5 EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free,
6 EVP_MAC_is_a, EVP_MAC_number, EVP_MAC_name, EVP_MAC_names_do_all,
7 EVP_MAC_provider, EVP_MAC_get_params, EVP_MAC_gettable_params,
8 EVP_MAC_CTX, EVP_MAC_CTX_new, EVP_MAC_CTX_free, EVP_MAC_CTX_dup,
9 EVP_MAC_CTX_mac, EVP_MAC_CTX_get_params, EVP_MAC_CTX_set_params,
10 EVP_MAC_CTX_get_mac_size, EVP_MAC_init, EVP_MAC_update, EVP_MAC_final,
11 EVP_MAC_gettable_ctx_params, EVP_MAC_settable_ctx_params,
12 EVP_MAC_do_all_provided - EVP MAC routines
16 #include <openssl/evp.h>
18 typedef struct evp_mac_st EVP_MAC;
19 typedef struct evp_mac_ctx_st EVP_MAC_CTX;
21 EVP_MAC *EVP_MAC_fetch(OSSL_LIB_CTX *libctx, const char *algorithm,
22 const char *properties);
23 int EVP_MAC_up_ref(EVP_MAC *mac);
24 void EVP_MAC_free(EVP_MAC *mac);
25 int EVP_MAC_is_a(const EVP_MAC *mac, const char *name);
26 int EVP_MAC_number(const EVP_MAC *mac);
27 const char *EVP_MAC_name(const EVP_MAC *mac);
28 void EVP_MAC_names_do_all(const EVP_MAC *mac,
29 void (*fn)(const char *name, void *data),
31 const OSSL_PROVIDER *EVP_MAC_provider(const EVP_MAC *mac);
32 int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]);
34 EVP_MAC_CTX *EVP_MAC_CTX_new(EVP_MAC *mac);
35 void EVP_MAC_CTX_free(EVP_MAC_CTX *ctx);
36 EVP_MAC_CTX *EVP_MAC_CTX_dup(const EVP_MAC_CTX *src);
37 EVP_MAC *EVP_MAC_CTX_mac(EVP_MAC_CTX *ctx);
38 int EVP_MAC_CTX_get_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]);
39 int EVP_MAC_CTX_set_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]);
41 size_t EVP_MAC_CTX_get_mac_size(EVP_MAC_CTX *ctx);
42 int EVP_MAC_init(EVP_MAC_CTX *ctx);
43 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
44 int EVP_MAC_final(EVP_MAC_CTX *ctx,
45 unsigned char *out, size_t *outl, size_t outsize);
47 const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
48 const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
49 const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
51 void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx,
52 void (*fn)(EVP_MAC *mac, void *arg),
57 These types and functions help the application to calculate MACs of
58 different types and with different underlying algorithms if there are
61 MACs are a bit complex insofar that some of them use other algorithms
62 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
63 Therefore, there are sometimes two contexts to keep track of, one for
64 the MAC algorithm itself and one for the underlying computation
65 algorithm if there is one.
67 To make things less ambiguous, this manual talks about a "context" or
68 "MAC context", which is to denote the MAC level context, and about a
69 "underlying context", or "computation context", which is to denote the
70 context for the underlying computation algorithm if there is one.
74 B<EVP_MAC> is a type that holds the implementation of a MAC.
76 B<EVP_MAC_CTX> is a context type that holds internal MAC information
77 as well as a reference to a computation context, for those MACs that
78 rely on an underlying computation algorithm.
80 =head2 Algorithm implementation fetching
82 EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given
83 a library context I<libctx> and a set of I<properties>.
84 See L<provider(7)/Fetching algorithms> for further information.
86 See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list
87 of algorithms supported by the default provider.
89 The returned value must eventually be freed with
92 EVP_MAC_up_ref() increments the reference count of an already fetched
95 EVP_MAC_free() frees a fetched algorithm.
96 NULL is a valid parameter, for which this function is a no-op.
98 =head2 Context manipulation functions
100 EVP_MAC_CTX_new() creates a new context for the MAC type I<mac>.
101 The created context can then be used with most other functions
104 EVP_MAC_CTX_free() frees the contents of the context, including an
105 underlying context if there is one, as well as the context itself.
106 NULL is a valid parameter, for which this function is a no-op.
108 EVP_MAC_CTX_dup() duplicates the I<src> context and returns a newly allocated
111 EVP_MAC_CTX_mac() returns the B<EVP_MAC> associated with the context
114 =head2 Computing functions
116 EVP_MAC_init() sets up the underlying context with information given
117 through diverse controls.
118 This should be called before calling EVP_MAC_update() and
121 EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input.
123 EVP_MAC_final() does the final computation and stores the result in
124 the memory pointed at by I<out> of size I<outsize>, and sets the number
125 of bytes written in I<*outl> at.
126 If I<out> is NULL or I<outsize> is too small, then no computation
128 To figure out what the output length will be and allocate space for it
129 dynamically, simply call with I<out> being NULL and I<outl>
130 pointing at a valid location, then allocate space and make a second
131 call with I<out> pointing at the allocated space.
133 EVP_MAC_get_params() retrieves details about the implementation
135 The set of parameters given with I<params> determine exactly what
136 parameters should be retrieved.
137 Note that a parameter that is unknown in the underlying context is
140 EVP_MAC_CTX_get_params() retrieves chosen parameters, given the
141 context I<ctx> and its underlying context.
142 The set of parameters given with I<params> determine exactly what
143 parameters should be retrieved.
144 Note that a parameter that is unknown in the underlying context is
147 EVP_MAC_CTX_set_params() passes chosen parameters to the underlying
148 context, given a context I<ctx>.
149 The set of parameters given with I<params> determine exactly what
150 parameters are passed down.
151 Note that a parameter that is unknown in the underlying context is
153 Also, what happens when a needed parameter isn't passed down is
154 defined by the implementation.
156 EVP_MAC_gettable_params(), EVP_MAC_gettable_ctx_params() and
157 EVP_MAC_settable_ctx_params() get a constant B<OSSL_PARAM> array that
158 describes the retrievable and settable parameters, i.e. parameters that
159 can be used with EVP_MAC_get_params(), EVP_MAC_CTX_get_params()
160 and EVP_MAC_CTX_set_params(), respectively.
161 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
163 =head2 Information functions
165 EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context.
167 EVP_MAC_is_a() checks if the given I<mac> is an implementation of an
168 algorithm that's identifiable with I<name>.
170 EVP_MAC_provider() returns the provider that holds the implementation
173 EVP_MAC_do_all_provided() traverses all MAC implemented by all activated
174 providers in the given library context I<libctx>, and for each of the
175 implementations, calls the given function I<fn> with the implementation method
176 and the given I<arg> as argument.
178 EVP_MAC_number() returns the internal dynamic number assigned to
181 EVP_MAC_name() return the name of the given MAC. For fetched MACs
182 with multiple names, only one of them is returned; it's
183 recommended to use EVP_MAC_names_do_all() instead.
185 EVP_MAC_names_do_all() traverses all names for I<mac>, and calls
186 I<fn> with each name and I<data>.
190 Parameters are identified by name as strings, and have an expected
191 data type and maximum size.
192 OpenSSL has a set of macros for parameter names it expects to see in
193 its own MAC implementations.
194 Here, we show all three, the OpenSSL macro for the parameter name, the
195 name in string form, and a type description.
197 The standard parameter names are:
201 =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
203 Its value is the MAC key as an array of bytes.
205 For MACs that use an underlying computation algorithm, the algorithm
206 must be set first, see parameter names "algorithm" below.
208 =item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string>
210 Some MAC implementations require an IV, this parameter sets the IV.
212 =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
214 Some MAC implementations (KMAC, BLAKE2) accept a Customization String,
215 this parameter sets the Customization String. The default value is the
218 =item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string>
220 This option is used by BLAKE2 MAC.
222 =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
224 It's a simple flag, the value 0 or 1 are expected.
226 This option is used by KMAC.
228 =item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer>
230 A simple flag to set the MAC digest to not initialise the
231 implementation specific data. The value 0 or 1 is expected.
233 This option is used by HMAC.
235 =item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer>
237 A simple flag to set the MAC digest to be a oneshot operation.
238 The value 0 or 1 is expected.
240 This option is used by HMAC.
242 =item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string>
244 =item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string>
246 =item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string>
248 For MAC implementations that use an underlying computation cipher or
249 digest, these parameters set what the algorithm should be.
251 The value is always the name of the intended algorithm,
254 Note that not all algorithms may support all digests.
255 HMAC does not support variable output length digests such as SHAKE128
258 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
260 For MAC implementations that support it, set the output size that
261 EVP_MAC_final() should produce.
262 The allowed sizes vary between MAC implementations, but must never exceed
263 what can be given with a B<size_t>.
265 =item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer>
267 This parameter is only supported by HMAC. If set then special handling is
268 activated for calculating the MAC of a received mac-then-encrypt TLS record
269 where variable length record padding has been used (as in the case of CBC mode
270 ciphersuites). The value represents the total length of the record that is
271 having the MAC calculated including the received MAC and the record padding.
273 When used EVP_MAC_update must be called precisely twice. The first time with
274 the 13 bytes of TLS "header" data, and the second time with the entire record
275 including the MAC itself and any padding. The entire record length must equal
276 the value passed in the "tls-data-size" parameter. The length passed in the
277 B<datalen> parameter to EVP_MAC_update() should be equal to the length of the
278 record after the MAC and any padding has been removed.
282 All these parameters should be used before the calls to any of
283 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
285 Anything else may give undefined results.
289 EVP_MAC_fetch() returns a pointer to a newly fetched EVP_MAC, or
290 NULL if allocation failed.
292 EVP_MAC_up_ref() returns 1 on success, 0 on error.
294 EVP_MAC_free() returns nothing at all.
296 EVP_MAC_is_a() returns 1 if the given method can be identified with
297 the given name, otherwise 0.
299 EVP_MAC_name() returns a name of the MAC, or NULL on error.
301 EVP_MAC_provider() returns a pointer to the provider for the MAC, or
304 EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly
305 created EVP_MAC_CTX, or NULL if allocation failed.
307 EVP_MAC_CTX_free() returns nothing at all.
309 EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on
312 EVP_MAC_init(), EVP_MAC_update(), and EVP_MAC_final() return 1 on success, 0
315 EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't set.
316 If it isn't set, a call to EVP_MAC_init() should get it set.
318 EVP_MAC_do_all_provided() returns nothing at all.
328 #include <openssl/evp.h>
329 #include <openssl/err.h>
330 #include <openssl/params.h>
333 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
334 const char *cipher = getenv("MY_MAC_CIPHER");
335 const char *digest = getenv("MY_MAC_DIGEST");
336 const char *key = getenv("MY_KEY");
337 EVP_MAC_CTX *ctx = NULL;
339 unsigned char buf[4096];
345 OSSL_PARAM params[4];
350 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0);
353 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0);
355 OSSL_PARAM_construct_octet_string("key", (void*)key, strlen(key));
356 params[params_n] = OSSL_PARAM_construct_end();
360 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
361 || EVP_MAC_CTX_set_params(ctx, params) <= 0)
364 if (!EVP_MAC_init(ctx))
367 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
368 if (!EVP_MAC_update(ctx, buf, read_l))
372 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf)))
376 for (i = 0; i < final_l; i++)
377 printf("%02X", buf[i]);
380 EVP_MAC_CTX_free(ctx);
385 EVP_MAC_CTX_free(ctx);
387 fprintf(stderr, "Something went wrong\n");
388 ERR_print_errors_fp(stderr);
392 A run of this program, called with correct environment variables, can
395 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
396 LD_LIBRARY_PATH=. ./foo < foo.c
397 Result: C5C06683CD9DDEF904D754505C560A4E
399 (in this example, that program was stored in F<foo.c> and compiled to
406 L<EVP_MAC-BLAKE2(7)>,
411 L<EVP_MAC-Siphash(7)>,
412 L<EVP_MAC-Poly1305(7)>
416 These functions were added in OpenSSL 3.0.
420 Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
422 Licensed under the Apache License 2.0 (the "License"). You may not use
423 this file except in compliance with the License. You can obtain a copy
424 in the file LICENSE in the source distribution or at
425 L<https://www.openssl.org/source/license.html>.