# provider-base - The basic OpenSSL library provider functions - man(7ssl) - [phpMan] [_PROVIDER-BASE_(7SSL)](https://www.chedong.com/phpMan.php/man/PROVIDER-BASE/7SSL/markdown) OpenSSL [_PROVIDER-BASE_(7SSL)](https://www.chedong.com/phpMan.php/man/PROVIDER-BASE/7SSL/markdown) ## NAME provider-base - The basic OpenSSL library <-> provider functions ## SYNOPSIS #include /* * 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); void cleanup_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); void cleanup_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)](https://www.chedong.com/phpMan.php/man/OSSLDISPATCH/3/markdown) arrays, in the call of the provider initialization function. See "Provider" in [**provider**(7)](https://www.chedong.com/phpMan.php/man/provider/7/markdown) 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)](https://www.chedong.com/phpMan.php/man/OSSLDISPATCH/3/markdown) 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)](https://www.chedong.com/phpMan.php/man/OSSLDISPATCH/3/markdown) arrays are indexed by numbers that are provided as macros in [**openssl-core_dispatch.h**(7)](https://www.chedong.com/phpMan.php/man/openssl-coredispatch.h/7/markdown), as follows: For _in_ (the [**OSSL_DISPATCH**(3)](https://www.chedong.com/phpMan.php/man/OSSLDISPATCH/3/markdown) 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_cleanup_entropy OSSL_FUNC_CLEANUP_ENTROPY ossl_rand_get_nonce OSSL_FUNC_GET_NONCE ossl_rand_cleanup_nonce OSSL_FUNC_CLEANUP_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)](https://www.chedong.com/phpMan.php/man/OSSLDISPATCH/3/markdown) 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)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown), 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)](https://www.chedong.com/phpMan.php/man/OSSLLIBCTXnewchild/3/markdown) 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)](https://www.chedong.com/phpMan.php/man/ERRnew/3/markdown). ### 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)](https://www.chedong.com/phpMan.php/man/ERRsetdebug/3/markdown). ### 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)](https://www.chedong.com/phpMan.php/man/ERRvseterror/3/markdown). 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)](https://www.chedong.com/phpMan.php/man/OBJcreate/3/markdown) 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). This function is not thread safe. 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)](https://www.chedong.com/phpMan.php/man/OBJaddsigid/3/markdown), 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. This function is not thread safe. **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)](https://www.chedong.com/phpMan.php/man/OSSLDISPATCH/3/markdown) 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. **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**. **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. **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**. **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)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown), for parameters that **provider_get_params() **can handle. **provider_get_params() **should process the [**OSSL_PARAM**(3)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown) array _params_, setting the values of the parameters it understands. **provider_query_operation() **should return a constant [**OSSL_ALGORITHM**(3)](https://www.chedong.com/phpMan.php/man/OSSLALGORITHM/3/markdown) 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)](https://www.chedong.com/phpMan.php/man/OSSLITEM/3/markdown) 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)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown)s and the caller supplied argument _arg_. The [**OSSL_PARAM**(3)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown)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**) This points to a string that should give a unique name for the provider. "version" (**OSSL_PROV_PARAM_VERSION**) 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**) 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**) 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**) 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**) This points to the OpenSSL libraries' idea of what the calling provider is named. "module-filename" (**OSSL_PROV_PARAM_CORE_MODULE_FILENAME**) 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)](https://www.chedong.com/phpMan.php/man/OSSLPARAM/3/markdown) as [**OSSL_PARAM_int**(3)](https://www.chedong.com/phpMan.php/man/OSSLPARAMint/3/markdown). ## 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**) The name of the group as given in the IANA TLS Supported Groups registry <>. "tls-group-name-internal" (**OSSL_CAPABILITY_TLS_GROUP_NAME_INTERNAL**) 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**) The TLS group id value as given in the IANA TLS Supported Groups registry. "tls-group-alg" (**OSSL_CAPABILITY_TLS_GROUP_ALG**) 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**) 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**) 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)](https://www.chedong.com/phpMan.php/man/provider-keyexch/7/markdown). 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)](https://www.chedong.com/phpMan.php/man/provider-kem/7/markdown). 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**) "tls-max-tls" (**OSSL_CAPABILITY_TLS_GROUP_MAX_TLS**) "tls-min-dtls" (**OSSL_CAPABILITY_TLS_GROUP_MIN_DTLS**) "tls-max-dtls" (**OSSL_CAPABILITY_TLS_GROUP_MAX_DTLS**) 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. ## 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 #include #include /* Errors used in this provider */ #define E_MALLOC 1 static const OSSL_ITEM reasons[] = { { E_MALLOC, "memory allocation failure" }. { 0, NULL } /* Termination */ }; /* * 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 }, { 0, NULL } }; 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 }, { 0, NULL } }; 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)](https://www.chedong.com/phpMan.php/man/provider/7/markdown) ## HISTORY The concept of providers and everything surrounding them was introduced 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 <>. 3.0.13 2026-07-29 [_PROVIDER-BASE_(7SSL)](https://www.chedong.com/phpMan.php/man/PROVIDER-BASE/7SSL/markdown)