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 L<OSSL_PARAM(3)> array that describes 191the retrievable and settable parameters. EVP_MAC_gettable_params() 192returns parameters that can be used with EVP_MAC_get_params(). 193 194EVP_MAC_gettable_ctx_params() and EVP_MAC_CTX_gettable_params() 195return constant L<OSSL_PARAM(3)> arrays that describe the retrievable 196parameters that can be used with EVP_MAC_CTX_get_params(). 197EVP_MAC_gettable_ctx_params() returns the parameters that can be retrieved 198from the algorithm, whereas EVP_MAC_CTX_gettable_params() returns 199the parameters that can be retrieved in the context's current state. 200 201EVP_MAC_settable_ctx_params() and EVP_MAC_CTX_settable_params() return 202constant L<OSSL_PARAM(3)> arrays that describe the settable parameters that 203can be used with EVP_MAC_CTX_set_params(). EVP_MAC_settable_ctx_params() 204returns the parameters that can be retrieved from the algorithm, 205whereas EVP_MAC_CTX_settable_params() returns the parameters that can 206be retrieved in the context's current state. 207 208=head2 Information functions 209 210EVP_MAC_CTX_get_mac_size() returns the MAC output size for the given context. 211 212EVP_MAC_CTX_get_block_size() returns the MAC block size for the given context. 213Not all MAC algorithms support this. 214 215EVP_MAC_is_a() checks if the given I<mac> is an implementation of an 216algorithm that's identifiable with I<name>. 217 218EVP_MAC_get0_provider() returns the provider that holds the implementation 219of the given I<mac>. 220 221EVP_MAC_do_all_provided() traverses all MAC implemented by all activated 222providers in the given library context I<libctx>, and for each of the 223implementations, calls the given function I<fn> with the implementation method 224and the given I<arg> as argument. 225 226EVP_MAC_get0_name() return the name of the given MAC. For fetched MACs 227with multiple names, only one of them is returned; it's 228recommended to use EVP_MAC_names_do_all() instead. 229 230EVP_MAC_names_do_all() traverses all names for I<mac>, and calls 231I<fn> with each name and I<data>. 232 233EVP_MAC_get0_description() returns a description of the I<mac>, meant 234for display and human consumption. The description is at the discretion 235of the mac implementation. 236 237=head1 PARAMETERS 238 239Parameters are identified by name as strings, and have an expected 240data type and maximum size. 241OpenSSL has a set of macros for parameter names it expects to see in 242its own MAC implementations. 243Here, we show all three, the OpenSSL macro for the parameter name, the 244name in string form, and a type description. 245 246The standard parameter names are: 247 248=over 4 249 250=item "key" (B<OSSL_MAC_PARAM_KEY>) <octet string> 251 252Its value is the MAC key as an array of bytes. 253 254For MACs that use an underlying computation algorithm, the algorithm 255must be set first, see parameter names "algorithm" below. 256 257=item "iv" (B<OSSL_MAC_PARAM_IV>) <octet string> 258 259Some MAC implementations (GMAC) require an IV, this parameter sets the IV. 260 261=item "custom" (B<OSSL_MAC_PARAM_CUSTOM>) <octet string> 262 263Some MAC implementations (KMAC, BLAKE2) accept a Customization String, 264this parameter sets the Customization String. The default value is the 265empty string. 266 267=item "salt" (B<OSSL_MAC_PARAM_SALT>) <octet string> 268 269This option is used by BLAKE2 MAC. 270 271=item "xof" (B<OSSL_MAC_PARAM_XOF>) <integer> 272 273It's a simple flag, the value 0 or 1 are expected. 274 275This option is used by KMAC. 276 277=item "digest-noinit" (B<OSSL_MAC_PARAM_DIGEST_NOINIT>) <integer> 278 279A simple flag to set the MAC digest to not initialise the 280implementation specific data. The value 0 or 1 is expected. 281 282This option is used by HMAC. 283 284=item "digest-oneshot" (B<OSSL_MAC_PARAM_DIGEST_ONESHOT>) <integer> 285 286A simple flag to set the MAC digest to be a oneshot operation. 287The value 0 or 1 is expected. 288 289This option is used by HMAC. 290 291=item "properties" (B<OSSL_MAC_PARAM_PROPERTIES>) <UTF8 string> 292 293=item "digest" (B<OSSL_MAC_PARAM_DIGEST>) <UTF8 string> 294 295=item "cipher" (B<OSSL_MAC_PARAM_CIPHER>) <UTF8 string> 296 297For MAC implementations that use an underlying computation cipher or 298digest, these parameters set what the algorithm should be. 299 300The value is always the name of the intended algorithm, 301or the properties. 302 303Note that not all algorithms may support all digests. 304HMAC does not support variable output length digests such as SHAKE128 305or SHAKE256. 306 307=item "size" (B<OSSL_MAC_PARAM_SIZE>) <unsigned integer> 308 309For MAC implementations that support it, set the output size that 310EVP_MAC_final() should produce. 311The allowed sizes vary between MAC implementations, but must never exceed 312what can be given with a B<size_t>. 313 314=item "tls-data-size" (B<OSSL_MAC_PARAM_TLS_DATA_SIZE>) <unsigned integer> 315 316This parameter is only supported by HMAC. If set then special handling is 317activated for calculating the MAC of a received mac-then-encrypt TLS record 318where variable length record padding has been used (as in the case of CBC mode 319ciphersuites). The value represents the total length of the record that is 320having the MAC calculated including the received MAC and the record padding. 321 322When used EVP_MAC_update must be called precisely twice. The first time with 323the 13 bytes of TLS "header" data, and the second time with the entire record 324including the MAC itself and any padding. The entire record length must equal 325the value passed in the "tls-data-size" parameter. The length passed in the 326B<datalen> parameter to EVP_MAC_update() should be equal to the length of the 327record after the MAC and any padding has been removed. 328 329=back 330 331All these parameters should be used before the calls to any of 332EVP_MAC_init(), EVP_MAC_update() and EVP_MAC_final() for a full 333computation. 334Anything else may give undefined results. 335 336=head1 NOTES 337 338The MAC life-cycle is described in L<life_cycle-mac(7)>. In the future, 339the transitions described there will be enforced. When this is done, it will 340not be considered a breaking change to the API. 341 342The usage of the parameter names "custom", "iv" and "salt" correspond to 343the names used in the standard where the algorithm was defined. 344 345=head1 RETURN VALUES 346 347EVP_MAC_fetch() returns a pointer to a newly fetched B<EVP_MAC>, or 348NULL if allocation failed. 349 350EVP_MAC_up_ref() returns 1 on success, 0 on error. 351 352EVP_MAC_names_do_all() returns 1 if the callback was called for all names. A 353return value of 0 means that the callback was not called for any names. 354 355EVP_MAC_free() returns nothing at all. 356 357EVP_MAC_is_a() returns 1 if the given method can be identified with 358the given name, otherwise 0. 359 360EVP_MAC_get0_name() returns a name of the MAC, or NULL on error. 361 362EVP_MAC_get0_provider() returns a pointer to the provider for the MAC, or 363NULL on error. 364 365EVP_MAC_CTX_new() and EVP_MAC_CTX_dup() return a pointer to a newly 366created EVP_MAC_CTX, or NULL if allocation failed. 367 368EVP_MAC_CTX_free() returns nothing at all. 369 370EVP_MAC_CTX_get_params() and EVP_MAC_CTX_set_params() return 1 on 371success, 0 on error. 372 373EVP_Q_mac() returns a pointer to the computed MAC value, or NULL on error. 374 375EVP_MAC_init(), EVP_MAC_update(), EVP_MAC_final(), and EVP_MAC_finalXOF() 376return 1 on success, 0 on error. 377 378EVP_MAC_CTX_get_mac_size() returns the expected output size, or 0 if it isn't 379set. If it isn't set, a call to EVP_MAC_init() will set it. 380 381EVP_MAC_CTX_get_block_size() returns the block size, or 0 if it isn't set. 382If it isn't set, a call to EVP_MAC_init() will set it. 383 384EVP_MAC_do_all_provided() returns nothing at all. 385 386=head1 EXAMPLES 387 388 #include <stdlib.h> 389 #include <stdio.h> 390 #include <string.h> 391 #include <stdarg.h> 392 #include <unistd.h> 393 394 #include <openssl/evp.h> 395 #include <openssl/err.h> 396 #include <openssl/params.h> 397 398 int main() { 399 EVP_MAC *mac = EVP_MAC_fetch(NULL, getenv("MY_MAC"), NULL); 400 const char *cipher = getenv("MY_MAC_CIPHER"); 401 const char *digest = getenv("MY_MAC_DIGEST"); 402 const char *key = getenv("MY_KEY"); 403 EVP_MAC_CTX *ctx = NULL; 404 405 unsigned char buf[4096]; 406 size_t read_l; 407 size_t final_l; 408 409 size_t i; 410 411 OSSL_PARAM params[3]; 412 size_t params_n = 0; 413 414 if (cipher != NULL) 415 params[params_n++] = 416 OSSL_PARAM_construct_utf8_string("cipher", (char*)cipher, 0); 417 if (digest != NULL) 418 params[params_n++] = 419 OSSL_PARAM_construct_utf8_string("digest", (char*)digest, 0); 420 params[params_n] = OSSL_PARAM_construct_end(); 421 422 if (mac == NULL 423 || key == NULL 424 || (ctx = EVP_MAC_CTX_new(mac)) == NULL 425 || !EVP_MAC_init(ctx, (const unsigned char *)key, strlen(key), 426 params)) 427 goto err; 428 429 while ( (read_l = read(STDIN_FILENO, buf, sizeof(buf))) > 0) { 430 if (!EVP_MAC_update(ctx, buf, read_l)) 431 goto err; 432 } 433 434 if (!EVP_MAC_final(ctx, buf, &final_l, sizeof(buf))) 435 goto err; 436 437 printf("Result: "); 438 for (i = 0; i < final_l; i++) 439 printf("%02X", buf[i]); 440 printf("\n"); 441 442 EVP_MAC_CTX_free(ctx); 443 EVP_MAC_free(mac); 444 exit(0); 445 446 err: 447 EVP_MAC_CTX_free(ctx); 448 EVP_MAC_free(mac); 449 fprintf(stderr, "Something went wrong\n"); 450 ERR_print_errors_fp(stderr); 451 exit (1); 452 } 453 454A run of this program, called with correct environment variables, can 455look like this: 456 457 $ MY_MAC=cmac MY_KEY=secret0123456789 MY_MAC_CIPHER=aes-128-cbc \ 458 LD_LIBRARY_PATH=. ./foo < foo.c 459 Result: C5C06683CD9DDEF904D754505C560A4E 460 461(in this example, that program was stored in F<foo.c> and compiled to 462F<./foo>) 463 464=head1 SEE ALSO 465 466L<property(7)> 467L<OSSL_PARAM(3)>, 468L<EVP_MAC-BLAKE2(7)>, 469L<EVP_MAC-CMAC(7)>, 470L<EVP_MAC-GMAC(7)>, 471L<EVP_MAC-HMAC(7)>, 472L<EVP_MAC-KMAC(7)>, 473L<EVP_MAC-Siphash(7)>, 474L<EVP_MAC-Poly1305(7)>, 475L<provider-mac(7)>, 476L<life_cycle-mac(7)> 477 478=head1 HISTORY 479 480These functions were added in OpenSSL 3.0. 481 482=head1 COPYRIGHT 483 484Copyright 2018-2021 The OpenSSL Project Authors. All Rights Reserved. 485 486Licensed under the Apache License 2.0 (the "License"). You may not use 487this file except in compliance with the License. You can obtain a copy 488in the file LICENSE in the source distribution or at 489L<https://www.openssl.org/source/license.html>. 490 491=cut 492