EVP_PKEY_is_a, EVP_PKEY_can_sign, EVP_PKEY_typenames_do_all, EVP_PKEY_get0_first_alg_name - key type and capabilities functions
#include <openssl/evp.h>
int EVP_PKEY_is_a(const EVP_PKEY *pkey, const char *name);
int EVP_PKEY_can_sign(const EVP_PKEY *pkey);
void EVP_PKEY_typenames_do_all(const EVP_PKEY *pkey,
void (*fn)(const char *name, void *data),
void *data);
const char *EVP_PKEY_get0_first_alg_name(const EVP_PKEY *key);EVP_PKEY_is_a() checks if the key type of pkey is name.
EVP_PKEY_can_sign() checks if the functionality for the key type of pkey supports signing. No other check is done, such as whether pkey contains a private key.
EVP_PKEY_typenames_do_all() traverses all names for pkey's key type, and calls fn with each name and data. For example, an RSA EVP_PKEY may be named both RSA and rsaEncryption. The order of the names is undefined.
EVP_PKEY_get0_first_alg_name() returns the first algorithm name that is found for the given pkey. Note that the pkey may have multiple synonyms associated with it. In this case it is undefined which one will be returned. Ownership of the returned string is retained by the pkey object and should not be freed by the caller.
EVP_PKEY_is_a() returns 1 if pkey has the key type name, otherwise 0.
EVP_PKEY_can_sign() returns 1 if the pkey key type functionality supports signing, otherwise 0.
EVP_PKEY_get0_first_alg_name() returns the name that is found or NULL on error.
The loaded providers and what key types they support will ultimately determine what name is possible to use with EVP_PKEY_is_a(). We do know that the default provider supports RSA, DH, DSA and EC keys, so we can use this as an crude example:
#include <openssl/evp.h>
...
/* |pkey| is an EVP_PKEY* */
if (EVP_PKEY_is_a(pkey, "RSA")) {
BIGNUM *modulus = NULL;
if (EVP_PKEY_get_bn_param(pkey, "n", &modulus))
/* do whatever with the modulus */
BN_free(modulus);
} #include <openssl/evp.h>
...
/* |pkey| is an EVP_PKEY* */
if (!EVP_PKEY_can_sign(pkey)) {
fprintf(stderr, "Not a signing key!");
exit(1);
}
/* Sign something... */The functions described here were added in OpenSSL 3.0.
Copyright 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.