All these parameters (except for ``block-size'') can be set with EVP_MAC_CTX_set_params(). Furthermore, the ``size'' parameter can be retrieved with EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_mac_size(). The length of the ``size'' parameter should not exceed that of a size_t. Likewise, the ``block-size'' parameter can be retrieved with EVP_MAC_CTX_get_params(), or with EVP_MAC_CTX_get_block_size().
The ``custom'' parameter must be set as part of or before the EVP_MAC_init() call. The ``xof'' and ``size'' parameters can be set at any time before EVP_MAC_final(). The ``key'' parameter is set as part of the EVP_MAC_init() call, but can be set before it instead.
#include <openssl/evp.h>
#include <openssl/params.h>
static int do_kmac(const unsigned char *in, size_t in_len,
const unsigned char *key, size_t key_len,
const unsigned char *custom, size_t custom_len,
int xof_enabled, unsigned char *out, int out_len)
{
EVP_MAC_CTX *ctx = NULL;
EVP_MAC *mac = NULL;
OSSL_PARAM params[4], *p;
int ret = 0;
size_t l = 0;
mac = EVP_MAC_fetch(NULL, "KMAC-128", NULL);
if (mac == NULL)
goto err;
ctx = EVP_MAC_CTX_new(mac);
/* The mac can be freed after it is used by EVP_MAC_CTX_new */
EVP_MAC_free(mac);
if (ctx == NULL)
goto err;
/*
* Setup parameters required before calling EVP_MAC_init()
* The parameters OSSL_MAC_PARAM_XOF and OSSL_MAC_PARAM_SIZE may also be
* used at this point.
*/
p = params;
*p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_KEY,
(void *)key, key_len);
if (custom != NULL && custom_len != 0)
*p++ = OSSL_PARAM_construct_octet_string(OSSL_MAC_PARAM_CUSTOM,
(void *)custom, custom_len);
*p = OSSL_PARAM_construct_end();
if (!EVP_MAC_CTX_set_params(ctx, params))
goto err;
if (!EVP_MAC_init(ctx))
goto err;
/*
* Note: the following optional parameters can be set any time
* before EVP_MAC_final().
*/
p = params;
*p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_XOF, &xof_enabled);
*p++ = OSSL_PARAM_construct_int(OSSL_MAC_PARAM_SIZE, &out_len);
*p = OSSL_PARAM_construct_end();
if (!EVP_MAC_CTX_set_params(ctx, params))
goto err;
/* The update may be called multiple times here for streamed input */
if (!EVP_MAC_update(ctx, in, in_len))
goto err;
if (!EVP_MAC_final(ctx, out, &l, out_len))
goto err;
ret = 1;
err:
EVP_MAC_CTX_free(ctx);
return ret;
}
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>.