303 lines
8.1 KiB
C
Executable file
303 lines
8.1 KiB
C
Executable file
/* $OpenBSD: dh_check.c,v 1.24 2022/01/10 12:00:52 tb Exp $ */
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/* 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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*/
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#include <stdio.h>
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#include <openssl/bn.h>
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#include <openssl/dh.h>
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#include <openssl/err.h>
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#include "bn_lcl.h"
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#include "dh_local.h"
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#define DH_NUMBER_ITERATIONS_FOR_PRIME 64
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/*
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* Check that p is odd and 1 < g < p - 1. The _ex version removes the need of
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* inspecting flags and pushes errors on the stack instead.
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*/
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int
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DH_check_params_ex(const DH *dh)
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{
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int flags = 0;
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if (!DH_check_params(dh, &flags))
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return 0;
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if ((flags & DH_CHECK_P_NOT_PRIME) != 0)
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DHerror(DH_R_CHECK_P_NOT_PRIME);
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if ((flags & DH_NOT_SUITABLE_GENERATOR) != 0)
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DHerror(DH_R_NOT_SUITABLE_GENERATOR);
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return flags == 0;
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}
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int
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DH_check_params(const DH *dh, int *flags)
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{
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BIGNUM *max_g = NULL;
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int ok = 0;
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*flags = 0;
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if (!BN_is_odd(dh->p))
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*flags |= DH_CHECK_P_NOT_PRIME;
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/*
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* Check that 1 < dh->g < p - 1
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*/
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if (BN_cmp(dh->g, BN_value_one()) <= 0)
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*flags |= DH_NOT_SUITABLE_GENERATOR;
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/* max_g = p - 1 */
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if ((max_g = BN_dup(dh->p)) == NULL)
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goto err;
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if (!BN_sub_word(max_g, 1))
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goto err;
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/* check that g < max_g */
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if (BN_cmp(dh->g, max_g) >= 0)
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*flags |= DH_NOT_SUITABLE_GENERATOR;
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ok = 1;
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err:
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BN_free(max_g);
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return ok;
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}
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/*
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* Check that p is a safe prime and that g is a suitable generator.
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* The _ex version puts errors on the stack instead of returning flags.
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*/
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int
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DH_check_ex(const DH *dh)
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{
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int flags = 0;
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if (!DH_check(dh, &flags))
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return 0;
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if ((flags & DH_NOT_SUITABLE_GENERATOR) != 0)
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DHerror(DH_R_NOT_SUITABLE_GENERATOR);
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if ((flags & DH_CHECK_Q_NOT_PRIME) != 0)
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DHerror(DH_R_CHECK_Q_NOT_PRIME);
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if ((flags & DH_CHECK_INVALID_Q_VALUE) != 0)
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DHerror(DH_R_CHECK_INVALID_Q_VALUE);
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if ((flags & DH_CHECK_INVALID_J_VALUE) != 0)
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DHerror(DH_R_CHECK_INVALID_J_VALUE);
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if ((flags & DH_UNABLE_TO_CHECK_GENERATOR) != 0)
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DHerror(DH_R_UNABLE_TO_CHECK_GENERATOR);
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if ((flags & DH_CHECK_P_NOT_PRIME) != 0)
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DHerror(DH_R_CHECK_P_NOT_PRIME);
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if ((flags & DH_CHECK_P_NOT_SAFE_PRIME) != 0)
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DHerror(DH_R_CHECK_P_NOT_SAFE_PRIME);
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return flags == 0;
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}
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int
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DH_check(const DH *dh, int *flags)
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{
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BN_CTX *ctx = NULL;
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int is_prime;
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int ok = 0;
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*flags = 0;
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if (!DH_check_params(dh, flags))
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goto err;
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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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BN_CTX_start(ctx);
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if (dh->q != NULL) {
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BIGNUM *quotient, *residue;
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if ((quotient = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((residue = BN_CTX_get(ctx)) == NULL)
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goto err;
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if ((*flags & DH_NOT_SUITABLE_GENERATOR) == 0) {
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/* Check g^q == 1 mod p */
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if (!BN_mod_exp_ct(residue, dh->g, dh->q, dh->p, ctx))
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goto err;
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if (!BN_is_one(residue))
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*flags |= DH_NOT_SUITABLE_GENERATOR;
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}
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is_prime = BN_is_prime_ex(dh->q, DH_NUMBER_ITERATIONS_FOR_PRIME,
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ctx, NULL);
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if (is_prime < 0)
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goto err;
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if (is_prime == 0)
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*flags |= DH_CHECK_Q_NOT_PRIME;
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/* Check p == 1 mod q, i.e., q divides p - 1 */
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if (!BN_div_ct(quotient, residue, dh->p, dh->q, ctx))
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goto err;
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if (!BN_is_one(residue))
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*flags |= DH_CHECK_INVALID_Q_VALUE;
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if (dh->j != NULL && BN_cmp(dh->j, quotient) != 0)
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*flags |= DH_CHECK_INVALID_J_VALUE;
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}
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is_prime = BN_is_prime_ex(dh->p, DH_NUMBER_ITERATIONS_FOR_PRIME,
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ctx, NULL);
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if (is_prime < 0)
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goto err;
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if (is_prime == 0)
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*flags |= DH_CHECK_P_NOT_PRIME;
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else if (dh->q == NULL) {
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BIGNUM *q;
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if ((q = BN_CTX_get(ctx)) == NULL)
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goto err;
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if (!BN_rshift1(q, dh->p))
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goto err;
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is_prime = BN_is_prime_ex(q, DH_NUMBER_ITERATIONS_FOR_PRIME,
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ctx, NULL);
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if (is_prime < 0)
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goto err;
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if (is_prime == 0)
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*flags |= DH_CHECK_P_NOT_SAFE_PRIME;
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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
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DH_check_pub_key_ex(const DH *dh, const BIGNUM *pub_key)
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{
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int flags = 0;
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if (!DH_check_pub_key(dh, pub_key, &flags))
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return 0;
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if ((flags & DH_CHECK_PUBKEY_TOO_SMALL) != 0)
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DHerror(DH_R_CHECK_PUBKEY_TOO_SMALL);
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if ((flags & DH_CHECK_PUBKEY_TOO_LARGE) != 0)
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DHerror(DH_R_CHECK_PUBKEY_TOO_LARGE);
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if ((flags & DH_CHECK_PUBKEY_INVALID) != 0)
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DHerror(DH_R_CHECK_PUBKEY_INVALID);
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return flags == 0;
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}
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int
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DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *flags)
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{
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BN_CTX *ctx = NULL;
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BIGNUM *max_pub_key;
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int ok = 0;
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*flags = 0;
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if ((ctx = BN_CTX_new()) == NULL)
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goto err;
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BN_CTX_start(ctx);
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if ((max_pub_key = BN_CTX_get(ctx)) == NULL)
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goto err;
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/*
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* Check that 1 < pub_key < dh->p - 1
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*/
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if (BN_cmp(pub_key, BN_value_one()) <= 0)
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*flags |= DH_CHECK_PUBKEY_TOO_SMALL;
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/* max_pub_key = dh->p - 1 */
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if (BN_copy(max_pub_key, dh->p) == NULL)
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goto err;
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if (!BN_sub_word(max_pub_key, 1))
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goto err;
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if (BN_cmp(pub_key, max_pub_key) >= 0)
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*flags |= DH_CHECK_PUBKEY_TOO_LARGE;
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/*
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* If dh->q is set, check that pub_key^q == 1 mod p
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*/
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if (dh->q != NULL) {
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BIGNUM *residue;
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if ((residue = BN_CTX_get(ctx)) == NULL)
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goto err;
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if (!BN_mod_exp_ct(residue, pub_key, dh->q, dh->p, ctx))
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goto err;
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if (!BN_is_one(residue))
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*flags = DH_CHECK_PUBKEY_INVALID;
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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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