=pod

=head1 NAME

EVP_KEYMGMT,
EVP_KEYMGMT_fetch,
EVP_KEYMGMT_up_ref,
EVP_KEYMGMT_free,
EVP_KEYMGMT_provider,
EVP_KEYMGMT_is_a,
EVP_KEYMGMT_number,
EVP_KEYMGMT_do_all_provided,
EVP_KEYMGMT_names_do_all
- EVP key management routines

=head1 SYNOPSIS

 #include <openssl/evp.h>

 typedef struct evp_keymgmt_st EVP_KEYMGMT;

 EVP_KEYMGMT *EVP_KEYMGMT_fetch(OPENSSL_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_provider(const EVP_KEYMGMT *keymgmt);
 int EVP_KEYMGMT_is_a(const EVP_KEYMGMT *keymgmt, const char *name);
 int EVP_KEYMGMT_number(const EVP_KEYMGMT *keymgmt);
 void EVP_KEYMGMT_do_all_provided(OPENSSL_CTX *libctx,
                                  void (*fn)(EVP_KEYMGMT *keymgmt, void *arg),
                                  void *arg);
 void EVP_KEYMGMT_names_do_all(const EVP_KEYMGMT *keymgmt,
                               void (*fn)(const char *name, void *data),
                               void *data);

=head1 DESCRIPTION

B<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 B<OPENSSL_CTX> given by I<ctx>, having the
name given by I<algorithm> and the properties given by I<properties>.

EVP_KEYMGMT_up_ref() increments the reference count for the given
B<EVP_KEYMGMT> I<keymgmt>.

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

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

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

EVP_KEYMGMT_number() returns the internal dynamic number assigned to
the I<keymgmt>.

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

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

=head1 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.

=head1 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_free() doesn't return any value.

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

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

EVP_KEYMGMT_number() returns an integer.

=head1 SEE ALSO

L<EVP_MD_fetch(3)>, L<OPENSSL_CTX(3)>

=head1 HISTORY

The functions described here were added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019 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
L<https://www.openssl.org/source/license.html>.

=cut