/* $OpenBSD: dh.c,v 1.62 2016/12/15 21:20:41 dtucker 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" #include #include #include #include #include #include #include #include #include "dh.h" #include "pathnames.h" #include "log.h" #include "misc.h" #include "ssherr.h" 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: if (dhg->g != NULL) BN_clear_free(dhg->g); if (dhg->p != NULL) 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[4096]; int best, bestcount, which; int linenum; struct dhgroup dhg; if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL) { logit("WARNING: could not open %s (%s), using fixed modulus", _PATH_DH_MODULI, strerror(errno)); return (dh_new_group_fallback(max)); } linenum = 0; best = bestcount = 0; while (fgets(line, sizeof(line), f)) { 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++; } rewind(f); if (bestcount == 0) { fclose(f); logit("WARNING: no suitable primes in %s", _PATH_DH_MODULI); return (dh_new_group_fallback(max)); } linenum = 0; which = arc4random_uniform(bestcount); while (fgets(line, sizeof(line), f)) { if (!parse_prime(linenum, line, &dhg)) continue; if ((dhg.size > max || dhg.size < min) || dhg.size != best || linenum++ != which) { BN_clear_free(dhg.g); BN_clear_free(dhg.p); continue; } break; } fclose(f); if (linenum != which+1) { logit("WARNING: line %d disappeared in %s, giving up", which, _PATH_DH_MODULI); return (dh_new_group_fallback(max)); } return (dh_new_group(dhg.g, dhg.p)); } /* diffie-hellman-groupN-sha1 */ int dh_pub_is_valid(DH *dh, BIGNUM *dh_pub) { int i; int n = BN_num_bits(dh_pub); int bits_set = 0; BIGNUM *tmp; if (dh_pub->neg) { 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("%s: BN_new failed", __func__); 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; 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. */ dh->length = MINIMUM(need * 2, pbits - 1); if (DH_generate_key(dh) == 0 || !dh_pub_is_valid(dh, dh->pub_key)) { BN_clear_free(dh->priv_key); return SSH_ERR_LIBCRYPTO_ERROR; } return 0; } DH * dh_new_group_asc(const char *gen, const char *modulus) { DH *dh; if ((dh = DH_new()) == NULL) return NULL; if (BN_hex2bn(&dh->p, modulus) == 0 || BN_hex2bn(&dh->g, gen) == 0) { DH_free(dh); return NULL; } return (dh); } /* * 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; dh->p = modulus; dh->g = gen; 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", *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" "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, group16)); } /* Select fallback group used by DH-GEX if moduli file cannot be read. */ DH * dh_new_group_fallback(int max) { debug3("%s: requested max size %d", __func__, 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; }