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EVP_RAND-TEST-RAND

(7ssl)

The test EVP_RAND implementation

Overview, conventions, miscellanyopenssl 3.5.6-1~deb13u2

DESCRIPTION

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

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

The supported parameters are:

"state" (OSSL_RAND_PARAM_STATE) <integer>
"fips-indicator" (OSSL_RAND_PARAM_FIPS_APPROVED_INDICATOR) <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.

See also

EVP_RAND(7ssl)