Annotation of src/usr.bin/ssh/dh.c, Revision 1.40
1.40 ! stevesk 1: /* $OpenBSD: dh.c,v 1.39 2006/07/26 02:35:17 stevesk 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"
1.39 stevesk 27:
28: #include <sys/param.h>
1.1 provos 29:
30: #include <openssl/bn.h>
31: #include <openssl/dh.h>
1.38 stevesk 32:
1.40 ! stevesk 33: #include <stdlib.h>
1.38 stevesk 34: #include <string.h>
1.1 provos 35:
36: #include "dh.h"
1.5 markus 37: #include "pathnames.h"
1.6 markus 38: #include "log.h"
39: #include "misc.h"
1.1 provos 40:
1.17 itojun 41: static int
1.1 provos 42: parse_prime(int linenum, char *line, struct dhgroup *dhg)
43: {
44: char *cp, *arg;
45: char *strsize, *gen, *prime;
1.35 deraadt 46: const char *errstr = NULL;
1.1 provos 47:
48: cp = line;
1.32 djm 49: if ((arg = strdelim(&cp)) == NULL)
50: return 0;
1.1 provos 51: /* Ignore leading whitespace */
52: if (*arg == '\0')
53: arg = strdelim(&cp);
1.22 markus 54: if (!arg || !*arg || *arg == '#')
1.1 provos 55: return 0;
56:
57: /* time */
58: if (cp == NULL || *arg == '\0')
59: goto fail;
60: arg = strsep(&cp, " "); /* type */
61: if (cp == NULL || *arg == '\0')
62: goto fail;
63: arg = strsep(&cp, " "); /* tests */
64: if (cp == NULL || *arg == '\0')
65: goto fail;
66: arg = strsep(&cp, " "); /* tries */
67: if (cp == NULL || *arg == '\0')
68: goto fail;
69: strsize = strsep(&cp, " "); /* size */
70: if (cp == NULL || *strsize == '\0' ||
1.35 deraadt 71: (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
72: errstr)
1.1 provos 73: goto fail;
1.9 provos 74: /* The whole group is one bit larger */
75: dhg->size++;
1.1 provos 76: gen = strsep(&cp, " "); /* gen */
77: if (cp == NULL || *gen == '\0')
78: goto fail;
79: prime = strsep(&cp, " "); /* prime */
80: if (cp != NULL || *prime == '\0')
81: goto fail;
82:
1.18 markus 83: if ((dhg->g = BN_new()) == NULL)
84: fatal("parse_prime: BN_new failed");
85: if ((dhg->p = BN_new()) == NULL)
86: fatal("parse_prime: BN_new failed");
1.14 markus 87: if (BN_hex2bn(&dhg->g, gen) == 0)
1.10 provos 88: goto failclean;
89:
1.14 markus 90: if (BN_hex2bn(&dhg->p, prime) == 0)
1.10 provos 91: goto failclean;
92:
93: if (BN_num_bits(dhg->p) != dhg->size)
1.27 dtucker 94: goto failclean;
95:
96: if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
1.10 provos 97: goto failclean;
1.1 provos 98:
99: return (1);
1.10 provos 100:
101: failclean:
1.19 markus 102: BN_clear_free(dhg->g);
103: BN_clear_free(dhg->p);
1.1 provos 104: fail:
1.7 millert 105: error("Bad prime description in line %d", linenum);
1.1 provos 106: return (0);
107: }
108:
109: DH *
1.9 provos 110: choose_dh(int min, int wantbits, int max)
1.1 provos 111: {
112: FILE *f;
1.28 dtucker 113: char line[4096];
1.1 provos 114: int best, bestcount, which;
115: int linenum;
116: struct dhgroup dhg;
117:
1.15 provos 118: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
119: (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
1.30 djm 120: logit("WARNING: %s does not exist, using fixed modulus",
121: _PATH_DH_MODULI);
122: return (dh_new_group14());
1.1 provos 123: }
124:
125: linenum = 0;
126: best = bestcount = 0;
127: while (fgets(line, sizeof(line), f)) {
128: linenum++;
129: if (!parse_prime(linenum, line, &dhg))
130: continue;
1.19 markus 131: BN_clear_free(dhg.g);
132: BN_clear_free(dhg.p);
1.1 provos 133:
1.9 provos 134: if (dhg.size > max || dhg.size < min)
135: continue;
136:
137: if ((dhg.size > wantbits && dhg.size < best) ||
138: (dhg.size > best && best < wantbits)) {
1.1 provos 139: best = dhg.size;
140: bestcount = 0;
141: }
142: if (dhg.size == best)
143: bestcount++;
144: }
1.16 provos 145: rewind(f);
1.1 provos 146:
147: if (bestcount == 0) {
1.16 provos 148: fclose(f);
1.24 itojun 149: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.31 djm 150: return (dh_new_group14());
1.1 provos 151: }
152:
153: linenum = 0;
154: which = arc4random() % bestcount;
155: while (fgets(line, sizeof(line), f)) {
156: if (!parse_prime(linenum, line, &dhg))
1.9 provos 157: continue;
1.13 markus 158: if ((dhg.size > max || dhg.size < min) ||
159: dhg.size != best ||
160: linenum++ != which) {
1.19 markus 161: BN_clear_free(dhg.g);
162: BN_clear_free(dhg.p);
1.1 provos 163: continue;
164: }
165: break;
166: }
167: fclose(f);
1.13 markus 168: if (linenum != which+1)
169: fatal("WARNING: line %d disappeared in %s, giving up",
170: which, _PATH_DH_PRIMES);
1.1 provos 171:
172: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 173: }
174:
1.30 djm 175: /* diffie-hellman-groupN-sha1 */
1.11 markus 176:
177: int
178: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
179: {
180: int i;
181: int n = BN_num_bits(dh_pub);
182: int bits_set = 0;
1.36 djm 183: BIGNUM *tmp;
1.11 markus 184:
185: if (dh_pub->neg) {
1.24 itojun 186: logit("invalid public DH value: negativ");
1.11 markus 187: return 0;
188: }
1.36 djm 189: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
190: logit("invalid public DH value: <= 1");
191: return 0;
192: }
193:
194: if ((tmp = BN_new()) == NULL)
195: return (-1);
196: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
197: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
198: BN_clear_free(tmp);
199: logit("invalid public DH value: >= p-1");
200: return 0;
201: }
202: BN_clear_free(tmp);
203:
1.11 markus 204: for (i = 0; i <= n; i++)
205: if (BN_is_bit_set(dh_pub, i))
206: bits_set++;
1.23 markus 207: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 208:
209: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
1.36 djm 210: if (bits_set > 1)
1.11 markus 211: return 1;
1.36 djm 212:
1.24 itojun 213: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 214: return 0;
215: }
216:
217: void
218: dh_gen_key(DH *dh, int need)
219: {
1.29 dtucker 220: int i, bits_set, tries = 0;
1.11 markus 221:
222: if (dh->p == NULL)
223: fatal("dh_gen_key: dh->p == NULL");
1.25 miod 224: if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
1.11 markus 225: fatal("dh_gen_key: group too small: %d (2*need %d)",
226: BN_num_bits(dh->p), 2*need);
227: do {
228: if (dh->priv_key != NULL)
1.19 markus 229: BN_clear_free(dh->priv_key);
1.18 markus 230: if ((dh->priv_key = BN_new()) == NULL)
1.11 markus 231: fatal("dh_gen_key: BN_new failed");
232: /* generate a 2*need bits random private exponent */
1.21 markus 233: if (!BN_rand(dh->priv_key, 2*need, 0, 0))
234: fatal("dh_gen_key: BN_rand failed");
1.11 markus 235: if (DH_generate_key(dh) == 0)
236: fatal("DH_generate_key");
1.29 dtucker 237: for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
1.11 markus 238: if (BN_is_bit_set(dh->priv_key, i))
239: bits_set++;
1.23 markus 240: debug2("dh_gen_key: priv key bits set: %d/%d",
1.11 markus 241: bits_set, BN_num_bits(dh->priv_key));
242: if (tries++ > 10)
243: fatal("dh_gen_key: too many bad keys: giving up");
244: } while (!dh_pub_is_valid(dh, dh->pub_key));
245: }
246:
247: DH *
248: dh_new_group_asc(const char *gen, const char *modulus)
249: {
250: DH *dh;
251:
1.18 markus 252: if ((dh = DH_new()) == NULL)
253: fatal("dh_new_group_asc: DH_new");
1.11 markus 254:
1.14 markus 255: if (BN_hex2bn(&dh->p, modulus) == 0)
1.11 markus 256: fatal("BN_hex2bn p");
1.14 markus 257: if (BN_hex2bn(&dh->g, gen) == 0)
1.11 markus 258: fatal("BN_hex2bn g");
259:
260: return (dh);
261: }
262:
263: /*
264: * This just returns the group, we still need to generate the exchange
265: * value.
266: */
267:
268: DH *
269: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
270: {
271: DH *dh;
272:
1.18 markus 273: if ((dh = DH_new()) == NULL)
274: fatal("dh_new_group: DH_new");
1.11 markus 275: dh->p = modulus;
276: dh->g = gen;
277:
278: return (dh);
279: }
280:
281: DH *
282: dh_new_group1(void)
283: {
284: static char *gen = "2", *group1 =
285: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
286: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
287: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
288: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
289: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
290: "FFFFFFFF" "FFFFFFFF";
291:
292: return (dh_new_group_asc(gen, group1));
1.30 djm 293: }
294:
295: DH *
296: dh_new_group14(void)
297: {
298: static char *gen = "2", *group14 =
299: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
300: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
301: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
302: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
303: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
304: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
305: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
306: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
307: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
308: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
309: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
310:
311: return (dh_new_group_asc(gen, group14));
1.12 markus 312: }
313:
314: /*
315: * Estimates the group order for a Diffie-Hellman group that has an
316: * attack complexity approximately the same as O(2**bits). Estimate
317: * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
318: */
319:
320: int
321: dh_estimate(int bits)
322: {
323:
1.26 markus 324: if (bits <= 128)
1.12 markus 325: return (1024); /* O(2**86) */
1.26 markus 326: if (bits <= 192)
1.12 markus 327: return (2048); /* O(2**116) */
328: return (4096); /* O(2**156) */
1.1 provos 329: }
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