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_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 char *EVP_MAC_description(const EVP_MAC *mac);
33 const OSSL_PROVIDER *EVP_MAC_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_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 int EVP_MAC_init(EVP_MAC_CTX *ctx, const unsigned char *key, size_t keylen,
45 const OSSL_PARAM params[]);
46 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
47 int EVP_MAC_final(EVP_MAC_CTX *ctx,
48 unsigned char *out, size_t *outl, size_t outsize);
50 const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
51 const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
52 const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
53 const OSSL_PARAM *EVP_MAC_CTX_gettable_params(EVP_MAC_CTX *ctx);
54 const OSSL_PARAM *EVP_MAC_CTX_settable_params(EVP_MAC_CTX *ctx);
56 void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx,
57 void (*fn)(EVP_MAC *mac, void *arg),
62 These types and functions help the application to calculate MACs of
63 different types and with different underlying algorithms if there are
66 MACs are a bit complex insofar that some of them use other algorithms
67 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
68 Therefore, there are sometimes two contexts to keep track of, one for
69 the MAC algorithm itself and one for the underlying computation
70 algorithm if there is one.
72 To make things less ambiguous, this manual talks about a "context" or
73 "MAC context", which is to denote the MAC level context, and about a
74 "underlying context", or "computation context", which is to denote the
75 context for the underlying computation algorithm if there is one.
79 B<EVP_MAC> is a type that holds the implementation of a MAC.
81 B<EVP_MAC_CTX> is a context type that holds internal MAC information
82 as well as a reference to a computation context, for those MACs that
83 rely on an underlying computation algorithm.
85 =head2 Algorithm implementation fetching
87 EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given
88 a library context I<libctx> and a set of I<properties>.
89 See L<provider(7)/Fetching algorithms> for further information.
91 See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list
92 of algorithms supported by the default provider.
94 The returned value must eventually be freed with
97 EVP_MAC_up_ref() increments the reference count of an already fetched
100 EVP_MAC_free() frees a fetched algorithm.
101 NULL is a valid parameter, for which this function is a no-op.
103 =head2 Context manipulation functions
105 EVP_MAC_CTX_new() creates a new context for the MAC type I<mac>.
106 The created context can then be used with most other functions
109 EVP_MAC_CTX_free() frees the contents of the context, including an
110 underlying context if there is one, as well as the context itself.
111 NULL is a valid parameter, for which this function is a no-op.
113 EVP_MAC_CTX_dup() duplicates the I<src> context and returns a newly allocated
116 EVP_MAC_CTX_mac() returns the B<EVP_MAC> associated with the context
119 =head2 Computing functions
121 EVP_MAC_init() sets up the underlying context with information given
122 via the I<key> and I<params> arguments. The MAC I<key> has a length of
123 I<keylen> and the parameters in I<params> are processed before setting
124 the key. If I<key> is NULL, the key must be set via params either
125 as part of this call or separately using EVP_MAC_CTX_set_params().
126 This should be called before calling EVP_MAC_update() and EVP_MAC_final().
128 EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input.
130 EVP_MAC_final() does the final computation and stores the result in
131 the memory pointed at by I<out> of size I<outsize>, and sets the number
132 of bytes written in I<*outl> at.
133 If I<out> is NULL or I<outsize> is too small, then no computation
135 To figure out what the output length will be and allocate space for it
136 dynamically, simply call with I<out> being NULL and I<outl>
137 pointing at a valid location, then allocate space and make a second
138 call with I<out> pointing at the allocated space.
140 EVP_MAC_get_params() retrieves details about the implementation
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_get_params() retrieves chosen parameters, given the
148 context I<ctx> and its underlying context.
149 The set of parameters given with I<params> determine exactly what
150 parameters should be retrieved.
151 Note that a parameter that is unknown in the underlying context is
154 EVP_MAC_CTX_set_params() passes chosen parameters to the underlying
155 context, given a context I<ctx>.
156 The set of parameters given with I<params> determine exactly what
157 parameters are passed down.
158 Note that a parameter that is unknown in the underlying context is
160 Also, what happens when a needed parameter isn't passed down is
161 defined by the implementation.
163 EVP_MAC_gettable_params() returns an B<OSSL_PARAM> array that describes
164 the retrievable and settable parameters. EVP_MAC_gettable_params()
165 returns parameters that can be used with EVP_MAC_get_params().
166 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor.
168 EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params()
169 return constant B<OSSL_PARAM> arrays that describe the retrievable
170 parameters that can be used with EVP_MAC_CTX_get_params().
171 EVP_MAC_gettable_ctx_params() returns the parameters that can be retrieved
172 from the algorithm, whereas EVP_MAC_CTX_gettable_params() returns
173 the parameters that can be retrieved in the context's current state.
174 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor.
176 EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return
177 constant B<OSSL_PARAM> arrays that describe the settable parameters that
178 can be used with EVP_MAC_CTX_set_params(). EVP_MAC_settable_ctx_params()
179 returns the parameters that can be retrieved from the algorithm,
180 whereas EVP_MAC_CTX_settable_params() returns the parameters that can
181 be retrieved in the context's current state. See L<OSSL_PARAM(3)>
182 for the use of B<OSSL_PARAM> as a parameter descriptor.
184 =head2 Information functions
186 EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context.
188 EVP_MAC_is_a() checks if the given I<mac> is an implementation of an
189 algorithm that's identifiable with I<name>.
191 EVP_MAC_provider() returns the provider that holds the implementation
194 EVP_MAC_do_all_provided() traverses all MAC implemented by all activated
195 providers in the given library context I<libctx>, and for each of the
196 implementations, calls the given function I<fn> with the implementation method
197 and the given I<arg> as argument.
199 EVP_MAC_number() returns the internal dynamic number assigned to
202 EVP_MAC_name() return the name of the given MAC. For fetched MACs
203 with multiple names, only one of them is returned; it's
204 recommended to use EVP_MAC_names_do_all() instead.
206 EVP_MAC_names_do_all() traverses all names for I<mac>, and calls
207 I<fn> with each name and I<data>.
209 EVP_MAC_description() returns a description of the I<mac>, meant for display
210 and human consumption. The description is at the discretion of the mac
215 Parameters are identified by name as strings, and have an expected
216 data type and maximum size.
217 OpenSSL has a set of macros for parameter names it expects to see in
218 its own MAC implementations.
219 Here, we show all three, the OpenSSL macro for the parameter name, the
220 name in string form, and a type description.
222 The standard parameter names are:
226 =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
228 Its value is the MAC key as an array of bytes.
230 For MACs that use an underlying computation algorithm, the algorithm
231 must be set first, see parameter names "algorithm" below.
233 =item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string>
235 Some MAC implementations require an IV, this parameter sets the IV.
237 =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
239 Some MAC implementations (KMAC, BLAKE2) accept a Customization String,
240 this parameter sets the Customization String. The default value is the
243 =item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string>
245 This option is used by BLAKE2 MAC.
247 =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
249 It's a simple flag, the value 0 or 1 are expected.
251 This option is used by KMAC.
253 =item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer>
255 A simple flag to set the MAC digest to not initialise the
256 implementation specific data. The value 0 or 1 is expected.
258 This option is used by HMAC.
260 =item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer>
262 A simple flag to set the MAC digest to be a oneshot operation.
263 The value 0 or 1 is expected.
265 This option is used by HMAC.
267 =item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string>
269 =item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string>
271 =item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string>
273 For MAC implementations that use an underlying computation cipher or
274 digest, these parameters set what the algorithm should be.
276 The value is always the name of the intended algorithm,
279 Note that not all algorithms may support all digests.
280 HMAC does not support variable output length digests such as SHAKE128
283 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
285 For MAC implementations that support it, set the output size that
286 EVP_MAC_final() should produce.
287 The allowed sizes vary between MAC implementations, but must never exceed
288 what can be given with a B<size_t>.
290 =item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer>
292 This parameter is only supported by HMAC. If set then special handling is
293 activated for calculating the MAC of a received mac-then-encrypt TLS record
294 where variable length record padding has been used (as in the case of CBC mode
295 ciphersuites). The value represents the total length of the record that is
296 having the MAC calculated including the received MAC and the record padding.
298 When used EVP_MAC_update must be called precisely twice. The first time with
299 the 13 bytes of TLS "header" data, and the second time with the entire record
300 including the MAC itself and any padding. The entire record length must equal
301 the value passed in the "tls-data-size" parameter. The length passed in the
302 B<datalen> parameter to EVP_MAC_update() should be equal to the length of the
303 record after the MAC and any padding has been removed.
307 All these parameters should be used before the calls to any of
308 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
310 Anything else may give undefined results.
314 The MAC life-cycle is described in L<life_cycle-mac(7)>. In the future,
315 the transitions described there will be enforced. When this is done, it will
316 not be considered a breaking change to the API.
321 EVP_MAC_fetch() returns a pointer to a newly fetched EVP_MAC, or
322 NULL if allocation failed.
324 EVP_MAC_up_ref() returns 1 on success, 0 on error.
326 EVP_MAC_names_do_all() returns 1 if the callback was called for all names. A
327 return value of 0 means that the callback was not called for any names.
329 EVP_MAC_free() returns nothing at all.
331 EVP_MAC_is_a() returns 1 if the given method can be identified with
332 the given name, otherwise 0.
334 EVP_MAC_name() returns a name of the MAC, or NULL on error.
336 EVP_MAC_provider() returns a pointer to the provider for the MAC, or
339 EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly
340 created EVP_MAC_CTX, or NULL if allocation failed.
342 EVP_MAC_CTX_free() returns nothing at all.
344 EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on
347 EVP_MAC_init(), EVP_MAC_update(), and EVP_MAC_final() return 1 on success, 0
350 EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't set.
351 If it isn't set, a call to EVP_MAC_init() should get it set.
353 EVP_MAC_do_all_provided() returns nothing at all.
363 #include <openssl/evp.h>
364 #include <openssl/err.h>
365 #include <openssl/params.h>
368 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
369 const char *cipher = getenv("MY_MAC_CIPHER");
370 const char *digest = getenv("MY_MAC_DIGEST");
371 const char *key = getenv("MY_KEY");
372 EVP_MAC_CTX *ctx = NULL;
374 unsigned char buf[4096];
380 OSSL_PARAM params[3];
385 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0);
388 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0);
389 params[params_n] = OSSL_PARAM_construct_end();
393 || (ctx = EVP_MAC_CTX_new(mac)) == NULL
394 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key),
398 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
399 if (!EVP_MAC_update(ctx, buf, read_l))
403 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf)))
407 for (i = 0; i < final_l; i++)
408 printf("%02X", buf[i]);
411 EVP_MAC_CTX_free(ctx);
416 EVP_MAC_CTX_free(ctx);
418 fprintf(stderr, "Something went wrong\n");
419 ERR_print_errors_fp(stderr);
423 A run of this program, called with correct environment variables, can
426 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
427 LD_LIBRARY_PATH=. ./foo < foo.c
428 Result: C5C06683CD9DDEF904D754505C560A4E
430 (in this example, that program was stored in F<foo.c> and compiled to
437 L<EVP_MAC-BLAKE2(7)>,
442 L<EVP_MAC-Siphash(7)>,
443 L<EVP_MAC-Poly1305(7)>,
449 These functions were added in OpenSSL 3.0.
453 Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved.
455 Licensed under the Apache License 2.0 (the "License"). You may not use
456 this file except in compliance with the License. You can obtain a copy
457 in the file LICENSE in the source distribution or at
458 L<https://www.openssl.org/source/license.html>.