5 EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free,
6 EVP_MAC_is_a, EVP_MAC_number, EVP_MAC_names_do_all,
7 EVP_MAC_provider, EVP_MAC_get_params, EVP_MAC_gettable_params,
8 EVP_MAC_CTX, EVP_MAC_new_ctx, EVP_MAC_free_ctx, EVP_MAC_dup_ctx,
9 EVP_MAC_get_ctx_mac, EVP_MAC_get_ctx_params, EVP_MAC_set_ctx_params,
10 EVP_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(OPENSSL_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 void EVP_MAC_names_do_all(const EVP_MAC *mac,
28 void (*fn)(const char *name, void *data),
30 const OSSL_PROVIDER *EVP_MAC_provider(const EVP_MAC *mac);
31 int EVP_MAC_get_params(EVP_MAC *mac, OSSL_PARAM params[]);
33 EVP_MAC_CTX *EVP_MAC_new_ctx(EVP_MAC *mac);
34 void EVP_MAC_free_ctx(EVP_MAC_CTX *ctx);
35 EVP_MAC_CTX *EVP_MAC_dup_ctx(const EVP_MAC_CTX *src);
36 EVP_MAC *EVP_MAC_get_ctx_mac(EVP_MAC_CTX *ctx);
37 int EVP_MAC_get_ctx_params(EVP_MAC_CTX *ctx, OSSL_PARAM params[]);
38 int EVP_MAC_set_ctx_params(EVP_MAC_CTX *ctx, const OSSL_PARAM params[]);
40 size_t EVP_MAC_size(EVP_MAC_CTX *ctx);
41 int EVP_MAC_init(EVP_MAC_CTX *ctx);
42 int EVP_MAC_update(EVP_MAC_CTX *ctx, const unsigned char *data, size_t datalen);
43 int EVP_MAC_final(EVP_MAC_CTX *ctx,
44 unsigned char *out, size_t *outl, size_t outsize);
46 const OSSL_PARAM *EVP_MAC_gettable_params(const EVP_MAC *mac);
47 const OSSL_PARAM *EVP_MAC_gettable_ctx_params(const EVP_MAC *mac);
48 const OSSL_PARAM *EVP_MAC_settable_ctx_params(const EVP_MAC *mac);
50 void EVP_MAC_do_all_provided(OPENSSL_CTX *libctx,
51 void (*fn)(EVP_MAC *mac, void *arg),
56 These types and functions help the application to calculate MACs of
57 different types and with different underlying algorithms if there are
60 MACs are a bit complex insofar that some of them use other algorithms
61 for actual computation. HMAC uses a digest, and CMAC uses a cipher.
62 Therefore, there are sometimes two contexts to keep track of, one for
63 the MAC algorithm itself and one for the underlying computation
64 algorithm if there is one.
66 To make things less ambiguous, this manual talks about a "context" or
67 "MAC context", which is to denote the MAC level context, and about a
68 "underlying context", or "computation context", which is to denote the
69 context for the underlying computation algorithm if there is one.
73 B<EVP_MAC> is a type that holds the implementation of a MAC.
75 B<EVP_MAC_CTX> is a context type that holds internal MAC information
76 as well as a reference to a computation context, for those MACs that
77 rely on an underlying computation algorithm.
79 =head2 Algorithm implementation fetching
81 EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given
82 a library context I<libctx> and a set of I<properties>.
83 See L<provider(7)/Fetching algorithms> for further information.
85 See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list
86 of algorithms supported by the default provider.
88 The returned value must eventually be freed with
91 EVP_MAC_up_ref() increments the reference count of an already fetched
94 EVP_MAC_free() frees a fetched algorithm.
95 NULL is a valid parameter, for which this function is a no-op.
97 =head2 Context manipulation functions
99 EVP_MAC_new_ctx() creates a new context for the MAC type I<mac>.
100 The created context can then be used with most other functions
103 EVP_MAC_free_ctx() frees the contents of the context, including an
104 underlying context if there is one, as well as the context itself.
105 NULL is a valid parameter, for which this function is a no-op.
107 EVP_MAC_dup_ctx() duplicates the I<src> context and returns a newly allocated
110 EVP_MAC_get_ctx_mac() returns the B<EVP_MAC> associated with the context
113 =head2 Computing functions
115 EVP_MAC_init() sets up the underlying context with information given
116 through diverse controls.
117 This should be called before calling EVP_MAC_update() and
120 EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input.
122 EVP_MAC_final() does the final computation and stores the result in
123 the memory pointed at by I<out> of size I<outsize>, and sets the number
124 of bytes written in I<*outl> at.
125 If I<out> is NULL or I<outsize> is too small, then no computation
127 To figure out what the output length will be and allocate space for it
128 dynamically, simply call with I<out> being NULL and I<outl>
129 pointing at a valid location, then allocate space and make a second
130 call with I<out> pointing at the allocated space.
132 EVP_MAC_get_params() retrieves details about the implementation
134 The set of parameters given with I<params> determine exactly what
135 parameters should be retrieved.
136 Note that a parameter that is unknown in the underlying context is
139 EVP_MAC_get_ctx_params() retrieves chosen parameters, given the
140 context I<ctx> and its underlying context.
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_set_ctx_params() passes chosen parameters to the underlying
147 context, given a context I<ctx>.
148 The set of parameters given with I<params> determine exactly what
149 parameters are passed down.
150 Note that a parameter that is unknown in the underlying context is
152 Also, what happens when a needed parameter isn't passed down is
153 defined by the implementation.
155 EVP_MAC_gettable_params(), EVP_MAC_gettable_ctx_params() and
156 EVP_MAC_settable_ctx_params() get a constant B<OSSL_PARAM> array that
157 describes the retrievable and settable parameters, i.e. parameters that
158 can be used with EVP_MAC_get_params(), EVP_MAC_get_ctx_params()
159 and EVP_MAC_set_ctx_params(), respectively.
160 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
162 =head2 Information functions
164 EVP_MAC_size() returns the MAC output size for the given context.
166 EVP_MAC_is_a() checks if the given I<mac> is an implementation of an
167 algorithm that's identifiable with I<name>.
169 EVP_MAC_provider() returns the provider that holds the implementation
172 EVP_MAC_do_all_provided() traverses all MAC implemented by all activated
173 providers in the given library context I<libctx>, and for each of the
174 implementations, calls the given function I<fn> with the implementation method
175 and the given I<arg> as argument.
177 EVP_MAC_number() returns the internal dynamic number assigned to
180 EVP_MAC_names_do_all() traverses all names for I<mac>, and calls
181 I<fn> with each name and I<data>.
185 Parameters are identified by name as strings, and have an expected
186 data type and maximum size.
187 OpenSSL has a set of macros for parameter names it expects to see in
188 its own MAC implementations.
189 Here, we show all three, the OpenSSL macro for the parameter name, the
190 name in string form, and a type description.
192 The standard parameter names are:
196 =item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string>
198 Its value is the MAC key as an array of bytes.
200 For MACs that use an underlying computation algorithm, the algorithm
201 must be set first, see parameter names "algorithm" below.
203 =item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string>
205 Some MAC implementations require an IV, this parameter sets the IV.
207 =item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string>
209 Some MAC implementations (KMAC, BLAKE2) accept a Customization String,
210 this parameter sets the Customization String. The default value is the
213 =item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string>
215 This option is used by BLAKE2 MAC.
217 =item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer>
219 It's a simple flag, the value 0 or 1 are expected.
221 This option is used by KMAC.
223 =item "flags" (B<OSSL_MAC_PARAM_FLAGS>) <integer>
225 These will set the MAC flags to the given numbers.
226 Some MACs do not support this option.
228 =item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string>
230 =item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string>
232 =item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string>
234 For MAC implementations that use an underlying computation cipher or
235 digest, these parameters set what the algorithm should be.
237 The value is always the name of the intended algorithm,
240 Note that not all algorithms may support all digests.
241 HMAC does not support variable output length digests such as SHAKE128
244 =item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer>
246 For MAC implementations that support it, set the output size that
247 EVP_MAC_final() should produce.
248 The allowed sizes vary between MAC implementations, but must never exceed
249 what can be given with a B<size_t>.
253 All these parameters should be used before the calls to any of
254 EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full
256 Anything else may give undefined results.
260 EVP_MAC_fetch() returns a pointer to a newly fetched EVP_MAC, or
261 NULL if allocation failed.
263 EVP_MAC_up_ref() returns 1 on success, 0 on error.
265 EVP_MAC_free() returns nothing at all.
267 EVP_MAC_is_a() returns 1 if the given method can be identified with
268 the given name, otherwise 0.
270 EVP_MAC_provider() returns a pointer to the provider for the MAC, or
273 EVP_MAC_new_ctx() and EVP_MAC_dup_ctx() return a pointer to a newly
274 created EVP_MAC_CTX, or NULL if allocation failed.
276 EVP_MAC_free_ctx() returns nothing at all.
278 EVP_MAC_get_ctx_params() and EVP_MAC_set_ctx_params() return 1 on
281 EVP_MAC_init(), EVP_MAC_update(), and EVP_MAC_final() return 1 on success, 0
284 EVP_MAC_size() returns the expected output size, or 0 if it isn't
286 If it isn't set, a call to EVP_MAC_init() should get it set.
288 EVP_MAC_do_all_provided() returns nothing at all.
298 #include <openssl/evp.h>
299 #include <openssl/err.h>
300 #include <openssl/params.h>
303 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL);
304 const char *cipher = getenv("MY_MAC_CIPHER");
305 const char *digest = getenv("MY_MAC_DIGEST");
306 const char *key = getenv("MY_KEY");
307 EVP_MAC_CTX *ctx = NULL;
309 unsigned char buf[4096];
315 OSSL_PARAM params[4];
320 OSSL_PARAM_construct_utf8_string("cipher", cipher, 0;
323 OSSL_PARAM_construct_utf8_string("digest", digest, 0);
325 OSSL_PARAM_construct_octet_string("key", key, strlen(key));
326 params[params_n] = OSSL_PARAM_construct_end();
330 || (ctx = EVP_MAC_new_ctx(mac)) == NULL
331 || EVP_MAC_set_ctx_params(ctx, params) <= 0)
334 if (!EVP_MAC_init(ctx))
337 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) {
338 if (!EVP_MAC_update(ctx, buf, read_l))
342 if (!EVP_MAC_final(ctx, buf, &final_l))
346 for (i = 0; i < final_l; i++)
347 printf("%02X", buf[i]);
350 EVP_MAC_free_ctx(ctx);
355 EVP_MAC_free_ctx(ctx);
357 fprintf(stderr, "Something went wrong\n");
358 ERR_print_errors_fp(stderr);
362 A run of this program, called with correct environment variables, can
365 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \
366 LD_LIBRARY_PATH=. ./foo < foo.c
367 Result: C5C06683CD9DDEF904D754505C560A4E
369 (in this example, that program was stored in F<foo.c> and compiled to
376 L<EVP_MAC-BLAKE2(7)>,
381 L<EVP_MAC-Siphash(7)>,
382 L<EVP_MAC-Poly1305(7)>
386 These functions were added in OpenSSL 3.0.
390 Copyright 2018-2020 The OpenSSL Project Authors. All Rights Reserved.
392 Licensed under the Apache License 2.0 (the "License"). You may not use
393 this file except in compliance with the License. You can obtain a copy
394 in the file LICENSE in the source distribution or at
395 L<https://www.openssl.org/source/license.html>.