mirror of https://github.com/openssl/openssl.git
159 lines
5.1 KiB
Plaintext
159 lines
5.1 KiB
Plaintext
=pod
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=head1 NAME
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OSSL_METHOD_CONSTRUCT_METHOD, ossl_method_construct
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- generic method constructor
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=head1 SYNOPSIS
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#include "internal/core.h"
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struct ossl_method_construct_method_st {
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/* Get a temporary store */
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void *(*get_tmp_store)(void *data);
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/* Get an already existing method from a store */
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void *(*get)(void *store, const OSSL_PROVIDER *prov, void *data);
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/* Store a method in a store */
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int (*put)(void *store, void *method, const OSSL_PROVIDER *prov,
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const char *name, const char *propdef, void *data);
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/* Construct a new method */
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void *(*construct)(const OSSL_ALGORITHM *algodef, OSSL_PROVIDER *prov,
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void *data);
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/* Destruct a method */
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void (*destruct)(void *method, void *data);
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};
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typedef struct ossl_method_construct_method OSSL_METHOD_CONSTRUCT_METHOD;
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void *ossl_method_construct(OSSL_LIB_CTX *ctx, int operation_id,
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OSSL_PROVIDER *prov, int force_cache,
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OSSL_METHOD_CONSTRUCT_METHOD *mcm, void *mcm_data);
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=head1 DESCRIPTION
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All libcrypto subsystems that want to create their own methods based
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on provider dispatch tables need to do so in exactly the same way.
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ossl_method_construct() does this while leaving it to the subsystems
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to define more precisely how the methods are created, stored, etc.
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It's important to keep in mind that a method is identified by three things:
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=over 4
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=item The operation identity
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=item The name of the algorithm
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=item The properties associated with the algorithm implementation
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=back
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=head2 Functions
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ossl_method_construct() creates a method by asking all available
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providers for a dispatch table given an I<operation_id>, and then
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calling the appropriate functions given by the subsystem specific
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method creator through I<mcm> and the data in I<mcm_data> (which is
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passed by ossl_method_construct()).
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If I<prov> is not NULL, only that provider is considered, which is
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useful in the case a method must be found in that particular
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provider.
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This function assumes that the subsystem method creator implements
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reference counting and acts accordingly (i.e. it will call the
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subsystem destruct() method to decrement the reference count when
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appropriate).
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=head2 Structures
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A central part of constructing a subsystem specific method is to give
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ossl_method_construct a set of functions, all in the
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B<OSSL_METHOD_CONSTRUCT_METHOD> structure, which holds the following
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function pointers:
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=over 4
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=item get_tmp_store()
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Create a temporary method store in the scope of the library context I<ctx>.
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This store is used to temporarily store methods for easier lookup, for
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when the provider doesn't want its dispatch table stored in a longer
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term cache.
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=item get()
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Look up an already existing method from a store by name.
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The store may be given with I<store>.
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NULL is a valid value and means that a subsystem default store
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must be used.
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This default store should be stored in the library context I<libctx>.
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The method to be looked up should be identified with data found in I<data>
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(which is the I<mcm_data> that was passed to ossl_construct_method()).
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In other words, the ossl_method_construct() caller is entirely responsible
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for ensuring the necessary data is made available.
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Optionally, I<prov> may be given as a search criterion, to narrow down the
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search of a method belonging to just one provider.
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This function is expected to increment the resulting method's reference count.
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=item put()
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Places the I<method> created by the construct() function (see below)
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in a store.
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The store may be given with I<store>.
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NULL is a valid value and means that a subsystem default store
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must be used.
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This default store should be stored in the library context I<libctx>.
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The method should be associated with the given provider I<prov>,
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I<name> and property definition I<propdef> as well as any
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identification data given through I<data> (which is the I<mcm_data>
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that was passed to ossl_construct_method()).
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This function is expected to increment the I<method>'s reference count.
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=item construct()
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Constructs a subsystem method for the given I<name> and the given
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dispatch table I<fns>.
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The associated provider object I<prov> is passed as well, to make
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it possible for the subsystem constructor to keep a reference, which
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is recommended.
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If such a reference is kept, the I<provider object> reference counter
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must be incremented, using ossl_provider_up_ref().
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This function is expected to set the method's reference count to 1.
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=item destruct()
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Decrement the I<method>'s reference count, and destruct it when
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the reference count reaches zero.
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=back
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=head1 RETURN VALUES
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ossl_method_construct() returns a constructed method on success, or
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NULL on error.
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=head1 HISTORY
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This functionality was added to OpenSSL 3.0.
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=head1 COPYRIGHT
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Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use this
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file except in compliance with the License. You can obtain a copy in the file
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LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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