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1 /* $OpenBSD: dh.c,v 1.46 2008/04/13 00:22:17 djm Exp $ */
2 /*
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
7 * are met:
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.
26 #include "includes.h"
28 #include <sys/param.h>
30 #include <openssl/bn.h>
31 #include <openssl/dh.h>
33 #include <stdarg.h>
34 #include <stdio.h>
35 #include <stdlib.h>
36 #include <string.h>
38 #include "dh.h"
39 #include "pathnames.h"
40 #include "log.h"
41 #include "misc.h"
43 static int
44 parse_prime(int linenum, char *line, struct dhgroup *dhg)
46 char *cp, *arg;
47 char *strsize, *gen, *prime;
48 const char *errstr = NULL;
50 cp = line;
51 if ((arg = strdelim(&cp)) == NULL)
52 return 0;
53 /* Ignore leading whitespace */
54 if (*arg == '\0')
55 arg = strdelim(&cp);
56 if (!arg || !*arg || *arg == '#')
57 return 0;
59 /* time */
60 if (cp == NULL || *arg == '\0')
61 goto fail;
62 arg = strsep(&cp, " "); /* type */
63 if (cp == NULL || *arg == '\0')
64 goto fail;
65 arg = strsep(&cp, " "); /* tests */
66 if (cp == NULL || *arg == '\0')
67 goto fail;
68 arg = strsep(&cp, " "); /* tries */
69 if (cp == NULL || *arg == '\0')
70 goto fail;
71 strsize = strsep(&cp, " "); /* size */
72 if (cp == NULL || *strsize == '\0' ||
73 (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
74 errstr)
75 goto fail;
76 /* The whole group is one bit larger */
77 dhg->size++;
78 gen = strsep(&cp, " "); /* gen */
79 if (cp == NULL || *gen == '\0')
80 goto fail;
81 prime = strsep(&cp, " "); /* prime */
82 if (cp != NULL || *prime == '\0')
83 goto fail;
85 if ((dhg->g = BN_new()) == NULL)
86 fatal("parse_prime: BN_new failed");
87 if ((dhg->p = BN_new()) == NULL)
88 fatal("parse_prime: BN_new failed");
89 if (BN_hex2bn(&dhg->g, gen) == 0)
90 goto failclean;
92 if (BN_hex2bn(&dhg->p, prime) == 0)
93 goto failclean;
95 if (BN_num_bits(dhg->p) != dhg->size)
96 goto failclean;
98 if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
99 goto failclean;
101 return (1);
103 failclean:
104 BN_clear_free(dhg->g);
105 BN_clear_free(dhg->p);
106 fail:
107 error("Bad prime description in line %d", linenum);
108 return (0);
111 DH *
112 choose_dh(int min, int wantbits, int max)
114 FILE *f;
115 char line[4096];
116 int best, bestcount, which;
117 int linenum;
118 struct dhgroup dhg;
120 if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
121 (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
122 logit("WARNING: %s does not exist, using fixed modulus",
123 _PATH_DH_MODULI);
124 return (dh_new_group14());
127 linenum = 0;
128 best = bestcount = 0;
129 while (fgets(line, sizeof(line), f)) {
130 linenum++;
131 if (!parse_prime(linenum, line, &dhg))
132 continue;
133 BN_clear_free(dhg.g);
134 BN_clear_free(dhg.p);
136 if (dhg.size > max || dhg.size < min)
137 continue;
139 if ((dhg.size > wantbits && dhg.size < best) ||
140 (dhg.size > best && best < wantbits)) {
141 best = dhg.size;
142 bestcount = 0;
144 if (dhg.size == best)
145 bestcount++;
147 rewind(f);
149 if (bestcount == 0) {
150 fclose(f);
151 logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
152 return (dh_new_group14());
155 linenum = 0;
156 which = arc4random_uniform(bestcount);
157 while (fgets(line, sizeof(line), f)) {
158 if (!parse_prime(linenum, line, &dhg))
159 continue;
160 if ((dhg.size > max || dhg.size < min) ||
161 dhg.size != best ||
162 linenum++ != which) {
163 BN_clear_free(dhg.g);
164 BN_clear_free(dhg.p);
165 continue;
167 break;
169 fclose(f);
170 if (linenum != which+1)
171 fatal("WARNING: line %d disappeared in %s, giving up",
172 which, _PATH_DH_PRIMES);
174 return (dh_new_group(dhg.g, dhg.p));
177 /* diffie-hellman-groupN-sha1 */
180 dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
182 int i;
183 int n = BN_num_bits(dh_pub);
184 int bits_set = 0;
185 BIGNUM *tmp;
187 if (dh_pub->neg) {
188 logit("invalid public DH value: negative");
189 return 0;
191 if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
192 logit("invalid public DH value: <= 1");
193 return 0;
196 if ((tmp = BN_new()) == NULL) {
197 error("%s: BN_new failed", __func__);
198 return 0;
200 if (!BN_sub(tmp, dh->p, BN_value_one()) ||
201 BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
202 BN_clear_free(tmp);
203 logit("invalid public DH value: >= p-1");
204 return 0;
206 BN_clear_free(tmp);
208 for (i = 0; i <= n; i++)
209 if (BN_is_bit_set(dh_pub, i))
210 bits_set++;
211 debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
213 /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
214 if (bits_set > 1)
215 return 1;
217 logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
218 return 0;
221 void
222 dh_gen_key(DH *dh, int need)
224 int i, bits_set, tries = 0;
226 if (dh->p == NULL)
227 fatal("dh_gen_key: dh->p == NULL");
228 if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
229 fatal("dh_gen_key: group too small: %d (2*need %d)",
230 BN_num_bits(dh->p), 2*need);
231 do {
232 if (dh->priv_key != NULL)
233 BN_clear_free(dh->priv_key);
234 if ((dh->priv_key = BN_new()) == NULL)
235 fatal("dh_gen_key: BN_new failed");
236 /* generate a 2*need bits random private exponent */
237 if (!BN_rand(dh->priv_key, 2*need, 0, 0))
238 fatal("dh_gen_key: BN_rand failed");
239 if (DH_generate_key(dh) == 0)
240 fatal("DH_generate_key");
241 for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
242 if (BN_is_bit_set(dh->priv_key, i))
243 bits_set++;
244 debug2("dh_gen_key: priv key bits set: %d/%d",
245 bits_set, BN_num_bits(dh->priv_key));
246 if (tries++ > 10)
247 fatal("dh_gen_key: too many bad keys: giving up");
248 } while (!dh_pub_is_valid(dh, dh->pub_key));
251 DH *
252 dh_new_group_asc(const char *gen, const char *modulus)
254 DH *dh;
256 if ((dh = DH_new()) == NULL)
257 fatal("dh_new_group_asc: DH_new");
259 if (BN_hex2bn(&dh->p, modulus) == 0)
260 fatal("BN_hex2bn p");
261 if (BN_hex2bn(&dh->g, gen) == 0)
262 fatal("BN_hex2bn g");
264 return (dh);
268 * This just returns the group, we still need to generate the exchange
269 * value.
272 DH *
273 dh_new_group(BIGNUM *gen, BIGNUM *modulus)
275 DH *dh;
277 if ((dh = DH_new()) == NULL)
278 fatal("dh_new_group: DH_new");
279 dh->p = modulus;
280 dh->g = gen;
282 return (dh);
285 DH *
286 dh_new_group1(void)
288 static char *gen = "2", *group1 =
289 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
290 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
291 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
292 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
293 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
294 "FFFFFFFF" "FFFFFFFF";
296 return (dh_new_group_asc(gen, group1));
299 DH *
300 dh_new_group14(void)
302 static char *gen = "2", *group14 =
303 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
304 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
305 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
306 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
307 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
308 "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
309 "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
310 "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
311 "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
312 "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
313 "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
315 return (dh_new_group_asc(gen, group14));
319 * Estimates the group order for a Diffie-Hellman group that has an
320 * attack complexity approximately the same as O(2**bits). Estimate
321 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
325 dh_estimate(int bits)
328 if (bits <= 128)
329 return (1024); /* O(2**86) */
330 if (bits <= 192)
331 return (2048); /* O(2**116) */
332 return (4096); /* O(2**156) */