Annotation of src/usr.bin/ssh/dh.c, Revision 1.37
1.37 ! stevesk 1: /* $OpenBSD: dh.c,v 1.36 2006/05/04 14:55:23 djm Exp $ */
1.1 provos 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 <openssl/bn.h>
29: #include <openssl/dh.h>
30:
31: #include "dh.h"
1.5 markus 32: #include "pathnames.h"
1.6 markus 33: #include "log.h"
34: #include "misc.h"
1.1 provos 35:
1.17 itojun 36: static int
1.1 provos 37: parse_prime(int linenum, char *line, struct dhgroup *dhg)
38: {
39: char *cp, *arg;
40: char *strsize, *gen, *prime;
1.35 deraadt 41: const char *errstr = NULL;
1.1 provos 42:
43: cp = line;
1.32 djm 44: if ((arg = strdelim(&cp)) == NULL)
45: return 0;
1.1 provos 46: /* Ignore leading whitespace */
47: if (*arg == '\0')
48: arg = strdelim(&cp);
1.22 markus 49: if (!arg || !*arg || *arg == '#')
1.1 provos 50: return 0;
51:
52: /* time */
53: if (cp == NULL || *arg == '\0')
54: goto fail;
55: arg = strsep(&cp, " "); /* type */
56: if (cp == NULL || *arg == '\0')
57: goto fail;
58: arg = strsep(&cp, " "); /* tests */
59: if (cp == NULL || *arg == '\0')
60: goto fail;
61: arg = strsep(&cp, " "); /* tries */
62: if (cp == NULL || *arg == '\0')
63: goto fail;
64: strsize = strsep(&cp, " "); /* size */
65: if (cp == NULL || *strsize == '\0' ||
1.35 deraadt 66: (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
67: errstr)
1.1 provos 68: goto fail;
1.9 provos 69: /* The whole group is one bit larger */
70: dhg->size++;
1.1 provos 71: gen = strsep(&cp, " "); /* gen */
72: if (cp == NULL || *gen == '\0')
73: goto fail;
74: prime = strsep(&cp, " "); /* prime */
75: if (cp != NULL || *prime == '\0')
76: goto fail;
77:
1.18 markus 78: if ((dhg->g = BN_new()) == NULL)
79: fatal("parse_prime: BN_new failed");
80: if ((dhg->p = BN_new()) == NULL)
81: fatal("parse_prime: BN_new failed");
1.14 markus 82: if (BN_hex2bn(&dhg->g, gen) == 0)
1.10 provos 83: goto failclean;
84:
1.14 markus 85: if (BN_hex2bn(&dhg->p, prime) == 0)
1.10 provos 86: goto failclean;
87:
88: if (BN_num_bits(dhg->p) != dhg->size)
1.27 dtucker 89: goto failclean;
90:
91: if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
1.10 provos 92: goto failclean;
1.1 provos 93:
94: return (1);
1.10 provos 95:
96: failclean:
1.19 markus 97: BN_clear_free(dhg->g);
98: BN_clear_free(dhg->p);
1.1 provos 99: fail:
1.7 millert 100: error("Bad prime description in line %d", linenum);
1.1 provos 101: return (0);
102: }
103:
104: DH *
1.9 provos 105: choose_dh(int min, int wantbits, int max)
1.1 provos 106: {
107: FILE *f;
1.28 dtucker 108: char line[4096];
1.1 provos 109: int best, bestcount, which;
110: int linenum;
111: struct dhgroup dhg;
112:
1.15 provos 113: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
114: (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
1.30 djm 115: logit("WARNING: %s does not exist, using fixed modulus",
116: _PATH_DH_MODULI);
117: return (dh_new_group14());
1.1 provos 118: }
119:
120: linenum = 0;
121: best = bestcount = 0;
122: while (fgets(line, sizeof(line), f)) {
123: linenum++;
124: if (!parse_prime(linenum, line, &dhg))
125: continue;
1.19 markus 126: BN_clear_free(dhg.g);
127: BN_clear_free(dhg.p);
1.1 provos 128:
1.9 provos 129: if (dhg.size > max || dhg.size < min)
130: continue;
131:
132: if ((dhg.size > wantbits && dhg.size < best) ||
133: (dhg.size > best && best < wantbits)) {
1.1 provos 134: best = dhg.size;
135: bestcount = 0;
136: }
137: if (dhg.size == best)
138: bestcount++;
139: }
1.16 provos 140: rewind(f);
1.1 provos 141:
142: if (bestcount == 0) {
1.16 provos 143: fclose(f);
1.24 itojun 144: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.31 djm 145: return (dh_new_group14());
1.1 provos 146: }
147:
148: linenum = 0;
149: which = arc4random() % bestcount;
150: while (fgets(line, sizeof(line), f)) {
151: if (!parse_prime(linenum, line, &dhg))
1.9 provos 152: continue;
1.13 markus 153: if ((dhg.size > max || dhg.size < min) ||
154: dhg.size != best ||
155: linenum++ != which) {
1.19 markus 156: BN_clear_free(dhg.g);
157: BN_clear_free(dhg.p);
1.1 provos 158: continue;
159: }
160: break;
161: }
162: fclose(f);
1.13 markus 163: if (linenum != which+1)
164: fatal("WARNING: line %d disappeared in %s, giving up",
165: which, _PATH_DH_PRIMES);
1.1 provos 166:
167: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 168: }
169:
1.30 djm 170: /* diffie-hellman-groupN-sha1 */
1.11 markus 171:
172: int
173: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
174: {
175: int i;
176: int n = BN_num_bits(dh_pub);
177: int bits_set = 0;
1.36 djm 178: BIGNUM *tmp;
1.11 markus 179:
180: if (dh_pub->neg) {
1.24 itojun 181: logit("invalid public DH value: negativ");
1.11 markus 182: return 0;
183: }
1.36 djm 184: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
185: logit("invalid public DH value: <= 1");
186: return 0;
187: }
188:
189: if ((tmp = BN_new()) == NULL)
190: return (-1);
191: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
192: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
193: BN_clear_free(tmp);
194: logit("invalid public DH value: >= p-1");
195: return 0;
196: }
197: BN_clear_free(tmp);
198:
1.11 markus 199: for (i = 0; i <= n; i++)
200: if (BN_is_bit_set(dh_pub, i))
201: bits_set++;
1.23 markus 202: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 203:
204: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
1.36 djm 205: if (bits_set > 1)
1.11 markus 206: return 1;
1.36 djm 207:
1.24 itojun 208: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 209: return 0;
210: }
211:
212: void
213: dh_gen_key(DH *dh, int need)
214: {
1.29 dtucker 215: int i, bits_set, tries = 0;
1.11 markus 216:
217: if (dh->p == NULL)
218: fatal("dh_gen_key: dh->p == NULL");
1.25 miod 219: if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
1.11 markus 220: fatal("dh_gen_key: group too small: %d (2*need %d)",
221: BN_num_bits(dh->p), 2*need);
222: do {
223: if (dh->priv_key != NULL)
1.19 markus 224: BN_clear_free(dh->priv_key);
1.18 markus 225: if ((dh->priv_key = BN_new()) == NULL)
1.11 markus 226: fatal("dh_gen_key: BN_new failed");
227: /* generate a 2*need bits random private exponent */
1.21 markus 228: if (!BN_rand(dh->priv_key, 2*need, 0, 0))
229: fatal("dh_gen_key: BN_rand failed");
1.11 markus 230: if (DH_generate_key(dh) == 0)
231: fatal("DH_generate_key");
1.29 dtucker 232: for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
1.11 markus 233: if (BN_is_bit_set(dh->priv_key, i))
234: bits_set++;
1.23 markus 235: debug2("dh_gen_key: priv key bits set: %d/%d",
1.11 markus 236: bits_set, BN_num_bits(dh->priv_key));
237: if (tries++ > 10)
238: fatal("dh_gen_key: too many bad keys: giving up");
239: } while (!dh_pub_is_valid(dh, dh->pub_key));
240: }
241:
242: DH *
243: dh_new_group_asc(const char *gen, const char *modulus)
244: {
245: DH *dh;
246:
1.18 markus 247: if ((dh = DH_new()) == NULL)
248: fatal("dh_new_group_asc: DH_new");
1.11 markus 249:
1.14 markus 250: if (BN_hex2bn(&dh->p, modulus) == 0)
1.11 markus 251: fatal("BN_hex2bn p");
1.14 markus 252: if (BN_hex2bn(&dh->g, gen) == 0)
1.11 markus 253: fatal("BN_hex2bn g");
254:
255: return (dh);
256: }
257:
258: /*
259: * This just returns the group, we still need to generate the exchange
260: * value.
261: */
262:
263: DH *
264: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
265: {
266: DH *dh;
267:
1.18 markus 268: if ((dh = DH_new()) == NULL)
269: fatal("dh_new_group: DH_new");
1.11 markus 270: dh->p = modulus;
271: dh->g = gen;
272:
273: return (dh);
274: }
275:
276: DH *
277: dh_new_group1(void)
278: {
279: static char *gen = "2", *group1 =
280: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
281: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
282: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
283: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
284: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
285: "FFFFFFFF" "FFFFFFFF";
286:
287: return (dh_new_group_asc(gen, group1));
1.30 djm 288: }
289:
290: DH *
291: dh_new_group14(void)
292: {
293: static char *gen = "2", *group14 =
294: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
295: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
296: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
297: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
298: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
299: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
300: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
301: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
302: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
303: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
304: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
305:
306: return (dh_new_group_asc(gen, group14));
1.12 markus 307: }
308:
309: /*
310: * Estimates the group order for a Diffie-Hellman group that has an
311: * attack complexity approximately the same as O(2**bits). Estimate
312: * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
313: */
314:
315: int
316: dh_estimate(int bits)
317: {
318:
1.26 markus 319: if (bits <= 128)
1.12 markus 320: return (1024); /* O(2**86) */
1.26 markus 321: if (bits <= 192)
1.12 markus 322: return (2048); /* O(2**116) */
323: return (4096); /* O(2**156) */
1.1 provos 324: }
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