1=pod
2
3=head1 NAME
4
5provider-digest - The digest library E<lt>-E<gt> provider functions
6
7=head1 SYNOPSIS
8
9=for openssl multiple includes
10
11 #include <openssl/core_dispatch.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 *OSSL_FUNC_digest_newctx(void *provctx);
21 void OSSL_FUNC_digest_freectx(void *dctx);
22 void *OSSL_FUNC_digest_dupctx(void *dctx);
23
24 /* Digest generation */
25 int OSSL_FUNC_digest_init(void *dctx, const OSSL_PARAM params[]);
26 int OSSL_FUNC_digest_update(void *dctx, const unsigned char *in, size_t inl);
27 int OSSL_FUNC_digest_final(void *dctx, unsigned char *out, size_t *outl,
28                            size_t outsz);
29 int OSSL_FUNC_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 *OSSL_FUNC_digest_gettable_params(void *provctx);
34
35 /* Digest operation parameter descriptors */
36 const OSSL_PARAM *OSSL_FUNC_digest_gettable_ctx_params(void *dctx,
37                                                        void *provctx);
38 const OSSL_PARAM *OSSL_FUNC_digest_settable_ctx_params(void *dctx,
39                                                        void *provctx);
40
41 /* Digest parameters */
42 int OSSL_FUNC_digest_get_params(OSSL_PARAM params[]);
43
44 /* Digest operation parameters */
45 int OSSL_FUNC_digest_set_ctx_params(void *dctx, const OSSL_PARAM params[]);
46 int OSSL_FUNC_digest_get_ctx_params(void *dctx, OSSL_PARAM params[]);
47
48=head1 DESCRIPTION
49
50This documentation is primarily aimed at provider authors. See L<provider(7)>
51for further information.
52
53The DIGEST operation enables providers to implement digest algorithms and make
54them available to applications via the API functions L<EVP_DigestInit_ex(3)>,
55L<EVP_DigestUpdate(3)> and L<EVP_DigestFinal(3)> (and other related functions).
56
57All "functions" mentioned here are passed as function pointers between
58F<libcrypto> and the provider in L<OSSL_DISPATCH(3)> arrays via
59L<OSSL_ALGORITHM(3)> arrays that are returned by the provider's
60provider_query_operation() function
61(see L<provider-base(7)/Provider Functions>).
62
63All these "functions" have a corresponding function type definition
64named B<OSSL_FUNC_{name}_fn>, and a helper function to retrieve the
65function pointer from an L<OSSL_DISPATCH(3)> element named
66B<OSSL_FUNC_{name}>.
67For example, the "function" OSSL_FUNC_digest_newctx() has these:
68
69 typedef void *(OSSL_FUNC_digest_newctx_fn)(void *provctx);
70 static ossl_inline OSSL_FUNC_digest_newctx_fn
71     OSSL_FUNC_digest_newctx(const OSSL_DISPATCH *opf);
72
73L<OSSL_DISPATCH(3)> arrays are indexed by numbers that are provided as
74macros in L<openssl-core_dispatch.h(7)>, as follows:
75
76 OSSL_FUNC_digest_newctx               OSSL_FUNC_DIGEST_NEWCTX
77 OSSL_FUNC_digest_freectx              OSSL_FUNC_DIGEST_FREECTX
78 OSSL_FUNC_digest_dupctx               OSSL_FUNC_DIGEST_DUPCTX
79
80 OSSL_FUNC_digest_init                 OSSL_FUNC_DIGEST_INIT
81 OSSL_FUNC_digest_update               OSSL_FUNC_DIGEST_UPDATE
82 OSSL_FUNC_digest_final                OSSL_FUNC_DIGEST_FINAL
83 OSSL_FUNC_digest_digest               OSSL_FUNC_DIGEST_DIGEST
84
85 OSSL_FUNC_digest_get_params           OSSL_FUNC_DIGEST_GET_PARAMS
86 OSSL_FUNC_digest_get_ctx_params       OSSL_FUNC_DIGEST_GET_CTX_PARAMS
87 OSSL_FUNC_digest_set_ctx_params       OSSL_FUNC_DIGEST_SET_CTX_PARAMS
88
89 OSSL_FUNC_digest_gettable_params      OSSL_FUNC_DIGEST_GETTABLE_PARAMS
90 OSSL_FUNC_digest_gettable_ctx_params  OSSL_FUNC_DIGEST_GETTABLE_CTX_PARAMS
91 OSSL_FUNC_digest_settable_ctx_params  OSSL_FUNC_DIGEST_SETTABLE_CTX_PARAMS
92
93A digest algorithm implementation may not implement all of these functions.
94In order to be usable all or none of OSSL_FUNC_digest_newctx, OSSL_FUNC_digest_freectx,
95OSSL_FUNC_digest_init, OSSL_FUNC_digest_update and OSSL_FUNC_digest_final should be implemented.
96All other functions are optional.
97
98=head2 Context Management Functions
99
100OSSL_FUNC_digest_newctx() should create and return a pointer to a provider side
101structure for holding context information during a digest operation.
102A pointer to this context will be passed back in a number of the other digest
103operation function calls.
104The parameter I<provctx> is the provider context generated during provider
105initialisation (see L<provider(7)>).
106
107OSSL_FUNC_digest_freectx() is passed a pointer to the provider side digest context in
108the I<dctx> parameter.
109This function should free any resources associated with that context.
110
111OSSL_FUNC_digest_dupctx() should duplicate the provider side digest context in the
112I<dctx> parameter and return the duplicate copy.
113
114=head2 Digest Generation Functions
115
116OSSL_FUNC_digest_init() initialises a digest operation given a newly created
117provider side digest context in the I<dctx> parameter.
118The I<params>, if not NULL, should be set on the context in a manner similar to
119using OSSL_FUNC_digest_set_ctx_params().
120
121OSSL_FUNC_digest_update() is called to supply data to be digested as part of a
122previously initialised digest operation.
123The I<dctx> parameter contains a pointer to a previously initialised provider
124side context.
125OSSL_FUNC_digest_update() should digest I<inl> bytes of data at the location pointed to
126by I<in>.
127OSSL_FUNC_digest_update() may be called multiple times for a single digest operation.
128
129OSSL_FUNC_digest_final() generates a digest started through previous OSSL_FUNC_digest_init()
130and OSSL_FUNC_digest_update() calls.
131The I<dctx> parameter contains a pointer to the provider side context.
132The digest should be written to I<*out> and the length of the digest to
133I<*outl>.
134The digest should not exceed I<outsz> bytes.
135
136OSSL_FUNC_digest_digest() is a "oneshot" digest function.
137No provider side digest context is used.
138Instead the provider context that was created during provider initialisation is
139passed in the I<provctx> parameter (see L<provider(7)>).
140I<inl> bytes at I<in> should be digested and the result should be stored at
141I<out>. The length of the digest should be stored in I<*outl> which should not
142exceed I<outsz> bytes.
143
144=head2 Digest Parameters
145
146See L<OSSL_PARAM(3)> for further details on the parameters structure used by
147these functions.
148
149OSSL_FUNC_digest_get_params() gets details of the algorithm implementation
150and stores them in I<params>.
151
152OSSL_FUNC_digest_set_ctx_params() sets digest operation parameters for the
153provider side digest context I<dctx> to I<params>.
154Any parameter settings are additional to any that were previously set.
155Passing NULL for I<params> should return true.
156
157OSSL_FUNC_digest_get_ctx_params() gets digest operation details details from
158the given provider side digest context I<dctx> and stores them in I<params>.
159Passing NULL for I<params> should return true.
160
161OSSL_FUNC_digest_gettable_params() returns a constant L<OSSL_PARAM(3)> array
162containing descriptors of the parameters that OSSL_FUNC_digest_get_params()
163can handle.
164
165OSSL_FUNC_digest_gettable_ctx_params() and
166OSSL_FUNC_digest_settable_ctx_params() both return constant
167L<OSSL_PARAM(3)> arrays as descriptors of the parameters that
168OSSL_FUNC_digest_get_ctx_params() and OSSL_FUNC_digest_set_ctx_params()
169can handle, respectively.  The array is based on the current state of
170the provider side context if I<dctx> is not NULL and on the provider
171side algorithm I<provctx> otherwise.
172
173Parameters currently recognised by built-in digests with this function
174are as follows. Not all parameters are relevant to, or are understood
175by all digests:
176
177=over 4
178
179=item "blocksize" (B<OSSL_DIGEST_PARAM_BLOCK_SIZE>) <unsigned integer>
180
181The digest block size.
182The length of the "blocksize" parameter should not exceed that of a B<size_t>.
183
184=item "size" (B<OSSL_DIGEST_PARAM_SIZE>) <unsigned integer>
185
186The digest output size.
187The length of the "size" parameter should not exceed that of a B<size_t>.
188
189=item "flags" (B<OSSL_DIGEST_PARAM_FLAGS>) <unsigned integer>
190
191Diverse flags that describe exceptional behaviour for the digest:
192
193=over 4
194
195=item B<EVP_MD_FLAG_ONESHOT>
196
197This digest method can only handle one block of input.
198
199=item B<EVP_MD_FLAG_XOF>
200
201This digest method is an extensible-output function (XOF) and supports
202setting the B<OSSL_DIGEST_PARAM_XOFLEN> parameter.
203
204=item B<EVP_MD_FLAG_DIGALGID_NULL>
205
206When setting up a DigestAlgorithmIdentifier, this flag will have the
207parameter set to NULL by default.  Use this for PKCS#1.  I<Note: if
208combined with EVP_MD_FLAG_DIGALGID_ABSENT, the latter will override.>
209
210=item B<EVP_MD_FLAG_DIGALGID_ABSENT>
211
212When setting up a DigestAlgorithmIdentifier, this flag will have the
213parameter be left absent by default.  I<Note: if combined with
214EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
215
216=item B<EVP_MD_FLAG_DIGALGID_CUSTOM>
217
218Custom DigestAlgorithmIdentifier handling via ctrl, with
219B<EVP_MD_FLAG_DIGALGID_ABSENT> as default.  I<Note: if combined with
220EVP_MD_FLAG_DIGALGID_NULL, the latter will be overridden.>
221Currently unused.
222
223=back
224
225The length of the "flags" parameter should equal that of an
226B<unsigned long int>.
227
228=back
229
230=head2 Digest Context Parameters
231
232OSSL_FUNC_digest_set_ctx_params() sets digest parameters associated with the
233given provider side digest context I<dctx> to I<params>.
234Any parameter settings are additional to any that were previously set.
235See L<OSSL_PARAM(3)> for further details on the parameters structure.
236
237OSSL_FUNC_digest_get_ctx_params() gets details of currently set parameters
238values associated with the give provider side digest context I<dctx>
239and stores them in I<params>.
240See L<OSSL_PARAM(3)> for further details on the parameters structure.
241
242=head1 RETURN VALUES
243
244OSSL_FUNC_digest_newctx() and OSSL_FUNC_digest_dupctx() should return the newly created
245provider side digest context, or NULL on failure.
246
247OSSL_FUNC_digest_init(), OSSL_FUNC_digest_update(), OSSL_FUNC_digest_final(), OSSL_FUNC_digest_digest(),
248OSSL_FUNC_digest_set_params() and OSSL_FUNC_digest_get_params() should return 1 for success or
2490 on error.
250
251OSSL_FUNC_digest_size() should return the digest size.
252
253OSSL_FUNC_digest_block_size() should return the block size of the underlying digest
254algorithm.
255
256=head1 BUGS
257
258The EVP_Q_digest(), EVP_Digest() and EVP_DigestFinal_ex() API calls do not
259expect the digest size to be larger than EVP_MAX_MD_SIZE. Any algorithm which
260produces larger digests is unusable with those API calls.
261
262=head1 SEE ALSO
263
264L<provider(7)>, L<OSSL_PROVIDER-FIPS(7)>, L<OSSL_PROVIDER-default(7)>,
265L<OSSL_PROVIDER-legacy(7)>,
266L<EVP_MD-common(7)>, L<EVP_MD-BLAKE2(7)>, L<EVP_MD-MD2(7)>,
267L<EVP_MD-MD4(7)>, L<EVP_MD-MD5(7)>, L<EVP_MD-MD5-SHA1(7)>,
268L<EVP_MD-MDC2(7)>, L<EVP_MD-RIPEMD160(7)>, L<EVP_MD-SHA1(7)>,
269L<EVP_MD-SHA2(7)>, L<EVP_MD-SHA3(7)>, L<EVP_MD-SHAKE(7)>,
270L<EVP_MD-SM3(7)>, L<EVP_MD-WHIRLPOOL(7)>,
271L<EVP_MD-NULL(7)>,
272L<life_cycle-digest(7)>, L<EVP_DigestInit(3)>
273
274=head1 HISTORY
275
276The provider DIGEST interface was introduced in OpenSSL 3.0.
277
278=head1 COPYRIGHT
279
280Copyright 2019-2023 The OpenSSL Project Authors. All Rights Reserved.
281
282Licensed under the Apache License 2.0 (the "License").  You may not use
283this file except in compliance with the License.  You can obtain a copy
284in the file LICENSE in the source distribution or at
285L<https://www.openssl.org/source/license.html>.
286
287=cut
288