# man > provider-mac(7ssl) [PROVIDER-MAC(7SSL)](https://www.chedong.com/phpMan.php/man/PROVIDER-MAC/7SSL/markdown) OpenSSL [PROVIDER-MAC(7SSL)](https://www.chedong.com/phpMan.php/man/PROVIDER-MAC/7SSL/markdown) ## NAME provider-mac - The mac library <-> provider functions ## SYNOPSIS #include #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. */ /* Context management */ void *OSSL_FUNC_mac_newctx(void *provctx); void OSSL_FUNC_mac_freectx(void *mctx); void *OSSL_FUNC_mac_dupctx(void *src); /* Encryption/decryption */ int OSSL_FUNC_mac_init(void *mctx, unsigned char *key, size_t keylen, const OSSL_PARAM params[]); int OSSL_FUNC_mac_update(void *mctx, const unsigned char *in, size_t inl); int OSSL_FUNC_mac_final(void *mctx, unsigned char *out, size_t *outl, size_t outsize); /* MAC parameter descriptors */ const OSSL_PARAM *OSSL_FUNC_mac_gettable_params(void *provctx); const OSSL_PARAM *OSSL_FUNC_mac_gettable_ctx_params(void *mctx, void *provctx); const OSSL_PARAM *OSSL_FUNC_mac_settable_ctx_params(void *mctx, void *provctx); /* MAC parameters */ int OSSL_FUNC_mac_get_params(OSSL_PARAM params[]); int OSSL_FUNC_mac_get_ctx_params(void *mctx, OSSL_PARAM params[]); int OSSL_FUNC_mac_set_ctx_params(void *mctx, const OSSL_PARAM params[]); ## DESCRIPTION This documentation is primarily aimed at provider authors. See [**provider**(7)](https://www.chedong.com/phpMan.php/man/provider/7/markdown) for further information. The MAC operation enables providers to implement mac algorithms and make them available to applications via the API functions **EVP**___**MAC**___**[init**(3)](https://www.chedong.com/phpMan.php/man/init/3/markdown), **EVP**___**MAC**___**[update**(3)](https://www.chedong.com/phpMan.php/man/update/3/markdown) and **EVP**___**MAC**___**[final**(3)](https://www.chedong.com/phpMan.php/man/final/3/markdown). All "functions" mentioned here are passed as function pointers between _libcrypto_ and the provider in **OSSL**___**DISPATCH** arrays via **OSSL**___**ALGORITHM** arrays that are returned by the provider's **provider**___**query**___**operation()** function (see "Provider Functions" in [**provider-base**(7)](https://www.chedong.com/phpMan.php/man/provider-base/7/markdown)). All these "functions" have a corresponding function type definition named **OSSL**___**FUNC**___**{name}**___**fn**, and a helper function to retrieve the function pointer from an **OSSL**___**DISPATCH** element named **OSSL**___**FUNC**___**{name}**. For example, the "function" **OSSL**___**FUNC**___**mac**___**newctx()** has these: typedef void *(OSSL_OSSL_FUNC_mac_newctx_fn)(void *provctx); static ossl_inline OSSL_OSSL_FUNC_mac_newctx_fn OSSL_FUNC_mac_newctx(const OSSL_DISPATCH *opf); **OSSL**___**DISPATCH** arrays are indexed by numbers that are provided as macros in **openssl-core**___**[dispatch.h**(7)](https://www.chedong.com/phpMan.php/man/dispatch.h/7/markdown), as follows: OSSL_FUNC_mac_newctx OSSL_FUNC_MAC_NEWCTX OSSL_FUNC_mac_freectx OSSL_FUNC_MAC_FREECTX OSSL_FUNC_mac_dupctx OSSL_FUNC_MAC_DUPCTX OSSL_FUNC_mac_init OSSL_FUNC_MAC_INIT OSSL_FUNC_mac_update OSSL_FUNC_MAC_UPDATE OSSL_FUNC_mac_final OSSL_FUNC_MAC_FINAL OSSL_FUNC_mac_get_params OSSL_FUNC_MAC_GET_PARAMS OSSL_FUNC_mac_get_ctx_params OSSL_FUNC_MAC_GET_CTX_PARAMS OSSL_FUNC_mac_set_ctx_params OSSL_FUNC_MAC_SET_CTX_PARAMS OSSL_FUNC_mac_gettable_params OSSL_FUNC_MAC_GETTABLE_PARAMS OSSL_FUNC_mac_gettable_ctx_params OSSL_FUNC_MAC_GETTABLE_CTX_PARAMS OSSL_FUNC_mac_settable_ctx_params OSSL_FUNC_MAC_SETTABLE_CTX_PARAMS A mac algorithm implementation may not implement all of these functions. In order to be a consistent set of functions, at least the following functions must be implemented: **OSSL**___**FUNC**___**mac**___**newctx()**, **OSSL**___**FUNC**___**mac**___**freectx()**, **OSSL**___**FUNC**___**mac**___**init()**, **OSSL**___**FUNC**___**mac**___**update()**, **OSSL**___**FUNC**___**mac**___**final()**. All other functions are optional. ### Context Management Functions **OSSL**___**FUNC**___**mac**___**newctx()** should create and return a pointer to a provider side structure for holding context information during a mac operation. A pointer to this context will be passed back in a number of the other mac operation function calls. The parameter _provctx_ is the provider context generated during provider initialisation (see [**provider**(7)](https://www.chedong.com/phpMan.php/man/provider/7/markdown)). **OSSL**___**FUNC**___**mac**___**freectx()** is passed a pointer to the provider side mac context in the _mctx_ parameter. If it receives NULL as _mctx_ value, it should not do anything other than return. This function should free any resources associated with that context. **OSSL**___**FUNC**___**mac**___**dupctx()** should duplicate the provider side mac context in the _mctx_ parameter and return the duplicate copy. ### Encryption/Decryption Functions **OSSL**___**FUNC**___**mac**___**init()** initialises a mac operation given a newly created provider side mac context in the _mctx_ parameter. The _params_ are set before setting the MAC _key_ of _keylen_ bytes. **OSSL**___**FUNC**___**mac**___**update()** is called to supply data for MAC computation of a previously initialised mac operation. The _mctx_ parameter contains a pointer to a previously initialised provider side context. **OSSL**___**FUNC**___**mac**___**update()** may be called multiple times for a single mac operation. **OSSL**___**FUNC**___**mac**___**final()** completes the MAC computation started through previous **OSSL**___**FUNC**___**mac**___**init()** and **OSSL**___**FUNC**___**mac**___**update()** calls. The _mctx_ parameter contains a pointer to the provider side context. The resulting MAC should be written to _out_ and the amount of data written to _*outl_, which should not exceed _outsize_ bytes. The same expectations apply to _outsize_ as documented for **EVP**___**MAC**___**[final**(3)](https://www.chedong.com/phpMan.php/man/final/3/markdown). ### Mac Parameters See **OSSL**___**[PARAM**(3)](https://www.chedong.com/phpMan.php/man/PARAM/3/markdown) for further details on the parameters structure used by these functions. **OSSL**___**FUNC**___**mac**___**get**___**params()** gets details of parameter values associated with the provider algorithm and stores them in _params_. **OSSL**___**FUNC**___**mac**___**set**___**ctx**___**params()** sets mac parameters associated with the given provider side mac context _mctx_ to _params_. Any parameter settings are additional to any that were previously set. Passing NULL for _params_ should return true. **OSSL**___**FUNC**___**mac**___**get**___**ctx**___**params()** gets details of currently set parameter values associated with the given provider side mac context _mctx_ and stores them in _params_. Passing NULL for _params_ should return true. **OSSL**___**FUNC**___**mac**___**gettable**___**params()**, **OSSL**___**FUNC**___**mac**___**gettable**___**ctx**___**params()**, and **OSSL**___**FUNC**___**mac**___**settable**___**ctx**___**params()** all return constant **OSSL**___**PARAM** arrays as descriptors of the parameters that **OSSL**___**FUNC**___**mac**___**get**___**params()**, **OSSL**___**FUNC**___**mac**___**get**___**ctx**___**params()**, and **OSSL**___**FUNC**___**mac**___**set**___**ctx**___**params()** can handle, respectively. **OSSL**___**FUNC**___**mac**___**gettable**___**ctx**___**params()** and **OSSL**___**FUNC**___**mac**___**settable**___**ctx**___**params()** will return the parameters associated with the provider side context _mctx_ in its current state if it is not NULL. Otherwise, they return the parameters associated with the provider side algorithm _provctx_. All MAC implementations are expected to handle the following parameters: with **OSSL**___**FUNC**___**set**___**ctx**___**params()**: "key" (**OSSL**___**MAC**___**PARAM**___**KEY**) Sets the key in the associated MAC ctx. This is identical to passing a _key_ argument to the **OSSL**___**FUNC**___**mac**___**init()** function. with **OSSL**___**FUNC**___**get**___**params()**: "size" (**OSSL**___**MAC**___**PARAM**___**SIZE**) Can be used to get the default MAC size (which might be the only allowable MAC size for the implementation). Note that some implementations allow setting the size that the resulting MAC should have as well, see the documentation of the implementation. "size" (**OSSL**___**MAC**___**PARAM**___**BLOCK**___**SIZE**) Can be used to get the MAC block size (if supported by the algorithm). ## NOTES The MAC life-cycle is described in **life**___**[cycle-rand**(7)](https://www.chedong.com/phpMan.php/man/cycle-rand/7/markdown). Providers should ensure that the various transitions listed there are supported. At some point the EVP layer will begin enforcing the listed transitions. ## RETURN VALUES **OSSL**___**FUNC**___**mac**___**newctx()** and **OSSL**___**FUNC**___**mac**___**dupctx()** should return the newly created provider side mac context, or NULL on failure. **OSSL**___**FUNC**___**mac**___**init()**, **OSSL**___**FUNC**___**mac**___**update()**, **OSSL**___**FUNC**___**mac**___**final()**, **OSSL**___**FUNC**___**mac**___**get**___**params()**, **OSSL**___**FUNC**___**mac**___**get**___**ctx**___**params()** and **OSSL**___**FUNC**___**mac**___**set**___**ctx**___**params()** should return 1 for success or 0 on error. **OSSL**___**FUNC**___**mac**___**gettable**___**params()**, **OSSL**___**FUNC**___**mac**___**gettable**___**ctx**___**params()** and **OSSL**___**FUNC**___**mac**___**settable**___**ctx**___**params()** should return a constant **OSSL**___**PARAM** array, or NULL if none is offered. ## SEE ALSO [**provider**(7)](https://www.chedong.com/phpMan.php/man/provider/7/markdown), **EVP**___**[MAC-BLAKE2**(7)](https://www.chedong.com/phpMan.php/man/MAC-BLAKE2/7/markdown), **EVP**___**[MAC-CMAC**(7)](https://www.chedong.com/phpMan.php/man/MAC-CMAC/7/markdown), **EVP**___**[MAC-GMAC**(7)](https://www.chedong.com/phpMan.php/man/MAC-GMAC/7/markdown), **EVP**___**[MAC-HMAC**(7)](https://www.chedong.com/phpMan.php/man/MAC-HMAC/7/markdown), **EVP**___**[MAC-KMAC**(7)](https://www.chedong.com/phpMan.php/man/MAC-KMAC/7/markdown), **EVP**___**[MAC-Poly1305**(7)](https://www.chedong.com/phpMan.php/man/MAC-Poly1305/7/markdown), **EVP**___**[MAC-Siphash**(7)](https://www.chedong.com/phpMan.php/man/MAC-Siphash/7/markdown), **life**___**[cycle-mac**(7)](https://www.chedong.com/phpMan.php/man/cycle-mac/7/markdown), **EVP**___**[MAC**(3)](https://www.chedong.com/phpMan.php/man/MAC/3/markdown) ## HISTORY The provider MAC interface was introduced in OpenSSL 3.0. ## COPYRIGHT Copyright 2019-2021 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 <>. 3.0.2 2026-06-02 [PROVIDER-MAC(7SSL)](https://www.chedong.com/phpMan.php/man/PROVIDER-MAC/7SSL/markdown)