Annotation of src/usr.bin/ssh/dh.c, Revision 1.47
1.47 ! djm 1: /* $OpenBSD: dh.c,v 1.46 2008/04/13 00:22:17 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: */
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;
1.47 ! djm 46: long long n;
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;
1.47 ! djm 63: /* Ensure this is a safe prime */
! 64: n = strtonum(arg, 0, 5, &errstr);
! 65: if (errstr != NULL || n != MODULI_TYPE_SAFE)
! 66: goto fail;
1.1 provos 67: arg = strsep(&cp, " "); /* tests */
68: if (cp == NULL || *arg == '\0')
69: goto fail;
1.47 ! djm 70: /* Ensure prime has been tested and is not composite */
! 71: n = strtonum(arg, 0, 0x1f, &errstr);
! 72: if (errstr != NULL ||
! 73: (n & MODULI_TESTS_COMPOSITE) || !(n & ~MODULI_TESTS_COMPOSITE))
! 74: goto fail;
1.1 provos 75: arg = strsep(&cp, " "); /* tries */
76: if (cp == NULL || *arg == '\0')
1.47 ! djm 77: goto fail;
! 78: n = strtonum(arg, 0, 1<<30, &errstr);
! 79: if (errstr != NULL || n == 0)
1.1 provos 80: goto fail;
81: strsize = strsep(&cp, " "); /* size */
82: if (cp == NULL || *strsize == '\0' ||
1.35 deraadt 83: (dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
84: errstr)
1.1 provos 85: goto fail;
1.9 provos 86: /* The whole group is one bit larger */
87: dhg->size++;
1.1 provos 88: gen = strsep(&cp, " "); /* gen */
89: if (cp == NULL || *gen == '\0')
90: goto fail;
91: prime = strsep(&cp, " "); /* prime */
92: if (cp != NULL || *prime == '\0')
93: goto fail;
94:
1.18 markus 95: if ((dhg->g = BN_new()) == NULL)
96: fatal("parse_prime: BN_new failed");
97: if ((dhg->p = BN_new()) == NULL)
98: fatal("parse_prime: BN_new failed");
1.14 markus 99: if (BN_hex2bn(&dhg->g, gen) == 0)
1.10 provos 100: goto failclean;
101:
1.14 markus 102: if (BN_hex2bn(&dhg->p, prime) == 0)
1.10 provos 103: goto failclean;
104:
105: if (BN_num_bits(dhg->p) != dhg->size)
1.27 dtucker 106: goto failclean;
107:
108: if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
1.10 provos 109: goto failclean;
1.1 provos 110:
111: return (1);
1.10 provos 112:
113: failclean:
1.19 markus 114: BN_clear_free(dhg->g);
115: BN_clear_free(dhg->p);
1.1 provos 116: fail:
1.7 millert 117: error("Bad prime description in line %d", linenum);
1.1 provos 118: return (0);
119: }
120:
121: DH *
1.9 provos 122: choose_dh(int min, int wantbits, int max)
1.1 provos 123: {
124: FILE *f;
1.28 dtucker 125: char line[4096];
1.1 provos 126: int best, bestcount, which;
127: int linenum;
128: struct dhgroup dhg;
129:
1.15 provos 130: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
131: (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
1.30 djm 132: logit("WARNING: %s does not exist, using fixed modulus",
133: _PATH_DH_MODULI);
134: return (dh_new_group14());
1.1 provos 135: }
136:
137: linenum = 0;
138: best = bestcount = 0;
139: while (fgets(line, sizeof(line), f)) {
140: linenum++;
141: if (!parse_prime(linenum, line, &dhg))
142: continue;
1.19 markus 143: BN_clear_free(dhg.g);
144: BN_clear_free(dhg.p);
1.1 provos 145:
1.9 provos 146: if (dhg.size > max || dhg.size < min)
147: continue;
148:
149: if ((dhg.size > wantbits && dhg.size < best) ||
150: (dhg.size > best && best < wantbits)) {
1.1 provos 151: best = dhg.size;
152: bestcount = 0;
153: }
154: if (dhg.size == best)
155: bestcount++;
156: }
1.16 provos 157: rewind(f);
1.1 provos 158:
159: if (bestcount == 0) {
1.16 provos 160: fclose(f);
1.24 itojun 161: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.31 djm 162: return (dh_new_group14());
1.1 provos 163: }
164:
165: linenum = 0;
1.46 djm 166: which = arc4random_uniform(bestcount);
1.1 provos 167: while (fgets(line, sizeof(line), f)) {
168: if (!parse_prime(linenum, line, &dhg))
1.9 provos 169: continue;
1.13 markus 170: if ((dhg.size > max || dhg.size < min) ||
171: dhg.size != best ||
172: linenum++ != which) {
1.19 markus 173: BN_clear_free(dhg.g);
174: BN_clear_free(dhg.p);
1.1 provos 175: continue;
176: }
177: break;
178: }
179: fclose(f);
1.13 markus 180: if (linenum != which+1)
181: fatal("WARNING: line %d disappeared in %s, giving up",
182: which, _PATH_DH_PRIMES);
1.1 provos 183:
184: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 185: }
186:
1.30 djm 187: /* diffie-hellman-groupN-sha1 */
1.11 markus 188:
189: int
190: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
191: {
192: int i;
193: int n = BN_num_bits(dh_pub);
194: int bits_set = 0;
1.36 djm 195: BIGNUM *tmp;
1.11 markus 196:
197: if (dh_pub->neg) {
1.45 ray 198: logit("invalid public DH value: negative");
1.11 markus 199: return 0;
200: }
1.36 djm 201: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
202: logit("invalid public DH value: <= 1");
203: return 0;
204: }
205:
1.45 ray 206: if ((tmp = BN_new()) == NULL) {
207: error("%s: BN_new failed", __func__);
208: return 0;
209: }
1.36 djm 210: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
211: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
212: BN_clear_free(tmp);
213: logit("invalid public DH value: >= p-1");
214: return 0;
215: }
216: BN_clear_free(tmp);
217:
1.11 markus 218: for (i = 0; i <= n; i++)
219: if (BN_is_bit_set(dh_pub, i))
220: bits_set++;
1.23 markus 221: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 222:
223: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
1.36 djm 224: if (bits_set > 1)
1.11 markus 225: return 1;
1.36 djm 226:
1.24 itojun 227: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 228: return 0;
229: }
230:
231: void
232: dh_gen_key(DH *dh, int need)
233: {
1.29 dtucker 234: int i, bits_set, tries = 0;
1.11 markus 235:
236: if (dh->p == NULL)
237: fatal("dh_gen_key: dh->p == NULL");
1.25 miod 238: if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
1.11 markus 239: fatal("dh_gen_key: group too small: %d (2*need %d)",
240: BN_num_bits(dh->p), 2*need);
241: do {
242: if (dh->priv_key != NULL)
1.19 markus 243: BN_clear_free(dh->priv_key);
1.18 markus 244: if ((dh->priv_key = BN_new()) == NULL)
1.11 markus 245: fatal("dh_gen_key: BN_new failed");
246: /* generate a 2*need bits random private exponent */
1.21 markus 247: if (!BN_rand(dh->priv_key, 2*need, 0, 0))
248: fatal("dh_gen_key: BN_rand failed");
1.11 markus 249: if (DH_generate_key(dh) == 0)
250: fatal("DH_generate_key");
1.29 dtucker 251: for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
1.11 markus 252: if (BN_is_bit_set(dh->priv_key, i))
253: bits_set++;
1.23 markus 254: debug2("dh_gen_key: priv key bits set: %d/%d",
1.11 markus 255: bits_set, BN_num_bits(dh->priv_key));
256: if (tries++ > 10)
257: fatal("dh_gen_key: too many bad keys: giving up");
258: } while (!dh_pub_is_valid(dh, dh->pub_key));
259: }
260:
261: DH *
262: dh_new_group_asc(const char *gen, const char *modulus)
263: {
264: DH *dh;
265:
1.18 markus 266: if ((dh = DH_new()) == NULL)
267: fatal("dh_new_group_asc: DH_new");
1.11 markus 268:
1.44 markus 269: if (BN_hex2bn(&dh->p, modulus) == 0)
1.11 markus 270: fatal("BN_hex2bn p");
1.44 markus 271: if (BN_hex2bn(&dh->g, gen) == 0)
1.11 markus 272: fatal("BN_hex2bn g");
273:
274: return (dh);
275: }
276:
277: /*
278: * This just returns the group, we still need to generate the exchange
279: * value.
280: */
281:
282: DH *
283: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
284: {
285: DH *dh;
286:
1.18 markus 287: if ((dh = DH_new()) == NULL)
288: fatal("dh_new_group: DH_new");
1.11 markus 289: dh->p = modulus;
290: dh->g = gen;
291:
292: return (dh);
293: }
294:
295: DH *
296: dh_new_group1(void)
297: {
298: static char *gen = "2", *group1 =
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" "ECE65381"
304: "FFFFFFFF" "FFFFFFFF";
305:
306: return (dh_new_group_asc(gen, group1));
1.30 djm 307: }
308:
309: DH *
310: dh_new_group14(void)
311: {
312: static char *gen = "2", *group14 =
313: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
314: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
315: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
316: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
317: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
318: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
319: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
320: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
321: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
322: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
323: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
324:
325: return (dh_new_group_asc(gen, group14));
1.12 markus 326: }
327:
328: /*
329: * Estimates the group order for a Diffie-Hellman group that has an
330: * attack complexity approximately the same as O(2**bits). Estimate
331: * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
332: */
333:
334: int
335: dh_estimate(int bits)
336: {
337:
1.26 markus 338: if (bits <= 128)
1.12 markus 339: return (1024); /* O(2**86) */
1.26 markus 340: if (bits <= 192)
1.12 markus 341: return (2048); /* O(2**116) */
342: return (4096); /* O(2**156) */
1.1 provos 343: }
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