mirror of https://github.com/openssl/openssl
138 lines
6.3 KiB
Plaintext
138 lines
6.3 KiB
Plaintext
=pod
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=head1 NAME
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OSSL_LIB_CTX, OSSL_LIB_CTX_new, OSSL_LIB_CTX_new_from_dispatch,
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OSSL_LIB_CTX_new_child, OSSL_LIB_CTX_free, OSSL_LIB_CTX_load_config,
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OSSL_LIB_CTX_get0_global_default, OSSL_LIB_CTX_set0_default
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- OpenSSL library context
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=head1 SYNOPSIS
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#include <openssl/crypto.h>
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typedef struct ossl_lib_ctx_st OSSL_LIB_CTX;
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OSSL_LIB_CTX *OSSL_LIB_CTX_new(void);
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OSSL_LIB_CTX *OSSL_LIB_CTX_new_from_dispatch(const OSSL_CORE_HANDLE *handle,
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const OSSL_DISPATCH *in);
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OSSL_LIB_CTX *OSSL_LIB_CTX_new_child(const OSSL_CORE_HANDLE *handle,
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const OSSL_DISPATCH *in);
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int OSSL_LIB_CTX_load_config(OSSL_LIB_CTX *ctx, const char *config_file);
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void OSSL_LIB_CTX_free(OSSL_LIB_CTX *ctx);
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OSSL_LIB_CTX *OSSL_LIB_CTX_get0_global_default(void);
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OSSL_LIB_CTX *OSSL_LIB_CTX_set0_default(OSSL_LIB_CTX *ctx);
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=head1 DESCRIPTION
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B<OSSL_LIB_CTX> is an internal OpenSSL library context type.
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Applications may allocate their own, but may also use NULL to use
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a default context with functions that take an B<OSSL_LIB_CTX>
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argument.
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When a non default library context is in use care should be taken with
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multi-threaded applications to properly clean up thread local resources before
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the OSSL_LIB_CTX is freed.
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See L<OPENSSL_thread_stop_ex(3)> for more information.
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OSSL_LIB_CTX_new() creates a new OpenSSL library context.
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OSSL_LIB_CTX_new_from_dispatch() creates a new OpenSSL library context
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initialised to use callbacks from the OSSL_DISPATCH structure. This is primarily
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useful for provider authors. The I<handle> and dispatch structure arguments
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passed should be the same ones as passed to a provider's
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OSSL_provider_init function. Some OpenSSL functions, such as
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L<BIO_new_from_core_bio(3)>, require the library context to be created in this
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way in order to work.
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OSSL_LIB_CTX_new_child() is only useful to provider authors and does the same
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thing as OSSL_LIB_CTX_new_from_dispatch() except that it additionally links the
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new library context to the application library context. The new library context
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is a full library context in its own right, but will have all the same providers
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available to it that are available in the application library context (without
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having to reload them). If the application loads or unloads providers from the
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application library context then this will be automatically mirrored in the
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child library context.
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In addition providers that are not loaded in the parent library context can be
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explicitly loaded into the child library context independently from the parent
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library context. Providers loaded independently in this way will not be mirrored
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in the parent library context and will not be affected if the parent library
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context subsequently loads the same provider.
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A provider may call the function L<OSSL_PROVIDER_load(3)> with the child library
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context as required. If the provider already exists due to it being mirrored
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from the parent library context then it will remain available and its reference
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count will be increased. If L<OSSL_PROVIDER_load(3)> is called in this way then
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L<OSSL_PROVIDER_unload(3)> should be subsequently called to decrement the
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reference count. L<OSSL_PROVIDER_unload(3)> must not be called for a provider in
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the child library context that did not have an earlier L<OSSL_PROVIDER_load(3)>
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call for that provider in that child library context.
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In addition to providers, a child library context will also mirror the default
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properties (set via L<EVP_set_default_properties(3)>) from the parent library
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context. If L<EVP_set_default_properties(3)> is called directly on a child
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library context then the new properties will override anything from the parent
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library context and mirroring of the properties will stop.
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When OSSL_LIB_CTX_new_child() is called from within the scope of a provider's
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B<OSSL_provider_init> function the currently initialising provider is not yet
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available in the application's library context and therefore will similarly not
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yet be available in the newly constructed child library context. As soon as the
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B<OSSL_provider_init> function returns then the new provider is available in the
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application's library context and will be similarly mirrored in the child
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library context.
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OSSL_LIB_CTX_load_config() loads a configuration file using the given I<ctx>.
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This can be used to associate a library context with providers that are loaded
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from a configuration. This function must not be called concurrently from
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multiple threads on a single I<ctx>.
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OSSL_LIB_CTX_free() frees the given I<ctx>, unless it happens to be the
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default OpenSSL library context.
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OSSL_LIB_CTX_get0_global_default() returns a concrete (non NULL) reference to
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the global default library context.
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OSSL_LIB_CTX_set0_default() sets the default OpenSSL library context to be
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I<ctx> in the current thread. The previous default library context is
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returned. Care should be taken by the caller to restore the previous
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default library context with a subsequent call of this function. If I<ctx> is
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NULL then no change is made to the default library context, but a pointer to
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the current library context is still returned. On a successful call of this
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function the returned value will always be a concrete (non NULL) library
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context.
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Care should be taken when changing the default library context and starting
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async jobs (see L<ASYNC_start_job(3)>), as the default library context when
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the job is started will be used throughout the lifetime of an async job, no
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matter how the calling thread makes further default library context changes
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in the mean time. This means that the calling thread must not free the
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library context that was the default at the start of the async job before
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that job has finished.
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=head1 RETURN VALUES
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OSSL_LIB_CTX_new(), OSSL_LIB_CTX_get0_global_default() and
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OSSL_LIB_CTX_set0_default() return a library context pointer on success, or NULL
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on error.
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OSSL_LIB_CTX_free() doesn't return any value.
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OSSL_LIB_CTX_load_config() returns 1 on success, 0 on error.
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=head1 HISTORY
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All of the functions described on this page were added in 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
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this file except in compliance with the License. You can obtain a copy
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in the file 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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