5 EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free, EVP_MAC_is_a,
6 EVP_MAC_number, EVP_MAC_name, EVP_MAC_names_do_all, EVP_MAC_description,
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_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 int EVP_MAC_number(const EVP_MAC *mac);
29 const char *EVP_MAC_name(const EVP_MAC *mac);
30 int EVP_MAC_names_do_all(const EVP_MAC *mac,
31 void (*fn)(const char *name, void *data),
33 const char *EVP_MAC_description(const EVP_MAC *mac);
34 const OSSL_PROVIDER *EVP_MAC_provider(const EVP_MAC *mac);
35 int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]);
37 EVP_MAC_CTX *EVP_MAC_CTX_new(EVP_MAC *mac);
38 void EVP_MAC_CTX_free(EVP_MAC_CTX *ctx);
39 EVP_MAC_CTX *EVP_MAC_CTX_dup(const EVP_MAC_CTX *src);
40 EVP_MAC *EVP_MAC_CTX_mac(EVP_MAC_CTX *ctx);
41 int EVP_MAC_CTX_get_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]);
42 int EVP_MAC_CTX_set_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]);
44 size_t EVP_MAC_CTX_get_mac_size(EVP_MAC_CTX *ctx);
45 size_t EVP_MAC_CTX_get_block_size(EVP_MAC_CTX *ctx);
46 unsigned char *EVP_Q_mac(OSSL_LIB_CTX *libctx, const char *name, const char *propq,
47 const char *subalg, const OSSL_PARAM *params,
48 const void *key, size_t keylen,
49 const unsigned char *data, size_t datalen,
50 unsigned char *out, size_t outsize, unsigned int *outlen);
51 int EVP_MAC_init(EVP_MAC_CTX *ctx, const unsigned char *key, size_t keylen,
52 const OSSL_PARAM params[]);
53 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
54 int EVP_MAC_final(EVP_MAC_CTX *ctx,
55 unsigned char *out, size_t *outl, size_t outsize);
56 int EVP_MAC_finalXOF(EVP_MAC_CTX *ctx, unsigned char *out, size_t outsize);
58 const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
59 const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
60 const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
61 const OSSL_PARAM *EVP_MAC_CTX_gettable_params(EVP_MAC_CTX *ctx);
62 const OSSL_PARAM *EVP_MAC_CTX_settable_params(EVP_MAC_CTX *ctx);
64 void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx,
65 void (*fn)(EVP_MAC *mac, void *arg),
70 These types and functions help the application to calculate MACs of
71 different types and with different underlying algorithms if there are
74 MACs are a bit complex insofar that some of them use other algorithms
75 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
76 Therefore, there are sometimes two contexts to keep track of, one for
77 the MAC algorithm itself and one for the underlying computation
78 algorithm if there is one.
80 To make things less ambiguous, this manual talks about a "context" or
81 "MAC context", which is to denote the MAC level context, and about a
82 "underlying context", or "computation context", which is to denote the
83 context for the underlying computation algorithm if there is one.
87 B<EVP_MAC> is a type that holds the implementation of a MAC.
89 B<EVP_MAC_CTX> is a context type that holds internal MAC information
90 as well as a reference to a computation context, for those MACs that
91 rely on an underlying computation algorithm.
93 =head2 Algorithm implementation fetching
95 EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given
96 a library context I<libctx> and a set of I<properties>.
97 See L<crypto(7)/ALGORITHM FETCHING> for further information.
99 See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list
100 of algorithms supported by the default provider.
102 The returned value must eventually be freed with
105 EVP_MAC_up_ref() increments the reference count of an already fetched
108 EVP_MAC_free() frees a fetched algorithm.
109 NULL is a valid parameter, for which this function is a no-op.
111 =head2 Context manipulation functions
113 EVP_MAC_CTX_new() creates a new context for the MAC type I<mac>.
114 The created context can then be used with most other functions
117 EVP_MAC_CTX_free() frees the contents of the context, including an
118 underlying context if there is one, as well as the context itself.
119 NULL is a valid parameter, for which this function is a no-op.
121 EVP_MAC_CTX_dup() duplicates the I<src> context and returns a newly allocated
124 EVP_MAC_CTX_mac() returns the B<EVP_MAC> associated with the context
127 =head2 Computing functions
129 EVP_Q_mac() computes the message authentication code
130 of I<data> with length I<datalen>
131 using the MAC algorithm I<name> and the key I<key> with length I<keylen>.
132 The MAC algorithm is fetched using any given I<libctx> and property query
133 string I<propq>. It takes parameters I<subalg> and further I<params>,
134 both of which may be NULL if not needed.
135 If I<out> is not NULL, it places the result in the memory pointed at by I<out>,
136 but only if I<outsize> is sufficient (otherwise no computation is made).
137 If I<out> is NULL, it allocates and uses a buffer of suitable length,
138 which will be returned on success and must be freed by the caller.
139 In either case, also on error,
140 it assigns the number of bytes written to I<*outlen> unless I<outlen> is NULL.
142 EVP_MAC_init() sets up the underlying context I<ctx> with information given
143 via the I<key> and I<params> arguments. The MAC I<key> has a length of
144 I<keylen> and the parameters in I<params> are processed before setting
145 the key. If I<key> is NULL, the key must be set via I<params> either
146 as part of this call or separately using EVP_MAC_CTX_set_params().
147 Providing non-NULL I<params> to this function is equivalent to calling
148 EVP_MAC_CTX_set_params() with those I<params> for the same I<ctx> beforehand.
150 EVP_MAC_init() should be called before EVP_MAC_update() and EVP_MAC_final().
152 EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input.
154 EVP_MAC_final() does the final computation and stores the result in
155 the memory pointed at by I<out> of size I<outsize>, and sets the number
156 of bytes written in I<*outl> at.
157 If I<out> is NULL or I<outsize> is too small, then no computation
159 To figure out what the output length will be and allocate space for it
160 dynamically, simply call with I<out> being NULL and I<outl>
161 pointing at a valid location, then allocate space and make a second
162 call with I<out> pointing at the allocated space.
164 EVP_MAC_finalXOF() does the final computation for an XOF based MAC and stores
165 the result in the memory pointed at by I<out> of size I<outsize>.
167 EVP_MAC_get_params() retrieves details about the implementation
169 The set of parameters given with I<params> determine exactly what
170 parameters should be retrieved.
171 Note that a parameter that is unknown in the underlying context is
174 EVP_MAC_CTX_get_params() retrieves chosen parameters, given the
175 context I<ctx> and its underlying context.
176 The set of parameters given with I<params> determine exactly what
177 parameters should be retrieved.
178 Note that a parameter that is unknown in the underlying context is
181 EVP_MAC_CTX_set_params() passes chosen parameters to the underlying
182 context, given a context I<ctx>.
183 The set of parameters given with I<params> determine exactly what
184 parameters are passed down.
185 If I<params> are NULL, the unterlying context should do nothing and return 1.
186 Note that a parameter that is unknown in the underlying context is
188 Also, what happens when a needed parameter isn't passed down is
189 defined by the implementation.
191 EVP_MAC_gettable_params() returns an B<OSSL_PARAM> array that describes
192 the retrievable and settable parameters. EVP_MAC_gettable_params()
193 returns parameters that can be used with EVP_MAC_get_params().
194 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor.
196 EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params()
197 return constant B<OSSL_PARAM> arrays that describe the retrievable
198 parameters that can be used with EVP_MAC_CTX_get_params().
199 EVP_MAC_gettable_ctx_params() returns the parameters that can be retrieved
200 from the algorithm, whereas EVP_MAC_CTX_gettable_params() returns
201 the parameters that can be retrieved in the context's current state.
202 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor.
204 EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return
205 constant B<OSSL_PARAM> 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. See L<OSSL_PARAM(3)>
210 for the use of B<OSSL_PARAM> as a parameter descriptor.
212 =head2 Information functions
214 EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context.
216 EVP_MAC_CTX_get_block_size() returns the MAC block size for the given context.
217 Not all MAC algorithms support this.
219 EVP_MAC_is_a() checks if the given I<mac> is an implementation of an
220 algorithm that's identifiable with I<name>.
222 EVP_MAC_provider() returns the provider that holds the implementation
225 EVP_MAC_do_all_provided() traverses all MAC implemented by all activated
226 providers in the given library context I<libctx>, and for each of the
227 implementations, calls the given function I<fn> with the implementation method
228 and the given I<arg> as argument.
230 EVP_MAC_number() returns the internal dynamic number assigned to
233 EVP_MAC_name() return the name of the given MAC. For fetched MACs
234 with multiple names, only one of them is returned; it's
235 recommended to use EVP_MAC_names_do_all() instead.
237 EVP_MAC_names_do_all() traverses all names for I<mac>, and calls
238 I<fn> with each name and I<data>.
240 EVP_MAC_description() returns a description of the I<mac>, meant for display
241 and human consumption. The description is at the discretion of the mac
246 Parameters are identified by name as strings, and have an expected
247 data type and maximum size.
248 OpenSSL has a set of macros for parameter names it expects to see in
249 its own MAC implementations.
250 Here, we show all three, the OpenSSL macro for the parameter name, the
251 name in string form, and a type description.
253 The standard parameter names are:
257 =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
259 Its value is the MAC key as an array of bytes.
261 For MACs that use an underlying computation algorithm, the algorithm
262 must be set first, see parameter names "algorithm" below.
264 =item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string>
266 Some MAC implementations (GMAC) require an IV, this parameter sets the IV.
268 =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
270 Some MAC implementations (KMAC, BLAKE2) accept a Customization String,
271 this parameter sets the Customization String. The default value is the
274 =item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string>
276 This option is used by BLAKE2 MAC.
278 =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
280 It's a simple flag, the value 0 or 1 are expected.
282 This option is used by KMAC.
284 =item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer>
286 A simple flag to set the MAC digest to not initialise the
287 implementation specific data. The value 0 or 1 is expected.
289 This option is used by HMAC.
291 =item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer>
293 A simple flag to set the MAC digest to be a oneshot operation.
294 The value 0 or 1 is expected.
296 This option is used by HMAC.
298 =item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string>
300 =item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string>
302 =item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string>
304 For MAC implementations that use an underlying computation cipher or
305 digest, these parameters set what the algorithm should be.
307 The value is always the name of the intended algorithm,
310 Note that not all algorithms may support all digests.
311 HMAC does not support variable output length digests such as SHAKE128
314 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
316 For MAC implementations that support it, set the output size that
317 EVP_MAC_final() should produce.
318 The allowed sizes vary between MAC implementations, but must never exceed
319 what can be given with a B<size_t>.
321 =item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer>
323 This parameter is only supported by HMAC. If set then special handling is
324 activated for calculating the MAC of a received mac-then-encrypt TLS record
325 where variable length record padding has been used (as in the case of CBC mode
326 ciphersuites). The value represents the total length of the record that is
327 having the MAC calculated including the received MAC and the record padding.
329 When used EVP_MAC_update must be called precisely twice. The first time with
330 the 13 bytes of TLS "header" data, and the second time with the entire record
331 including the MAC itself and any padding. The entire record length must equal
332 the value passed in the "tls-data-size" parameter. The length passed in the
333 B<datalen> parameter to EVP_MAC_update() should be equal to the length of the
334 record after the MAC and any padding has been removed.
338 All these parameters should be used before the calls to any of
339 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
341 Anything else may give undefined results.
345 The MAC life-cycle is described in L<life_cycle-mac(7)>. In the future,
346 the transitions described there will be enforced. When this is done, it will
347 not be considered a breaking change to the API.
349 The usage of the parameter names "custom", "iv" and "salt" correspond to
350 the names used in the standard where the algorithm was defined.
354 EVP_MAC_fetch() returns a pointer to a newly fetched B<EVP_MAC>, or
355 NULL if allocation failed.
357 EVP_MAC_up_ref() returns 1 on success, 0 on error.
359 EVP_MAC_names_do_all() returns 1 if the callback was called for all names. A
360 return value of 0 means that the callback was not called for any names.
362 EVP_MAC_free() returns nothing at all.
364 EVP_MAC_is_a() returns 1 if the given method can be identified with
365 the given name, otherwise 0.
367 EVP_MAC_name() returns a name of the MAC, or NULL on error.
369 EVP_MAC_provider() returns a pointer to the provider for the MAC, or
372 EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly
373 created EVP_MAC_CTX, or NULL if allocation failed.
375 EVP_MAC_CTX_free() returns nothing at all.
377 EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on
380 EVP_Q_mac() returns a pointer to the computed MAC value, or NULL on error.
382 EVP_MAC_init(), EVP_MAC_update(), EVP_MAC_final(), and EVP_MAC_finalXOF()
383 return 1 on success, 0 on error.
385 EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't
386 set. If it isn't set, a call to EVP_MAC_init() will set it.
388 EVP_MAC_CTX_get_block_size() returns the block size, or 0 if it isn't set.
389 If it isn't set, a call to EVP_MAC_init() will set it.
391 EVP_MAC_do_all_provided() returns nothing at all.
401 #include <openssl/evp.h>
402 #include <openssl/err.h>
403 #include <openssl/params.h>
406 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
407 const char *cipher = getenv("MY_MAC_CIPHER");
408 const char *digest = getenv("MY_MAC_DIGEST");
409 const char *key = getenv("MY_KEY");
410 EVP_MAC_CTX *ctx = NULL;
412 unsigned char buf[4096];
418 OSSL_PARAM params[3];
423 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0);
426 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0);
427 params[params_n] = OSSL_PARAM_construct_end();
431 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
432 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key),
436 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
437 if (!EVP_MAC_update(ctx, buf, read_l))
441 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf)))
445 for (i = 0; i < final_l; i++)
446 printf("%02X", buf[i]);
449 EVP_MAC_CTX_free(ctx);
454 EVP_MAC_CTX_free(ctx);
456 fprintf(stderr, "Something went wrong\n");
457 ERR_print_errors_fp(stderr);
461 A run of this program, called with correct environment variables, can
464 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
465 LD_LIBRARY_PATH=. ./foo < foo.c
466 Result: C5C06683CD9DDEF904D754505C560A4E
468 (in this example, that program was stored in F<foo.c> and compiled to
475 L<EVP_MAC-BLAKE2(7)>,
480 L<EVP_MAC-Siphash(7)>,
481 L<EVP_MAC-Poly1305(7)>,
487 These functions were added in OpenSSL 3.0.
491 Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
493 Licensed under the Apache License 2.0 (the "License"). You may not use
494 this file except in compliance with the License. You can obtain a copy
495 in the file LICENSE in the source distribution or at
496 L<https://www.openssl.org/source/license.html>.