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94ec8c6b | 1 | /* |
2 | * Copyright (c) 2000 Niels Provos. All rights reserved. | |
3 | * | |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
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. | |
12 | * | |
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. | |
23 | */ | |
24 | ||
25 | #include "includes.h" | |
f11fe301 | 26 | RCSID("$OpenBSD: dh.c,v 1.22 2002/06/27 08:49:44 markus Exp $"); |
94ec8c6b | 27 | |
28 | #include "xmalloc.h" | |
29 | ||
30 | #include <openssl/bn.h> | |
31 | #include <openssl/dh.h> | |
32 | #include <openssl/evp.h> | |
33 | ||
94ec8c6b | 34 | #include "buffer.h" |
42f11eb2 | 35 | #include "cipher.h" |
94ec8c6b | 36 | #include "kex.h" |
37 | #include "dh.h" | |
42f11eb2 | 38 | #include "pathnames.h" |
39 | #include "log.h" | |
40 | #include "misc.h" | |
94ec8c6b | 41 | |
396c147e | 42 | static int |
94ec8c6b | 43 | parse_prime(int linenum, char *line, struct dhgroup *dhg) |
44 | { | |
45 | char *cp, *arg; | |
46 | char *strsize, *gen, *prime; | |
47 | ||
48 | cp = line; | |
49 | arg = strdelim(&cp); | |
50 | /* Ignore leading whitespace */ | |
51 | if (*arg == '\0') | |
52 | arg = strdelim(&cp); | |
f11fe301 | 53 | if (!arg || !*arg || *arg == '#') |
94ec8c6b | 54 | return 0; |
55 | ||
56 | /* time */ | |
57 | if (cp == NULL || *arg == '\0') | |
58 | goto fail; | |
59 | arg = strsep(&cp, " "); /* type */ | |
60 | if (cp == NULL || *arg == '\0') | |
61 | goto fail; | |
62 | arg = strsep(&cp, " "); /* tests */ | |
63 | if (cp == NULL || *arg == '\0') | |
64 | goto fail; | |
65 | arg = strsep(&cp, " "); /* tries */ | |
66 | if (cp == NULL || *arg == '\0') | |
67 | goto fail; | |
68 | strsize = strsep(&cp, " "); /* size */ | |
69 | if (cp == NULL || *strsize == '\0' || | |
70 | (dhg->size = atoi(strsize)) == 0) | |
71 | goto fail; | |
db1cd2f3 | 72 | /* The whole group is one bit larger */ |
73 | dhg->size++; | |
94ec8c6b | 74 | gen = strsep(&cp, " "); /* gen */ |
75 | if (cp == NULL || *gen == '\0') | |
76 | goto fail; | |
77 | prime = strsep(&cp, " "); /* prime */ | |
78 | if (cp != NULL || *prime == '\0') | |
79 | goto fail; | |
80 | ||
b775c6f2 | 81 | if ((dhg->g = BN_new()) == NULL) |
82 | fatal("parse_prime: BN_new failed"); | |
83 | if ((dhg->p = BN_new()) == NULL) | |
84 | fatal("parse_prime: BN_new failed"); | |
ec1f12d3 | 85 | if (BN_hex2bn(&dhg->g, gen) == 0) |
c8682232 | 86 | goto failclean; |
87 | ||
ec1f12d3 | 88 | if (BN_hex2bn(&dhg->p, prime) == 0) |
c8682232 | 89 | goto failclean; |
90 | ||
91 | if (BN_num_bits(dhg->p) != dhg->size) | |
92 | goto failclean; | |
94ec8c6b | 93 | |
94 | return (1); | |
c8682232 | 95 | |
96 | failclean: | |
108d362e | 97 | BN_clear_free(dhg->g); |
98 | BN_clear_free(dhg->p); | |
94ec8c6b | 99 | fail: |
54b974dc | 100 | error("Bad prime description in line %d", linenum); |
94ec8c6b | 101 | return (0); |
102 | } | |
103 | ||
104 | DH * | |
db1cd2f3 | 105 | choose_dh(int min, int wantbits, int max) |
94ec8c6b | 106 | { |
107 | FILE *f; | |
826676b3 | 108 | char line[2048]; |
94ec8c6b | 109 | int best, bestcount, which; |
110 | int linenum; | |
111 | struct dhgroup dhg; | |
112 | ||
e2854364 | 113 | if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL && |
114 | (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) { | |
115 | log("WARNING: %s does not exist, using old modulus", _PATH_DH_MODULI); | |
94ec8c6b | 116 | return (dh_new_group1()); |
117 | } | |
118 | ||
119 | linenum = 0; | |
120 | best = bestcount = 0; | |
121 | while (fgets(line, sizeof(line), f)) { | |
122 | linenum++; | |
123 | if (!parse_prime(linenum, line, &dhg)) | |
124 | continue; | |
108d362e | 125 | BN_clear_free(dhg.g); |
126 | BN_clear_free(dhg.p); | |
94ec8c6b | 127 | |
db1cd2f3 | 128 | if (dhg.size > max || dhg.size < min) |
129 | continue; | |
130 | ||
131 | if ((dhg.size > wantbits && dhg.size < best) || | |
132 | (dhg.size > best && best < wantbits)) { | |
94ec8c6b | 133 | best = dhg.size; |
134 | bestcount = 0; | |
135 | } | |
136 | if (dhg.size == best) | |
137 | bestcount++; | |
138 | } | |
826676b3 | 139 | rewind(f); |
94ec8c6b | 140 | |
141 | if (bestcount == 0) { | |
826676b3 | 142 | fclose(f); |
db1cd2f3 | 143 | log("WARNING: no suitable primes in %s", _PATH_DH_PRIMES); |
144 | return (NULL); | |
94ec8c6b | 145 | } |
146 | ||
94ec8c6b | 147 | linenum = 0; |
148 | which = arc4random() % bestcount; | |
149 | while (fgets(line, sizeof(line), f)) { | |
150 | if (!parse_prime(linenum, line, &dhg)) | |
151 | continue; | |
a7ca6275 | 152 | if ((dhg.size > max || dhg.size < min) || |
153 | dhg.size != best || | |
154 | linenum++ != which) { | |
108d362e | 155 | BN_clear_free(dhg.g); |
156 | BN_clear_free(dhg.p); | |
94ec8c6b | 157 | continue; |
158 | } | |
159 | break; | |
160 | } | |
161 | fclose(f); | |
a7ca6275 | 162 | if (linenum != which+1) |
163 | fatal("WARNING: line %d disappeared in %s, giving up", | |
164 | which, _PATH_DH_PRIMES); | |
94ec8c6b | 165 | |
166 | return (dh_new_group(dhg.g, dhg.p)); | |
167 | } | |
03b8f8be | 168 | |
169 | /* diffie-hellman-group1-sha1 */ | |
170 | ||
171 | int | |
172 | dh_pub_is_valid(DH *dh, BIGNUM *dh_pub) | |
173 | { | |
174 | int i; | |
175 | int n = BN_num_bits(dh_pub); | |
176 | int bits_set = 0; | |
177 | ||
178 | if (dh_pub->neg) { | |
179 | log("invalid public DH value: negativ"); | |
180 | return 0; | |
181 | } | |
182 | for (i = 0; i <= n; i++) | |
183 | if (BN_is_bit_set(dh_pub, i)) | |
184 | bits_set++; | |
185 | debug("bits set: %d/%d", bits_set, BN_num_bits(dh->p)); | |
186 | ||
187 | /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */ | |
188 | if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1)) | |
189 | return 1; | |
190 | log("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p)); | |
191 | return 0; | |
192 | } | |
193 | ||
194 | void | |
195 | dh_gen_key(DH *dh, int need) | |
196 | { | |
197 | int i, bits_set = 0, tries = 0; | |
198 | ||
199 | if (dh->p == NULL) | |
200 | fatal("dh_gen_key: dh->p == NULL"); | |
201 | if (2*need >= BN_num_bits(dh->p)) | |
202 | fatal("dh_gen_key: group too small: %d (2*need %d)", | |
203 | BN_num_bits(dh->p), 2*need); | |
204 | do { | |
205 | if (dh->priv_key != NULL) | |
108d362e | 206 | BN_clear_free(dh->priv_key); |
b775c6f2 | 207 | if ((dh->priv_key = BN_new()) == NULL) |
03b8f8be | 208 | fatal("dh_gen_key: BN_new failed"); |
209 | /* generate a 2*need bits random private exponent */ | |
83a9aa63 | 210 | if (!BN_rand(dh->priv_key, 2*need, 0, 0)) |
211 | fatal("dh_gen_key: BN_rand failed"); | |
03b8f8be | 212 | if (DH_generate_key(dh) == 0) |
213 | fatal("DH_generate_key"); | |
214 | for (i = 0; i <= BN_num_bits(dh->priv_key); i++) | |
215 | if (BN_is_bit_set(dh->priv_key, i)) | |
216 | bits_set++; | |
217 | debug("dh_gen_key: priv key bits set: %d/%d", | |
218 | bits_set, BN_num_bits(dh->priv_key)); | |
219 | if (tries++ > 10) | |
220 | fatal("dh_gen_key: too many bad keys: giving up"); | |
221 | } while (!dh_pub_is_valid(dh, dh->pub_key)); | |
222 | } | |
223 | ||
224 | DH * | |
225 | dh_new_group_asc(const char *gen, const char *modulus) | |
226 | { | |
227 | DH *dh; | |
03b8f8be | 228 | |
b775c6f2 | 229 | if ((dh = DH_new()) == NULL) |
230 | fatal("dh_new_group_asc: DH_new"); | |
03b8f8be | 231 | |
ec1f12d3 | 232 | if (BN_hex2bn(&dh->p, modulus) == 0) |
03b8f8be | 233 | fatal("BN_hex2bn p"); |
ec1f12d3 | 234 | if (BN_hex2bn(&dh->g, gen) == 0) |
03b8f8be | 235 | fatal("BN_hex2bn g"); |
236 | ||
237 | return (dh); | |
238 | } | |
239 | ||
240 | /* | |
241 | * This just returns the group, we still need to generate the exchange | |
242 | * value. | |
243 | */ | |
244 | ||
245 | DH * | |
246 | dh_new_group(BIGNUM *gen, BIGNUM *modulus) | |
247 | { | |
248 | DH *dh; | |
249 | ||
b775c6f2 | 250 | if ((dh = DH_new()) == NULL) |
251 | fatal("dh_new_group: DH_new"); | |
03b8f8be | 252 | dh->p = modulus; |
253 | dh->g = gen; | |
254 | ||
255 | return (dh); | |
256 | } | |
257 | ||
258 | DH * | |
259 | dh_new_group1(void) | |
260 | { | |
261 | static char *gen = "2", *group1 = | |
262 | "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" | |
263 | "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" | |
264 | "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" | |
265 | "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" | |
266 | "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381" | |
267 | "FFFFFFFF" "FFFFFFFF"; | |
268 | ||
269 | return (dh_new_group_asc(gen, group1)); | |
270 | } | |
a5c9ffdb | 271 | |
272 | /* | |
273 | * Estimates the group order for a Diffie-Hellman group that has an | |
274 | * attack complexity approximately the same as O(2**bits). Estimate | |
275 | * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3))) | |
276 | */ | |
277 | ||
278 | int | |
279 | dh_estimate(int bits) | |
280 | { | |
281 | ||
282 | if (bits < 64) | |
283 | return (512); /* O(2**63) */ | |
284 | if (bits < 128) | |
285 | return (1024); /* O(2**86) */ | |
286 | if (bits < 192) | |
287 | return (2048); /* O(2**116) */ | |
288 | return (4096); /* O(2**156) */ | |
289 | } |