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1 | /* |
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2 | * PKCS#5 padding mechanism for udp tunnel |
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3 | * |
4 | * arguments: block size to pad to, must be power of 2 |
5 | * |
6 | * encoding: append between 1 and n bytes, all of the same value being |
7 | * the number of bytes appended |
8 | */ |
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9 | /* |
10 | * Copyright (C) 2000 Ian Jackson |
11 | * |
12 | * This is free software; you can redistribute it and/or modify it |
13 | * under the terms of the GNU General Public License as published by |
14 | * the Free Software Foundation; either version 2 of the License, or |
15 | * (at your option) any later version. |
16 | * |
17 | * This program is distributed in the hope that it will be useful, but |
18 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
20 | * General Public License for more details. |
21 | * |
22 | * You should have received a copy of the GNU General Public License |
23 | * along with userv-utils; if not, write to the Free Software |
24 | * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
25 | */ |
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26 | |
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27 | #include "forwarder.h" |
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28 | |
29 | struct mechdata { |
30 | unsigned mask; |
31 | }; |
32 | |
33 | static unsigned long setup(struct mechdata **md_r) { |
34 | struct mechdata *md; |
35 | unsigned long blocksize; |
36 | |
37 | XMALLOC(md); |
38 | |
39 | blocksize= getarg_ulong(); |
40 | md->mask= blocksize - 1; |
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41 | arg_assert(!(md->mask & blocksize)); |
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42 | arg_assert(blocksize <= 255); |
43 | |
44 | *md_r= md; |
45 | return blocksize; |
46 | } |
47 | |
48 | static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
49 | unsigned long blocksize; |
50 | |
51 | blocksize= setup(md_r); |
52 | *maxsuffix_io += blocksize + 1; |
53 | } |
54 | |
55 | static void mds_pkcs5(struct mechdata **md_r) { |
56 | setup(md_r); |
57 | } |
58 | |
59 | static void menc_pkcs5(struct mechdata *md, struct buffer *buf) { |
60 | unsigned char *pad; |
61 | int padlen; |
62 | |
63 | /* eg with blocksize=4 mask=3 mask+2=5 */ |
64 | /* msgsize 20 21 22 23 24 */ |
65 | padlen= md->mask - buf->size; /* -17 -18 -19 -16 -17 */ |
66 | padlen &= md->mask; /* 3 2 1 0 3 */ |
67 | padlen++; /* 4 3 2 1 4 */ |
68 | |
69 | pad= buf_append(buf,padlen); |
70 | memset(pad,padlen,padlen); |
71 | } |
72 | |
73 | static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) { |
74 | unsigned char *padp; |
75 | unsigned padlen; |
76 | int i; |
77 | |
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78 | BUF_UNAPPEND(padp,buf,1); |
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79 | padlen= *padp; |
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80 | if (!padlen || (padlen > md->mask+1)) return "invalid length"; |
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81 | |
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82 | BUF_UNAPPEND(padp,buf,padlen-1); |
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83 | for (i=0; i<padlen-1; i++) |
84 | if (*++padp != padlen) return "corrupted padding"; |
85 | |
86 | return 0; |
87 | } |
88 | |
89 | STANDARD_MECHANISMLIST("pkcs5",pkcs5) |