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/*
* Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the Apache License 2.0 (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
#include "internal/ffc.h"
/*
* See SP800-56Ar3 Section 5.6.2.3.1 : FFC Partial public key validation.
* To only be used with ephemeral FFC public keys generated using the approved
* safe-prime groups. (Checks that the public key is in the range [2, p - 1]
*
* ret contains 0 on success, or error flags (see FFC_ERROR_PUBKEY_TOO_SMALL)
*/
int ossl_ffc_validate_public_key_partial(const FFC_PARAMS *params,
const BIGNUM *pub_key, int *ret)
{
int ok = 0;
BIGNUM *tmp = NULL;
BN_CTX *ctx = NULL;
*ret = 0;
if (params == NULL || pub_key == NULL || params->p == NULL) {
*ret = FFC_ERROR_PASSED_NULL_PARAM;
return 0;
}
ctx = BN_CTX_new_ex(NULL);
if (ctx == NULL)
goto err;
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
/* Step(1): Verify pub_key >= 2 */
if (tmp == NULL
|| !BN_set_word(tmp, 1))
goto err;
if (BN_cmp(pub_key, tmp) <= 0) {
*ret |= FFC_ERROR_PUBKEY_TOO_SMALL;
goto err;
}
/* Step(1): Verify pub_key <= p-2 */
if (BN_copy(tmp, params->p) == NULL
|| !BN_sub_word(tmp, 1))
goto err;
if (BN_cmp(pub_key, tmp) >= 0) {
*ret |= FFC_ERROR_PUBKEY_TOO_LARGE;
goto err;
}
ok = 1;
err:
if (ctx != NULL) {
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ok;
}
/*
* See SP800-56Ar3 Section 5.6.2.3.1 : FFC Full public key validation.
*/
int ossl_ffc_validate_public_key(const FFC_PARAMS *params,
const BIGNUM *pub_key, int *ret)
{
int ok = 0;
BIGNUM *tmp = NULL;
BN_CTX *ctx = NULL;
if (!ossl_ffc_validate_public_key_partial(params, pub_key, ret))
return 0;
if (params->q != NULL) {
ctx = BN_CTX_new_ex(NULL);
if (ctx == NULL)
goto err;
BN_CTX_start(ctx);
tmp = BN_CTX_get(ctx);
/* Check pub_key^q == 1 mod p */
if (tmp == NULL
|| !BN_mod_exp(tmp, pub_key, params->q, params->p, ctx))
goto err;
if (!BN_is_one(tmp)) {
*ret |= FFC_ERROR_PUBKEY_INVALID;
goto err;
}
}
ok = 1;
err:
if (ctx != NULL) {
BN_CTX_end(ctx);
BN_CTX_free(ctx);
}
return ok;
}
/*
* See SP800-56Ar3 Section 5.6.2.1.2: Owner assurance of Private key validity.
* Verifies priv_key is in the range [1..upper-1]. The passed in value of upper
* is normally params->q but can be 2^N for approved safe prime groups.
* Note: This assumes that the domain parameters are valid.
*/
int ossl_ffc_validate_private_key(const BIGNUM *upper, const BIGNUM *priv,
int *ret)
{
int ok = 0;
*ret = 0;
if (priv == NULL || upper == NULL) {
*ret = FFC_ERROR_PASSED_NULL_PARAM;
goto err;
}
if (BN_cmp(priv, BN_value_one()) < 0) {
*ret |= FFC_ERROR_PRIVKEY_TOO_SMALL;
goto err;
}
if (BN_cmp(priv, upper) >= 0) {
*ret |= FFC_ERROR_PRIVKEY_TOO_LARGE;
goto err;
}
ok = 1;
err:
return ok;
}
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