Annotation of src/usr.bin/ssh/dh.c, Revision 1.53
1.53 ! djm 1: /* $OpenBSD: dh.c,v 1.52 2013/10/08 11:42:13 dtucker 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:
1.51 markus 48: dhg->p = dhg->g = NULL;
1.1 provos 49: cp = line;
1.32 djm 50: if ((arg = strdelim(&cp)) == NULL)
51: return 0;
1.1 provos 52: /* Ignore leading whitespace */
53: if (*arg == '\0')
54: arg = strdelim(&cp);
1.22 markus 55: if (!arg || !*arg || *arg == '#')
1.1 provos 56: return 0;
57:
58: /* time */
59: if (cp == NULL || *arg == '\0')
1.50 djm 60: goto truncated;
1.1 provos 61: arg = strsep(&cp, " "); /* type */
62: if (cp == NULL || *arg == '\0')
1.50 djm 63: goto truncated;
1.47 djm 64: /* Ensure this is a safe prime */
65: n = strtonum(arg, 0, 5, &errstr);
1.50 djm 66: if (errstr != NULL || n != MODULI_TYPE_SAFE) {
67: error("moduli:%d: type is not %d", linenum, MODULI_TYPE_SAFE);
1.47 djm 68: goto fail;
1.50 djm 69: }
1.1 provos 70: arg = strsep(&cp, " "); /* tests */
71: if (cp == NULL || *arg == '\0')
1.50 djm 72: goto truncated;
1.47 djm 73: /* Ensure prime has been tested and is not composite */
74: n = strtonum(arg, 0, 0x1f, &errstr);
75: if (errstr != NULL ||
1.50 djm 76: (n & MODULI_TESTS_COMPOSITE) || !(n & ~MODULI_TESTS_COMPOSITE)) {
77: error("moduli:%d: invalid moduli tests flag", linenum);
1.47 djm 78: goto fail;
1.50 djm 79: }
1.1 provos 80: arg = strsep(&cp, " "); /* tries */
81: if (cp == NULL || *arg == '\0')
1.50 djm 82: goto truncated;
1.47 djm 83: n = strtonum(arg, 0, 1<<30, &errstr);
1.50 djm 84: if (errstr != NULL || n == 0) {
85: error("moduli:%d: invalid primality trial count", linenum);
1.1 provos 86: goto fail;
1.50 djm 87: }
1.1 provos 88: strsize = strsep(&cp, " "); /* size */
89: if (cp == NULL || *strsize == '\0' ||
1.48 grunk 90: (dhg->size = (int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
1.50 djm 91: errstr) {
92: error("moduli:%d: invalid prime length", linenum);
1.1 provos 93: goto fail;
1.50 djm 94: }
1.9 provos 95: /* The whole group is one bit larger */
96: dhg->size++;
1.1 provos 97: gen = strsep(&cp, " "); /* gen */
98: if (cp == NULL || *gen == '\0')
1.50 djm 99: goto truncated;
1.1 provos 100: prime = strsep(&cp, " "); /* prime */
1.50 djm 101: if (cp != NULL || *prime == '\0') {
102: truncated:
103: error("moduli:%d: truncated", linenum);
1.1 provos 104: goto fail;
1.50 djm 105: }
1.1 provos 106:
1.18 markus 107: if ((dhg->g = BN_new()) == NULL)
108: fatal("parse_prime: BN_new failed");
109: if ((dhg->p = BN_new()) == NULL)
110: fatal("parse_prime: BN_new failed");
1.50 djm 111: if (BN_hex2bn(&dhg->g, gen) == 0) {
112: error("moduli:%d: could not parse generator value", linenum);
113: goto fail;
114: }
115: if (BN_hex2bn(&dhg->p, prime) == 0) {
116: error("moduli:%d: could not parse prime value", linenum);
117: goto fail;
118: }
119: if (BN_num_bits(dhg->p) != dhg->size) {
120: error("moduli:%d: prime has wrong size: actual %d listed %d",
121: linenum, BN_num_bits(dhg->p), dhg->size - 1);
122: goto fail;
123: }
124: if (BN_cmp(dhg->g, BN_value_one()) <= 0) {
125: error("moduli:%d: generator is invalid", linenum);
126: goto fail;
127: }
1.1 provos 128:
1.50 djm 129: return 1;
1.10 provos 130:
1.1 provos 131: fail:
1.50 djm 132: if (dhg->g != NULL)
133: BN_clear_free(dhg->g);
134: if (dhg->p != NULL)
135: BN_clear_free(dhg->p);
136: dhg->g = dhg->p = NULL;
1.7 millert 137: error("Bad prime description in line %d", linenum);
1.50 djm 138: return 0;
1.1 provos 139: }
140:
141: DH *
1.9 provos 142: choose_dh(int min, int wantbits, int max)
1.1 provos 143: {
144: FILE *f;
1.28 dtucker 145: char line[4096];
1.1 provos 146: int best, bestcount, which;
147: int linenum;
148: struct dhgroup dhg;
149:
1.15 provos 150: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
151: (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
1.30 djm 152: logit("WARNING: %s does not exist, using fixed modulus",
153: _PATH_DH_MODULI);
154: return (dh_new_group14());
1.1 provos 155: }
156:
157: linenum = 0;
158: best = bestcount = 0;
159: while (fgets(line, sizeof(line), f)) {
160: linenum++;
161: if (!parse_prime(linenum, line, &dhg))
162: continue;
1.19 markus 163: BN_clear_free(dhg.g);
164: BN_clear_free(dhg.p);
1.1 provos 165:
1.9 provos 166: if (dhg.size > max || dhg.size < min)
167: continue;
168:
169: if ((dhg.size > wantbits && dhg.size < best) ||
170: (dhg.size > best && best < wantbits)) {
1.1 provos 171: best = dhg.size;
172: bestcount = 0;
173: }
174: if (dhg.size == best)
175: bestcount++;
176: }
1.16 provos 177: rewind(f);
1.1 provos 178:
179: if (bestcount == 0) {
1.16 provos 180: fclose(f);
1.24 itojun 181: logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
1.31 djm 182: return (dh_new_group14());
1.1 provos 183: }
184:
185: linenum = 0;
1.46 djm 186: which = arc4random_uniform(bestcount);
1.1 provos 187: while (fgets(line, sizeof(line), f)) {
188: if (!parse_prime(linenum, line, &dhg))
1.9 provos 189: continue;
1.13 markus 190: if ((dhg.size > max || dhg.size < min) ||
191: dhg.size != best ||
192: linenum++ != which) {
1.19 markus 193: BN_clear_free(dhg.g);
194: BN_clear_free(dhg.p);
1.1 provos 195: continue;
196: }
197: break;
198: }
199: fclose(f);
1.13 markus 200: if (linenum != which+1)
201: fatal("WARNING: line %d disappeared in %s, giving up",
202: which, _PATH_DH_PRIMES);
1.1 provos 203:
204: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 205: }
206:
1.30 djm 207: /* diffie-hellman-groupN-sha1 */
1.11 markus 208:
209: int
210: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
211: {
212: int i;
213: int n = BN_num_bits(dh_pub);
214: int bits_set = 0;
1.36 djm 215: BIGNUM *tmp;
1.11 markus 216:
217: if (dh_pub->neg) {
1.45 ray 218: logit("invalid public DH value: negative");
1.11 markus 219: return 0;
220: }
1.36 djm 221: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
222: logit("invalid public DH value: <= 1");
223: return 0;
224: }
225:
1.45 ray 226: if ((tmp = BN_new()) == NULL) {
227: error("%s: BN_new failed", __func__);
228: return 0;
229: }
1.36 djm 230: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
231: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
232: BN_clear_free(tmp);
233: logit("invalid public DH value: >= p-1");
234: return 0;
235: }
236: BN_clear_free(tmp);
237:
1.11 markus 238: for (i = 0; i <= n; i++)
239: if (BN_is_bit_set(dh_pub, i))
240: bits_set++;
1.23 markus 241: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 242:
243: /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
1.36 djm 244: if (bits_set > 1)
1.11 markus 245: return 1;
1.36 djm 246:
1.24 itojun 247: logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
1.11 markus 248: return 0;
249: }
250:
251: void
252: dh_gen_key(DH *dh, int need)
253: {
1.53 ! djm 254: int pbits;
1.11 markus 255:
1.53 ! djm 256: if (need <= 0)
! 257: fatal("%s: need <= 0", __func__);
1.11 markus 258: if (dh->p == NULL)
1.53 ! djm 259: fatal("%s: dh->p == NULL", __func__);
! 260: if ((pbits = BN_num_bits(dh->p)) <= 0)
! 261: fatal("%s: bits(p) <= 0", __func__);
! 262: dh->length = MIN(need * 2, pbits - 1);
! 263: if (DH_generate_key(dh) == 0)
! 264: fatal("%s: key generation failed", __func__);
! 265: if (!dh_pub_is_valid(dh, dh->pub_key))
! 266: fatal("%s: generated invalid key", __func__);
1.11 markus 267: }
268:
269: DH *
270: dh_new_group_asc(const char *gen, const char *modulus)
271: {
272: DH *dh;
273:
1.18 markus 274: if ((dh = DH_new()) == NULL)
275: fatal("dh_new_group_asc: DH_new");
1.11 markus 276:
1.44 markus 277: if (BN_hex2bn(&dh->p, modulus) == 0)
1.11 markus 278: fatal("BN_hex2bn p");
1.44 markus 279: if (BN_hex2bn(&dh->g, gen) == 0)
1.11 markus 280: fatal("BN_hex2bn g");
281:
282: return (dh);
283: }
284:
285: /*
286: * This just returns the group, we still need to generate the exchange
287: * value.
288: */
289:
290: DH *
291: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
292: {
293: DH *dh;
294:
1.18 markus 295: if ((dh = DH_new()) == NULL)
296: fatal("dh_new_group: DH_new");
1.11 markus 297: dh->p = modulus;
298: dh->g = gen;
299:
300: return (dh);
301: }
302:
303: DH *
304: dh_new_group1(void)
305: {
306: static char *gen = "2", *group1 =
307: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
308: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
309: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
310: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
311: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
312: "FFFFFFFF" "FFFFFFFF";
313:
314: return (dh_new_group_asc(gen, group1));
1.30 djm 315: }
316:
317: DH *
318: dh_new_group14(void)
319: {
320: static char *gen = "2", *group14 =
321: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
322: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
323: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
324: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
325: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
326: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
327: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
328: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
329: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
330: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
331: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
332:
333: return (dh_new_group_asc(gen, group14));
1.12 markus 334: }
335:
336: /*
337: * Estimates the group order for a Diffie-Hellman group that has an
1.52 dtucker 338: * attack complexity approximately the same as O(2**bits).
339: * Values from NIST Special Publication 800-57: Recommendation for Key
340: * Management Part 1 (rev 3) limited by the recommended maximum value
341: * from RFC4419 section 3.
1.12 markus 342: */
343:
344: int
345: dh_estimate(int bits)
346: {
1.52 dtucker 347: if (bits <= 112)
348: return 2048;
1.26 markus 349: if (bits <= 128)
1.52 dtucker 350: return 3072;
1.26 markus 351: if (bits <= 192)
1.52 dtucker 352: return 7680;
353: return 8192;
1.1 provos 354: }
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