| 1 | =pod
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| 2 |
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| 3 | =head1 NAME
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| 4 |
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| 5 | RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes - query entropy gathering daemon
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| 6 |
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| 7 | =head1 SYNOPSIS
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| 8 |
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| 9 | #include <openssl/rand.h>
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| 10 |
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| 11 | int RAND_egd_bytes(const char *path, int num);
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| 12 | int RAND_egd(const char *path);
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| 13 |
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| 14 | int RAND_query_egd_bytes(const char *path, unsigned char *buf, int num);
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| 15 |
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| 16 | =head1 DESCRIPTION
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| 17 |
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| 18 | On older platforms without a good source of randomness such as C</dev/urandom>,
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| 19 | it is possible to query an Entropy Gathering Daemon (EGD) over a local
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| 20 | socket to obtain randomness and seed the OpenSSL RNG.
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| 21 | The protocol used is defined by the EGDs available at
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| 22 | L<http://egd.sourceforge.net/> or L<http://prngd.sourceforge.net>.
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| 23 |
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| 24 | RAND_egd_bytes() requests B<num> bytes of randomness from an EGD at the
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| 25 | specified socket B<path>, and passes the data it receives into RAND_add().
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| 26 | RAND_egd() is equivalent to RAND_egd_bytes() with B<num> set to 255.
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| 27 |
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| 28 | RAND_query_egd_bytes() requests B<num> bytes of randomness from an EGD at
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| 29 | the specified socket B<path>, where B<num> must be less than 256.
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| 30 | If B<buf> is B<NULL>, it is equivalent to RAND_egd_bytes().
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| 31 | If B<buf> is not B<NULL>, then the data is copied to the buffer and
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| 32 | RAND_add() is not called.
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| 33 |
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| 34 | OpenSSL can be configured at build time to try to use the EGD for seeding
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| 35 | automatically.
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| 36 |
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| 37 | =head1 RETURN VALUES
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| 38 |
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| 39 | RAND_egd() and RAND_egd_bytes() return the number of bytes read from the
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| 40 | daemon on success, or -1 if the connection failed or the daemon did not
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| 41 | return enough data to fully seed the PRNG.
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| 42 |
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| 43 | RAND_query_egd_bytes() returns the number of bytes read from the daemon on
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| 44 | success, or -1 if the connection failed.
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| 45 |
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| 46 | =head1 SEE ALSO
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| 47 |
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| 48 | L<RAND_add(3)>,
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| 49 | L<RAND_bytes(3)>,
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| 50 | L<RAND(7)>
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| 51 |
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| 52 | =head1 COPYRIGHT
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| 53 |
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| 54 | Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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| 55 |
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| 56 | Licensed under the OpenSSL license (the "License"). You may not use
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| 57 | this file except in compliance with the License. You can obtain a copy
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| 58 | in the file LICENSE in the source distribution or at
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| 59 | L<https://www.openssl.org/source/license.html>.
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| 60 |
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| 61 | =cut
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