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/*
* PKCS#5 padding mechanism for udp tunnel
*
* mechanism: pkcs5
* arguments: block size to pad to, must be power of 2 and <=128
*
* restrictions: none
* encoding: append between 1 and n bytes, all of the same value being
* the number of bytes appended
*/
/*
* This file is part of ipif, part of userv-utils
*
* Copyright 1996-2013 Ian Jackson <ijackson@chiark.greenend.org.uk>
* Copyright 1998 David Damerell <damerell@chiark.greenend.org.uk>
* Copyright 1999,2003
* Chancellor Masters and Scholars of the University of Cambridge
* Copyright 2010 Tony Finch <fanf@dotat.at>
*
* This is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful, but
* WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with userv-utils; if not, see http://www.gnu.org/licenses/.
*/
#include "forwarder.h"
struct mechdata {
unsigned mask;
};
static unsigned long setup(struct mechdata **md_r) {
struct mechdata *md;
unsigned long blocksize;
XMALLOC(md);
blocksize= getarg_ulong();
md->mask= blocksize - 1;
arg_assert(!(md->mask & blocksize));
arg_assert(blocksize <= 255);
*md_r= md;
return blocksize;
}
static void mes_pkcs5(struct mechdata **md_r, int *maxprefix_io, int *maxsuffix_io) {
unsigned long blocksize;
blocksize= setup(md_r);
*maxsuffix_io += blocksize + 1;
}
static void mds_pkcs5(struct mechdata **md_r) {
setup(md_r);
}
static void menc_pkcs5(struct mechdata *md, struct buffer *buf) {
unsigned char *pad;
int padlen;
/* eg with blocksize=4 mask=3 mask+2=5 */
/* msgsize 20 21 22 23 24 */
padlen= md->mask - buf->size; /* -17 -18 -19 -16 -17 */
padlen &= md->mask; /* 3 2 1 0 3 */
padlen++; /* 4 3 2 1 4 */
pad= buf_append(buf,padlen);
memset(pad,padlen,padlen);
}
static const char *mdec_pkcs5(struct mechdata *md, struct buffer *buf) {
unsigned char *padp;
unsigned padlen;
int i;
BUF_UNAPPEND(padp,buf,1);
padlen= *padp;
if (!padlen || (padlen > md->mask+1)) return "invalid length";
BUF_UNAPPEND(padp,buf,padlen-1);
for (i=0; i<padlen-1; i++)
if (*++padp != padlen) return "corrupted padding";
return 0;
}
STANDARD_MECHANISMLIST("pkcs5",pkcs5)
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