1=pod 2 3=head1 NAME 4 5EVP_MD_fetch, EVP_MD_up_ref, EVP_MD_free, 6EVP_MD_get_params, EVP_MD_gettable_params, 7EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_copy, 8EVP_MD_CTX_copy_ex, EVP_MD_CTX_ctrl, 9EVP_MD_CTX_set_params, EVP_MD_CTX_get_params, 10EVP_MD_settable_ctx_params, EVP_MD_gettable_ctx_params, 11EVP_MD_CTX_settable_params, EVP_MD_CTX_gettable_params, 12EVP_MD_CTX_set_flags, EVP_MD_CTX_clear_flags, EVP_MD_CTX_test_flags, 13EVP_Q_digest, EVP_Digest, EVP_DigestInit_ex2, EVP_DigestInit_ex, EVP_DigestInit, 14EVP_DigestUpdate, EVP_DigestFinal_ex, EVP_DigestFinalXOF, EVP_DigestFinal, 15EVP_MD_is_a, EVP_MD_get0_name, EVP_MD_get0_description, 16EVP_MD_names_do_all, EVP_MD_get0_provider, EVP_MD_get_type, 17EVP_MD_get_pkey_type, EVP_MD_get_size, EVP_MD_get_block_size, EVP_MD_get_flags, 18EVP_MD_CTX_get0_name, EVP_MD_CTX_md, EVP_MD_CTX_get0_md, EVP_MD_CTX_get1_md, 19EVP_MD_CTX_get_type, EVP_MD_CTX_get_size, EVP_MD_CTX_get_block_size, 20EVP_MD_CTX_get0_md_data, EVP_MD_CTX_update_fn, EVP_MD_CTX_set_update_fn, 21EVP_md_null, 22EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj, 23EVP_MD_CTX_get_pkey_ctx, EVP_MD_CTX_set_pkey_ctx, 24EVP_MD_do_all_provided, 25EVP_MD_type, EVP_MD_nid, EVP_MD_name, EVP_MD_pkey_type, EVP_MD_size, 26EVP_MD_block_size, EVP_MD_flags, EVP_MD_CTX_size, EVP_MD_CTX_block_size, 27EVP_MD_CTX_type, EVP_MD_CTX_pkey_ctx, EVP_MD_CTX_md_data 28- EVP digest routines 29 30=head1 SYNOPSIS 31 32 #include <openssl/evp.h> 33 34 EVP_MD *EVP_MD_fetch(OSSL_LIB_CTX *ctx, const char *algorithm, 35 const char *properties); 36 int EVP_MD_up_ref(EVP_MD *md); 37 void EVP_MD_free(EVP_MD *md); 38 int EVP_MD_get_params(const EVP_MD *digest, OSSL_PARAM params[]); 39 const OSSL_PARAM *EVP_MD_gettable_params(const EVP_MD *digest); 40 EVP_MD_CTX *EVP_MD_CTX_new(void); 41 int EVP_MD_CTX_reset(EVP_MD_CTX *ctx); 42 void EVP_MD_CTX_free(EVP_MD_CTX *ctx); 43 void EVP_MD_CTX_ctrl(EVP_MD_CTX *ctx, int cmd, int p1, void* p2); 44 int EVP_MD_CTX_get_params(EVP_MD_CTX *ctx, OSSL_PARAM params[]); 45 int EVP_MD_CTX_set_params(EVP_MD_CTX *ctx, const OSSL_PARAM params[]); 46 const OSSL_PARAM *EVP_MD_settable_ctx_params(const EVP_MD *md); 47 const OSSL_PARAM *EVP_MD_gettable_ctx_params(const EVP_MD *md); 48 const OSSL_PARAM *EVP_MD_CTX_settable_params(EVP_MD_CTX *ctx); 49 const OSSL_PARAM *EVP_MD_CTX_gettable_params(EVP_MD_CTX *ctx); 50 void EVP_MD_CTX_set_flags(EVP_MD_CTX *ctx, int flags); 51 void EVP_MD_CTX_clear_flags(EVP_MD_CTX *ctx, int flags); 52 int EVP_MD_CTX_test_flags(const EVP_MD_CTX *ctx, int flags); 53 54 int EVP_Q_digest(OSSL_LIB_CTX *libctx, const char *name, const char *propq, 55 const void *data, size_t datalen, 56 unsigned char *md, size_t *mdlen); 57 int EVP_Digest(const void *data, size_t count, unsigned char *md, 58 unsigned int *size, const EVP_MD *type, ENGINE *impl); 59 int EVP_DigestInit_ex2(EVP_MD_CTX *ctx, const EVP_MD *type, 60 const OSSL_PARAM params[]); 61 int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); 62 int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); 63 int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s); 64 int EVP_DigestFinalXOF(EVP_MD_CTX *ctx, unsigned char *md, size_t len); 65 66 int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out, const EVP_MD_CTX *in); 67 68 int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type); 69 int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s); 70 71 int EVP_MD_CTX_copy(EVP_MD_CTX *out, EVP_MD_CTX *in); 72 73 const char *EVP_MD_get0_name(const EVP_MD *md); 74 const char *EVP_MD_get0_description(const EVP_MD *md); 75 int EVP_MD_is_a(const EVP_MD *md, const char *name); 76 int EVP_MD_names_do_all(const EVP_MD *md, 77 void (*fn)(const char *name, void *data), 78 void *data); 79 const OSSL_PROVIDER *EVP_MD_get0_provider(const EVP_MD *md); 80 int EVP_MD_get_type(const EVP_MD *md); 81 int EVP_MD_get_pkey_type(const EVP_MD *md); 82 int EVP_MD_get_size(const EVP_MD *md); 83 int EVP_MD_get_block_size(const EVP_MD *md); 84 unsigned long EVP_MD_get_flags(const EVP_MD *md); 85 86 const EVP_MD *EVP_MD_CTX_get0_md(const EVP_MD_CTX *ctx); 87 EVP_MD *EVP_MD_CTX_get1_md(EVP_MD_CTX *ctx); 88 const char *EVP_MD_CTX_get0_name(const EVP_MD_CTX *ctx); 89 int EVP_MD_CTX_get_size(const EVP_MD_CTX *ctx); 90 int EVP_MD_CTX_get_block_size(const EVP_MD_CTX *ctx); 91 int EVP_MD_CTX_get_type(const EVP_MD_CTX *ctx); 92 void *EVP_MD_CTX_get0_md_data(const EVP_MD_CTX *ctx); 93 94 const EVP_MD *EVP_md_null(void); 95 96 const EVP_MD *EVP_get_digestbyname(const char *name); 97 const EVP_MD *EVP_get_digestbynid(int type); 98 const EVP_MD *EVP_get_digestbyobj(const ASN1_OBJECT *o); 99 100 EVP_PKEY_CTX *EVP_MD_CTX_get_pkey_ctx(const EVP_MD_CTX *ctx); 101 void EVP_MD_CTX_set_pkey_ctx(EVP_MD_CTX *ctx, EVP_PKEY_CTX *pctx); 102 103 void EVP_MD_do_all_provided(OSSL_LIB_CTX *libctx, 104 void (*fn)(EVP_MD *mac, void *arg), 105 void *arg); 106 107 #define EVP_MD_type EVP_MD_get_type 108 #define EVP_MD_nid EVP_MD_get_type 109 #define EVP_MD_name EVP_MD_get0_name 110 #define EVP_MD_pkey_type EVP_MD_get_pkey_type 111 #define EVP_MD_size EVP_MD_get_size 112 #define EVP_MD_block_size EVP_MD_get_block_size 113 #define EVP_MD_flags EVP_MD_get_flags 114 #define EVP_MD_CTX_size EVP_MD_CTX_get_size 115 #define EVP_MD_CTX_block_size EVP_MD_CTX_get_block_size 116 #define EVP_MD_CTX_type EVP_MD_CTX_get_type 117 #define EVP_MD_CTX_pkey_ctx EVP_MD_CTX_get_pkey_ctx 118 #define EVP_MD_CTX_md_data EVP_MD_CTX_get0_md_data 119 120The following functions have been deprecated since OpenSSL 3.0, and can be 121hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value, 122see L<openssl_user_macros(7)>: 123 124 const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx); 125 126 int (*EVP_MD_CTX_update_fn(EVP_MD_CTX *ctx))(EVP_MD_CTX *ctx, 127 const void *data, size_t count); 128 129 void EVP_MD_CTX_set_update_fn(EVP_MD_CTX *ctx, 130 int (*update)(EVP_MD_CTX *ctx, 131 const void *data, size_t count)); 132 133=head1 DESCRIPTION 134 135The EVP digest routines are a high-level interface to message digests, 136and should be used instead of the digest-specific functions. 137 138The B<EVP_MD> type is a structure for digest method implementation. 139 140=over 4 141 142=item EVP_MD_fetch() 143 144Fetches the digest implementation for the given I<algorithm> from any 145provider offering it, within the criteria given by the I<properties>. 146See L<crypto(7)/ALGORITHM FETCHING> for further information. 147 148The returned value must eventually be freed with EVP_MD_free(). 149 150Fetched B<EVP_MD> structures are reference counted. 151 152=item EVP_MD_up_ref() 153 154Increments the reference count for an B<EVP_MD> structure. 155 156=item EVP_MD_free() 157 158Decrements the reference count for the fetched B<EVP_MD> structure. 159If the reference count drops to 0 then the structure is freed. 160 161=item EVP_MD_CTX_new() 162 163Allocates and returns a digest context. 164 165=item EVP_MD_CTX_reset() 166 167Resets the digest context I<ctx>. This can be used to reuse an already 168existing context. 169 170=item EVP_MD_CTX_free() 171 172Cleans up digest context I<ctx> and frees up the space allocated to it. 173 174=item EVP_MD_CTX_ctrl() 175 176I<This is a legacy method. EVP_MD_CTX_set_params() and EVP_MD_CTX_get_params() 177is the mechanism that should be used to set and get parameters that are used by 178providers.> 179 180Performs digest-specific control actions on context I<ctx>. The control command 181is indicated in I<cmd> and any additional arguments in I<p1> and I<p2>. 182EVP_MD_CTX_ctrl() must be called after EVP_DigestInit_ex2(). Other restrictions 183may apply depending on the control type and digest implementation. 184 185If this function happens to be used with a fetched B<EVP_MD>, it will 186translate the controls that are known to OpenSSL into L<OSSL_PARAM(3)> 187parameters with keys defined by OpenSSL and call EVP_MD_CTX_get_params() or 188EVP_MD_CTX_set_params() as is appropriate for each control command. 189 190See L</CONTROLS> below for more information, including what translations are 191being done. 192 193=item EVP_MD_get_params() 194 195Retrieves the requested list of I<params> from a MD I<md>. 196See L</PARAMETERS> below for more information. 197 198=item EVP_MD_CTX_get_params() 199 200Retrieves the requested list of I<params> from a MD context I<ctx>. 201See L</PARAMETERS> below for more information. 202 203=item EVP_MD_CTX_set_params() 204 205Sets the list of I<params> into a MD context I<ctx>. 206See L</PARAMETERS> below for more information. 207 208=item EVP_MD_gettable_params() 209 210Get a constant B<OSSL_PARAM> array that describes the retrievable parameters 211that can be used with EVP_MD_get_params(). See L<OSSL_PARAM(3)> for the 212use of B<OSSL_PARAM> as a parameter descriptor. 213 214=item EVP_MD_gettable_ctx_params(), EVP_MD_CTX_gettable_params() 215 216Get a constant B<OSSL_PARAM> array that describes the retrievable parameters 217that can be used with EVP_MD_CTX_get_params(). EVP_MD_gettable_ctx_params() 218returns the parameters that can be retrieved from the algorithm, whereas 219EVP_MD_CTX_gettable_params() returns the parameters that can be retrieved 220in the context's current state. See L<OSSL_PARAM(3)> for the use of 221B<OSSL_PARAM> as a parameter descriptor. 222 223=item EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() 224 225Get a constant B<OSSL_PARAM> array that describes the settable parameters 226that can be used with EVP_MD_CTX_set_params(). EVP_MD_settable_ctx_params() 227returns the parameters that can be set from the algorithm, whereas 228EVP_MD_CTX_settable_params() returns the parameters that can be set in the 229context's current state. See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> 230as a parameter descriptor. 231 232=item EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), EVP_MD_CTX_test_flags() 233 234Sets, clears and tests I<ctx> flags. See L</FLAGS> below for more information. 235 236=item EVP_Q_digest() is a quick one-shot digest function. 237 238It hashes I<datalen> bytes of data at I<data> using the digest algorithm 239I<name>, which is fetched using the optional I<libctx> and I<propq> parameters. 240The digest value is placed in I<md> and its length is written at I<mdlen> 241if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 242 243=item EVP_Digest() 244 245A wrapper around the Digest Init_ex, Update and Final_ex functions. 246Hashes I<count> bytes of data at I<data> using a digest I<type> from ENGINE 247I<impl>. The digest value is placed in I<md> and its length is written at I<size> 248if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 249If I<impl> is NULL the default implementation of digest I<type> is used. 250 251=item EVP_DigestInit_ex2() 252 253Sets up digest context I<ctx> to use a digest I<type>. 254I<type> is typically supplied by a function such as EVP_sha1(), or a 255value explicitly fetched with EVP_MD_fetch(). 256 257The parameters B<params> are set on the context after initialisation. 258 259The I<type> parameter can be NULL if I<ctx> has been already initialized 260with another EVP_DigestInit_ex() call and has not been reset with 261EVP_MD_CTX_reset(). 262 263=item EVP_DigestInit_ex() 264 265Sets up digest context I<ctx> to use a digest I<type>. 266I<type> is typically supplied by a function such as EVP_sha1(), or a 267value explicitly fetched with EVP_MD_fetch(). 268 269If I<impl> is non-NULL, its implementation of the digest I<type> is used if 270there is one, and if not, the default implementation is used. 271 272The I<type> parameter can be NULL if I<ctx> has been already initialized 273with another EVP_DigestInit_ex() call and has not been reset with 274EVP_MD_CTX_reset(). 275 276=item EVP_DigestUpdate() 277 278Hashes I<cnt> bytes of data at I<d> into the digest context I<ctx>. This 279function can be called several times on the same I<ctx> to hash additional 280data. 281 282=item EVP_DigestFinal_ex() 283 284Retrieves the digest value from I<ctx> and places it in I<md>. If the I<s> 285parameter is not NULL then the number of bytes of data written (i.e. the 286length of the digest) will be written to the integer at I<s>, at most 287B<EVP_MAX_MD_SIZE> bytes will be written. After calling EVP_DigestFinal_ex() 288no additional calls to EVP_DigestUpdate() can be made, but 289EVP_DigestInit_ex2() can be called to initialize a new digest operation. 290 291=item EVP_DigestFinalXOF() 292 293Interfaces to extendable-output functions, XOFs, such as SHAKE128 and SHAKE256. 294It retrieves the digest value from I<ctx> and places it in I<len>-sized I<md>. 295After calling this function no additional calls to EVP_DigestUpdate() can be 296made, but EVP_DigestInit_ex2() can be called to initialize a new operation. 297 298=item EVP_MD_CTX_copy_ex() 299 300Can be used to copy the message digest state from I<in> to I<out>. This is 301useful if large amounts of data are to be hashed which only differ in the last 302few bytes. 303 304=item EVP_DigestInit() 305 306Behaves in the same way as EVP_DigestInit_ex2() except it doesn't set any 307parameters and calls EVP_MD_CTX_reset() so it cannot be used with an I<type> 308of NULL. 309 310=item EVP_DigestFinal() 311 312Similar to EVP_DigestFinal_ex() except after computing the digest 313the digest context I<ctx> is automatically cleaned up with EVP_MD_CTX_reset(). 314 315=item EVP_MD_CTX_copy() 316 317Similar to EVP_MD_CTX_copy_ex() except the destination I<out> does not have to 318be initialized. 319 320=item EVP_MD_is_a() 321 322Returns 1 if I<md> is an implementation of an algorithm that's 323identifiable with I<name>, otherwise 0. 324 325If I<md> is a legacy digest (it's the return value from the likes of 326EVP_sha256() rather than the result of an EVP_MD_fetch()), only cipher 327names registered with the default library context (see 328L<OSSL_LIB_CTX(3)>) will be considered. 329 330=item EVP_MD_get0_name(), 331EVP_MD_CTX_get0_name() 332 333Return the name of the given message digest. For fetched message 334digests with multiple names, only one of them is returned; it's 335recommended to use EVP_MD_names_do_all() instead. 336 337=item EVP_MD_names_do_all() 338 339Traverses all names for the I<md>, and calls I<fn> with each name and 340I<data>. This is only useful with fetched B<EVP_MD>s. 341 342=item EVP_MD_get0_description() 343 344Returns a description of the digest, meant for display and human consumption. 345The description is at the discretion of the digest implementation. 346 347=item EVP_MD_get0_provider() 348 349Returns an B<OSSL_PROVIDER> pointer to the provider that implements the given 350B<EVP_MD>. 351 352=item EVP_MD_get_size(), 353EVP_MD_CTX_get_size() 354 355Return the size of the message digest when passed an B<EVP_MD> or an 356B<EVP_MD_CTX> structure, i.e. the size of the hash. 357 358=item EVP_MD_get_block_size(), 359EVP_MD_CTX_get_block_size() 360 361Return the block size of the message digest when passed an B<EVP_MD> or an 362B<EVP_MD_CTX> structure. 363 364=item EVP_MD_get_type(), 365EVP_MD_CTX_get_type() 366 367Return the NID of the OBJECT IDENTIFIER representing the given message digest 368when passed an B<EVP_MD> structure. For example, C<EVP_MD_get_type(EVP_sha1())> 369returns B<NID_sha1>. This function is normally used when setting ASN1 OIDs. 370 371=item EVP_MD_CTX_get0_md_data() 372 373Return the digest method private data for the passed B<EVP_MD_CTX>. 374The space is allocated by OpenSSL and has the size originally set with 375EVP_MD_meth_set_app_datasize(). 376 377=item EVP_MD_CTX_get0_md(), EVP_MD_CTX_get1_md() 378 379EVP_MD_CTX_get0_md() returns 380the B<EVP_MD> structure corresponding to the passed B<EVP_MD_CTX>. This 381will be the same B<EVP_MD> object originally passed to EVP_DigestInit_ex2() (or 382other similar function) when the EVP_MD_CTX was first initialised. Note that 383where explicit fetch is in use (see L<EVP_MD_fetch(3)>) the value returned from 384this function will not have its reference count incremented and therefore it 385should not be used after the EVP_MD_CTX is freed. 386EVP_MD_CTX_get1_md() is the same except the ownership is passed to the 387caller and is from the passed B<EVP_MD_CTX>. 388 389=item EVP_MD_CTX_set_update_fn() 390 391Sets the update function for I<ctx> to I<update>. 392This is the function that is called by EVP_DigestUpdate(). If not set, the 393update function from the B<EVP_MD> type specified at initialization is used. 394 395=item EVP_MD_CTX_update_fn() 396 397Returns the update function for I<ctx>. 398 399=item EVP_MD_get_flags() 400 401Returns the I<md> flags. Note that these are different from the B<EVP_MD_CTX> 402ones. See L<EVP_MD_meth_set_flags(3)> for more information. 403 404=item EVP_MD_get_pkey_type() 405 406Returns the NID of the public key signing algorithm associated with this 407digest. For example EVP_sha1() is associated with RSA so this will return 408B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms are no 409longer linked this function is only retained for compatibility reasons. 410 411=item EVP_md_null() 412 413A "null" message digest that does nothing: i.e. the hash it returns is of zero 414length. 415 416=item EVP_get_digestbyname(), 417EVP_get_digestbynid(), 418EVP_get_digestbyobj() 419 420Returns an B<EVP_MD> structure when passed a digest name, a digest B<NID> or an 421B<ASN1_OBJECT> structure respectively. 422 423The EVP_get_digestbyname() function is present for backwards compatibility with 424OpenSSL prior to version 3 and is different to the EVP_MD_fetch() function 425since it does not attempt to "fetch" an implementation of the cipher. 426Additionally, it only knows about digests that are built-in to OpenSSL and have 427an associated NID. Similarly EVP_get_digestbynid() and EVP_get_digestbyobj() 428also return objects without an associated implementation. 429 430When the digest objects returned by these functions are used (such as in a call 431to EVP_DigestInit_ex()) an implementation of the digest will be implicitly 432fetched from the loaded providers. This fetch could fail if no suitable 433implementation is available. Use EVP_MD_fetch() instead to explicitly fetch 434the algorithm and an associated implementation from a provider. 435 436See L<crypto(7)/ALGORITHM FETCHING> for more information about fetching. 437 438The digest objects returned from these functions do not need to be freed with 439EVP_MD_free(). 440 441=item EVP_MD_CTX_get_pkey_ctx() 442 443Returns the B<EVP_PKEY_CTX> assigned to I<ctx>. The returned pointer should not 444be freed by the caller. 445 446=item EVP_MD_CTX_set_pkey_ctx() 447 448Assigns an B<EVP_PKEY_CTX> to B<EVP_MD_CTX>. This is usually used to provide 449a customized B<EVP_PKEY_CTX> to L<EVP_DigestSignInit(3)> or 450L<EVP_DigestVerifyInit(3)>. The I<pctx> passed to this function should be freed 451by the caller. A NULL I<pctx> pointer is also allowed to clear the B<EVP_PKEY_CTX> 452assigned to I<ctx>. In such case, freeing the cleared B<EVP_PKEY_CTX> or not 453depends on how the B<EVP_PKEY_CTX> is created. 454 455=item EVP_MD_do_all_provided() 456 457Traverses all messages digests implemented by all activated providers 458in the given library context I<libctx>, and for each of the implementations, 459calls the given function I<fn> with the implementation method and the given 460I<arg> as argument. 461 462=back 463 464=head1 PARAMETERS 465 466See L<OSSL_PARAM(3)> for information about passing parameters. 467 468EVP_MD_CTX_set_params() can be used with the following OSSL_PARAM keys: 469 470=over 4 471 472=item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer> 473 474Sets the digest length for extendable output functions. 475It is used by the SHAKE algorithm and should not exceed what can be given 476using a B<size_t>. 477 478=item "pad-type" (B<OSSL_DIGEST_PARAM_PAD_TYPE>) <unsigned integer> 479 480Sets the padding type. 481It is used by the MDC2 algorithm. 482 483=back 484 485EVP_MD_CTX_get_params() can be used with the following OSSL_PARAM keys: 486 487=over 4 488 489=item "micalg" (B<OSSL_PARAM_DIGEST_KEY_MICALG>) <UTF8 string>. 490 491Gets the digest Message Integrity Check algorithm string. This is used when 492creating S/MIME multipart/signed messages, as specified in RFC 3851. 493It may be used by external engines or providers. 494 495=back 496 497=head1 CONTROLS 498 499EVP_MD_CTX_ctrl() can be used to send the following standard controls: 500 501=over 4 502 503=item EVP_MD_CTRL_MICALG 504 505Gets the digest Message Integrity Check algorithm string. This is used when 506creating S/MIME multipart/signed messages, as specified in RFC 3851. 507The string value is written to I<p2>. 508 509When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with 510an L<OSSL_PARAM(3)> item with the key "micalg" (B<OSSL_DIGEST_PARAM_MICALG>). 511 512=item EVP_MD_CTRL_XOF_LEN 513 514This control sets the digest length for extendable output functions to I<p1>. 515Sending this control directly should not be necessary, the use of 516EVP_DigestFinalXOF() is preferred. 517Currently used by SHAKE. 518 519When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with 520an L<OSSL_PARAM(3)> item with the key "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>). 521 522=back 523 524=head1 FLAGS 525 526EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags() and EVP_MD_CTX_test_flags() 527can be used the manipulate and test these B<EVP_MD_CTX> flags: 528 529=over 4 530 531=item EVP_MD_CTX_FLAG_ONESHOT 532 533This flag instructs the digest to optimize for one update only, if possible. 534 535=for comment EVP_MD_CTX_FLAG_CLEANED is internal, don't mention it 536 537=for comment EVP_MD_CTX_FLAG_REUSE is internal, don't mention it 538 539=for comment We currently avoid documenting flags that are only bit holder: 540EVP_MD_CTX_FLAG_NON_FIPS_ALLOW, EVP_MD_CTX_FLAGS_PAD_* 541 542=item EVP_MD_CTX_FLAG_NO_INIT 543 544This flag instructs EVP_DigestInit() and similar not to initialise the 545implementation specific data. 546 547=item EVP_MD_CTX_FLAG_FINALISE 548 549Some functions such as EVP_DigestSign only finalise copies of internal 550contexts so additional data can be included after the finalisation call. 551This is inefficient if this functionality is not required, and can be 552disabled with this flag. 553 554=back 555 556=head1 RETURN VALUES 557 558=over 4 559 560=item EVP_MD_fetch() 561 562Returns a pointer to a B<EVP_MD> for success or NULL for failure. 563 564=item EVP_MD_up_ref() 565 566Returns 1 for success or 0 for failure. 567 568=item EVP_Q_digest(), 569EVP_Digest(), 570EVP_DigestInit_ex2(), 571EVP_DigestInit_ex(), 572EVP_DigestUpdate(), 573EVP_DigestFinal_ex(), 574EVP_DigestFinalXOF(), and 575EVP_DigestFinal() 576 577return 1 for 578success and 0 for failure. 579 580=item EVP_MD_CTX_ctrl() 581 582Returns 1 if successful or 0 for failure. 583 584=item EVP_MD_CTX_set_params(), 585EVP_MD_CTX_get_params() 586 587Returns 1 if successful or 0 for failure. 588 589=item EVP_MD_CTX_settable_params(), 590EVP_MD_CTX_gettable_params() 591 592Return an array of constant B<OSSL_PARAM>s, or NULL if there is none 593to get. 594 595=item EVP_MD_CTX_copy_ex() 596 597Returns 1 if successful or 0 for failure. 598 599=item EVP_MD_get_type(), 600EVP_MD_get_pkey_type() 601 602Returns the NID of the corresponding OBJECT IDENTIFIER or NID_undef if none 603exists. 604 605=item EVP_MD_get_size(), 606EVP_MD_get_block_size(), 607EVP_MD_CTX_get_size(), 608EVP_MD_CTX_get_block_size() 609 610Returns the digest or block size in bytes. 611 612=item EVP_md_null() 613 614Returns a pointer to the B<EVP_MD> structure of the "null" message digest. 615 616=item EVP_get_digestbyname(), 617EVP_get_digestbynid(), 618EVP_get_digestbyobj() 619 620Returns either an B<EVP_MD> structure or NULL if an error occurs. 621 622=item EVP_MD_CTX_set_pkey_ctx() 623 624This function has no return value. 625 626=item EVP_MD_names_do_all() 627 628Returns 1 if the callback was called for all names. A return value of 0 means 629that the callback was not called for any names. 630 631=back 632 633=head1 NOTES 634 635The B<EVP> interface to message digests should almost always be used in 636preference to the low-level interfaces. This is because the code then becomes 637transparent to the digest used and much more flexible. 638 639New applications should use the SHA-2 (such as L<EVP_sha256(3)>) or the SHA-3 640digest algorithms (such as L<EVP_sha3_512(3)>). The other digest algorithms 641are still in common use. 642 643For most applications the I<impl> parameter to EVP_DigestInit_ex() will be 644set to NULL to use the default digest implementation. 645 646The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are 647obsolete but are retained to maintain compatibility with existing code. New 648applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and 649EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context 650instead of initializing and cleaning it up on each call and allow non default 651implementations of digests to be specified. 652 653If digest contexts are not cleaned up after use, 654memory leaks will occur. 655 656EVP_MD_CTX_get0_name(), EVP_MD_CTX_get_size(), EVP_MD_CTX_get_block_size(), 657EVP_MD_CTX_get_type(), EVP_get_digestbynid() and EVP_get_digestbyobj() are 658defined as macros. 659 660EVP_MD_CTX_ctrl() sends commands to message digests for additional configuration 661or control. 662 663=head1 EXAMPLES 664 665This example digests the data "Test Message\n" and "Hello World\n", using the 666digest name passed on the command line. 667 668 #include <stdio.h> 669 #include <string.h> 670 #include <openssl/evp.h> 671 672 int main(int argc, char *argv[]) 673 { 674 EVP_MD_CTX *mdctx; 675 const EVP_MD *md; 676 char mess1[] = "Test Message\n"; 677 char mess2[] = "Hello World\n"; 678 unsigned char md_value[EVP_MAX_MD_SIZE]; 679 unsigned int md_len, i; 680 681 if (argv[1] == NULL) { 682 printf("Usage: mdtest digestname\n"); 683 exit(1); 684 } 685 686 md = EVP_get_digestbyname(argv[1]); 687 if (md == NULL) { 688 printf("Unknown message digest %s\n", argv[1]); 689 exit(1); 690 } 691 692 mdctx = EVP_MD_CTX_new(); 693 EVP_DigestInit_ex2(mdctx, md, NULL); 694 EVP_DigestUpdate(mdctx, mess1, strlen(mess1)); 695 EVP_DigestUpdate(mdctx, mess2, strlen(mess2)); 696 EVP_DigestFinal_ex(mdctx, md_value, &md_len); 697 EVP_MD_CTX_free(mdctx); 698 699 printf("Digest is: "); 700 for (i = 0; i < md_len; i++) 701 printf("%02x", md_value[i]); 702 printf("\n"); 703 704 exit(0); 705 } 706 707=head1 SEE ALSO 708 709L<EVP_MD_meth_new(3)>, 710L<openssl-dgst(1)>, 711L<evp(7)>, 712L<OSSL_PROVIDER(3)>, 713L<OSSL_PARAM(3)>, 714L<property(7)>, 715L<crypto(7)/ALGORITHM FETCHING>, 716L<provider-digest(7)>, 717L<life_cycle-digest(7)> 718 719The full list of digest algorithms are provided below. 720 721L<EVP_blake2b512(3)>, 722L<EVP_md2(3)>, 723L<EVP_md4(3)>, 724L<EVP_md5(3)>, 725L<EVP_mdc2(3)>, 726L<EVP_ripemd160(3)>, 727L<EVP_sha1(3)>, 728L<EVP_sha224(3)>, 729L<EVP_sha3_224(3)>, 730L<EVP_sm3(3)>, 731L<EVP_whirlpool(3)> 732 733=head1 HISTORY 734 735The EVP_MD_CTX_create() and EVP_MD_CTX_destroy() functions were renamed to 736EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.0, respectively. 737 738The link between digests and signing algorithms was fixed in OpenSSL 1.0 and 739later, so now EVP_sha1() can be used with RSA and DSA. 740 741The EVP_dss1() function was removed in OpenSSL 1.1.0. 742 743The EVP_MD_CTX_set_pkey_ctx() function was added in OpenSSL 1.1.1. 744 745The EVP_Q_digest(), EVP_DigestInit_ex2(), 746EVP_MD_fetch(), EVP_MD_free(), EVP_MD_up_ref(), 747EVP_MD_get_params(), EVP_MD_CTX_set_params(), EVP_MD_CTX_get_params(), 748EVP_MD_gettable_params(), EVP_MD_gettable_ctx_params(), 749EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() and 750EVP_MD_CTX_gettable_params() functions were added in OpenSSL 3.0. 751 752The EVP_MD_type(), EVP_MD_nid(), EVP_MD_name(), EVP_MD_pkey_type(), 753EVP_MD_size(), EVP_MD_block_size(), EVP_MD_flags(), EVP_MD_CTX_size(), 754EVP_MD_CTX_block_size(), EVP_MD_CTX_type(), and EVP_MD_CTX_md_data() 755functions were renamed to include C<get> or C<get0> in their names in 756OpenSSL 3.0, respectively. The old names are kept as non-deprecated 757alias macros. 758 759The EVP_MD_CTX_md() function was deprecated in OpenSSL 3.0; use 760EVP_MD_CTX_get0_md() instead. 761EVP_MD_CTX_update_fn() and EVP_MD_CTX_set_update_fn() were deprecated 762in OpenSSL 3.0. 763 764=head1 COPYRIGHT 765 766Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved. 767 768Licensed under the Apache License 2.0 (the "License"). You may not use 769this file except in compliance with the License. You can obtain a copy 770in the file LICENSE in the source distribution or at 771L<https://www.openssl.org/source/license.html>. 772 773=cut 774