NAME

       OSSL_PROVIDER_set_default_search_path, OSSL_PROVIDER, OSSL_PROVIDER_load,
       OSSL_PROVIDER_try_load, OSSL_PROVIDER_unload, OSSL_PROVIDER_available,
       OSSL_PROVIDER_do_all, OSSL_PROVIDER_gettable_params, OSSL_PROVIDER_get_params,
       OSSL_PROVIDER_query_operation, OSSL_PROVIDER_unquery_operation,
       OSSL_PROVIDER_get0_provider_ctx, OSSL_PROVIDER_get0_dispatch, OSSL_PROVIDER_add_builtin,
       OSSL_PROVIDER_get0_name, OSSL_PROVIDER_get_capabilities, OSSL_PROVIDER_self_test -
       provider routines

SYNOPSIS

        #include <openssl/provider.h>

        typedef struct ossl_provider_st OSSL_PROVIDER;

        int OSSL_PROVIDER_set_default_search_path(OSSL_LIB_CTX *libctx,
                                                  const char *path);

        OSSL_PROVIDER *OSSL_PROVIDER_load(OSSL_LIB_CTX *libctx, const char *name);
        OSSL_PROVIDER *OSSL_PROVIDER_try_load(OSSL_LIB_CTX *libctx, const char *name,
                                              int retain_fallbacks);
        int OSSL_PROVIDER_unload(OSSL_PROVIDER *prov);
        int OSSL_PROVIDER_available(OSSL_LIB_CTX *libctx, const char *name);
        int OSSL_PROVIDER_do_all(OSSL_LIB_CTX *ctx,
                                 int (*cb)(OSSL_PROVIDER *provider, void *cbdata),
                                 void *cbdata);

        const OSSL_PARAM *OSSL_PROVIDER_gettable_params(OSSL_PROVIDER *prov);
        int OSSL_PROVIDER_get_params(OSSL_PROVIDER *prov, OSSL_PARAM params[]);

        const OSSL_ALGORITHM *OSSL_PROVIDER_query_operation(const OSSL_PROVIDER *prov,
                                                            int operation_id,
                                                            int *no_cache);
        void OSSL_PROVIDER_unquery_operation(const OSSL_PROVIDER *prov,
                                             int operation_id,
                                             const OSSL_ALGORITHM *algs);
        void *OSSL_PROVIDER_get0_provider_ctx(const OSSL_PROVIDER *prov);
        const OSSL_DISPATCH *OSSL_PROVIDER_get0_dispatch(const OSSL_PROVIDER *prov);

        int OSSL_PROVIDER_add_builtin(OSSL_LIB_CTX *libctx, const char *name,
                                      ossl_provider_init_fn *init_fn);

        const char *OSSL_PROVIDER_get0_name(const OSSL_PROVIDER *prov);

        int OSSL_PROVIDER_get_capabilities(const OSSL_PROVIDER *prov,
                                           const char *capability,
                                           OSSL_CALLBACK *cb,
                                           void *arg);
        int OSSL_PROVIDER_self_test(const OSSL_PROVIDER *prov);

DESCRIPTION

       OSSL_PROVIDER is a type that holds internal information about implementation providers
       (see provider(7) for information on what a provider is).  A provider can be built in to
       the application or the OpenSSL libraries, or can be a loadable module.  The functions
       described here handle both forms.

       Some of these functions operate within a library context, please see OSSL_LIB_CTX(3) for
       further details.

   Functions
       OSSL_PROVIDER_set_default_search_path() specifies the default search path that is to be
       used for looking for providers in the specified libctx.  If left unspecified, an
       environment variable and a fall back default value will be used instead.

       OSSL_PROVIDER_add_builtin() is used to add a built in provider to OSSL_PROVIDER store in
       the given library context, by associating a provider name with a provider initialization
       function.  This name can then be used with OSSL_PROVIDER_load().

       OSSL_PROVIDER_load() loads and initializes a provider.  This may simply initialize a
       provider that was previously added with OSSL_PROVIDER_add_builtin() and run its given
       initialization function, or load a provider module with the given name and run its
       provider entry point, "OSSL_provider_init". The name can be a path to a provider module,
       in that case the provider name as returned by OSSL_PROVIDER_get0_name() will be the path.
       Interpretation of relative paths is platform dependent and they are relative to the
       configured "MODULESDIR" directory or the path set in the environment variable
       OPENSSL_MODULES if set.

       OSSL_PROVIDER_try_load() functions like OSSL_PROVIDER_load(), except that it does not
       disable the fallback providers if the provider cannot be loaded and initialized or if
       retain_fallbacks is nonzero.  If the provider loads successfully and retain_fallbacks is
       zero, the fallback providers are disabled.

       OSSL_PROVIDER_unload() unloads the given provider.  For a provider added with
       OSSL_PROVIDER_add_builtin(), this simply runs its teardown function.

       OSSL_PROVIDER_available() checks if a named provider is available for use.

       OSSL_PROVIDER_do_all() iterates over all loaded providers, calling cb for each one, with
       the current provider in provider and the cbdata that comes from the caller. If no other
       provider has been loaded before calling this function, the default provider is still
       available as fallback.  See OSSL_PROVIDER-default(7) for more information on this fallback
       behaviour.

       OSSL_PROVIDER_gettable_params() is used to get a provider parameter descriptor set as a
       constant OSSL_PARAM(3) array.

       OSSL_PROVIDER_get_params() is used to get provider parameter values.  The caller must
       prepare the OSSL_PARAM(3) array before calling this function, and the variables acting as
       buffers for this parameter array should be filled with data when it returns successfully.

       OSSL_PROVIDER_self_test() is used to run a provider's self tests on demand.  If the self
       tests fail then the provider will fail to provide any further services and algorithms.
       OSSL_SELF_TEST_set_callback(3) may be called beforehand in order to display diagnostics
       for the running self tests.

       OSSL_PROVIDER_query_operation() calls the provider's query_operation function (see
       provider(7)), if the provider has one. It returns an array of OSSL_ALGORITHM for the given
       operation_id terminated by an all NULL OSSL_ALGORITHM entry. This is considered a low-
       level function that most applications should not need to call.

       OSSL_PROVIDER_unquery_operation() calls the provider's unquery_operation function (see
       provider(7)), if the provider has one.  This is considered a low-level function that most
       applications should not need to call.

       OSSL_PROVIDER_get0_provider_ctx() returns the provider context for the given provider. The
       provider context is an opaque handle set by the provider itself and is passed back to the
       provider by libcrypto in various function calls.

       OSSL_PROVIDER_get0_dispatch() returns the provider's dispatch table as it was returned in
       the out parameter from the provider's init function. See provider-base(7).

       If it is permissible to cache references to this array then *no_store is set to 0 or 1
       otherwise. If the array is not cacheable then it is assumed to have a short lifetime.

       OSSL_PROVIDER_get0_name() returns the name of the given provider.

       OSSL_PROVIDER_get_capabilities() provides information about the capabilities supported by
       the provider specified in prov with the capability name capability. For each capability of
       that name supported by the provider it will call the callback cb and supply a set of
       OSSL_PARAM(3)s describing the capability. It will also pass back the argument arg. For
       more details about capabilities and what they can be used for please see "CAPABILTIIES" in
       provider-base(7).

RETURN VALUES

       OSSL_PROVIDER_set_default_search_path(), OSSL_PROVIDER_add(), OSSL_PROVIDER_unload(),
       OSSL_PROVIDER_get_params() and OSSL_PROVIDER_get_capabilities() return 1 on success, or 0
       on error.

       OSSL_PROVIDER_load() and OSSL_PROVIDER_try_load() return a pointer to a provider object on
       success, or NULL on error.

       OSSL_PROVIDER_do_all() returns 1 if the callback cb returns 1 for every provider it is
       called with, or 0 if any provider callback invocation returns 0; callback processing stops
       at the first callback invocation on a provider that returns 0.

       OSSL_PROVIDER_available() returns 1 if the named provider is available, otherwise 0.

       OSSL_PROVIDER_gettable_params() returns a pointer to an array of constant OSSL_PARAM(3),
       or NULL if none is provided.

       OSSL_PROVIDER_get_params() and returns 1 on success, or 0 on error.

       OSSL_PROVIDER_query_operation() returns an array of OSSL_ALGORITHM or NULL on error.

       OSSL_PROVIDER_self_test() returns 1 if the self tests pass, or 0 on error.

EXAMPLES

       This demonstrates how to load the provider module "foo" and ask for its build information.

        #include <openssl/params.h>
        #include <openssl/provider.h>
        #include <openssl/err.h>

        OSSL_PROVIDER *prov = NULL;
        const char *build = NULL;
        OSSL_PARAM request[] = {
            { "buildinfo", OSSL_PARAM_UTF8_PTR, &build, 0, 0 },
            { NULL, 0, NULL, 0, 0 }
        };

        if ((prov = OSSL_PROVIDER_load(NULL, "foo")) != NULL
            && OSSL_PROVIDER_get_params(prov, request))
            printf("Provider 'foo' buildinfo: %s\n", build);
        else
            ERR_print_errors_fp(stderr);

SEE ALSO

       openssl-core.h(7), OSSL_LIB_CTX(3), provider(7)

HISTORY

       The type and functions described here were added in OpenSSL 3.0.

COPYRIGHT

       Copyright 2019-2023 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 <https://www.openssl.org/source/license.html>.