doc/man7/provider-rand.pod

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