.\" Automatically generated by Pod::Man 4.14 (Pod::Simple 3.42) .\" .\" Standard preamble: .\" ======================================================================== .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. \*(C+ will .\" give a nicer C++. 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No user-serviceable parts. . \" fudge factors for nroff and troff .if n \{\ . ds #H 0 . ds #V .8m . ds #F .3m . ds #[ \f1 . ds #] \fP .\} .if t \{\ . ds #H ((1u-(\\\\n(.fu%2u))*.13m) . ds #V .6m . ds #F 0 . ds #[ \& . ds #] \& .\} . \" simple accents for nroff and troff .if n \{\ . ds ' \& . ds ` \& . ds ^ \& . ds , \& . ds ~ ~ . ds / .\} .if t \{\ . ds ' \\k:\h'-(\\n(.wu*8/10-\*(#H)'\'\h"|\\n:u" . ds ` \\k:\h'-(\\n(.wu*8/10-\*(#H)'\`\h'|\\n:u' . ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'^\h'|\\n:u' . ds , \\k:\h'-(\\n(.wu*8/10)',\h'|\\n:u' . ds ~ \\k:\h'-(\\n(.wu-\*(#H-.1m)'~\h'|\\n:u' . ds / \\k:\h'-(\\n(.wu*8/10-\*(#H)'\z\(sl\h'|\\n:u' .\} . \" troff and (daisy-wheel) nroff accents .ds : \\k:\h'-(\\n(.wu*8/10-\*(#H+.1m+\*(#F)'\v'-\*(#V'\z.\h'.2m+\*(#F'.\h'|\\n:u'\v'\*(#V' .ds 8 \h'\*(#H'\(*b\h'-\*(#H' .ds o \\k:\h'-(\\n(.wu+\w'\(de'u-\*(#H)/2u'\v'-.3n'\*(#[\z\(de\v'.3n'\h'|\\n:u'\*(#] .ds d- \h'\*(#H'\(pd\h'-\w'~'u'\v'-.25m'\f2\(hy\fP\v'.25m'\h'-\*(#H' .ds D- D\\k:\h'-\w'D'u'\v'-.11m'\z\(hy\v'.11m'\h'|\\n:u' .ds th \*(#[\v'.3m'\s+1I\s-1\v'-.3m'\h'-(\w'I'u*2/3)'\s-1o\s+1\*(#] .ds Th \*(#[\s+2I\s-2\h'-\w'I'u*3/5'\v'-.3m'o\v'.3m'\*(#] .ds ae a\h'-(\w'a'u*4/10)'e .ds Ae A\h'-(\w'A'u*4/10)'E . \" corrections for vroff .if v .ds ~ \\k:\h'-(\\n(.wu*9/10-\*(#H)'\s-2\u~\d\s+2\h'|\\n:u' .if v .ds ^ \\k:\h'-(\\n(.wu*10/11-\*(#H)'\v'-.4m'^\v'.4m'\h'|\\n:u' . \" for low resolution devices (crt and lpr) .if \n(.H>23 .if \n(.V>19 \ \{\ . ds : e . ds 8 ss . ds o a . ds d- d\h'-1'\(ga . ds D- D\h'-1'\(hy . ds th \o'bp' . ds Th \o'LP' . ds ae ae . ds Ae AE .\} .rm #[ #] #H #V #F C .\" ======================================================================== .\" .IX Title "EVP_MAC 3ossl" .TH EVP_MAC 3ossl "2023-09-19" "3.0.11" "OpenSSL" .\" For nroff, turn off justification. Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "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 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #include \& \& 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); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" These types and functions help the application to calculate MACs of different types and with different underlying algorithms if there are any. .PP MACs are a bit complex insofar that some of them use other algorithms for actual computation. \s-1HMAC\s0 uses a digest, and \s-1CMAC\s0 uses a cipher. Therefore, there are sometimes two contexts to keep track of, one for the \s-1MAC\s0 algorithm itself and one for the underlying computation algorithm if there is one. .PP To make things less ambiguous, this manual talks about a \*(L"context\*(R" or \&\*(L"\s-1MAC\s0 context\*(R", which is to denote the \s-1MAC\s0 level context, and about a \&\*(L"underlying context\*(R", or \*(L"computation context\*(R", which is to denote the context for the underlying computation algorithm if there is one. .SS "Types" .IX Subsection "Types" \&\fB\s-1EVP_MAC\s0\fR is a type that holds the implementation of a \s-1MAC.\s0 .PP \&\fB\s-1EVP_MAC_CTX\s0\fR is a context type that holds internal \s-1MAC\s0 information as well as a reference to a computation context, for those MACs that rely on an underlying computation algorithm. .SS "Algorithm implementation fetching" .IX Subsection "Algorithm implementation fetching" \&\fBEVP_MAC_fetch()\fR fetches an implementation of a \s-1MAC\s0 \fIalgorithm\fR, given a library context \fIlibctx\fR and a set of \fIproperties\fR. See \*(L"\s-1ALGORITHM FETCHING\*(R"\s0 in \fBcrypto\fR\|(7) for further information. .PP See \*(L"Message Authentication Code (\s-1MAC\s0)\*(R" in \fBOSSL_PROVIDER\-default\fR\|(7) for the list of algorithms supported by the default provider. .PP The returned value must eventually be freed with \&\fBEVP_MAC_free\fR\|(3). .PP \&\fBEVP_MAC_up_ref()\fR increments the reference count of an already fetched \&\s-1MAC.\s0 .PP \&\fBEVP_MAC_free()\fR frees a fetched algorithm. \&\s-1NULL\s0 is a valid parameter, for which this function is a no-op. .SS "Context manipulation functions" .IX Subsection "Context manipulation functions" \&\fBEVP_MAC_CTX_new()\fR creates a new context for the \s-1MAC\s0 type \fImac\fR. The created context can then be used with most other functions described here. .PP \&\fBEVP_MAC_CTX_free()\fR frees the contents of the context, including an underlying context if there is one, as well as the context itself. \&\s-1NULL\s0 is a valid parameter, for which this function is a no-op. .PP \&\fBEVP_MAC_CTX_dup()\fR duplicates the \fIsrc\fR context and returns a newly allocated context. .PP \&\fBEVP_MAC_CTX_get0_mac()\fR returns the \fB\s-1EVP_MAC\s0\fR associated with the context \&\fIctx\fR. .SS "Computing functions" .IX Subsection "Computing functions" \&\fBEVP_Q_mac()\fR computes the message authentication code of \fIdata\fR with length \fIdatalen\fR using the \s-1MAC\s0 algorithm \fIname\fR and the key \fIkey\fR with length \fIkeylen\fR. The \s-1MAC\s0 algorithm is fetched using any given \fIlibctx\fR and property query string \fIpropq\fR. It takes parameters \fIsubalg\fR and further \fIparams\fR, both of which may be \s-1NULL\s0 if not needed. If \fIout\fR is not \s-1NULL,\s0 it places the result in the memory pointed at by \fIout\fR, but only if \fIoutsize\fR is sufficient (otherwise no computation is made). If \fIout\fR is \s-1NULL,\s0 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 \fI*outlen\fR unless \fIoutlen\fR is \s-1NULL.\s0 .PP \&\fBEVP_MAC_init()\fR sets up the underlying context \fIctx\fR with information given via the \fIkey\fR and \fIparams\fR arguments. The \s-1MAC\s0 \fIkey\fR has a length of \&\fIkeylen\fR and the parameters in \fIparams\fR are processed before setting the key. If \fIkey\fR is \s-1NULL,\s0 the key must be set via \fIparams\fR either as part of this call or separately using \fBEVP_MAC_CTX_set_params()\fR. Providing non-NULL \fIparams\fR to this function is equivalent to calling \&\fBEVP_MAC_CTX_set_params()\fR with those \fIparams\fR for the same \fIctx\fR beforehand. .PP \&\fBEVP_MAC_init()\fR should be called before \fBEVP_MAC_update()\fR and \fBEVP_MAC_final()\fR. .PP \&\fBEVP_MAC_update()\fR adds \fIdatalen\fR bytes from \fIdata\fR to the \s-1MAC\s0 input. .PP \&\fBEVP_MAC_final()\fR does the final computation and stores the result in the memory pointed at by \fIout\fR of size \fIoutsize\fR, and sets the number of bytes written in \fI*outl\fR at. If \fIout\fR is \s-1NULL\s0 or \fIoutsize\fR 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 \fIout\fR being \s-1NULL\s0 and \fIoutl\fR pointing at a valid location, then allocate space and make a second call with \fIout\fR pointing at the allocated space. .PP \&\fBEVP_MAC_finalXOF()\fR does the final computation for an \s-1XOF\s0 based \s-1MAC\s0 and stores the result in the memory pointed at by \fIout\fR of size \fIoutsize\fR. .PP \&\fBEVP_MAC_get_params()\fR retrieves details about the implementation \&\fImac\fR. The set of parameters given with \fIparams\fR determine exactly what parameters should be retrieved. Note that a parameter that is unknown in the underlying context is simply ignored. .PP \&\fBEVP_MAC_CTX_get_params()\fR retrieves chosen parameters, given the context \fIctx\fR and its underlying context. The set of parameters given with \fIparams\fR determine exactly what parameters should be retrieved. Note that a parameter that is unknown in the underlying context is simply ignored. .PP \&\fBEVP_MAC_CTX_set_params()\fR passes chosen parameters to the underlying context, given a context \fIctx\fR. The set of parameters given with \fIparams\fR determine exactly what parameters are passed down. If \fIparams\fR are \s-1NULL,\s0 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. .PP \&\fBEVP_MAC_gettable_params()\fR returns an \s-1\fBOSSL_PARAM\s0\fR\|(3) array that describes the retrievable and settable parameters. \fBEVP_MAC_gettable_params()\fR returns parameters that can be used with \fBEVP_MAC_get_params()\fR. .PP \&\fBEVP_MAC_gettable_ctx_params()\fR and \fBEVP_MAC_CTX_gettable_params()\fR return constant \s-1\fBOSSL_PARAM\s0\fR\|(3) arrays that describe the retrievable parameters that can be used with \fBEVP_MAC_CTX_get_params()\fR. \&\fBEVP_MAC_gettable_ctx_params()\fR returns the parameters that can be retrieved from the algorithm, whereas \fBEVP_MAC_CTX_gettable_params()\fR returns the parameters that can be retrieved in the context's current state. .PP \&\fBEVP_MAC_settable_ctx_params()\fR and \fBEVP_MAC_CTX_settable_params()\fR return constant \s-1\fBOSSL_PARAM\s0\fR\|(3) arrays that describe the settable parameters that can be used with \fBEVP_MAC_CTX_set_params()\fR. \fBEVP_MAC_settable_ctx_params()\fR returns the parameters that can be retrieved from the algorithm, whereas \fBEVP_MAC_CTX_settable_params()\fR returns the parameters that can be retrieved in the context's current state. .SS "Information functions" .IX Subsection "Information functions" \&\fBEVP_MAC_CTX_get_mac_size()\fR returns the \s-1MAC\s0 output size for the given context. .PP \&\fBEVP_MAC_CTX_get_block_size()\fR returns the \s-1MAC\s0 block size for the given context. Not all \s-1MAC\s0 algorithms support this. .PP \&\fBEVP_MAC_is_a()\fR checks if the given \fImac\fR is an implementation of an algorithm that's identifiable with \fIname\fR. .PP \&\fBEVP_MAC_get0_provider()\fR returns the provider that holds the implementation of the given \fImac\fR. .PP \&\fBEVP_MAC_do_all_provided()\fR traverses all \s-1MAC\s0 implemented by all activated providers in the given library context \fIlibctx\fR, and for each of the implementations, calls the given function \fIfn\fR with the implementation method and the given \fIarg\fR as argument. .PP \&\fBEVP_MAC_get0_name()\fR return the name of the given \s-1MAC.\s0 For fetched MACs with multiple names, only one of them is returned; it's recommended to use \fBEVP_MAC_names_do_all()\fR instead. .PP \&\fBEVP_MAC_names_do_all()\fR traverses all names for \fImac\fR, and calls \&\fIfn\fR with each name and \fIdata\fR. .PP \&\fBEVP_MAC_get0_description()\fR returns a description of the \fImac\fR, meant for display and human consumption. The description is at the discretion of the mac implementation. .SH "PARAMETERS" .IX Header "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 \s-1MAC\s0 implementations. Here, we show all three, the OpenSSL macro for the parameter name, the name in string form, and a type description. .PP The standard parameter names are: .ie n .IP """key"" (\fB\s-1OSSL_MAC_PARAM_KEY\s0\fR) " 4 .el .IP "``key'' (\fB\s-1OSSL_MAC_PARAM_KEY\s0\fR) " 4 .IX Item "key (OSSL_MAC_PARAM_KEY) " Its value is the \s-1MAC\s0 key as an array of bytes. .Sp For MACs that use an underlying computation algorithm, the algorithm must be set first, see parameter names \*(L"algorithm\*(R" below. .ie n .IP """iv"" (\fB\s-1OSSL_MAC_PARAM_IV\s0\fR) " 4 .el .IP "``iv'' (\fB\s-1OSSL_MAC_PARAM_IV\s0\fR) " 4 .IX Item "iv (OSSL_MAC_PARAM_IV) " Some \s-1MAC\s0 implementations (\s-1GMAC\s0) require an \s-1IV,\s0 this parameter sets the \s-1IV.\s0 .ie n .IP """custom"" (\fB\s-1OSSL_MAC_PARAM_CUSTOM\s0\fR) " 4 .el .IP "``custom'' (\fB\s-1OSSL_MAC_PARAM_CUSTOM\s0\fR) " 4 .IX Item "custom (OSSL_MAC_PARAM_CUSTOM) " Some \s-1MAC\s0 implementations (\s-1KMAC, BLAKE2\s0) accept a Customization String, this parameter sets the Customization String. The default value is the empty string. .ie n .IP """salt"" (\fB\s-1OSSL_MAC_PARAM_SALT\s0\fR) " 4 .el .IP "``salt'' (\fB\s-1OSSL_MAC_PARAM_SALT\s0\fR) " 4 .IX Item "salt (OSSL_MAC_PARAM_SALT) " This option is used by \s-1BLAKE2 MAC.\s0 .ie n .IP """xof"" (\fB\s-1OSSL_MAC_PARAM_XOF\s0\fR) " 4 .el .IP "``xof'' (\fB\s-1OSSL_MAC_PARAM_XOF\s0\fR) " 4 .IX Item "xof (OSSL_MAC_PARAM_XOF) " It's a simple flag, the value 0 or 1 are expected. .Sp This option is used by \s-1KMAC.\s0 .ie n .IP """digest-noinit"" (\fB\s-1OSSL_MAC_PARAM_DIGEST_NOINIT\s0\fR) " 4 .el .IP "``digest-noinit'' (\fB\s-1OSSL_MAC_PARAM_DIGEST_NOINIT\s0\fR) " 4 .IX Item "digest-noinit (OSSL_MAC_PARAM_DIGEST_NOINIT) " A simple flag to set the \s-1MAC\s0 digest to not initialise the implementation specific data. The value 0 or 1 is expected. .Sp This option is used by \s-1HMAC.\s0 .ie n .IP """digest-oneshot"" (\fB\s-1OSSL_MAC_PARAM_DIGEST_ONESHOT\s0\fR) " 4 .el .IP "``digest-oneshot'' (\fB\s-1OSSL_MAC_PARAM_DIGEST_ONESHOT\s0\fR) " 4 .IX Item "digest-oneshot (OSSL_MAC_PARAM_DIGEST_ONESHOT) " A simple flag to set the \s-1MAC\s0 digest to be a oneshot operation. The value 0 or 1 is expected. .Sp This option is used by \s-1HMAC.\s0 .ie n .IP """properties"" (\fB\s-1OSSL_MAC_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``properties'' (\fB\s-1OSSL_MAC_PARAM_PROPERTIES\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "properties (OSSL_MAC_PARAM_PROPERTIES) " .PD 0 .ie n .IP """digest"" (\fB\s-1OSSL_MAC_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``digest'' (\fB\s-1OSSL_MAC_PARAM_DIGEST\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "digest (OSSL_MAC_PARAM_DIGEST) " .ie n .IP """cipher"" (\fB\s-1OSSL_MAC_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4 .el .IP "``cipher'' (\fB\s-1OSSL_MAC_PARAM_CIPHER\s0\fR) <\s-1UTF8\s0 string>" 4 .IX Item "cipher (OSSL_MAC_PARAM_CIPHER) " .PD For \s-1MAC\s0 implementations that use an underlying computation cipher or digest, these parameters set what the algorithm should be. .Sp The value is always the name of the intended algorithm, or the properties. .Sp Note that not all algorithms may support all digests. \&\s-1HMAC\s0 does not support variable output length digests such as \s-1SHAKE128\s0 or \s-1SHAKE256.\s0 .ie n .IP """size"" (\fB\s-1OSSL_MAC_PARAM_SIZE\s0\fR) " 4 .el .IP "``size'' (\fB\s-1OSSL_MAC_PARAM_SIZE\s0\fR) " 4 .IX Item "size (OSSL_MAC_PARAM_SIZE) " For \s-1MAC\s0 implementations that support it, set the output size that \&\fBEVP_MAC_final()\fR should produce. The allowed sizes vary between \s-1MAC\s0 implementations, but must never exceed what can be given with a \fBsize_t\fR. .ie n .IP """tls-data-size"" (\fB\s-1OSSL_MAC_PARAM_TLS_DATA_SIZE\s0\fR) " 4 .el .IP "``tls-data-size'' (\fB\s-1OSSL_MAC_PARAM_TLS_DATA_SIZE\s0\fR) " 4 .IX Item "tls-data-size (OSSL_MAC_PARAM_TLS_DATA_SIZE) " This parameter is only supported by \s-1HMAC.\s0 If set then special handling is activated for calculating the \s-1MAC\s0 of a received mac-then-encrypt \s-1TLS\s0 record where variable length record padding has been used (as in the case of \s-1CBC\s0 mode ciphersuites). The value represents the total length of the record that is having the \s-1MAC\s0 calculated including the received \s-1MAC\s0 and the record padding. .Sp When used EVP_MAC_update must be called precisely twice. The first time with the 13 bytes of \s-1TLS\s0 \*(L"header\*(R" data, and the second time with the entire record including the \s-1MAC\s0 itself and any padding. The entire record length must equal the value passed in the \*(L"tls-data-size\*(R" parameter. The length passed in the \&\fBdatalen\fR parameter to \fBEVP_MAC_update()\fR should be equal to the length of the record after the \s-1MAC\s0 and any padding has been removed. .PP All these parameters should be used before the calls to any of \&\fBEVP_MAC_init()\fR, \fBEVP_MAC_update()\fR and \fBEVP_MAC_final()\fR for a full computation. Anything else may give undefined results. .SH "NOTES" .IX Header "NOTES" The \s-1MAC\s0 life-cycle is described in \fBlife_cycle\-mac\fR\|(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 \s-1API.\s0 .PP The usage of the parameter names \*(L"custom\*(R", \*(L"iv\*(R" and \*(L"salt\*(R" correspond to the names used in the standard where the algorithm was defined. .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBEVP_MAC_fetch()\fR returns a pointer to a newly fetched \fB\s-1EVP_MAC\s0\fR, or \&\s-1NULL\s0 if allocation failed. .PP \&\fBEVP_MAC_up_ref()\fR returns 1 on success, 0 on error. .PP \&\fBEVP_MAC_names_do_all()\fR 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. .PP \&\fBEVP_MAC_free()\fR returns nothing at all. .PP \&\fBEVP_MAC_is_a()\fR returns 1 if the given method can be identified with the given name, otherwise 0. .PP \&\fBEVP_MAC_get0_name()\fR returns a name of the \s-1MAC,\s0 or \s-1NULL\s0 on error. .PP \&\fBEVP_MAC_get0_provider()\fR returns a pointer to the provider for the \s-1MAC,\s0 or \&\s-1NULL\s0 on error. .PP \&\fBEVP_MAC_CTX_new()\fR and \fBEVP_MAC_CTX_dup()\fR return a pointer to a newly created \s-1EVP_MAC_CTX,\s0 or \s-1NULL\s0 if allocation failed. .PP \&\fBEVP_MAC_CTX_free()\fR returns nothing at all. .PP \&\fBEVP_MAC_CTX_get_params()\fR and \fBEVP_MAC_CTX_set_params()\fR return 1 on success, 0 on error. .PP \&\fBEVP_Q_mac()\fR returns a pointer to the computed \s-1MAC\s0 value, or \s-1NULL\s0 on error. .PP \&\fBEVP_MAC_init()\fR, \fBEVP_MAC_update()\fR, \fBEVP_MAC_final()\fR, and \fBEVP_MAC_finalXOF()\fR return 1 on success, 0 on error. .PP \&\fBEVP_MAC_CTX_get_mac_size()\fR returns the expected output size, or 0 if it isn't set. If it isn't set, a call to \fBEVP_MAC_init()\fR will set it. .PP \&\fBEVP_MAC_CTX_get_block_size()\fR returns the block size, or 0 if it isn't set. If it isn't set, a call to \fBEVP_MAC_init()\fR will set it. .PP \&\fBEVP_MAC_do_all_provided()\fR returns nothing at all. .SH "EXAMPLES" .IX Header "EXAMPLES" .Vb 5 \& #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]; \& 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("\en"); \& \& 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\en"); \& ERR_print_errors_fp(stderr); \& exit (1); \& } .Ve .PP A run of this program, called with correct environment variables, can look like this: .PP .Vb 3 \& $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes\-128\-cbc \e \& LD_LIBRARY_PATH=. ./foo < foo.c \& Result: C5C06683CD9DDEF904D754505C560A4E .Ve .PP (in this example, that program was stored in \fIfoo.c\fR and compiled to \&\fI./foo\fR) .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBproperty\fR\|(7) \&\s-1\fBOSSL_PARAM\s0\fR\|(3), \&\s-1\fBEVP_MAC\-BLAKE2\s0\fR\|(7), \&\s-1\fBEVP_MAC\-CMAC\s0\fR\|(7), \&\s-1\fBEVP_MAC\-GMAC\s0\fR\|(7), \&\s-1\fBEVP_MAC\-HMAC\s0\fR\|(7), \&\s-1\fBEVP_MAC\-KMAC\s0\fR\|(7), \&\fBEVP_MAC\-Siphash\fR\|(7), \&\fBEVP_MAC\-Poly1305\fR\|(7), \&\fBprovider\-mac\fR\|(7), \&\fBlife_cycle\-mac\fR\|(7) .SH "HISTORY" .IX Header "HISTORY" These functions were added in OpenSSL 3.0. .SH "COPYRIGHT" .IX Header "COPYRIGHT" Copyright 2018\-2023 The OpenSSL Project Authors. All Rights Reserved. .PP Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at .