a383083194
Fully assume that the method constructors use reference counting. Otherwise, we may leak memory, or loose track and do a double free. Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/8341)
145 lines
4.6 KiB
Text
145 lines
4.6 KiB
Text
=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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/* Create store */
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void *(*alloc_tmp_store)(void);
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/* Remove a store */
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void (*dealloc_tmp_store)(void *store);
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/* Get an already existing method from a store */
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void *(*get)(OPENSSL_CTX *libctx, void *store, const char *propquery,
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void *data);
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/* Store a method in a store */
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int (*put)(OPENSSL_CTX *libctx, void *store, const char *propdef,
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void *method, void *data);
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/* Construct a new method */
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void *(*construct)(const OSSL_DISPATCH *fns, OSSL_PROVIDER *prov,
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void *data);
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/* Destruct a method */
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void (*destruct)(void *method);
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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(OPENSSL_CTX *ctx, int operation_id,
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const char *name, const char *properties,
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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 sub-systems 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 sub-systems
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to define more precisely how the methods are created, stored, etc.
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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 C<operation_id>, an algorithm
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C<name> and a set of C<properties>, and then calling appropriate
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functions given by the sub-system specific method creator through
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C<mcm> and the data in C<mcm_data> (which is passed by
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ossl_method_construct()).
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This function assumes that the sub-system method creator implements
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reference counting and acts accordingly (i.e. it will call the
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sub-system 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 sub-system specific method is to give
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ossl_method_construct a set of functions, all in the
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C<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 alloc_tmp_store()
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Create a temporary method store.
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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 dealloc_tmp_store()
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Remove a temporary store.
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=item get()
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Look up an already existing method from a store.
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The store may be given with C<store>.
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B<NULL> is a valid value and means that a sub-system default store
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must be used.
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This default store should be stored in the library context C<libctx>.
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The method to be looked up should be identified with data from C<data>
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(which is the C<mcm_data> that was passed to ossl_construct_method())
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and the provided property query C<propquery>.
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This function is expected to increment the method's reference count.
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=item put()
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Places the C<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 C<store>.
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B<NULL> is a valid value and means that a sub-system default store
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must be used.
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This default store should be stored in the library context C<libctx>.
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The method should be associated with the given property definition
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C<propdef> and any identification data given through C<data> (which is
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the C<mcm_data> that was passed to ossl_construct_method()).
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This function is expected to increment the C<method>'s reference count.
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=item construct()
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Constructs a sub-system method given a dispatch table C<fns>.
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The associated I<provider object> C<prov> is passed as well, to make
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it possible for the sub-system 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_upref().
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This function is expected to set the method's reference count to 1.
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=item desctruct()
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Decrement the C<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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B<NULL> on error.
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=head1 HISTORY
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This functionality was added to OpenSSL 3.0.0.
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=head1 COPYRIGHT
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Copyright 2019 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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