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
)