Annotation of src/usr.bin/ssh/dh.c, Revision 1.61
1.61 ! deraadt 1: /* $OpenBSD: dh.c,v 1.60 2016/05/02 10:26:04 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:
1.1 provos 26:
27: #include <openssl/bn.h>
28: #include <openssl/dh.h>
1.38 stevesk 29:
1.59 dtucker 30: #include <errno.h>
1.41 stevesk 31: #include <stdio.h>
1.40 stevesk 32: #include <stdlib.h>
1.38 stevesk 33: #include <string.h>
1.55 deraadt 34: #include <limits.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"
1.54 markus 40: #include "ssherr.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;
1.35 deraadt 47: const char *errstr = NULL;
1.47 djm 48: long long n;
1.1 provos 49:
1.51 markus 50: dhg->p = dhg->g = NULL;
1.1 provos 51: cp = line;
1.32 djm 52: if ((arg = strdelim(&cp)) == NULL)
53: return 0;
1.1 provos 54: /* Ignore leading whitespace */
55: if (*arg == '\0')
56: arg = strdelim(&cp);
1.22 markus 57: if (!arg || !*arg || *arg == '#')
1.1 provos 58: return 0;
59:
60: /* time */
61: if (cp == NULL || *arg == '\0')
1.50 djm 62: goto truncated;
1.1 provos 63: arg = strsep(&cp, " "); /* type */
64: if (cp == NULL || *arg == '\0')
1.50 djm 65: goto truncated;
1.47 djm 66: /* Ensure this is a safe prime */
67: n = strtonum(arg, 0, 5, &errstr);
1.50 djm 68: if (errstr != NULL || n != MODULI_TYPE_SAFE) {
69: error("moduli:%d: type is not %d", linenum, MODULI_TYPE_SAFE);
1.47 djm 70: goto fail;
1.50 djm 71: }
1.1 provos 72: arg = strsep(&cp, " "); /* tests */
73: if (cp == NULL || *arg == '\0')
1.50 djm 74: goto truncated;
1.47 djm 75: /* Ensure prime has been tested and is not composite */
76: n = strtonum(arg, 0, 0x1f, &errstr);
77: if (errstr != NULL ||
1.50 djm 78: (n & MODULI_TESTS_COMPOSITE) || !(n & ~MODULI_TESTS_COMPOSITE)) {
79: error("moduli:%d: invalid moduli tests flag", linenum);
1.47 djm 80: goto fail;
1.50 djm 81: }
1.1 provos 82: arg = strsep(&cp, " "); /* tries */
83: if (cp == NULL || *arg == '\0')
1.50 djm 84: goto truncated;
1.47 djm 85: n = strtonum(arg, 0, 1<<30, &errstr);
1.50 djm 86: if (errstr != NULL || n == 0) {
87: error("moduli:%d: invalid primality trial count", linenum);
1.1 provos 88: goto fail;
1.50 djm 89: }
1.1 provos 90: strsize = strsep(&cp, " "); /* size */
91: if (cp == NULL || *strsize == '\0' ||
1.48 grunk 92: (dhg->size = (int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
1.50 djm 93: errstr) {
94: error("moduli:%d: invalid prime length", linenum);
1.1 provos 95: goto fail;
1.50 djm 96: }
1.9 provos 97: /* The whole group is one bit larger */
98: dhg->size++;
1.1 provos 99: gen = strsep(&cp, " "); /* gen */
100: if (cp == NULL || *gen == '\0')
1.50 djm 101: goto truncated;
1.1 provos 102: prime = strsep(&cp, " "); /* prime */
1.50 djm 103: if (cp != NULL || *prime == '\0') {
104: truncated:
105: error("moduli:%d: truncated", linenum);
1.1 provos 106: goto fail;
1.50 djm 107: }
1.1 provos 108:
1.54 markus 109: if ((dhg->g = BN_new()) == NULL ||
110: (dhg->p = BN_new()) == NULL) {
111: error("parse_prime: BN_new failed");
112: goto fail;
113: }
1.50 djm 114: if (BN_hex2bn(&dhg->g, gen) == 0) {
115: error("moduli:%d: could not parse generator value", linenum);
116: goto fail;
117: }
118: if (BN_hex2bn(&dhg->p, prime) == 0) {
119: error("moduli:%d: could not parse prime value", linenum);
120: goto fail;
121: }
122: if (BN_num_bits(dhg->p) != dhg->size) {
123: error("moduli:%d: prime has wrong size: actual %d listed %d",
124: linenum, BN_num_bits(dhg->p), dhg->size - 1);
125: goto fail;
126: }
127: if (BN_cmp(dhg->g, BN_value_one()) <= 0) {
128: error("moduli:%d: generator is invalid", linenum);
129: goto fail;
130: }
131: return 1;
1.10 provos 132:
1.1 provos 133: fail:
1.50 djm 134: if (dhg->g != NULL)
135: BN_clear_free(dhg->g);
136: if (dhg->p != NULL)
137: BN_clear_free(dhg->p);
138: dhg->g = dhg->p = NULL;
139: return 0;
1.1 provos 140: }
141:
142: DH *
1.9 provos 143: choose_dh(int min, int wantbits, int max)
1.1 provos 144: {
145: FILE *f;
1.28 dtucker 146: char line[4096];
1.1 provos 147: int best, bestcount, which;
148: int linenum;
149: struct dhgroup dhg;
150:
1.59 dtucker 151: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL) {
152: logit("WARNING: could open open %s (%s), using fixed modulus",
153: _PATH_DH_MODULI, strerror(errno));
1.57 dtucker 154: return (dh_new_group_fallback(max));
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);
1.59 dtucker 181: logit("WARNING: no suitable primes in %s", _PATH_DH_MODULI);
1.57 dtucker 182: return (dh_new_group_fallback(max));
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);
1.54 markus 200: if (linenum != which+1) {
201: logit("WARNING: line %d disappeared in %s, giving up",
1.59 dtucker 202: which, _PATH_DH_MODULI);
1.57 dtucker 203: return (dh_new_group_fallback(max));
1.54 markus 204: }
1.1 provos 205:
206: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 207: }
208:
1.30 djm 209: /* diffie-hellman-groupN-sha1 */
1.11 markus 210:
211: int
212: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
213: {
214: int i;
215: int n = BN_num_bits(dh_pub);
216: int bits_set = 0;
1.36 djm 217: BIGNUM *tmp;
1.11 markus 218:
219: if (dh_pub->neg) {
1.45 ray 220: logit("invalid public DH value: negative");
1.11 markus 221: return 0;
222: }
1.36 djm 223: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
224: logit("invalid public DH value: <= 1");
225: return 0;
226: }
227:
1.45 ray 228: if ((tmp = BN_new()) == NULL) {
229: error("%s: BN_new failed", __func__);
230: return 0;
231: }
1.36 djm 232: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
233: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
234: BN_clear_free(tmp);
235: logit("invalid public DH value: >= p-1");
236: return 0;
237: }
238: BN_clear_free(tmp);
239:
1.11 markus 240: for (i = 0; i <= n; i++)
241: if (BN_is_bit_set(dh_pub, i))
242: bits_set++;
1.23 markus 243: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 244:
1.58 djm 245: /*
246: * if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial
247: */
248: if (bits_set < 4) {
249: logit("invalid public DH value (%d/%d)",
250: bits_set, BN_num_bits(dh->p));
251: return 0;
252: }
253: return 1;
1.11 markus 254: }
255:
1.54 markus 256: int
1.11 markus 257: dh_gen_key(DH *dh, int need)
258: {
1.53 djm 259: int pbits;
1.11 markus 260:
1.54 markus 261: if (need < 0 || dh->p == NULL ||
262: (pbits = BN_num_bits(dh->p)) <= 0 ||
1.56 djm 263: need > INT_MAX / 2 || 2 * need > pbits)
1.54 markus 264: return SSH_ERR_INVALID_ARGUMENT;
1.58 djm 265: if (need < 256)
266: need = 256;
267: /*
268: * Pollard Rho, Big step/Little Step attacks are O(sqrt(n)),
269: * so double requested need here.
270: */
1.61 ! deraadt 271: dh->length = MINIMUM(need * 2, pbits - 1);
1.54 markus 272: if (DH_generate_key(dh) == 0 ||
273: !dh_pub_is_valid(dh, dh->pub_key)) {
274: BN_clear_free(dh->priv_key);
275: return SSH_ERR_LIBCRYPTO_ERROR;
276: }
277: return 0;
1.11 markus 278: }
279:
280: DH *
281: dh_new_group_asc(const char *gen, const char *modulus)
282: {
283: DH *dh;
284:
1.18 markus 285: if ((dh = DH_new()) == NULL)
1.54 markus 286: return NULL;
287: if (BN_hex2bn(&dh->p, modulus) == 0 ||
288: BN_hex2bn(&dh->g, gen) == 0) {
289: DH_free(dh);
290: return NULL;
291: }
1.11 markus 292: return (dh);
293: }
294:
295: /*
296: * This just returns the group, we still need to generate the exchange
297: * value.
298: */
299:
300: DH *
301: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
302: {
303: DH *dh;
304:
1.18 markus 305: if ((dh = DH_new()) == NULL)
1.54 markus 306: return NULL;
1.11 markus 307: dh->p = modulus;
308: dh->g = gen;
309:
310: return (dh);
311: }
312:
1.60 djm 313: /* rfc2409 "Second Oakley Group" (1024 bits) */
1.11 markus 314: DH *
315: dh_new_group1(void)
316: {
317: static char *gen = "2", *group1 =
318: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
319: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
320: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
321: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
322: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
323: "FFFFFFFF" "FFFFFFFF";
324:
325: return (dh_new_group_asc(gen, group1));
1.30 djm 326: }
327:
1.60 djm 328: /* rfc3526 group 14 "2048-bit MODP Group" */
1.30 djm 329: DH *
330: dh_new_group14(void)
331: {
332: static char *gen = "2", *group14 =
333: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
334: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
335: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
336: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
337: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
338: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
339: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
340: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
341: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
342: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
343: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
344:
345: return (dh_new_group_asc(gen, group14));
1.57 dtucker 346: }
347:
1.60 djm 348: /* rfc3526 group 16 "4096-bit MODP Group" */
1.57 dtucker 349: DH *
1.60 djm 350: dh_new_group16(void)
1.57 dtucker 351: {
352: static char *gen = "2", *group16 =
353: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
354: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
355: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
356: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
357: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
358: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
359: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
360: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
361: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
362: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
363: "15728E5A" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64"
364: "ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7"
365: "ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B"
366: "F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C"
367: "BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31"
368: "43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7"
369: "88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA"
370: "2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6"
371: "287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED"
372: "1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9"
373: "93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34063199"
374: "FFFFFFFF" "FFFFFFFF";
375:
1.60 djm 376: return (dh_new_group_asc(gen, group16));
377: }
378:
379: /* rfc3526 group 18 "8192-bit MODP Group" */
380: DH *
381: dh_new_group18(void)
382: {
383: static char *gen = "2", *group16 =
384: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
385: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
386: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
387: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
388: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
389: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
390: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
391: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
392: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
393: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
394: "15728E5A" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64"
395: "ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7"
396: "ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B"
397: "F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C"
398: "BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31"
399: "43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7"
400: "88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA"
401: "2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6"
402: "287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED"
403: "1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9"
404: "93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34028492"
405: "36C3FAB4" "D27C7026" "C1D4DCB2" "602646DE" "C9751E76" "3DBA37BD"
406: "F8FF9406" "AD9E530E" "E5DB382F" "413001AE" "B06A53ED" "9027D831"
407: "179727B0" "865A8918" "DA3EDBEB" "CF9B14ED" "44CE6CBA" "CED4BB1B"
408: "DB7F1447" "E6CC254B" "33205151" "2BD7AF42" "6FB8F401" "378CD2BF"
409: "5983CA01" "C64B92EC" "F032EA15" "D1721D03" "F482D7CE" "6E74FEF6"
410: "D55E702F" "46980C82" "B5A84031" "900B1C9E" "59E7C97F" "BEC7E8F3"
411: "23A97A7E" "36CC88BE" "0F1D45B7" "FF585AC5" "4BD407B2" "2B4154AA"
412: "CC8F6D7E" "BF48E1D8" "14CC5ED2" "0F8037E0" "A79715EE" "F29BE328"
413: "06A1D58B" "B7C5DA76" "F550AA3D" "8A1FBFF0" "EB19CCB1" "A313D55C"
414: "DA56C9EC" "2EF29632" "387FE8D7" "6E3C0468" "043E8F66" "3F4860EE"
415: "12BF2D5B" "0B7474D6" "E694F91E" "6DBE1159" "74A3926F" "12FEE5E4"
416: "38777CB6" "A932DF8C" "D8BEC4D0" "73B931BA" "3BC832B6" "8D9DD300"
417: "741FA7BF" "8AFC47ED" "2576F693" "6BA42466" "3AAB639C" "5AE4F568"
418: "3423B474" "2BF1C978" "238F16CB" "E39D652D" "E3FDB8BE" "FC848AD9"
419: "22222E04" "A4037C07" "13EB57A8" "1A23F0C7" "3473FC64" "6CEA306B"
420: "4BCBC886" "2F8385DD" "FA9D4B7F" "A2C087E8" "79683303" "ED5BDD3A"
421: "062B3CF5" "B3A278A6" "6D2A13F8" "3F44F82D" "DF310EE0" "74AB6A36"
422: "4597E899" "A0255DC1" "64F31CC5" "0846851D" "F9AB4819" "5DED7EA1"
423: "B1D510BD" "7EE74D73" "FAF36BC3" "1ECFA268" "359046F4" "EB879F92"
424: "4009438B" "481C6CD7" "889A002E" "D5EE382B" "C9190DA6" "FC026E47"
425: "9558E447" "5677E9AA" "9E3050E2" "765694DF" "C81F56E8" "80B96E71"
426: "60C980DD" "98EDD3DF" "FFFFFFFF" "FFFFFFFF";
427:
428: return (dh_new_group_asc(gen, group16));
429: }
430:
431: /* Select fallback group used by DH-GEX if moduli file cannot be read. */
432: DH *
433: dh_new_group_fallback(int max)
434: {
435: debug3("%s: requested max size %d", __func__, max);
436: if (max < 3072) {
437: debug3("using 2k bit group 14");
1.57 dtucker 438: return dh_new_group14();
1.60 djm 439: } else if (max < 6144) {
440: debug3("using 4k bit group 16");
441: return dh_new_group16();
1.57 dtucker 442: }
1.60 djm 443: debug3("using 8k bit group 18");
444: return dh_new_group18();
1.12 markus 445: }
446:
447: /*
448: * Estimates the group order for a Diffie-Hellman group that has an
1.52 dtucker 449: * attack complexity approximately the same as O(2**bits).
450: * Values from NIST Special Publication 800-57: Recommendation for Key
451: * Management Part 1 (rev 3) limited by the recommended maximum value
452: * from RFC4419 section 3.
1.12 markus 453: */
1.54 markus 454: u_int
1.12 markus 455: dh_estimate(int bits)
456: {
1.52 dtucker 457: if (bits <= 112)
458: return 2048;
1.26 markus 459: if (bits <= 128)
1.52 dtucker 460: return 3072;
1.26 markus 461: if (bits <= 192)
1.52 dtucker 462: return 7680;
463: return 8192;
1.1 provos 464: }
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