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1 | /* $OpenBSD: dh.c,v 1.45 2007/09/27 00:15:57 ray Exp $ */ | |
2 | /* | |
3 | * Copyright (c) 2000 Niels Provos. All rights reserved. | |
4 | * | |
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. | |
13 | * | |
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. | |
24 | */ | |
25 | ||
26 | #include "includes.h" | |
27 | ||
28 | #include <sys/param.h> | |
29 | ||
30 | #include <openssl/bn.h> | |
31 | #include <openssl/dh.h> | |
32 | ||
33 | #include <stdarg.h> | |
34 | #include <stdio.h> | |
35 | #include <stdlib.h> | |
36 | #include <string.h> | |
37 | ||
38 | #include "dh.h" | |
39 | #include "pathnames.h" | |
40 | #include "log.h" | |
41 | #include "misc.h" | |
42 | ||
43 | static int | |
44 | parse_prime(int linenum, char *line, struct dhgroup *dhg) | |
45 | { | |
46 | char *cp, *arg; | |
47 | char *strsize, *gen, *prime; | |
48 | const char *errstr = NULL; | |
49 | ||
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; | |
58 | ||
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; | |
84 | ||
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; | |
91 | ||
92 | if (BN_hex2bn(&dhg->p, prime) == 0) | |
93 | goto failclean; | |
94 | ||
95 | if (BN_num_bits(dhg->p) != dhg->size) | |
96 | goto failclean; | |
97 | ||
98 | if (BN_is_zero(dhg->g) || BN_is_one(dhg->g)) | |
99 | goto failclean; | |
100 | ||
101 | return (1); | |
102 | ||
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); | |
109 | } | |
110 | ||
111 | DH * | |
112 | choose_dh(int min, int wantbits, int max) | |
113 | { | |
114 | FILE *f; | |
115 | char line[4096]; | |
116 | int best, bestcount, which; | |
117 | int linenum; | |
118 | struct dhgroup dhg; | |
119 | ||
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()); | |
125 | } | |
126 | ||
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); | |
135 | ||
136 | if (dhg.size > max || dhg.size < min) | |
137 | continue; | |
138 | ||
139 | if ((dhg.size > wantbits && dhg.size < best) || | |
140 | (dhg.size > best && best < wantbits)) { | |
141 | best = dhg.size; | |
142 | bestcount = 0; | |
143 | } | |
144 | if (dhg.size == best) | |
145 | bestcount++; | |
146 | } | |
147 | rewind(f); | |
148 | ||
149 | if (bestcount == 0) { | |
150 | fclose(f); | |
151 | logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES); | |
152 | return (dh_new_group14()); | |
153 | } | |
154 | ||
155 | linenum = 0; | |
156 | which = arc4random() % 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; | |
166 | } | |
167 | break; | |
168 | } | |
169 | fclose(f); | |
170 | if (linenum != which+1) | |
171 | fatal("WARNING: line %d disappeared in %s, giving up", | |
172 | which, _PATH_DH_PRIMES); | |
173 | ||
174 | return (dh_new_group(dhg.g, dhg.p)); | |
175 | } | |
176 | ||
177 | /* diffie-hellman-groupN-sha1 */ | |
178 | ||
179 | int | |
180 | dh_pub_is_valid(DH *dh, BIGNUM *dh_pub) | |
181 | { | |
182 | int i; | |
183 | int n = BN_num_bits(dh_pub); | |
184 | int bits_set = 0; | |
185 | BIGNUM *tmp; | |
186 | ||
187 | if (dh_pub->neg) { | |
188 | logit("invalid public DH value: negative"); | |
189 | return 0; | |
190 | } | |
191 | if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */ | |
192 | logit("invalid public DH value: <= 1"); | |
193 | return 0; | |
194 | } | |
195 | ||
196 | if ((tmp = BN_new()) == NULL) { | |
197 | error("%s: BN_new failed", __func__); | |
198 | return 0; | |
199 | } | |
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; | |
205 | } | |
206 | BN_clear_free(tmp); | |
207 | ||
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)); | |
212 | ||
213 | /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */ | |
214 | if (bits_set > 1) | |
215 | return 1; | |
216 | ||
217 | logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p)); | |
218 | return 0; | |
219 | } | |
220 | ||
221 | void | |
222 | dh_gen_key(DH *dh, int need) | |
223 | { | |
224 | int i, bits_set, tries = 0; | |
225 | ||
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)); | |
249 | } | |
250 | ||
251 | DH * | |
252 | dh_new_group_asc(const char *gen, const char *modulus) | |
253 | { | |
254 | DH *dh; | |
255 | ||
256 | if ((dh = DH_new()) == NULL) | |
257 | fatal("dh_new_group_asc: DH_new"); | |
258 | ||
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"); | |
263 | ||
264 | return (dh); | |
265 | } | |
266 | ||
267 | /* | |
268 | * This just returns the group, we still need to generate the exchange | |
269 | * value. | |
270 | */ | |
271 | ||
272 | DH * | |
273 | dh_new_group(BIGNUM *gen, BIGNUM *modulus) | |
274 | { | |
275 | DH *dh; | |
276 | ||
277 | if ((dh = DH_new()) == NULL) | |
278 | fatal("dh_new_group: DH_new"); | |
279 | dh->p = modulus; | |
280 | dh->g = gen; | |
281 | ||
282 | return (dh); | |
283 | } | |
284 | ||
285 | DH * | |
286 | dh_new_group1(void) | |
287 | { | |
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"; | |
295 | ||
296 | return (dh_new_group_asc(gen, group1)); | |
297 | } | |
298 | ||
299 | DH * | |
300 | dh_new_group14(void) | |
301 | { | |
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"; | |
314 | ||
315 | return (dh_new_group_asc(gen, group14)); | |
316 | } | |
317 | ||
318 | /* | |
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))) | |
322 | */ | |
323 | ||
324 | int | |
325 | dh_estimate(int bits) | |
326 | { | |
327 | ||
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) */ | |
333 | } |