Annotation of src/usr.bin/ssh/dh.c, Revision 1.43
1.43 ! markus 1: /* $OpenBSD: dh.c,v 1.42 2006/08/03 03:34:42 deraadt 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: */
1.39 stevesk 25:
26: #include <sys/param.h>
1.1 provos 27:
28: #include <openssl/bn.h>
29: #include <openssl/dh.h>
1.38 stevesk 30:
1.41 stevesk 31: #include <stdio.h>
1.40 stevesk 32: #include <stdlib.h>
1.38 stevesk 33: #include <string.h>
1.1 provos 34:
35: #include "dh.h"
1.5 markus 36: #include "pathnames.h"
1.6 markus 37: #include "log.h"
38: #include "misc.h"
1.1 provos 39:
1.17 itojun 40: static int
1.1 provos 41: parse_prime(int linenum, char *line, struct dhgroup *dhg)
42: {
43: char *cp, *arg;
44: char *strsize, *gen, *prime;
1.35 deraadt 45: const char *errstr = NULL;
1.1 provos 46:
47: cp = line;
1.32 djm 48: if ((arg = strdelim(&cp)) == NULL)
49: return 0;
1.1 provos 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' ||
1.35 deraadt 70: (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
71: errstr)
1.1 provos 72: goto fail;
1.9 provos 73: /* The whole group is one bit larger */
74: dhg->size++;
1.1 provos 75: gen = strsep(&cp, " "); /* gen */
76: if (cp == NULL || *gen == '\0')
77: goto fail;
78: prime = strsep(&cp, " "); /* prime */
79: if (cp != NULL || *prime == '\0')
80: goto fail;
81:
1.18 markus 82: if ((dhg->g = BN_new()) == NULL)
83: fatal("parse_prime: BN_new failed");
84: if ((dhg->p = BN_new()) == NULL)
85: fatal("parse_prime: BN_new failed");
1.14 markus 86: if (BN_hex2bn(&dhg->g, gen) == 0)
1.10 provos 87: goto failclean;
88:
1.14 markus 89: if (BN_hex2bn(&dhg->p, prime) == 0)
1.10 provos 90: goto failclean;
91:
92: if (BN_num_bits(dhg->p) != dhg->size)
1.27 dtucker 93: goto failclean;
94:
95: if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
1.10 provos 96: goto failclean;
1.1 provos 97:
98: return (1);
1.10 provos 99:
100: failclean:
1.19 markus 101: BN_clear_free(dhg->g);
102: BN_clear_free(dhg->p);
1.1 provos 103: fail:
1.7 millert 104: error("Bad prime description in line %d", linenum);
1.1 provos 105: return (0);
106: }
107:
108: DH *
1.9 provos 109: choose_dh(int min, int wantbits, int max)
1.1 provos 110: {
111: FILE *f;
1.28 dtucker 112: char line[4096];
1.1 provos 113: int best, bestcount, which;
114: int linenum;
115: struct dhgroup dhg;
116:
1.15 provos 117: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
118: (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
1.30 djm 119: logit("WARNING: %s does not exist, using fixed modulus",
120: _PATH_DH_MODULI);
121: return (dh_new_group14());
1.1 provos 122: }
123:
124: linenum = 0;
125: best = bestcount = 0;
126: while (fgets(line, sizeof(line), f)) {
127: linenum++;
128: if (!parse_prime(linenum, line, &dhg))
129: continue;
1.19 markus 130: BN_clear_free(dhg.g);
131: BN_clear_free(dhg.p);
1.1 provos 132:
1.9 provos 133: if (dhg.size > max || dhg.size < min)
134: continue;
135:
136: if ((dhg.size > wantbits && dhg.size < best) ||
137: (dhg.size > best && best < wantbits)) {
1.1 provos 138: best = dhg.size;
139: bestcount = 0;
140: }
141: if (dhg.size == best)
142: bestcount++;
143: }
1.16 provos 144: rewind(f);
1.1 provos 145:
146: if (bestcount == 0) {
1.16 provos 147: fclose(f);
1.24 itojun 148: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.31 djm 149: return (dh_new_group14());
1.1 provos 150: }
151:
152: linenum = 0;
153: which = arc4random() % bestcount;
154: while (fgets(line, sizeof(line), f)) {
155: if (!parse_prime(linenum, line, &dhg))
1.9 provos 156: continue;
1.13 markus 157: if ((dhg.size > max || dhg.size < min) ||
158: dhg.size != best ||
159: linenum++ != which) {
1.19 markus 160: BN_clear_free(dhg.g);
161: BN_clear_free(dhg.p);
1.1 provos 162: continue;
163: }
164: break;
165: }
166: fclose(f);
1.13 markus 167: if (linenum != which+1)
168: fatal("WARNING: line %d disappeared in %s, giving up",
169: which, _PATH_DH_PRIMES);
1.1 provos 170:
171: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 172: }
173:
1.30 djm 174: /* diffie-hellman-groupN-sha1 */
1.11 markus 175:
176: int
177: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
178: {
179: int i;
180: int n = BN_num_bits(dh_pub);
181: int bits_set = 0;
1.36 djm 182: BIGNUM *tmp;
1.11 markus 183:
184: if (dh_pub->neg) {
1.24 itojun 185: logit("invalid public DH value: negativ");
1.11 markus 186: return 0;
187: }
1.36 djm 188: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
189: logit("invalid public DH value: <= 1");
190: return 0;
191: }
192:
193: if ((tmp = BN_new()) == NULL)
194: return (-1);
195: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
196: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
197: BN_clear_free(tmp);
198: logit("invalid public DH value: >= p-1");
199: return 0;
200: }
201: BN_clear_free(tmp);
202:
1.11 markus 203: for (i = 0; i <= n; i++)
204: if (BN_is_bit_set(dh_pub, i))
205: bits_set++;
1.23 markus 206: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 207:
208: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
1.36 djm 209: if (bits_set > 1)
1.11 markus 210: return 1;
1.36 djm 211:
1.24 itojun 212: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 213: return 0;
214: }
215:
216: void
217: dh_gen_key(DH *dh, int need)
218: {
1.29 dtucker 219: int i, bits_set, tries = 0;
1.11 markus 220:
221: if (dh->p == NULL)
222: fatal("dh_gen_key: dh->p == NULL");
1.25 miod 223: if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
1.11 markus 224: fatal("dh_gen_key: group too small: %d (2*need %d)",
225: BN_num_bits(dh->p), 2*need);
226: do {
227: if (dh->priv_key != NULL)
1.19 markus 228: BN_clear_free(dh->priv_key);
1.18 markus 229: if ((dh->priv_key = BN_new()) == NULL)
1.11 markus 230: fatal("dh_gen_key: BN_new failed");
231: /* generate a 2*need bits random private exponent */
1.21 markus 232: if (!BN_rand(dh->priv_key, 2*need, 0, 0))
233: fatal("dh_gen_key: BN_rand failed");
1.11 markus 234: if (DH_generate_key(dh) == 0)
235: fatal("DH_generate_key");
1.29 dtucker 236: for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
1.11 markus 237: if (BN_is_bit_set(dh->priv_key, i))
238: bits_set++;
1.23 markus 239: debug2("dh_gen_key: priv key bits set: %d/%d",
1.11 markus 240: bits_set, BN_num_bits(dh->priv_key));
241: if (tries++ > 10)
242: fatal("dh_gen_key: too many bad keys: giving up");
243: } while (!dh_pub_is_valid(dh, dh->pub_key));
244: }
245:
246: DH *
247: dh_new_group_asc(const char *gen, const char *modulus)
248: {
249: DH *dh;
250:
1.18 markus 251: if ((dh = DH_new()) == NULL)
252: fatal("dh_new_group_asc: DH_new");
1.11 markus 253:
1.43 ! markus 254: if (BN_hex2bn(&dh->p, modulus) == NULL)
1.11 markus 255: fatal("BN_hex2bn p");
1.43 ! markus 256: if (BN_hex2bn(&dh->g, gen) == NULL)
1.11 markus 257: fatal("BN_hex2bn g");
258:
259: return (dh);
260: }
261:
262: /*
263: * This just returns the group, we still need to generate the exchange
264: * value.
265: */
266:
267: DH *
268: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
269: {
270: DH *dh;
271:
1.18 markus 272: if ((dh = DH_new()) == NULL)
273: fatal("dh_new_group: DH_new");
1.11 markus 274: dh->p = modulus;
275: dh->g = gen;
276:
277: return (dh);
278: }
279:
280: DH *
281: dh_new_group1(void)
282: {
283: static char *gen = "2", *group1 =
284: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
285: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
286: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
287: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
288: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
289: "FFFFFFFF" "FFFFFFFF";
290:
291: return (dh_new_group_asc(gen, group1));
1.30 djm 292: }
293:
294: DH *
295: dh_new_group14(void)
296: {
297: static char *gen = "2", *group14 =
298: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
299: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
300: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
301: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
302: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
303: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
304: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
305: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
306: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
307: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
308: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
309:
310: return (dh_new_group_asc(gen, group14));
1.12 markus 311: }
312:
313: /*
314: * Estimates the group order for a Diffie-Hellman group that has an
315: * attack complexity approximately the same as O(2**bits). Estimate
316: * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
317: */
318:
319: int
320: dh_estimate(int bits)
321: {
322:
1.26 markus 323: if (bits <= 128)
1.12 markus 324: return (1024); /* O(2**86) */
1.26 markus 325: if (bits <= 192)
1.12 markus 326: return (2048); /* O(2**116) */
327: return (4096); /* O(2**156) */
1.1 provos 328: }
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