1=pod 2 3=head1 NAME 4 5EVP_MAC, EVP_MAC_fetch, EVP_MAC_up_ref, EVP_MAC_free, EVP_MAC_is_a, 6EVP_MAC_get0_name, EVP_MAC_names_do_all, EVP_MAC_get0_description, 7EVP_MAC_get0_provider, EVP_MAC_get_params, EVP_MAC_gettable_params, 8EVP_MAC_CTX, EVP_MAC_CTX_new, EVP_MAC_CTX_free, EVP_MAC_CTX_dup, 9EVP_MAC_CTX_get0_mac, EVP_MAC_CTX_get_params, EVP_MAC_CTX_set_params, 10EVP_MAC_CTX_get_mac_size, EVP_MAC_CTX_get_block_size, EVP_Q_mac, 11EVP_MAC_init, EVP_MAC_update, EVP_MAC_final, EVP_MAC_finalXOF, 12EVP_MAC_gettable_ctx_params, EVP_MAC_settable_ctx_params, 13EVP_MAC_CTX_gettable_params, EVP_MAC_CTX_settable_params, 14EVP_MAC_do_all_provided - EVP MAC routines 15 16=head1 SYNOPSIS 17 18 #include <openssl/evp.h> 19 20 typedef struct evp_mac_st EVP_MAC; 21 typedef struct evp_mac_ctx_st EVP_MAC_CTX; 22 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), 31 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[]); 35 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[]); 42 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); 56 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); 62 63 void EVP_MAC_do_all_provided(OSSL_LIB_CTX *libctx, 64 void (*fn)(EVP_MAC *mac, void *arg), 65 void *arg); 66 67=head1 DESCRIPTION 68 69These types and functions help the application to calculate MACs of 70different types and with different underlying algorithms if there are 71any. 72 73MACs are a bit complex insofar that some of them use other algorithms 74for actual computation. HMAC uses a digest, and CMAC uses a cipher. 75Therefore, there are sometimes two contexts to keep track of, one for 76the MAC algorithm itself and one for the underlying computation 77algorithm if there is one. 78 79To 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 82context for the underlying computation algorithm if there is one. 83 84=head2 Types 85 86B<EVP_MAC> is a type that holds the implementation of a MAC. 87 88B<EVP_MAC_CTX> is a context type that holds internal MAC information 89as well as a reference to a computation context, for those MACs that 90rely on an underlying computation algorithm. 91 92=head2 Algorithm implementation fetching 93 94EVP_MAC_fetch() fetches an implementation of a MAC I<algorithm>, given 95a library context I<libctx> and a set of I<properties>. 96See L<crypto(7)/ALGORITHM FETCHING> for further information. 97 98See L<OSSL_PROVIDER-default(7)/Message Authentication Code (MAC)> for the list 99of algorithms supported by the default provider. 100 101The returned value must eventually be freed with 102L<EVP_MAC_free(3)>. 103 104EVP_MAC_up_ref() increments the reference count of an already fetched 105MAC. 106 107EVP_MAC_free() frees a fetched algorithm. 108NULL is a valid parameter, for which this function is a no-op. 109 110=head2 Context manipulation functions 111 112EVP_MAC_CTX_new() creates a new context for the MAC type I<mac>. 113The created context can then be used with most other functions 114described here. 115 116EVP_MAC_CTX_free() frees the contents of the context, including an 117underlying context if there is one, as well as the context itself. 118NULL is a valid parameter, for which this function is a no-op. 119 120EVP_MAC_CTX_dup() duplicates the I<src> context and returns a newly allocated 121context. 122 123EVP_MAC_CTX_get0_mac() returns the B<EVP_MAC> associated with the context 124I<ctx>. 125 126=head2 Computing functions 127 128EVP_Q_mac() computes the message authentication code 129of I<data> with length I<datalen> 130using the MAC algorithm I<name> and the key I<key> with length I<keylen>. 131The MAC algorithm is fetched using any given I<libctx> and property query 132string I<propq>. It takes parameters I<subalg> and further I<params>, 133both of which may be NULL if not needed. 134If I<out> is not NULL, it places the result in the memory pointed at by I<out>, 135but only if I<outsize> is sufficient (otherwise no computation is made). 136If I<out> is NULL, it allocates and uses a buffer of suitable length, 137which will be returned on success and must be freed by the caller. 138In either case, also on error, 139it assigns the number of bytes written to I<*outlen> unless I<outlen> is NULL. 140 141EVP_MAC_init() sets up the underlying context I<ctx> with information given 142via the I<key> and I<params> arguments. The MAC I<key> has a length of 143I<keylen> and the parameters in I<params> are processed before setting 144the key. If I<key> is NULL, the key must be set via I<params> either 145as part of this call or separately using EVP_MAC_CTX_set_params(). 146Providing non-NULL I<params> to this function is equivalent to calling 147EVP_MAC_CTX_set_params() with those I<params> for the same I<ctx> beforehand. 148 149EVP_MAC_init() should be called before EVP_MAC_update() and EVP_MAC_final(). 150 151EVP_MAC_update() adds I<datalen> bytes from I<data> to the MAC input. 152 153EVP_MAC_final() does the final computation and stores the result in 154the memory pointed at by I<out> of size I<outsize>, and sets the number 155of bytes written in I<*outl> at. 156If I<out> is NULL or I<outsize> is too small, then no computation 157is made. 158To figure out what the output length will be and allocate space for it 159dynamically, simply call with I<out> being NULL and I<outl> 160pointing at a valid location, then allocate space and make a second 161call with I<out> pointing at the allocated space. 162 163EVP_MAC_finalXOF() does the final computation for an XOF based MAC and stores 164the result in the memory pointed at by I<out> of size I<outsize>. 165 166EVP_MAC_get_params() retrieves details about the implementation 167I<mac>. 168The set of parameters given with I<params> determine exactly what 169parameters should be retrieved. 170Note that a parameter that is unknown in the underlying context is 171simply ignored. 172 173EVP_MAC_CTX_get_params() retrieves chosen parameters, given the 174context I<ctx> and its underlying context. 175The set of parameters given with I<params> determine exactly what 176parameters should be retrieved. 177Note that a parameter that is unknown in the underlying context is 178simply ignored. 179 180EVP_MAC_CTX_set_params() passes chosen parameters to the underlying 181context, given a context I<ctx>. 182The set of parameters given with I<params> determine exactly what 183parameters are passed down. 184If I<params> are NULL, the unterlying context should do nothing and return 1. 185Note that a parameter that is unknown in the underlying context is 186simply ignored. 187Also, what happens when a needed parameter isn't passed down is 188defined by the implementation. 189 190EVP_MAC_gettable_params() returns an B<OSSL_PARAM> array that describes 191the retrievable and settable parameters. EVP_MAC_gettable_params() 192returns parameters that can be used with EVP_MAC_get_params(). 193See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor. 194 195EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params() 196return constant B<OSSL_PARAM> arrays that describe the retrievable 197parameters that can be used with EVP_MAC_CTX_get_params(). 198EVP_MAC_gettable_ctx_params() returns the parameters that can be retrieved 199from the algorithm, whereas EVP_MAC_CTX_gettable_params() returns 200the parameters that can be retrieved in the context's current state. 201See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor. 202 203EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return 204constant B<OSSL_PARAM> arrays that describe the settable parameters that 205can be used with EVP_MAC_CTX_set_params(). EVP_MAC_settable_ctx_params() 206returns the parameters that can be retrieved from the algorithm, 207whereas EVP_MAC_CTX_settable_params() returns the parameters that can 208be retrieved in the context's current state. See L<OSSL_PARAM(3)> 209for the use of B<OSSL_PARAM> as a parameter descriptor. 210 211=head2 Information functions 212 213EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context. 214 215EVP_MAC_CTX_get_block_size() returns the MAC block size for the given context. 216Not all MAC algorithms support this. 217 218EVP_MAC_is_a() checks if the given I<mac> is an implementation of an 219algorithm that's identifiable with I<name>. 220 221EVP_MAC_get0_provider() returns the provider that holds the implementation 222of the given I<mac>. 223 224EVP_MAC_do_all_provided() traverses all MAC implemented by all activated 225providers in the given library context I<libctx>, and for each of the 226implementations, calls the given function I<fn> with the implementation method 227and the given I<arg> as argument. 228 229EVP_MAC_get0_name() return the name of the given MAC. For fetched MACs 230with multiple names, only one of them is returned; it's 231recommended to use EVP_MAC_names_do_all() instead. 232 233EVP_MAC_names_do_all() traverses all names for I<mac>, and calls 234I<fn> with each name and I<data>. 235 236EVP_MAC_get0_description() returns a description of the I<mac>, meant 237for display and human consumption. The description is at the discretion 238of the mac implementation. 239 240=head1 PARAMETERS 241 242Parameters are identified by name as strings, and have an expected 243data type and maximum size. 244OpenSSL has a set of macros for parameter names it expects to see in 245its own MAC implementations. 246Here, we show all three, the OpenSSL macro for the parameter name, the 247name in string form, and a type description. 248 249The standard parameter names are: 250 251=over 4 252 253=item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string> 254 255Its value is the MAC key as an array of bytes. 256 257For MACs that use an underlying computation algorithm, the algorithm 258must be set first, see parameter names "algorithm" below. 259 260=item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string> 261 262Some MAC implementations (GMAC) require an IV, this parameter sets the IV. 263 264=item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string> 265 266Some MAC implementations (KMAC, BLAKE2) accept a Customization String, 267this parameter sets the Customization String. The default value is the 268empty string. 269 270=item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string> 271 272This option is used by BLAKE2 MAC. 273 274=item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer> 275 276It's a simple flag, the value 0 or 1 are expected. 277 278This option is used by KMAC. 279 280=item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer> 281 282A simple flag to set the MAC digest to not initialise the 283implementation specific data. The value 0 or 1 is expected. 284 285This option is used by HMAC. 286 287=item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer> 288 289A simple flag to set the MAC digest to be a oneshot operation. 290The value 0 or 1 is expected. 291 292This option is used by HMAC. 293 294=item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string> 295 296=item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string> 297 298=item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string> 299 300For MAC implementations that use an underlying computation cipher or 301digest, these parameters set what the algorithm should be. 302 303The value is always the name of the intended algorithm, 304or the properties. 305 306Note that not all algorithms may support all digests. 307HMAC does not support variable output length digests such as SHAKE128 308or SHAKE256. 309 310=item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer> 311 312For MAC implementations that support it, set the output size that 313EVP_MAC_final() should produce. 314The allowed sizes vary between MAC implementations, but must never exceed 315what can be given with a B<size_t>. 316 317=item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer> 318 319This parameter is only supported by HMAC. If set then special handling is 320activated for calculating the MAC of a received mac-then-encrypt TLS record 321where variable length record padding has been used (as in the case of CBC mode 322ciphersuites). The value represents the total length of the record that is 323having the MAC calculated including the received MAC and the record padding. 324 325When used EVP_MAC_update must be called precisely twice. The first time with 326the 13 bytes of TLS "header" data, and the second time with the entire record 327including the MAC itself and any padding. The entire record length must equal 328the value passed in the "tls-data-size" parameter. The length passed in the 329B<datalen> parameter to EVP_MAC_update() should be equal to the length of the 330record after the MAC and any padding has been removed. 331 332=back 333 334All these parameters should be used before the calls to any of 335EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full 336computation. 337Anything else may give undefined results. 338 339=head1 NOTES 340 341The MAC life-cycle is described in L<life_cycle-mac(7)>. In the future, 342the transitions described there will be enforced. When this is done, it will 343not be considered a breaking change to the API. 344 345The usage of the parameter names "custom", "iv" and "salt" correspond to 346the names used in the standard where the algorithm was defined. 347 348=head1 RETURN VALUES 349 350EVP_MAC_fetch() returns a pointer to a newly fetched B<EVP_MAC>, or 351NULL if allocation failed. 352 353EVP_MAC_up_ref() returns 1 on success, 0 on error. 354 355EVP_MAC_names_do_all() returns 1 if the callback was called for all names. A 356return value of 0 means that the callback was not called for any names. 357 358EVP_MAC_free() returns nothing at all. 359 360EVP_MAC_is_a() returns 1 if the given method can be identified with 361the given name, otherwise 0. 362 363EVP_MAC_get0_name() returns a name of the MAC, or NULL on error. 364 365EVP_MAC_get0_provider() returns a pointer to the provider for the MAC, or 366NULL on error. 367 368EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly 369created EVP_MAC_CTX, or NULL if allocation failed. 370 371EVP_MAC_CTX_free() returns nothing at all. 372 373EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on 374success, 0 on error. 375 376EVP_Q_mac() returns a pointer to the computed MAC value, or NULL on error. 377 378EVP_MAC_init(), EVP_MAC_update(), EVP_MAC_final(), and EVP_MAC_finalXOF() 379return 1 on success, 0 on error. 380 381EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't 382set. If it isn't set, a call to EVP_MAC_init() will set it. 383 384EVP_MAC_CTX_get_block_size() returns the block size, or 0 if it isn't set. 385If it isn't set, a call to EVP_MAC_init() will set it. 386 387EVP_MAC_do_all_provided() returns nothing at all. 388 389=head1 EXAMPLES 390 391 #include <stdlib.h> 392 #include <stdio.h> 393 #include <string.h> 394 #include <stdarg.h> 395 #include <unistd.h> 396 397 #include <openssl/evp.h> 398 #include <openssl/err.h> 399 #include <openssl/params.h> 400 401 int main() { 402 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL); 403 const char *cipher = getenv("MY_MAC_CIPHER"); 404 const char *digest = getenv("MY_MAC_DIGEST"); 405 const char *key = getenv("MY_KEY"); 406 EVP_MAC_CTX *ctx = NULL; 407 408 unsigned char buf[4096]; 409 size_t read_l; 410 size_t final_l; 411 412 size_t i; 413 414 OSSL_PARAM params[3]; 415 size_t params_n = 0; 416 417 if (cipher != NULL) 418 params[params_n++] = 419 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0); 420 if (digest != NULL) 421 params[params_n++] = 422 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0); 423 params[params_n] = OSSL_PARAM_construct_end(); 424 425 if (mac == NULL 426 || key == NULL 427 || (ctx = EVP_MAC_CTX_new(mac)) == NULL 428 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key), 429 params)) 430 goto err; 431 432 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) { 433 if (!EVP_MAC_update(ctx, buf, read_l)) 434 goto err; 435 } 436 437 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf))) 438 goto err; 439 440 printf("Result: "); 441 for (i = 0; i < final_l; i++) 442 printf("%02X", buf[i]); 443 printf("\n"); 444 445 EVP_MAC_CTX_free(ctx); 446 EVP_MAC_free(mac); 447 exit(0); 448 449 err: 450 EVP_MAC_CTX_free(ctx); 451 EVP_MAC_free(mac); 452 fprintf(stderr, "Something went wrong\n"); 453 ERR_print_errors_fp(stderr); 454 exit (1); 455 } 456 457A run of this program, called with correct environment variables, can 458look like this: 459 460 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \ 461 LD_LIBRARY_PATH=. ./foo < foo.c 462 Result: C5C06683CD9DDEF904D754505C560A4E 463 464(in this example, that program was stored in F<foo.c> and compiled to 465F<./foo>) 466 467=head1 SEE ALSO 468 469L<property(7)> 470L<OSSL_PARAM(3)>, 471L<EVP_MAC-BLAKE2(7)>, 472L<EVP_MAC-CMAC(7)>, 473L<EVP_MAC-GMAC(7)>, 474L<EVP_MAC-HMAC(7)>, 475L<EVP_MAC-KMAC(7)>, 476L<EVP_MAC-Siphash(7)>, 477L<EVP_MAC-Poly1305(7)>, 478L<provider-mac(7)>, 479L<life_cycle-mac(7)> 480 481=head1 HISTORY 482 483These functions were added in OpenSSL 3.0. 484 485=head1 COPYRIGHT 486 487Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved. 488 489Licensed under the Apache License 2.0 (the "License"). You may not use 490this file except in compliance with the License. You can obtain a copy 491in the file LICENSE in the source distribution or at 492L<https://www.openssl.org/source/license.html>. 493 494=cut 495