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
16import cStringIO
17
18import dns.exception
19import dns.rdata
20import dns.rdatatype
21import dns.name
22
23class 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