]> andersk Git - openssh.git/blame - dh.c
- djm@cvs.openbsd.org 2006/03/19 02:23:26
[openssh.git] / dh.c
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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"
94ec8c6b 26
27#include "xmalloc.h"
28
29#include <openssl/bn.h>
30#include <openssl/dh.h>
31#include <openssl/evp.h>
32
94ec8c6b 33#include "buffer.h"
42f11eb2 34#include "cipher.h"
94ec8c6b 35#include "kex.h"
36#include "dh.h"
42f11eb2 37#include "pathnames.h"
38#include "log.h"
39#include "misc.h"
94ec8c6b 40
396c147e 41static int
94ec8c6b 42parse_prime(int linenum, char *line, struct dhgroup *dhg)
43{
44 char *cp, *arg;
45 char *strsize, *gen, *prime;
46
47 cp = line;
48 arg = strdelim(&cp);
49 /* Ignore leading whitespace */
50 if (*arg == '\0')
51 arg = strdelim(&cp);
f11fe301 52 if (!arg || !*arg || *arg == '#')
94ec8c6b 53 return 0;
54
55 /* time */
56 if (cp == NULL || *arg == '\0')
57 goto fail;
58 arg = strsep(&cp, " "); /* type */
59 if (cp == NULL || *arg == '\0')
60 goto fail;
61 arg = strsep(&cp, " "); /* tests */
62 if (cp == NULL || *arg == '\0')
63 goto fail;
64 arg = strsep(&cp, " "); /* tries */
65 if (cp == NULL || *arg == '\0')
66 goto fail;
67 strsize = strsep(&cp, " "); /* size */
68 if (cp == NULL || *strsize == '\0' ||
69 (dhg->size = atoi(strsize)) == 0)
70 goto fail;
db1cd2f3 71 /* The whole group is one bit larger */
72 dhg->size++;
94ec8c6b 73 gen = strsep(&cp, " "); /* gen */
74 if (cp == NULL || *gen == '\0')
75 goto fail;
76 prime = strsep(&cp, " "); /* prime */
77 if (cp != NULL || *prime == '\0')
78 goto fail;
79
b775c6f2 80 if ((dhg->g = BN_new()) == NULL)
81 fatal("parse_prime: BN_new failed");
82 if ((dhg->p = BN_new()) == NULL)
83 fatal("parse_prime: BN_new failed");
ec1f12d3 84 if (BN_hex2bn(&dhg->g, gen) == 0)
c8682232 85 goto failclean;
86
ec1f12d3 87 if (BN_hex2bn(&dhg->p, prime) == 0)
c8682232 88 goto failclean;
89
90 if (BN_num_bits(dhg->p) != dhg->size)
91 goto failclean;
94ec8c6b 92
8b0a55ac 93 if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
94 goto failclean;
95
94ec8c6b 96 return (1);
c8682232 97
98 failclean:
108d362e 99 BN_clear_free(dhg->g);
100 BN_clear_free(dhg->p);
94ec8c6b 101 fail:
54b974dc 102 error("Bad prime description in line %d", linenum);
94ec8c6b 103 return (0);
104}
105
106DH *
db1cd2f3 107choose_dh(int min, int wantbits, int max)
94ec8c6b 108{
109 FILE *f;
cd744742 110 char line[4096];
94ec8c6b 111 int best, bestcount, which;
112 int linenum;
113 struct dhgroup dhg;
114
e2854364 115 if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
116 (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
41e5bd9a 117 logit("WARNING: %s does not exist, using fixed modulus",
118 _PATH_DH_MODULI);
119 return (dh_new_group14());
94ec8c6b 120 }
121
122 linenum = 0;
123 best = bestcount = 0;
124 while (fgets(line, sizeof(line), f)) {
125 linenum++;
126 if (!parse_prime(linenum, line, &dhg))
127 continue;
108d362e 128 BN_clear_free(dhg.g);
129 BN_clear_free(dhg.p);
94ec8c6b 130
db1cd2f3 131 if (dhg.size > max || dhg.size < min)
132 continue;
133
134 if ((dhg.size > wantbits && dhg.size < best) ||
135 (dhg.size > best && best < wantbits)) {
94ec8c6b 136 best = dhg.size;
137 bestcount = 0;
138 }
139 if (dhg.size == best)
140 bestcount++;
141 }
826676b3 142 rewind(f);
94ec8c6b 143
144 if (bestcount == 0) {
826676b3 145 fclose(f);
bbe88b6d 146 logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
0875a0a2 147 return (dh_new_group14());
94ec8c6b 148 }
149
94ec8c6b 150 linenum = 0;
151 which = arc4random() % bestcount;
152 while (fgets(line, sizeof(line), f)) {
153 if (!parse_prime(linenum, line, &dhg))
154 continue;
a7ca6275 155 if ((dhg.size > max || dhg.size < min) ||
156 dhg.size != best ||
157 linenum++ != which) {
108d362e 158 BN_clear_free(dhg.g);
159 BN_clear_free(dhg.p);
94ec8c6b 160 continue;
161 }
162 break;
163 }
164 fclose(f);
a7ca6275 165 if (linenum != which+1)
166 fatal("WARNING: line %d disappeared in %s, giving up",
167 which, _PATH_DH_PRIMES);
94ec8c6b 168
169 return (dh_new_group(dhg.g, dhg.p));
170}
03b8f8be 171
41e5bd9a 172/* diffie-hellman-groupN-sha1 */
03b8f8be 173
174int
175dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
176{
177 int i;
178 int n = BN_num_bits(dh_pub);
179 int bits_set = 0;
180
181 if (dh_pub->neg) {
bbe88b6d 182 logit("invalid public DH value: negativ");
03b8f8be 183 return 0;
184 }
185 for (i = 0; i <= n; i++)
186 if (BN_is_bit_set(dh_pub, i))
187 bits_set++;
35efb24c 188 debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
03b8f8be 189
190 /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
191 if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1))
192 return 1;
bbe88b6d 193 logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
03b8f8be 194 return 0;
195}
196
197void
198dh_gen_key(DH *dh, int need)
199{
e24bb7d5 200 int i, bits_set, tries = 0;
03b8f8be 201
202 if (dh->p == NULL)
203 fatal("dh_gen_key: dh->p == NULL");
bb92e5cc 204 if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
03b8f8be 205 fatal("dh_gen_key: group too small: %d (2*need %d)",
206 BN_num_bits(dh->p), 2*need);
207 do {
208 if (dh->priv_key != NULL)
108d362e 209 BN_clear_free(dh->priv_key);
b775c6f2 210 if ((dh->priv_key = BN_new()) == NULL)
03b8f8be 211 fatal("dh_gen_key: BN_new failed");
212 /* generate a 2*need bits random private exponent */
83a9aa63 213 if (!BN_rand(dh->priv_key, 2*need, 0, 0))
214 fatal("dh_gen_key: BN_rand failed");
03b8f8be 215 if (DH_generate_key(dh) == 0)
216 fatal("DH_generate_key");
e24bb7d5 217 for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
03b8f8be 218 if (BN_is_bit_set(dh->priv_key, i))
219 bits_set++;
35efb24c 220 debug2("dh_gen_key: priv key bits set: %d/%d",
03b8f8be 221 bits_set, BN_num_bits(dh->priv_key));
222 if (tries++ > 10)
223 fatal("dh_gen_key: too many bad keys: giving up");
224 } while (!dh_pub_is_valid(dh, dh->pub_key));
225}
226
227DH *
228dh_new_group_asc(const char *gen, const char *modulus)
229{
230 DH *dh;
03b8f8be 231
b775c6f2 232 if ((dh = DH_new()) == NULL)
233 fatal("dh_new_group_asc: DH_new");
03b8f8be 234
ec1f12d3 235 if (BN_hex2bn(&dh->p, modulus) == 0)
03b8f8be 236 fatal("BN_hex2bn p");
ec1f12d3 237 if (BN_hex2bn(&dh->g, gen) == 0)
03b8f8be 238 fatal("BN_hex2bn g");
239
240 return (dh);
241}
242
243/*
244 * This just returns the group, we still need to generate the exchange
245 * value.
246 */
247
248DH *
249dh_new_group(BIGNUM *gen, BIGNUM *modulus)
250{
251 DH *dh;
252
b775c6f2 253 if ((dh = DH_new()) == NULL)
254 fatal("dh_new_group: DH_new");
03b8f8be 255 dh->p = modulus;
256 dh->g = gen;
257
258 return (dh);
259}
260
261DH *
262dh_new_group1(void)
263{
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";
271
272 return (dh_new_group_asc(gen, group1));
273}
a5c9ffdb 274
41e5bd9a 275DH *
276dh_new_group14(void)
277{
278 static char *gen = "2", *group14 =
279 "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
280 "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
281 "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
282 "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
283 "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
284 "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
285 "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
286 "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
287 "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
288 "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
289 "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
290
291 return (dh_new_group_asc(gen, group14));
292}
293
a5c9ffdb 294/*
295 * Estimates the group order for a Diffie-Hellman group that has an
296 * attack complexity approximately the same as O(2**bits). Estimate
297 * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
298 */
299
300int
301dh_estimate(int bits)
302{
303
b3c35b71 304 if (bits <= 128)
a5c9ffdb 305 return (1024); /* O(2**86) */
b3c35b71 306 if (bits <= 192)
a5c9ffdb 307 return (2048); /* O(2**116) */
308 return (4096); /* O(2**156) */
309}
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