diff options
Diffstat (limited to 'dh.c')
-rw-r--r-- | dh.c | 331 |
1 files changed, 331 insertions, 0 deletions
@@ -0,0 +1,331 @@ +/* $OpenBSD: dh.c,v 1.43 2006/11/06 21:25:28 markus 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 <sys/param.h> + +#include <openssl/bn.h> +#include <openssl/dh.h> + +#include <stdarg.h> +#include <stdio.h> +#include <stdlib.h> +#include <string.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; + const char *errstr = 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 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 = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 || + errstr) + 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; + BIGNUM *tmp; + + if (dh_pub->neg) { + logit("invalid public DH value: negativ"); + 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) + return (-1); + 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 > 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) */ +} |