doc/man7/provider-digest.pod

   1 =pod
   2
   3 =head1 NAME
   4
   5 provider-digest - The digest library E<lt>-E<gt> provider functions
   6
   7 =head1 SYNOPSIS
   8
   9 =for comment multiple includes
  10
  11  #include <openssl/core_numbers.h>
  12  #include <openssl/core_names.h>
  13
  14  /*
  15   * Digests support the following function signatures in OSSL_DISPATCH arrays.
  16   * (The function signatures are not actual functions).
  17   */
  18
  19  /* Context management */
  20  void *OP_digest_newctx(void *provctx);
  21  void OP_digest_freectx(void *dctx);
  22  void *OP_digest_dupctx(void *dctx);
  23
  24  /* Digest generation */
  25  int OP_digest_init(void *dctx);
  26  int OP_digest_update(void *dctx, const unsigned char *in, size_t inl);
  27  int OP_digest_final(void *dctx, unsigned char *out, size_t *outl,
  28                      size_t outsz);
  29  int OP_digest_digest(void *provctx, const unsigned char *in, size_t inl,
  30                       unsigned char *out, size_t *outl, size_t outsz);
  31
  32  /* Digest parameter descriptors */
  33  const OSSL_PARAM *OP_cipher_gettable_params(void);
  34
  35  /* Digest operation parameter descriptors */
  36  const OSSL_PARAM *OP_cipher_gettable_ctx_params(void);
  37  const OSSL_PARAM *OP_cipher_settable_ctx_params(void);
  38
  39  /* Digest parameters */
  40  int OP_digest_get_params(OSSL_PARAM params[]);
  41
  42  /* Digest operation parameters */
  43  int OP_digest_set_ctx_params(void *dctx, const OSSL_PARAM params[]);
  44  int OP_digest_get_ctx_params(void *dctx, OSSL_PARAM params[]);
  45
  46 =head1 DESCRIPTION
  47
  48 This documentation is primarily aimed at provider authors. See L<provider(7)>
  49 for further information.
  50
  51 The DIGEST operation enables providers to implement digest algorithms and make
  52 them available to applications via the API functions L<EVP_DigestInit_ex(3)>,
  53 L<EVP_DigestUpdate(3)> and L<EVP_DigestFinal(3)> (and other related functions).
  54
  55 All "functions" mentioned here are passed as function pointers between
  56 F<libcrypto> and the provider in B<OSSL_DISPATCH> arrays via
  57 B<OSSL_ALGORITHM> arrays that are returned by the provider's
  58 provider_query_operation() function
  59 (see L<provider-base(7)/Provider Functions>).
  60
  61 All these "functions" have a corresponding function type definition
  62 named B<OSSL_{name}_fn>, and a helper function to retrieve the
  63 function pointer from an B<OSSL_DISPATCH> element named
  64 B<OSSL_get_{name}>.
  65 For example, the "function" OP_digest_newctx() has these:
  66
  67  typedef void *(OSSL_OP_digest_newctx_fn)(void *provctx);
  68  static ossl_inline OSSL_OP_digest_newctx_fn
  69      OSSL_get_OP_digest_newctx(const OSSL_DISPATCH *opf);
  70
  71 B<OSSL_DISPATCH> arrays are indexed by numbers that are provided as
  72 macros in L<openssl-core_numbers.h(7)>, as follows:
  73
  74  OP_digest_newctx               OSSL_FUNC_DIGEST_NEWCTX
  75  OP_digest_freectx              OSSL_FUNC_DIGEST_FREECTX
  76  OP_digest_dupctx               OSSL_FUNC_DIGEST_DUPCTX
  77
  78  OP_digest_init                 OSSL_FUNC_DIGEST_INIT
  79  OP_digest_update               OSSL_FUNC_DIGEST_UPDATE
  80  OP_digest_final                OSSL_FUNC_DIGEST_FINAL
  81  OP_digest_digest               OSSL_FUNC_DIGEST_DIGEST
  82
  83  OP_digest_get_params           OSSL_FUNC_DIGEST_GET_PARAMS
  84  OP_digest_get_ctx_params       OSSL_FUNC_DIGEST_GET_CTX_PARAMS
  85  OP_digest_set_ctx_params       OSSL_FUNC_DIGEST_SET_CTX_PARAMS
  86
  87  OP_digest_gettable_params      OSSL_FUNC_DIGEST_GETTABLE_PARAMS
  88  OP_digest_gettable_ctx_params  OSSL_FUNC_DIGEST_GETTABLE_CTX_PARAMS
  89  OP_digest_settable_ctx_params  OSSL_FUNC_DIGEST_SETTABLE_CTX_PARAMS
  90
  91 A digest algorithm implementation may not implement all of these functions.
  92 In order to be usable all or none of OP_digest_newctx, OP_digest_freectx,
  93 OP_digest_init, OP_digest_update and OP_digest_final should be implemented.
  94 All other functions are optional.
  95
  96 =head2 Context Management Functions
  97
  98 OP_digest_newctx() should create and return a pointer to a provider side
  99 structure for holding context information during a digest operation.
 100 A pointer to this context will be passed back in a number of the other digest
 101 operation function calls.
 102 The parameter B<provctx> is the provider context generated during provider
 103 initialisation (see L<provider(3)>).
 104
 105 OP_digest_freectx() is passed a pointer to the provider side digest context in
 106 the B<dctx> parameter.
 107 This function should free any resources associated with that context.
 108
 109 OP_digest_dupctx() should duplicate the provider side digest context in the
 110 B<dctx> parameter and return the duplicate copy.
 111
 112 =head2 Digest Generation Functions
 113
 114 OP_digest_init() initialises a digest operation given a newly created
 115 provider side digest context in the B<dctx> parameter.
 116
 117 OP_digest_update() is called to supply data to be digested as part of a
 118 previously initialised digest operation.
 119 The B<dctx> parameter contains a pointer to a previously initialised provider
 120 side context.
 121 OP_digest_update() should digest B<inl> bytes of data at the location pointed to
 122 by B<in>.
 123 OP_digest_update() may be called multiple times for a single digest operation.
 124
 125 OP_digest_final() generates a digest started through previous OP_digest_init()
 126 and OP_digest_update() calls.
 127 The B<dctx> parameter contains a pointer to the provider side context.
 128 The digest should be written to B<*out> and the length of the digest to
 129 B<*outl>.
 130 The digest should not exceed B<outsz> bytes.
 131
 132 OP_digest_digest() is a "oneshot" digest function.
 133 No provider side digest context is used.
 134 Instead the provider context that was created during provider initialisation is
 135 passed in the B<provctx> parameter (see L<provider(3)>).
 136 B<inl> bytes at B<in> should be digested and the result should be stored at
 137 B<out>. The length of the digest should be stored in B<*outl> which should not
 138 exceed B<outsz> bytes.
 139
 140 =head2 Digest Parameters
 141
 142 See L<OSSL_PARAM(3)> for further details on the parameters structure used by
 143 these functions.
 144
 145 OP_digest_get_params() gets details of the algorithm implementation
 146 and stores them in B<params>.
 147
 148 OP_digest_set_ctx_params() sets digest operation parameters for the
 149 provider side digest context B<dctx> to B<params>.
 150 Any parameter settings are additional to any that were previously set.
 151
 152 OP_digest_get_ctx_params() gets digest operation details details from
 153 the given provider side digest context B<dctx> and stores them in B<params>.
 154
 155 OP_digest_gettable_params(), OP_digest_gettable_ctx_params(), and
 156 OP_digest_settable_ctx_params() all return constant B<OSSL_PARAM> arrays
 157 as descriptors of the parameters that OP_digest_get_params(),
 158 OP_digest_get_ctx_params(), and OP_digest_set_ctx_params() can handle,
 159 respectively.
 160
 161 Parameters currently recognised by built-in digests with this function
 162 are as follows. Not all parameters are relevant to, or are understood
 163 by all digests:
 164
 165 =over 4
 166
 167 =item B<OSSL_DIGEST_PARAM_BLOCK_SIZE> (size_t)
 168
 169 The digest block size.
 170
 171 =item B<OSSL_DIGEST_PARAM_SIZE> (size_t)
 172
 173 The digest output size.
 174
 175 =item B<OSSL_DIGEST_PARAM_FLAGS> (unsigned long)
 176
 177 Diverse flags that describe exceptional behaviour for the digest:
 178
 179 =over 4
 180
 181 =item B<EVP_MD_FLAG_ONESHOT>
 182
 183 This digest method can only handle one block of input.
 184
 185 =item B<EVP_MD_FLAG_XOF>
 186
 187 This digest method is an extensible-output function (XOF) and supports
 188 setting the B<OSSL_DIGEST_PARAM_XOFLEN> parameter.
 189
 190 =item B<EVP_MD_FLAG_DIGALGID_NULL>
 191
 192 When setting up a DigestAlgorithmIdentifier, this flag will have the
 193 parameter set to NULL by default.  Use this for PKCS#1.  I<Note: if
 194 combined with EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.>
 195
 196 =item B<EVP_MD_FLAG_DIGALGID_ABSENT>
 197
 198 When setting up a DigestAlgorithmIdentifier, this flag will have the
 199 parameter be left absent by default.  I<Note: if combined with
 200 EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
 201
 202 =item B<EVP_MD_FLAG_DIGALGID_CUSTOM>
 203
 204 Custom DigestAlgorithmIdentifier handling via ctrl, with
 205 B<EVP_MD_FLAG_DIGALGID_ABSENT> as default.  I<Note: if combined with
 206 EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
 207 Currently unused.
 208
 209 =back
 210
 211 =back
 212
 213 =head2 Digest Context Parameters
 214
 215 OP_digest_set_ctx_params() sets digest parameters associated with the
 216 given provider side digest context B<dctx> to B<params>.
 217 Any parameter settings are additional to any that were previously set.
 218 See L<OSSL_PARAM(3)> for further details on the parameters structure.
 219
 220 OP_digest_get_ctx_params() gets details of currently set parameters
 221 values associated with the give provider side digest context B<dctx>
 222 and stores them in B<params>.
 223 See L<OSSL_PARAM(3)> for further details on the parameters structure.
 224
 225 Parameters currently recognised by built-in digests are as follows. Not all
 226 parameters are relevant to, or are understood by all digests:
 227
 228 =over 4
 229
 230 =item B<OSSL_DIGEST_PARAM_XOFLEN> (unsigned integer)
 231
 232 Sets the digest length for extendable output functions.
 233 The length of the "xoflen" parameter should not exceed that of a B<size_t>.
 234
 235 =item B<OSSL_DIGEST_PARAM_SSL3_MS> (octet string)
 236
 237 This parameter is set by libssl in order to calculate a signature hash for an
 238 SSLv3 CertificateVerify message as per RFC6101.
 239 It is only set after all handshake messages have already been digested via
 240 OP_digest_update() calls.
 241 The parameter provides the master secret value to be added to the digest.
 242 The digest implementation should calculate the complete digest as per RFC6101
 243 section 5.6.8.
 244 The next call after setting this parameter will be OP_digest_final().
 245 This is only relevant for implementations of SHA1 or MD5_SHA1.
 246
 247 =item B<OSSL_DIGEST_PARAM_PAD_TYPE> (unsigned integer)
 248
 249 Sets the pad type to be used.
 250 The only built-in digest that uses this is MDC2.
 251 Normally the final MDC2 block is padded with 0s.
 252 If the pad type is set to 2 then the final block is padded with 0x80 followed by
 253 0s.
 254
 255 =item B<OSSL_DIGEST_PARAM_MICALG> (UTF8 string)
 256
 257 Gets the digest Message Integrity Check algorithm string.
 258 This is used when creating S/MIME multipart/signed messages, as specified in
 259 RFC 5751.
 260
 261 =back
 262
 263 =head1 RETURN VALUES
 264
 265 OP_digest_newctx() and OP_digest_dupctx() should return the newly created
 266 provider side digest context, or NULL on failure.
 267
 268 OP_digest_init(), OP_digest_update(), OP_digest_final(), OP_digest_digest(),
 269 OP_digest_set_params() and OP_digest_get_params() should return 1 for success or
 270 0 on error.
 271
 272 OP_digest_size() should return the digest size.
 273
 274 OP_digest_block_size() should return the block size of the underlying digest
 275 algorithm.
 276
 277 =head1 SEE ALSO
 278
 279 L<provider(7)>
 280
 281 =head1 HISTORY
 282
 283 The provider DIGEST interface was introduced in OpenSSL 3.0.
 284
 285 =head1 COPYRIGHT
 286
 287 Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
 288
 289 Licensed under the Apache License 2.0 (the "License").  You may not use
 290 this file except in compliance with the License.  You can obtain a copy
 291 in the file LICENSE in the source distribution or at
 292 L<https://www.openssl.org/source/license.html>.
 293
 294 =cut