591f251bf3
Within the library, we never need to exponentiate modulo an even number.
In fact, all the remaining BN_mod_exp calls are modulo an odd prime.
This extends 617804adc5 to the rest of the
library.
Change-Id: I4273439faa6a516c99673b28f8ae38ddfff7e42d
Reviewed-on: https://boringssl-review.googlesource.com/14024
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
219 lines
6.5 KiB
C
219 lines
6.5 KiB
C
/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
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* All rights reserved.
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*
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* This package is an SSL implementation written
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* by Eric Young (eay@cryptsoft.com).
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* The implementation was written so as to conform with Netscapes SSL.
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*
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* This library is free for commercial and non-commercial use as long as
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* the following conditions are aheared to. The following conditions
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* apply to all code found in this distribution, be it the RC4, RSA,
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* lhash, DES, etc., code; not just the SSL code. The SSL documentation
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* included with this distribution is covered by the same copyright terms
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* except that the holder is Tim Hudson (tjh@cryptsoft.com).
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*
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* Copyright remains Eric Young's, and as such any Copyright notices in
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* the code are not to be removed.
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* If this package is used in a product, Eric Young should be given attribution
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* as the author of the parts of the library used.
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* This can be in the form of a textual message at program startup or
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* in documentation (online or textual) provided with the package.
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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 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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* "This product includes cryptographic software written by
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* Eric Young (eay@cryptsoft.com)"
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* The word 'cryptographic' can be left out if the rouines from the library
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* being used are not cryptographic related :-).
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* 4. If you include any Windows specific code (or a derivative thereof) from
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* the apps directory (application code) you must include an acknowledgement:
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* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
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*
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* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* The licence and distribution terms for any publically available version or
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* derivative of this code cannot be changed. i.e. this code cannot simply be
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* copied and put under another distribution licence
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* [including the GNU Public Licence.] */
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#include <openssl/dh.h>
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#include <openssl/bn.h>
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int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret) {
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*ret = 0;
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BN_CTX *ctx = BN_CTX_new();
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if (ctx == NULL) {
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return 0;
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}
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BN_CTX_start(ctx);
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int ok = 0;
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/* Check |pub_key| is greater than 1. */
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BIGNUM *tmp = BN_CTX_get(ctx);
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if (tmp == NULL ||
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!BN_set_word(tmp, 1)) {
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goto err;
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}
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if (BN_cmp(pub_key, tmp) <= 0) {
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*ret |= DH_CHECK_PUBKEY_TOO_SMALL;
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}
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/* Check |pub_key| is less than |dh->p| - 1. */
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if (!BN_copy(tmp, dh->p) ||
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!BN_sub_word(tmp, 1)) {
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goto err;
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}
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if (BN_cmp(pub_key, tmp) >= 0) {
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*ret |= DH_CHECK_PUBKEY_TOO_LARGE;
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}
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if (dh->q != NULL) {
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/* Check |pub_key|^|dh->q| is 1 mod |dh->p|. This is necessary for RFC 5114
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* groups which are not safe primes but pick a generator on a prime-order
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* subgroup of size |dh->q|. */
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if (!BN_mod_exp_mont(tmp, pub_key, dh->q, dh->p, ctx, NULL)) {
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goto err;
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}
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if (!BN_is_one(tmp)) {
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*ret |= DH_CHECK_PUBKEY_INVALID;
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}
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}
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ok = 1;
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err:
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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return ok;
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}
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int DH_check(const DH *dh, int *ret) {
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/* Check that p is a safe prime and if g is 2, 3 or 5, check that it is a
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* suitable generator where:
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* for 2, p mod 24 == 11
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* for 3, p mod 12 == 5
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* for 5, p mod 10 == 3 or 7
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* should hold.
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*/
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int ok = 0, r;
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BN_CTX *ctx = NULL;
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BN_ULONG l;
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BIGNUM *t1 = NULL, *t2 = NULL;
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*ret = 0;
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ctx = BN_CTX_new();
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if (ctx == NULL) {
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goto err;
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}
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BN_CTX_start(ctx);
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t1 = BN_CTX_get(ctx);
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if (t1 == NULL) {
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goto err;
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}
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t2 = BN_CTX_get(ctx);
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if (t2 == NULL) {
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goto err;
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}
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if (dh->q) {
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if (BN_cmp(dh->g, BN_value_one()) <= 0) {
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*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
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} else if (BN_cmp(dh->g, dh->p) >= 0) {
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*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
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} else {
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/* Check g^q == 1 mod p */
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if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) {
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goto err;
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}
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if (!BN_is_one(t1)) {
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*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
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}
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}
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r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
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if (r < 0) {
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goto err;
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}
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if (!r) {
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*ret |= DH_CHECK_Q_NOT_PRIME;
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}
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/* Check p == 1 mod q i.e. q divides p - 1 */
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if (!BN_div(t1, t2, dh->p, dh->q, ctx)) {
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goto err;
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}
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if (!BN_is_one(t2)) {
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*ret |= DH_CHECK_INVALID_Q_VALUE;
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}
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if (dh->j && BN_cmp(dh->j, t1)) {
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*ret |= DH_CHECK_INVALID_J_VALUE;
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}
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} else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
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l = BN_mod_word(dh->p, 24);
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if (l == (BN_ULONG)-1) {
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goto err;
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}
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if (l != 11) {
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*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
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}
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} else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
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l = BN_mod_word(dh->p, 10);
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if (l == (BN_ULONG)-1) {
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goto err;
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}
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if (l != 3 && l != 7) {
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*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
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}
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} else {
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*ret |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR;
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}
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r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
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if (r < 0) {
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goto err;
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}
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if (!r) {
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*ret |= DH_CHECK_P_NOT_PRIME;
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} else if (!dh->q) {
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if (!BN_rshift1(t1, dh->p)) {
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goto err;
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}
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r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
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if (r < 0) {
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goto err;
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}
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if (!r) {
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*ret |= DH_CHECK_P_NOT_SAFE_PRIME;
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}
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}
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ok = 1;
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err:
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if (ctx != NULL) {
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BN_CTX_end(ctx);
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BN_CTX_free(ctx);
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}
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return ok;
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}
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