oracular (7) provider-base.7ssl.gz

Provided by: openssl_3.3.1-2ubuntu2.1_amd64 bug

NAME

       provider-base - The basic OpenSSL library <-> provider functions

SYNOPSIS

        #include <openssl/core_dispatch.h>

        /*
         * None of these are actual functions, but are displayed like this for
         * the function signatures for functions that are offered as function
         * pointers in OSSL_DISPATCH arrays.
         */

        /* Functions offered by libcrypto to the providers */
        const OSSL_ITEM *core_gettable_params(const OSSL_CORE_HANDLE *handle);
        int core_get_params(const OSSL_CORE_HANDLE *handle, OSSL_PARAM params[]);

        typedef void (*OSSL_thread_stop_handler_fn)(void *arg);
        int core_thread_start(const OSSL_CORE_HANDLE *handle,
                              OSSL_thread_stop_handler_fn handfn,
                              void *arg);

        OPENSSL_CORE_CTX *core_get_libctx(const OSSL_CORE_HANDLE *handle);
        void core_new_error(const OSSL_CORE_HANDLE *handle);
        void core_set_error_debug(const OSSL_CORE_HANDLE *handle,
                                  const char *file, int line, const char *func);
        void core_vset_error(const OSSL_CORE_HANDLE *handle,
                             uint32_t reason, const char *fmt, va_list args);

        int core_obj_add_sigid(const OSSL_CORE_HANDLE *prov, const char  *sign_name,
                               const char *digest_name, const char *pkey_name);
        int core_obj_create(const OSSL_CORE_HANDLE *handle, const char *oid,
                            const char *sn, const char *ln);

        /*
         * Some OpenSSL functionality is directly offered to providers via
         * dispatch
         */
        void *CRYPTO_malloc(size_t num, const char *file, int line);
        void *CRYPTO_zalloc(size_t num, const char *file, int line);
        void CRYPTO_free(void *ptr, const char *file, int line);
        void CRYPTO_clear_free(void *ptr, size_t num,
                               const char *file, int line);
        void *CRYPTO_realloc(void *addr, size_t num,
                             const char *file, int line);
        void *CRYPTO_clear_realloc(void *addr, size_t old_num, size_t num,
                                   const char *file, int line);
        void *CRYPTO_secure_malloc(size_t num, const char *file, int line);
        void *CRYPTO_secure_zalloc(size_t num, const char *file, int line);
        void CRYPTO_secure_free(void *ptr, const char *file, int line);
        void CRYPTO_secure_clear_free(void *ptr, size_t num,
                                      const char *file, int line);
        int CRYPTO_secure_allocated(const void *ptr);
        void OPENSSL_cleanse(void *ptr, size_t len);

        unsigned char *OPENSSL_hexstr2buf(const char *str, long *buflen);

        OSSL_CORE_BIO *BIO_new_file(const char *filename, const char *mode);
        OSSL_CORE_BIO *BIO_new_membuf(const void *buf, int len);
        int BIO_read_ex(OSSL_CORE_BIO *bio, void *data, size_t data_len,
                        size_t *bytes_read);
        int BIO_write_ex(OSSL_CORE_BIO *bio, const void *data, size_t data_len,
                         size_t *written);
        int BIO_up_ref(OSSL_CORE_BIO *bio);
        int BIO_free(OSSL_CORE_BIO *bio);
        int BIO_vprintf(OSSL_CORE_BIO *bio, const char *format, va_list args);
        int BIO_vsnprintf(char *buf, size_t n, const char *fmt, va_list args);

        void OSSL_SELF_TEST_set_callback(OSSL_LIB_CTX *libctx, OSSL_CALLBACK *cb,
                                         void *cbarg);

        size_t get_entropy(const OSSL_CORE_HANDLE *handle,
                           unsigned char **pout, int entropy,
                           size_t min_len, size_t max_len);
        size_t get_user_entropy(const OSSL_CORE_HANDLE *handle,
                                unsigned char **pout, int entropy,
                                size_t min_len, size_t max_len);
        void cleanup_entropy(const OSSL_CORE_HANDLE *handle,
                             unsigned char *buf, size_t len);
        void cleanup_user_entropy(const OSSL_CORE_HANDLE *handle,
                                  unsigned char *buf, size_t len);
        size_t get_nonce(const OSSL_CORE_HANDLE *handle,
                         unsigned char **pout, size_t min_len, size_t max_len,
                         const void *salt, size_t salt_len);
        size_t get_user_nonce(const OSSL_CORE_HANDLE *handle,
                              unsigned char **pout, size_t min_len, size_t max_len,
                              const void *salt, size_t salt_len);
        void cleanup_nonce(const OSSL_CORE_HANDLE *handle,
                           unsigned char *buf, size_t len);
        void cleanup_user_nonce(const OSSL_CORE_HANDLE *handle,
                                unsigned char *buf, size_t len);

        /* Functions for querying the providers in the application library context */
        int provider_register_child_cb(const OSSL_CORE_HANDLE *handle,
                            int (*create_cb)(const OSSL_CORE_HANDLE *provider,
                                             void *cbdata),
                            int (*remove_cb)(const OSSL_CORE_HANDLE *provider,
                                             void *cbdata),
                            int (*global_props_cb)(const char *props, void *cbdata),
                            void *cbdata);
        void provider_deregister_child_cb(const OSSL_CORE_HANDLE *handle);
        const char *provider_name(const OSSL_CORE_HANDLE *prov);
        void *provider_get0_provider_ctx(const OSSL_CORE_HANDLE *prov);
        const OSSL_DISPATCH *provider_get0_dispatch(const OSSL_CORE_HANDLE *prov);
        int provider_up_ref(const OSSL_CORE_HANDLE *prov, int activate);
        int provider_free(const OSSL_CORE_HANDLE *prov, int deactivate);

        /* Functions offered by the provider to libcrypto */
        void provider_teardown(void *provctx);
        const OSSL_ITEM *provider_gettable_params(void *provctx);
        int provider_get_params(void *provctx, OSSL_PARAM params[]);
        const OSSL_ALGORITHM *provider_query_operation(void *provctx,
                                                       int operation_id,
                                                       const int *no_store);
        void provider_unquery_operation(void *provctx, int operation_id,
                                        const OSSL_ALGORITHM *algs);
        const OSSL_ITEM *provider_get_reason_strings(void *provctx);
        int provider_get_capabilities(void *provctx, const char *capability,
                                      OSSL_CALLBACK *cb, void *arg);
        int provider_self_test(void *provctx);

DESCRIPTION

       All "functions" mentioned here are passed as function pointers between libcrypto and the provider in
       OSSL_DISPATCH(3) arrays, in the call of the provider initialization function.  See "Provider" in
       provider(7) for a description of the initialization function. They are known as "upcalls".

       All these "functions" have a corresponding function type definition named OSSL_FUNC_{name}_fn, and a
       helper function to retrieve the function pointer from a OSSL_DISPATCH(3) element named OSSL_FUNC_{name}.
       For example, the "function" core_gettable_params() has these:

        typedef OSSL_PARAM *
            (OSSL_FUNC_core_gettable_params_fn)(const OSSL_CORE_HANDLE *handle);
        static ossl_inline OSSL_NAME_core_gettable_params_fn
            OSSL_FUNC_core_gettable_params(const OSSL_DISPATCH *opf);

       OSSL_DISPATCH(3) arrays are indexed by numbers that are provided as macros in openssl-core_dispatch.h(7),
       as follows:

       For in (the OSSL_DISPATCH(3) array passed from libcrypto to the provider):

        core_gettable_params           OSSL_FUNC_CORE_GETTABLE_PARAMS
        core_get_params                OSSL_FUNC_CORE_GET_PARAMS
        core_thread_start              OSSL_FUNC_CORE_THREAD_START
        core_get_libctx                OSSL_FUNC_CORE_GET_LIBCTX
        core_new_error                 OSSL_FUNC_CORE_NEW_ERROR
        core_set_error_debug           OSSL_FUNC_CORE_SET_ERROR_DEBUG
        core_vset_error                OSSL_FUNC_CORE_VSET_ERROR
        core_obj_add_sigid             OSSL_FUNC_CORE_OBJ_ADD_SIGID
        core_obj_create                OSSL_FUNC_CORE_OBJ_CREATE
        CRYPTO_malloc                  OSSL_FUNC_CRYPTO_MALLOC
        CRYPTO_zalloc                  OSSL_FUNC_CRYPTO_ZALLOC
        CRYPTO_free                    OSSL_FUNC_CRYPTO_FREE
        CRYPTO_clear_free              OSSL_FUNC_CRYPTO_CLEAR_FREE
        CRYPTO_realloc                 OSSL_FUNC_CRYPTO_REALLOC
        CRYPTO_clear_realloc           OSSL_FUNC_CRYPTO_CLEAR_REALLOC
        CRYPTO_secure_malloc           OSSL_FUNC_CRYPTO_SECURE_MALLOC
        CRYPTO_secure_zalloc           OSSL_FUNC_CRYPTO_SECURE_ZALLOC
        CRYPTO_secure_free             OSSL_FUNC_CRYPTO_SECURE_FREE
        CRYPTO_secure_clear_free       OSSL_FUNC_CRYPTO_SECURE_CLEAR_FREE
        CRYPTO_secure_allocated        OSSL_FUNC_CRYPTO_SECURE_ALLOCATED
        BIO_new_file                   OSSL_FUNC_BIO_NEW_FILE
        BIO_new_mem_buf                OSSL_FUNC_BIO_NEW_MEMBUF
        BIO_read_ex                    OSSL_FUNC_BIO_READ_EX
        BIO_write_ex                   OSSL_FUNC_BIO_WRITE_EX
        BIO_up_ref                     OSSL_FUNC_BIO_UP_REF
        BIO_free                       OSSL_FUNC_BIO_FREE
        BIO_vprintf                    OSSL_FUNC_BIO_VPRINTF
        BIO_vsnprintf                  OSSL_FUNC_BIO_VSNPRINTF
        BIO_puts                       OSSL_FUNC_BIO_PUTS
        BIO_gets                       OSSL_FUNC_BIO_GETS
        BIO_ctrl                       OSSL_FUNC_BIO_CTRL
        OPENSSL_cleanse                OSSL_FUNC_OPENSSL_CLEANSE
        OSSL_SELF_TEST_set_callback    OSSL_FUNC_SELF_TEST_CB
        ossl_rand_get_entropy          OSSL_FUNC_GET_ENTROPY
        ossl_rand_get_user_entropy     OSSL_FUNC_GET_USER_ENTROPY
        ossl_rand_cleanup_entropy      OSSL_FUNC_CLEANUP_ENTROPY
        ossl_rand_cleanup_user_entropy OSSL_FUNC_CLEANUP_USER_ENTROPY
        ossl_rand_get_nonce            OSSL_FUNC_GET_NONCE
        ossl_rand_get_user_nonce       OSSL_FUNC_GET_USER_NONCE
        ossl_rand_cleanup_nonce        OSSL_FUNC_CLEANUP_NONCE
        ossl_rand_cleanup_user_nonce   OSSL_FUNC_CLEANUP_USER_NONCE
        provider_register_child_cb     OSSL_FUNC_PROVIDER_REGISTER_CHILD_CB
        provider_deregister_child_cb   OSSL_FUNC_PROVIDER_DEREGISTER_CHILD_CB
        provider_name                  OSSL_FUNC_PROVIDER_NAME
        provider_get0_provider_ctx     OSSL_FUNC_PROVIDER_GET0_PROVIDER_CTX
        provider_get0_dispatch         OSSL_FUNC_PROVIDER_GET0_DISPATCH
        provider_up_ref                OSSL_FUNC_PROVIDER_UP_REF
        provider_free                  OSSL_FUNC_PROVIDER_FREE

       For *out (the OSSL_DISPATCH(3) array passed from the provider to libcrypto):

        provider_teardown              OSSL_FUNC_PROVIDER_TEARDOWN
        provider_gettable_params       OSSL_FUNC_PROVIDER_GETTABLE_PARAMS
        provider_get_params            OSSL_FUNC_PROVIDER_GET_PARAMS
        provider_query_operation       OSSL_FUNC_PROVIDER_QUERY_OPERATION
        provider_unquery_operation     OSSL_FUNC_PROVIDER_UNQUERY_OPERATION
        provider_get_reason_strings    OSSL_FUNC_PROVIDER_GET_REASON_STRINGS
        provider_get_capabilities      OSSL_FUNC_PROVIDER_GET_CAPABILITIES
        provider_self_test             OSSL_FUNC_PROVIDER_SELF_TEST

   Core functions
       core_gettable_params() returns a constant array of descriptor OSSL_PARAM(3), for parameters that
       core_get_params() can handle.

       core_get_params() retrieves parameters from the core for the given handle.  See "Core parameters" below
       for a description of currently known parameters.

       The core_thread_start() function informs the core that the provider has stated an interest in the current
       thread. The core will inform the provider when the thread eventually stops. It must be passed the handle
       for this provider, as well as a callback handfn which will be called when the thread stops. The callback
       will subsequently be called, with the supplied argument arg, from the thread that is stopping and gets
       passed the provider context as an argument. This may be useful to perform thread specific clean up such
       as freeing thread local variables.

       core_get_libctx() retrieves the core context in which the library object for the current provider is
       stored, accessible through the handle.  This function is useful only for built-in providers such as the
       default provider. Never cast this to OSSL_LIB_CTX in a provider that is not built-in as the OSSL_LIB_CTX
       of the library loading the provider might be a completely different structure than the OSSL_LIB_CTX of
       the library the provider is linked to. Use  OSSL_LIB_CTX_new_child(3) instead to obtain a proper library
       context that is linked to the application library context.

       core_new_error(), core_set_error_debug() and core_vset_error() are building blocks for reporting an error
       back to the core, with reference to the handle.

       core_new_error()
           allocates a new thread specific error record.

           This corresponds to the OpenSSL function ERR_new(3).

       core_set_error_debug()
           sets debugging information in the current thread specific error record.  The debugging information
           includes the name of the file file, the line line and the function name func where the error
           occurred.

           This corresponds to the OpenSSL function ERR_set_debug(3).

       core_vset_error()
           sets the reason for the error, along with any addition data.  The reason is a number defined by the
           provider and used to index the reason strings table that's returned by provider_get_reason_strings().
           The additional data is given as a format string fmt and a set of arguments args, which are treated in
           the same manner as with BIO_vsnprintf().  file and line may also be passed to indicate exactly where
           the error occurred or was reported.

           This corresponds to the OpenSSL function ERR_vset_error(3).

       The core_obj_create() function registers a new OID and associated short name sn and long name ln for the
       given handle. It is similar to the OpenSSL function OBJ_create(3) except that it returns 1 on success or
       0 on failure.  It will treat as success the case where the OID already exists (even if the short name sn
       or long name ln provided as arguments differ from those associated with the existing OID, in which case
       the new names are not associated).

       The core_obj_add_sigid() function registers a new composite signature algorithm (sign_name) consisting of
       an underlying signature algorithm (pkey_name) and digest algorithm (digest_name) for the given handle. It
       assumes that the OIDs for the composite signature algorithm as well as for the underlying signature and
       digest algorithms are either already known to OpenSSL or have been registered via a call to
       core_obj_create(). It corresponds to the OpenSSL function OBJ_add_sigid(3), except that the objects are
       identified by name rather than a numeric NID. Any name (OID, short name or long name) can be used to
       identify the object. It will treat as success the case where the composite signature algorithm already
       exists (even if registered against a different underlying signature or digest algorithm). For
       digest_name, NULL or an empty string is permissible for signature algorithms that do not need a digest to
       operate correctly. The function returns 1 on success or 0 on failure.

       CRYPTO_malloc(), CRYPTO_zalloc(), CRYPTO_free(), CRYPTO_clear_free(), CRYPTO_realloc(),
       CRYPTO_clear_realloc(), CRYPTO_secure_malloc(), CRYPTO_secure_zalloc(), CRYPTO_secure_free(),
       CRYPTO_secure_clear_free(), CRYPTO_secure_allocated(), BIO_new_file(), BIO_new_mem_buf(), BIO_read_ex(),
       BIO_write_ex(), BIO_up_ref(), BIO_free(), BIO_vprintf(), BIO_vsnprintf(), BIO_gets(), BIO_puts(),
       BIO_ctrl(), OPENSSL_cleanse() and OPENSSL_hexstr2buf() correspond exactly to the public functions with
       the same name.  As a matter of fact, the pointers in the OSSL_DISPATCH(3) array are typically direct
       pointers to those public functions. Note that the BIO functions take an OSSL_CORE_BIO type rather than
       the standard BIO type. This is to ensure that a provider does not mix BIOs from the core with BIOs used
       on the provider side (the two are not compatible).  OSSL_SELF_TEST_set_callback() is used to set an
       optional callback that can be passed into a provider. This may be ignored by a provider.

       get_entropy() retrieves seeding material from the operating system.  The seeding material will have at
       least entropy bytes of randomness and the output will have at least min_len and at most max_len bytes.
       The buffer address is stored in *pout and the buffer length is returned to the caller.  On error, zero is
       returned.

       get_user_entropy() is the same as get_entropy() except that it will attempt to gather seed material via
       the seed source specified by a call to RAND_set_seed_source_type(3) or via "Random Configuration" in
       config(5).

       cleanup_entropy() is used to clean up and free the buffer returned by get_entropy().  The entropy pointer
       returned by get_entropy() is passed in buf and its length in len.

       cleanup_user_entropy() is used to clean up and free the buffer returned by get_user_entropy().  The
       entropy pointer returned by get_user_entropy() is passed in buf and its length in len.

       get_nonce() retrieves a nonce using the passed salt parameter of length salt_len and operating system
       specific information.  The salt should contain uniquely identifying information and this is included, in
       an unspecified manner, as part of the output.  The output is stored in a buffer which contains at least
       min_len and at most max_len bytes.  The buffer address is stored in *pout and the buffer length returned
       to the caller.  On error, zero is returned.

       get_user_nonce() is the same as get_nonce() except that it will attempt to gather seed material via the
       seed source specified by a call to RAND_set_seed_source_type(3) or via "Random Configuration" in
       config(5).

       cleanup_nonce() is used to clean up and free the buffer returned by get_nonce().  The nonce pointer
       returned by get_nonce() is passed in buf and its length in len.

       cleanup_user_nonce() is used to clean up and free the buffer returned by get_user_nonce().  The nonce
       pointer returned by get_user_nonce() is passed in buf and its length in len.

       provider_register_child_cb() registers callbacks for being informed about the loading and unloading of
       providers in the application's library context.  handle is this provider's handle and cbdata is this
       provider's data that will be passed back to the callbacks. It returns 1 on success or 0 otherwise. These
       callbacks may be called while holding locks in libcrypto. In order to avoid deadlocks the callback
       implementation must not be long running and must not call other OpenSSL API functions or upcalls.

       create_cb is a callback that will be called when a new provider is loaded into the application's library
       context. It is also called for any providers that are already loaded at the point that this callback is
       registered. The callback is passed the handle being used for the new provider being loadded and this
       provider's data in cbdata. It should return 1 on success or 0 on failure.

       remove_cb is a callback that will be called when a new provider is unloaded from the application's
       library context. It is passed the handle being used for the provider being unloaded and this provider's
       data in cbdata. It should return 1 on success or 0 on failure.

       global_props_cb is a callback that will be called when the global properties from the parent library
       context are changed. It should return 1 on success or 0 on failure.

       provider_deregister_child_cb() unregisters callbacks previously registered via
       provider_register_child_cb(). If provider_register_child_cb() has been called then
       provider_deregister_child_cb() should be called at or before the point that this provider's teardown
       function is called.

       provider_name() returns a string giving the name of the provider identified by handle.

       provider_get0_provider_ctx() returns the provider context that is associated with the provider identified
       by prov.

       provider_get0_dispatch() gets the dispatch table registered by the provider identified by prov when it
       initialised.

       provider_up_ref() increments the reference count on the provider prov. If activate is nonzero then the
       provider is also loaded if it is not already loaded. It returns 1 on success or 0 on failure.

       provider_free() decrements the reference count on the provider prov. If deactivate is nonzero then the
       provider is also unloaded if it is not already loaded. It returns 1 on success or 0 on failure.

   Provider functions
       provider_teardown() is called when a provider is shut down and removed from the core's provider store.
       It must free the passed provctx.

       provider_gettable_params() should return a constant array of descriptor OSSL_PARAM(3), for parameters
       that provider_get_params() can handle.

       provider_get_params() should process the OSSL_PARAM(3) array params, setting the values of the parameters
       it understands.

       provider_query_operation() should return a constant OSSL_ALGORITHM(3) that corresponds to the given
       operation_id.  It should indicate if the core may store a reference to this array by setting *no_store to
       0 (core may store a reference) or 1 (core may not store a reference).

       provider_unquery_operation() informs the provider that the result of a provider_query_operation() is no
       longer directly required and that the function pointers have been copied.  The operation_id should match
       that passed to provider_query_operation() and algs should be its return value.

       provider_get_reason_strings() should return a constant OSSL_ITEM(3) array that provides reason strings
       for reason codes the provider may use when reporting errors using core_put_error().

       The provider_get_capabilities() function should call the callback cb passing it a set of OSSL_PARAM(3)s
       and the caller supplied argument arg. The OSSL_PARAM(3)s should provide details about the capability with
       the name given in the capability argument relevant for the provider context provctx. If a provider
       supports multiple capabilities with the given name then it may call the callback multiple times (one for
       each capability). Capabilities can be useful for describing the services that a provider can offer. For
       further details see the "CAPABILITIES" section below. It should return 1 on success or 0 on error.

       The provider_self_test() function should perform known answer tests on a subset of the algorithms that it
       uses, and may also verify the integrity of the provider module. It should return 1 on success or 0 on
       error. It will return 1 if this function is not used.

       None of these functions are mandatory, but a provider is fairly useless without at least
       provider_query_operation(), and provider_gettable_params() is fairly useless if not accompanied by
       provider_get_params().

   Provider parameters
       provider_get_params() can return the following provider parameters to the core:

       "name" (OSSL_PROV_PARAM_NAME) <UTF8 ptr>
           This points to a string that should give a unique name for the provider.

       "version" (OSSL_PROV_PARAM_VERSION) <UTF8 ptr>
           This points to a string that is a version number associated with this provider.  OpenSSL in-built
           providers use OPENSSL_VERSION_STR, but this may be different for any third party provider. This
           string is for informational purposes only.

       "buildinfo" (OSSL_PROV_PARAM_BUILDINFO) <UTF8 ptr>
           This points to a string that is a build information associated with this provider.  OpenSSL in-built
           providers use OPENSSL_FULL_VERSION_STR, but this may be different for any third party provider.

       "status" (OSSL_PROV_PARAM_STATUS) <unsigned integer>
           This returns 0 if the provider has entered an error state, otherwise it returns 1.

       provider_gettable_params() should return the above parameters.

   Core parameters
       core_get_params() can retrieve the following core parameters for each provider:

       "openssl-version" (OSSL_PROV_PARAM_CORE_VERSION) <UTF8 string ptr>
           This points to the OpenSSL libraries' full version string, i.e. the string expanded from the macro
           OPENSSL_VERSION_STR.

       "provider-name" (OSSL_PROV_PARAM_CORE_PROV_NAME) <UTF8 string ptr>
           This points to the OpenSSL libraries' idea of what the calling provider is named.

       "module-filename" (OSSL_PROV_PARAM_CORE_MODULE_FILENAME) <UTF8 string ptr>
           This points to a string containing the full filename of the providers module file.

       Additionally, provider specific configuration parameters from the config file are available, in dotted
       name form.  The dotted name form is a concatenation of section names and final config command name
       separated by periods.

       For example, let's say we have the following config example:

        config_diagnostics = 1
        openssl_conf = openssl_init

        [openssl_init]
        providers = providers_sect

        [providers_sect]
        foo = foo_sect

        [foo_sect]
        activate = 1
        data1 = 2
        data2 = str
        more = foo_more

        [foo_more]
        data3 = foo,bar

       The provider will have these additional parameters available:

       "activate"
           pointing at the string "1"

       "data1"
           pointing at the string "2"

       "data2"
           pointing at the string "str"

       "more.data3"
           pointing at the string "foo,bar"

       For more information on handling parameters, see OSSL_PARAM(3) as OSSL_PARAM_int(3).

CAPABILITIES

       Capabilities describe some of the services that a provider can offer.  Applications can query the
       capabilities to discover those services.

       "TLS-GROUP" Capability

       The "TLS-GROUP" capability can be queried by libssl to discover the list of TLS groups that a provider
       can support. Each group supported can be used for key exchange (KEX) or key encapsulation method (KEM)
       during a TLS handshake.  TLS clients can advertise the list of TLS groups they support in the
       supported_groups extension, and TLS servers can select a group from the offered list that they also
       support. In this way a provider can add to the list of groups that libssl already supports with
       additional ones.

       Each TLS group that a provider supports should be described via the callback passed in through the
       provider_get_capabilities function. Each group should have the following details supplied (all are
       mandatory, except OSSL_CAPABILITY_TLS_GROUP_IS_KEM):

       "tls-group-name" (OSSL_CAPABILITY_TLS_GROUP_NAME) <UTF8 string>
           The name of the group as given in the IANA TLS Supported Groups registry
           <https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-parameters-8>.

       "tls-group-name-internal" (OSSL_CAPABILITY_TLS_GROUP_NAME_INTERNAL) <UTF8 string>
           The name of the group as known by the provider. This could be the same as the "tls-group-name", but
           does not have to be.

       "tls-group-id" (OSSL_CAPABILITY_TLS_GROUP_ID) <unsigned integer>
           The TLS group id value as given in the IANA TLS Supported Groups registry.

       "tls-group-alg" (OSSL_CAPABILITY_TLS_GROUP_ALG) <UTF8 string>
           The name of a Key Management algorithm that the provider offers and that should be used with this
           group. Keys created should be able to support key exchange or key encapsulation method (KEM), as
           implied by the optional OSSL_CAPABILITY_TLS_GROUP_IS_KEM flag.  The algorithm must support key and
           parameter generation as well as the key/parameter generation parameter, OSSL_PKEY_PARAM_GROUP_NAME.
           The group name given via "tls-group-name-internal" above will be passed via
           OSSL_PKEY_PARAM_GROUP_NAME when libssl wishes to generate keys/parameters.

       "tls-group-sec-bits" (OSSL_CAPABILITY_TLS_GROUP_SECURITY_BITS) <unsigned integer>
           The number of bits of security offered by keys in this group. The number of bits should be comparable
           with the ones given in table 2 and 3 of the NIST SP800-57 document.

       "tls-group-is-kem" (OSSL_CAPABILITY_TLS_GROUP_IS_KEM) <unsigned integer>
           Boolean flag to describe if the group should be used in key exchange (KEX) mode (0, default) or in
           key encapsulation method (KEM) mode (1).

           This parameter is optional: if not specified, KEX mode is assumed as the default mode for the group.

           In KEX mode, in a typical Diffie-Hellman fashion, both sides execute keygen then derive against the
           peer public key. To operate in KEX mode, the group implementation must support the provider functions
           as described in provider-keyexch(7).

           In KEM mode, the client executes keygen and sends its public key, the server executes encapsulate
           using the client's public key and sends back the resulting ciphertext, finally the client executes
           decapsulate to retrieve the same shared secret generated by the server's encapsulate. To operate in
           KEM mode, the group implementation must support the provider functions as described in
           provider-kem(7).

           Both in KEX and KEM mode, the resulting shared secret is then used according to the protocol
           specification.

       "tls-min-tls" (OSSL_CAPABILITY_TLS_GROUP_MIN_TLS) <integer>
       "tls-max-tls" (OSSL_CAPABILITY_TLS_GROUP_MAX_TLS) <integer>
       "tls-min-dtls" (OSSL_CAPABILITY_TLS_GROUP_MIN_DTLS) <integer>
       "tls-max-dtls" (OSSL_CAPABILITY_TLS_GROUP_MAX_DTLS) <integer>
           These parameters can be used to describe the minimum and maximum TLS and DTLS versions supported by
           the group. The values equate to the on-the-wire encoding of the various TLS versions. For example
           TLSv1.3 is 0x0304 (772 decimal), and TLSv1.2 is 0x0303 (771 decimal). A 0 indicates that there is no
           defined minimum or maximum. A -1 indicates that the group should not be used in that protocol.

       "TLS-SIGALG" Capability

       The "TLS-SIGALG" capability can be queried by libssl to discover the list of TLS signature algorithms
       that a provider can support. Each signature supported can be used for client- or server-authentication in
       addition to the built-in signature algorithms.  TLS1.3 clients can advertise the list of TLS signature
       algorithms they support in the signature_algorithms extension, and TLS servers can select an algorithm
       from the offered list that they also support. In this way a provider can add to the list of signature
       algorithms that libssl already supports with additional ones.

       Each TLS signature algorithm that a provider supports should be described via the callback passed in
       through the provider_get_capabilities function. Each algorithm can have the following details supplied:

       "iana-name" (OSSL_CAPABILITY_TLS_SIGALG_IANA_NAME) <UTF8 string>
           The name of the signature algorithm as given in the IANA TLS Signature Scheme registry as
           "Description":
           <https://www.iana.org/assignments/tls-parameters/tls-parameters.xhtml#tls-signaturescheme>.  This
           value must be supplied.

       "iana-code-point" (OSSL_CAPABILITY_TLS_SIGALG_CODE_POINT) <unsigned integer>
           The TLS algorithm ID value as given in the IANA TLS SignatureScheme registry.  This value must be
           supplied.

       "sigalg-name" (OSSL_CAPABILITY_TLS_SIGALG_NAME) <UTF8 string>
           A name for the full (possibly composite hash-and-signature) signature algorithm.  The provider may,
           but is not obligated to, provide a signature implementation with this name; if it doesn't, this is
           assumed to be a composite of a pure signature algorithm and a hash algorithm, which must be given
           with the parameters "sig-name" and "hash-name".  This value must be supplied.

       "sigalg-oid" (OSSL_CAPABILITY_TLS_SIGALG_OID) <UTF8 string>
           The OID of the "sigalg-name" algorithm in canonical numeric text form. If this parameter is given,
           OBJ_create() will be used to create an OBJ and a NID for this OID, using the "sigalg-name" parameter
           for its (short) name.  Otherwise, it's assumed to already exist in the object database, possibly done
           by the provider with the core_obj_create() upcall.  This value is optional.

       "sig-name" (OSSL_CAPABILITY_TLS_SIGALG_SIG_NAME) <UTF8 string>
           The name of the pure signature algorithm that is part of a composite "sigalg-name". If "sigalg-name"
           is implemented by the provider, this parameter is redundant and must not be given.  This value is
           optional.

       "sig-oid" (OSSL_CAPABILITY_TLS_SIGALG_SIG_OID) <UTF8 string>
           The OID of the "sig-name" algorithm in canonical numeric text form. If this parameter is given,
           OBJ_create() will be used to create an OBJ and a NID for this OID, using the "sig-name" parameter for
           its (short) name.  Otherwise, it is assumed to already exist in the object database. This can be done
           by the provider using the core_obj_create() upcall.  This value is optional.

       "hash-name" (OSSL_CAPABILITY_TLS_SIGALG_HASH_NAME) <UTF8 string>
           The name of the hash algorithm that is part of a composite "sigalg-name".  If "sigalg-name" is
           implemented by the provider, this parameter is redundant and must not be given.  This value is
           optional.

       "hash-oid" (OSSL_CAPABILITY_TLS_SIGALG_HASH_OID) <UTF8 string>
           The OID of the "hash-name" algorithm in canonical numeric text form. If this parameter is given,
           OBJ_create() will be used to create an OBJ and a NID for this OID, using the "hash-name" parameter
           for its (short) name.  Otherwise, it's assumed to already exist in the object database, possibly done
           by the provider with the core_obj_create() upcall.  This value is optional.

       "key-type" (OSSL_CAPABILITY_TLS_SIGALG_KEYTYPE) <UTF8 string>
           The key type of the public key of applicable certificates. If this parameter isn't present, it's
           assumed to be the same as "sig-name" if that's present, otherwise "sigalg-name".  This value is
           optional.

       "key-type-oid" (OSSL_CAPABILITY_TLS_SIGALG_KEYTYPE_OID) <UTF8 string>
           The OID of the "key-type" in canonical numeric text form. If this parameter is given, OBJ_create()
           will be used to create an OBJ and a NID for this OID, using the "key-type" parameter for its (short)
           name.  Otherwise, it's assumed to already exist in the object database, possibly done by the provider
           with the core_obj_create() upcall.  This value is optional.

       "sec-bits" (OSSL_CAPABILITY_TLS_SIGALG_SECURITY_BITS) <unsigned integer>
           The number of bits of security offered by keys of this algorithm. The number of bits should be
           comparable with the ones given in table 2 and 3 of the NIST SP800-57 document. This number is used to
           determine the security strength of the algorithm if no digest algorithm has been registered that
           otherwise defines the security strength. If the signature algorithm implements its own digest
           internally, this value needs to be set to properly reflect the overall security strength.  This value
           must be supplied.

       "tls-min-tls" (OSSL_CAPABILITY_TLS_SIGALG_MIN_TLS) <integer>
       "tls-max-tls" (OSSL_CAPABILITY_TLS_SIGALG_MAX_TLS) <integer>
           These parameters can be used to describe the minimum and maximum TLS versions supported by the
           signature algorithm. The values equate to the on-the-wire encoding of the various TLS versions. For
           example TLSv1.3 is 0x0304 (772 decimal), and TLSv1.2 is 0x0303 (771 decimal). A 0 indicates that
           there is no defined minimum or maximum. A -1 indicates that the signature algorithm should not be
           used in that protocol.  Presently values representing anything other than TLS1.3 mean that the
           complete algorithm is ignored.

NOTES

       The core_obj_create() and core_obj_add_sigid() functions were not thread safe in OpenSSL 3.0.

EXAMPLES

       This is an example of a simple provider made available as a dynamically loadable module.  It implements
       the fictitious algorithm "FOO" for the fictitious operation "BAR".

        #include <malloc.h>
        #include <openssl/core.h>
        #include <openssl/core_dispatch.h>

        /* Errors used in this provider */
        #define E_MALLOC       1

        static const OSSL_ITEM reasons[] = {
            { E_MALLOC, "memory allocation failure" }.
            OSSL_DISPATCH_END
        };

        /*
         * To ensure we get the function signature right, forward declare
         * them using function types provided by openssl/core_dispatch.h
         */
        OSSL_FUNC_bar_newctx_fn foo_newctx;
        OSSL_FUNC_bar_freectx_fn foo_freectx;
        OSSL_FUNC_bar_init_fn foo_init;
        OSSL_FUNC_bar_update_fn foo_update;
        OSSL_FUNC_bar_final_fn foo_final;

        OSSL_FUNC_provider_query_operation_fn p_query;
        OSSL_FUNC_provider_get_reason_strings_fn p_reasons;
        OSSL_FUNC_provider_teardown_fn p_teardown;

        OSSL_provider_init_fn OSSL_provider_init;

        OSSL_FUNC_core_put_error *c_put_error = NULL;

        /* Provider context */
        struct prov_ctx_st {
            OSSL_CORE_HANDLE *handle;
        }

        /* operation context for the algorithm FOO */
        struct foo_ctx_st {
            struct prov_ctx_st *provctx;
            int b;
        };

        static void *foo_newctx(void *provctx)
        {
            struct foo_ctx_st *fooctx = malloc(sizeof(*fooctx));

            if (fooctx != NULL)
                fooctx->provctx = provctx;
            else
                c_put_error(provctx->handle, E_MALLOC, __FILE__, __LINE__);
            return fooctx;
        }

        static void foo_freectx(void *fooctx)
        {
            free(fooctx);
        }

        static int foo_init(void *vfooctx)
        {
            struct foo_ctx_st *fooctx = vfooctx;

            fooctx->b = 0x33;
        }

        static int foo_update(void *vfooctx, unsigned char *in, size_t inl)
        {
            struct foo_ctx_st *fooctx = vfooctx;

            /* did you expect something serious? */
            if (inl == 0)
                return 1;
            for (; inl-- > 0; in++)
                *in ^= fooctx->b;
            return 1;
        }

        static int foo_final(void *vfooctx)
        {
            struct foo_ctx_st *fooctx = vfooctx;

            fooctx->b = 0x66;
        }

        static const OSSL_DISPATCH foo_fns[] = {
            { OSSL_FUNC_BAR_NEWCTX, (void (*)(void))foo_newctx },
            { OSSL_FUNC_BAR_FREECTX, (void (*)(void))foo_freectx },
            { OSSL_FUNC_BAR_INIT, (void (*)(void))foo_init },
            { OSSL_FUNC_BAR_UPDATE, (void (*)(void))foo_update },
            { OSSL_FUNC_BAR_FINAL, (void (*)(void))foo_final },
            OSSL_DISPATCH_END
        };

        static const OSSL_ALGORITHM bars[] = {
            { "FOO", "provider=chumbawamba", foo_fns },
            { NULL, NULL, NULL }
        };

        static const OSSL_ALGORITHM *p_query(void *provctx, int operation_id,
                                             int *no_store)
        {
            switch (operation_id) {
            case OSSL_OP_BAR:
                return bars;
            }
            return NULL;
        }

        static const OSSL_ITEM *p_reasons(void *provctx)
        {
            return reasons;
        }

        static void p_teardown(void *provctx)
        {
            free(provctx);
        }

        static const OSSL_DISPATCH prov_fns[] = {
            { OSSL_FUNC_PROVIDER_TEARDOWN, (void (*)(void))p_teardown },
            { OSSL_FUNC_PROVIDER_QUERY_OPERATION, (void (*)(void))p_query },
            { OSSL_FUNC_PROVIDER_GET_REASON_STRINGS, (void (*)(void))p_reasons },
            OSSL_DISPATCH_END
        };

        int OSSL_provider_init(const OSSL_CORE_HANDLE *handle,
                               const OSSL_DISPATCH *in,
                               const OSSL_DISPATCH **out,
                               void **provctx)
        {
            struct prov_ctx_st *pctx = NULL;

            for (; in->function_id != 0; in++)
                switch (in->function_id) {
                case OSSL_FUNC_CORE_PUT_ERROR:
                    c_put_error = OSSL_FUNC_core_put_error(in);
                    break;
                }

            *out = prov_fns;

            if ((pctx = malloc(sizeof(*pctx))) == NULL) {
                /*
                 * ALEA IACTA EST, if the core retrieves the reason table
                 * regardless, that string will be displayed, otherwise not.
                 */
                c_put_error(handle, E_MALLOC, __FILE__, __LINE__);
                return 0;
            }
            pctx->handle = handle;
            return 1;
        }

       This relies on a few things existing in openssl/core_dispatch.h:

        #define OSSL_OP_BAR            4711

        #define OSSL_FUNC_BAR_NEWCTX      1
        typedef void *(OSSL_FUNC_bar_newctx_fn)(void *provctx);
        static ossl_inline OSSL_FUNC_bar_newctx(const OSSL_DISPATCH *opf)
        { return (OSSL_FUNC_bar_newctx_fn *)opf->function; }

        #define OSSL_FUNC_BAR_FREECTX     2
        typedef void (OSSL_FUNC_bar_freectx_fn)(void *ctx);
        static ossl_inline OSSL_FUNC_bar_freectx(const OSSL_DISPATCH *opf)
        { return (OSSL_FUNC_bar_freectx_fn *)opf->function; }

        #define OSSL_FUNC_BAR_INIT        3
        typedef void *(OSSL_FUNC_bar_init_fn)(void *ctx);
        static ossl_inline OSSL_FUNC_bar_init(const OSSL_DISPATCH *opf)
        { return (OSSL_FUNC_bar_init_fn *)opf->function; }

        #define OSSL_FUNC_BAR_UPDATE      4
        typedef void *(OSSL_FUNC_bar_update_fn)(void *ctx,
                                              unsigned char *in, size_t inl);
        static ossl_inline OSSL_FUNC_bar_update(const OSSL_DISPATCH *opf)
        { return (OSSL_FUNC_bar_update_fn *)opf->function; }

        #define OSSL_FUNC_BAR_FINAL       5
        typedef void *(OSSL_FUNC_bar_final_fn)(void *ctx);
        static ossl_inline OSSL_FUNC_bar_final(const OSSL_DISPATCH *opf)
        { return (OSSL_FUNC_bar_final_fn *)opf->function; }

SEE ALSO

       provider(7)

HISTORY

       The concept of providers and everything surrounding them was introduced in OpenSSL 3.0.

       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>.