doc/man3/EVP_DigestInit.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 EVP_MD_fetch, EVP_MD_up_ref, EVP_MD_free,
   6 EVP_MD_get_params, EVP_MD_gettable_params,
   7 EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_dup,
   8 EVP_MD_CTX_copy, EVP_MD_CTX_copy_ex, EVP_MD_CTX_ctrl,
   9 EVP_MD_CTX_set_params, EVP_MD_CTX_get_params,
  10 EVP_MD_settable_ctx_params, EVP_MD_gettable_ctx_params,
  11 EVP_MD_CTX_settable_params, EVP_MD_CTX_gettable_params,
  12 EVP_MD_CTX_set_flags, EVP_MD_CTX_clear_flags, EVP_MD_CTX_test_flags,
  13 EVP_Q_digest, EVP_Digest, EVP_DigestInit_ex2, EVP_DigestInit_ex, EVP_DigestInit,
  14 EVP_DigestUpdate, EVP_DigestFinal_ex, EVP_DigestFinalXOF, EVP_DigestFinal,
  15 EVP_DigestSqueeze,
  16 EVP_MD_is_a, EVP_MD_get0_name, EVP_MD_get0_description,
  17 EVP_MD_names_do_all, EVP_MD_get0_provider, EVP_MD_get_type,
  18 EVP_MD_get_pkey_type, EVP_MD_get_size, EVP_MD_get_block_size, EVP_MD_get_flags,
  19 EVP_MD_CTX_get0_name, EVP_MD_CTX_md, EVP_MD_CTX_get0_md, EVP_MD_CTX_get1_md,
  20 EVP_MD_CTX_get_type, EVP_MD_CTX_get_size, EVP_MD_CTX_get_block_size,
  21 EVP_MD_CTX_get0_md_data, EVP_MD_CTX_update_fn, EVP_MD_CTX_set_update_fn,
  22 EVP_md_null,
  23 EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj,
  24 EVP_MD_CTX_get_pkey_ctx, EVP_MD_CTX_set_pkey_ctx,
  25 EVP_MD_do_all_provided,
  26 EVP_MD_type, EVP_MD_nid, EVP_MD_name, EVP_MD_pkey_type, EVP_MD_size,
  27 EVP_MD_block_size, EVP_MD_flags, EVP_MD_CTX_size, EVP_MD_CTX_block_size,
  28 EVP_MD_CTX_type, EVP_MD_CTX_pkey_ctx, EVP_MD_CTX_md_data
  29 - EVP digest routines
  30
  31 =head1 SYNOPSIS
  32
  33  #include <openssl/evp.h>
  34
  35  EVP_MD *EVP_MD_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
  36                       const char *properties);
  37  int EVP_MD_up_ref(EVP_MD *md);
  38  void EVP_MD_free(EVP_MD *md);
  39  int EVP_MD_get_params(const EVP_MD *digest, OSSL_PARAM params[]);
  40  const OSSL_PARAM *EVP_MD_gettable_params(const EVP_MD *digest);
  41  EVP_MD_CTX *EVP_MD_CTX_new(void);
  42  int EVP_MD_CTX_reset(EVP_MD_CTX *ctx);
  43  void EVP_MD_CTX_free(EVP_MD_CTX *ctx);
  44  void EVP_MD_CTX_ctrl(EVP_MD_CTX *ctx, int cmd, int p1, void* p2);
  45  int EVP_MD_CTX_get_params(EVP_MD_CTX *ctx, OSSL_PARAM params[]);
  46  int EVP_MD_CTX_set_params(EVP_MD_CTX *ctx, const OSSL_PARAM params[]);
  47  const OSSL_PARAM *EVP_MD_settable_ctx_params(const EVP_MD *md);
  48  const OSSL_PARAM *EVP_MD_gettable_ctx_params(const EVP_MD *md);
  49  const OSSL_PARAM *EVP_MD_CTX_settable_params(EVP_MD_CTX *ctx);
  50  const OSSL_PARAM *EVP_MD_CTX_gettable_params(EVP_MD_CTX *ctx);
  51  void EVP_MD_CTX_set_flags(EVP_MD_CTX *ctx, int flags);
  52  void EVP_MD_CTX_clear_flags(EVP_MD_CTX *ctx, int flags);
  53  int EVP_MD_CTX_test_flags(const EVP_MD_CTX *ctx, int flags);
  54
  55  int EVP_Q_digest(OSSL_LIB_CTX *libctx, const char *name, const char *propq,
  56                   const void *data, size_t datalen,
  57                   unsigned char *md, size_t *mdlen);
  58  int EVP_Digest(const void *data, size_t count, unsigned char *md,
  59                 unsigned int *size, const EVP_MD *type, ENGINE *impl);
  60  int EVP_DigestInit_ex2(EVP_MD_CTX *ctx, const EVP_MD *type,
  61                         const OSSL_PARAM params[]);
  62  int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl);
  63  int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt);
  64  int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s);
  65  int EVP_DigestFinalXOF(EVP_MD_CTX *ctx, unsigned char *out, size_t outlen);
  66  int EVP_DigestSqueeze(EVP_MD_CTX *ctx, unsigned char *out, size_t outlen);
  67
  68  EVP_MD_CTX *EVP_MD_CTX_dup(const EVP_MD_CTX *in);
  69  int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out, const EVP_MD_CTX *in);
  70
  71  int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type);
  72  int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s);
  73
  74  int EVP_MD_CTX_copy(EVP_MD_CTX *out, EVP_MD_CTX *in);
  75
  76  const char *EVP_MD_get0_name(const EVP_MD *md);
  77  const char *EVP_MD_get0_description(const EVP_MD *md);
  78  int EVP_MD_is_a(const EVP_MD *md, const char *name);
  79  int EVP_MD_names_do_all(const EVP_MD *md,
  80                          void (*fn)(const char *name, void *data),
  81                          void *data);
  82  const OSSL_PROVIDER *EVP_MD_get0_provider(const EVP_MD *md);
  83  int EVP_MD_get_type(const EVP_MD *md);
  84  int EVP_MD_get_pkey_type(const EVP_MD *md);
  85  int EVP_MD_get_size(const EVP_MD *md);
  86  int EVP_MD_get_block_size(const EVP_MD *md);
  87  unsigned long EVP_MD_get_flags(const EVP_MD *md);
  88
  89  const EVP_MD *EVP_MD_CTX_get0_md(const EVP_MD_CTX *ctx);
  90  EVP_MD *EVP_MD_CTX_get1_md(EVP_MD_CTX *ctx);
  91  const char *EVP_MD_CTX_get0_name(const EVP_MD_CTX *ctx);
  92  int EVP_MD_CTX_get_size(const EVP_MD_CTX *ctx);
  93  int EVP_MD_CTX_get_block_size(const EVP_MD_CTX *ctx);
  94  int EVP_MD_CTX_get_type(const EVP_MD_CTX *ctx);
  95  void *EVP_MD_CTX_get0_md_data(const EVP_MD_CTX *ctx);
  96
  97  const EVP_MD *EVP_md_null(void);
  98
  99  const EVP_MD *EVP_get_digestbyname(const char *name);
 100  const EVP_MD *EVP_get_digestbynid(int type);
 101  const EVP_MD *EVP_get_digestbyobj(const ASN1_OBJECT *o);
 102
 103  EVP_PKEY_CTX *EVP_MD_CTX_get_pkey_ctx(const EVP_MD_CTX *ctx);
 104  void EVP_MD_CTX_set_pkey_ctx(EVP_MD_CTX *ctx, EVP_PKEY_CTX *pctx);
 105
 106  void EVP_MD_do_all_provided(OSSL_LIB_CTX *libctx,
 107                              void (*fn)(EVP_MD *mac, void *arg),
 108                              void *arg);
 109
 110  #define EVP_MD_type EVP_MD_get_type
 111  #define EVP_MD_nid EVP_MD_get_type
 112  #define EVP_MD_name EVP_MD_get0_name
 113  #define EVP_MD_pkey_type EVP_MD_get_pkey_type
 114  #define EVP_MD_size EVP_MD_get_size
 115  #define EVP_MD_block_size EVP_MD_get_block_size
 116  #define EVP_MD_flags EVP_MD_get_flags
 117  #define EVP_MD_CTX_size EVP_MD_CTX_get_size
 118  #define EVP_MD_CTX_block_size EVP_MD_CTX_get_block_size
 119  #define EVP_MD_CTX_type EVP_MD_CTX_get_type
 120  #define EVP_MD_CTX_pkey_ctx EVP_MD_CTX_get_pkey_ctx
 121  #define EVP_MD_CTX_md_data EVP_MD_CTX_get0_md_data
 122
 123 The following functions have been deprecated since OpenSSL 3.0, and can be
 124 hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
 125 see L<openssl_user_macros(7)>:
 126
 127  const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx);
 128
 129  int (*EVP_MD_CTX_update_fn(EVP_MD_CTX *ctx))(EVP_MD_CTX *ctx,
 130                                               const void *data, size_t count);
 131
 132  void EVP_MD_CTX_set_update_fn(EVP_MD_CTX *ctx,
 133                                int (*update)(EVP_MD_CTX *ctx,
 134                                              const void *data, size_t count));
 135
 136 =head1 DESCRIPTION
 137
 138 The EVP digest routines are a high-level interface to message digests,
 139 and should be used instead of the digest-specific functions.
 140
 141 The B<EVP_MD> type is a structure for digest method implementation.
 142
 143 =over 4
 144
 145 =item EVP_MD_fetch()
 146
 147 Fetches the digest implementation for the given I<algorithm> from any
 148 provider offering it, within the criteria given by the I<properties>.
 149 See L<crypto(7)/ALGORITHM FETCHING> for further information.
 150
 151 The returned value must eventually be freed with EVP_MD_free().
 152
 153 Fetched B<EVP_MD> structures are reference counted.
 154
 155 =item EVP_MD_up_ref()
 156
 157 Increments the reference count for an B<EVP_MD> structure.
 158
 159 =item EVP_MD_free()
 160
 161 Decrements the reference count for the fetched B<EVP_MD> structure.
 162 If the reference count drops to 0 then the structure is freed.
 163
 164 =item EVP_MD_CTX_new()
 165
 166 Allocates and returns a digest context.
 167
 168 =item EVP_MD_CTX_reset()
 169
 170 Resets the digest context I<ctx>.  This can be used to reuse an already
 171 existing context.
 172
 173 =item EVP_MD_CTX_free()
 174
 175 Cleans up digest context I<ctx> and frees up the space allocated to it.
 176
 177 =item EVP_MD_CTX_ctrl()
 178
 179 I<This is a legacy method. EVP_MD_CTX_set_params() and EVP_MD_CTX_get_params()
 180 is the mechanism that should be used to set and get parameters that are used by
 181 providers.>
 182
 183 Performs digest-specific control actions on context I<ctx>. The control command
 184 is indicated in I<cmd> and any additional arguments in I<p1> and I<p2>.
 185 EVP_MD_CTX_ctrl() must be called after EVP_DigestInit_ex2(). Other restrictions
 186 may apply depending on the control type and digest implementation.
 187
 188 If this function happens to be used with a fetched B<EVP_MD>, it will
 189 translate the controls that are known to OpenSSL into L<OSSL_PARAM(3)>
 190 parameters with keys defined by OpenSSL and call EVP_MD_CTX_get_params() or
 191 EVP_MD_CTX_set_params() as is appropriate for each control command.
 192
 193 See L</CONTROLS> below for more information, including what translations are
 194 being done.
 195
 196 =item EVP_MD_get_params()
 197
 198 Retrieves the requested list of I<params> from a MD I<md>.
 199 See L</PARAMETERS> below for more information.
 200
 201 =item EVP_MD_CTX_get_params()
 202
 203 Retrieves the requested list of I<params> from a MD context I<ctx>.
 204 See L</PARAMETERS> below for more information.
 205
 206 =item EVP_MD_CTX_set_params()
 207
 208 Sets the list of I<params> into a MD context I<ctx>.
 209 See L</PARAMETERS> below for more information.
 210
 211 =item EVP_MD_gettable_params()
 212
 213 Get a constant L<OSSL_PARAM(3)> array that describes the retrievable parameters
 214 that can be used with EVP_MD_get_params().
 215
 216 =item EVP_MD_gettable_ctx_params(), EVP_MD_CTX_gettable_params()
 217
 218 Get a constant L<OSSL_PARAM(3)> array that describes the retrievable parameters
 219 that can be used with EVP_MD_CTX_get_params().  EVP_MD_gettable_ctx_params()
 220 returns the parameters that can be retrieved from the algorithm, whereas
 221 EVP_MD_CTX_gettable_params() returns the parameters that can be retrieved
 222 in the context's current state.
 223
 224 =item EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params()
 225
 226 Get a constant L<OSSL_PARAM(3)> array that describes the settable parameters
 227 that can be used with EVP_MD_CTX_set_params().  EVP_MD_settable_ctx_params()
 228 returns the parameters that can be set from the algorithm, whereas
 229 EVP_MD_CTX_settable_params() returns the parameters that can be set in the
 230 context's current state.
 231
 232 =item EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), EVP_MD_CTX_test_flags()
 233
 234 Sets, 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
 238 It hashes I<datalen> bytes of data at I<data> using the digest algorithm
 239 I<name>, which is fetched using the optional I<libctx> and I<propq> parameters.
 240 The digest value is placed in I<md> and its length is written at I<mdlen>
 241 if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written.
 242
 243 =item EVP_Digest()
 244
 245 A wrapper around the Digest Init_ex, Update and Final_ex functions.
 246 Hashes I<count> bytes of data at I<data> using a digest I<type> from ENGINE
 247 I<impl>. The digest value is placed in I<md> and its length is written at I<size>
 248 if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written.
 249 If I<impl> is NULL the default implementation of digest I<type> is used.
 250
 251 =item EVP_DigestInit_ex2()
 252
 253 Sets up digest context I<ctx> to use a digest I<type>.
 254 I<type> is typically supplied by a function such as EVP_sha1(), or a
 255 value explicitly fetched with EVP_MD_fetch().
 256
 257 The parameters B<params> are set on the context after initialisation.
 258
 259 The I<type> parameter can be NULL if I<ctx> has been already initialized
 260 with another EVP_DigestInit_ex() call and has not been reset with
 261 EVP_MD_CTX_reset().
 262
 263 =item EVP_DigestInit_ex()
 264
 265 Sets up digest context I<ctx> to use a digest I<type>.
 266 I<type> is typically supplied by a function such as EVP_sha1(), or a
 267 value explicitly fetched with EVP_MD_fetch().
 268
 269 If I<impl> is non-NULL, its implementation of the digest I<type> is used if
 270 there is one, and if not, the default implementation is used.
 271
 272 The I<type> parameter can be NULL if I<ctx> has been already initialized
 273 with another EVP_DigestInit_ex() call and has not been reset with
 274 EVP_MD_CTX_reset().
 275
 276 =item EVP_DigestUpdate()
 277
 278 Hashes I<cnt> bytes of data at I<d> into the digest context I<ctx>. This
 279 function can be called several times on the same I<ctx> to hash additional
 280 data.
 281
 282 =item EVP_DigestFinal_ex()
 283
 284 Retrieves the digest value from I<ctx> and places it in I<md>. If the I<s>
 285 parameter is not NULL then the number of bytes of data written (i.e. the
 286 length of the digest) will be written to the integer at I<s>, at most
 287 B<EVP_MAX_MD_SIZE> bytes will be written unless the digest implementation
 288 allows changing the digest size and it is set to a larger value by the
 289 application. After calling EVP_DigestFinal_ex() no additional calls to
 290 EVP_DigestUpdate() can be made, but EVP_DigestInit_ex2() can be called to
 291 initialize a new digest operation.
 292
 293 =item EVP_DigestFinalXOF()
 294
 295 Interfaces to extendable-output functions, XOFs, such as SHAKE128 and SHAKE256.
 296 It retrieves the digest value from I<ctx> and places it in I<outlen>-sized I<out>.
 297 After calling this function no additional calls to EVP_DigestUpdate() can be
 298 made, but EVP_DigestInit_ex2() can be called to initialize a new operation.
 299 EVP_DigestFinalXOF() may only be called once
 300
 301 =item EVP_DigestSqueeze()
 302
 303 Similar to EVP_DigestFinalXOF() but allows multiple calls to be made to
 304 squeeze variable length output data.
 305 EVP_DigestFinalXOF() should not be called after this.
 306
 307 =item EVP_MD_CTX_dup()
 308
 309 Can be used to duplicate the message digest state from I<in>.  This is useful
 310 to avoid multiple EVP_MD_fetch() calls or if large amounts of data are to be
 311 hashed which only differ in the last few bytes.
 312
 313 =item EVP_MD_CTX_copy_ex()
 314
 315 Can be used to copy the message digest state from I<in> to I<out>. This is
 316 useful if large amounts of data are to be hashed which only differ in the last
 317 few bytes.
 318
 319 =item EVP_DigestInit()
 320
 321 Behaves in the same way as EVP_DigestInit_ex2() except it doesn't set any
 322 parameters and calls EVP_MD_CTX_reset() so it cannot be used with an I<type>
 323 of NULL.
 324
 325 =item EVP_DigestFinal()
 326
 327 Similar to EVP_DigestFinal_ex() except after computing the digest
 328 the digest context I<ctx> is automatically cleaned up with EVP_MD_CTX_reset().
 329
 330 =item EVP_MD_CTX_copy()
 331
 332 Similar to EVP_MD_CTX_copy_ex() except the destination I<out> does not have to
 333 be initialized.
 334
 335 =item EVP_MD_is_a()
 336
 337 Returns 1 if I<md> is an implementation of an algorithm that's
 338 identifiable with I<name>, otherwise 0.
 339
 340 If I<md> is a legacy digest (it's the return value from the likes of
 341 EVP_sha256() rather than the result of an EVP_MD_fetch()), only cipher
 342 names registered with the default library context (see
 343 L<OSSL_LIB_CTX(3)>) will be considered.
 344
 345 =item EVP_MD_get0_name(),
 346 EVP_MD_CTX_get0_name()
 347
 348 Return the name of the given message digest.  For fetched message
 349 digests with multiple names, only one of them is returned; it's
 350 recommended to use EVP_MD_names_do_all() instead.
 351
 352 =item EVP_MD_names_do_all()
 353
 354 Traverses all names for the I<md>, and calls I<fn> with each name and
 355 I<data>.  This is only useful with fetched B<EVP_MD>s.
 356
 357 =item EVP_MD_get0_description()
 358
 359 Returns a description of the digest, meant for display and human consumption.
 360 The description is at the discretion of the digest implementation.
 361
 362 =item EVP_MD_get0_provider()
 363
 364 Returns an B<OSSL_PROVIDER> pointer to the provider that implements the given
 365 B<EVP_MD>.
 366
 367 =item EVP_MD_get_size(),
 368 EVP_MD_CTX_get_size()
 369
 370 Return the size of the message digest when passed an B<EVP_MD> or an
 371 B<EVP_MD_CTX> structure, i.e. the size of the hash.
 372
 373 =item EVP_MD_get_block_size(),
 374 EVP_MD_CTX_get_block_size()
 375
 376 Return the block size of the message digest when passed an B<EVP_MD> or an
 377 B<EVP_MD_CTX> structure.
 378
 379 =item EVP_MD_get_type(),
 380 EVP_MD_CTX_get_type()
 381
 382 Return the NID of the OBJECT IDENTIFIER representing the given message digest
 383 when passed an B<EVP_MD> structure.  For example, C<EVP_MD_get_type(EVP_sha1())>
 384 returns B<NID_sha1>. This function is normally used when setting ASN1 OIDs.
 385
 386 =item EVP_MD_CTX_get0_md_data()
 387
 388 Return the digest method private data for the passed B<EVP_MD_CTX>.
 389 The space is allocated by OpenSSL and has the size originally set with
 390 EVP_MD_meth_set_app_datasize().
 391
 392 =item EVP_MD_CTX_get0_md(), EVP_MD_CTX_get1_md()
 393
 394 EVP_MD_CTX_get0_md() returns
 395 the B<EVP_MD> structure corresponding to the passed B<EVP_MD_CTX>. This
 396 will be the same B<EVP_MD> object originally passed to EVP_DigestInit_ex2() (or
 397 other similar function) when the EVP_MD_CTX was first initialised. Note that
 398 where explicit fetch is in use (see L<EVP_MD_fetch(3)>) the value returned from
 399 this function will not have its reference count incremented and therefore it
 400 should not be used after the EVP_MD_CTX is freed.
 401 EVP_MD_CTX_get1_md() is the same except the ownership is passed to the
 402 caller and is from the passed B<EVP_MD_CTX>.
 403
 404 =item EVP_MD_CTX_set_update_fn()
 405
 406 Sets the update function for I<ctx> to I<update>.
 407 This is the function that is called by EVP_DigestUpdate(). If not set, the
 408 update function from the B<EVP_MD> type specified at initialization is used.
 409
 410 =item EVP_MD_CTX_update_fn()
 411
 412 Returns the update function for I<ctx>.
 413
 414 =item EVP_MD_get_flags()
 415
 416 Returns the I<md> flags. Note that these are different from the B<EVP_MD_CTX>
 417 ones. See L<EVP_MD_meth_set_flags(3)> for more information.
 418
 419 =item EVP_MD_get_pkey_type()
 420
 421 Returns the NID of the public key signing algorithm associated with this
 422 digest. For example EVP_sha1() is associated with RSA so this will return
 423 B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms are no
 424 longer linked this function is only retained for compatibility reasons.
 425
 426 =item EVP_md_null()
 427
 428 A "null" message digest that does nothing: i.e. the hash it returns is of zero
 429 length.
 430
 431 =item EVP_get_digestbyname(),
 432 EVP_get_digestbynid(),
 433 EVP_get_digestbyobj()
 434
 435 Returns an B<EVP_MD> structure when passed a digest name, a digest B<NID> or an
 436 B<ASN1_OBJECT> structure respectively.
 437
 438 The EVP_get_digestbyname() function is present for backwards compatibility with
 439 OpenSSL prior to version 3 and is different to the EVP_MD_fetch() function
 440 since it does not attempt to "fetch" an implementation of the cipher.
 441 Additionally, it only knows about digests that are built-in to OpenSSL and have
 442 an associated NID. Similarly EVP_get_digestbynid() and EVP_get_digestbyobj()
 443 also return objects without an associated implementation.
 444
 445 When the digest objects returned by these functions are used (such as in a call
 446 to EVP_DigestInit_ex()) an implementation of the digest will be implicitly
 447 fetched from the loaded providers. This fetch could fail if no suitable
 448 implementation is available. Use EVP_MD_fetch() instead to explicitly fetch
 449 the algorithm and an associated implementation from a provider.
 450
 451 See L<crypto(7)/ALGORITHM FETCHING> for more information about fetching.
 452
 453 The digest objects returned from these functions do not need to be freed with
 454 EVP_MD_free().
 455
 456 =item EVP_MD_CTX_get_pkey_ctx()
 457
 458 Returns the B<EVP_PKEY_CTX> assigned to I<ctx>. The returned pointer should not
 459 be freed by the caller.
 460
 461 =item EVP_MD_CTX_set_pkey_ctx()
 462
 463 Assigns an B<EVP_PKEY_CTX> to B<EVP_MD_CTX>. This is usually used to provide
 464 a customized B<EVP_PKEY_CTX> to L<EVP_DigestSignInit(3)> or
 465 L<EVP_DigestVerifyInit(3)>. The I<pctx> passed to this function should be freed
 466 by the caller. A NULL I<pctx> pointer is also allowed to clear the B<EVP_PKEY_CTX>
 467 assigned to I<ctx>. In such case, freeing the cleared B<EVP_PKEY_CTX> or not
 468 depends on how the B<EVP_PKEY_CTX> is created.
 469
 470 =item EVP_MD_do_all_provided()
 471
 472 Traverses all messages digests implemented by all activated providers
 473 in the given library context I<libctx>, and for each of the implementations,
 474 calls the given function I<fn> with the implementation method and the given
 475 I<arg> as argument.
 476
 477 =back
 478
 479 =head1 PARAMETERS
 480
 481 See L<OSSL_PARAM(3)> for information about passing parameters.
 482
 483 EVP_MD_CTX_set_params() can be used with the following OSSL_PARAM keys:
 484
 485 =over 4
 486
 487 =item "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>) <unsigned integer>
 488
 489 Sets the digest length for extendable output functions.
 490 The value should not exceed what can be given using a B<size_t>.
 491 It may be used by BLAKE2B-512, SHAKE-128 and SHAKE-256 to set the
 492 output length used by EVP_DigestFinal_ex() and EVP_DigestFinal().
 493
 494 =item "pad-type" (B<OSSL_DIGEST_PARAM_PAD_TYPE>) <unsigned integer>
 495
 496 Sets the padding type.
 497 It is used by the MDC2 algorithm.
 498
 499 =back
 500
 501 EVP_MD_CTX_get_params() can be used with the following OSSL_PARAM keys:
 502
 503 =over 4
 504
 505 =item "micalg" (B<OSSL_DIGEST_PARAM_MICALG>) <UTF8 string>.
 506
 507 Gets the digest Message Integrity Check algorithm string. This is used when
 508 creating S/MIME multipart/signed messages, as specified in RFC 3851.
 509 It may be used by external engines or providers.
 510
 511 =back
 512
 513 =head1 CONTROLS
 514
 515 EVP_MD_CTX_ctrl() can be used to send the following standard controls:
 516
 517 =over 4
 518
 519 =item EVP_MD_CTRL_MICALG
 520
 521 Gets the digest Message Integrity Check algorithm string. This is used when
 522 creating S/MIME multipart/signed messages, as specified in RFC 3851.
 523 The string value is written to I<p2>.
 524
 525 When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with
 526 an L<OSSL_PARAM(3)> item with the key "micalg" (B<OSSL_DIGEST_PARAM_MICALG>).
 527
 528 =item EVP_MD_CTRL_XOF_LEN
 529
 530 This control sets the digest length for extendable output functions to I<p1>.
 531 Sending this control directly should not be necessary, the use of
 532 EVP_DigestFinalXOF() is preferred.
 533 Currently used by SHAKE.
 534
 535 When used with a fetched B<EVP_MD>, EVP_MD_CTX_get_params() gets called with
 536 an L<OSSL_PARAM(3)> item with the key "xoflen" (B<OSSL_DIGEST_PARAM_XOFLEN>).
 537
 538 =back
 539
 540 =head1 FLAGS
 541
 542 EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags() and EVP_MD_CTX_test_flags()
 543 can be used the manipulate and test these B<EVP_MD_CTX> flags:
 544
 545 =over 4
 546
 547 =item EVP_MD_CTX_FLAG_ONESHOT
 548
 549 This flag instructs the digest to optimize for one update only, if possible.
 550
 551 =for comment EVP_MD_CTX_FLAG_CLEANED is internal, don't mention it
 552
 553 =for comment EVP_MD_CTX_FLAG_REUSE is internal, don't mention it
 554
 555 =for comment We currently avoid documenting flags that are only bit holder:
 556 EVP_MD_CTX_FLAG_NON_FIPS_ALLOW, EVP_MD_CTX_FLAGS_PAD_*
 557
 558 =item EVP_MD_CTX_FLAG_NO_INIT
 559
 560 This flag instructs EVP_DigestInit() and similar not to initialise the
 561 implementation specific data.
 562
 563 =item EVP_MD_CTX_FLAG_FINALISE
 564
 565 Some functions such as EVP_DigestSign only finalise copies of internal
 566 contexts so additional data can be included after the finalisation call.
 567 This is inefficient if this functionality is not required, and can be
 568 disabled with this flag.
 569
 570 =back
 571
 572 =head1 RETURN VALUES
 573
 574 =over 4
 575
 576 =item EVP_MD_fetch()
 577
 578 Returns a pointer to a B<EVP_MD> for success or NULL for failure.
 579
 580 =item EVP_MD_up_ref()
 581
 582 Returns 1 for success or 0 for failure.
 583
 584 =item EVP_Q_digest(),
 585 EVP_Digest(),
 586 EVP_DigestInit_ex2(),
 587 EVP_DigestInit_ex(),
 588 EVP_DigestInit(),
 589 EVP_DigestUpdate(),
 590 EVP_DigestFinal_ex(),
 591 EVP_DigestFinalXOF(), and
 592 EVP_DigestFinal()
 593
 594 return 1 for
 595 success and 0 for failure.
 596
 597 =item EVP_MD_CTX_ctrl()
 598
 599 Returns 1 if successful or 0 for failure.
 600
 601 =item EVP_MD_CTX_set_params(),
 602 EVP_MD_CTX_get_params()
 603
 604 Returns 1 if successful or 0 for failure.
 605
 606 =item EVP_MD_CTX_settable_params(),
 607 EVP_MD_CTX_gettable_params()
 608
 609 Return an array of constant L<OSSL_PARAM(3)>s, or NULL if there is none
 610 to get.
 611
 612 =item EVP_MD_CTX_dup()
 613
 614 Returns a new EVP_MD_CTX if successful or NULL on failure.
 615
 616 =item EVP_MD_CTX_copy_ex()
 617
 618 Returns 1 if successful or 0 for failure.
 619
 620 =item EVP_MD_get_type(),
 621 EVP_MD_get_pkey_type()
 622
 623 Returns the NID of the corresponding OBJECT IDENTIFIER or NID_undef if none
 624 exists.
 625
 626 =item EVP_MD_get_size(),
 627 EVP_MD_get_block_size(),
 628 EVP_MD_CTX_get_size(),
 629 EVP_MD_CTX_get_block_size()
 630
 631 Returns the digest or block size in bytes or -1 for failure.
 632
 633 =item EVP_md_null()
 634
 635 Returns a pointer to the B<EVP_MD> structure of the "null" message digest.
 636
 637 =item EVP_get_digestbyname(),
 638 EVP_get_digestbynid(),
 639 EVP_get_digestbyobj()
 640
 641 Returns either an B<EVP_MD> structure or NULL if an error occurs.
 642
 643 =item EVP_MD_CTX_set_pkey_ctx()
 644
 645 This function has no return value.
 646
 647 =item EVP_MD_names_do_all()
 648
 649 Returns 1 if the callback was called for all names. A return value of 0 means
 650 that the callback was not called for any names.
 651
 652 =back
 653
 654 =head1 NOTES
 655
 656 The B<EVP> interface to message digests should almost always be used in
 657 preference to the low-level interfaces. This is because the code then becomes
 658 transparent to the digest used and much more flexible.
 659
 660 New applications should use the SHA-2 (such as L<EVP_sha256(3)>) or the SHA-3
 661 digest algorithms (such as L<EVP_sha3_512(3)>). The other digest algorithms
 662 are still in common use.
 663
 664 For most applications the I<impl> parameter to EVP_DigestInit_ex() will be
 665 set to NULL to use the default digest implementation.
 666
 667 Ignoring failure returns of EVP_DigestInit_ex(), EVP_DigestInit_ex2(), or
 668 EVP_DigestInit() can lead to undefined behavior on subsequent calls
 669 updating or finalizing the B<EVP_MD_CTX> such as the EVP_DigestUpdate() or
 670 EVP_DigestFinal() functions. The only valid calls on the B<EVP_MD_CTX>
 671 when initialization fails are calls that attempt another initialization of
 672 the context or release the context.
 673
 674 The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are
 675 obsolete but are retained to maintain compatibility with existing code. New
 676 applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and
 677 EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context
 678 instead of initializing and cleaning it up on each call and allow non default
 679 implementations of digests to be specified.
 680
 681 If digest contexts are not cleaned up after use,
 682 memory leaks will occur.
 683
 684 EVP_MD_CTX_get0_name(), EVP_MD_CTX_get_size(), EVP_MD_CTX_get_block_size(),
 685 EVP_MD_CTX_get_type(), EVP_get_digestbynid() and EVP_get_digestbyobj() are
 686 defined as macros.
 687
 688 EVP_MD_CTX_ctrl() sends commands to message digests for additional configuration
 689 or control.
 690
 691 =head1 EXAMPLES
 692
 693 This example digests the data "Test Message\n" and "Hello World\n", using the
 694 digest name passed on the command line.
 695
 696  #include <stdio.h>
 697  #include <string.h>
 698  #include <openssl/evp.h>
 699
 700  int main(int argc, char *argv[])
 701  {
 702      EVP_MD_CTX *mdctx;
 703      const EVP_MD *md;
 704      char mess1[] = "Test Message\n";
 705      char mess2[] = "Hello World\n";
 706      unsigned char md_value[EVP_MAX_MD_SIZE];
 707      unsigned int md_len, i;
 708
 709      if (argv[1] == NULL) {
 710          printf("Usage: mdtest digestname\n");
 711          exit(1);
 712      }
 713
 714      md = EVP_get_digestbyname(argv[1]);
 715      if (md == NULL) {
 716          printf("Unknown message digest %s\n", argv[1]);
 717          exit(1);
 718      }
 719
 720      mdctx = EVP_MD_CTX_new();
 721      if (!EVP_DigestInit_ex2(mdctx, md, NULL)) {
 722          printf("Message digest initialization failed.\n");
 723          EVP_MD_CTX_free(mdctx);
 724          exit(1);
 725      }
 726      if (!EVP_DigestUpdate(mdctx, mess1, strlen(mess1))) {
 727          printf("Message digest update failed.\n");
 728          EVP_MD_CTX_free(mdctx);
 729          exit(1);
 730      }
 731      if (!EVP_DigestUpdate(mdctx, mess2, strlen(mess2))) {
 732          printf("Message digest update failed.\n");
 733          EVP_MD_CTX_free(mdctx);
 734          exit(1);
 735      }
 736      if (!EVP_DigestFinal_ex(mdctx, md_value, &md_len)) {
 737          printf("Message digest finalization failed.\n");
 738          EVP_MD_CTX_free(mdctx);
 739          exit(1);
 740      }
 741      EVP_MD_CTX_free(mdctx);
 742
 743      printf("Digest is: ");
 744      for (i = 0; i < md_len; i++)
 745          printf("%02x", md_value[i]);
 746      printf("\n");
 747
 748      exit(0);
 749  }
 750
 751 =head1 SEE ALSO
 752
 753 L<EVP_MD_meth_new(3)>,
 754 L<openssl-dgst(1)>,
 755 L<evp(7)>,
 756 L<OSSL_PROVIDER(3)>,
 757 L<OSSL_PARAM(3)>,
 758 L<property(7)>,
 759 L<crypto(7)/ALGORITHM FETCHING>,
 760 L<provider-digest(7)>,
 761 L<life_cycle-digest(7)>
 762
 763 The full list of digest algorithms are provided below.
 764
 765 L<EVP_blake2b512(3)>,
 766 L<EVP_md2(3)>,
 767 L<EVP_md4(3)>,
 768 L<EVP_md5(3)>,
 769 L<EVP_mdc2(3)>,
 770 L<EVP_ripemd160(3)>,
 771 L<EVP_sha1(3)>,
 772 L<EVP_sha224(3)>,
 773 L<EVP_sha3_224(3)>,
 774 L<EVP_sm3(3)>,
 775 L<EVP_whirlpool(3)>
 776
 777 =head1 HISTORY
 778
 779 The EVP_MD_CTX_create() and EVP_MD_CTX_destroy() functions were renamed to
 780 EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.0, respectively.
 781
 782 The link between digests and signing algorithms was fixed in OpenSSL 1.0 and
 783 later, so now EVP_sha1() can be used with RSA and DSA.
 784
 785 The EVP_dss1() function was removed in OpenSSL 1.1.0.
 786
 787 The EVP_MD_CTX_set_pkey_ctx() function was added in OpenSSL 1.1.1.
 788
 789 The EVP_Q_digest(), EVP_DigestInit_ex2(),
 790 EVP_MD_fetch(), EVP_MD_free(), EVP_MD_up_ref(),
 791 EVP_MD_get_params(), EVP_MD_CTX_set_params(), EVP_MD_CTX_get_params(),
 792 EVP_MD_gettable_params(), EVP_MD_gettable_ctx_params(),
 793 EVP_MD_settable_ctx_params(), EVP_MD_CTX_settable_params() and
 794 EVP_MD_CTX_gettable_params() functions were added in OpenSSL 3.0.
 795
 796 The EVP_MD_type(), EVP_MD_nid(), EVP_MD_name(), EVP_MD_pkey_type(),
 797 EVP_MD_size(), EVP_MD_block_size(), EVP_MD_flags(), EVP_MD_CTX_size(),
 798 EVP_MD_CTX_block_size(), EVP_MD_CTX_type(), and EVP_MD_CTX_md_data()
 799 functions were renamed to include C<get> or C<get0> in their names in
 800 OpenSSL 3.0, respectively. The old names are kept as non-deprecated
 801 alias macros.
 802
 803 The EVP_MD_CTX_md() function was deprecated in OpenSSL 3.0; use
 804 EVP_MD_CTX_get0_md() instead.
 805 EVP_MD_CTX_update_fn() and EVP_MD_CTX_set_update_fn() were deprecated
 806 in OpenSSL 3.0.
 807
 808 The EVP_MD_CTX_dup() function was added in OpenSSL 3.1.
 809
 810 The EVP_DigestSqueeze() function was added in OpenSSL 3.3.
 811
 812 =head1 COPYRIGHT
 813
 814 Copyright 2000-2024 The OpenSSL Project Authors. All Rights Reserved.
 815
 816 Licensed under the Apache License 2.0 (the "License").  You may not use
 817 this file except in compliance with the License.  You can obtain a copy
 818 in the file LICENSE in the source distribution or at
 819 L<https://www.openssl.org/source/license.html>.
 820
 821 =cut