evp_rand: documentation

EVP_RAND, the RNGs and provider-rand.

Reviewed-by: Matthias St. Pierre <Matthias.St.Pierre@ncp-e.com>
(Merged from https://github.com/openssl/openssl/pull/11682)

1 files changed, 113 insertions, 0 deletions

diff --git a/doc/man7/EVP_RAND-TEST-RAND.pod b/doc/man7/EVP_RAND-TEST-RAND.pod
new file mode 100644
index 0000000000..4736b5a976
--- /dev/null
+++ b/doc/man7/EVP_RAND-TEST-RAND.pod
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+=pod
+
+=head1 NAME
+
+EVP_RAND-TEST-RAND - The test EVP_RAND implementation
+
+=head1 DESCRIPTION
+
+Support for a test generator through the B<EVP_RAND> API. This generator is
+for test purposes only, it does not generate random numbers.
+
+=head2 Identity
+
+"TEST-RAND" is the name for this implementation; it can be used with the
+EVP_RAND_fetch() function.
+
+=head2 Supported parameters
+
+The supported parameters are:
+
+=over 4
+
+=item "state" (B<OSSL_RAND_PARAM_STATE>) <integer>
+
+These parameter works as described in L<EVP_RAND(3)/PARAMETERS>.
+
+=item "strength" (B<OSSL_RAND_PARAM_STRENGTH>) <unsigned integer>
+
+=item "reseed_requests" (B<OSSL_DRBG_PARAM_RESEED_REQUESTS>) <unsigned integer>
+
+=item "reseed_time_interval" (B<OSSL_DRBG_PARAM_RESEED_TIME_INTERVAL>) <integer>
+
+=item "max_request" (B<OSSL_DRBG_PARAM_RESEED_REQUESTS>) <unsigned integer>
+
+=item "min_entropylen" (B<OSSL_DRBG_PARAM_MIN_ENTROPYLEN>) <unsigned integer>
+
+=item "max_entropylen" (B<OSSL_DRBG_PARAM_MAX_ENTROPYLEN>) <unsigned integer>
+
+=item "min_noncelen" (B<OSSL_DRBG_PARAM_MIN_NONCELEN>) <unsigned integer>
+
+=item "max_noncelen" (B<OSSL_DRBG_PARAM_MAX_NONCELEN>) <unsigned integer>
+
+=item "max_perslen" (B<OSSL_DRBG_PARAM_MAX_PERSLEN>) <unsigned integer>
+
+=item "max_adinlen" (B<OSSL_DRBG_PARAM_MAX_ADINLEN>) <unsigned integer>
+
+=item "reseed_counter" (B<OSSL_DRBG_PARAM_RESEED_CTR>) <unsigned integer>
+
+These parameters work as described in L<EVP_RAND(3)/PARAMETERS>, except that
+they can all be set as well as read.
+
+=item "test_entropy" (B<OSSL_RAND_PARAM_TEST_ENTROPY>) <octet string>
+
+Sets the bytes returned when the test generator is sent an entropy request.
+When entropy is requested, these bytes are treated as a cyclic buffer and they
+are repeated as required.  The current position is remembered across generate
+calls.
+
+=item "test_nonce" (B<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.
+
+=back
+
+=head1 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);
+
+=head1 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_set_ctx_params(rctx, params);
+
+ EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
+
+ EVP_RAND_CTX_free(rctx);
+
+=head1 SEE ALSO
+
+L<EVP_RAND(3)>,
+L<EVP_RAND(3)/PARAMETERS>
+
+=head1 COPYRIGHT
+
+Copyright 2020 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
+L<https://www.openssl.org/source/license.html>.
+
+=cut