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 L<OSSL_PARAM(3)> array that describes the retrievable parameters 211that can be used with EVP_MD_get_params(). 212 213=item EVP_MD_gettable_ctx_params(), EVP_MD_CTX_gettable_params() 214 215Get a constant L<OSSL_PARAM(3)> array that describes the retrievable parameters 216that can be used with EVP_MD_CTX_get_params(). EVP_MD_gettable_ctx_params() 217returns the parameters that can be retrieved from the algorithm, whereas 218EVP_MD_CTX_gettable_params() returns the parameters that can be retrieved 219in the context's current state. 220 221=item EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() 222 223Get a constant L<OSSL_PARAM(3)> array that describes the settable parameters 224that can be used with EVP_MD_CTX_set_params(). EVP_MD_settable_ctx_params() 225returns the parameters that can be set from the algorithm, whereas 226EVP_MD_CTX_settable_params() returns the parameters that can be set in the 227context's current state. 228 229=item EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), EVP_MD_CTX_test_flags() 230 231Sets, clears and tests I<ctx> flags. See L</FLAGS> below for more information. 232 233=item EVP_Q_digest() is a quick one-shot digest function. 234 235It hashes I<datalen> bytes of data at I<data> using the digest algorithm 236I<name>, which is fetched using the optional I<libctx> and I<propq> parameters. 237The digest value is placed in I<md> and its length is written at I<mdlen> 238if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 239 240=item EVP_Digest() 241 242A wrapper around the Digest Init_ex, Update and Final_ex functions. 243Hashes I<count> bytes of data at I<data> using a digest I<type> from ENGINE 244I<impl>. The digest value is placed in I<md> and its length is written at I<size> 245if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 246If I<impl> is NULL the default implementation of digest I<type> is used. 247 248=item EVP_DigestInit_ex2() 249 250Sets up digest context I<ctx> to use a digest I<type>. 251I<type> is typically supplied by a function such as EVP_sha1(), or a 252value explicitly fetched with EVP_MD_fetch(). 253 254The parameters B<params> are set on the context after initialisation. 255 256The I<type> parameter can be NULL if I<ctx> has been already initialized 257with another EVP_DigestInit_ex() call and has not been reset with 258EVP_MD_CTX_reset(). 259 260=item EVP_DigestInit_ex() 261 262Sets up digest context I<ctx> to use a digest I<type>. 263I<type> is typically supplied by a function such as EVP_sha1(), or a 264value explicitly fetched with EVP_MD_fetch(). 265 266If I<impl> is non-NULL, its implementation of the digest I<type> is used if 267there is one, and if not, the default implementation is used. 268 269The I<type> parameter can be NULL if I<ctx> has been already initialized 270with another EVP_DigestInit_ex() call and has not been reset with 271EVP_MD_CTX_reset(). 272 273=item EVP_DigestUpdate() 274 275Hashes I<cnt> bytes of data at I<d> into the digest context I<ctx>. This 276function can be called several times on the same I<ctx> to hash additional 277data. 278 279=item EVP_DigestFinal_ex() 280 281Retrieves the digest value from I<ctx> and places it in I<md>. If the I<s> 282parameter is not NULL then the number of bytes of data written (i.e. the 283length of the digest) will be written to the integer at I<s>, at most 284B<EVP_MAX_MD_SIZE> bytes will be written. After calling EVP_DigestFinal_ex() 285no additional calls to EVP_DigestUpdate() can be made, but 286EVP_DigestInit_ex2() can be called to initialize a new digest operation. 287 288=item EVP_DigestFinalXOF() 289 290Interfaces to extendable-output functions, XOFs, such as SHAKE128 and SHAKE256. 291It retrieves the digest value from I<ctx> and places it in I<len>-sized I<md>. 292After calling this function no additional calls to EVP_DigestUpdate() can be 293made, but EVP_DigestInit_ex2() can be called to initialize a new operation. 294 295=item EVP_MD_CTX_copy_ex() 296 297Can be used to copy the message digest state from I<in> to I<out>. This is 298useful if large amounts of data are to be hashed which only differ in the last 299few bytes. 300 301=item EVP_DigestInit() 302 303Behaves in the same way as EVP_DigestInit_ex2() except it doesn't set any 304parameters and calls EVP_MD_CTX_reset() so it cannot be used with an I<type> 305of NULL. 306 307=item EVP_DigestFinal() 308 309Similar to EVP_DigestFinal_ex() except after computing the digest 310the digest context I<ctx> is automatically cleaned up with EVP_MD_CTX_reset(). 311 312=item EVP_MD_CTX_copy() 313 314Similar to EVP_MD_CTX_copy_ex() except the destination I<out> does not have to 315be initialized. 316 317=item EVP_MD_is_a() 318 319Returns 1 if I<md> is an implementation of an algorithm that's 320identifiable with I<name>, otherwise 0. 321 322If I<md> is a legacy digest (it's the return value from the likes of 323EVP_sha256() rather than the result of an EVP_MD_fetch()), only cipher 324names registered with the default library context (see 325L<OSSL_LIB_CTX(3)>) will be considered. 326 327=item EVP_MD_get0_name(), 328EVP_MD_CTX_get0_name() 329 330Return the name of the given message digest. For fetched message 331digests with multiple names, only one of them is returned; it's 332recommended to use EVP_MD_names_do_all() instead. 333 334=item EVP_MD_names_do_all() 335 336Traverses all names for the I<md>, and calls I<fn> with each name and 337I<data>. This is only useful with fetched B<EVP_MD>s. 338 339=item EVP_MD_get0_description() 340 341Returns a description of the digest, meant for display and human consumption. 342The description is at the discretion of the digest implementation. 343 344=item EVP_MD_get0_provider() 345 346Returns an B<OSSL_PROVIDER> pointer to the provider that implements the given 347B<EVP_MD>. 348 349=item EVP_MD_get_size(), 350EVP_MD_CTX_get_size() 351 352Return the size of the message digest when passed an B<EVP_MD> or an 353B<EVP_MD_CTX> structure, i.e. the size of the hash. 354 355=item EVP_MD_get_block_size(), 356EVP_MD_CTX_get_block_size() 357 358Return the block size of the message digest when passed an B<EVP_MD> or an 359B<EVP_MD_CTX> structure. 360 361=item EVP_MD_get_type(), 362EVP_MD_CTX_get_type() 363 364Return the NID of the OBJECT IDENTIFIER representing the given message digest 365when passed an B<EVP_MD> structure. For example, C<EVP_MD_get_type(EVP_sha1())> 366returns B<NID_sha1>. This function is normally used when setting ASN1 OIDs. 367 368=item EVP_MD_CTX_get0_md_data() 369 370Return the digest method private data for the passed B<EVP_MD_CTX>. 371The space is allocated by OpenSSL and has the size originally set with 372EVP_MD_meth_set_app_datasize(). 373 374=item EVP_MD_CTX_get0_md(), EVP_MD_CTX_get1_md() 375 376EVP_MD_CTX_get0_md() returns 377the B<EVP_MD> structure corresponding to the passed B<EVP_MD_CTX>. This 378will be the same B<EVP_MD> object originally passed to EVP_DigestInit_ex2() (or 379other similar function) when the EVP_MD_CTX was first initialised. Note that 380where explicit fetch is in use (see L<EVP_MD_fetch(3)>) the value returned from 381this function will not have its reference count incremented and therefore it 382should not be used after the EVP_MD_CTX is freed. 383EVP_MD_CTX_get1_md() is the same except the ownership is passed to the 384caller and is from the passed B<EVP_MD_CTX>. 385 386=item EVP_MD_CTX_set_update_fn() 387 388Sets the update function for I<ctx> to I<update>. 389This is the function that is called by EVP_DigestUpdate(). If not set, the 390update function from the B<EVP_MD> type specified at initialization is used. 391 392=item EVP_MD_CTX_update_fn() 393 394Returns the update function for I<ctx>. 395 396=item EVP_MD_get_flags() 397 398Returns the I<md> flags. Note that these are different from the B<EVP_MD_CTX> 399ones. See L<EVP_MD_meth_set_flags(3)> for more information. 400 401=item EVP_MD_get_pkey_type() 402 403Returns the NID of the public key signing algorithm associated with this 404digest. For example EVP_sha1() is associated with RSA so this will return 405B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms are no 406longer linked this function is only retained for compatibility reasons. 407 408=item EVP_md_null() 409 410A "null" message digest that does nothing: i.e. the hash it returns is of zero 411length. 412 413=item EVP_get_digestbyname(), 414EVP_get_digestbynid(), 415EVP_get_digestbyobj() 416 417Returns an B<EVP_MD> structure when passed a digest name, a digest B<NID> or an 418B<ASN1_OBJECT> structure respectively. 419 420The EVP_get_digestbyname() function is present for backwards compatibility with 421OpenSSL prior to version 3 and is different to the EVP_MD_fetch() function 422since it does not attempt to "fetch" an implementation of the cipher. 423Additionally, it only knows about digests that are built-in to OpenSSL and have 424an associated NID. Similarly EVP_get_digestbynid() and EVP_get_digestbyobj() 425also return objects without an associated implementation. 426 427When the digest objects returned by these functions are used (such as in a call 428to EVP_DigestInit_ex()) an implementation of the digest will be implicitly 429fetched from the loaded providers. This fetch could fail if no suitable 430implementation is available. Use EVP_MD_fetch() instead to explicitly fetch 431the algorithm and an associated implementation from a provider. 432 433See L<crypto(7)/ALGORITHM FETCHING> for more information about fetching. 434 435The digest objects returned from these functions do not need to be freed with 436EVP_MD_free(). 437 438=item EVP_MD_CTX_get_pkey_ctx() 439 440Returns the B<EVP_PKEY_CTX> assigned to I<ctx>. The returned pointer should not 441be freed by the caller. 442 443=item EVP_MD_CTX_set_pkey_ctx() 444 445Assigns an B<EVP_PKEY_CTX> to B<EVP_MD_CTX>. This is usually used to provide 446a customized B<EVP_PKEY_CTX> to L<EVP_DigestSignInit(3)> or 447L<EVP_DigestVerifyInit(3)>. The I<pctx> passed to this function should be freed 448by the caller. A NULL I<pctx> pointer is also allowed to clear the B<EVP_PKEY_CTX> 449assigned to I<ctx>. In such case, freeing the cleared B<EVP_PKEY_CTX> or not 450depends on how the B<EVP_PKEY_CTX> is created. 451 452=item EVP_MD_do_all_provided() 453 454Traverses all messages digests implemented by all activated providers 455in the given library context I<libctx>, and for each of the implementations, 456calls the given function I<fn> with the implementation method and the given 457I<arg> as argument. 458 459=back 460 461=head1 PARAMETERS 462 463See L<OSSL_PARAM(3)> for information about passing parameters. 464 465EVP_MD_CTX_set_params() can be used with the following OSSL_PARAM keys: 466 467=over 4 468 469=item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer> 470 471Sets the digest length for extendable output functions. 472It is used by the SHAKE algorithm and should not exceed what can be given 473using a B<size_t>. 474 475=item "pad-type" (B<OSSL_DIGEST_PARAM_PAD_TYPE>) <unsigned integer> 476 477Sets the padding type. 478It is used by the MDC2 algorithm. 479 480=back 481 482EVP_MD_CTX_get_params() can be used with the following OSSL_PARAM keys: 483 484=over 4 485 486=item "micalg" (B<OSSL_PARAM_DIGEST_KEY_MICALG>) <UTF8 string>. 487 488Gets the digest Message Integrity Check algorithm string. This is used when 489creating S/MIME multipart/signed messages, as specified in RFC 3851. 490It may be used by external engines or providers. 491 492=back 493 494=head1 CONTROLS 495 496EVP_MD_CTX_ctrl() can be used to send the following standard controls: 497 498=over 4 499 500=item EVP_MD_CTRL_MICALG 501 502Gets the digest Message Integrity Check algorithm string. This is used when 503creating S/MIME multipart/signed messages, as specified in RFC 3851. 504The string value is written to I<p2>. 505 506When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with 507an L<OSSL_PARAM(3)> item with the key "micalg" (B<OSSL_DIGEST_PARAM_MICALG>). 508 509=item EVP_MD_CTRL_XOF_LEN 510 511This control sets the digest length for extendable output functions to I<p1>. 512Sending this control directly should not be necessary, the use of 513EVP_DigestFinalXOF() is preferred. 514Currently used by SHAKE. 515 516When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with 517an L<OSSL_PARAM(3)> item with the key "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>). 518 519=back 520 521=head1 FLAGS 522 523EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags() and EVP_MD_CTX_test_flags() 524can be used the manipulate and test these B<EVP_MD_CTX> flags: 525 526=over 4 527 528=item EVP_MD_CTX_FLAG_ONESHOT 529 530This flag instructs the digest to optimize for one update only, if possible. 531 532=for comment EVP_MD_CTX_FLAG_CLEANED is internal, don't mention it 533 534=for comment EVP_MD_CTX_FLAG_REUSE is internal, don't mention it 535 536=for comment We currently avoid documenting flags that are only bit holder: 537EVP_MD_CTX_FLAG_NON_FIPS_ALLOW, EVP_MD_CTX_FLAGS_PAD_* 538 539=item EVP_MD_CTX_FLAG_NO_INIT 540 541This flag instructs EVP_DigestInit() and similar not to initialise the 542implementation specific data. 543 544=item EVP_MD_CTX_FLAG_FINALISE 545 546Some functions such as EVP_DigestSign only finalise copies of internal 547contexts so additional data can be included after the finalisation call. 548This is inefficient if this functionality is not required, and can be 549disabled with this flag. 550 551=back 552 553=head1 RETURN VALUES 554 555=over 4 556 557=item EVP_MD_fetch() 558 559Returns a pointer to a B<EVP_MD> for success or NULL for failure. 560 561=item EVP_MD_up_ref() 562 563Returns 1 for success or 0 for failure. 564 565=item EVP_Q_digest(), 566EVP_Digest(), 567EVP_DigestInit_ex2(), 568EVP_DigestInit_ex(), 569EVP_DigestInit(), 570EVP_DigestUpdate(), 571EVP_DigestFinal_ex(), 572EVP_DigestFinalXOF(), and 573EVP_DigestFinal() 574 575return 1 for 576success and 0 for failure. 577 578=item EVP_MD_CTX_ctrl() 579 580Returns 1 if successful or 0 for failure. 581 582=item EVP_MD_CTX_set_params(), 583EVP_MD_CTX_get_params() 584 585Returns 1 if successful or 0 for failure. 586 587=item EVP_MD_CTX_settable_params(), 588EVP_MD_CTX_gettable_params() 589 590Return an array of constant L<OSSL_PARAM(3)>s, or NULL if there is none 591to get. 592 593=item EVP_MD_CTX_copy_ex() 594 595Returns 1 if successful or 0 for failure. 596 597=item EVP_MD_get_type(), 598EVP_MD_get_pkey_type() 599 600Returns the NID of the corresponding OBJECT IDENTIFIER or NID_undef if none 601exists. 602 603=item EVP_MD_get_size(), 604EVP_MD_get_block_size(), 605EVP_MD_CTX_get_size(), 606EVP_MD_CTX_get_block_size() 607 608Returns the digest or block size in bytes or -1 for failure. 609 610=item EVP_md_null() 611 612Returns a pointer to the B<EVP_MD> structure of the "null" message digest. 613 614=item EVP_get_digestbyname(), 615EVP_get_digestbynid(), 616EVP_get_digestbyobj() 617 618Returns either an B<EVP_MD> structure or NULL if an error occurs. 619 620=item EVP_MD_CTX_set_pkey_ctx() 621 622This function has no return value. 623 624=item EVP_MD_names_do_all() 625 626Returns 1 if the callback was called for all names. A return value of 0 means 627that the callback was not called for any names. 628 629=back 630 631=head1 NOTES 632 633The B<EVP> interface to message digests should almost always be used in 634preference to the low-level interfaces. This is because the code then becomes 635transparent to the digest used and much more flexible. 636 637New applications should use the SHA-2 (such as L<EVP_sha256(3)>) or the SHA-3 638digest algorithms (such as L<EVP_sha3_512(3)>). The other digest algorithms 639are still in common use. 640 641For most applications the I<impl> parameter to EVP_DigestInit_ex() will be 642set to NULL to use the default digest implementation. 643 644Ignoring failure returns of EVP_DigestInit_ex(), EVP_DigestInit_ex2(), or 645EVP_DigestInit() can lead to undefined behavior on subsequent calls 646updating or finalizing the B<EVP_MD_CTX> such as the EVP_DigestUpdate() or 647EVP_DigestFinal() functions. The only valid calls on the B<EVP_MD_CTX> 648when initialization fails are calls that attempt another initialization of 649the context or release the context. 650 651The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are 652obsolete but are retained to maintain compatibility with existing code. New 653applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and 654EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context 655instead of initializing and cleaning it up on each call and allow non default 656implementations of digests to be specified. 657 658If digest contexts are not cleaned up after use, 659memory leaks will occur. 660 661EVP_MD_CTX_get0_name(), EVP_MD_CTX_get_size(), EVP_MD_CTX_get_block_size(), 662EVP_MD_CTX_get_type(), EVP_get_digestbynid() and EVP_get_digestbyobj() are 663defined as macros. 664 665EVP_MD_CTX_ctrl() sends commands to message digests for additional configuration 666or control. 667 668=head1 EXAMPLES 669 670This example digests the data "Test Message\n" and "Hello World\n", using the 671digest name passed on the command line. 672 673 #include <stdio.h> 674 #include <string.h> 675 #include <openssl/evp.h> 676 677 int main(int argc, char *argv[]) 678 { 679 EVP_MD_CTX *mdctx; 680 const EVP_MD *md; 681 char mess1[] = "Test Message\n"; 682 char mess2[] = "Hello World\n"; 683 unsigned char md_value[EVP_MAX_MD_SIZE]; 684 unsigned int md_len, i; 685 686 if (argv[1] == NULL) { 687 printf("Usage: mdtest digestname\n"); 688 exit(1); 689 } 690 691 md = EVP_get_digestbyname(argv[1]); 692 if (md == NULL) { 693 printf("Unknown message digest %s\n", argv[1]); 694 exit(1); 695 } 696 697 mdctx = EVP_MD_CTX_new(); 698 if (!EVP_DigestInit_ex2(mdctx, md, NULL)) { 699 printf("Message digest initialization failed.\n"); 700 EVP_MD_CTX_free(mdctx); 701 exit(1); 702 } 703 if (!EVP_DigestUpdate(mdctx, mess1, strlen(mess1))) { 704 printf("Message digest update failed.\n"); 705 EVP_MD_CTX_free(mdctx); 706 exit(1); 707 } 708 if (!EVP_DigestUpdate(mdctx, mess2, strlen(mess2))) { 709 printf("Message digest update failed.\n"); 710 EVP_MD_CTX_free(mdctx); 711 exit(1); 712 } 713 if (!EVP_DigestFinal_ex(mdctx, md_value, &md_len)) { 714 printf("Message digest finalization failed.\n"); 715 EVP_MD_CTX_free(mdctx); 716 exit(1); 717 } 718 EVP_MD_CTX_free(mdctx); 719 720 printf("Digest is: "); 721 for (i = 0; i < md_len; i++) 722 printf("%02x", md_value[i]); 723 printf("\n"); 724 725 exit(0); 726 } 727 728=head1 SEE ALSO 729 730L<EVP_MD_meth_new(3)>, 731L<openssl-dgst(1)>, 732L<evp(7)>, 733L<OSSL_PROVIDER(3)>, 734L<OSSL_PARAM(3)>, 735L<property(7)>, 736L<crypto(7)/ALGORITHM FETCHING>, 737L<provider-digest(7)>, 738L<life_cycle-digest(7)> 739 740The full list of digest algorithms are provided below. 741 742L<EVP_blake2b512(3)>, 743L<EVP_md2(3)>, 744L<EVP_md4(3)>, 745L<EVP_md5(3)>, 746L<EVP_mdc2(3)>, 747L<EVP_ripemd160(3)>, 748L<EVP_sha1(3)>, 749L<EVP_sha224(3)>, 750L<EVP_sha3_224(3)>, 751L<EVP_sm3(3)>, 752L<EVP_whirlpool(3)> 753 754=head1 HISTORY 755 756The EVP_MD_CTX_create() and EVP_MD_CTX_destroy() functions were renamed to 757EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.0, respectively. 758 759The link between digests and signing algorithms was fixed in OpenSSL 1.0 and 760later, so now EVP_sha1() can be used with RSA and DSA. 761 762The EVP_dss1() function was removed in OpenSSL 1.1.0. 763 764The EVP_MD_CTX_set_pkey_ctx() function was added in OpenSSL 1.1.1. 765 766The EVP_Q_digest(), EVP_DigestInit_ex2(), 767EVP_MD_fetch(), EVP_MD_free(), EVP_MD_up_ref(), 768EVP_MD_get_params(), EVP_MD_CTX_set_params(), EVP_MD_CTX_get_params(), 769EVP_MD_gettable_params(), EVP_MD_gettable_ctx_params(), 770EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() and 771EVP_MD_CTX_gettable_params() functions were added in OpenSSL 3.0. 772 773The EVP_MD_type(), EVP_MD_nid(), EVP_MD_name(), EVP_MD_pkey_type(), 774EVP_MD_size(), EVP_MD_block_size(), EVP_MD_flags(), EVP_MD_CTX_size(), 775EVP_MD_CTX_block_size(), EVP_MD_CTX_type(), and EVP_MD_CTX_md_data() 776functions were renamed to include C<get> or C<get0> in their names in 777OpenSSL 3.0, respectively. The old names are kept as non-deprecated 778alias macros. 779 780The EVP_MD_CTX_md() function was deprecated in OpenSSL 3.0; use 781EVP_MD_CTX_get0_md() instead. 782EVP_MD_CTX_update_fn() and EVP_MD_CTX_set_update_fn() were deprecated 783in OpenSSL 3.0. 784 785=head1 COPYRIGHT 786 787Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved. 788 789Licensed under the Apache License 2.0 (the "License"). You may not use 790this file except in compliance with the License. You can obtain a copy 791in the file LICENSE in the source distribution or at 792L<https://www.openssl.org/source/license.html>. 793 794=cut 795