1 /* $OpenBSD: dh.c,v 1.37 2006/07/18 22:27:55 stevesk Exp $ */
3 * Copyright (c) 2000 Niels Provos. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 #include <openssl/bn.h>
29 #include <openssl/dh.h>
32 #include "pathnames.h"
37 parse_prime(int linenum, char *line, struct dhgroup *dhg)
40 char *strsize, *gen, *prime;
41 const char *errstr = NULL;
44 if ((arg = strdelim(&cp)) == NULL)
46 /* Ignore leading whitespace */
49 if (!arg || !*arg || *arg == '#')
53 if (cp == NULL || *arg == '\0')
55 arg = strsep(&cp, " "); /* type */
56 if (cp == NULL || *arg == '\0')
58 arg = strsep(&cp, " "); /* tests */
59 if (cp == NULL || *arg == '\0')
61 arg = strsep(&cp, " "); /* tries */
62 if (cp == NULL || *arg == '\0')
64 strsize = strsep(&cp, " "); /* size */
65 if (cp == NULL || *strsize == '\0' ||
66 (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
69 /* The whole group is one bit larger */
71 gen = strsep(&cp, " "); /* gen */
72 if (cp == NULL || *gen == '\0')
74 prime = strsep(&cp, " "); /* prime */
75 if (cp != NULL || *prime == '\0')
78 if ((dhg->g = BN_new()) == NULL)
79 fatal("parse_prime: BN_new failed");
80 if ((dhg->p = BN_new()) == NULL)
81 fatal("parse_prime: BN_new failed");
82 if (BN_hex2bn(&dhg->g, gen) == 0)
85 if (BN_hex2bn(&dhg->p, prime) == 0)
88 if (BN_num_bits(dhg->p) != dhg->size)
91 if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
97 BN_clear_free(dhg->g);
98 BN_clear_free(dhg->p);
100 error("Bad prime description in line %d", linenum);
105 choose_dh(int min, int wantbits, int max)
109 int best, bestcount, which;
113 if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
114 (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
115 logit("WARNING: %s does not exist, using fixed modulus",
117 return (dh_new_group14());
121 best = bestcount = 0;
122 while (fgets(line, sizeof(line), f)) {
124 if (!parse_prime(linenum, line, &dhg))
126 BN_clear_free(dhg.g);
127 BN_clear_free(dhg.p);
129 if (dhg.size > max || dhg.size < min)
132 if ((dhg.size > wantbits && dhg.size < best) ||
133 (dhg.size > best && best < wantbits)) {
137 if (dhg.size == best)
142 if (bestcount == 0) {
144 logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
145 return (dh_new_group14());
149 which = arc4random() % bestcount;
150 while (fgets(line, sizeof(line), f)) {
151 if (!parse_prime(linenum, line, &dhg))
153 if ((dhg.size > max || dhg.size < min) ||
155 linenum++ != which) {
156 BN_clear_free(dhg.g);
157 BN_clear_free(dhg.p);
163 if (linenum != which+1)
164 fatal("WARNING: line %d disappeared in %s, giving up",
165 which, _PATH_DH_PRIMES);
167 return (dh_new_group(dhg.g, dhg.p));
170 /* diffie-hellman-groupN-sha1 */
173 dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
176 int n = BN_num_bits(dh_pub);
181 logit("invalid public DH value: negativ");
184 if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
185 logit("invalid public DH value: <= 1");
189 if ((tmp = BN_new()) == NULL)
191 if (!BN_sub(tmp, dh->p, BN_value_one()) ||
192 BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
194 logit("invalid public DH value: >= p-1");
199 for (i = 0; i <= n; i++)
200 if (BN_is_bit_set(dh_pub, i))
202 debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
204 /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
208 logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
213 dh_gen_key(DH *dh, int need)
215 int i, bits_set, tries = 0;
218 fatal("dh_gen_key: dh->p == NULL");
219 if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
220 fatal("dh_gen_key: group too small: %d (2*need %d)",
221 BN_num_bits(dh->p), 2*need);
223 if (dh->priv_key != NULL)
224 BN_clear_free(dh->priv_key);
225 if ((dh->priv_key = BN_new()) == NULL)
226 fatal("dh_gen_key: BN_new failed");
227 /* generate a 2*need bits random private exponent */
228 if (!BN_rand(dh->priv_key, 2*need, 0, 0))
229 fatal("dh_gen_key: BN_rand failed");
230 if (DH_generate_key(dh) == 0)
231 fatal("DH_generate_key");
232 for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
233 if (BN_is_bit_set(dh->priv_key, i))
235 debug2("dh_gen_key: priv key bits set: %d/%d",
236 bits_set, BN_num_bits(dh->priv_key));
238 fatal("dh_gen_key: too many bad keys: giving up");
239 } while (!dh_pub_is_valid(dh, dh->pub_key));
243 dh_new_group_asc(const char *gen, const char *modulus)
247 if ((dh = DH_new()) == NULL)
248 fatal("dh_new_group_asc: DH_new");
250 if (BN_hex2bn(&dh->p, modulus) == 0)
251 fatal("BN_hex2bn p");
252 if (BN_hex2bn(&dh->g, gen) == 0)
253 fatal("BN_hex2bn g");
259 * This just returns the group, we still need to generate the exchange
264 dh_new_group(BIGNUM *gen, BIGNUM *modulus)
268 if ((dh = DH_new()) == NULL)
269 fatal("dh_new_group: DH_new");
279 static char *gen = "2", *group1 =
280 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
281 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
282 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
283 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
284 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
285 "FFFFFFFF" "FFFFFFFF";
287 return (dh_new_group_asc(gen, group1));
293 static char *gen = "2", *group14 =
294 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
295 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
296 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
297 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
298 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
299 "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
300 "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
301 "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
302 "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
303 "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
304 "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
306 return (dh_new_group_asc(gen, group14));
310 * Estimates the group order for a Diffie-Hellman group that has an
311 * attack complexity approximately the same as O(2**bits). Estimate
312 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
316 dh_estimate(int bits)
320 return (1024); /* O(2**86) */
322 return (2048); /* O(2**116) */
323 return (4096); /* O(2**156) */