Annotation of src/usr.bin/ssh/dh.c, Revision 1.66
1.66 ! djm 1: /* $OpenBSD: dh.c,v 1.65 2018/06/26 11:23:59 millert 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:
1.63 jsing 134: BN_clear_free(dhg->g);
135: BN_clear_free(dhg->p);
1.50 djm 136: dhg->g = dhg->p = NULL;
137: return 0;
1.1 provos 138: }
139:
140: DH *
1.9 provos 141: choose_dh(int min, int wantbits, int max)
1.1 provos 142: {
143: FILE *f;
1.64 markus 144: char *line = NULL;
145: size_t linesize = 0;
146: int best, bestcount, which, linenum;
1.1 provos 147: struct dhgroup dhg;
148:
1.59 dtucker 149: if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL) {
1.62 dtucker 150: logit("WARNING: could not open %s (%s), using fixed modulus",
1.59 dtucker 151: _PATH_DH_MODULI, strerror(errno));
1.57 dtucker 152: return (dh_new_group_fallback(max));
1.1 provos 153: }
154:
155: linenum = 0;
156: best = bestcount = 0;
1.64 markus 157: while (getline(&line, &linesize, f) != -1) {
1.1 provos 158: linenum++;
159: if (!parse_prime(linenum, line, &dhg))
160: continue;
1.19 markus 161: BN_clear_free(dhg.g);
162: BN_clear_free(dhg.p);
1.1 provos 163:
1.9 provos 164: if (dhg.size > max || dhg.size < min)
165: continue;
166:
167: if ((dhg.size > wantbits && dhg.size < best) ||
168: (dhg.size > best && best < wantbits)) {
1.1 provos 169: best = dhg.size;
170: bestcount = 0;
171: }
172: if (dhg.size == best)
173: bestcount++;
174: }
1.64 markus 175: free(line);
176: line = NULL;
177: linesize = 0;
1.16 provos 178: rewind(f);
1.1 provos 179:
180: if (bestcount == 0) {
1.16 provos 181: fclose(f);
1.59 dtucker 182: logit("WARNING: no suitable primes in %s", _PATH_DH_MODULI);
1.57 dtucker 183: return (dh_new_group_fallback(max));
1.1 provos 184: }
185:
186: linenum = 0;
1.46 djm 187: which = arc4random_uniform(bestcount);
1.64 markus 188: while (getline(&line, &linesize, f) != -1) {
1.1 provos 189: if (!parse_prime(linenum, line, &dhg))
1.9 provos 190: continue;
1.13 markus 191: if ((dhg.size > max || dhg.size < min) ||
192: dhg.size != best ||
193: linenum++ != which) {
1.19 markus 194: BN_clear_free(dhg.g);
195: BN_clear_free(dhg.p);
1.1 provos 196: continue;
197: }
198: break;
199: }
1.64 markus 200: free(line);
201: line = NULL;
1.1 provos 202: fclose(f);
1.54 markus 203: if (linenum != which+1) {
204: logit("WARNING: line %d disappeared in %s, giving up",
1.59 dtucker 205: which, _PATH_DH_MODULI);
1.57 dtucker 206: return (dh_new_group_fallback(max));
1.54 markus 207: }
1.1 provos 208:
209: return (dh_new_group(dhg.g, dhg.p));
1.11 markus 210: }
211:
1.30 djm 212: /* diffie-hellman-groupN-sha1 */
1.11 markus 213:
214: int
215: dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
216: {
217: int i;
218: int n = BN_num_bits(dh_pub);
219: int bits_set = 0;
1.36 djm 220: BIGNUM *tmp;
1.11 markus 221:
222: if (dh_pub->neg) {
1.45 ray 223: logit("invalid public DH value: negative");
1.11 markus 224: return 0;
225: }
1.36 djm 226: if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
227: logit("invalid public DH value: <= 1");
228: return 0;
229: }
230:
1.45 ray 231: if ((tmp = BN_new()) == NULL) {
232: error("%s: BN_new failed", __func__);
233: return 0;
234: }
1.36 djm 235: if (!BN_sub(tmp, dh->p, BN_value_one()) ||
236: BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
237: BN_clear_free(tmp);
238: logit("invalid public DH value: >= p-1");
239: return 0;
240: }
241: BN_clear_free(tmp);
242:
1.11 markus 243: for (i = 0; i <= n; i++)
244: if (BN_is_bit_set(dh_pub, i))
245: bits_set++;
1.23 markus 246: debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
1.11 markus 247:
1.58 djm 248: /*
249: * if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial
250: */
251: if (bits_set < 4) {
252: logit("invalid public DH value (%d/%d)",
253: bits_set, BN_num_bits(dh->p));
254: return 0;
255: }
256: return 1;
1.11 markus 257: }
258:
1.54 markus 259: int
1.11 markus 260: dh_gen_key(DH *dh, int need)
261: {
1.53 djm 262: int pbits;
1.11 markus 263:
1.54 markus 264: if (need < 0 || dh->p == NULL ||
265: (pbits = BN_num_bits(dh->p)) <= 0 ||
1.56 djm 266: need > INT_MAX / 2 || 2 * need > pbits)
1.54 markus 267: return SSH_ERR_INVALID_ARGUMENT;
1.58 djm 268: if (need < 256)
269: need = 256;
270: /*
271: * Pollard Rho, Big step/Little Step attacks are O(sqrt(n)),
272: * so double requested need here.
273: */
1.61 deraadt 274: dh->length = MINIMUM(need * 2, pbits - 1);
1.54 markus 275: if (DH_generate_key(dh) == 0 ||
276: !dh_pub_is_valid(dh, dh->pub_key)) {
277: BN_clear_free(dh->priv_key);
1.66 ! djm 278: dh->priv_key = NULL;
1.54 markus 279: return SSH_ERR_LIBCRYPTO_ERROR;
280: }
281: return 0;
1.11 markus 282: }
283:
284: DH *
285: dh_new_group_asc(const char *gen, const char *modulus)
286: {
287: DH *dh;
288:
1.18 markus 289: if ((dh = DH_new()) == NULL)
1.54 markus 290: return NULL;
291: if (BN_hex2bn(&dh->p, modulus) == 0 ||
292: BN_hex2bn(&dh->g, gen) == 0) {
293: DH_free(dh);
294: return NULL;
295: }
1.11 markus 296: return (dh);
297: }
298:
299: /*
300: * This just returns the group, we still need to generate the exchange
301: * value.
302: */
303:
304: DH *
305: dh_new_group(BIGNUM *gen, BIGNUM *modulus)
306: {
307: DH *dh;
308:
1.18 markus 309: if ((dh = DH_new()) == NULL)
1.54 markus 310: return NULL;
1.11 markus 311: dh->p = modulus;
312: dh->g = gen;
313:
314: return (dh);
315: }
316:
1.60 djm 317: /* rfc2409 "Second Oakley Group" (1024 bits) */
1.11 markus 318: DH *
319: dh_new_group1(void)
320: {
321: static char *gen = "2", *group1 =
322: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
323: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
324: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
325: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
326: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
327: "FFFFFFFF" "FFFFFFFF";
328:
329: return (dh_new_group_asc(gen, group1));
1.30 djm 330: }
331:
1.60 djm 332: /* rfc3526 group 14 "2048-bit MODP Group" */
1.30 djm 333: DH *
334: dh_new_group14(void)
335: {
336: static char *gen = "2", *group14 =
337: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
338: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
339: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
340: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
341: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
342: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
343: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
344: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
345: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
346: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
347: "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
348:
349: return (dh_new_group_asc(gen, group14));
1.57 dtucker 350: }
351:
1.60 djm 352: /* rfc3526 group 16 "4096-bit MODP Group" */
1.57 dtucker 353: DH *
1.60 djm 354: dh_new_group16(void)
1.57 dtucker 355: {
356: static char *gen = "2", *group16 =
357: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
358: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
359: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
360: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
361: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
362: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
363: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
364: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
365: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
366: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
367: "15728E5A" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64"
368: "ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7"
369: "ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B"
370: "F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C"
371: "BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31"
372: "43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7"
373: "88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA"
374: "2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6"
375: "287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED"
376: "1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9"
377: "93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34063199"
378: "FFFFFFFF" "FFFFFFFF";
379:
1.60 djm 380: return (dh_new_group_asc(gen, group16));
381: }
382:
383: /* rfc3526 group 18 "8192-bit MODP Group" */
384: DH *
385: dh_new_group18(void)
386: {
387: static char *gen = "2", *group16 =
388: "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
389: "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
390: "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
391: "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
392: "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
393: "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
394: "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
395: "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
396: "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
397: "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
398: "15728E5A" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64"
399: "ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7"
400: "ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B"
401: "F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C"
402: "BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31"
403: "43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7"
404: "88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA"
405: "2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6"
406: "287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED"
407: "1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9"
408: "93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34028492"
409: "36C3FAB4" "D27C7026" "C1D4DCB2" "602646DE" "C9751E76" "3DBA37BD"
410: "F8FF9406" "AD9E530E" "E5DB382F" "413001AE" "B06A53ED" "9027D831"
411: "179727B0" "865A8918" "DA3EDBEB" "CF9B14ED" "44CE6CBA" "CED4BB1B"
412: "DB7F1447" "E6CC254B" "33205151" "2BD7AF42" "6FB8F401" "378CD2BF"
413: "5983CA01" "C64B92EC" "F032EA15" "D1721D03" "F482D7CE" "6E74FEF6"
414: "D55E702F" "46980C82" "B5A84031" "900B1C9E" "59E7C97F" "BEC7E8F3"
415: "23A97A7E" "36CC88BE" "0F1D45B7" "FF585AC5" "4BD407B2" "2B4154AA"
416: "CC8F6D7E" "BF48E1D8" "14CC5ED2" "0F8037E0" "A79715EE" "F29BE328"
417: "06A1D58B" "B7C5DA76" "F550AA3D" "8A1FBFF0" "EB19CCB1" "A313D55C"
418: "DA56C9EC" "2EF29632" "387FE8D7" "6E3C0468" "043E8F66" "3F4860EE"
419: "12BF2D5B" "0B7474D6" "E694F91E" "6DBE1159" "74A3926F" "12FEE5E4"
420: "38777CB6" "A932DF8C" "D8BEC4D0" "73B931BA" "3BC832B6" "8D9DD300"
421: "741FA7BF" "8AFC47ED" "2576F693" "6BA42466" "3AAB639C" "5AE4F568"
422: "3423B474" "2BF1C978" "238F16CB" "E39D652D" "E3FDB8BE" "FC848AD9"
423: "22222E04" "A4037C07" "13EB57A8" "1A23F0C7" "3473FC64" "6CEA306B"
424: "4BCBC886" "2F8385DD" "FA9D4B7F" "A2C087E8" "79683303" "ED5BDD3A"
425: "062B3CF5" "B3A278A6" "6D2A13F8" "3F44F82D" "DF310EE0" "74AB6A36"
426: "4597E899" "A0255DC1" "64F31CC5" "0846851D" "F9AB4819" "5DED7EA1"
427: "B1D510BD" "7EE74D73" "FAF36BC3" "1ECFA268" "359046F4" "EB879F92"
428: "4009438B" "481C6CD7" "889A002E" "D5EE382B" "C9190DA6" "FC026E47"
429: "9558E447" "5677E9AA" "9E3050E2" "765694DF" "C81F56E8" "80B96E71"
430: "60C980DD" "98EDD3DF" "FFFFFFFF" "FFFFFFFF";
431:
432: return (dh_new_group_asc(gen, group16));
433: }
434:
435: /* Select fallback group used by DH-GEX if moduli file cannot be read. */
436: DH *
437: dh_new_group_fallback(int max)
438: {
439: debug3("%s: requested max size %d", __func__, max);
440: if (max < 3072) {
441: debug3("using 2k bit group 14");
1.57 dtucker 442: return dh_new_group14();
1.60 djm 443: } else if (max < 6144) {
444: debug3("using 4k bit group 16");
445: return dh_new_group16();
1.57 dtucker 446: }
1.60 djm 447: debug3("using 8k bit group 18");
448: return dh_new_group18();
1.12 markus 449: }
450:
451: /*
452: * Estimates the group order for a Diffie-Hellman group that has an
1.52 dtucker 453: * attack complexity approximately the same as O(2**bits).
454: * Values from NIST Special Publication 800-57: Recommendation for Key
455: * Management Part 1 (rev 3) limited by the recommended maximum value
456: * from RFC4419 section 3.
1.12 markus 457: */
1.54 markus 458: u_int
1.12 markus 459: dh_estimate(int bits)
460: {
1.52 dtucker 461: if (bits <= 112)
462: return 2048;
1.26 markus 463: if (bits <= 128)
1.52 dtucker 464: return 3072;
1.26 markus 465: if (bits <= 192)
1.52 dtucker 466: return 7680;
467: return 8192;
1.1 provos 468: }