=pod =head1 NAME EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free, EVP_MAC_is_a, EVP_MAC_number, EVP_MAC_names_do_all, EVP_MAC_provider, EVP_MAC_get_params, EVP_MAC_gettable_params, EVP_MAC_CTX, EVP_MAC_new_ctx, EVP_MAC_free_ctx, EVP_MAC_dup_ctx, EVP_MAC_get_ctx_mac, EVP_MAC_get_ctx_params, EVP_MAC_set_ctx_params, EVP_MAC_size, EVP_MAC_init, EVP_MAC_update, EVP_MAC_final, EVP_MAC_gettable_ctx_params, EVP_MAC_settable_ctx_params, EVP_MAC_do_all_provided - EVP MAC routines =head1 SYNOPSIS #include typedef struct evp_mac_st EVP_MAC; typedef struct evp_mac_ctx_st EVP_MAC_CTX; EVP_MAC *EVP_MAC_fetch(OPENSSL_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); int EVP_MAC_number(const EVP_MAC *mac); void EVP_MAC_names_do_all(const EVP_MAC *mac, void (*fn)(const char *name, void *data), void *data); const OSSL_PROVIDER *EVP_MAC_provider(const EVP_MAC *mac); int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]); EVP_MAC_CTX *EVP_MAC_new_ctx(EVP_MAC *mac); void EVP_MAC_free_ctx(EVP_MAC_CTX *ctx); EVP_MAC_CTX *EVP_MAC_dup_ctx(const EVP_MAC_CTX *src); EVP_MAC *EVP_MAC_get_ctx_mac(EVP_MAC_CTX *ctx); int EVP_MAC_get_ctx_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]); int EVP_MAC_set_ctx_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]); size_t EVP_MAC_size(EVP_MAC_CTX *ctx); int EVP_MAC_init(EVP_MAC_CTX *ctx); 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); 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); void EVP_MAC_do_all_provided(OPENSSL_CTX *libctx, void (*fn)(EVP_MAC *mac, void *arg), void *arg); =head1 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. =head2 Types B is a type that holds the implementation of a MAC. B 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. =head2 Algorithm implementation fetching EVP_MAC_fetch() fetches an implementation of a MAC I, given a library context I and a set of I. See L for further information. See L for the list of algorithms supported by the default provider. The returned value must eventually be freed with L. 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. =head2 Context manipulation functions EVP_MAC_new_ctx() creates a new context for the MAC type I. The created context can then be used with most other functions described here. EVP_MAC_free_ctx() 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_dup_ctx() duplicates the I context and returns a newly allocated context. EVP_MAC_get_ctx_mac() returns the B associated with the context I. =head2 Computing functions EVP_MAC_init() sets up the underlying context with information given through diverse controls. This should be called before calling EVP_MAC_update() and EVP_MAC_final(). EVP_MAC_update() adds I bytes from I to the MAC input. EVP_MAC_final() does the final computation and stores the result in the memory pointed at by I of size I, and sets the number of bytes written in I<*outl> at. If I is NULL or I 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 I being NULL and I pointing at a valid location, then allocate space and make a second call with I pointing at the allocated space. EVP_MAC_get_params() retrieves details about the implementation I. The set of parameters given with I determine exactly what parameters should be retrieved. Note that a parameter that is unknown in the underlying context is simply ignored. EVP_MAC_get_ctx_params() retrieves chosen parameters, given the context I and its underlying context. The set of parameters given with I determine exactly what parameters should be retrieved. Note that a parameter that is unknown in the underlying context is simply ignored. EVP_MAC_set_ctx_params() passes chosen parameters to the underlying context, given a context I. The set of parameters given with I determine exactly what parameters are passed down. 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(), EVP_MAC_gettable_ctx_params() and EVP_MAC_settable_ctx_params() get a constant B array that describes the retrievable and settable parameters, i.e. parameters that can be used with EVP_MAC_get_params(), EVP_MAC_get_ctx_params() and EVP_MAC_set_ctx_params(), respectively. See L for the use of B as parameter descriptor. =head2 Information functions EVP_MAC_size() returns the MAC output size for the given context. EVP_MAC_is_a() checks if the given I is an implementation of an algorithm that's identifiable with I. EVP_MAC_provider() returns the provider that holds the implementation of the given I. EVP_MAC_do_all_provided() traverses all MAC implemented by all activated providers in the given library context I, and for each of the implementations, calls the given function I with the implementation method and the given I as argument. EVP_MAC_number() returns the internal dynamic number assigned to I. EVP_MAC_names_do_all() traverses all names for I, and calls I with each name and I. =head1 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: =over 4 =item "key" (B) 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. =item "iv" (B) Some MAC implementations require an IV, this parameter sets the IV. =item "custom" (B) Some MAC implementations (KMAC, BLAKE2) accept a Customization String, this parameter sets the Customization String. The default value is the empty string. =item "salt" (B) This option is used by BLAKE2 MAC. =item "xof" (B) It's a simple flag, the value 0 or 1 are expected. This option is used by KMAC. =item "flags" (B) These will set the MAC flags to the given numbers. Some MACs do not support this option. =item "properties" (B) =item "digest" (B) =item "cipher" (B) 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. =item "size" (B) 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 B. =back 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. =head1 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_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_provider() returns a pointer to the provider for the MAC, or NULL on error. EVP_MAC_new_ctx() and EVP_MAC_dup_ctx() return a pointer to a newly created EVP_MAC_CTX, or NULL if allocation failed. EVP_MAC_free_ctx() returns nothing at all. EVP_MAC_get_ctx_params() and EVP_MAC_set_ctx_params() return 1 on success, 0 on error. EVP_MAC_init(), EVP_MAC_update(), and EVP_MAC_final() return 1 on success, 0 on error. EVP_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() should get it set. EVP_MAC_do_all_provided() returns nothing at all. =head1 EXAMPLES #include #include #include #include #include #include #include #include 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]; ssize_t read_l; size_t final_l; size_t i; OSSL_PARAM params[4]; size_t params_n = 0; if (cipher != NULL) params[params_n++] = OSSL_PARAM_construct_utf8_string("cipher", cipher, 0, NULL); if (digest != NULL) params[params_n++] = OSSL_PARAM_construct_utf8_string("digest", digest, 0, NULL); params[params_n++] = OSSL_PARAM_construct_octet_string("key", key, strlen(key), NULL); params[params_n] = OSSL_PARAM_construct_end(); if (mac == NULL || key == NULL || (ctx = EVP_MAC_new_ctx(mac)) == NULL || EVP_MAC_set_ctx_params(ctx, params) <= 0) goto err; if (!EVP_MAC_init(ctx)) 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)) goto err; printf("Result: "); for (i = 0; i < final_l; i++) printf("%02X", buf[i]); printf("\n"); EVP_MAC_free_ctx(ctx); EVP_MAC_free(mac); exit(0); err: EVP_MAC_free_ctx(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 F and compiled to F<./foo>) =head1 SEE ALSO L L, L, L, L, L, L, L, L =head1 HISTORY These functions were added in OpenSSL 3.0. =head1 COPYRIGHT Copyright 2018-2020 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 L. =cut