2 * PKCS#5 padding mechanism for udp tunnel
4 * arguments: block size to pad to, must be power of 2
6 * encoding: append between 1 and n bytes, all of the same value being
7 * the number of bytes appended
10 * Copyright (C) 2000 Ian Jackson
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.
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.
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.
27 #include "forwarder.h"
33 static unsigned long setup(struct mechdata **md_r) {
35 unsigned long blocksize;
39 blocksize= getarg_ulong();
40 md->mask= blocksize - 1;
41 arg_assert(!(md->mask & blocksize));
42 arg_assert(blocksize <= 255);
48 static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
49 unsigned long blocksize;
51 blocksize= setup(md_r);
52 *maxsuffix_io += blocksize + 1;
55 static void mds_pkcs5(struct mechdata **md_r) {
59 static void menc_pkcs5(struct mechdata *md, struct buffer *buf) {
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 */
69 pad= buf_append(buf,padlen);
70 memset(pad,padlen,padlen);
73 static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) {
78 BUF_UNAPPEND(padp,buf,1);
80 if (!padlen || (padlen > md->mask+1)) return "invalid length";
82 BUF_UNAPPEND(padp,buf,padlen-1);
83 for (i=0; i<padlen-1; i++)
84 if (*++padp != padlen) return "corrupted padding";
89 STANDARD_MECHANISMLIST("pkcs5",pkcs5)