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|
/* $OpenBSD: dh.c,v 1.74 2021/04/03 06:18:40 djm 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 <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include <openssl/bn.h>
#include <openssl/dh.h>
#include "dh.h"
#include "pathnames.h"
#include "log.h"
#include "misc.h"
#include "ssherr.h"
static const char *moduli_filename;
void dh_set_moduli_file(const char *filename)
{
moduli_filename = filename;
}
static const char * get_moduli_filename(void)
{
return moduli_filename ? moduli_filename : _PATH_DH_MODULI;
}
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:
BN_clear_free(dhg->g);
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 = NULL;
size_t linesize = 0;
int best, bestcount, which, linenum;
struct dhgroup dhg;
if ((f = fopen(get_moduli_filename(), "r")) == NULL) {
logit("WARNING: could not open %s (%s), using fixed modulus",
get_moduli_filename(), strerror(errno));
return (dh_new_group_fallback(max));
}
linenum = 0;
best = bestcount = 0;
while (getline(&line, &linesize, f) != -1) {
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++;
}
free(line);
line = NULL;
linesize = 0;
rewind(f);
if (bestcount == 0) {
fclose(f);
logit("WARNING: no suitable primes in %s",
get_moduli_filename());
return (dh_new_group_fallback(max));
}
which = arc4random_uniform(bestcount);
linenum = 0;
bestcount = 0;
while (getline(&line, &linesize, f) != -1) {
linenum++;
if (!parse_prime(linenum, line, &dhg))
continue;
if ((dhg.size > max || dhg.size < min) ||
dhg.size != best ||
bestcount++ != which) {
BN_clear_free(dhg.g);
BN_clear_free(dhg.p);
continue;
}
break;
}
free(line);
line = NULL;
fclose(f);
if (bestcount != which + 1) {
logit("WARNING: selected prime disappeared in %s, giving up",
get_moduli_filename());
return (dh_new_group_fallback(max));
}
return (dh_new_group(dhg.g, dhg.p));
}
/* diffie-hellman-groupN-sha1 */
int
dh_pub_is_valid(const DH *dh, const BIGNUM *dh_pub)
{
int i;
int n = BN_num_bits(dh_pub);
int bits_set = 0;
BIGNUM *tmp;
const BIGNUM *dh_p;
DH_get0_pqg(dh, &dh_p, NULL, NULL);
if (BN_is_negative(dh_pub)) {
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_f("BN_new failed");
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;
const BIGNUM *dh_p, *pub_key;
DH_get0_pqg(dh, &dh_p, NULL, NULL);
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.
*/
if (!DH_set_length(dh, MINIMUM(need * 2, pbits - 1)))
return SSH_ERR_LIBCRYPTO_ERROR;
if (DH_generate_key(dh) == 0)
return SSH_ERR_LIBCRYPTO_ERROR;
DH_get0_key(dh, &pub_key, NULL);
if (!dh_pub_is_valid(dh, pub_key))
return SSH_ERR_INVALID_FORMAT;
return 0;
}
DH *
dh_new_group_asc(const char *gen, const char *modulus)
{
DH *dh;
BIGNUM *dh_p = NULL, *dh_g = NULL;
if ((dh = DH_new()) == NULL)
return NULL;
if (BN_hex2bn(&dh_p, modulus) == 0 ||
BN_hex2bn(&dh_g, gen) == 0)
goto fail;
if (!DH_set0_pqg(dh, dh_p, NULL, dh_g))
goto fail;
return dh;
fail:
DH_free(dh);
BN_clear_free(dh_p);
BN_clear_free(dh_g);
return NULL;
}
/*
* 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;
if (!DH_set0_pqg(dh, modulus, NULL, gen)) {
DH_free(dh);
return NULL;
}
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", *group18 =
"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, group18));
}
/* Select fallback group used by DH-GEX if moduli file cannot be read. */
DH *
dh_new_group_fallback(int max)
{
debug3_f("requested max size %d", 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;
}
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