2 * PKCS#5 padding mechanism for udp tunnel
5 * arguments: block size to pad to, must be power of 2 and <=128
8 * encoding: append between 1 and n bytes, all of the same value being
9 * the number of bytes appended
12 * This file is part of ipif, part of userv-utils
14 * Copyright 1996-2013 Ian Jackson <ijackson@chiark.greenend.org.uk>
15 * Copyright 1998 David Damerell <damerell@chiark.greenend.org.uk>
17 * Chancellor Masters and Scholars of the University of Cambridge
18 * Copyright 2010 Tony Finch <fanf@dotat.at>
20 * This is free software; you can redistribute it and/or modify it
21 * under the terms of the GNU General Public License as published by
22 * the Free Software Foundation; either version 3 of the License, or
23 * (at your option) any later version.
25 * This program is distributed in the hope that it will be useful, but
26 * WITHOUT ANY WARRANTY; without even the implied warranty of
27 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
28 * General Public License for more details.
30 * You should have received a copy of the GNU General Public License
31 * along with userv-utils; if not, see http://www.gnu.org/licenses/.
34 #include "forwarder.h"
40 static unsigned long setup(struct mechdata **md_r) {
42 unsigned long blocksize;
46 blocksize= getarg_ulong();
47 md->mask= blocksize - 1;
48 arg_assert(!(md->mask & blocksize));
49 arg_assert(blocksize <= 255);
55 static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
56 unsigned long blocksize;
58 blocksize= setup(md_r);
59 *maxsuffix_io += blocksize + 1;
62 static void mds_pkcs5(struct mechdata **md_r) {
66 static void menc_pkcs5(struct mechdata *md, struct buffer *buf) {
70 /* eg with blocksize=4 mask=3 mask+2=5 */
71 /* msgsize 20 21 22 23 24 */
72 padlen= md->mask - buf->size; /* -17 -18 -19 -16 -17 */
73 padlen &= md->mask; /* 3 2 1 0 3 */
74 padlen++; /* 4 3 2 1 4 */
76 pad= buf_append(buf,padlen);
77 memset(pad,padlen,padlen);
80 static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) {
85 BUF_UNAPPEND(padp,buf,1);
87 if (!padlen || (padlen > md->mask+1)) return "invalid length";
89 BUF_UNAPPEND(padp,buf,padlen-1);
90 for (i=0; i<padlen-1; i++)
91 if (*++padp != padlen) return "corrupted padding";
96 STANDARD_MECHANISMLIST("pkcs5",pkcs5)