Annotation of src/usr.bin/ssh/dh.c, Revision 1.28
1.1 provos 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"
1.28 ! dtucker 26: RCSID("$OpenBSD: dh.c,v 1.27 2004/02/27 22:42:47 dtucker Exp $");
1.1 provos 27:
28: #include "xmalloc.h"
29:
30: #include <openssl/bn.h>
31: #include <openssl/dh.h>
32: #include <openssl/evp.h>
33:
34: #include "buffer.h"
1.6 markus 35: #include "cipher.h"
1.1 provos 36: #include "kex.h"
37: #include "dh.h"
1.5 markus 38: #include "pathnames.h"
1.6 markus 39: #include "log.h"
40: #include "misc.h"
1.1 provos 41:
1.17 itojun 42: static int
1.1 provos 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);
1.22 markus 53: if (!arg || !*arg || *arg == '#')
1.1 provos 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;
1.9 provos 72: /* The whole group is one bit larger */
73: dhg->size++;
1.1 provos 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:
1.18 markus 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");
1.14 markus 85: if (BN_hex2bn(&dhg->g, gen) == 0)
1.10 provos 86: goto failclean;
87:
1.14 markus 88: if (BN_hex2bn(&dhg->p, prime) == 0)
1.10 provos 89: goto failclean;
90:
91: if (BN_num_bits(dhg->p) != dhg->size)
1.27 dtucker 92: goto failclean;
93:
94: if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
1.10 provos 95: goto failclean;
1.1 provos 96:
97: return (1);
1.10 provos 98:
99: failclean:
1.19 markus 100: BN_clear_free(dhg->g);
101: BN_clear_free(dhg->p);
1.1 provos 102: fail:
1.7 millert 103: error("Bad prime description in line %d", linenum);
1.1 provos 104: return (0);
105: }
106:
107: DH *
1.9 provos 108: choose_dh(int min, int wantbits, int max)
1.1 provos 109: {
110: FILE *f;
1.28 ! dtucker 111: char line[4096];
1.1 provos 112: int best, bestcount, which;
113: int linenum;
114: struct dhgroup dhg;
115:
1.15 provos 116: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
117: (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
1.24 itojun 118: logit("WARNING: %s does not exist, using old modulus", _PATH_DH_MODULI);
1.1 provos 119: return (dh_new_group1());
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;
1.19 markus 128: BN_clear_free(dhg.g);
129: BN_clear_free(dhg.p);
1.1 provos 130:
1.9 provos 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)) {
1.1 provos 136: best = dhg.size;
137: bestcount = 0;
138: }
139: if (dhg.size == best)
140: bestcount++;
141: }
1.16 provos 142: rewind(f);
1.1 provos 143:
144: if (bestcount == 0) {
1.16 provos 145: fclose(f);
1.24 itojun 146: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.9 provos 147: return (NULL);
1.1 provos 148: }
149:
150: linenum = 0;
151: which = arc4random() % bestcount;
152: while (fgets(line, sizeof(line), f)) {
153: if (!parse_prime(linenum, line, &dhg))
1.9 provos 154: continue;
1.13 markus 155: if ((dhg.size > max || dhg.size < min) ||
156: dhg.size != best ||
157: linenum++ != which) {
1.19 markus 158: BN_clear_free(dhg.g);
159: BN_clear_free(dhg.p);
1.1 provos 160: continue;
161: }
162: break;
163: }
164: fclose(f);
1.13 markus 165: if (linenum != which+1)
166: fatal("WARNING: line %d disappeared in %s, giving up",
167: which, _PATH_DH_PRIMES);
1.1 provos 168:
169: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 170: }
171:
172: /* diffie-hellman-group1-sha1 */
173:
174: int
175: dh_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) {
1.24 itojun 182: logit("invalid public DH value: negativ");
1.11 markus 183: return 0;
184: }
185: for (i = 0; i <= n; i++)
186: if (BN_is_bit_set(dh_pub, i))
187: bits_set++;
1.23 markus 188: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 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;
1.24 itojun 193: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 194: return 0;
195: }
196:
197: void
198: dh_gen_key(DH *dh, int need)
199: {
200: int i, bits_set = 0, tries = 0;
201:
202: if (dh->p == NULL)
203: fatal("dh_gen_key: dh->p == NULL");
1.25 miod 204: if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
1.11 markus 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)
1.19 markus 209: BN_clear_free(dh->priv_key);
1.18 markus 210: if ((dh->priv_key = BN_new()) == NULL)
1.11 markus 211: fatal("dh_gen_key: BN_new failed");
212: /* generate a 2*need bits random private exponent */
1.21 markus 213: if (!BN_rand(dh->priv_key, 2*need, 0, 0))
214: fatal("dh_gen_key: BN_rand failed");
1.11 markus 215: if (DH_generate_key(dh) == 0)
216: fatal("DH_generate_key");
217: for (i = 0; i <= BN_num_bits(dh->priv_key); i++)
218: if (BN_is_bit_set(dh->priv_key, i))
219: bits_set++;
1.23 markus 220: debug2("dh_gen_key: priv key bits set: %d/%d",
1.11 markus 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:
227: DH *
228: dh_new_group_asc(const char *gen, const char *modulus)
229: {
230: DH *dh;
231:
1.18 markus 232: if ((dh = DH_new()) == NULL)
233: fatal("dh_new_group_asc: DH_new");
1.11 markus 234:
1.14 markus 235: if (BN_hex2bn(&dh->p, modulus) == 0)
1.11 markus 236: fatal("BN_hex2bn p");
1.14 markus 237: if (BN_hex2bn(&dh->g, gen) == 0)
1.11 markus 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:
248: DH *
249: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
250: {
251: DH *dh;
252:
1.18 markus 253: if ((dh = DH_new()) == NULL)
254: fatal("dh_new_group: DH_new");
1.11 markus 255: dh->p = modulus;
256: dh->g = gen;
257:
258: return (dh);
259: }
260:
261: DH *
262: dh_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));
1.12 markus 273: }
274:
275: /*
276: * Estimates the group order for a Diffie-Hellman group that has an
277: * attack complexity approximately the same as O(2**bits). Estimate
278: * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
279: */
280:
281: int
282: dh_estimate(int bits)
283: {
284:
1.26 markus 285: if (bits <= 128)
1.12 markus 286: return (1024); /* O(2**86) */
1.26 markus 287: if (bits <= 192)
1.12 markus 288: return (2048); /* O(2**116) */
289: return (4096); /* O(2**156) */
1.1 provos 290: }
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