2020-11-20 06:45:34 +08:00
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=pod
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=head1 NAME
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EVP_RAND-SEED-SRC - The randomness seed source EVP_RAND implementation
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=head1 DESCRIPTION
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Support for deterministic random number generator seeding through the
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B<EVP_RAND> API.
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The seed sources used are specified at the time OpenSSL is configured for
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building using the B<--with-rand-seed=> option. By default, operating system
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randomness sources are used.
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=head2 Identity
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"SEED-SRC" is the name for this implementation; it can be used with the
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EVP_RAND_fetch() function.
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=head2 Supported parameters
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The supported parameters are:
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=over 4
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=item "state" (B<OSSL_RAND_PARAM_STATE>) <integer>
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=item "strength" (B<OSSL_RAND_PARAM_STRENGTH>) <unsigned integer>
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=item "max_request" (B<OSSL_RAND_PARAM_MAX_REQUEST>) <unsigned integer>
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These parameters work as described in L<EVP_RAND(3)/PARAMETERS>.
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=back
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=head1 NOTES
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A context for the seed source can be obtained by calling:
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EVP_RAND *rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL);
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2022-07-19 11:40:34 +08:00
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EVP_RAND_CTX *rctx = EVP_RAND_CTX_new(rand, NULL);
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2020-11-20 06:45:34 +08:00
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=head1 EXAMPLES
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EVP_RAND *rand;
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EVP_RAND_CTX *seed, *rctx;
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unsigned char bytes[100];
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OSSL_PARAM params[2], *p = params;
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unsigned int strength = 128;
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/* Create a seed source */
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rand = EVP_RAND_fetch(NULL, "SEED-SRC", NULL);
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seed = EVP_RAND_CTX_new(rand, NULL);
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EVP_RAND_free(rand);
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/* Feed this into a DRBG */
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rand = EVP_RAND_fetch(NULL, "CTR-DRBG", NULL);
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rctx = EVP_RAND_CTX_new(rand, seed);
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EVP_RAND_free(rand);
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/* Configure the DRBG */
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*p++ = OSSL_PARAM_construct_utf8_string(OSSL_DRBG_PARAM_CIPHER,
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SN_aes_256_ctr, 0);
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*p = OSSL_PARAM_construct_end();
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2021-02-26 08:56:46 +08:00
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EVP_RAND_instantiate(rctx, strength, 0, NULL, 0, params);
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2020-11-20 06:45:34 +08:00
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EVP_RAND_generate(rctx, bytes, sizeof(bytes), strength, 0, NULL, 0);
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EVP_RAND_CTX_free(rctx);
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EVP_RAND_CTX_free(seed);
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=head1 SEE ALSO
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L<EVP_RAND(3)>,
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L<EVP_RAND(3)/PARAMETERS>
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=head1 COPYRIGHT
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2021-03-11 21:27:36 +08:00
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Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
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2020-11-20 06:45:34 +08:00
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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