Annotation of src/usr.bin/ssh/dh.c, Revision 1.31
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"
1.31 ! djm 26: RCSID("$OpenBSD: dh.c,v 1.30 2004/06/13 12:53:24 djm 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) {
1.30 djm 118: logit("WARNING: %s does not exist, using fixed modulus",
119: _PATH_DH_MODULI);
120: return (dh_new_group14());
1.1 provos 121: }
122:
123: linenum = 0;
124: best = bestcount = 0;
125: while (fgets(line, sizeof(line), f)) {
126: linenum++;
127: if (!parse_prime(linenum, line, &dhg))
128: continue;
1.19 markus 129: BN_clear_free(dhg.g);
130: BN_clear_free(dhg.p);
1.1 provos 131:
1.9 provos 132: if (dhg.size > max || dhg.size < min)
133: continue;
134:
135: if ((dhg.size > wantbits && dhg.size < best) ||
136: (dhg.size > best && best < wantbits)) {
1.1 provos 137: best = dhg.size;
138: bestcount = 0;
139: }
140: if (dhg.size == best)
141: bestcount++;
142: }
1.16 provos 143: rewind(f);
1.1 provos 144:
145: if (bestcount == 0) {
1.16 provos 146: fclose(f);
1.24 itojun 147: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.31 ! djm 148: return (dh_new_group14());
1.1 provos 149: }
150:
151: linenum = 0;
152: which = arc4random() % bestcount;
153: while (fgets(line, sizeof(line), f)) {
154: if (!parse_prime(linenum, line, &dhg))
1.9 provos 155: continue;
1.13 markus 156: if ((dhg.size > max || dhg.size < min) ||
157: dhg.size != best ||
158: linenum++ != which) {
1.19 markus 159: BN_clear_free(dhg.g);
160: BN_clear_free(dhg.p);
1.1 provos 161: continue;
162: }
163: break;
164: }
165: fclose(f);
1.13 markus 166: if (linenum != which+1)
167: fatal("WARNING: line %d disappeared in %s, giving up",
168: which, _PATH_DH_PRIMES);
1.1 provos 169:
170: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 171: }
172:
1.30 djm 173: /* diffie-hellman-groupN-sha1 */
1.11 markus 174:
175: int
176: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
177: {
178: int i;
179: int n = BN_num_bits(dh_pub);
180: int bits_set = 0;
181:
182: if (dh_pub->neg) {
1.24 itojun 183: logit("invalid public DH value: negativ");
1.11 markus 184: return 0;
185: }
186: for (i = 0; i <= n; i++)
187: if (BN_is_bit_set(dh_pub, i))
188: bits_set++;
1.23 markus 189: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 190:
191: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
192: if (bits_set > 1 && (BN_cmp(dh_pub, dh->p) == -1))
193: return 1;
1.24 itojun 194: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 195: return 0;
196: }
197:
198: void
199: dh_gen_key(DH *dh, int need)
200: {
1.29 dtucker 201: int i, bits_set, tries = 0;
1.11 markus 202:
203: if (dh->p == NULL)
204: fatal("dh_gen_key: dh->p == NULL");
1.25 miod 205: if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
1.11 markus 206: fatal("dh_gen_key: group too small: %d (2*need %d)",
207: BN_num_bits(dh->p), 2*need);
208: do {
209: if (dh->priv_key != NULL)
1.19 markus 210: BN_clear_free(dh->priv_key);
1.18 markus 211: if ((dh->priv_key = BN_new()) == NULL)
1.11 markus 212: fatal("dh_gen_key: BN_new failed");
213: /* generate a 2*need bits random private exponent */
1.21 markus 214: if (!BN_rand(dh->priv_key, 2*need, 0, 0))
215: fatal("dh_gen_key: BN_rand failed");
1.11 markus 216: if (DH_generate_key(dh) == 0)
217: fatal("DH_generate_key");
1.29 dtucker 218: for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
1.11 markus 219: if (BN_is_bit_set(dh->priv_key, i))
220: bits_set++;
1.23 markus 221: debug2("dh_gen_key: priv key bits set: %d/%d",
1.11 markus 222: bits_set, BN_num_bits(dh->priv_key));
223: if (tries++ > 10)
224: fatal("dh_gen_key: too many bad keys: giving up");
225: } while (!dh_pub_is_valid(dh, dh->pub_key));
226: }
227:
228: DH *
229: dh_new_group_asc(const char *gen, const char *modulus)
230: {
231: DH *dh;
232:
1.18 markus 233: if ((dh = DH_new()) == NULL)
234: fatal("dh_new_group_asc: DH_new");
1.11 markus 235:
1.14 markus 236: if (BN_hex2bn(&dh->p, modulus) == 0)
1.11 markus 237: fatal("BN_hex2bn p");
1.14 markus 238: if (BN_hex2bn(&dh->g, gen) == 0)
1.11 markus 239: fatal("BN_hex2bn g");
240:
241: return (dh);
242: }
243:
244: /*
245: * This just returns the group, we still need to generate the exchange
246: * value.
247: */
248:
249: DH *
250: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
251: {
252: DH *dh;
253:
1.18 markus 254: if ((dh = DH_new()) == NULL)
255: fatal("dh_new_group: DH_new");
1.11 markus 256: dh->p = modulus;
257: dh->g = gen;
258:
259: return (dh);
260: }
261:
262: DH *
263: dh_new_group1(void)
264: {
265: static char *gen = "2", *group1 =
266: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
267: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
268: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
269: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
270: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
271: "FFFFFFFF" "FFFFFFFF";
272:
273: return (dh_new_group_asc(gen, group1));
1.30 djm 274: }
275:
276: DH *
277: dh_new_group14(void)
278: {
279: static char *gen = "2", *group14 =
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" "ECE45B3D"
285: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
286: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
287: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
288: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
289: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
290: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
291:
292: return (dh_new_group_asc(gen, group14));
1.12 markus 293: }
294:
295: /*
296: * Estimates the group order for a Diffie-Hellman group that has an
297: * attack complexity approximately the same as O(2**bits). Estimate
298: * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
299: */
300:
301: int
302: dh_estimate(int bits)
303: {
304:
1.26 markus 305: if (bits <= 128)
1.12 markus 306: return (1024); /* O(2**86) */
1.26 markus 307: if (bits <= 192)
1.12 markus 308: return (2048); /* O(2**116) */
309: return (4096); /* O(2**156) */
1.1 provos 310: }
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