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EVP_PKEY_gettable_params(3) OpenSSL EVP_PKEY_gettable_params(3)
NAME
EVP_PKEY_gettable_params, EVP_PKEY_get_params, EVP_PKEY_get_int_param,
EVP_PKEY_get_size_t_param, EVP_PKEY_get_bn_param,
EVP_PKEY_get_utf8_string_param, EVP_PKEY_get_octet_string_param -
retrieve key parameters from a key
LIBRARY
libcrypto, -lcrypto
SYNOPSIS
#include <openssl/evp.h>
const OSSL_PARAM *EVP_PKEY_gettable_params(EVP_PKEY *pkey);
int EVP_PKEY_get_params(const EVP_PKEY *pkey, OSSL_PARAM params[]);
int EVP_PKEY_get_int_param(const EVP_PKEY *pkey, const char *key_name,
int *out);
int EVP_PKEY_get_size_t_param(const EVP_PKEY *pkey, const char *key_name,
size_t *out);
int EVP_PKEY_get_bn_param(const EVP_PKEY *pkey, const char *key_name,
BIGNUM **bn);
int EVP_PKEY_get_utf8_string_param(const EVP_PKEY *pkey, const char *key_name,
char *str, size_t max_buf_sz,
size_t *out_len);
int EVP_PKEY_get_octet_string_param(const EVP_PKEY *pkey, const char *key_name,
unsigned char *buf, size_t max_buf_sz,
size_t *out_len);
DESCRIPTION
See OSSL_PARAM(3) for information about parameters.
EVP_PKEY_get_params() retrieves parameters from the key pkey, according
to the contents of params.
EVP_PKEY_gettable_params() returns a constant list of params indicating
the names and types of key parameters that can be retrieved.
An OSSL_PARAM(3) of type OSSL_PARAM_INTEGER or
OSSL_PARAM_UNSIGNED_INTEGER is of arbitrary length. Such a parameter
can be obtained using any of the functions EVP_PKEY_get_int_param(),
EVP_PKEY_get_size_t_param() or EVP_PKEY_get_bn_param(). Attempting to
obtain an integer value that does not fit into a native C int type will
cause EVP_PKEY_get_int_param() to fail. Similarly attempting to obtain
an integer value that is negative or does not fit into a native C
size_t type using EVP_PKEY_get_size_t_param() will also fail.
EVP_PKEY_get_int_param() retrieves a key pkey integer value *out
associated with a name of key_name if it fits into "int" type. For
parameters that do not fit into "int" use EVP_PKEY_get_bn_param().
EVP_PKEY_get_size_t_param() retrieves a key pkey size_t value *out
associated with a name of key_name if it fits into "size_t" type. For
parameters that do not fit into "size_t" use EVP_PKEY_get_bn_param().
EVP_PKEY_get_bn_param() retrieves a key pkey BIGNUM value **bn
associated with a name of key_name. If *bn is NULL then the BIGNUM is
allocated by the method.
EVP_PKEY_get_utf8_string_param() get a key pkey UTF8 string value into
a buffer str of maximum size max_buf_sz associated with a name of
key_name. The maximum size must be large enough to accommodate the
string value including a terminating NUL byte, or this function will
fail. If out_len is not NULL, *out_len is set to the length of the
string not including the terminating NUL byte. The required buffer size
not including the terminating NUL byte can be obtained from *out_len by
calling the function with str set to NULL.
EVP_PKEY_get_octet_string_param() get a key pkey's octet string value
into a buffer buf of maximum size max_buf_sz associated with a name of
key_name. If out_len is not NULL, *out_len is set to the length of the
contents. The required buffer size can be obtained from *out_len by
calling the function with buf set to NULL.
NOTES
These functions only work for EVP_PKEYs that contain a provider side
key.
RETURN VALUES
EVP_PKEY_gettable_params() returns NULL on error or if it is not
supported.
All other methods return 1 if a value associated with the key's
key_name was successfully returned, or 0 if there was an error. An
error may be returned by methods EVP_PKEY_get_utf8_string_param() and
EVP_PKEY_get_octet_string_param() if max_buf_sz is not big enough to
hold the value. If out_len is not NULL, *out_len will be assigned the
required buffer size to hold the value.
EXAMPLES
#include <openssl/evp.h>
char curve_name[64];
unsigned char pub[256];
BIGNUM *bn_priv = NULL;
/*
* NB: assumes 'key' is set up before the next step. In this example the key
* is an EC key.
*/
if (!EVP_PKEY_get_utf8_string_param(key, OSSL_PKEY_PARAM_GROUP_NAME,
curve_name, sizeof(curve_name), &len)) {
/* Error */
}
if (!EVP_PKEY_get_octet_string_param(key, OSSL_PKEY_PARAM_PUB_KEY,
pub, sizeof(pub), &len)) {
/* Error */
}
if (!EVP_PKEY_get_bn_param(key, OSSL_PKEY_PARAM_PRIV_KEY, &bn_priv)) {
/* Error */
}
BN_clear_free(bn_priv);
SEE ALSO
EVP_PKEY_CTX_new(3), provider-keymgmt(7), OSSL_PARAM(3)
HISTORY
These functions were added in OpenSSL 3.0.
COPYRIGHT
Copyright 2020-2023 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>.
3.0.12 2023-10-25 EVP_PKEY_gettable_params(3)