
|---|
| 480 | done = True
|
|---|
| 481 | elif expecting_SOA:
|
|---|
| 482 | #
|
|---|
| 483 | # We made an IXFR request and are expecting another
|
|---|
| 484 | # SOA RR, but saw something else, so this must be an
|
|---|
| 485 | # AXFR response.
|
|---|
| 486 | #
|
|---|
| 487 | rdtype = dns.rdatatype.AXFR
|
|---|
| 488 | expecting_SOA = False
|
|---|
| 489 | if done and q.keyring and not r.had_tsig:
|
|---|
| 490 | raise dns.exception.FormError("missing TSIG")
|
|---|
| 491 | yield r
|
|---|
| 492 | s.close()
|
|---|
