/* * 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" RCSID("$OpenBSD: dh.c,v 1.31 2004/08/04 10:37:52 djm Exp $"); #include "xmalloc.h" #include #include #include #include "buffer.h" #include "cipher.h" #include "kex.h" #include "dh.h" #include "pathnames.h" #include "log.h" #include "misc.h" static int parse_prime(int linenum, char *line, struct dhgroup *dhg) { char *cp, *arg; char *strsize, *gen, *prime; cp = line; arg = strdelim(&cp); /* Ignore leading whitespace */ if (*arg == '\0') arg = strdelim(&cp); if (!arg || !*arg || *arg == '#') return 0; /* time */ if (cp == NULL || *arg == '\0') goto fail; arg = strsep(&cp, " "); /* type */ if (cp == NULL || *arg == '\0') goto fail; arg = strsep(&cp, " "); /* tests */ if (cp == NULL || *arg == '\0') goto fail; arg = strsep(&cp, " "); /* tries */ if (cp == NULL || *arg == '\0') goto fail; strsize = strsep(&cp, " "); /* size */ if (cp == NULL || *strsize == '\0' || (dhg->size = atoi(strsize)) == 0) goto fail; /* The whole group is one bit larger */ dhg->size++; gen = strsep(&cp, " "); /* gen */ if (cp == NULL || *gen == '\0') goto fail; prime = strsep(&cp, " "); /* prime */ if (cp != NULL || *prime == '\0') goto fail; if ((dhg->g = BN_new()) == NULL) fatal("parse_prime: BN_new failed"); if ((dhg->p = BN_new()) == NULL) fatal("parse_prime: BN_new failed"); if (BN_hex2bn(&dhg->g, gen) == 0) goto failclean; if (BN_hex2bn(&dhg->p, prime) == 0) goto failclean; if (BN_num_bits(dhg->p) != dhg->size) goto failclean; if (BN_is_zero(dhg->g) || BN_is_one(dhg->g)) goto failclean; return (1); failclean: BN_clear_free(dhg->g); BN_clear_free(dhg->p); fail: error("Bad prime description in line %d", linenum); 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 && (f = fopen(_PATH_DH_PRIMES, "r")) == NULL) { logit("WARNING: %s does not exist, using fixed modulus", _PATH_DH_MODULI); return (dh_new_group14()); } 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_PRIMES); return (dh_new_group14()); } linenum = 0; which = arc4random() % 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) fatal("WARNING: line %d disappeared in %s, giving up", which, _PATH_DH_PRIMES); 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; if (dh_pub->neg) { logit("invalid public DH value: negativ"); return 0; } 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 > 1 && (BN_cmp(dh_pub, dh->p) == -1)) return 1; logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p)); return 0; } void dh_gen_key(DH *dh, int need) { int i, bits_set, tries = 0; if (dh->p == NULL) fatal("dh_gen_key: dh->p == NULL"); if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p)) fatal("dh_gen_key: group too small: %d (2*need %d)", BN_num_bits(dh->p), 2*need); do { if (dh->priv_key != NULL) BN_clear_free(dh->priv_key); if ((dh->priv_key = BN_new()) == NULL) fatal("dh_gen_key: BN_new failed"); /* generate a 2*need bits random private exponent */ if (!BN_rand(dh->priv_key, 2*need, 0, 0)) fatal("dh_gen_key: BN_rand failed"); if (DH_generate_key(dh) == 0) fatal("DH_generate_key"); for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++) if (BN_is_bit_set(dh->priv_key, i)) bits_set++; debug2("dh_gen_key: priv key bits set: %d/%d", bits_set, BN_num_bits(dh->priv_key)); if (tries++ > 10) fatal("dh_gen_key: too many bad keys: giving up"); } while (!dh_pub_is_valid(dh, dh->pub_key)); } DH * dh_new_group_asc(const char *gen, const char *modulus) { DH *dh; if ((dh = DH_new()) == NULL) fatal("dh_new_group_asc: DH_new"); if (BN_hex2bn(&dh->p, modulus) == 0) fatal("BN_hex2bn p"); if (BN_hex2bn(&dh->g, gen) == 0) fatal("BN_hex2bn g"); 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) fatal("dh_new_group: DH_new"); dh->p = modulus; dh->g = gen; return (dh); } 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)); } 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)); } /* * Estimates the group order for a Diffie-Hellman group that has an * attack complexity approximately the same as O(2**bits). Estimate * with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3))) */ int dh_estimate(int bits) { if (bits <= 128) return (1024); /* O(2**86) */ if (bits <= 192) return (2048); /* O(2**116) */ return (4096); /* O(2**156) */ }