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_CTX_gettable_params, EVP_MAC_CTX_settable_params,
13 EVP_MAC_do_all_provided - EVP MAC routines
17 #include <openssl/evp.h>
19 typedef struct evp_mac_st EVP_MAC;
20 typedef struct evp_mac_ctx_st EVP_MAC_CTX;
22 EVP_MAC *EVP_MAC_fetch(OSSL_LIB_CTX *libctx, const char *algorithm,
23 const char *properties);
24 int EVP_MAC_up_ref(EVP_MAC *mac);
25 void EVP_MAC_free(EVP_MAC *mac);
26 int EVP_MAC_is_a(const EVP_MAC *mac, const char *name);
27 int EVP_MAC_number(const EVP_MAC *mac);
28 const char *EVP_MAC_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 OSSL_PROVIDER *EVP_MAC_provider(const EVP_MAC *mac);
33 int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]);
35 EVP_MAC_CTX *EVP_MAC_CTX_new(EVP_MAC *mac);
36 void EVP_MAC_CTX_free(EVP_MAC_CTX *ctx);
37 EVP_MAC_CTX *EVP_MAC_CTX_dup(const EVP_MAC_CTX *src);
38 EVP_MAC *EVP_MAC_CTX_mac(EVP_MAC_CTX *ctx);
39 int EVP_MAC_CTX_get_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]);
40 int EVP_MAC_CTX_set_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]);
42 size_t EVP_MAC_CTX_get_mac_size(EVP_MAC_CTX *ctx);
43 int EVP_MAC_init(EVP_MAC_CTX *ctx, const unsigned char *key, size_t keylen,
44 const OSSL_PARAM params[]);
45 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
46 int EVP_MAC_final(EVP_MAC_CTX *ctx,
47 unsigned char *out, size_t *outl, size_t outsize);
49 const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
50 const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
51 const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
52 const OSSL_PARAM *EVP_MAC_CTX_gettable_params(EVP_MAC_CTX *ctx);
53 const OSSL_PARAM *EVP_MAC_CTX_settable_params(EVP_MAC_CTX *ctx);
55 void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx,
56 void (*fn)(EVP_MAC *mac, void *arg),
61 These types and functions help the application to calculate MACs of
62 different types and with different underlying algorithms if there are
65 MACs are a bit complex insofar that some of them use other algorithms
66 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
67 Therefore, there are sometimes two contexts to keep track of, one for
68 the MAC algorithm itself and one for the underlying computation
69 algorithm if there is one.
71 To make things less ambiguous, this manual talks about a "context" or
72 "MAC context", which is to denote the MAC level context, and about a
73 "underlying context", or "computation context", which is to denote the
74 context for the underlying computation algorithm if there is one.
78 B<EVP_MAC> is a type that holds the implementation of a MAC.
80 B<EVP_MAC_CTX> is a context type that holds internal MAC information
81 as well as a reference to a computation context, for those MACs that
82 rely on an underlying computation algorithm.
84 =head2 Algorithm implementation fetching
86 EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given
87 a library context I<libctx> and a set of I<properties>.
88 See L<provider(7)/Fetching algorithms> for further information.
90 See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list
91 of algorithms supported by the default provider.
93 The returned value must eventually be freed with
96 EVP_MAC_up_ref() increments the reference count of an already fetched
99 EVP_MAC_free() frees a fetched algorithm.
100 NULL is a valid parameter, for which this function is a no-op.
102 =head2 Context manipulation functions
104 EVP_MAC_CTX_new() creates a new context for the MAC type I<mac>.
105 The created context can then be used with most other functions
108 EVP_MAC_CTX_free() frees the contents of the context, including an
109 underlying context if there is one, as well as the context itself.
110 NULL is a valid parameter, for which this function is a no-op.
112 EVP_MAC_CTX_dup() duplicates the I<src> context and returns a newly allocated
115 EVP_MAC_CTX_mac() returns the B<EVP_MAC> associated with the context
118 =head2 Computing functions
120 EVP_MAC_init() sets up the underlying context with information given
121 via the I<key> and I<params> arguments. The MAC I<key> has a length of
122 I<keylen> and the parameters in I<params> are processed before setting
123 the key. If I<key> is NULL, the key must be set via params either
124 as part of this call or separately using EVP_MAC_CTX_set_params().
125 This should be called before calling EVP_MAC_update() and EVP_MAC_final().
127 EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input.
129 EVP_MAC_final() does the final computation and stores the result in
130 the memory pointed at by I<out> of size I<outsize>, and sets the number
131 of bytes written in I<*outl> at.
132 If I<out> is NULL or I<outsize> is too small, then no computation
134 To figure out what the output length will be and allocate space for it
135 dynamically, simply call with I<out> being NULL and I<outl>
136 pointing at a valid location, then allocate space and make a second
137 call with I<out> pointing at the allocated space.
139 EVP_MAC_get_params() retrieves details about the implementation
141 The set of parameters given with I<params> determine exactly what
142 parameters should be retrieved.
143 Note that a parameter that is unknown in the underlying context is
146 EVP_MAC_CTX_get_params() retrieves chosen parameters, given the
147 context I<ctx> and its underlying context.
148 The set of parameters given with I<params> determine exactly what
149 parameters should be retrieved.
150 Note that a parameter that is unknown in the underlying context is
153 EVP_MAC_CTX_set_params() passes chosen parameters to the underlying
154 context, given a context I<ctx>.
155 The set of parameters given with I<params> determine exactly what
156 parameters are passed down.
157 Note that a parameter that is unknown in the underlying context is
159 Also, what happens when a needed parameter isn't passed down is
160 defined by the implementation.
162 EVP_MAC_gettable_params() returns an B<OSSL_PARAM> array that describes
163 the retrievable and settable parameters. EVP_MAC_gettable_params()
164 returns parameters that can be used with EVP_MAC_get_params().
165 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor.
167 EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params()
168 return constant B<OSSL_PARAM> arrays that describe the retrievable
169 parameters that can be used with EVP_MAC_CTX_get_params().
170 EVP_MAC_gettable_ctx_params() returns the parameters that can be retrieved
171 from the algorithm, whereas EVP_MAC_CTX_gettable_params() returns
172 the parameters that can be retrieved in the context's current state.
173 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor.
175 EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return
176 constant B<OSSL_PARAM> arrays that describe the settable parameters that
177 can be used with EVP_MAC_CTX_set_params(). EVP_MAC_settable_ctx_params()
178 returns the parameters that can be retrieved from the algorithm,
179 whereas EVP_MAC_CTX_settable_params() returns the parameters that can
180 be retrieved in the context's current state. See L<OSSL_PARAM(3)>
181 for the use of B<OSSL_PARAM> as a parameter descriptor.
183 =head2 Information functions
185 EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context.
187 EVP_MAC_is_a() checks if the given I<mac> is an implementation of an
188 algorithm that's identifiable with I<name>.
190 EVP_MAC_provider() returns the provider that holds the implementation
193 EVP_MAC_do_all_provided() traverses all MAC implemented by all activated
194 providers in the given library context I<libctx>, and for each of the
195 implementations, calls the given function I<fn> with the implementation method
196 and the given I<arg> as argument.
198 EVP_MAC_number() returns the internal dynamic number assigned to
201 EVP_MAC_name() return the name of the given MAC. For fetched MACs
202 with multiple names, only one of them is returned; it's
203 recommended to use EVP_MAC_names_do_all() instead.
205 EVP_MAC_names_do_all() traverses all names for I<mac>, and calls
206 I<fn> with each name and I<data>.
210 Parameters are identified by name as strings, and have an expected
211 data type and maximum size.
212 OpenSSL has a set of macros for parameter names it expects to see in
213 its own MAC implementations.
214 Here, we show all three, the OpenSSL macro for the parameter name, the
215 name in string form, and a type description.
217 The standard parameter names are:
221 =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
223 Its value is the MAC key as an array of bytes.
225 For MACs that use an underlying computation algorithm, the algorithm
226 must be set first, see parameter names "algorithm" below.
228 =item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string>
230 Some MAC implementations require an IV, this parameter sets the IV.
232 =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
234 Some MAC implementations (KMAC, BLAKE2) accept a Customization String,
235 this parameter sets the Customization String. The default value is the
238 =item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string>
240 This option is used by BLAKE2 MAC.
242 =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
244 It's a simple flag, the value 0 or 1 are expected.
246 This option is used by KMAC.
248 =item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer>
250 A simple flag to set the MAC digest to not initialise the
251 implementation specific data. The value 0 or 1 is expected.
253 This option is used by HMAC.
255 =item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer>
257 A simple flag to set the MAC digest to be a oneshot operation.
258 The value 0 or 1 is expected.
260 This option is used by HMAC.
262 =item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string>
264 =item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string>
266 =item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string>
268 For MAC implementations that use an underlying computation cipher or
269 digest, these parameters set what the algorithm should be.
271 The value is always the name of the intended algorithm,
274 Note that not all algorithms may support all digests.
275 HMAC does not support variable output length digests such as SHAKE128
278 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
280 For MAC implementations that support it, set the output size that
281 EVP_MAC_final() should produce.
282 The allowed sizes vary between MAC implementations, but must never exceed
283 what can be given with a B<size_t>.
285 =item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer>
287 This parameter is only supported by HMAC. If set then special handling is
288 activated for calculating the MAC of a received mac-then-encrypt TLS record
289 where variable length record padding has been used (as in the case of CBC mode
290 ciphersuites). The value represents the total length of the record that is
291 having the MAC calculated including the received MAC and the record padding.
293 When used EVP_MAC_update must be called precisely twice. The first time with
294 the 13 bytes of TLS "header" data, and the second time with the entire record
295 including the MAC itself and any padding. The entire record length must equal
296 the value passed in the "tls-data-size" parameter. The length passed in the
297 B<datalen> parameter to EVP_MAC_update() should be equal to the length of the
298 record after the MAC and any padding has been removed.
302 All these parameters should be used before the calls to any of
303 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
305 Anything else may give undefined results.
309 EVP_MAC_fetch() returns a pointer to a newly fetched EVP_MAC, or
310 NULL if allocation failed.
312 EVP_MAC_up_ref() returns 1 on success, 0 on error.
314 EVP_MAC_names_do_all() returns 1 if the callback was called for all names. A
315 return value of 0 means that the callback was not called for any names.
317 EVP_MAC_free() returns nothing at all.
319 EVP_MAC_is_a() returns 1 if the given method can be identified with
320 the given name, otherwise 0.
322 EVP_MAC_name() returns a name of the MAC, or NULL on error.
324 EVP_MAC_provider() returns a pointer to the provider for the MAC, or
327 EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly
328 created EVP_MAC_CTX, or NULL if allocation failed.
330 EVP_MAC_CTX_free() returns nothing at all.
332 EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on
335 EVP_MAC_init(), EVP_MAC_update(), and EVP_MAC_final() return 1 on success, 0
338 EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't set.
339 If it isn't set, a call to EVP_MAC_init() should get it set.
341 EVP_MAC_do_all_provided() returns nothing at all.
351 #include <openssl/evp.h>
352 #include <openssl/err.h>
353 #include <openssl/params.h>
356 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
357 const char *cipher = getenv("MY_MAC_CIPHER");
358 const char *digest = getenv("MY_MAC_DIGEST");
359 const char *key = getenv("MY_KEY");
360 EVP_MAC_CTX *ctx = NULL;
362 unsigned char buf[4096];
368 OSSL_PARAM params[3];
373 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0);
376 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0);
377 params[params_n] = OSSL_PARAM_construct_end();
381 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
382 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key),
386 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
387 if (!EVP_MAC_update(ctx, buf, read_l))
391 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf)))
395 for (i = 0; i < final_l; i++)
396 printf("%02X", buf[i]);
399 EVP_MAC_CTX_free(ctx);
404 EVP_MAC_CTX_free(ctx);
406 fprintf(stderr, "Something went wrong\n");
407 ERR_print_errors_fp(stderr);
411 A run of this program, called with correct environment variables, can
414 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
415 LD_LIBRARY_PATH=. ./foo < foo.c
416 Result: C5C06683CD9DDEF904D754505C560A4E
418 (in this example, that program was stored in F<foo.c> and compiled to
425 L<EVP_MAC-BLAKE2(7)>,
430 L<EVP_MAC-Siphash(7)>,
431 L<EVP_MAC-Poly1305(7)>
435 These functions were added in OpenSSL 3.0.
439 Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
441 Licensed under the Apache License 2.0 (the "License"). You may not use
442 this file except in compliance with the License. You can obtain a copy
443 in the file LICENSE in the source distribution or at
444 L<https://www.openssl.org/source/license.html>.