/* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
* All rights reserved.
*
* This package is an SSL implementation written
* by Eric Young (eay@cryptsoft.com).
* The implementation was written so as to conform with Netscapes SSL.
*
* This library is free for commercial and non-commercial use as long as
* the following conditions are aheared to. The following conditions
* apply to all code found in this distribution, be it the RC4, RSA,
* lhash, DES, etc., code; not just the SSL code. The SSL documentation
* included with this distribution is covered by the same copyright terms
* except that the holder is Tim Hudson (tjh@cryptsoft.com).
*
* Copyright remains Eric Young's, and as such any Copyright notices in
* the code are not to be removed.
* If this package is used in a product, Eric Young should be given attribution
* as the author of the parts of the library used.
* This can be in the form of a textual message at program startup or
* in documentation (online or textual) provided with the package.
*
* 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 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* "This product includes cryptographic software written by
* Eric Young (eay@cryptsoft.com)"
* The word 'cryptographic' can be left out if the rouines from the library
* being used are not cryptographic related :-).
* 4. If you include any Windows specific code (or a derivative thereof) from
* the apps directory (application code) you must include an acknowledgement:
* "This product includes software written by Tim Hudson (tjh@cryptsoft.com)"
*
* THIS SOFTWARE IS PROVIDED BY ERIC YOUNG ``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 OR CONTRIBUTORS 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.
*
* The licence and distribution terms for any publically available version or
* derivative of this code cannot be changed. i.e. this code cannot simply be
* copied and put under another distribution licence
* [including the GNU Public Licence.] */
#include <openssl/dh.h>
#include <openssl/bn.h>
int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *out_flags) {
*out_flags = 0;
BN_CTX *ctx = BN_CTX_new();
if (ctx == NULL) {
return 0;
}
BN_CTX_start(ctx);
int ok = 0;
// Check |pub_key| is greater than 1.
BIGNUM *tmp = BN_CTX_get(ctx);
if (tmp == NULL ||
!BN_set_word(tmp, 1)) {
goto err;
}
if (BN_cmp(pub_key, tmp) <= 0) {
*out_flags |= DH_CHECK_PUBKEY_TOO_SMALL;
}
// Check |pub_key| is less than |dh->p| - 1.
if (!BN_copy(tmp, dh->p) ||
!BN_sub_word(tmp, 1)) {
goto err;
}
if (BN_cmp(pub_key, tmp) >= 0) {
*out_flags |= DH_CHECK_PUBKEY_TOO_LARGE;
}
if (dh->q != NULL) {
// Check |pub_key|^|dh->q| is 1 mod |dh->p|. This is necessary for RFC 5114
// groups which are not safe primes but pick a generator on a prime-order
// subgroup of size |dh->q|.
if (!BN_mod_exp_mont(tmp, pub_key, dh->q, dh->p, ctx, NULL)) {
goto err;
}
if (!BN_is_one(tmp)) {
*out_flags |= DH_CHECK_PUBKEY_INVALID;
}
}
ok = 1;
err:
BN_CTX_end(ctx);
BN_CTX_free(ctx);
return ok;
}
int DH_check(const DH *dh, int *out_flags) {
// Check that p is a safe prime and if g is 2, 3 or 5, check that it is a
// suitable generator where:
// for 2, p mod 24 == 11
// for 3, p mod 12 == 5
// for 5, p mod 10 == 3 or 7
// should hold.
int ok = 0, r;
BN_CTX *ctx = NULL;
BN_ULONG l;
BIGNUM *t1 = NULL, *t2 = NULL;
*out_flags = 0;
ctx = BN_CTX_new();
if (ctx == NULL) {
goto err;
}
BN_CTX_start(ctx);
t1 = BN_CTX_get(ctx);
if (t1 == NULL) {
goto err;
}
t2 = BN_CTX_get(ctx);
if (t2 == NULL) {
goto err;
}
if (dh->q) {
if (BN_cmp(dh->g, BN_value_one()) <= 0) {
*out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
} else if (BN_cmp(dh->g, dh->p) >= 0) {
*out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
} else {
// Check g^q == 1 mod p
if (!BN_mod_exp_mont(t1, dh->g, dh->q, dh->p, ctx, NULL)) {
goto err;
}
if (!BN_is_one(t1)) {
*out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
}
}
r = BN_is_prime_ex(dh->q, BN_prime_checks, ctx, NULL);
if (r < 0) {
goto err;
}
if (!r) {
*out_flags |= DH_CHECK_Q_NOT_PRIME;
}
// Check p == 1 mod q i.e. q divides p - 1
if (!BN_div(t1, t2, dh->p, dh->q, ctx)) {
goto err;
}
if (!BN_is_one(t2)) {
*out_flags |= DH_CHECK_INVALID_Q_VALUE;
}
if (dh->j && BN_cmp(dh->j, t1)) {
*out_flags |= DH_CHECK_INVALID_J_VALUE;
}
} else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
l = BN_mod_word(dh->p, 24);
if (l == (BN_ULONG)-1) {
goto err;
}
if (l != 11) {
*out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
}
} else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
l = BN_mod_word(dh->p, 10);
if (l == (BN_ULONG)-1) {
goto err;
}
if (l != 3 && l != 7) {
*out_flags |= DH_CHECK_NOT_SUITABLE_GENERATOR;
}
} else {
*out_flags |= DH_CHECK_UNABLE_TO_CHECK_GENERATOR;
}
r = BN_is_prime_ex(dh->p, BN_prime_checks, ctx, NULL);
if (r < 0) {
goto err;
}
if (!r) {
*out_flags |= DH_CHECK_P_NOT_PRIME;
} else if (!dh->q) {
if (!BN_rshift1(t1, dh->p)) {
goto err;
}
r = BN_is_prime_ex(t1, BN_prime_checks, ctx, NULL);
if (r < 0) {
goto err;
}
if (!r) {
*out_flags |= DH_CHECK_P_NOT_SAFE_PRIME;
}
}
ok = 1;
err:
if (ctx != NULL) {
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ok;
}