[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 1.10 2001/03/28 22:04:57 provos 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;
	/* The whole group is one bit larger */
	dhg->size++;
	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();
	dhg->p = BN_new();
	if (BN_hex2bn(&dhg->g, gen) < 0)
		goto failclean;

	if (BN_hex2bn(&dhg->p, prime) < 0)
		goto failclean;

	if (BN_num_bits(dhg->p) != dhg->size)
		goto failclean;

	return (1);

 failclean:
	BN_free(dhg->g);
	BN_free(dhg->p);
 fail:
	error("Bad prime description in line %d", linenum);
	return (0);
}

DH *
choose_dh(int min, int wantbits, int max)
{
	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 > max || dhg.size < min)
			continue;

		if ((dhg.size > wantbits && dhg.size < best) ||
		    (dhg.size > best && best < wantbits)) {
			best = dhg.size;
			bestcount = 0;
		}
		if (dhg.size == best)
			bestcount++;
	}
	fclose (f);

	if (bestcount == 0) {
		log("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
		return (NULL);
	}

	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 > max || dhg.size < min)
			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"
c8682232	26	RCSID("$OpenBSD: dh.c,v 1.10 2001/03/28 22:04:57 provos 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;
db1cd2f3	72	/* The whole group is one bit larger */
db1cd2f3	73	dhg->size++;
94ec8c6b	74	gen = strsep(&cp, " "); /* gen */
	75	if (cp == NULL \|\| *gen == '\0')
	76	goto fail;
	77	prime = strsep(&cp, " "); /* prime */
	78	if (cp != NULL \|\| *prime == '\0')
	79	goto fail;
	80
	81	dhg->g = BN_new();
94ec8c6b	82	dhg->p = BN_new();
c8682232	83	if (BN_hex2bn(&dhg->g, gen) < 0)
	84	goto failclean;
	85
	86	if (BN_hex2bn(&dhg->p, prime) < 0)
	87	goto failclean;
	88
	89	if (BN_num_bits(dhg->p) != dhg->size)
	90	goto failclean;
94ec8c6b	91
94ec8c6b	92	return (1);
c8682232	93
	94	failclean:
	95	BN_free(dhg->g);
	96	BN_free(dhg->p);
94ec8c6b	97	fail:
54b974dc	98	error("Bad prime description in line %d", linenum);
94ec8c6b	99	return (0);
	100	}
	101
	102	DH *
db1cd2f3	103	choose_dh(int min, int wantbits, int max)
94ec8c6b	104	{
	105	FILE *f;
	106	char line[1024];
	107	int best, bestcount, which;
	108	int linenum;
	109	struct dhgroup dhg;
	110
42f11eb2	111	f = fopen(_PATH_DH_PRIMES, "r");
94ec8c6b	112	if (!f) {
42f11eb2	113	log("WARNING: %s does not exist, using old prime", _PATH_DH_PRIMES);
94ec8c6b	114	return (dh_new_group1());
	115	}
	116
	117	linenum = 0;
	118	best = bestcount = 0;
	119	while (fgets(line, sizeof(line), f)) {
	120	linenum++;
	121	if (!parse_prime(linenum, line, &dhg))
	122	continue;
	123	BN_free(dhg.g);
	124	BN_free(dhg.p);
	125
db1cd2f3	126	if (dhg.size > max \|\| dhg.size < min)
	127	continue;
	128
	129	if ((dhg.size > wantbits && dhg.size < best) \|\|
	130	(dhg.size > best && best < wantbits)) {
94ec8c6b	131	best = dhg.size;
	132	bestcount = 0;
	133	}
	134	if (dhg.size == best)
	135	bestcount++;
	136	}
	137	fclose (f);
	138
	139	if (bestcount == 0) {
db1cd2f3	140	log("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
db1cd2f3	141	return (NULL);
94ec8c6b	142	}
94ec8c6b	143
42f11eb2	144	f = fopen(_PATH_DH_PRIMES, "r");
94ec8c6b	145	if (!f) {
0b2190ee	146	fatal("WARNING: %s disappeared, giving up", _PATH_DH_PRIMES);
94ec8c6b	147	}
	148
	149	linenum = 0;
	150	which = arc4random() % bestcount;
	151	while (fgets(line, sizeof(line), f)) {
	152	if (!parse_prime(linenum, line, &dhg))
	153	continue;
db1cd2f3	154	if (dhg.size > max \|\| dhg.size < min)
db1cd2f3	155	continue;
94ec8c6b	156	if (dhg.size != best)
	157	continue;
	158	if (linenum++ != which) {
	159	BN_free(dhg.g);
	160	BN_free(dhg.p);
	161	continue;
	162	}
	163	break;
	164	}
	165	fclose(f);
	166
	167	return (dh_new_group(dhg.g, dhg.p));
	168	}