1=pod 2 3=head1 NAME 4 5EVP_MD_CTX_new, EVP_MD_CTX_reset, EVP_MD_CTX_free, EVP_MD_CTX_copy, 6EVP_MD_CTX_copy_ex, EVP_MD_CTX_ctrl, EVP_MD_CTX_set_flags, 7EVP_MD_CTX_clear_flags, EVP_MD_CTX_test_flags, 8EVP_Digest, EVP_DigestInit_ex, EVP_DigestInit, EVP_DigestUpdate, 9EVP_DigestFinal_ex, EVP_DigestFinalXOF, EVP_DigestFinal, 10EVP_MD_type, EVP_MD_pkey_type, EVP_MD_size, EVP_MD_block_size, EVP_MD_flags, 11EVP_MD_CTX_md, EVP_MD_CTX_type, EVP_MD_CTX_size, EVP_MD_CTX_block_size, 12EVP_MD_CTX_md_data, EVP_MD_CTX_update_fn, EVP_MD_CTX_set_update_fn, 13EVP_md_null, 14EVP_get_digestbyname, EVP_get_digestbynid, EVP_get_digestbyobj, 15EVP_MD_CTX_pkey_ctx, EVP_MD_CTX_set_pkey_ctx - EVP digest routines 16 17=head1 SYNOPSIS 18 19 #include <openssl/evp.h> 20 21 EVP_MD_CTX *EVP_MD_CTX_new(void); 22 int EVP_MD_CTX_reset(EVP_MD_CTX *ctx); 23 void EVP_MD_CTX_free(EVP_MD_CTX *ctx); 24 void EVP_MD_CTX_ctrl(EVP_MD_CTX *ctx, int cmd, int p1, void* p2); 25 void EVP_MD_CTX_set_flags(EVP_MD_CTX *ctx, int flags); 26 void EVP_MD_CTX_clear_flags(EVP_MD_CTX *ctx, int flags); 27 int EVP_MD_CTX_test_flags(const EVP_MD_CTX *ctx, int flags); 28 29 int EVP_Digest(const void *data, size_t count, unsigned char *md, 30 unsigned int *size, const EVP_MD *type, ENGINE *impl); 31 int EVP_DigestInit_ex(EVP_MD_CTX *ctx, const EVP_MD *type, ENGINE *impl); 32 int EVP_DigestUpdate(EVP_MD_CTX *ctx, const void *d, size_t cnt); 33 int EVP_DigestFinal_ex(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s); 34 int EVP_DigestFinalXOF(EVP_MD_CTX *ctx, unsigned char *md, size_t len); 35 36 int EVP_MD_CTX_copy_ex(EVP_MD_CTX *out, const EVP_MD_CTX *in); 37 38 int EVP_DigestInit(EVP_MD_CTX *ctx, const EVP_MD *type); 39 int EVP_DigestFinal(EVP_MD_CTX *ctx, unsigned char *md, unsigned int *s); 40 41 int EVP_MD_CTX_copy(EVP_MD_CTX *out, EVP_MD_CTX *in); 42 43 int EVP_MD_type(const EVP_MD *md); 44 int EVP_MD_pkey_type(const EVP_MD *md); 45 int EVP_MD_size(const EVP_MD *md); 46 int EVP_MD_block_size(const EVP_MD *md); 47 unsigned long EVP_MD_flags(const EVP_MD *md); 48 49 const EVP_MD *EVP_MD_CTX_md(const EVP_MD_CTX *ctx); 50 int EVP_MD_CTX_size(const EVP_MD_CTX *ctx); 51 int EVP_MD_CTX_block_size(const EVP_MD_CTX *ctx); 52 int EVP_MD_CTX_type(const EVP_MD_CTX *ctx); 53 void *EVP_MD_CTX_md_data(const EVP_MD_CTX *ctx); 54 int (*EVP_MD_CTX_update_fn(EVP_MD_CTX *ctx))(EVP_MD_CTX *ctx, 55 const void *data, size_t count); 56 void EVP_MD_CTX_set_update_fn(EVP_MD_CTX *ctx, 57 int (*update)(EVP_MD_CTX *ctx, 58 const void *data, size_t count)); 59 60 const EVP_MD *EVP_md_null(void); 61 62 const EVP_MD *EVP_get_digestbyname(const char *name); 63 const EVP_MD *EVP_get_digestbynid(int type); 64 const EVP_MD *EVP_get_digestbyobj(const ASN1_OBJECT *o); 65 66 EVP_PKEY_CTX *EVP_MD_CTX_pkey_ctx(const EVP_MD_CTX *ctx); 67 void EVP_MD_CTX_set_pkey_ctx(EVP_MD_CTX *ctx, EVP_PKEY_CTX *pctx); 68 69=head1 DESCRIPTION 70 71The EVP digest routines are a high-level interface to message digests, 72and should be used instead of the cipher-specific functions. 73 74=over 4 75 76=item EVP_MD_CTX_new() 77 78Allocates and returns a digest context. 79 80=item EVP_MD_CTX_reset() 81 82Resets the digest context B<ctx>. This can be used to reuse an already 83existing context. 84 85=item EVP_MD_CTX_free() 86 87Cleans up digest context B<ctx> and frees up the space allocated to it. 88 89=item EVP_MD_CTX_ctrl() 90 91Performs digest-specific control actions on context B<ctx>. The control command 92is indicated in B<cmd> and any additional arguments in B<p1> and B<p2>. 93EVP_MD_CTX_ctrl() must be called after EVP_DigestInit_ex(). Other restrictions 94may apply depending on the control type and digest implementation. 95See L</CONTROLS> below for more information. 96 97=item EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags(), EVP_MD_CTX_test_flags() 98 99Sets, clears and tests B<ctx> flags. See L</FLAGS> below for more information. 100 101=item EVP_Digest() 102 103A wrapper around the Digest Init_ex, Update and Final_ex functions. 104Hashes B<count> bytes of data at B<data> using a digest B<type> from ENGINE 105B<impl>. The digest value is placed in B<md> and its length is written at B<size> 106if the pointer is not NULL. At most B<EVP_MAX_MD_SIZE> bytes will be written. 107If B<impl> is NULL the default implementation of digest B<type> is used. 108 109=item EVP_DigestInit_ex() 110 111Sets up digest context B<ctx> to use a digest B<type> from ENGINE B<impl>. 112B<type> will typically be supplied by a function such as EVP_sha1(). If 113B<impl> is NULL then the default implementation of digest B<type> is used. 114 115=item EVP_DigestUpdate() 116 117Hashes B<cnt> bytes of data at B<d> into the digest context B<ctx>. This 118function can be called several times on the same B<ctx> to hash additional 119data. 120 121=item EVP_DigestFinal_ex() 122 123Retrieves the digest value from B<ctx> and places it in B<md>. If the B<s> 124parameter is not NULL then the number of bytes of data written (i.e. the 125length of the digest) will be written to the integer at B<s>, at most 126B<EVP_MAX_MD_SIZE> bytes will be written. After calling EVP_DigestFinal_ex() 127no additional calls to EVP_DigestUpdate() can be made, but 128EVP_DigestInit_ex() can be called to initialize a new digest operation. 129 130=item EVP_DigestFinalXOF() 131 132Interfaces to extendable-output functions, XOFs, such as SHAKE128 and SHAKE256. 133It retrieves the digest value from B<ctx> and places it in B<len>-sized <B>md. 134After calling this function no additional calls to EVP_DigestUpdate() can be 135made, but EVP_DigestInit_ex() can be called to initialize a new operation. 136 137=item EVP_MD_CTX_copy_ex() 138 139Can be used to copy the message digest state from B<in> to B<out>. This is 140useful if large amounts of data are to be hashed which only differ in the last 141few bytes. 142 143=item EVP_DigestInit() 144 145Behaves in the same way as EVP_DigestInit_ex() except it always uses the 146default digest implementation and calls EVP_MD_CTX_reset(). 147 148=item EVP_DigestFinal() 149 150Similar to EVP_DigestFinal_ex() except the digest context B<ctx> is 151automatically cleaned up. 152 153=item EVP_MD_CTX_copy() 154 155Similar to EVP_MD_CTX_copy_ex() except the destination B<out> does not have to 156be initialized. 157 158=item EVP_MD_size(), 159EVP_MD_CTX_size() 160 161Return the size of the message digest when passed an B<EVP_MD> or an 162B<EVP_MD_CTX> structure, i.e. the size of the hash. 163 164=item EVP_MD_block_size(), 165EVP_MD_CTX_block_size() 166 167Return the block size of the message digest when passed an B<EVP_MD> or an 168B<EVP_MD_CTX> structure. 169 170=item EVP_MD_type(), 171EVP_MD_CTX_type() 172 173Return the NID of the OBJECT IDENTIFIER representing the given message digest 174when passed an B<EVP_MD> structure. For example, C<EVP_MD_type(EVP_sha1())> 175returns B<NID_sha1>. This function is normally used when setting ASN1 OIDs. 176 177=item EVP_MD_CTX_md_data() 178 179Return the digest method private data for the passed B<EVP_MD_CTX>. 180The space is allocated by OpenSSL and has the size originally set with 181EVP_MD_meth_set_app_datasize(). 182 183=item EVP_MD_CTX_md() 184 185Returns the B<EVP_MD> structure corresponding to the passed B<EVP_MD_CTX>. 186 187=item EVP_MD_CTX_set_update_fn() 188 189Sets the update function for B<ctx> to B<update>. 190This is the function that is called by EVP_DigestUpdate. If not set, the 191update function from the B<EVP_MD> type specified at initialization is used. 192 193=item EVP_MD_CTX_update_fn() 194 195Returns the update function for B<ctx>. 196 197=item EVP_MD_flags() 198 199Returns the B<md> flags. Note that these are different from the B<EVP_MD_CTX> 200ones. See L<EVP_MD_meth_set_flags(3)> for more information. 201 202=item EVP_MD_pkey_type() 203 204Returns the NID of the public key signing algorithm associated with this 205digest. For example EVP_sha1() is associated with RSA so this will return 206B<NID_sha1WithRSAEncryption>. Since digests and signature algorithms are no 207longer linked this function is only retained for compatibility reasons. 208 209=item EVP_md_null() 210 211A "null" message digest that does nothing: i.e. the hash it returns is of zero 212length. 213 214=item EVP_get_digestbyname(), 215EVP_get_digestbynid(), 216EVP_get_digestbyobj() 217 218Returns an B<EVP_MD> structure when passed a digest name, a digest B<NID> or an 219B<ASN1_OBJECT> structure respectively. 220 221=item EVP_MD_CTX_pkey_ctx() 222 223Returns the B<EVP_PKEY_CTX> assigned to B<ctx>. The returned pointer should not 224be freed by the caller. 225 226=item EVP_MD_CTX_set_pkey_ctx() 227 228Assigns an B<EVP_PKEY_CTX> to B<EVP_MD_CTX>. This is usually used to provide 229a customized B<EVP_PKEY_CTX> to L<EVP_DigestSignInit(3)> or 230L<EVP_DigestVerifyInit(3)>. The B<pctx> passed to this function should be freed 231by the caller. A NULL B<pctx> pointer is also allowed to clear the B<EVP_PKEY_CTX> 232assigned to B<ctx>. In such case, freeing the cleared B<EVP_PKEY_CTX> or not 233depends on how the B<EVP_PKEY_CTX> is created. 234 235=back 236 237=head1 CONTROLS 238 239EVP_MD_CTX_ctrl() can be used to send the following standard controls: 240 241=over 4 242 243=item EVP_MD_CTRL_MICALG 244 245Gets the digest Message Integrity Check algorithm string. This is used when 246creating S/MIME multipart/signed messages, as specified in RFC 3851. 247The string value is written to B<p2>. 248 249=item EVP_MD_CTRL_XOF_LEN 250 251This control sets the digest length for extendable output functions to B<p1>. 252Sending this control directly should not be necessary, the use of 253C<EVP_DigestFinalXOF()> is preferred. 254Currently used by SHAKE. 255 256=back 257 258=head1 FLAGS 259 260EVP_MD_CTX_set_flags(), EVP_MD_CTX_clear_flags() and EVP_MD_CTX_test_flags() 261can be used the manipulate and test these B<EVP_MD_CTX> flags: 262 263=over 4 264 265=item EVP_MD_CTX_FLAG_ONESHOT 266 267This flag instructs the digest to optimize for one update only, if possible. 268 269=for comment EVP_MD_CTX_FLAG_CLEANED is internal, don't mention it 270 271=for comment EVP_MD_CTX_FLAG_REUSE is internal, don't mention it 272 273=for comment We currently avoid documenting flags that are only bit holder: 274EVP_MD_CTX_FLAG_NON_FIPS_ALLOW, EVP_MD_CTX_FLAGS_PAD_* 275 276=item EVP_MD_CTX_FLAG_NO_INIT 277 278This flag instructs EVP_DigestInit() and similar not to initialise the 279implementation specific data. 280 281=item EVP_MD_CTX_FLAG_FINALISE 282 283Some functions such as EVP_DigestSign only finalise copies of internal 284contexts so additional data can be included after the finalisation call. 285This is inefficient if this functionality is not required, and can be 286disabled with this flag. 287 288=back 289 290=head1 RETURN VALUES 291 292=over 4 293 294=item EVP_DigestInit_ex(), 295EVP_DigestUpdate(), 296EVP_DigestFinal_ex() 297 298Returns 1 for 299success and 0 for failure. 300 301=item EVP_MD_CTX_ctrl() 302 303Returns 1 if successful or 0 for failure. 304 305=item EVP_MD_CTX_copy_ex() 306 307Returns 1 if successful or 0 for failure. 308 309=item EVP_MD_type(), 310EVP_MD_pkey_type() 311 312Returns the NID of the corresponding OBJECT IDENTIFIER or NID_undef if none 313exists. 314 315=item EVP_MD_size(), 316EVP_MD_block_size(), 317EVP_MD_CTX_size(), 318EVP_MD_CTX_block_size() 319 320Returns the digest or block size in bytes. 321 322=item EVP_md_null() 323 324Returns a pointer to the B<EVP_MD> structure of the "null" message digest. 325 326=item EVP_get_digestbyname(), 327EVP_get_digestbynid(), 328EVP_get_digestbyobj() 329 330Returns either an B<EVP_MD> structure or NULL if an error occurs. 331 332=item EVP_MD_CTX_set_pkey_ctx() 333 334This function has no return value. 335 336=back 337 338=head1 NOTES 339 340The B<EVP> interface to message digests should almost always be used in 341preference to the low-level interfaces. This is because the code then becomes 342transparent to the digest used and much more flexible. 343 344New applications should use the SHA-2 (such as L<EVP_sha256(3)>) or the SHA-3 345digest algorithms (such as L<EVP_sha3_512(3)>). The other digest algorithms 346are still in common use. 347 348For most applications the B<impl> parameter to EVP_DigestInit_ex() will be 349set to NULL to use the default digest implementation. 350 351The functions EVP_DigestInit(), EVP_DigestFinal() and EVP_MD_CTX_copy() are 352obsolete but are retained to maintain compatibility with existing code. New 353applications should use EVP_DigestInit_ex(), EVP_DigestFinal_ex() and 354EVP_MD_CTX_copy_ex() because they can efficiently reuse a digest context 355instead of initializing and cleaning it up on each call and allow non default 356implementations of digests to be specified. 357 358If digest contexts are not cleaned up after use, 359memory leaks will occur. 360 361EVP_MD_CTX_size(), EVP_MD_CTX_block_size(), EVP_MD_CTX_type(), 362EVP_get_digestbynid() and EVP_get_digestbyobj() are defined as 363macros. 364 365EVP_MD_CTX_ctrl() sends commands to message digests for additional configuration 366or control. 367 368=head1 EXAMPLES 369 370This example digests the data "Test Message\n" and "Hello World\n", using the 371digest name passed on the command line. 372 373 #include <stdio.h> 374 #include <string.h> 375 #include <openssl/evp.h> 376 377 int main(int argc, char *argv[]) 378 { 379 EVP_MD_CTX *mdctx; 380 const EVP_MD *md; 381 char mess1[] = "Test Message\n"; 382 char mess2[] = "Hello World\n"; 383 unsigned char md_value[EVP_MAX_MD_SIZE]; 384 unsigned int md_len, i; 385 386 if (argv[1] == NULL) { 387 printf("Usage: mdtest digestname\n"); 388 exit(1); 389 } 390 391 md = EVP_get_digestbyname(argv[1]); 392 if (md == NULL) { 393 printf("Unknown message digest %s\n", argv[1]); 394 exit(1); 395 } 396 397 mdctx = EVP_MD_CTX_new(); 398 EVP_DigestInit_ex(mdctx, md, NULL); 399 EVP_DigestUpdate(mdctx, mess1, strlen(mess1)); 400 EVP_DigestUpdate(mdctx, mess2, strlen(mess2)); 401 EVP_DigestFinal_ex(mdctx, md_value, &md_len); 402 EVP_MD_CTX_free(mdctx); 403 404 printf("Digest is: "); 405 for (i = 0; i < md_len; i++) 406 printf("%02x", md_value[i]); 407 printf("\n"); 408 409 exit(0); 410 } 411 412=head1 SEE ALSO 413 414L<EVP_MD_meth_new(3)>, 415L<dgst(1)>, 416L<evp(7)> 417 418The full list of digest algorithms are provided below. 419 420L<EVP_blake2b512(3)>, 421L<EVP_md2(3)>, 422L<EVP_md4(3)>, 423L<EVP_md5(3)>, 424L<EVP_mdc2(3)>, 425L<EVP_ripemd160(3)>, 426L<EVP_sha1(3)>, 427L<EVP_sha224(3)>, 428L<EVP_sha3_224(3)>, 429L<EVP_sm3(3)>, 430L<EVP_whirlpool(3)> 431 432=head1 HISTORY 433 434The EVP_MD_CTX_create() and EVP_MD_CTX_destroy() functions were renamed to 435EVP_MD_CTX_new() and EVP_MD_CTX_free() in OpenSSL 1.1.0, respectively. 436 437The link between digests and signing algorithms was fixed in OpenSSL 1.0 and 438later, so now EVP_sha1() can be used with RSA and DSA. 439 440The EVP_dss1() function was removed in OpenSSL 1.1.0. 441 442The EVP_MD_CTX_set_pkey_ctx() function was added in 1.1.1. 443 444=head1 COPYRIGHT 445 446Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved. 447 448Licensed under the OpenSSL license (the "License"). You may not use 449this file except in compliance with the License. You can obtain a copy 450in the file LICENSE in the source distribution or at 451L<https://www.openssl.org/source/license.html>. 452 453=cut 454