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2e9cf49069
[dh.c dh.h moduli.c]
when loading moduli from /etc/moduli in sshd(8), check that they
are of the expected "safe prime" structure and have had
appropriate primality tests performed;
feedback and ok dtucker@
347 lines
9.0 KiB
C
347 lines
9.0 KiB
C
/* $OpenBSD: dh.c,v 1.47 2008/06/26 09:19:39 djm Exp $ */
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/*
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* Copyright (c) 2000 Niels Provos. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#include "includes.h"
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#include <sys/param.h>
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#include <openssl/bn.h>
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#include <openssl/dh.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include "dh.h"
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#include "pathnames.h"
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#include "log.h"
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#include "misc.h"
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static int
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parse_prime(int linenum, char *line, struct dhgroup *dhg)
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{
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char *cp, *arg;
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char *strsize, *gen, *prime;
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const char *errstr = NULL;
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long long n;
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cp = line;
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if ((arg = strdelim(&cp)) == NULL)
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return 0;
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/* Ignore leading whitespace */
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if (*arg == '\0')
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arg = strdelim(&cp);
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if (!arg || !*arg || *arg == '#')
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return 0;
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/* time */
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if (cp == NULL || *arg == '\0')
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goto fail;
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arg = strsep(&cp, " "); /* type */
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if (cp == NULL || *arg == '\0')
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goto fail;
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/* Ensure this is a safe prime */
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n = strtonum(arg, 0, 5, &errstr);
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if (errstr != NULL || n != MODULI_TYPE_SAFE)
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goto fail;
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arg = strsep(&cp, " "); /* tests */
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if (cp == NULL || *arg == '\0')
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goto fail;
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/* Ensure prime has been tested and is not composite */
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n = strtonum(arg, 0, 0x1f, &errstr);
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if (errstr != NULL ||
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(n & MODULI_TESTS_COMPOSITE) || !(n & ~MODULI_TESTS_COMPOSITE))
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goto fail;
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arg = strsep(&cp, " "); /* tries */
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if (cp == NULL || *arg == '\0')
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goto fail;
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n = strtonum(arg, 0, 1<<30, &errstr);
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if (errstr != NULL || n == 0)
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goto fail;
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strsize = strsep(&cp, " "); /* size */
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if (cp == NULL || *strsize == '\0' ||
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(dhg->size = (u_int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
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errstr)
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goto fail;
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/* The whole group is one bit larger */
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dhg->size++;
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gen = strsep(&cp, " "); /* gen */
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if (cp == NULL || *gen == '\0')
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goto fail;
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prime = strsep(&cp, " "); /* prime */
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if (cp != NULL || *prime == '\0')
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goto fail;
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if ((dhg->g = BN_new()) == NULL)
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fatal("parse_prime: BN_new failed");
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if ((dhg->p = BN_new()) == NULL)
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fatal("parse_prime: BN_new failed");
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if (BN_hex2bn(&dhg->g, gen) == 0)
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goto failclean;
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if (BN_hex2bn(&dhg->p, prime) == 0)
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goto failclean;
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if (BN_num_bits(dhg->p) != dhg->size)
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goto failclean;
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if (BN_is_zero(dhg->g) || BN_is_one(dhg->g))
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goto failclean;
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return (1);
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failclean:
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BN_clear_free(dhg->g);
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BN_clear_free(dhg->p);
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fail:
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error("Bad prime description in line %d", linenum);
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return (0);
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}
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DH *
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choose_dh(int min, int wantbits, int max)
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{
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FILE *f;
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char line[4096];
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int best, bestcount, which;
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int linenum;
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struct dhgroup dhg;
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if ((f = fopen(_PATH_DH_MODULI, "r")) == NULL &&
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(f = fopen(_PATH_DH_PRIMES, "r")) == NULL) {
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logit("WARNING: %s does not exist, using fixed modulus",
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_PATH_DH_MODULI);
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return (dh_new_group14());
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}
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linenum = 0;
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best = bestcount = 0;
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while (fgets(line, sizeof(line), f)) {
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linenum++;
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if (!parse_prime(linenum, line, &dhg))
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continue;
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BN_clear_free(dhg.g);
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BN_clear_free(dhg.p);
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if (dhg.size > max || dhg.size < min)
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continue;
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if ((dhg.size > wantbits && dhg.size < best) ||
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(dhg.size > best && best < wantbits)) {
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best = dhg.size;
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bestcount = 0;
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}
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if (dhg.size == best)
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bestcount++;
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}
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rewind(f);
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if (bestcount == 0) {
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fclose(f);
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logit("WARNING: no suitable primes in %s", _PATH_DH_PRIMES);
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return (dh_new_group14());
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}
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linenum = 0;
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which = arc4random_uniform(bestcount);
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while (fgets(line, sizeof(line), f)) {
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if (!parse_prime(linenum, line, &dhg))
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continue;
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if ((dhg.size > max || dhg.size < min) ||
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dhg.size != best ||
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linenum++ != which) {
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BN_clear_free(dhg.g);
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BN_clear_free(dhg.p);
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continue;
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}
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break;
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}
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fclose(f);
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if (linenum != which+1)
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fatal("WARNING: line %d disappeared in %s, giving up",
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which, _PATH_DH_PRIMES);
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return (dh_new_group(dhg.g, dhg.p));
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}
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/* diffie-hellman-groupN-sha1 */
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int
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dh_pub_is_valid(DH *dh, BIGNUM *dh_pub)
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{
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int i;
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int n = BN_num_bits(dh_pub);
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int bits_set = 0;
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BIGNUM *tmp;
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if (dh_pub->neg) {
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logit("invalid public DH value: negative");
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return 0;
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}
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if (BN_cmp(dh_pub, BN_value_one()) != 1) { /* pub_exp <= 1 */
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logit("invalid public DH value: <= 1");
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return 0;
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}
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if ((tmp = BN_new()) == NULL) {
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error("%s: BN_new failed", __func__);
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return 0;
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}
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if (!BN_sub(tmp, dh->p, BN_value_one()) ||
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BN_cmp(dh_pub, tmp) != -1) { /* pub_exp > p-2 */
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BN_clear_free(tmp);
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logit("invalid public DH value: >= p-1");
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return 0;
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}
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BN_clear_free(tmp);
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for (i = 0; i <= n; i++)
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if (BN_is_bit_set(dh_pub, i))
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bits_set++;
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debug2("bits set: %d/%d", bits_set, BN_num_bits(dh->p));
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/* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial */
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if (bits_set > 1)
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return 1;
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logit("invalid public DH value (%d/%d)", bits_set, BN_num_bits(dh->p));
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return 0;
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}
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void
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dh_gen_key(DH *dh, int need)
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{
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int i, bits_set, tries = 0;
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if (dh->p == NULL)
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fatal("dh_gen_key: dh->p == NULL");
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if (need > INT_MAX / 2 || 2 * need >= BN_num_bits(dh->p))
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fatal("dh_gen_key: group too small: %d (2*need %d)",
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BN_num_bits(dh->p), 2*need);
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do {
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if (dh->priv_key != NULL)
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BN_clear_free(dh->priv_key);
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if ((dh->priv_key = BN_new()) == NULL)
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fatal("dh_gen_key: BN_new failed");
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/* generate a 2*need bits random private exponent */
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if (!BN_rand(dh->priv_key, 2*need, 0, 0))
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fatal("dh_gen_key: BN_rand failed");
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if (DH_generate_key(dh) == 0)
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fatal("DH_generate_key");
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for (i = 0, bits_set = 0; i <= BN_num_bits(dh->priv_key); i++)
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if (BN_is_bit_set(dh->priv_key, i))
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bits_set++;
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debug2("dh_gen_key: priv key bits set: %d/%d",
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bits_set, BN_num_bits(dh->priv_key));
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if (tries++ > 10)
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fatal("dh_gen_key: too many bad keys: giving up");
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} while (!dh_pub_is_valid(dh, dh->pub_key));
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}
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DH *
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dh_new_group_asc(const char *gen, const char *modulus)
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{
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DH *dh;
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if ((dh = DH_new()) == NULL)
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fatal("dh_new_group_asc: DH_new");
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if (BN_hex2bn(&dh->p, modulus) == 0)
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fatal("BN_hex2bn p");
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if (BN_hex2bn(&dh->g, gen) == 0)
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fatal("BN_hex2bn g");
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return (dh);
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}
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/*
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* This just returns the group, we still need to generate the exchange
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* value.
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*/
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DH *
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dh_new_group(BIGNUM *gen, BIGNUM *modulus)
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{
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DH *dh;
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if ((dh = DH_new()) == NULL)
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fatal("dh_new_group: DH_new");
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dh->p = modulus;
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dh->g = gen;
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return (dh);
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}
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DH *
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dh_new_group1(void)
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{
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static char *gen = "2", *group1 =
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"FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
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"29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
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"EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
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"E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
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"EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE65381"
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"FFFFFFFF" "FFFFFFFF";
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return (dh_new_group_asc(gen, group1));
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}
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DH *
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dh_new_group14(void)
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{
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static char *gen = "2", *group14 =
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"FFFFFFFF" "FFFFFFFF" "C90FDAA2" "2168C234" "C4C6628B" "80DC1CD1"
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"29024E08" "8A67CC74" "020BBEA6" "3B139B22" "514A0879" "8E3404DD"
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"EF9519B3" "CD3A431B" "302B0A6D" "F25F1437" "4FE1356D" "6D51C245"
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"E485B576" "625E7EC6" "F44C42E9" "A637ED6B" "0BFF5CB6" "F406B7ED"
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"EE386BFB" "5A899FA5" "AE9F2411" "7C4B1FE6" "49286651" "ECE45B3D"
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"C2007CB8" "A163BF05" "98DA4836" "1C55D39A" "69163FA8" "FD24CF5F"
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"83655D23" "DCA3AD96" "1C62F356" "208552BB" "9ED52907" "7096966D"
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"670C354E" "4ABC9804" "F1746C08" "CA18217C" "32905E46" "2E36CE3B"
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"E39E772C" "180E8603" "9B2783A2" "EC07A28F" "B5C55DF0" "6F4C52C9"
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"DE2BCBF6" "95581718" "3995497C" "EA956AE5" "15D22618" "98FA0510"
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"15728E5A" "8AACAA68" "FFFFFFFF" "FFFFFFFF";
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return (dh_new_group_asc(gen, group14));
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}
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/*
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* Estimates the group order for a Diffie-Hellman group that has an
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* attack complexity approximately the same as O(2**bits). Estimate
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* with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
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*/
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int
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dh_estimate(int bits)
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{
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if (bits <= 128)
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return (1024); /* O(2**86) */
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if (bits <= 192)
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return (2048); /* O(2**116) */
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return (4096); /* O(2**156) */
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}
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