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);

HISTORY

This functionality was added in OpenSSL 3.0.

COPYRIGHT

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.