NAME

       EVP_KEYMGMT, EVP_KEYMGMT_fetch, EVP_KEYMGMT_up_ref, EVP_KEYMGMT_free,
       EVP_KEYMGMT_get0_provider, EVP_KEYMGMT_is_a, EVP_KEYMGMT_get0_description,
       EVP_KEYMGMT_get0_name, EVP_KEYMGMT_do_all_provided, EVP_KEYMGMT_names_do_all,
       EVP_KEYMGMT_gettable_params, EVP_KEYMGMT_settable_params, EVP_KEYMGMT_gen_settable_params
       - EVP key management routines

SYNOPSIS

        #include <openssl/evp.h>

        typedef struct evp_keymgmt_st EVP_KEYMGMT;

        EVP_KEYMGMT *EVP_KEYMGMT_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
                                       const char *properties);
        int EVP_KEYMGMT_up_ref(EVP_KEYMGMT *keymgmt);
        void EVP_KEYMGMT_free(EVP_KEYMGMT *keymgmt);
        const OSSL_PROVIDER *EVP_KEYMGMT_get0_provider(const EVP_KEYMGMT *keymgmt);
        int EVP_KEYMGMT_is_a(const EVP_KEYMGMT *keymgmt, const char *name);
        const char *EVP_KEYMGMT_get0_name(const EVP_KEYMGMT *keymgmt);
        const char *EVP_KEYMGMT_get0_description(const EVP_KEYMGMT *keymgmt);

        void EVP_KEYMGMT_do_all_provided(OSSL_LIB_CTX *libctx,
                                         void (*fn)(EVP_KEYMGMT *keymgmt, void *arg),
                                         void *arg);
        int EVP_KEYMGMT_names_do_all(const EVP_KEYMGMT *keymgmt,
                                     void (*fn)(const char *name, void *data),
                                     void *data);
        const OSSL_PARAM *EVP_KEYMGMT_gettable_params(const EVP_KEYMGMT *keymgmt);
        const OSSL_PARAM *EVP_KEYMGMT_settable_params(const EVP_KEYMGMT *keymgmt);
        const OSSL_PARAM *EVP_KEYMGMT_gen_settable_params(const EVP_KEYMGMT *keymgmt);

DESCRIPTION

       EVP_KEYMGMT is a method object that represents key management implementations for
       different cryptographic algorithms.  This method object provides functionality to have
       providers import key material from the outside, as well as export key material to the
       outside.  Most of the functionality can only be used internally and has no public
       interface, this object is simply passed into other functions when needed.

       EVP_KEYMGMT_fetch() looks for an algorithm within the provider that has been loaded into
       the OSSL_LIB_CTX given by ctx, having the name given by algorithm and the properties given
       by properties.

       EVP_KEYMGMT_up_ref() increments the reference count for the given EVP_KEYMGMT keymgmt.

       EVP_KEYMGMT_free() decrements the reference count for the given EVP_KEYMGMT keymgmt, and
       when the count reaches zero, frees it.

       EVP_KEYMGMT_get0_provider() returns the provider that has this particular implementation.

       EVP_KEYMGMT_is_a() checks if keymgmt is an implementation of an algorithm that's
       identifiable with name.

       EVP_KEYMGMT_get0_name() returns the algorithm name from the provided implementation for
       the given keymgmt. Note that the keymgmt may have multiple synonyms associated with it. In
       this case the first name from the algorithm definition is returned. Ownership of the
       returned string is retained by the keymgmt object and should not be freed by the caller.

       EVP_KEYMGMT_names_do_all() traverses all names for the keymgmt, and calls fn with each
       name and data.

       EVP_KEYMGMT_get0_description() returns a description of the keymgmt, meant for display and
       human consumption.  The description is at the discretion of the keymgmt implementation.

       EVP_KEYMGMT_do_all_provided() traverses all key keymgmt implementations by all activated
       providers in the library context libctx, and for each of the implementations, calls fn
       with the implementation method and data as arguments.

       EVP_KEYMGMT_gettable_params() and EVP_KEYMGMT_settable_params() return a constant
       OSSL_PARAM(3) array that describes the names and types of key parameters that can be
       retrieved or set.  EVP_KEYMGMT_gettable_params() is used by EVP_PKEY_gettable_params(3).

       EVP_KEYMGMT_gen_settable_params() returns a constant OSSL_PARAM(3) array that describes
       the names and types of key generation parameters that can be set via
       EVP_PKEY_CTX_set_params(3).

NOTES

       EVP_KEYMGMT_fetch() may be called implicitly by other fetching functions, using the same
       library context and properties.  Any other API that uses keys will typically do this.

RETURN VALUES

       EVP_KEYMGMT_fetch() returns a pointer to the key management implementation represented by
       an EVP_KEYMGMT object, or NULL on error.

       EVP_KEYMGMT_up_ref() returns 1 on success, or 0 on error.

       EVP_KEYMGMT_names_do_all() returns 1 if the callback was called for all names. A return
       value of 0 means that the callback was not called for any names.

       EVP_KEYMGMT_free() doesn't return any value.

       EVP_KEYMGMT_get0_provider() returns a pointer to a provider object, or NULL on error.

       EVP_KEYMGMT_is_a() returns 1 of keymgmt was identifiable, otherwise 0.

       EVP_KEYMGMT_get0_name() returns the algorithm name, or NULL on error.

       EVP_KEYMGMT_get0_description() returns a pointer to a description, or NULL if there isn't
       one.

       EVP_KEYMGMT_gettable_params(), EVP_KEYMGMT_settable_params() and
       EVP_KEYMGMT_gen_settable_params() return a constant OSSL_PARAM(3) array or NULL on error.

SEE ALSO

       EVP_MD_fetch(3), OSSL_LIB_CTX(3)

HISTORY

       The functions described here were added in OpenSSL 3.0.

COPYRIGHT

       Copyright 2019-2023 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>.