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EVP_MAC(3ossl)                      OpenSSL                     EVP_MAC(3ossl)



NAME

       EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free, EVP_MAC_is_a,
       EVP_MAC_get0_name, EVP_MAC_names_do_all, EVP_MAC_get0_description,
       EVP_MAC_get0_provider, EVP_MAC_get_params, EVP_MAC_gettable_params,
       EVP_MAC_CTX, EVP_MAC_CTX_new, EVP_MAC_CTX_free, EVP_MAC_CTX_dup,
       EVP_MAC_CTX_get0_mac, EVP_MAC_CTX_get_params, EVP_MAC_CTX_set_params,
       EVP_MAC_CTX_get_mac_size, EVP_MAC_CTX_get_block_size, EVP_Q_mac,
       EVP_MAC_init, EVP_MAC_update, EVP_MAC_final, EVP_MAC_finalXOF,
       EVP_MAC_gettable_ctx_params, EVP_MAC_settable_ctx_params,
       EVP_MAC_CTX_gettable_params, EVP_MAC_CTX_settable_params,
       EVP_MAC_do_all_provided - EVP MAC routines


SYNOPSIS

        #include <openssl/evp.h>

        typedef struct evp_mac_st EVP_MAC;
        typedef struct evp_mac_ctx_st EVP_MAC_CTX;

        EVP_MAC *EVP_MAC_fetch(OSSL_LIB_CTX *libctx, const char *algorithm,
                               const char *properties);
        int EVP_MAC_up_ref(EVP_MAC *mac);
        void EVP_MAC_free(EVP_MAC *mac);
        int EVP_MAC_is_a(const EVP_MAC *mac, const char *name);
        const char *EVP_MAC_get0_name(const EVP_MAC *mac);
        int EVP_MAC_names_do_all(const EVP_MAC *mac,
                                 void (*fn)(const char *name, void *data),
                                 void *data);
        const char *EVP_MAC_get0_description(const EVP_MAC *mac);
        const OSSL_PROVIDER *EVP_MAC_get0_provider(const EVP_MAC *mac);
        int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]);

        EVP_MAC_CTX *EVP_MAC_CTX_new(EVP_MAC *mac);
        void EVP_MAC_CTX_free(EVP_MAC_CTX *ctx);
        EVP_MAC_CTX *EVP_MAC_CTX_dup(const EVP_MAC_CTX *src);
        EVP_MAC *EVP_MAC_CTX_get0_mac(EVP_MAC_CTX *ctx);
        int EVP_MAC_CTX_get_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]);
        int EVP_MAC_CTX_set_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]);

        size_t EVP_MAC_CTX_get_mac_size(EVP_MAC_CTX *ctx);
        size_t EVP_MAC_CTX_get_block_size(EVP_MAC_CTX *ctx);
        unsigned char *EVP_Q_mac(OSSL_LIB_CTX *libctx, const char *name, const char *propq,
                                 const char *subalg, const OSSL_PARAM *params,
                                 const void *key, size_t keylen,
                                 const unsigned char *data, size_t datalen,
                                 unsigned char *out, size_t outsize, size_t *outlen);
        int EVP_MAC_init(EVP_MAC_CTX *ctx, const unsigned char *key, size_t keylen,
                         const OSSL_PARAM params[]);
        int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
        int EVP_MAC_final(EVP_MAC_CTX *ctx,
                          unsigned char *out, size_t *outl, size_t outsize);
        int EVP_MAC_finalXOF(EVP_MAC_CTX *ctx, unsigned char *out, size_t outsize);

        const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
        const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
        const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
        const OSSL_PARAM *EVP_MAC_CTX_gettable_params(EVP_MAC_CTX *ctx);
        const OSSL_PARAM *EVP_MAC_CTX_settable_params(EVP_MAC_CTX *ctx);

        void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx,
                                     void (*fn)(EVP_MAC *mac, void *arg),
                                     void *arg);


DESCRIPTION

       These types and functions help the application to calculate MACs of
       different types and with different underlying algorithms if there are
       any.

       MACs are a bit complex insofar that some of them use other algorithms
       for actual computation.  HMAC uses a digest, and CMAC uses a cipher.
       Therefore, there are sometimes two contexts to keep track of, one for
       the MAC algorithm itself and one for the underlying computation
       algorithm if there is one.

       To make things less ambiguous, this manual talks about a "context" or
       "MAC context", which is to denote the MAC level context, and about a
       "underlying context", or "computation context", which is to denote the
       context for the underlying computation algorithm if there is one.

   Types
       EVP_MAC is a type that holds the implementation of a MAC.

       EVP_MAC_CTX is a context type that holds internal MAC information as
       well as a reference to a computation context, for those MACs that rely
       on an underlying computation algorithm.

   Algorithm implementation fetching
       EVP_MAC_fetch() fetches an implementation of a MAC algorithm, given a
       library context libctx and a set of properties.  See "ALGORITHM
       FETCHING" in crypto(7) for further information.

       See "Message Authentication Code (MAC)" in OSSL_PROVIDER-default(7) for
       the list of algorithms supported by the default provider.

       The returned value must eventually be freed with EVP_MAC_free(3).

       EVP_MAC_up_ref() increments the reference count of an already fetched
       MAC.

       EVP_MAC_free() frees a fetched algorithm.  NULL is a valid parameter,
       for which this function is a no-op.

   Context manipulation functions
       EVP_MAC_CTX_new() creates a new context for the MAC type mac.  The
       created context can then be used with most other functions described
       here.

       EVP_MAC_CTX_free() frees the contents of the context, including an
       underlying context if there is one, as well as the context itself.
       NULL is a valid parameter, for which this function is a no-op.

       EVP_MAC_CTX_dup() duplicates the src context and returns a newly
       allocated context.

       EVP_MAC_CTX_get0_mac() returns the EVP_MAC associated with the context
       ctx.

   Computing functions
       EVP_Q_mac() computes the message authentication code of data with
       length datalen using the MAC algorithm name and the key key with length
       keylen.  The MAC algorithm is fetched using any given libctx and
       property query string propq. It takes parameters subalg and further
       params, both of which may be NULL if not needed.  If out is not NULL,
       it places the result in the memory pointed at by out, but only if
       outsize is sufficient (otherwise no computation is made).  If out is
       NULL, it allocates and uses a buffer of suitable length, which will be
       returned on success and must be freed by the caller.  In either case,
       also on error, it assigns the number of bytes written to *outlen unless
       outlen is NULL.

       EVP_MAC_init() sets up the underlying context ctx with information
       given via the key and params arguments.  The MAC key has a length of
       keylen and the parameters in params are processed before setting the
       key.  If key is NULL, the key must be set via params either as part of
       this call or separately using EVP_MAC_CTX_set_params().  Providing
       non-NULL params to this function is equivalent to calling
       EVP_MAC_CTX_set_params() with those params for the same ctx beforehand.
       Note: There are additional requirements for some MAC algorithms during
       re-initalization (i.e. calling EVP_MAC_init() on an EVP_MAC after
       EVP_MAC_final() has been called on the same object).  See the NOTES
       section below.

       EVP_MAC_init() should be called before EVP_MAC_update() and
       EVP_MAC_final().

       EVP_MAC_update() adds datalen bytes from data to the MAC input.

       EVP_MAC_final() does the final computation and stores the result in the
       memory pointed at by out of size outsize, and sets the number of bytes
       written in *outl at.  If out is NULL or outsize is too small, then no
       computation is made.  To figure out what the output length will be and
       allocate space for it dynamically, simply call with out being NULL and
       outl pointing at a valid location, then allocate space and make a
       second call with out pointing at the allocated space.

       EVP_MAC_finalXOF() does the final computation for an XOF based MAC and
       stores the result in the memory pointed at by out of size outsize.

       EVP_MAC_get_params() retrieves details about the implementation mac.
       The set of parameters given with params determine exactly what
       parameters should be retrieved.  Note that a parameter that is unknown
       in the underlying context is simply ignored.

       EVP_MAC_CTX_get_params() retrieves chosen parameters, given the context
       ctx and its underlying context.  The set of parameters given with
       params determine exactly what parameters should be retrieved.  Note
       that a parameter that is unknown in the underlying context is simply
       ignored.

       EVP_MAC_CTX_set_params() passes chosen parameters to the underlying
       context, given a context ctx.  The set of parameters given with params
       determine exactly what parameters are passed down.  If params are NULL,
       the underlying context should do nothing and return 1.  Note that a
       parameter that is unknown in the underlying context is simply ignored.
       Also, what happens when a needed parameter isn't passed down is defined
       by the implementation.

       EVP_MAC_gettable_params() returns an OSSL_PARAM(3) array that describes
       the retrievable and settable parameters.  EVP_MAC_gettable_params()
       returns parameters that can be used with EVP_MAC_get_params().

       EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params() return
       constant OSSL_PARAM(3) arrays that describe the retrievable parameters
       that can be used with EVP_MAC_CTX_get_params().
       EVP_MAC_gettable_ctx_params() returns the parameters that can be
       retrieved from the algorithm, whereas EVP_MAC_CTX_gettable_params()
       returns the parameters that can be retrieved in the context's current
       state.

       EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return
       constant OSSL_PARAM(3) arrays that describe the settable parameters
       that can be used with EVP_MAC_CTX_set_params().
       EVP_MAC_settable_ctx_params() returns the parameters that can be
       retrieved from the algorithm, whereas EVP_MAC_CTX_settable_params()
       returns the parameters that can be retrieved in the context's current
       state.

   Information functions
       EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given
       context.

       EVP_MAC_CTX_get_block_size() returns the MAC block size for the given
       context.  Not all MAC algorithms support this.

       EVP_MAC_is_a() checks if the given mac is an implementation of an
       algorithm that's identifiable with name.

       EVP_MAC_get0_provider() returns the provider that holds the
       implementation of the given mac.

       EVP_MAC_do_all_provided() traverses all MAC implemented by all
       activated providers in the given library context libctx, and for each
       of the implementations, calls the given function fn with the
       implementation method and the given arg as argument.

       EVP_MAC_get0_name() return the name of the given MAC.  For fetched MACs
       with multiple names, only one of them is returned; it's recommended to
       use EVP_MAC_names_do_all() instead.

       EVP_MAC_names_do_all() traverses all names for mac, and calls fn with
       each name and data.

       EVP_MAC_get0_description() returns a description of the mac, meant for
       display and human consumption.  The description is at the discretion of
       the mac implementation.


PARAMETERS

       Parameters are identified by name as strings, and have an expected data
       type and maximum size.  OpenSSL has a set of macros for parameter names
       it expects to see in its own MAC implementations.  Here, we show all
       three, the OpenSSL macro for the parameter name, the name in string
       form, and a type description.

       The standard parameter names are:

       "key" (OSSL_MAC_PARAM_KEY) <octet string>
           Its value is the MAC key as an array of bytes.

           For MACs that use an underlying computation algorithm, the
           algorithm must be set first, see parameter names "algorithm" below.

       "iv" (OSSL_MAC_PARAM_IV) <octet string>
           Some MAC implementations (GMAC) require an IV, this parameter sets
           the IV.

       "custom" (OSSL_MAC_PARAM_CUSTOM) <octet string>
           Some MAC implementations (KMAC, BLAKE2) accept a Customization
           String, this parameter sets the Customization String. The default
           value is the empty string.

       "salt" (OSSL_MAC_PARAM_SALT) <octet string>
           This option is used by BLAKE2 MAC.

       "xof" (OSSL_MAC_PARAM_XOF) <integer>
           It's a simple flag, the value 0 or 1 are expected.

           This option is used by KMAC.

       "digest-noinit" (OSSL_MAC_PARAM_DIGEST_NOINIT) <integer>
           A simple flag to set the MAC digest to not initialise the
           implementation specific data. The value 0 or 1 is expected.

           This option is deprecated and will be removed in a future release.
           The option may be set, but is ignored.

       "digest-oneshot" (OSSL_MAC_PARAM_DIGEST_ONESHOT) <integer>
           A simple flag to set the MAC digest to be a oneshot operation.  The
           value 0 or 1 is expected.

           This option is deprecated and will be removed in a future release.
           The option may be set, but is ignored.

       "properties" (OSSL_MAC_PARAM_PROPERTIES) <UTF8 string>
       "digest" (OSSL_MAC_PARAM_DIGEST) <UTF8 string>
       "cipher" (OSSL_MAC_PARAM_CIPHER) <UTF8 string>
           For MAC implementations that use an underlying computation cipher
           or digest, these parameters set what the algorithm should be.

           The value is always the name of the intended algorithm, or the
           properties.

           Note that not all algorithms may support all digests.  HMAC does
           not support variable output length digests such as SHAKE128 or
           SHAKE256.

       "size" (OSSL_MAC_PARAM_SIZE) <unsigned integer>
           For MAC implementations that support it, set the output size that
           EVP_MAC_final() should produce.  The allowed sizes vary between MAC
           implementations, but must never exceed what can be given with a
           size_t.

       "tls-data-size" (OSSL_MAC_PARAM_TLS_DATA_SIZE) <unsigned integer>
           This parameter is only supported by HMAC. If set then special
           handling is activated for calculating the MAC of a received
           mac-then-encrypt TLS record where variable length record padding
           has been used (as in the case of CBC mode ciphersuites). The value
           represents the total length of the record that is having the MAC
           calculated including the received MAC and the record padding.

           When used EVP_MAC_update must be called precisely twice. The first
           time with the 13 bytes of TLS "header" data, and the second time
           with the entire record including the MAC itself and any padding.
           The entire record length must equal the value passed in the
           "tls-data-size" parameter. The length passed in the datalen
           parameter to EVP_MAC_update() should be equal to the length of the
           record after the MAC and any padding has been removed.

       All these parameters should be used before the calls to any of
       EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
       computation.  Anything else may give undefined results.


NOTES

       The MAC life-cycle is described in life_cycle-mac(7).  In the future,
       the transitions described there will be enforced.  When this is done,
       it will not be considered a breaking change to the API.

       The usage of the parameter names "custom", "iv" and "salt" correspond
       to the names used in the standard where the algorithm was defined.

       Some MAC algorithms store internal state that cannot be extracted
       during re-initalization.  For example GMAC cannot extract an IV from
       the underlying CIPHER context, and so calling EVP_MAC_init() on an
       EVP_MAC object after EVP_MAC_final() has been called cannot reset its
       cipher state to what it was when the IV was initially generated.  For
       such instances, an OSSL_MAC_PARAM_IV parameter must be passed with each
       call to EVP_MAC_init().


RETURN VALUES

       EVP_MAC_fetch() returns a pointer to a newly fetched EVP_MAC, or NULL
       if allocation failed.

       EVP_MAC_up_ref() returns 1 on success, 0 on error.

       EVP_MAC_names_do_all() returns 1 if the callback was called for all
       names. A return value of 0 means that the callback was not called for
       any names.

       EVP_MAC_free() returns nothing at all.

       EVP_MAC_is_a() returns 1 if the given method can be identified with the
       given name, otherwise 0.

       EVP_MAC_get0_name() returns a name of the MAC, or NULL on error.

       EVP_MAC_get0_provider() returns a pointer to the provider for the MAC,
       or NULL on error.

       EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly
       created EVP_MAC_CTX, or NULL if allocation failed.

       EVP_MAC_CTX_free() returns nothing at all.

       EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on
       success, 0 on error.

       EVP_Q_mac() returns a pointer to the computed MAC value, or NULL on
       error.

       EVP_MAC_init(), EVP_MAC_update(), EVP_MAC_final(), and
       EVP_MAC_finalXOF() return 1 on success, 0 on error.

       EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it
       isn't set.  If it isn't set, a call to EVP_MAC_init() will set it.

       EVP_MAC_CTX_get_block_size() returns the block size, or 0 if it isn't
       set.  If it isn't set, a call to EVP_MAC_init() will set it.

       EVP_MAC_do_all_provided() returns nothing at all.


EXAMPLES

         #include <stdlib.h>
         #include <stdio.h>
         #include <string.h>
         #include <stdarg.h>
         #include <unistd.h>

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

         int main() {
             EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
             const char *cipher = getenv("MY_MAC_CIPHER");
             const char *digest = getenv("MY_MAC_DIGEST");
             const char *key = getenv("MY_KEY");
             EVP_MAC_CTX *ctx = NULL;

             unsigned char buf[4096];
             size_t read_l;
             size_t final_l;

             size_t i;

             OSSL_PARAM params[3];
             size_t params_n = 0;

             if (cipher != NULL)
                 params[params_n++] =
                     OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0);
             if (digest != NULL)
                 params[params_n++] =
                     OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0);
             params[params_n] = OSSL_PARAM_construct_end();

             if (mac == NULL
                 || key == NULL
                 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
                 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key),
                                  params))
                 goto err;

             while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
                 if (!EVP_MAC_update(ctx, buf, read_l))
                     goto err;
             }

             if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf)))
                 goto err;

             printf("Result: ");
             for (i = 0; i < final_l; i++)
                 printf("%02X", buf[i]);
             printf("\n");

             EVP_MAC_CTX_free(ctx);
             EVP_MAC_free(mac);
             exit(0);

          err:
             EVP_MAC_CTX_free(ctx);
             EVP_MAC_free(mac);
             fprintf(stderr, "Something went wrong\n");
             ERR_print_errors_fp(stderr);
             exit (1);
         }

       A run of this program, called with correct environment variables, can
       look like this:

         $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
           LD_LIBRARY_PATH=. ./foo < foo.c
         Result: C5C06683CD9DDEF904D754505C560A4E

       (in this example, that program was stored in foo.c and compiled to
       ./foo)


SEE ALSO

       property(7) OSSL_PARAM(3), EVP_MAC-BLAKE2(7), EVP_MAC-CMAC(7),
       EVP_MAC-GMAC(7), EVP_MAC-HMAC(7), EVP_MAC-KMAC(7), EVP_MAC-Siphash(7),
       EVP_MAC-Poly1305(7), provider-mac(7), life_cycle-mac(7)


HISTORY

       These functions were added in OpenSSL 3.0.


COPYRIGHT

       Copyright 2018-2024 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>.

3.3.2                             2024-09-04                    EVP_MAC(3ossl)

openssl 3.3.2 - Generated Thu Sep 12 07:41:16 CDT 2024
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