468 lines
15 KiB
C
468 lines
15 KiB
C
/* $OpenBSD: dh.c,v 1.62 2016/12/15 21:20:41 dtucker 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 <openssl/bn.h>
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#include <openssl/dh.h>
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#include <errno.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 <limits.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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#include "ssherr.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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dhg->p = dhg->g = NULL;
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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 truncated;
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arg = strsep(&cp, " "); /* type */
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if (cp == NULL || *arg == '\0')
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goto truncated;
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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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error("moduli:%d: type is not %d", linenum, MODULI_TYPE_SAFE);
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goto fail;
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}
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arg = strsep(&cp, " "); /* tests */
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if (cp == NULL || *arg == '\0')
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goto truncated;
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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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error("moduli:%d: invalid moduli tests flag", linenum);
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goto fail;
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}
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arg = strsep(&cp, " "); /* tries */
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if (cp == NULL || *arg == '\0')
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goto truncated;
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n = strtonum(arg, 0, 1<<30, &errstr);
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if (errstr != NULL || n == 0) {
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error("moduli:%d: invalid primality trial count", linenum);
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goto fail;
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}
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strsize = strsep(&cp, " "); /* size */
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if (cp == NULL || *strsize == '\0' ||
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(dhg->size = (int)strtonum(strsize, 0, 64*1024, &errstr)) == 0 ||
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errstr) {
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error("moduli:%d: invalid prime length", linenum);
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goto fail;
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}
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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 truncated;
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prime = strsep(&cp, " "); /* prime */
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if (cp != NULL || *prime == '\0') {
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truncated:
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error("moduli:%d: truncated", linenum);
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goto fail;
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}
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if ((dhg->g = BN_new()) == NULL ||
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(dhg->p = BN_new()) == NULL) {
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error("parse_prime: BN_new failed");
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goto fail;
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}
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if (BN_hex2bn(&dhg->g, gen) == 0) {
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error("moduli:%d: could not parse generator value", linenum);
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goto fail;
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}
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if (BN_hex2bn(&dhg->p, prime) == 0) {
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error("moduli:%d: could not parse prime value", linenum);
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goto fail;
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}
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if (BN_num_bits(dhg->p) != dhg->size) {
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error("moduli:%d: prime has wrong size: actual %d listed %d",
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linenum, BN_num_bits(dhg->p), dhg->size - 1);
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goto fail;
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}
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if (BN_cmp(dhg->g, BN_value_one()) <= 0) {
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error("moduli:%d: generator is invalid", linenum);
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goto fail;
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}
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return 1;
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fail:
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if (dhg->g != NULL)
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BN_clear_free(dhg->g);
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if (dhg->p != NULL)
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BN_clear_free(dhg->p);
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dhg->g = dhg->p = NULL;
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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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logit("WARNING: could not open %s (%s), using fixed modulus",
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_PATH_DH_MODULI, strerror(errno));
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return (dh_new_group_fallback(max));
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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_MODULI);
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return (dh_new_group_fallback(max));
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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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logit("WARNING: line %d disappeared in %s, giving up",
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which, _PATH_DH_MODULI);
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return (dh_new_group_fallback(max));
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}
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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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/*
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* if g==2 and bits_set==1 then computing log_g(dh_pub) is trivial
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*/
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if (bits_set < 4) {
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logit("invalid public DH value (%d/%d)",
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bits_set, BN_num_bits(dh->p));
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return 0;
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}
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return 1;
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}
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int
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dh_gen_key(DH *dh, int need)
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{
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int pbits;
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if (need < 0 || dh->p == NULL ||
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(pbits = BN_num_bits(dh->p)) <= 0 ||
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need > INT_MAX / 2 || 2 * need > pbits)
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return SSH_ERR_INVALID_ARGUMENT;
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if (need < 256)
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need = 256;
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/*
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* Pollard Rho, Big step/Little Step attacks are O(sqrt(n)),
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* so double requested need here.
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*/
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dh->length = MINIMUM(need * 2, pbits - 1);
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if (DH_generate_key(dh) == 0 ||
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!dh_pub_is_valid(dh, dh->pub_key)) {
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BN_clear_free(dh->priv_key);
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return SSH_ERR_LIBCRYPTO_ERROR;
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}
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return 0;
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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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return NULL;
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if (BN_hex2bn(&dh->p, modulus) == 0 ||
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BN_hex2bn(&dh->g, gen) == 0) {
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DH_free(dh);
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return NULL;
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}
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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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return NULL;
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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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/* rfc2409 "Second Oakley Group" (1024 bits) */
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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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/* rfc3526 group 14 "2048-bit MODP Group" */
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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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/* rfc3526 group 16 "4096-bit MODP Group" */
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DH *
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dh_new_group16(void)
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{
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static char *gen = "2", *group16 =
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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" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64"
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"ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7"
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"ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B"
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"F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C"
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"BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31"
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"43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7"
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"88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA"
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"2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6"
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"287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED"
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"1F612970" "CEE2D7AF" "B81BDD76" "2170481C" "D0069127" "D5B05AA9"
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"93B4EA98" "8D8FDDC1" "86FFB7DC" "90A6C08F" "4DF435C9" "34063199"
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"FFFFFFFF" "FFFFFFFF";
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return (dh_new_group_asc(gen, group16));
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}
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/* rfc3526 group 18 "8192-bit MODP Group" */
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DH *
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dh_new_group18(void)
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{
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static char *gen = "2", *group16 =
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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" "8AAAC42D" "AD33170D" "04507A33" "A85521AB" "DF1CBA64"
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"ECFB8504" "58DBEF0A" "8AEA7157" "5D060C7D" "B3970F85" "A6E1E4C7"
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"ABF5AE8C" "DB0933D7" "1E8C94E0" "4A25619D" "CEE3D226" "1AD2EE6B"
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"F12FFA06" "D98A0864" "D8760273" "3EC86A64" "521F2B18" "177B200C"
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"BBE11757" "7A615D6C" "770988C0" "BAD946E2" "08E24FA0" "74E5AB31"
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"43DB5BFC" "E0FD108E" "4B82D120" "A9210801" "1A723C12" "A787E6D7"
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"88719A10" "BDBA5B26" "99C32718" "6AF4E23C" "1A946834" "B6150BDA"
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"2583E9CA" "2AD44CE8" "DBBBC2DB" "04DE8EF9" "2E8EFC14" "1FBECAA6"
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"287C5947" "4E6BC05D" "99B2964F" "A090C3A2" "233BA186" "515BE7ED"
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"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;
|
|
}
|