5 EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free, EVP_MAC_is_a,
6 EVP_MAC_get0_name, EVP_MAC_names_do_all, EVP_MAC_get0_description,
7 EVP_MAC_get0_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_get0_mac, EVP_MAC_CTX_get_params, EVP_MAC_CTX_set_params,
10 EVP_MAC_CTX_get_mac_size, EVP_MAC_CTX_get_block_size, EVP_Q_mac,
11 EVP_MAC_init, EVP_MAC_update, EVP_MAC_final, EVP_MAC_finalXOF,
12 EVP_MAC_gettable_ctx_params, EVP_MAC_settable_ctx_params,
13 EVP_MAC_CTX_gettable_params, EVP_MAC_CTX_settable_params,
14 EVP_MAC_do_all_provided - EVP MAC routines
18 #include <openssl/evp.h>
20 typedef struct evp_mac_st EVP_MAC;
21 typedef struct evp_mac_ctx_st EVP_MAC_CTX;
23 EVP_MAC *EVP_MAC_fetch(OSSL_LIB_CTX *libctx, const char *algorithm,
24 const char *properties);
25 int EVP_MAC_up_ref(EVP_MAC *mac);
26 void EVP_MAC_free(EVP_MAC *mac);
27 int EVP_MAC_is_a(const EVP_MAC *mac, const char *name);
28 const char *EVP_MAC_get0_name(const EVP_MAC *mac);
29 int EVP_MAC_names_do_all(const EVP_MAC *mac,
30 void (*fn)(const char *name, void *data),
32 const char *EVP_MAC_get0_description(const EVP_MAC *mac);
33 const OSSL_PROVIDER *EVP_MAC_get0_provider(const EVP_MAC *mac);
34 int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]);
36 EVP_MAC_CTX *EVP_MAC_CTX_new(EVP_MAC *mac);
37 void EVP_MAC_CTX_free(EVP_MAC_CTX *ctx);
38 EVP_MAC_CTX *EVP_MAC_CTX_dup(const EVP_MAC_CTX *src);
39 EVP_MAC *EVP_MAC_CTX_get0_mac(EVP_MAC_CTX *ctx);
40 int EVP_MAC_CTX_get_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]);
41 int EVP_MAC_CTX_set_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]);
43 size_t EVP_MAC_CTX_get_mac_size(EVP_MAC_CTX *ctx);
44 size_t EVP_MAC_CTX_get_block_size(EVP_MAC_CTX *ctx);
45 unsigned char *EVP_Q_mac(OSSL_LIB_CTX *libctx, const char *name, const char *propq,
46 const char *subalg, const OSSL_PARAM *params,
47 const void *key, size_t keylen,
48 const unsigned char *data, size_t datalen,
49 unsigned char *out, size_t outsize, size_t *outlen);
50 int EVP_MAC_init(EVP_MAC_CTX *ctx, const unsigned char *key, size_t keylen,
51 const OSSL_PARAM params[]);
52 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
53 int EVP_MAC_final(EVP_MAC_CTX *ctx,
54 unsigned char *out, size_t *outl, size_t outsize);
55 int EVP_MAC_finalXOF(EVP_MAC_CTX *ctx, unsigned char *out, size_t outsize);
57 const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
58 const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
59 const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
60 const OSSL_PARAM *EVP_MAC_CTX_gettable_params(EVP_MAC_CTX *ctx);
61 const OSSL_PARAM *EVP_MAC_CTX_settable_params(EVP_MAC_CTX *ctx);
63 void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx,
64 void (*fn)(EVP_MAC *mac, void *arg),
69 These types and functions help the application to calculate MACs of
70 different types and with different underlying algorithms if there are
73 MACs are a bit complex insofar that some of them use other algorithms
74 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
75 Therefore, there are sometimes two contexts to keep track of, one for
76 the MAC algorithm itself and one for the underlying computation
77 algorithm if there is one.
79 To make things less ambiguous, this manual talks about a "context" or
80 "MAC context", which is to denote the MAC level context, and about a
81 "underlying context", or "computation context", which is to denote the
82 context for the underlying computation algorithm if there is one.
86 B<EVP_MAC> is a type that holds the implementation of a MAC.
88 B<EVP_MAC_CTX> is a context type that holds internal MAC information
89 as well as a reference to a computation context, for those MACs that
90 rely on an underlying computation algorithm.
92 =head2 Algorithm implementation fetching
94 EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given
95 a library context I<libctx> and a set of I<properties>.
96 See L<crypto(7)/ALGORITHM FETCHING> for further information.
98 See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list
99 of algorithms supported by the default provider.
101 The returned value must eventually be freed with
104 EVP_MAC_up_ref() increments the reference count of an already fetched
107 EVP_MAC_free() frees a fetched algorithm.
108 NULL is a valid parameter, for which this function is a no-op.
110 =head2 Context manipulation functions
112 EVP_MAC_CTX_new() creates a new context for the MAC type I<mac>.
113 The created context can then be used with most other functions
116 EVP_MAC_CTX_free() frees the contents of the context, including an
117 underlying context if there is one, as well as the context itself.
118 NULL is a valid parameter, for which this function is a no-op.
120 EVP_MAC_CTX_dup() duplicates the I<src> context and returns a newly allocated
123 EVP_MAC_CTX_get0_mac() returns the B<EVP_MAC> associated with the context
126 =head2 Computing functions
128 EVP_Q_mac() computes the message authentication code
129 of I<data> with length I<datalen>
130 using the MAC algorithm I<name> and the key I<key> with length I<keylen>.
131 The MAC algorithm is fetched using any given I<libctx> and property query
132 string I<propq>. It takes parameters I<subalg> and further I<params>,
133 both of which may be NULL if not needed.
134 If I<out> is not NULL, it places the result in the memory pointed at by I<out>,
135 but only if I<outsize> is sufficient (otherwise no computation is made).
136 If I<out> is NULL, it allocates and uses a buffer of suitable length,
137 which will be returned on success and must be freed by the caller.
138 In either case, also on error,
139 it assigns the number of bytes written to I<*outlen> unless I<outlen> is NULL.
141 EVP_MAC_init() sets up the underlying context I<ctx> with information given
142 via the I<key> and I<params> arguments. The MAC I<key> has a length of
143 I<keylen> and the parameters in I<params> are processed before setting
144 the key. If I<key> is NULL, the key must be set via I<params> either
145 as part of this call or separately using EVP_MAC_CTX_set_params().
146 Providing non-NULL I<params> to this function is equivalent to calling
147 EVP_MAC_CTX_set_params() with those I<params> for the same I<ctx> beforehand.
148 Note: There are additional requirements for some MAC algorithms during
149 re-initalization (i.e. calling EVP_MAC_init() on an EVP_MAC after EVP_MAC_final()
150 has been called on the same object). See the NOTES section below.
152 EVP_MAC_init() should be called before EVP_MAC_update() and EVP_MAC_final().
154 EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input.
156 EVP_MAC_final() does the final computation and stores the result in
157 the memory pointed at by I<out> of size I<outsize>, and sets the number
158 of bytes written in I<*outl> at.
159 If I<out> is NULL or I<outsize> is too small, then no computation
161 To figure out what the output length will be and allocate space for it
162 dynamically, simply call with I<out> being NULL and I<outl>
163 pointing at a valid location, then allocate space and make a second
164 call with I<out> pointing at the allocated space.
166 EVP_MAC_finalXOF() does the final computation for an XOF based MAC and stores
167 the result in the memory pointed at by I<out> of size I<outsize>.
169 EVP_MAC_get_params() retrieves details about the implementation
171 The set of parameters given with I<params> determine exactly what
172 parameters should be retrieved.
173 Note that a parameter that is unknown in the underlying context is
176 EVP_MAC_CTX_get_params() retrieves chosen parameters, given the
177 context I<ctx> and its underlying context.
178 The set of parameters given with I<params> determine exactly what
179 parameters should be retrieved.
180 Note that a parameter that is unknown in the underlying context is
183 EVP_MAC_CTX_set_params() passes chosen parameters to the underlying
184 context, given a context I<ctx>.
185 The set of parameters given with I<params> determine exactly what
186 parameters are passed down.
187 If I<params> are NULL, the underlying context should do nothing and return 1.
188 Note that a parameter that is unknown in the underlying context is
190 Also, what happens when a needed parameter isn't passed down is
191 defined by the implementation.
193 EVP_MAC_gettable_params() returns an L<OSSL_PARAM(3)> array that describes
194 the retrievable and settable parameters. EVP_MAC_gettable_params()
195 returns parameters that can be used with EVP_MAC_get_params().
197 EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params()
198 return constant L<OSSL_PARAM(3)> arrays that describe the retrievable
199 parameters that can be used with EVP_MAC_CTX_get_params().
200 EVP_MAC_gettable_ctx_params() returns the parameters that can be retrieved
201 from the algorithm, whereas EVP_MAC_CTX_gettable_params() returns
202 the parameters that can be retrieved in the context's current state.
204 EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return
205 constant L<OSSL_PARAM(3)> arrays that describe the settable parameters that
206 can be used with EVP_MAC_CTX_set_params(). EVP_MAC_settable_ctx_params()
207 returns the parameters that can be retrieved from the algorithm,
208 whereas EVP_MAC_CTX_settable_params() returns the parameters that can
209 be retrieved in the context's current state.
211 =head2 Information functions
213 EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context.
215 EVP_MAC_CTX_get_block_size() returns the MAC block size for the given context.
216 Not all MAC algorithms support this.
218 EVP_MAC_is_a() checks if the given I<mac> is an implementation of an
219 algorithm that's identifiable with I<name>.
221 EVP_MAC_get0_provider() returns the provider that holds the implementation
224 EVP_MAC_do_all_provided() traverses all MAC implemented by all activated
225 providers in the given library context I<libctx>, and for each of the
226 implementations, calls the given function I<fn> with the implementation method
227 and the given I<arg> as argument.
229 EVP_MAC_get0_name() return the name of the given MAC. For fetched MACs
230 with multiple names, only one of them is returned; it's
231 recommended to use EVP_MAC_names_do_all() instead.
233 EVP_MAC_names_do_all() traverses all names for I<mac>, and calls
234 I<fn> with each name and I<data>.
236 EVP_MAC_get0_description() returns a description of the I<mac>, meant
237 for display and human consumption. The description is at the discretion
238 of the mac implementation.
242 Parameters are identified by name as strings, and have an expected
243 data type and maximum size.
244 OpenSSL has a set of macros for parameter names it expects to see in
245 its own MAC implementations.
246 Here, we show all three, the OpenSSL macro for the parameter name, the
247 name in string form, and a type description.
249 The standard parameter names are:
253 =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
255 Its value is the MAC key as an array of bytes.
257 For MACs that use an underlying computation algorithm, the algorithm
258 must be set first, see parameter names "algorithm" below.
260 =item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string>
262 Some MAC implementations (GMAC) require an IV, this parameter sets the IV.
264 =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
266 Some MAC implementations (KMAC, BLAKE2) accept a Customization String,
267 this parameter sets the Customization String. The default value is the
270 =item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string>
272 This option is used by BLAKE2 MAC.
274 =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
276 It's a simple flag, the value 0 or 1 are expected.
278 This option is used by KMAC.
280 =item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer>
282 A simple flag to set the MAC digest to not initialise the
283 implementation specific data. The value 0 or 1 is expected.
285 This option is deprecated and will be removed in a future release.
286 The option may be set, but is ignored.
288 =item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer>
290 A simple flag to set the MAC digest to be a oneshot operation.
291 The value 0 or 1 is expected.
293 This option is deprecated and will be removed in a future release.
294 The option may be set, but is ignored.
296 =item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string>
298 =item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string>
300 =item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string>
302 For MAC implementations that use an underlying computation cipher or
303 digest, these parameters set what the algorithm should be.
305 The value is always the name of the intended algorithm,
308 Note that not all algorithms may support all digests.
309 HMAC does not support variable output length digests such as SHAKE128
312 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
314 For MAC implementations that support it, set the output size that
315 EVP_MAC_final() should produce.
316 The allowed sizes vary between MAC implementations, but must never exceed
317 what can be given with a B<size_t>.
319 =item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer>
321 This parameter is only supported by HMAC. If set then special handling is
322 activated for calculating the MAC of a received mac-then-encrypt TLS record
323 where variable length record padding has been used (as in the case of CBC mode
324 ciphersuites). The value represents the total length of the record that is
325 having the MAC calculated including the received MAC and the record padding.
327 When used EVP_MAC_update must be called precisely twice. The first time with
328 the 13 bytes of TLS "header" data, and the second time with the entire record
329 including the MAC itself and any padding. The entire record length must equal
330 the value passed in the "tls-data-size" parameter. The length passed in the
331 B<datalen> parameter to EVP_MAC_update() should be equal to the length of the
332 record after the MAC and any padding has been removed.
336 All these parameters should be used before the calls to any of
337 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
339 Anything else may give undefined results.
343 The MAC life-cycle is described in L<life_cycle-mac(7)>. In the future,
344 the transitions described there will be enforced. When this is done, it will
345 not be considered a breaking change to the API.
347 The usage of the parameter names "custom", "iv" and "salt" correspond to
348 the names used in the standard where the algorithm was defined.
350 Some MAC algorithms store internal state that cannot be extracted during
351 re-initalization. For example GMAC cannot extract an B<IV> from the
352 underlying CIPHER context, and so calling EVP_MAC_init() on an EVP_MAC object
353 after EVP_MAC_final() has been called cannot reset its cipher state to what it
354 was when the B<IV> was initially generated. For such instances, an
355 B<OSSL_MAC_PARAM_IV> parameter must be passed with each call to EVP_MAC_init().
359 EVP_MAC_fetch() returns a pointer to a newly fetched B<EVP_MAC>, or
360 NULL if allocation failed.
362 EVP_MAC_up_ref() returns 1 on success, 0 on error.
364 EVP_MAC_names_do_all() returns 1 if the callback was called for all names. A
365 return value of 0 means that the callback was not called for any names.
367 EVP_MAC_free() returns nothing at all.
369 EVP_MAC_is_a() returns 1 if the given method can be identified with
370 the given name, otherwise 0.
372 EVP_MAC_get0_name() returns a name of the MAC, or NULL on error.
374 EVP_MAC_get0_provider() returns a pointer to the provider for the MAC, or
377 EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly
378 created EVP_MAC_CTX, or NULL if allocation failed.
380 EVP_MAC_CTX_free() returns nothing at all.
382 EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on
385 EVP_Q_mac() returns a pointer to the computed MAC value, or NULL on error.
387 EVP_MAC_init(), EVP_MAC_update(), EVP_MAC_final(), and EVP_MAC_finalXOF()
388 return 1 on success, 0 on error.
390 EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't
391 set. If it isn't set, a call to EVP_MAC_init() will set it.
393 EVP_MAC_CTX_get_block_size() returns the block size, or 0 if it isn't set.
394 If it isn't set, a call to EVP_MAC_init() will set it.
396 EVP_MAC_do_all_provided() returns nothing at all.
406 #include <openssl/evp.h>
407 #include <openssl/err.h>
408 #include <openssl/params.h>
411 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
412 const char *cipher = getenv("MY_MAC_CIPHER");
413 const char *digest = getenv("MY_MAC_DIGEST");
414 const char *key = getenv("MY_KEY");
415 EVP_MAC_CTX *ctx = NULL;
417 unsigned char buf[4096];
423 OSSL_PARAM params[3];
428 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0);
431 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0);
432 params[params_n] = OSSL_PARAM_construct_end();
436 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
437 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key),
441 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
442 if (!EVP_MAC_update(ctx, buf, read_l))
446 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf)))
450 for (i = 0; i < final_l; i++)
451 printf("%02X", buf[i]);
454 EVP_MAC_CTX_free(ctx);
459 EVP_MAC_CTX_free(ctx);
461 fprintf(stderr, "Something went wrong\n");
462 ERR_print_errors_fp(stderr);
466 A run of this program, called with correct environment variables, can
469 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
470 LD_LIBRARY_PATH=. ./foo < foo.c
471 Result: C5C06683CD9DDEF904D754505C560A4E
473 (in this example, that program was stored in F<foo.c> and compiled to
480 L<EVP_MAC-BLAKE2(7)>,
485 L<EVP_MAC-Siphash(7)>,
486 L<EVP_MAC-Poly1305(7)>,
492 These functions were added in OpenSSL 3.0.
496 Copyright 2018-2024 The OpenSSL Project Authors. All Rights Reserved.
498 Licensed under the Apache License 2.0 (the "License"). You may not use
499 this file except in compliance with the License. You can obtain a copy
500 in the file LICENSE in the source distribution or at
501 L<https://www.openssl.org/source/license.html>.