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. 160If the argument is NULL, nothing is done. 161 162=item EVP_MD_CTX_new() 163 164Allocates and returns a digest context. 165 166=item EVP_MD_CTX_reset() 167 168Resets the digest context I<ctx>. This can be used to reuse an already 169existing context. 170 171=item EVP_MD_CTX_free() 172 173Cleans up digest context I<ctx> and frees up the space allocated to it. 174If the argument is NULL, nothing is done. 175 176=item EVP_MD_CTX_ctrl() 177 178I<This is a legacy method. EVP_MD_CTX_set_params() and EVP_MD_CTX_get_params() 179is the mechanism that should be used to set and get parameters that are used by 180providers.> 181 182Performs digest-specific control actions on context I<ctx>. The control command 183is indicated in I<cmd> and any additional arguments in I<p1> and I<p2>. 184EVP_MD_CTX_ctrl() must be called after EVP_DigestInit_ex2(). Other restrictions 185may apply depending on the control type and digest implementation. 186 187If this function happens to be used with a fetched B<EVP_MD>, it will 188translate the controls that are known to OpenSSL into L<OSSL_PARAM(3)> 189parameters with keys defined by OpenSSL and call EVP_MD_CTX_get_params() or 190EVP_MD_CTX_set_params() as is appropriate for each control command. 191 192See L</CONTROLS> below for more information, including what translations are 193being done. 194 195=item EVP_MD_get_params() 196 197Retrieves the requested list of I<params> from a MD I<md>. 198See L</PARAMETERS> below for more information. 199 200=item EVP_MD_CTX_get_params() 201 202Retrieves the requested list of I<params> from a MD context I<ctx>. 203See L</PARAMETERS> below for more information. 204 205=item EVP_MD_CTX_set_params() 206 207Sets the list of I<params> into a MD context I<ctx>. 208See L</PARAMETERS> below for more information. 209 210=item EVP_MD_gettable_params() 211 212Get a constant L<OSSL_PARAM(3)> array that describes the retrievable parameters 213that can be used with EVP_MD_get_params(). 214 215=item EVP_MD_gettable_ctx_params(), EVP_MD_CTX_gettable_params() 216 217Get a constant L<OSSL_PARAM(3)> array that describes the retrievable parameters 218that can be used with EVP_MD_CTX_get_params(). EVP_MD_gettable_ctx_params() 219returns the parameters that can be retrieved from the algorithm, whereas 220EVP_MD_CTX_gettable_params() returns the parameters that can be retrieved 221in the context's current state. 222 223=item EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() 224 225Get a constant L<OSSL_PARAM(3)> 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. 230 231=item EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), EVP_MD_CTX_test_flags() 232 233Sets, clears and tests I<ctx> flags. See L</FLAGS> below for more information. 234 235=item EVP_Q_digest() is a quick one-shot digest function. 236 237It hashes I<datalen> bytes of data at I<data> using the digest algorithm 238I<name>, which is fetched using the optional I<libctx> and I<propq> parameters. 239The digest value is placed in I<md> and its length is written at I<mdlen> 240if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 241 242=item EVP_Digest() 243 244A wrapper around the Digest Init_ex, Update and Final_ex functions. 245Hashes I<count> bytes of data at I<data> using a digest I<type> from ENGINE 246I<impl>. The digest value is placed in I<md> and its length is written at I<size> 247if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 248If I<impl> is NULL the default implementation of digest I<type> is used. 249 250=item EVP_DigestInit_ex2() 251 252Sets up digest context I<ctx> to use a digest I<type>. 253I<type> is typically supplied by a function such as EVP_sha1(), or a 254value explicitly fetched with EVP_MD_fetch(). 255 256The parameters B<params> are set on the context after initialisation. 257 258The I<type> parameter can be NULL if I<ctx> has been already initialized 259with another EVP_DigestInit_ex() call and has not been reset with 260EVP_MD_CTX_reset(). 261 262=item EVP_DigestInit_ex() 263 264Sets up digest context I<ctx> to use a digest I<type>. 265I<type> is typically supplied by a function such as EVP_sha1(), or a 266value explicitly fetched with EVP_MD_fetch(). 267 268If I<impl> is non-NULL, its implementation of the digest I<type> is used if 269there is one, and if not, the default implementation is used. 270 271The I<type> parameter can be NULL if I<ctx> has been already initialized 272with another EVP_DigestInit_ex() call and has not been reset with 273EVP_MD_CTX_reset(). 274 275=item EVP_DigestUpdate() 276 277Hashes I<cnt> bytes of data at I<d> into the digest context I<ctx>. This 278function can be called several times on the same I<ctx> to hash additional 279data. 280 281=item EVP_DigestFinal_ex() 282 283Retrieves the digest value from I<ctx> and places it in I<md>. If the I<s> 284parameter is not NULL then the number of bytes of data written (i.e. the 285length of the digest) will be written to the integer at I<s>, at most 286B<EVP_MAX_MD_SIZE> bytes will be written. After calling EVP_DigestFinal_ex() 287no additional calls to EVP_DigestUpdate() can be made, but 288EVP_DigestInit_ex2() can be called to initialize a new digest operation. 289 290=item EVP_DigestFinalXOF() 291 292Interfaces to extendable-output functions, XOFs, such as SHAKE128 and SHAKE256. 293It retrieves the digest value from I<ctx> and places it in I<len>-sized I<md>. 294After calling this function no additional calls to EVP_DigestUpdate() can be 295made, but EVP_DigestInit_ex2() can be called to initialize a new operation. 296 297=item EVP_MD_CTX_copy_ex() 298 299Can be used to copy the message digest state from I<in> to I<out>. This is 300useful if large amounts of data are to be hashed which only differ in the last 301few bytes. 302 303=item EVP_DigestInit() 304 305Behaves in the same way as EVP_DigestInit_ex2() except it doesn't set any 306parameters and calls EVP_MD_CTX_reset() so it cannot be used with an I<type> 307of NULL. 308 309=item EVP_DigestFinal() 310 311Similar to EVP_DigestFinal_ex() except after computing the digest 312the digest context I<ctx> is automatically cleaned up with EVP_MD_CTX_reset(). 313 314=item EVP_MD_CTX_copy() 315 316Similar to EVP_MD_CTX_copy_ex() except the destination I<out> does not have to 317be initialized. 318 319=item EVP_MD_is_a() 320 321Returns 1 if I<md> is an implementation of an algorithm that's 322identifiable with I<name>, otherwise 0. 323 324If I<md> is a legacy digest (it's the return value from the likes of 325EVP_sha256() rather than the result of an EVP_MD_fetch()), only cipher 326names registered with the default library context (see 327L<OSSL_LIB_CTX(3)>) will be considered. 328 329=item EVP_MD_get0_name(), 330EVP_MD_CTX_get0_name() 331 332Return the name of the given message digest. For fetched message 333digests with multiple names, only one of them is returned; it's 334recommended to use EVP_MD_names_do_all() instead. 335 336=item EVP_MD_names_do_all() 337 338Traverses all names for the I<md>, and calls I<fn> with each name and 339I<data>. This is only useful with fetched B<EVP_MD>s. 340 341=item EVP_MD_get0_description() 342 343Returns a description of the digest, meant for display and human consumption. 344The description is at the discretion of the digest implementation. 345 346=item EVP_MD_get0_provider() 347 348Returns an B<OSSL_PROVIDER> pointer to the provider that implements the given 349B<EVP_MD>. 350 351=item EVP_MD_get_size(), 352EVP_MD_CTX_get_size() 353 354Return the size of the message digest when passed an B<EVP_MD> or an 355B<EVP_MD_CTX> structure, i.e. the size of the hash. 356 357=item EVP_MD_get_block_size(), 358EVP_MD_CTX_get_block_size() 359 360Return the block size of the message digest when passed an B<EVP_MD> or an 361B<EVP_MD_CTX> structure. 362 363=item EVP_MD_get_type(), 364EVP_MD_CTX_get_type() 365 366Return the NID of the OBJECT IDENTIFIER representing the given message digest 367when passed an B<EVP_MD> structure. For example, C<EVP_MD_get_type(EVP_sha1())> 368returns B<NID_sha1>. This function is normally used when setting ASN1 OIDs. 369 370=item EVP_MD_CTX_get0_md_data() 371 372Return the digest method private data for the passed B<EVP_MD_CTX>. 373The space is allocated by OpenSSL and has the size originally set with 374EVP_MD_meth_set_app_datasize(). 375 376=item EVP_MD_CTX_get0_md(), EVP_MD_CTX_get1_md() 377 378EVP_MD_CTX_get0_md() returns 379the B<EVP_MD> structure corresponding to the passed B<EVP_MD_CTX>. This 380will be the same B<EVP_MD> object originally passed to EVP_DigestInit_ex2() (or 381other similar function) when the EVP_MD_CTX was first initialised. Note that 382where explicit fetch is in use (see L<EVP_MD_fetch(3)>) the value returned from 383this function will not have its reference count incremented and therefore it 384should not be used after the EVP_MD_CTX is freed. 385EVP_MD_CTX_get1_md() is the same except the ownership is passed to the 386caller and is from the passed B<EVP_MD_CTX>. 387 388=item EVP_MD_CTX_set_update_fn() 389 390Sets the update function for I<ctx> to I<update>. 391This is the function that is called by EVP_DigestUpdate(). If not set, the 392update function from the B<EVP_MD> type specified at initialization is used. 393 394=item EVP_MD_CTX_update_fn() 395 396Returns the update function for I<ctx>. 397 398=item EVP_MD_get_flags() 399 400Returns the I<md> flags. Note that these are different from the B<EVP_MD_CTX> 401ones. See L<EVP_MD_meth_set_flags(3)> for more information. 402 403=item EVP_MD_get_pkey_type() 404 405Returns the NID of the public key signing algorithm associated with this 406digest. For example EVP_sha1() is associated with RSA so this will return 407B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms are no 408longer linked this function is only retained for compatibility reasons. 409 410=item EVP_md_null() 411 412A "null" message digest that does nothing: i.e. the hash it returns is of zero 413length. 414 415=item EVP_get_digestbyname(), 416EVP_get_digestbynid(), 417EVP_get_digestbyobj() 418 419Returns an B<EVP_MD> structure when passed a digest name, a digest B<NID> or an 420B<ASN1_OBJECT> structure respectively. 421 422The EVP_get_digestbyname() function is present for backwards compatibility with 423OpenSSL prior to version 3 and is different to the EVP_MD_fetch() function 424since it does not attempt to "fetch" an implementation of the cipher. 425Additionally, it only knows about digests that are built-in to OpenSSL and have 426an associated NID. Similarly EVP_get_digestbynid() and EVP_get_digestbyobj() 427also return objects without an associated implementation. 428 429When the digest objects returned by these functions are used (such as in a call 430to EVP_DigestInit_ex()) an implementation of the digest will be implicitly 431fetched from the loaded providers. This fetch could fail if no suitable 432implementation is available. Use EVP_MD_fetch() instead to explicitly fetch 433the algorithm and an associated implementation from a provider. 434 435See L<crypto(7)/ALGORITHM FETCHING> for more information about fetching. 436 437The digest objects returned from these functions do not need to be freed with 438EVP_MD_free(). 439 440=item EVP_MD_CTX_get_pkey_ctx() 441 442Returns the B<EVP_PKEY_CTX> assigned to I<ctx>. The returned pointer should not 443be freed by the caller. 444 445=item EVP_MD_CTX_set_pkey_ctx() 446 447Assigns an B<EVP_PKEY_CTX> to B<EVP_MD_CTX>. This is usually used to provide 448a customized B<EVP_PKEY_CTX> to L<EVP_DigestSignInit(3)> or 449L<EVP_DigestVerifyInit(3)>. The I<pctx> passed to this function should be freed 450by the caller. A NULL I<pctx> pointer is also allowed to clear the B<EVP_PKEY_CTX> 451assigned to I<ctx>. In such case, freeing the cleared B<EVP_PKEY_CTX> or not 452depends on how the B<EVP_PKEY_CTX> is created. 453 454=item EVP_MD_do_all_provided() 455 456Traverses all messages digests implemented by all activated providers 457in the given library context I<libctx>, and for each of the implementations, 458calls the given function I<fn> with the implementation method and the given 459I<arg> as argument. 460 461=back 462 463=head1 PARAMETERS 464 465See L<OSSL_PARAM(3)> for information about passing parameters. 466 467EVP_MD_CTX_set_params() can be used with the following OSSL_PARAM keys: 468 469=over 4 470 471=item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer> 472 473Sets the digest length for extendable output functions. 474It is used by the SHAKE algorithm and should not exceed what can be given 475using a B<size_t>. 476 477=item "pad-type" (B<OSSL_DIGEST_PARAM_PAD_TYPE>) <unsigned integer> 478 479Sets the padding type. 480It is used by the MDC2 algorithm. 481 482=back 483 484EVP_MD_CTX_get_params() can be used with the following OSSL_PARAM keys: 485 486=over 4 487 488=item "micalg" (B<OSSL_DIGEST_PARAM_MICALG>) <UTF8 string>. 489 490Gets the digest Message Integrity Check algorithm string. This is used when 491creating S/MIME multipart/signed messages, as specified in RFC 3851. 492It may be used by external engines or providers. 493 494=back 495 496=head1 CONTROLS 497 498EVP_MD_CTX_ctrl() can be used to send the following standard controls: 499 500=over 4 501 502=item EVP_MD_CTRL_MICALG 503 504Gets the digest Message Integrity Check algorithm string. This is used when 505creating S/MIME multipart/signed messages, as specified in RFC 3851. 506The string value is written to I<p2>. 507 508When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with 509an L<OSSL_PARAM(3)> item with the key "micalg" (B<OSSL_DIGEST_PARAM_MICALG>). 510 511=item EVP_MD_CTRL_XOF_LEN 512 513This control sets the digest length for extendable output functions to I<p1>. 514Sending this control directly should not be necessary, the use of 515EVP_DigestFinalXOF() is preferred. 516Currently used by SHAKE. 517 518When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with 519an L<OSSL_PARAM(3)> item with the key "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>). 520 521=back 522 523=head1 FLAGS 524 525EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags() and EVP_MD_CTX_test_flags() 526can be used the manipulate and test these B<EVP_MD_CTX> flags: 527 528=over 4 529 530=item EVP_MD_CTX_FLAG_ONESHOT 531 532This flag instructs the digest to optimize for one update only, if possible. 533 534=item EVP_MD_CTX_FLAG_CLEANED 535 536This flag is for internal use only and I<must not> be used in user code. 537 538=item EVP_MD_CTX_FLAG_REUSE 539 540This flag is for internal use only and I<must not> be used in user code. 541 542=for comment We currently avoid documenting flags that are only bit holder: 543EVP_MD_CTX_FLAG_NON_FIPS_ALLOW, EVP_MD_CTX_FLAGS_PAD_* 544 545=item EVP_MD_CTX_FLAG_NO_INIT 546 547This flag instructs EVP_DigestInit() and similar not to initialise the 548implementation specific data. 549 550=item EVP_MD_CTX_FLAG_FINALISE 551 552Some functions such as EVP_DigestSign only finalise copies of internal 553contexts so additional data can be included after the finalisation call. 554This is inefficient if this functionality is not required, and can be 555disabled with this flag. 556 557=back 558 559=head1 RETURN VALUES 560 561=over 4 562 563=item EVP_MD_fetch() 564 565Returns a pointer to a B<EVP_MD> for success or NULL for failure. 566 567=item EVP_MD_up_ref() 568 569Returns 1 for success or 0 for failure. 570 571=item EVP_Q_digest(), 572EVP_Digest(), 573EVP_DigestInit_ex2(), 574EVP_DigestInit_ex(), 575EVP_DigestInit(), 576EVP_DigestUpdate(), 577EVP_DigestFinal_ex(), 578EVP_DigestFinalXOF(), and 579EVP_DigestFinal() 580 581return 1 for 582success and 0 for failure. 583 584=item EVP_MD_CTX_ctrl() 585 586Returns 1 if successful or 0 for failure. 587 588=item EVP_MD_CTX_set_params(), 589EVP_MD_CTX_get_params() 590 591Returns 1 if successful or 0 for failure. 592 593=item EVP_MD_CTX_settable_params(), 594EVP_MD_CTX_gettable_params() 595 596Return an array of constant L<OSSL_PARAM(3)>s, or NULL if there is none 597to get. 598 599=item EVP_MD_CTX_copy_ex() 600 601Returns 1 if successful or 0 for failure. 602 603=item EVP_MD_get_type(), 604EVP_MD_get_pkey_type() 605 606Returns the NID of the corresponding OBJECT IDENTIFIER or NID_undef if none 607exists. 608 609=item EVP_MD_get_size(), 610EVP_MD_get_block_size(), 611EVP_MD_CTX_get_size(), 612EVP_MD_CTX_get_block_size() 613 614Returns the digest or block size in bytes or -1 for failure. 615 616=item EVP_md_null() 617 618Returns a pointer to the B<EVP_MD> structure of the "null" message digest. 619 620=item EVP_get_digestbyname(), 621EVP_get_digestbynid(), 622EVP_get_digestbyobj() 623 624Returns either an B<EVP_MD> structure or NULL if an error occurs. 625 626=item EVP_MD_CTX_set_pkey_ctx() 627 628This function has no return value. 629 630=item EVP_MD_names_do_all() 631 632Returns 1 if the callback was called for all names. A return value of 0 means 633that the callback was not called for any names. 634 635=back 636 637=head1 NOTES 638 639The B<EVP> interface to message digests should almost always be used in 640preference to the low-level interfaces. This is because the code then becomes 641transparent to the digest used and much more flexible. 642 643New applications should use the SHA-2 (such as L<EVP_sha256(3)>) or the SHA-3 644digest algorithms (such as L<EVP_sha3_512(3)>). The other digest algorithms 645are still in common use. 646 647For most applications the I<impl> parameter to EVP_DigestInit_ex() will be 648set to NULL to use the default digest implementation. 649 650Ignoring failure returns of EVP_DigestInit_ex(), EVP_DigestInit_ex2(), or 651EVP_DigestInit() can lead to undefined behavior on subsequent calls 652updating or finalizing the B<EVP_MD_CTX> such as the EVP_DigestUpdate() or 653EVP_DigestFinal() functions. The only valid calls on the B<EVP_MD_CTX> 654when initialization fails are calls that attempt another initialization of 655the context or release the context. 656 657The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are 658obsolete but are retained to maintain compatibility with existing code. New 659applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and 660EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context 661instead of initializing and cleaning it up on each call and allow non default 662implementations of digests to be specified. 663 664If digest contexts are not cleaned up after use, 665memory leaks will occur. 666 667EVP_MD_CTX_get0_name(), EVP_MD_CTX_get_size(), EVP_MD_CTX_get_block_size(), 668EVP_MD_CTX_get_type(), EVP_get_digestbynid() and EVP_get_digestbyobj() are 669defined as macros. 670 671EVP_MD_CTX_ctrl() sends commands to message digests for additional configuration 672or control. 673 674=head1 EXAMPLES 675 676This example digests the data "Test Message\n" and "Hello World\n", using the 677digest name passed on the command line. 678 679 #include <stdio.h> 680 #include <string.h> 681 #include <openssl/evp.h> 682 683 int main(int argc, char *argv[]) 684 { 685 EVP_MD_CTX *mdctx; 686 const EVP_MD *md; 687 char mess1[] = "Test Message\n"; 688 char mess2[] = "Hello World\n"; 689 unsigned char md_value[EVP_MAX_MD_SIZE]; 690 unsigned int md_len, i; 691 692 if (argv[1] == NULL) { 693 printf("Usage: mdtest digestname\n"); 694 exit(1); 695 } 696 697 md = EVP_get_digestbyname(argv[1]); 698 if (md == NULL) { 699 printf("Unknown message digest %s\n", argv[1]); 700 exit(1); 701 } 702 703 mdctx = EVP_MD_CTX_new(); 704 if (!EVP_DigestInit_ex2(mdctx, md, NULL)) { 705 printf("Message digest initialization failed.\n"); 706 EVP_MD_CTX_free(mdctx); 707 exit(1); 708 } 709 if (!EVP_DigestUpdate(mdctx, mess1, strlen(mess1))) { 710 printf("Message digest update failed.\n"); 711 EVP_MD_CTX_free(mdctx); 712 exit(1); 713 } 714 if (!EVP_DigestUpdate(mdctx, mess2, strlen(mess2))) { 715 printf("Message digest update failed.\n"); 716 EVP_MD_CTX_free(mdctx); 717 exit(1); 718 } 719 if (!EVP_DigestFinal_ex(mdctx, md_value, &md_len)) { 720 printf("Message digest finalization failed.\n"); 721 EVP_MD_CTX_free(mdctx); 722 exit(1); 723 } 724 EVP_MD_CTX_free(mdctx); 725 726 printf("Digest is: "); 727 for (i = 0; i < md_len; i++) 728 printf("%02x", md_value[i]); 729 printf("\n"); 730 731 exit(0); 732 } 733 734=head1 SEE ALSO 735 736L<EVP_MD_meth_new(3)>, 737L<openssl-dgst(1)>, 738L<evp(7)>, 739L<OSSL_PROVIDER(3)>, 740L<OSSL_PARAM(3)>, 741L<property(7)>, 742L<crypto(7)/ALGORITHM FETCHING>, 743L<provider-digest(7)>, 744L<life_cycle-digest(7)> 745 746The full list of digest algorithms are provided below. 747 748L<EVP_blake2b512(3)>, 749L<EVP_md2(3)>, 750L<EVP_md4(3)>, 751L<EVP_md5(3)>, 752L<EVP_mdc2(3)>, 753L<EVP_ripemd160(3)>, 754L<EVP_sha1(3)>, 755L<EVP_sha224(3)>, 756L<EVP_sha3_224(3)>, 757L<EVP_sm3(3)>, 758L<EVP_whirlpool(3)> 759 760=head1 HISTORY 761 762The EVP_MD_CTX_create() and EVP_MD_CTX_destroy() functions were renamed to 763EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.0, respectively. 764 765The link between digests and signing algorithms was fixed in OpenSSL 1.0 and 766later, so now EVP_sha1() can be used with RSA and DSA. 767 768The EVP_dss1() function was removed in OpenSSL 1.1.0. 769 770The EVP_MD_CTX_set_pkey_ctx() function was added in OpenSSL 1.1.1. 771 772The EVP_Q_digest(), EVP_DigestInit_ex2(), 773EVP_MD_fetch(), EVP_MD_free(), EVP_MD_up_ref(), 774EVP_MD_get_params(), EVP_MD_CTX_set_params(), EVP_MD_CTX_get_params(), 775EVP_MD_gettable_params(), EVP_MD_gettable_ctx_params(), 776EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() and 777EVP_MD_CTX_gettable_params() functions were added in OpenSSL 3.0. 778 779The EVP_MD_type(), EVP_MD_nid(), EVP_MD_name(), EVP_MD_pkey_type(), 780EVP_MD_size(), EVP_MD_block_size(), EVP_MD_flags(), EVP_MD_CTX_size(), 781EVP_MD_CTX_block_size(), EVP_MD_CTX_type(), and EVP_MD_CTX_md_data() 782functions were renamed to include C<get> or C<get0> in their names in 783OpenSSL 3.0, respectively. The old names are kept as non-deprecated 784alias macros. 785 786The EVP_MD_CTX_md() function was deprecated in OpenSSL 3.0; use 787EVP_MD_CTX_get0_md() instead. 788EVP_MD_CTX_update_fn() and EVP_MD_CTX_set_update_fn() were deprecated 789in OpenSSL 3.0. 790 791=head1 COPYRIGHT 792 793Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved. 794 795Licensed under the Apache License 2.0 (the "License"). You may not use 796this file except in compliance with the License. You can obtain a copy 797in the file LICENSE in the source distribution or at 798L<https://www.openssl.org/source/license.html>. 799 800=cut 801