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Diffstat (limited to 'dh.c')
| -rw-r--r-- | dh.c | 505 |
1 files changed, 505 insertions, 0 deletions
@@ -0,0 +1,505 @@ +/* $OpenBSD: dh.c,v 1.74 2021/04/03 06:18:40 djm Exp $ */ +/* + * Copyright (c) 2000 Niels Provos. All rights reserved. + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR + * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES + * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. + * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, + * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT + * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, + * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY + * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT + * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF + * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + */ + +#include "includes.h" + +#ifdef WITH_OPENSSL + +#include <errno.h> +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.h> +#include <limits.h> + +#include <openssl/bn.h> +#include <openssl/dh.h> + +#include "dh.h" +#include "pathnames.h" +#include "log.h" +#include "misc.h" +#include "ssherr.h" + +#include "openbsd-compat/openssl-compat.h" + +static const char *moduli_filename; + +void dh_set_moduli_file(const char *filename) +{ + moduli_filename = filename; +} + +static const char * get_moduli_filename(void) +{ + return moduli_filename ? moduli_filename : _PATH_DH_MODULI; +} + +static int +parse_prime(int linenum, char *line, struct dhgroup *dhg) +{ + char *cp, *arg; + char *strsize, *gen, *prime; + const char *errstr = NULL; + long long n; + + dhg->p = dhg->g = NULL; + cp = line; + if ((arg = strdelim(&cp)) == NULL) + return 0; + /* Ignore leading whitespace */ + if (*arg == '\0') + arg = strdelim(&cp); + if (!arg || !*arg || *arg == '#') + return 0; + + /* time */ + if (cp == NULL || *arg == '\0') + goto truncated; + arg = strsep(&cp, " "); /* type */ + if (cp == NULL || *arg == '\0') + goto truncated; + /* Ensure this is a safe prime */ + n = strtonum(arg, 0, 5, &errstr); + if (errstr != NULL || n != MODULI_TYPE_SAFE) { + error("moduli:%d: type is not %d", linenum, MODULI_TYPE_SAFE); + goto fail; + } + arg = strsep(&cp, " "); /* tests */ + if (cp == NULL || *arg == '\0') + goto truncated; + /* Ensure prime has been tested and is not composite */ + n = strtonum(arg, 0, 0x1f, &errstr); + if (errstr != NULL || + (n & MODULI_TESTS_COMPOSITE) || !(n & ~MODULI_TESTS_COMPOSITE)) { + error("moduli:%d: invalid moduli tests flag", linenum); + goto fail; + } + arg = strsep(&cp, " "); /* tries */ + if (cp == NULL || *arg == '\0') + goto truncated; + n = strtonum(arg, 0, 1<<30, &errstr); + if (errstr != NULL || n == 0) { + error("moduli:%d: invalid primality trial count", linenum); + goto fail; + } + strsize = strsep(&cp, " "); /* size */ + if (cp == NULL || *strsize == '\0' || + (dhg->size = (int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 || + errstr) { + error("moduli:%d: invalid prime length", linenum); + goto fail; + } + /* The whole group is one bit larger */ + dhg->size++; + gen = strsep(&cp, " "); /* gen */ + if (cp == NULL || *gen == '\0') + goto truncated; + prime = strsep(&cp, " "); /* prime */ + if (cp != NULL || *prime == '\0') { + truncated: + error("moduli:%d: truncated", linenum); + goto fail; + } + + if ((dhg->g = BN_new()) == NULL || + (dhg->p = BN_new()) == NULL) { + error("parse_prime: BN_new failed"); + goto fail; + } + if (BN_hex2bn(&dhg->g, gen) == 0) { + error("moduli:%d: could not parse generator value", linenum); + goto fail; + } + if (BN_hex2bn(&dhg->p, prime) == 0) { + error("moduli:%d: could not parse prime value", linenum); + goto fail; + } + if (BN_num_bits(dhg->p) != dhg->size) { + error("moduli:%d: prime has wrong size: actual %d listed %d", + linenum, BN_num_bits(dhg->p), dhg->size - 1); + goto fail; + } + if (BN_cmp(dhg->g, BN_value_one()) <= 0) { + error("moduli:%d: generator is invalid", linenum); + goto fail; + } + return 1; + + fail: + BN_clear_free(dhg->g); + BN_clear_free(dhg->p); + dhg->g = dhg->p = NULL; + return 0; +} + +DH * +choose_dh(int min, int wantbits, int max) +{ + FILE *f; + char *line = NULL; + size_t linesize = 0; + int best, bestcount, which, linenum; + struct dhgroup dhg; + + if ((f = fopen(get_moduli_filename(), "r")) == NULL) { + logit("WARNING: could not open %s (%s), using fixed modulus", + get_moduli_filename(), strerror(errno)); + return (dh_new_group_fallback(max)); + } + + linenum = 0; + best = bestcount = 0; + while (getline(&line, &linesize, f) != -1) { + linenum++; + if (!parse_prime(linenum, line, &dhg)) + continue; + BN_clear_free(dhg.g); + BN_clear_free(dhg.p); + + if (dhg.size > max || dhg.size < min) + continue; + + if ((dhg.size > wantbits && dhg.size < best) || + (dhg.size > best && best < wantbits)) { + best = dhg.size; + bestcount = 0; + } + if (dhg.size == best) + bestcount++; + } + free(line); + line = NULL; + linesize = 0; + rewind(f); + + if (bestcount == 0) { + fclose(f); + logit("WARNING: no suitable primes in %s", + get_moduli_filename()); + return (dh_new_group_fallback(max)); + } + which = arc4random_uniform(bestcount); + + linenum = 0; + bestcount = 0; + while (getline(&line, &linesize, f) != -1) { + linenum++; + if (!parse_prime(linenum, line, &dhg)) + continue; + if ((dhg.size > max || dhg.size < min) || + dhg.size != best || + bestcount++ != which) { + BN_clear_free(dhg.g); + BN_clear_free(dhg.p); + continue; + } + break; + } + free(line); + line = NULL; + fclose(f); + if (bestcount != which + 1) { + logit("WARNING: selected prime disappeared in %s, giving up", + get_moduli_filename()); + return (dh_new_group_fallback(max)); + } + + return (dh_new_group(dhg.g, dhg.p)); +} + +/* diffie-hellman-groupN-sha1 */ + +int +dh_pub_is_valid(const DH *dh, const BIGNUM *dh_pub) +{ + int i; + int n = BN_num_bits(dh_pub); + int bits_set = 0; + BIGNUM *tmp; + const BIGNUM *dh_p; + + DH_get0_pqg(dh, &dh_p, NULL, NULL); + + if (BN_is_negative(dh_pub)) { + logit("invalid public DH value: negative"); + return 0; + } + if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */ + logit("invalid public DH value: <= 1"); + return 0; + } + + if ((tmp = BN_new()) == NULL) { + error_f("BN_new failed"); + return 0; + } + if (!BN_sub(tmp, dh_p, BN_value_one()) || + BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */ + BN_clear_free(tmp); + logit("invalid public DH value: >= p-1"); + return 0; + } + BN_clear_free(tmp); + + for (i = 0; i <= n; i++) + if (BN_is_bit_set(dh_pub, i)) + bits_set++; + debug2("bits set: %d/%d", bits_set, BN_num_bits(dh_p)); + + /* + * if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial + */ + if (bits_set < 4) { + logit("invalid public DH value (%d/%d)", + bits_set, BN_num_bits(dh_p)); + return 0; + } + return 1; +} + +int +dh_gen_key(DH *dh, int need) +{ + int pbits; + const BIGNUM *dh_p, *pub_key; + + DH_get0_pqg(dh, &dh_p, NULL, NULL); + + if (need < 0 || dh_p == NULL || + (pbits = BN_num_bits(dh_p)) <= 0 || + need > INT_MAX / 2 || 2 * need > pbits) + return SSH_ERR_INVALID_ARGUMENT; + if (need < 256) + need = 256; + /* + * Pollard Rho, Big step/Little Step attacks are O(sqrt(n)), + * so double requested need here. + */ + if (!DH_set_length(dh, MINIMUM(need * 2, pbits - 1))) + return SSH_ERR_LIBCRYPTO_ERROR; + + if (DH_generate_key(dh) == 0) + return SSH_ERR_LIBCRYPTO_ERROR; + DH_get0_key(dh, &pub_key, NULL); + if (!dh_pub_is_valid(dh, pub_key)) + return SSH_ERR_INVALID_FORMAT; + return 0; +} + +DH * +dh_new_group_asc(const char *gen, const char *modulus) +{ + DH *dh; + BIGNUM *dh_p = NULL, *dh_g = NULL; + + if ((dh = DH_new()) == NULL) + return NULL; + if (BN_hex2bn(&dh_p, modulus) == 0 || + BN_hex2bn(&dh_g, gen) == 0) + goto fail; + if (!DH_set0_pqg(dh, dh_p, NULL, dh_g)) + goto fail; + return dh; + fail: + DH_free(dh); + BN_clear_free(dh_p); + BN_clear_free(dh_g); + return NULL; +} + +/* + * This just returns the group, we still need to generate the exchange + * value. + */ +DH * +dh_new_group(BIGNUM *gen, BIGNUM *modulus) +{ + DH *dh; + + if ((dh = DH_new()) == NULL) + return NULL; + if (!DH_set0_pqg(dh, modulus, NULL, gen)) { + DH_free(dh); + return NULL; + } + + return dh; +} + +/* rfc2409 "Second Oakley Group" (1024 bits) */ +DH * +dh_new_group1(void) +{ + static char *gen = "2", *group1 = + "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" + "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" + "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" + "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" + "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381" + "FFFFFFFF" "FFFFFFFF"; + + return (dh_new_group_asc(gen, group1)); +} + +/* rfc3526 group 14 "2048-bit MODP Group" */ +DH * +dh_new_group14(void) +{ + static char *gen = "2", *group14 = + "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" + "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" + "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" + "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" + "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D" + "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F" + "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D" + "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B" + "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9" + "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510" + "15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF"; + + return (dh_new_group_asc(gen, group14)); +} + +/* rfc3526 group 16 "4096-bit MODP Group" */ +DH * +dh_new_group16(void) +{ + static char *gen = "2", *group16 = + "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" + "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" + "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" + "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" + "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D" + "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F" + "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D" + "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B" + "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9" + "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510" + "15728E5A" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64" + "ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7" + "ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B" + "F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C" + "BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31" + "43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7" + "88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA" + "2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6" + "287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED" + "1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9" + "93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34063199" + "FFFFFFFF" "FFFFFFFF"; + + return (dh_new_group_asc(gen, group16)); +} + +/* rfc3526 group 18 "8192-bit MODP Group" */ +DH * +dh_new_group18(void) +{ + static char *gen = "2", *group18 = + "FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1" + "29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD" + "EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245" + "E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED" + "EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D" + "C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F" + "83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D" + "670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B" + "E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9" + "DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510" + "15728E5A" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64" + "ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7" + "ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B" + "F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C" + "BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31" + "43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7" + "88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA" + "2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6" + "287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED" + "1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9" + "93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34028492" + "36C3FAB4" "D27C7026" "C1D4DCB2" "602646DE" "C9751E76" "3DBA37BD" + "F8FF9406" "AD9E530E" "E5DB382F" "413001AE" "B06A53ED" "9027D831" + "179727B0" "865A8918" "DA3EDBEB" "CF9B14ED" "44CE6CBA" "CED4BB1B" + "DB7F1447" "E6CC254B" "33205151" "2BD7AF42" "6FB8F401" "378CD2BF" + "5983CA01" "C64B92EC" "F032EA15" "D1721D03" "F482D7CE" "6E74FEF6" + "D55E702F" "46980C82" "B5A84031" "900B1C9E" "59E7C97F" "BEC7E8F3" + "23A97A7E" "36CC88BE" "0F1D45B7" "FF585AC5" "4BD407B2" "2B4154AA" + "CC8F6D7E" "BF48E1D8" "14CC5ED2" "0F8037E0" "A79715EE" "F29BE328" + "06A1D58B" "B7C5DA76" "F550AA3D" "8A1FBFF0" "EB19CCB1" "A313D55C" + "DA56C9EC" "2EF29632" "387FE8D7" "6E3C0468" "043E8F66" "3F4860EE" + "12BF2D5B" "0B7474D6" "E694F91E" "6DBE1159" "74A3926F" "12FEE5E4" + "38777CB6" "A932DF8C" "D8BEC4D0" "73B931BA" "3BC832B6" "8D9DD300" + "741FA7BF" "8AFC47ED" "2576F693" "6BA42466" "3AAB639C" "5AE4F568" + "3423B474" "2BF1C978" "238F16CB" "E39D652D" "E3FDB8BE" "FC848AD9" + "22222E04" "A4037C07" "13EB57A8" "1A23F0C7" "3473FC64" "6CEA306B" + "4BCBC886" "2F8385DD" "FA9D4B7F" "A2C087E8" "79683303" "ED5BDD3A" + "062B3CF5" "B3A278A6" "6D2A13F8" "3F44F82D" "DF310EE0" "74AB6A36" + "4597E899" "A0255DC1" "64F31CC5" "0846851D" "F9AB4819" "5DED7EA1" + "B1D510BD" "7EE74D73" "FAF36BC3" "1ECFA268" "359046F4" "EB879F92" + "4009438B" "481C6CD7" "889A002E" "D5EE382B" "C9190DA6" "FC026E47" + "9558E447" "5677E9AA" "9E3050E2" "765694DF" "C81F56E8" "80B96E71" + "60C980DD" "98EDD3DF" "FFFFFFFF" "FFFFFFFF"; + + return (dh_new_group_asc(gen, group18)); +} + +/* Select fallback group used by DH-GEX if moduli file cannot be read. */ +DH * +dh_new_group_fallback(int max) +{ + debug3_f("requested max size %d", max); + if (max < 3072) { + debug3("using 2k bit group 14"); + return dh_new_group14(); + } else if (max < 6144) { + debug3("using 4k bit group 16"); + return dh_new_group16(); + } + debug3("using 8k bit group 18"); + return dh_new_group18(); +} + +/* + * Estimates the group order for a Diffie-Hellman group that has an + * attack complexity approximately the same as O(2**bits). + * Values from NIST Special Publication 800-57: Recommendation for Key + * Management Part 1 (rev 3) limited by the recommended maximum value + * from RFC4419 section 3. + */ +u_int +dh_estimate(int bits) +{ + if (bits <= 112) + return 2048; + if (bits <= 128) + return 3072; + if (bits <= 192) + return 7680; + return 8192; +} + +#endif /* WITH_OPENSSL */ |