xref: /openssl/doc/man7/provider-rand.pod (revision 632bc4df) 
1=pod
2
3=head1 NAME
4
5provider-rand - The random number generation library E<lt>-E<gt> provider
6functions
7
8=head1 SYNOPSIS
9
10=for openssl multiple includes
11
12 #include <openssl/core_dispatch.h>
13 #include <openssl/core_names.h>
14
15 /*
16  * None of these are actual functions, but are displayed like this for
17  * the function signatures for functions that are offered as function
18  * pointers in OSSL_DISPATCH arrays.
19  */
20
21 /* Context management */
22 void *OSSL_FUNC_rand_newctx(void *provctx, void *parent,
23                             const OSSL_DISPATCH *parent_calls);
24 void OSSL_FUNC_rand_freectx(void *ctx);
25
26 /* Random number generator functions: NIST */
27 int OSSL_FUNC_rand_instantiate(void *ctx, unsigned int strength,
28                                int prediction_resistance,
29                                const unsigned char *pstr, size_t pstr_len,
30                                const OSSL_PARAM params[]);
31 int OSSL_FUNC_rand_uninstantiate(void *ctx);
32 int OSSL_FUNC_rand_generate(void *ctx, unsigned char *out, size_t outlen,
33                             unsigned int strength, int prediction_resistance,
34                             const unsigned char *addin, size_t addin_len);
35 int OSSL_FUNC_rand_reseed(void *ctx, int prediction_resistance,
36                           const unsigned char *ent, size_t ent_len,
37                           const unsigned char *addin, size_t addin_len);
38
39 /* Random number generator functions: additional */
40 size_t OSSL_FUNC_rand_nonce(void *ctx, unsigned char *out, size_t outlen,
41                             int strength, size_t min_noncelen,
42                             size_t max_noncelen);
43 size_t OSSL_FUNC_rand_get_seed(void *ctx, unsigned char **buffer,
44                                int entropy, size_t min_len, size_t max_len,
45                                int prediction_resistance,
46                                const unsigned char *adin, size_t adin_len);
47 void OSSL_FUNC_rand_clear_seed(void *ctx, unsigned char *buffer, size_t b_len);
48 int OSSL_FUNC_rand_verify_zeroization(void *ctx);
49
50 /* Context Locking */
51 int OSSL_FUNC_rand_enable_locking(void *ctx);
52 int OSSL_FUNC_rand_lock(void *ctx);
53 void OSSL_FUNC_rand_unlock(void *ctx);
54
55 /* RAND parameter descriptors */
56 const OSSL_PARAM *OSSL_FUNC_rand_gettable_params(void *provctx);
57 const OSSL_PARAM *OSSL_FUNC_rand_gettable_ctx_params(void *ctx, void *provctx);
58 const OSSL_PARAM *OSSL_FUNC_rand_settable_ctx_params(void *ctx, void *provctx);
59
60 /* RAND parameters */
61 int OSSL_FUNC_rand_get_params(OSSL_PARAM params[]);
62 int OSSL_FUNC_rand_get_ctx_params(void *ctx, OSSL_PARAM params[]);
63 int OSSL_FUNC_rand_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
64
65=head1 DESCRIPTION
66
67This documentation is primarily aimed at provider authors. See L<provider(7)>
68for further information.
69
70The RAND operation enables providers to implement random number generation
71algorithms and random number sources and make
72them available to applications via the API function L<EVP_RAND(3)>.
73
74=head2 Context Management Functions
75
76OSSL_FUNC_rand_newctx() should create and return a pointer to a provider side
77structure for holding context information during a rand operation.
78A pointer to this context will be passed back in a number of the other rand
79operation function calls.
80The parameter I<provctx> is the provider context generated during provider
81initialisation (see L<provider(7)>).
82The parameter I<parent> specifies another rand instance to be used for
83seeding purposes.  If NULL and the specific instance supports it, the
84operating system will be used for seeding.
85The parameter I<parent_calls> points to the dispatch table for I<parent>.
86Thus, the parent need not be from the same provider as the new instance.
87
88OSSL_FUNC_rand_freectx() is passed a pointer to the provider side rand context in
89the I<mctx> parameter.
90If it receives NULL as I<ctx> value, it should not do anything other than
91return.
92This function should free any resources associated with that context.
93
94=head2 Random Number Generator Functions: NIST
95
96These functions correspond to those defined in NIST SP 800-90A and SP 800-90C.
97
98OSSL_FUNC_rand_instantiate() is used to instantiate the DRBG I<ctx> at a requested
99security I<strength>.  In addition, I<prediction_resistance> can be requested.
100Additional input I<addin> of length I<addin_len> bytes can optionally
101be provided.  The parameters specified in I<params> configure the DRBG and these
102should be processed before instantiation.
103
104OSSL_FUNC_rand_uninstantiate() is used to uninstantiate the DRBG I<ctx>.  After being
105uninstantiated, a DRBG is unable to produce output until it is instantiated
106anew.
107
108OSSL_FUNC_rand_generate() is used to generate random bytes from the DRBG I<ctx>.
109It will generate I<outlen> bytes placing them into the buffer pointed to by
110I<out>.  The generated bytes will meet the specified security I<strength> and,
111if I<prediction_resistance> is true, the bytes will be produced after reseeding
112from a live entropy source.  Additional input I<addin> of length I<addin_len>
113bytes can optionally be provided.
114
115=head2 Random Number Generator Functions: Additional
116
117OSSL_FUNC_rand_nonce() is used to generate a nonce of the given I<strength> with a
118length from I<min_noncelen> to I<max_noncelen>. If the output buffer I<out> is
119NULL, the length of the nonce should be returned.
120
121OSSL_FUNC_rand_get_seed() is used by deterministic generators to obtain their
122seeding material from their parent.  The seed bytes will meet the specified
123security level of I<entropy> bits and there will be between I<min_len>
124and I<max_len> inclusive bytes in total.  If I<prediction_resistance> is
125true, the bytes will be produced from a live entropy source.  Additional
126input I<addin> of length I<addin_len> bytes can optionally be provided.
127A pointer to the seed material is returned in I<*buffer> and this must be
128freed by a later call to OSSL_FUNC_rand_clear_seed().
129
130OSSL_FUNC_rand_clear_seed() frees a seed I<buffer> of length I<b_len> bytes
131which was previously allocated by OSSL_FUNC_rand_get_seed().
132
133OSSL_FUNC_rand_verify_zeroization() is used to determine if the internal state of the
134DRBG is zero.  This capability is mandated by NIST as part of the self
135tests, it is unlikely to be useful in other circumstances.
136
137=head2 Context Locking
138
139When DRBGs are used by multiple threads, there must be locking employed to
140ensure their proper operation.  Because locking introduces an overhead, it
141is disabled by default.
142
143OSSL_FUNC_rand_enable_locking() allows locking to be turned on for a DRBG and all of
144its parent DRBGs.  From this call onwards, the DRBG can be used in a thread
145safe manner.
146
147OSSL_FUNC_rand_lock() is used to lock a DRBG.  Once locked, exclusive access
148is guaranteed.
149
150OSSL_FUNC_rand_unlock() is used to unlock a DRBG.
151
152=head2 Rand Parameters
153
154See L<OSSL_PARAM(3)> for further details on the parameters structure used by
155these functions.
156
157OSSL_FUNC_rand_get_params() gets details of parameter values associated with the
158provider algorithm and stores them in I<params>.
159
160OSSL_FUNC_rand_set_ctx_params() sets rand parameters associated with the given
161provider side rand context I<ctx> to I<params>.
162Any parameter settings are additional to any that were previously set.
163Passing NULL for I<params> should return true.
164
165OSSL_FUNC_rand_get_ctx_params() gets details of currently set parameter values
166associated with the given provider side rand context I<ctx> and stores them
167in I<params>.
168Passing NULL for I<params> should return true.
169
170OSSL_FUNC_rand_gettable_params(), OSSL_FUNC_rand_gettable_ctx_params(),
171and OSSL_FUNC_rand_settable_ctx_params() all return constant B<OSSL_PARAM>
172arrays as descriptors of the parameters that OSSL_FUNC_rand_get_params(),
173OSSL_FUNC_rand_get_ctx_params(), and OSSL_FUNC_rand_set_ctx_params()
174can handle, respectively.  OSSL_FUNC_rand_gettable_ctx_params()
175and OSSL_FUNC_rand_settable_ctx_params() will return the parameters
176associated with the provider side context I<ctx> in its current state
177if it is not NULL.  Otherwise, they return the parameters associated
178with the provider side algorithm I<provctx>.
179
180
181Parameters currently recognised by built-in rands are as follows. Not all
182parameters are relevant to, or are understood by all rands:
183
184=over 4
185
186=item "state" (B<OSSL_RAND_PARAM_STATE>) <integer>
187
188Returns the state of the random number generator.
189
190=item "strength" (B<OSSL_RAND_PARAM_STRENGTH>) <unsigned integer>
191
192Returns the bit strength of the random number generator.
193
194=back
195
196For rands that are also deterministic random bit generators (DRBGs), these
197additional parameters are recognised. Not all
198parameters are relevant to, or are understood by all DRBG rands:
199
200=over 4
201
202=item "reseed_requests" (B<OSSL_DRBG_PARAM_RESEED_REQUESTS>) <unsigned integer>
203
204Reads or set the number of generate requests before reseeding the
205associated RAND ctx.
206
207=item "reseed_time_interval" (B<OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL>) <integer>
208
209Reads or set the number of elapsed seconds before reseeding the
210associated RAND ctx.
211
212=item "max_request" (B<OSSL_DRBG_PARAM_RESEED_REQUESTS>) <unsigned integer>
213
214Specifies the maximum number of bytes that can be generated in a single
215call to OSSL_FUNC_rand_generate.
216
217=item "min_entropylen" (B<OSSL_DRBG_PARAM_MIN_ENTROPYLEN>) <unsigned integer>
218
219=item "max_entropylen" (B<OSSL_DRBG_PARAM_MAX_ENTROPYLEN>) <unsigned integer>
220
221Specify the minimum and maximum number of bytes of random material that
222can be used to seed the DRBG.
223
224=item "min_noncelen" (B<OSSL_DRBG_PARAM_MIN_NONCELEN>) <unsigned integer>
225
226=item "max_noncelen" (B<OSSL_DRBG_PARAM_MAX_NONCELEN>) <unsigned integer>
227
228Specify the minimum and maximum number of bytes of nonce that can be used to
229instantiate the DRBG.
230
231=item "max_perslen" (B<OSSL_DRBG_PARAM_MAX_PERSLEN>) <unsigned integer>
232
233=item "max_adinlen" (B<OSSL_DRBG_PARAM_MAX_ADINLEN>) <unsigned integer>
234
235Specify the minimum and maximum number of bytes of personalisation string
236that can be used with the DRBG.
237
238=item "reseed_counter" (B<OSSL_DRBG_PARAM_RESEED_COUNTER>) <unsigned integer>
239
240Specifies the number of times the DRBG has been seeded or reseeded.
241
242=item "digest" (B<OSSL_DRBG_PARAM_DIGEST>) <UTF8 string>
243
244=item "cipher" (B<OSSL_DRBG_PARAM_CIPHER>) <UTF8 string>
245
246=item "mac" (B<OSSL_DRBG_PARAM_MAC>) <UTF8 string>
247
248Sets the name of the underlying cipher, digest or MAC to be used.
249It must name a suitable algorithm for the DRBG that's being used.
250
251=item "properties" (B<OSSL_DRBG_PARAM_PROPERTIES>) <UTF8 string>
252
253Sets the properties to be queried when trying to fetch an underlying algorithm.
254This must be given together with the algorithm naming parameter to be
255considered valid.
256
257=back
258
259=head1 RETURN VALUES
260
261OSSL_FUNC_rand_newctx() should return the newly created
262provider side rand context, or NULL on failure.
263
264OSSL_FUNC_rand_gettable_params(), OSSL_FUNC_rand_gettable_ctx_params() and
265OSSL_FUNC_rand_settable_ctx_params() should return a constant B<OSSL_PARAM>
266array, or NULL if none is offered.
267
268OSSL_FUNC_rand_nonce() returns the size of the generated nonce, or 0 on error.
269
270OSSL_FUNC_rand_get_seed() returns the size of the generated seed, or 0 on
271error.
272
273All of the remaining functions should return 1 for success or 0 on error.
274
275=head1 NOTES
276
277The RAND life-cycle is described in L<life_cycle-rand(7)>.  Providers should
278ensure that the various transitions listed there are supported.  At some point
279the EVP layer will begin enforcing the listed transitions.
280
281=head1 SEE ALSO
282
283L<provider(7)>,
284L<RAND(7)>,
285L<EVP_RAND(7)>,
286L<life_cycle-rand(7)>,
287L<EVP_RAND(3)>
288
289=head1 HISTORY
290
291The provider RAND interface was introduced in OpenSSL 3.0.
292
293=head1 COPYRIGHT
294
295Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
296
297Licensed under the Apache License 2.0 (the "License").  You may not use
298this file except in compliance with the License.  You can obtain a copy
299in the file LICENSE in the source distribution or at
300L<https://www.openssl.org/source/license.html>.
301
302=cut
303