1 /* $OpenBSD: dh.c,v 1.39 2006/07/26 02:35:17 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 <sys/param.h>
30 #include <openssl/bn.h>
31 #include <openssl/dh.h>
36 #include "pathnames.h"
41 parse_prime(int linenum, char *line, struct dhgroup *dhg)
44 char *strsize, *gen, *prime;
45 const char *errstr = NULL;
48 if ((arg = strdelim(&cp)) == NULL)
50 /* Ignore leading whitespace */
53 if (!arg || !*arg || *arg == '#')
57 if (cp == NULL || *arg == '\0')
59 arg = strsep(&cp, " "); /* type */
60 if (cp == NULL || *arg == '\0')
62 arg = strsep(&cp, " "); /* tests */
63 if (cp == NULL || *arg == '\0')
65 arg = strsep(&cp, " "); /* tries */
66 if (cp == NULL || *arg == '\0')
68 strsize = strsep(&cp, " "); /* size */
69 if (cp == NULL || *strsize == '\0' ||
70 (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
73 /* The whole group is one bit larger */
75 gen = strsep(&cp, " "); /* gen */
76 if (cp == NULL || *gen == '\0')
78 prime = strsep(&cp, " "); /* prime */
79 if (cp != NULL || *prime == '\0')
82 if ((dhg->g = BN_new()) == NULL)
83 fatal("parse_prime: BN_new failed");
84 if ((dhg->p = BN_new()) == NULL)
85 fatal("parse_prime: BN_new failed");
86 if (BN_hex2bn(&dhg->g, gen) == 0)
89 if (BN_hex2bn(&dhg->p, prime) == 0)
92 if (BN_num_bits(dhg->p) != dhg->size)
95 if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
101 BN_clear_free(dhg->g);
102 BN_clear_free(dhg->p);
104 error("Bad prime description in line %d", linenum);
109 choose_dh(int min, int wantbits, int max)
113 int best, bestcount, which;
117 if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
118 (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
119 logit("WARNING: %s does not exist, using fixed modulus",
121 return (dh_new_group14());
125 best = bestcount = 0;
126 while (fgets(line, sizeof(line), f)) {
128 if (!parse_prime(linenum, line, &dhg))
130 BN_clear_free(dhg.g);
131 BN_clear_free(dhg.p);
133 if (dhg.size > max || dhg.size < min)
136 if ((dhg.size > wantbits && dhg.size < best) ||
137 (dhg.size > best && best < wantbits)) {
141 if (dhg.size == best)
146 if (bestcount == 0) {
148 logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
149 return (dh_new_group14());
153 which = arc4random() % bestcount;
154 while (fgets(line, sizeof(line), f)) {
155 if (!parse_prime(linenum, line, &dhg))
157 if ((dhg.size > max || dhg.size < min) ||
159 linenum++ != which) {
160 BN_clear_free(dhg.g);
161 BN_clear_free(dhg.p);
167 if (linenum != which+1)
168 fatal("WARNING: line %d disappeared in %s, giving up",
169 which, _PATH_DH_PRIMES);
171 return (dh_new_group(dhg.g, dhg.p));
174 /* diffie-hellman-groupN-sha1 */
177 dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
180 int n = BN_num_bits(dh_pub);
185 logit("invalid public DH value: negativ");
188 if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
189 logit("invalid public DH value: <= 1");
193 if ((tmp = BN_new()) == NULL)
195 if (!BN_sub(tmp, dh->p, BN_value_one()) ||
196 BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
198 logit("invalid public DH value: >= p-1");
203 for (i = 0; i <= n; i++)
204 if (BN_is_bit_set(dh_pub, i))
206 debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
208 /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
212 logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
217 dh_gen_key(DH *dh, int need)
219 int i, bits_set, tries = 0;
222 fatal("dh_gen_key: dh->p == NULL");
223 if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
224 fatal("dh_gen_key: group too small: %d (2*need %d)",
225 BN_num_bits(dh->p), 2*need);
227 if (dh->priv_key != NULL)
228 BN_clear_free(dh->priv_key);
229 if ((dh->priv_key = BN_new()) == NULL)
230 fatal("dh_gen_key: BN_new failed");
231 /* generate a 2*need bits random private exponent */
232 if (!BN_rand(dh->priv_key, 2*need, 0, 0))
233 fatal("dh_gen_key: BN_rand failed");
234 if (DH_generate_key(dh) == 0)
235 fatal("DH_generate_key");
236 for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
237 if (BN_is_bit_set(dh->priv_key, i))
239 debug2("dh_gen_key: priv key bits set: %d/%d",
240 bits_set, BN_num_bits(dh->priv_key));
242 fatal("dh_gen_key: too many bad keys: giving up");
243 } while (!dh_pub_is_valid(dh, dh->pub_key));
247 dh_new_group_asc(const char *gen, const char *modulus)
251 if ((dh = DH_new()) == NULL)
252 fatal("dh_new_group_asc: DH_new");
254 if (BN_hex2bn(&dh->p, modulus) == 0)
255 fatal("BN_hex2bn p");
256 if (BN_hex2bn(&dh->g, gen) == 0)
257 fatal("BN_hex2bn g");
263 * This just returns the group, we still need to generate the exchange
268 dh_new_group(BIGNUM *gen, BIGNUM *modulus)
272 if ((dh = DH_new()) == NULL)
273 fatal("dh_new_group: DH_new");
283 static char *gen = "2", *group1 =
284 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
285 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
286 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
287 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
288 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
289 "FFFFFFFF" "FFFFFFFF";
291 return (dh_new_group_asc(gen, group1));
297 static char *gen = "2", *group14 =
298 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
299 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
300 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
301 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
302 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
303 "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
304 "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
305 "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
306 "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
307 "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
308 "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
310 return (dh_new_group_asc(gen, group14));
314 * Estimates the group order for a Diffie-Hellman group that has an
315 * attack complexity approximately the same as O(2**bits). Estimate
316 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
320 dh_estimate(int bits)
324 return (1024); /* O(2**86) */
326 return (2048); /* O(2**116) */
327 return (4096); /* O(2**156) */