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/*
* Copyright (c) 2000 Niels Provos. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "includes.h"
RCSID("$OpenBSD: dh.c,v 1.8 2001/03/05 17:58:22 stevesk Exp $");
#include "xmalloc.h"
#include <openssl/bn.h>
#include <openssl/dh.h>
#include <openssl/evp.h>
#include "buffer.h"
#include "cipher.h"
#include "kex.h"
#include "dh.h"
#include "pathnames.h"
#include "log.h"
#include "misc.h"
int
parse_prime(int linenum, char *line, struct dhgroup *dhg)
{
char *cp, *arg;
char *strsize, *gen, *prime;
cp = line;
arg = strdelim(&cp);
/* Ignore leading whitespace */
if (*arg == '\0')
arg = strdelim(&cp);
if (!*arg || *arg == '#')
return 0;
/* time */
if (cp == NULL || *arg == '\0')
goto fail;
arg = strsep(&cp, " "); /* type */
if (cp == NULL || *arg == '\0')
goto fail;
arg = strsep(&cp, " "); /* tests */
if (cp == NULL || *arg == '\0')
goto fail;
arg = strsep(&cp, " "); /* tries */
if (cp == NULL || *arg == '\0')
goto fail;
strsize = strsep(&cp, " "); /* size */
if (cp == NULL || *strsize == '\0' ||
(dhg->size = atoi(strsize)) == 0)
goto fail;
gen = strsep(&cp, " "); /* gen */
if (cp == NULL || *gen == '\0')
goto fail;
prime = strsep(&cp, " "); /* prime */
if (cp != NULL || *prime == '\0')
goto fail;
dhg->g = BN_new();
if (BN_hex2bn(&dhg->g, gen) < 0) {
BN_free(dhg->g);
goto fail;
}
dhg->p = BN_new();
if (BN_hex2bn(&dhg->p, prime) < 0) {
BN_free(dhg->g);
BN_free(dhg->p);
goto fail;
}
return (1);
fail:
error("Bad prime description in line %d", linenum);
return (0);
}
DH *
choose_dh(int minbits)
{
FILE *f;
char line[1024];
int best, bestcount, which;
int linenum;
struct dhgroup dhg;
f = fopen(_PATH_DH_PRIMES, "r");
if (!f) {
log("WARNING: %s does not exist, using old prime", _PATH_DH_PRIMES);
return (dh_new_group1());
}
linenum = 0;
best = bestcount = 0;
while (fgets(line, sizeof(line), f)) {
linenum++;
if (!parse_prime(linenum, line, &dhg))
continue;
BN_free(dhg.g);
BN_free(dhg.p);
if ((dhg.size > minbits && dhg.size < best) ||
(dhg.size > best && best < minbits)) {
best = dhg.size;
bestcount = 0;
}
if (dhg.size == best)
bestcount++;
}
fclose (f);
if (bestcount == 0) {
log("WARNING: no primes in %s, using old prime", _PATH_DH_PRIMES);
return (dh_new_group1());
}
f = fopen(_PATH_DH_PRIMES, "r");
if (!f) {
fatal("WARNING: %s disappeared, giving up", _PATH_DH_PRIMES);
}
linenum = 0;
which = arc4random() % bestcount;
while (fgets(line, sizeof(line), f)) {
if (!parse_prime(linenum, line, &dhg))
continue;
if (dhg.size != best)
continue;
if (linenum++ != which) {
BN_free(dhg.g);
BN_free(dhg.p);
continue;
}
break;
}
fclose(f);
return (dh_new_group(dhg.g, dhg.p));
}
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