NAME

       EVP_RAND-TEST-RAND - The test EVP_RAND implementation

DESCRIPTION

       Support for a test generator through the EVP_RAND API. This generator is for test purposes
       only, it does not generate random numbers.

   Identity
       "TEST-RAND" is the name for this implementation; it can be used with the EVP_RAND_fetch()
       function.

   Supported parameters
       The supported parameters are:

       "state" (OSSL_RAND_PARAM_STATE) <integer>
           These parameter works as described in "PARAMETERS" in EVP_RAND(3).

       "strength" (OSSL_RAND_PARAM_STRENGTH) <unsigned integer>
       "reseed_requests" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>
       "reseed_time_interval" (OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL) <integer>
       "max_request" (OSSL_DRBG_PARAM_RESEED_REQUESTS) <unsigned integer>
       "min_entropylen" (OSSL_DRBG_PARAM_MIN_ENTROPYLEN) <unsigned integer>
       "max_entropylen" (OSSL_DRBG_PARAM_MAX_ENTROPYLEN) <unsigned integer>
       "min_noncelen" (OSSL_DRBG_PARAM_MIN_NONCELEN) <unsigned integer>
       "max_noncelen" (OSSL_DRBG_PARAM_MAX_NONCELEN) <unsigned integer>
       "max_perslen" (OSSL_DRBG_PARAM_MAX_PERSLEN) <unsigned integer>
       "max_adinlen" (OSSL_DRBG_PARAM_MAX_ADINLEN) <unsigned integer>
       "reseed_counter" (OSSL_DRBG_PARAM_RESEED_COUNTER) <unsigned integer>
           These parameters work as described in "PARAMETERS" in EVP_RAND(3), except that they
           can all be set as well as read.

       "test_entropy" (OSSL_RAND_PARAM_TEST_ENTROPY) <octet string>
           Sets the bytes returned when the test generator is sent an entropy request.  The
           current position is remembered across generate calls.  If there are insufficient data
           present to satisfy a call, an error is returned.

       "test_nonce" (OSSL_RAND_PARAM_TEST_NONCE) <octet string>
           Sets the bytes returned when the test generator is sent a nonce request.  Each nonce
           request will return all of the bytes.

       "generate" (OSSL_RAND_PARAM_GENERATE) <integer>
           If this parameter is zero, it will only emit the nonce and entropy data supplied via
           the aforementioned parameters.  Otherwise, low quality non-cryptographic pseudorandom
           output is produced.  This parameter defaults to zero.

NOTES

       A context for a test generator can be obtained by calling:

        EVP_RAND *rand = EVP_RAND_fetch(NULL, "TEST-RAND", NULL);
        EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);

EXAMPLES

        EVP_RAND *rand;
        EVP_RAND_CTX *rctx;
        unsigned char bytes[100];
        OSSL_PARAM params[4], *p = params;
        unsigned char entropy[1000] = { ... };
        unsigned char nonce[20] = { ... };
        unsigned int strength = 48;

        rand = EVP_RAND_fetch(NULL, "TEST-RAND", NULL);
        rctx = EVP_RAND_CTX_new(rand, NULL);
        EVP_RAND_free(rand);

        *p++ = OSSL_PARAM_construct_uint(OSSL_RAND_PARAM_STRENGTH, &strength);
        *p++ = OSSL_PARAM_construct_octet_string(OSSL_RAND_PARAM_TEST_ENTROPY,
                                                 entropy, sizeof(entropy));
        *p++ = OSSL_PARAM_construct_octet_string(OSSL_RAND_PARAM_TEST_NONCE,
                                                 nonce, sizeof(nonce));
        *p = OSSL_PARAM_construct_end();
        EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params);

        EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);

        EVP_RAND_CTX_free(rctx);

SEE ALSO

       EVP_RAND(3), "PARAMETERS" in EVP_RAND(3)

HISTORY

       This functionality was added in OpenSSL 3.0.

COPYRIGHT

       Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use this file except
       in compliance with the License.  You can obtain a copy in the file LICENSE in the source
       distribution or at <https://www.openssl.org/source/license.html>.