Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 1 | /* $OpenBSD: dh.c,v 1.55 2015/01/20 23:14:00 deraadt Exp $ */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 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 | */ |
| 25 | |
| 26 | #include "includes.h" |
| 27 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 28 | #include <sys/param.h> /* MIN */ |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 29 | |
| 30 | #include <openssl/bn.h> |
| 31 | #include <openssl/dh.h> |
| 32 | |
| 33 | #include <stdarg.h> |
| 34 | #include <stdio.h> |
| 35 | #include <stdlib.h> |
| 36 | #include <string.h> |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 37 | #include <limits.h> |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 38 | |
| 39 | #include "dh.h" |
| 40 | #include "pathnames.h" |
| 41 | #include "log.h" |
| 42 | #include "misc.h" |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 43 | #include "ssherr.h" |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 44 | |
| 45 | static int |
| 46 | parse_prime(int linenum, char *line, struct dhgroup *dhg) |
| 47 | { |
| 48 | char *cp, *arg; |
| 49 | char *strsize, *gen, *prime; |
| 50 | const char *errstr = NULL; |
| 51 | long long n; |
| 52 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 53 | dhg->p = dhg->g = NULL; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 54 | cp = line; |
| 55 | if ((arg = strdelim(&cp)) == NULL) |
| 56 | return 0; |
| 57 | /* Ignore leading whitespace */ |
| 58 | if (*arg == '\0') |
| 59 | arg = strdelim(&cp); |
| 60 | if (!arg || !*arg || *arg == '#') |
| 61 | return 0; |
| 62 | |
| 63 | /* time */ |
| 64 | if (cp == NULL || *arg == '\0') |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 65 | goto truncated; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 66 | arg = strsep(&cp, " "); /* type */ |
| 67 | if (cp == NULL || *arg == '\0') |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 68 | goto truncated; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 69 | /* Ensure this is a safe prime */ |
| 70 | n = strtonum(arg, 0, 5, &errstr); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 71 | if (errstr != NULL || n != MODULI_TYPE_SAFE) { |
| 72 | error("moduli:%d: type is not %d", linenum, MODULI_TYPE_SAFE); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 73 | goto fail; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 74 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 75 | arg = strsep(&cp, " "); /* tests */ |
| 76 | if (cp == NULL || *arg == '\0') |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 77 | goto truncated; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 78 | /* Ensure prime has been tested and is not composite */ |
| 79 | n = strtonum(arg, 0, 0x1f, &errstr); |
| 80 | if (errstr != NULL || |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 81 | (n & MODULI_TESTS_COMPOSITE) || !(n & ~MODULI_TESTS_COMPOSITE)) { |
| 82 | error("moduli:%d: invalid moduli tests flag", linenum); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 83 | goto fail; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 84 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 85 | arg = strsep(&cp, " "); /* tries */ |
| 86 | if (cp == NULL || *arg == '\0') |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 87 | goto truncated; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 88 | n = strtonum(arg, 0, 1<<30, &errstr); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 89 | if (errstr != NULL || n == 0) { |
| 90 | error("moduli:%d: invalid primality trial count", linenum); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 91 | goto fail; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 92 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 93 | strsize = strsep(&cp, " "); /* size */ |
| 94 | if (cp == NULL || *strsize == '\0' || |
| 95 | (dhg->size = (int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 || |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 96 | errstr) { |
| 97 | error("moduli:%d: invalid prime length", linenum); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 98 | goto fail; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 99 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 100 | /* The whole group is one bit larger */ |
| 101 | dhg->size++; |
| 102 | gen = strsep(&cp, " "); /* gen */ |
| 103 | if (cp == NULL || *gen == '\0') |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 104 | goto truncated; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 105 | prime = strsep(&cp, " "); /* prime */ |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 106 | if (cp != NULL || *prime == '\0') { |
| 107 | truncated: |
| 108 | error("moduli:%d: truncated", linenum); |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 109 | goto fail; |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 110 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 111 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 112 | if ((dhg->g = BN_new()) == NULL || |
| 113 | (dhg->p = BN_new()) == NULL) { |
| 114 | error("parse_prime: BN_new failed"); |
| 115 | goto fail; |
| 116 | } |
| 117 | if (BN_hex2bn(&dhg->g, gen) == 0) { |
| 118 | error("moduli:%d: could not parse generator value", linenum); |
| 119 | goto fail; |
| 120 | } |
| 121 | if (BN_hex2bn(&dhg->p, prime) == 0) { |
| 122 | error("moduli:%d: could not parse prime value", linenum); |
| 123 | goto fail; |
| 124 | } |
| 125 | if (BN_num_bits(dhg->p) != dhg->size) { |
| 126 | error("moduli:%d: prime has wrong size: actual %d listed %d", |
| 127 | linenum, BN_num_bits(dhg->p), dhg->size - 1); |
| 128 | goto fail; |
| 129 | } |
| 130 | if (BN_cmp(dhg->g, BN_value_one()) <= 0) { |
| 131 | error("moduli:%d: generator is invalid", linenum); |
| 132 | goto fail; |
| 133 | } |
| 134 | return 1; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 135 | |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 136 | fail: |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 137 | if (dhg->g != NULL) |
| 138 | BN_clear_free(dhg->g); |
| 139 | if (dhg->p != NULL) |
| 140 | BN_clear_free(dhg->p); |
| 141 | dhg->g = dhg->p = NULL; |
| 142 | return 0; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 143 | } |
| 144 | |
| 145 | DH * |
| 146 | choose_dh(int min, int wantbits, int max) |
| 147 | { |
| 148 | FILE *f; |
| 149 | char line[4096]; |
| 150 | int best, bestcount, which; |
| 151 | int linenum; |
| 152 | struct dhgroup dhg; |
| 153 | |
| 154 | if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL && |
| 155 | (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) { |
| 156 | logit("WARNING: %s does not exist, using fixed modulus", |
| 157 | _PATH_DH_MODULI); |
| 158 | return (dh_new_group14()); |
| 159 | } |
| 160 | |
| 161 | linenum = 0; |
| 162 | best = bestcount = 0; |
| 163 | while (fgets(line, sizeof(line), f)) { |
| 164 | linenum++; |
| 165 | if (!parse_prime(linenum, line, &dhg)) |
| 166 | continue; |
| 167 | BN_clear_free(dhg.g); |
| 168 | BN_clear_free(dhg.p); |
| 169 | |
| 170 | if (dhg.size > max || dhg.size < min) |
| 171 | continue; |
| 172 | |
| 173 | if ((dhg.size > wantbits && dhg.size < best) || |
| 174 | (dhg.size > best && best < wantbits)) { |
| 175 | best = dhg.size; |
| 176 | bestcount = 0; |
| 177 | } |
| 178 | if (dhg.size == best) |
| 179 | bestcount++; |
| 180 | } |
| 181 | rewind(f); |
| 182 | |
| 183 | if (bestcount == 0) { |
| 184 | fclose(f); |
| 185 | logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES); |
| 186 | return (dh_new_group14()); |
| 187 | } |
| 188 | |
| 189 | linenum = 0; |
| 190 | which = arc4random_uniform(bestcount); |
| 191 | while (fgets(line, sizeof(line), f)) { |
| 192 | if (!parse_prime(linenum, line, &dhg)) |
| 193 | continue; |
| 194 | if ((dhg.size > max || dhg.size < min) || |
| 195 | dhg.size != best || |
| 196 | linenum++ != which) { |
| 197 | BN_clear_free(dhg.g); |
| 198 | BN_clear_free(dhg.p); |
| 199 | continue; |
| 200 | } |
| 201 | break; |
| 202 | } |
| 203 | fclose(f); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 204 | if (linenum != which+1) { |
| 205 | logit("WARNING: line %d disappeared in %s, giving up", |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 206 | which, _PATH_DH_PRIMES); |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 207 | return (dh_new_group14()); |
| 208 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 209 | |
| 210 | return (dh_new_group(dhg.g, dhg.p)); |
| 211 | } |
| 212 | |
| 213 | /* diffie-hellman-groupN-sha1 */ |
| 214 | |
| 215 | int |
| 216 | dh_pub_is_valid(DH *dh, BIGNUM *dh_pub) |
| 217 | { |
| 218 | int i; |
| 219 | int n = BN_num_bits(dh_pub); |
| 220 | int bits_set = 0; |
| 221 | BIGNUM *tmp; |
| 222 | |
| 223 | if (dh_pub->neg) { |
| 224 | logit("invalid public DH value: negative"); |
| 225 | return 0; |
| 226 | } |
| 227 | if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */ |
| 228 | logit("invalid public DH value: <= 1"); |
| 229 | return 0; |
| 230 | } |
| 231 | |
| 232 | if ((tmp = BN_new()) == NULL) { |
| 233 | error("%s: BN_new failed", __func__); |
| 234 | return 0; |
| 235 | } |
| 236 | if (!BN_sub(tmp, dh->p, BN_value_one()) || |
| 237 | BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */ |
| 238 | BN_clear_free(tmp); |
| 239 | logit("invalid public DH value: >= p-1"); |
| 240 | return 0; |
| 241 | } |
| 242 | BN_clear_free(tmp); |
| 243 | |
| 244 | for (i = 0; i <= n; i++) |
| 245 | if (BN_is_bit_set(dh_pub, i)) |
| 246 | bits_set++; |
| 247 | debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p)); |
| 248 | |
| 249 | /* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */ |
| 250 | if (bits_set > 1) |
| 251 | return 1; |
| 252 | |
| 253 | logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p)); |
| 254 | return 0; |
| 255 | } |
| 256 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 257 | int |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 258 | dh_gen_key(DH *dh, int need) |
| 259 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 260 | int pbits; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 261 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 262 | if (need < 0 || dh->p == NULL || |
| 263 | (pbits = BN_num_bits(dh->p)) <= 0 || |
| 264 | need > INT_MAX / 2 || 2 * need >= pbits) |
| 265 | return SSH_ERR_INVALID_ARGUMENT; |
| 266 | #if !defined(OPENSSL_IS_BORINGSSL) |
| 267 | /* BoringSSL renamed |length| to |priv_length| to better reflect its |
| 268 | * actual use. Also, BoringSSL recognises common groups and chooses the |
| 269 | * length of the private exponent accoringly. */ |
| 270 | dh->length = MIN(need * 2, pbits - 1); |
| 271 | #endif |
| 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; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 278 | } |
| 279 | |
| 280 | DH * |
| 281 | dh_new_group_asc(const char *gen, const char *modulus) |
| 282 | { |
| 283 | DH *dh; |
| 284 | |
| 285 | if ((dh = DH_new()) == NULL) |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 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 | } |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 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 | |
| 305 | if ((dh = DH_new()) == NULL) |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 306 | return NULL; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 307 | dh->p = modulus; |
| 308 | dh->g = gen; |
| 309 | |
| 310 | return (dh); |
| 311 | } |
| 312 | |
| 313 | DH * |
| 314 | dh_new_group1(void) |
| 315 | { |
| 316 | static char *gen = "2", *group1 = |
| 317 | "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" |
| 318 | "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" |
| 319 | "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" |
| 320 | "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" |
| 321 | "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381" |
| 322 | "FFFFFFFF" "FFFFFFFF"; |
| 323 | |
| 324 | return (dh_new_group_asc(gen, group1)); |
| 325 | } |
| 326 | |
| 327 | DH * |
| 328 | dh_new_group14(void) |
| 329 | { |
| 330 | static char *gen = "2", *group14 = |
| 331 | "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" |
| 332 | "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" |
| 333 | "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" |
| 334 | "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" |
| 335 | "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D" |
| 336 | "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F" |
| 337 | "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D" |
| 338 | "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B" |
| 339 | "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9" |
| 340 | "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510" |
| 341 | "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF"; |
| 342 | |
| 343 | return (dh_new_group_asc(gen, group14)); |
| 344 | } |
| 345 | |
| 346 | /* |
| 347 | * Estimates the group order for a Diffie-Hellman group that has an |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 348 | * attack complexity approximately the same as O(2**bits). |
| 349 | * Values from NIST Special Publication 800-57: Recommendation for Key |
| 350 | * Management Part 1 (rev 3) limited by the recommended maximum value |
| 351 | * from RFC4419 section 3. |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 352 | */ |
| 353 | |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 354 | u_int |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 355 | dh_estimate(int bits) |
| 356 | { |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 357 | if (bits <= 112) |
| 358 | return 2048; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 359 | if (bits <= 128) |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 360 | return 3072; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 361 | if (bits <= 192) |
Adam Langley | d059297 | 2015-03-30 14:49:51 -0700 | [diff] [blame] | 362 | return 7680; |
| 363 | return 8192; |
Greg Hartman | bd77cf7 | 2015-02-25 13:21:06 -0800 | [diff] [blame] | 364 | } |