chiark / gitweb /
httpauth.py: Don't crash if Base-64 decoding of the CSRF token fails.
[chopwood] / crypto.py
CommitLineData
a2916c06
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1### -*-python-*-
2###
3### Cryptographic primitives
4###
5### (c) 2013 Mark Wooding
6###
7
8###----- Licensing notice ---------------------------------------------------
9###
10### This file is part of Chopwood: a password-changing service.
11###
12### Chopwood is free software; you can redistribute it and/or modify
13### it under the terms of the GNU Affero General Public License as
14### published by the Free Software Foundation; either version 3 of the
15### License, or (at your option) any later version.
16###
17### Chopwood is distributed in the hope that it will be useful,
18### but WITHOUT ANY WARRANTY; without even the implied warranty of
19### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
20### GNU Affero General Public License for more details.
21###
22### You should have received a copy of the GNU Affero General Public
23### License along with Chopwood; if not, see
24### <http://www.gnu.org/licenses/>.
25
cc56a4cf
MW
26from struct import pack, unpack
27
a2916c06
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28###--------------------------------------------------------------------------
29### The core of MD5.
30
31def U32(x): return x&0xffffffff
32def FF(x, y, z): return (x&y) | (~x&z)
33def GG(x, y, z): return (z&x) | (~z&y)
34def HH(x, y, z): return x^y^z
35def II(x, y, z): return y^(x|~z)
36def rot(x, n): return U32((x << n) | (x >> 32 - n))
37MD5_INIT = '0123456789abcdeffedcba9876543210'.decode('hex')
38def compress_md5(buf, st = MD5_INIT):
39 """
40 The MD5 compression function, in pure Python.
41
42 This is about as small as I could make it. Apply the MD5 compression
43 function to BUF, using the initial state ST (defaults to the standard
44 initialization vector); return the new state as the function value.
45 """
46 a, b, c, d = unpack('<4L', st)
47 aa, bb, cc, dd = a, b, c, d
48 x = xx = unpack('<16L', buf)
49 for f, i, r, k in [(FF, 0, 7, 0xd76aa478), (FF, 1, 12, 0xe8c7b756),
50 (FF, 2, 17, 0x242070db), (FF, 3, 22, 0xc1bdceee),
51 (FF, 4, 7, 0xf57c0faf), (FF, 5, 12, 0x4787c62a),
52 (FF, 6, 17, 0xa8304613), (FF, 7, 22, 0xfd469501),
53 (FF, 8, 7, 0x698098d8), (FF, 9, 12, 0x8b44f7af),
54 (FF, 10, 17, 0xffff5bb1), (FF, 11, 22, 0x895cd7be),
55 (FF, 12, 7, 0x6b901122), (FF, 13, 12, 0xfd987193),
56 (FF, 14, 17, 0xa679438e), (FF, 15, 22, 0x49b40821),
57 (GG, 1, 5, 0xf61e2562), (GG, 6, 9, 0xc040b340),
58 (GG, 11, 14, 0x265e5a51), (GG, 0, 20, 0xe9b6c7aa),
59 (GG, 5, 5, 0xd62f105d), (GG, 10, 9, 0x02441453),
60 (GG, 15, 14, 0xd8a1e681), (GG, 4, 20, 0xe7d3fbc8),
61 (GG, 9, 5, 0x21e1cde6), (GG, 14, 9, 0xc33707d6),
62 (GG, 3, 14, 0xf4d50d87), (GG, 8, 20, 0x455a14ed),
63 (GG, 13, 5, 0xa9e3e905), (GG, 2, 9, 0xfcefa3f8),
64 (GG, 7, 14, 0x676f02d9), (GG, 12, 20, 0x8d2a4c8a),
65 (HH, 5, 4, 0xfffa3942), (HH, 8, 11, 0x8771f681),
66 (HH, 11, 16, 0x6d9d6122), (HH, 14, 23, 0xfde5380c),
67 (HH, 1, 4, 0xa4beea44), (HH, 4, 11, 0x4bdecfa9),
68 (HH, 7, 16, 0xf6bb4b60), (HH, 10, 23, 0xbebfbc70),
69 (HH, 13, 4, 0x289b7ec6), (HH, 0, 11, 0xeaa127fa),
70 (HH, 3, 16, 0xd4ef3085), (HH, 6, 23, 0x04881d05),
71 (HH, 9, 4, 0xd9d4d039), (HH, 12, 11, 0xe6db99e5),
72 (HH, 15, 16, 0x1fa27cf8), (HH, 2, 23, 0xc4ac5665),
73 (II, 0, 6, 0xf4292244), (II, 7, 10, 0x432aff97),
74 (II, 14, 15, 0xab9423a7), (II, 5, 21, 0xfc93a039),
75 (II, 12, 6, 0x655b59c3), (II, 3, 10, 0x8f0ccc92),
76 (II, 10, 15, 0xffeff47d), (II, 1, 21, 0x85845dd1),
77 (II, 8, 6, 0x6fa87e4f), (II, 15, 10, 0xfe2ce6e0),
78 (II, 6, 15, 0xa3014314), (II, 13, 21, 0x4e0811a1),
79 (II, 4, 6, 0xf7537e82), (II, 11, 10, 0xbd3af235),
80 (II, 2, 15, 0x2ad7d2bb), (II, 9, 21, 0xeb86d391)]:
81 b, c, d, a = U32(rot(U32(a + f(b, c, d) + x[i] + k), r) + b), b, c, d
82 return pack('<4L', U32(a + aa), U32(b + bb), U32(c + cc), U32(d + dd))
83
84###----- That's all, folks --------------------------------------------------