[openssh.git] / dh.c

/*
 * 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));
}
Commit	Line	Data
94ec8c6b	1	/*
	2	* Copyright (c) 2000 Niels Provos. All rights reserved.
	3	*
	4	* Redistribution and use in source and binary forms, with or without
	5	* modification, are permitted provided that the following conditions
	6	* are met:
	7	* 1. Redistributions of source code must retain the above copyright
	8	* notice, this list of conditions and the following disclaimer.
	9	* 2. Redistributions in binary form must reproduce the above copyright
	10	* notice, this list of conditions and the following disclaimer in the
	11	* documentation and/or other materials provided with the distribution.
	12	*
	13	* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
	14	* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
	15	* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
	16	* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
	17	* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
	18	* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
	19	* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
	20	* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
	21	* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
	22	* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
	23	*/
	24
	25	#include "includes.h"
0b2190ee	26	RCSID("$OpenBSD: dh.c,v 1.8 2001/03/05 17:58:22 stevesk Exp $");
94ec8c6b	27
	28	#include "xmalloc.h"
	29
	30	#include <openssl/bn.h>
	31	#include <openssl/dh.h>
	32	#include <openssl/evp.h>
	33
94ec8c6b	34	#include "buffer.h"
42f11eb2	35	#include "cipher.h"
94ec8c6b	36	#include "kex.h"
94ec8c6b	37	#include "dh.h"
42f11eb2	38	#include "pathnames.h"
	39	#include "log.h"
	40	#include "misc.h"
94ec8c6b	41
	42	int
	43	parse_prime(int linenum, char line, struct dhgroup dhg)
	44	{
	45	char cp, arg;
	46	char strsize, gen, *prime;
	47
	48	cp = line;
	49	arg = strdelim(&cp);
	50	/* Ignore leading whitespace */
	51	if (*arg == '\0')
	52	arg = strdelim(&cp);
	53	if (!arg \|\| arg == '#')
	54	return 0;
	55
	56	/* time */
	57	if (cp == NULL \|\| *arg == '\0')
	58	goto fail;
	59	arg = strsep(&cp, " "); /* type */
	60	if (cp == NULL \|\| *arg == '\0')
	61	goto fail;
	62	arg = strsep(&cp, " "); /* tests */
	63	if (cp == NULL \|\| *arg == '\0')
	64	goto fail;
	65	arg = strsep(&cp, " "); /* tries */
	66	if (cp == NULL \|\| *arg == '\0')
	67	goto fail;
	68	strsize = strsep(&cp, " "); /* size */
	69	if (cp == NULL \|\| *strsize == '\0' \|\|
	70	(dhg->size = atoi(strsize)) == 0)
	71	goto fail;
	72	gen = strsep(&cp, " "); /* gen */
	73	if (cp == NULL \|\| *gen == '\0')
	74	goto fail;
	75	prime = strsep(&cp, " "); /* prime */
	76	if (cp != NULL \|\| *prime == '\0')
	77	goto fail;
	78
	79	dhg->g = BN_new();
	80	if (BN_hex2bn(&dhg->g, gen) < 0) {
	81	BN_free(dhg->g);
	82	goto fail;
	83	}
	84	dhg->p = BN_new();
	85	if (BN_hex2bn(&dhg->p, prime) < 0) {
	86	BN_free(dhg->g);
	87	BN_free(dhg->p);
	88	goto fail;
	89	}
	90
	91	return (1);
	92	fail:
54b974dc	93	error("Bad prime description in line %d", linenum);
94ec8c6b	94	return (0);
	95	}
	96
	97	DH *
	98	choose_dh(int minbits)
	99	{
	100	FILE *f;
	101	char line[1024];
	102	int best, bestcount, which;
	103	int linenum;
	104	struct dhgroup dhg;
	105
42f11eb2	106	f = fopen(_PATH_DH_PRIMES, "r");
94ec8c6b	107	if (!f) {
42f11eb2	108	log("WARNING: %s does not exist, using old prime", _PATH_DH_PRIMES);
94ec8c6b	109	return (dh_new_group1());
	110	}
	111
	112	linenum = 0;
	113	best = bestcount = 0;
	114	while (fgets(line, sizeof(line), f)) {
	115	linenum++;
	116	if (!parse_prime(linenum, line, &dhg))
	117	continue;
	118	BN_free(dhg.g);
	119	BN_free(dhg.p);
	120
	121	if ((dhg.size > minbits && dhg.size < best) \|\|
	122	(dhg.size > best && best < minbits)) {
	123	best = dhg.size;
	124	bestcount = 0;
	125	}
	126	if (dhg.size == best)
	127	bestcount++;
	128	}
	129	fclose (f);
	130
	131	if (bestcount == 0) {
42f11eb2	132	log("WARNING: no primes in %s, using old prime", _PATH_DH_PRIMES);
94ec8c6b	133	return (dh_new_group1());
	134	}
	135
42f11eb2	136	f = fopen(_PATH_DH_PRIMES, "r");
94ec8c6b	137	if (!f) {
0b2190ee	138	fatal("WARNING: %s disappeared, giving up", _PATH_DH_PRIMES);
94ec8c6b	139	}
	140
	141	linenum = 0;
	142	which = arc4random() % bestcount;
	143	while (fgets(line, sizeof(line), f)) {
	144	if (!parse_prime(linenum, line, &dhg))
	145	continue;
	146	if (dhg.size != best)
	147	continue;
	148	if (linenum++ != which) {
	149	BN_free(dhg.g);
	150	BN_free(dhg.p);
	151	continue;
	152	}
	153	break;
	154	}
	155	fclose(f);
	156
	157	return (dh_new_group(dhg.g, dhg.p));
	158	}