2 * Copyright (c) 2000 Niels Provos. All rights reserved.
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
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.
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.
26 RCSID("$OpenBSD: dh.c,v 1.20 2002/03/06 00:20:54 markus Exp $");
30 #include <openssl/bn.h>
31 #include <openssl/dh.h>
32 #include <openssl/evp.h>
33 #include <openssl/err.h>
39 #include "pathnames.h"
44 parse_prime(int linenum, char *line, struct dhgroup *dhg)
47 char *strsize, *gen, *prime;
51 /* Ignore leading whitespace */
54 if (!*arg || *arg == '#')
58 if (cp == NULL || *arg == '\0')
60 arg = strsep(&cp, " "); /* type */
61 if (cp == NULL || *arg == '\0')
63 arg = strsep(&cp, " "); /* tests */
64 if (cp == NULL || *arg == '\0')
66 arg = strsep(&cp, " "); /* tries */
67 if (cp == NULL || *arg == '\0')
69 strsize = strsep(&cp, " "); /* size */
70 if (cp == NULL || *strsize == '\0' ||
71 (dhg->size = atoi(strsize)) == 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)
98 BN_clear_free(dhg->g);
99 BN_clear_free(dhg->p);
101 error("Bad prime description in line %d", linenum);
106 choose_dh(int min, int wantbits, int max)
110 int best, bestcount, which;
114 if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
115 (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
116 log("WARNING: %s does not exist, using old modulus", _PATH_DH_MODULI);
117 return (dh_new_group1());
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 log("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
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-group1-sha1 */
173 dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
176 int n = BN_num_bits(dh_pub);
180 log("invalid public DH value: negativ");
183 for (i = 0; i <= n; i++)
184 if (BN_is_bit_set(dh_pub, i))
186 debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
188 /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
189 if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1))
191 log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
196 dh_gen_key(DH *dh, int need)
198 int i, bits_set = 0, tries = 0;
201 fatal("dh_gen_key: dh->p == NULL");
202 if (2*need >= BN_num_bits(dh->p))
203 fatal("dh_gen_key: group too small: %d (2*need %d)",
204 BN_num_bits(dh->p), 2*need);
206 if (dh->priv_key != NULL)
207 BN_clear_free(dh->priv_key);
208 if ((dh->priv_key = BN_new()) == NULL)
209 fatal("dh_gen_key: BN_new failed");
210 /* generate a 2*need bits random private exponent */
211 if (!BN_rand(dh->priv_key, 2*need, 0, 0)) {
212 int ecode = ERR_get_error();
213 fatal("dh_gen_key: BN_rand failed: %s", ERR_error_string(ecode, NULL));
215 if (DH_generate_key(dh) == 0)
216 fatal("DH_generate_key");
217 for (i = 0; i <= BN_num_bits(dh->priv_key); i++)
218 if (BN_is_bit_set(dh->priv_key, i))
220 debug("dh_gen_key: priv key bits set: %d/%d",
221 bits_set, BN_num_bits(dh->priv_key));
223 fatal("dh_gen_key: too many bad keys: giving up");
224 } while (!dh_pub_is_valid(dh, dh->pub_key));
228 dh_new_group_asc(const char *gen, const char *modulus)
232 if ((dh = DH_new()) == NULL)
233 fatal("dh_new_group_asc: DH_new");
235 if (BN_hex2bn(&dh->p, modulus) == 0)
236 fatal("BN_hex2bn p");
237 if (BN_hex2bn(&dh->g, gen) == 0)
238 fatal("BN_hex2bn g");
244 * This just returns the group, we still need to generate the exchange
249 dh_new_group(BIGNUM *gen, BIGNUM *modulus)
253 if ((dh = DH_new()) == NULL)
254 fatal("dh_new_group: DH_new");
264 static char *gen = "2", *group1 =
265 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
266 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
267 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
268 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
269 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
270 "FFFFFFFF" "FFFFFFFF";
272 return (dh_new_group_asc(gen, group1));
276 * Estimates the group order for a Diffie-Hellman group that has an
277 * attack complexity approximately the same as O(2**bits). Estimate
278 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
282 dh_estimate(int bits)
286 return (512); /* O(2**63) */
288 return (1024); /* O(2**86) */
290 return (2048); /* O(2**116) */
291 return (4096); /* O(2**156) */