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https://github.com/openssl/openssl.git
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d70a562714
As of 37258dadaa and the corresponding upstream
change, BN_mod_word may fail, like BN_div_word. Handle this properly. Thanks to
Brian Smith for pointing this out. See BoringSSL's
44bedc348d9491e63c7ed1438db100a4b8a830be.
Signed-off-by: Kurt Roeckx <kurt@roeckx.be>
Reviewed-by: Rich Salz <rsalz@openssl.org>
GH: #1251
144 lines
3.7 KiB
C
144 lines
3.7 KiB
C
/*
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* Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the OpenSSL license (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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#include <stdio.h>
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#include "internal/cryptlib.h"
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#include <openssl/bn.h>
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#include "dh_locl.h"
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/*-
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* Check that p is a safe prime and
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* if g is 2, 3 or 5, check that it is a suitable generator
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* 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 DH_check(const DH *dh, int *ret)
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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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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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t2 = BN_CTX_get(ctx);
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if (t2 == NULL)
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goto err;
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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_NOT_SUITABLE_GENERATOR;
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else if (BN_cmp(dh->g, dh->p) >= 0)
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*ret |= DH_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(t1, dh->g, dh->q, dh->p, ctx))
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goto err;
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if (!BN_is_one(t1))
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*ret |= DH_NOT_SUITABLE_GENERATOR;
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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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if (!r)
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*ret |= 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(t1, t2, dh->p, dh->q, ctx))
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goto err;
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if (!BN_is_one(t2))
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*ret |= DH_CHECK_INVALID_Q_VALUE;
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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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} 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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if (l != 11)
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*ret |= DH_NOT_SUITABLE_GENERATOR;
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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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if ((l != 3) && (l != 7))
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*ret |= DH_NOT_SUITABLE_GENERATOR;
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} else
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*ret |= DH_UNABLE_TO_CHECK_GENERATOR;
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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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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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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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if (!r)
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*ret |= 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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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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int DH_check_pub_key(const DH *dh, const BIGNUM *pub_key, int *ret)
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{
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int ok = 0;
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BIGNUM *tmp = NULL;
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BN_CTX *ctx = 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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BN_CTX_start(ctx);
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tmp = BN_CTX_get(ctx);
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if (tmp == NULL || !BN_set_word(tmp, 1))
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goto err;
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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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if (BN_copy(tmp, dh->p) == NULL || !BN_sub_word(tmp, 1))
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goto err;
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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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if (dh->q != NULL) {
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/* Check pub_key^q == 1 mod p */
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if (!BN_mod_exp(tmp, pub_key, dh->q, dh->p, ctx))
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goto err;
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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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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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