1# Copyright (C) Dnspython Contributors, see LICENSE for text of ISC license
2
3# Copyright (C) 2003-2017 Nominum, Inc.
4#
5# Permission to use, copy, modify, and distribute this software and its
6# documentation for any purpose with or without fee is hereby granted,
7# provided that the above copyright notice and this permission notice
8# appear in all copies.
9#
10# THE SOFTWARE IS PROVIDED "AS IS" AND NOMINUM DISCLAIMS ALL WARRANTIES
11# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
12# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL NOMINUM BE LIABLE FOR
13# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
14# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
15# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT
16# OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
17
18"""IPv6 helper functions."""
19
20import re
21import binascii
22
23import dns.exception
24import dns.ipv4
25
26_leading_zero = re.compile(r'0+([0-9a-f]+)')
27
28def inet_ntoa(address):
29    """Convert an IPv6 address in binary form to text form.
30
31    *address*, a ``bytes``, the IPv6 address in binary form.
32
33    Raises ``ValueError`` if the address isn't 16 bytes long.
34    Returns a ``str``.
35    """
36
37    if len(address) != 16:
38        raise ValueError("IPv6 addresses are 16 bytes long")
39    hex = binascii.hexlify(address)
40    chunks = []
41    i = 0
42    l = len(hex)
43    while i < l:
44        chunk = hex[i:i + 4].decode()
45        # strip leading zeros.  we do this with an re instead of
46        # with lstrip() because lstrip() didn't support chars until
47        # python 2.2.2
48        m = _leading_zero.match(chunk)
49        if m is not None:
50            chunk = m.group(1)
51        chunks.append(chunk)
52        i += 4
53    #
54    # Compress the longest subsequence of 0-value chunks to ::
55    #
56    best_start = 0
57    best_len = 0
58    start = -1
59    last_was_zero = False
60    for i in range(8):
61        if chunks[i] != '0':
62            if last_was_zero:
63                end = i
64                current_len = end - start
65                if current_len > best_len:
66                    best_start = start
67                    best_len = current_len
68                last_was_zero = False
69        elif not last_was_zero:
70            start = i
71            last_was_zero = True
72    if last_was_zero:
73        end = 8
74        current_len = end - start
75        if current_len > best_len:
76            best_start = start
77            best_len = current_len
78    if best_len > 1:
79        if best_start == 0 and \
80           (best_len == 6 or
81            best_len == 5 and chunks[5] == 'ffff'):
82            # We have an embedded IPv4 address
83            if best_len == 6:
84                prefix = '::'
85            else:
86                prefix = '::ffff:'
87            hex = prefix + dns.ipv4.inet_ntoa(address[12:])
88        else:
89            hex = ':'.join(chunks[:best_start]) + '::' + \
90                  ':'.join(chunks[best_start + best_len:])
91    else:
92        hex = ':'.join(chunks)
93    return hex
94
95_v4_ending = re.compile(br'(.*):(\d+\.\d+\.\d+\.\d+)$')
96_colon_colon_start = re.compile(br'::.*')
97_colon_colon_end = re.compile(br'.*::$')
98
99def inet_aton(text, ignore_scope=False):
100    """Convert an IPv6 address in text form to binary form.
101
102    *text*, a ``str``, the IPv6 address in textual form.
103
104    *ignore_scope*, a ``bool``.  If ``True``, a scope will be ignored.
105    If ``False``, the default, it is an error for a scope to be present.
106
107    Returns a ``bytes``.
108    """
109
110    #
111    # Our aim here is not something fast; we just want something that works.
112    #
113    if not isinstance(text, bytes):
114        text = text.encode()
115
116    if ignore_scope:
117        parts = text.split(b'%')
118        l = len(parts)
119        if l == 2:
120            text = parts[0]
121        elif l > 2:
122            raise dns.exception.SyntaxError
123
124    if text == b'::':
125        text = b'0::'
126    #
127    # Get rid of the icky dot-quad syntax if we have it.
128    #
129    m = _v4_ending.match(text)
130    if m is not None:
131        b = dns.ipv4.inet_aton(m.group(2))
132        text = (u"{}:{:02x}{:02x}:{:02x}{:02x}".format(m.group(1).decode(),
133                                                       b[0], b[1], b[2],
134                                                       b[3])).encode()
135    #
136    # Try to turn '::<whatever>' into ':<whatever>'; if no match try to
137    # turn '<whatever>::' into '<whatever>:'
138    #
139    m = _colon_colon_start.match(text)
140    if m is not None:
141        text = text[1:]
142    else:
143        m = _colon_colon_end.match(text)
144        if m is not None:
145            text = text[:-1]
146    #
147    # Now canonicalize into 8 chunks of 4 hex digits each
148    #
149    chunks = text.split(b':')
150    l = len(chunks)
151    if l > 8:
152        raise dns.exception.SyntaxError
153    seen_empty = False
154    canonical = []
155    for c in chunks:
156        if c == b'':
157            if seen_empty:
158                raise dns.exception.SyntaxError
159            seen_empty = True
160            for i in range(0, 8 - l + 1):
161                canonical.append(b'0000')
162        else:
163            lc = len(c)
164            if lc > 4:
165                raise dns.exception.SyntaxError
166            if lc != 4:
167                c = (b'0' * (4 - lc)) + c
168            canonical.append(c)
169    if l < 8 and not seen_empty:
170        raise dns.exception.SyntaxError
171    text = b''.join(canonical)
172
173    #
174    # Finally we can go to binary.
175    #
176    try:
177        return binascii.unhexlify(text)
178    except (binascii.Error, TypeError):
179        raise dns.exception.SyntaxError
180
181_mapped_prefix = b'\x00' * 10 + b'\xff\xff'
182
183def is_mapped(address):
184    """Is the specified address a mapped IPv4 address?
185
186    *address*, a ``bytes`` is an IPv6 address in binary form.
187
188    Returns a ``bool``.
189    """
190
191    return address.startswith(_mapped_prefix)
192