1fb3cba0 |
1 | /* |
f0e54a99 |
2 | * PKCS#5 padding mechanism for udp tunnel |
1fb3cba0 |
3 | * |
5124214b |
4 | * mechanism: pkcs5 |
5 | * arguments: block size to pad to, must be power of 2 and <=128 |
1fb3cba0 |
6 | * |
5124214b |
7 | * restrictions: none |
1fb3cba0 |
8 | * encoding: append between 1 and n bytes, all of the same value being |
9 | * the number of bytes appended |
10 | */ |
f0e54a99 |
11 | /* |
c07be359 |
12 | * Copyright (C) 2000,2003 Ian Jackson |
13 | * This file is part of ipif, part of userv-utils |
f0e54a99 |
14 | * |
15 | * This is free software; you can redistribute it and/or modify it |
16 | * under the terms of the GNU General Public License as published by |
17 | * the Free Software Foundation; either version 2 of the License, or |
18 | * (at your option) any later version. |
19 | * |
20 | * This program is distributed in the hope that it will be useful, but |
21 | * WITHOUT ANY WARRANTY; without even the implied warranty of |
22 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
23 | * General Public License for more details. |
24 | * |
25 | * You should have received a copy of the GNU General Public License |
26 | * along with userv-utils; if not, write to the Free Software |
27 | * Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
28 | */ |
1fb3cba0 |
29 | |
f9e59051 |
30 | #include "forwarder.h" |
1fb3cba0 |
31 | |
32 | struct mechdata { |
33 | unsigned mask; |
34 | }; |
35 | |
36 | static unsigned long setup(struct mechdata **md_r) { |
37 | struct mechdata *md; |
38 | unsigned long blocksize; |
39 | |
40 | XMALLOC(md); |
41 | |
42 | blocksize= getarg_ulong(); |
43 | md->mask= blocksize - 1; |
0f4b558c |
44 | arg_assert(!(md->mask & blocksize)); |
1fb3cba0 |
45 | arg_assert(blocksize <= 255); |
46 | |
47 | *md_r= md; |
48 | return blocksize; |
49 | } |
50 | |
51 | static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) { |
52 | unsigned long blocksize; |
53 | |
54 | blocksize= setup(md_r); |
55 | *maxsuffix_io += blocksize + 1; |
56 | } |
57 | |
58 | static void mds_pkcs5(struct mechdata **md_r) { |
59 | setup(md_r); |
60 | } |
61 | |
62 | static void menc_pkcs5(struct mechdata *md, struct buffer *buf) { |
63 | unsigned char *pad; |
64 | int padlen; |
65 | |
66 | /* eg with blocksize=4 mask=3 mask+2=5 */ |
67 | /* msgsize 20 21 22 23 24 */ |
68 | padlen= md->mask - buf->size; /* -17 -18 -19 -16 -17 */ |
69 | padlen &= md->mask; /* 3 2 1 0 3 */ |
70 | padlen++; /* 4 3 2 1 4 */ |
71 | |
72 | pad= buf_append(buf,padlen); |
73 | memset(pad,padlen,padlen); |
74 | } |
75 | |
76 | static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) { |
77 | unsigned char *padp; |
78 | unsigned padlen; |
79 | int i; |
80 | |
ed509ebd |
81 | BUF_UNAPPEND(padp,buf,1); |
1fb3cba0 |
82 | padlen= *padp; |
ed509ebd |
83 | if (!padlen || (padlen > md->mask+1)) return "invalid length"; |
1fb3cba0 |
84 | |
ed509ebd |
85 | BUF_UNAPPEND(padp,buf,padlen-1); |
1fb3cba0 |
86 | for (i=0; i<padlen-1; i++) |
87 | if (*++padp != padlen) return "corrupted padding"; |
88 | |
89 | return 0; |
90 | } |
91 | |
92 | STANDARD_MECHANISMLIST("pkcs5",pkcs5) |