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=head1 NAME

evp_keymgmt_util_export,
evp_keymgmt_util_export_to_provider,
evp_keymgmt_util_find_operation_cache_index,
evp_keymgmt_util_clear_operation_cache,
evp_keymgmt_util_cache_keydata,
evp_keymgmt_util_cache_keyinfo,
evp_keymgmt_util_fromdata
- internal KEYMGMT utility functions

=head1 SYNOPSIS

 #include "crypto/evp.h"

 int evp_keymgmt_util_export(const EVP_PKEY *pk, int selection,
                             OSSL_CALLBACK *export_cb, void *export_cbarg);
 void *evp_keymgmt_util_export_to_provider(EVP_PKEY *pk, EVP_KEYMGMT *keymgmt);
 size_t evp_keymgmt_util_find_operation_cache_index(EVP_PKEY *pk,
                                                    EVP_KEYMGMT *keymgmt);
 void evp_keymgmt_util_clear_operation_cache(EVP_PKEY *pk);
 void evp_keymgmt_util_cache_keydata(EVP_PKEY *pk, size_t index,
                                     EVP_KEYMGMT *keymgmt, void *keydata);
 void evp_keymgmt_util_cache_keyinfo(EVP_PKEY *pk);
 void *evp_keymgmt_util_fromdata(EVP_PKEY *target, EVP_KEYMGMT *keymgmt,
                                 int selection, const OSSL_PARAM params[]);

=head1 DESCRIPTION

evp_keymgmt_util_export() calls L<evp_keymgmt_export(3)> with the
I<keymgmt> and I<keydata> from I<pk>.  This is a convenience function.

evp_keymgmt_util_export_to_provider() exports cached key material
(provider side key material) from the given key I<pk> to a provider
via a B<EVP_KEYMGMT> interface, if this hasn't already been done.
It maintains a cache of provider key references in I<pk> to keep track
of all provider side keys.

To export a legacy key, use L<evp_pkey_export_to_provider(3)> instead,
as this function ignores any legacy key data.

evp_keymgmt_util_find_operation_cache_index() finds the location if
I<keymgmt> in I<pk>'s cache of provided keys for operations.  If
I<keymgmt> is NULL or couldn't be found in the cache, it finds the
first empty slot instead if there is any.

evp_keymgmt_util_clear_operation_cache() can be used to explicitly
clear the cache of operation key references.

evp_keymgmt_util_cache_keydata() can be used to assign a provider key
object to a specific cache slot in the given I<target>.
I<Use extreme care>.

evp_keymgmt_util_cache_keyinfo() can be used to get all kinds of
information from the provvider "origin" and save it in I<pk>'s
information cache.

evp_keymgmt_util_fromdata() can be used to add key object data to a
given key I<target> via a B<EVP_KEYMGMT> interface.  This is used as a
helper for L<EVP_PKEY_fromdata(3)>.

=head1 RETURN VALUES

evp_keymgmt_export_to_provider() and evp_keymgmt_util_fromdata()
return a pointer to the appropriate provider side key (created or
found again), or NULL on error.

evp_keymgmt_util_find_operation_cache_index() returns the index of the
operation cache slot.  If I<keymgmt> is NULL, or if there is no slot
with a match for I<keymgmt>, the index of the first empty slot is
returned, or the maximum number of slots if there isn't an empty one.

=head1 NOTES

"Legacy key" is the term used for any key that has been assigned to an
B<EVP_PKEY> with EVP_PKEY_assign_RSA() and similar functions.

=head1 SEE ALSO

L<EVP_PKEY_ASN1_METHOD(3)>, L<EVP_PKEY_assign_RSA(3)>

=head1 COPYRIGHT

Copyright 2019-2020 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
L<https://www.openssl.org/source/license.html>.

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