=pod

=head1 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_gettable_params,
EVP_KEYMGMT_gen_settable_params
- EVP key management routines

=head1 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);
 const OSSL_PARAM *EVP_KEYMGMT_gen_gettable_params(const EVP_KEYMGMT *keymgmt);

=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<OSSL_LIB_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.
If the argument is NULL, nothing is done.

EVP_KEYMGMT_get0_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_get0_name() returns the algorithm name from the provided
implementation for the given I<keymgmt>. Note that the I<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 I<keymgmt> object and should not be freed by the caller.

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

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

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.

EVP_KEYMGMT_gettable_params() and EVP_KEYMGMT_settable_params() return a
constant L<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 L<EVP_PKEY_gettable_params(3)>.

EVP_KEYMGMT_gen_gettable_params() and EVP_KEYMGMT_gen_settable_params() return a
constant L<OSSL_PARAM(3)> array that describes the names and types of key
generation parameters that can be retrieved or set via
L<EVP_PKEY_CTX_get_params(3)> or L<EVP_PKEY_CTX_set_params(3)> respectively.

=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_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 I<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(),
EVP_KEYMGMT_gen_gettable_params() and EVP_KEYMGMT_gen_settable_params()
return a constant L<OSSL_PARAM(3)> array or NULL on error.

=head1 SEE ALSO

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

=head1 HISTORY

The function EVP_KEYMGMT_gen_gettable_params() was added in OpenSSL 3.4.0
All other functions described here were added in OpenSSL 3.0.

=head1 COPYRIGHT

Copyright 2019-2024 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