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      1 # Copyright (C) 2004-2007, 2009, 2010 Nominum, Inc.
      2 #
      3 # Permission to use, copy, modify, and distribute this software and its
      4 # documentation for any purpose with or without fee is hereby granted,
      5 # provided that the above copyright notice and this permission notice
      6 # appear in all copies.
      7 #
      8 # THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
      9 # WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
     10 # MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
     11 # ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
     12 # WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
     13 # ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
     14 # OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
     15 
     16 import cStringIO
     17 
     18 import dns.exception
     19 import dns.rdata
     20 import dns.rdatatype
     21 import dns.name
     22 
     23 class NSEC(dns.rdata.Rdata):
     24     """NSEC record
     25 
     26     @ivar next: the next name
     27     @type next: dns.name.Name object
     28     @ivar windows: the windowed bitmap list
     29     @type windows: list of (window number, string) tuples"""
     30 
     31     __slots__ = ['next', 'windows']
     32 
     33     def __init__(self, rdclass, rdtype, next, windows):
     34         super(NSEC, self).__init__(rdclass, rdtype)
     35         self.next = next
     36         self.windows = windows
     37 
     38     def to_text(self, origin=None, relativize=True, **kw):
     39         next = self.next.choose_relativity(origin, relativize)
     40         text = ''
     41         for (window, bitmap) in self.windows:
     42             bits = []
     43             for i in xrange(0, len(bitmap)):
     44                 byte = ord(bitmap[i])
     45                 for j in xrange(0, 8):
     46                     if byte & (0x80 >> j):
     47                         bits.append(dns.rdatatype.to_text(window * 256 + \
     48                                                           i * 8 + j))
     49             text += (' ' + ' '.join(bits))
     50         return '%s%s' % (next, text)
     51 
     52     def from_text(cls, rdclass, rdtype, tok, origin = None, relativize = True):
     53         next = tok.get_name()
     54         next = next.choose_relativity(origin, relativize)
     55         rdtypes = []
     56         while 1:
     57             token = tok.get().unescape()
     58             if token.is_eol_or_eof():
     59                 break
     60             nrdtype = dns.rdatatype.from_text(token.value)
     61             if nrdtype == 0:
     62                 raise dns.exception.SyntaxError("NSEC with bit 0")
     63             if nrdtype > 65535:
     64                 raise dns.exception.SyntaxError("NSEC with bit > 65535")
     65             rdtypes.append(nrdtype)
     66         rdtypes.sort()
     67         window = 0
     68         octets = 0
     69         prior_rdtype = 0
     70         bitmap = ['\0'] * 32
     71         windows = []
     72         for nrdtype in rdtypes:
     73             if nrdtype == prior_rdtype:
     74                 continue
     75             prior_rdtype = nrdtype
     76             new_window = nrdtype // 256
     77             if new_window != window:
     78                 windows.append((window, ''.join(bitmap[0:octets])))
     79                 bitmap = ['\0'] * 32
     80                 window = new_window
     81             offset = nrdtype % 256
     82             byte = offset / 8
     83             bit = offset % 8
     84             octets = byte + 1
     85             bitmap[byte] = chr(ord(bitmap[byte]) | (0x80 >> bit))
     86         windows.append((window, ''.join(bitmap[0:octets])))
     87         return cls(rdclass, rdtype, next, windows)
     88 
     89     from_text = classmethod(from_text)
     90 
     91     def to_wire(self, file, compress = None, origin = None):
     92         self.next.to_wire(file, None, origin)
     93         for (window, bitmap) in self.windows:
     94             file.write(chr(window))
     95             file.write(chr(len(bitmap)))
     96             file.write(bitmap)
     97 
     98     def from_wire(cls, rdclass, rdtype, wire, current, rdlen, origin = None):
     99         (next, cused) = dns.name.from_wire(wire[: current + rdlen], current)
    100         current += cused
    101         rdlen -= cused
    102         windows = []
    103         while rdlen > 0:
    104             if rdlen < 3:
    105                 raise dns.exception.FormError("NSEC too short")
    106             window = ord(wire[current])
    107             octets = ord(wire[current + 1])
    108             if octets == 0 or octets > 32:
    109                 raise dns.exception.FormError("bad NSEC octets")
    110             current += 2
    111             rdlen -= 2
    112             if rdlen < octets:
    113                 raise dns.exception.FormError("bad NSEC bitmap length")
    114             bitmap = wire[current : current + octets]
    115             current += octets
    116             rdlen -= octets
    117             windows.append((window, bitmap))
    118         if not origin is None:
    119             next = next.relativize(origin)
    120         return cls(rdclass, rdtype, next, windows)
    121 
    122     from_wire = classmethod(from_wire)
    123 
    124     def choose_relativity(self, origin = None, relativize = True):
    125         self.next = self.next.choose_relativity(origin, relativize)
    126 
    127     def _cmp(self, other):
    128         v = cmp(self.next, other.next)
    129         if v == 0:
    130             b1 = cStringIO.StringIO()
    131             for (window, bitmap) in self.windows:
    132                 b1.write(chr(window))
    133                 b1.write(chr(len(bitmap)))
    134                 b1.write(bitmap)
    135             b2 = cStringIO.StringIO()
    136             for (window, bitmap) in other.windows:
    137                 b2.write(chr(window))
    138                 b2.write(chr(len(bitmap)))
    139                 b2.write(bitmap)
    140             v = cmp(b1.getvalue(), b2.getvalue())
    141         return v
    142