4746f25ac6
[skip ci] Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7829)
61 lines
1.9 KiB
Text
61 lines
1.9 KiB
Text
=pod
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=head1 NAME
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RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes - query entropy gathering daemon
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=head1 SYNOPSIS
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#include <openssl/rand.h>
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int RAND_egd_bytes(const char *path, int num);
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int RAND_egd(const char *path);
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int RAND_query_egd_bytes(const char *path, unsigned char *buf, int num);
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=head1 DESCRIPTION
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On older platforms without a good source of randomness such as C</dev/urandom>,
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it is possible to query an Entropy Gathering Daemon (EGD) over a local
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socket to obtain randomness and seed the OpenSSL RNG.
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The protocol used is defined by the EGDs available at
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L<http://egd.sourceforge.net/> or L<http://prngd.sourceforge.net>.
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RAND_egd_bytes() requests B<num> bytes of randomness from an EGD at the
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specified socket B<path>, and passes the data it receives into RAND_add().
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RAND_egd() is equivalent to RAND_egd_bytes() with B<num> set to 255.
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RAND_query_egd_bytes() requests B<num> bytes of randomness from an EGD at
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the specified socket B<path>, where B<num> must be less than 256.
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If B<buf> is B<NULL>, it is equivalent to RAND_egd_bytes().
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If B<buf> is not B<NULL>, then the data is copied to the buffer and
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RAND_add() is not called.
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OpenSSL can be configured at build time to try to use the EGD for seeding
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automatically.
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=head1 RETURN VALUES
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RAND_egd() and RAND_egd_bytes() return the number of bytes read from the
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daemon on success, or -1 if the connection failed or the daemon did not
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return enough data to fully seed the PRNG.
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RAND_query_egd_bytes() returns the number of bytes read from the daemon on
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success, or -1 if the connection failed.
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=head1 SEE ALSO
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L<RAND_add(3)>,
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L<RAND_bytes(3)>,
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L<RAND(7)>
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=head1 COPYRIGHT
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Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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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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