#include <openssl/rand.h> int RAND_egd_bytes(const char *path, int num); int RAND_egd(const char *path); int RAND_query_egd_bytes(const char *path, unsigned char *buf, int num);
On older platforms without a good source of randomness such as
/dev/urandom, it is possible to query an Entropy Gathering Daemon (EGD) over a local socket to obtain randomness and seed the OpenSSL RNG. The protocol used is defined by the EGDs available at <http://egd.sourceforge.net/> or <http://prngd.sourceforge.net>.
RAND_egd_bytes() requests num bytes of randomness from an EGD at the specified socket path, and passes the data it receives into RAND_add(). RAND_egd() is equivalent to RAND_egd_bytes() with num set to 255.
RAND_query_egd_bytes() requests num bytes of randomness from an EGD at the specified socket path, where num must be less than 256. If buf is NULL, it is equivalent to RAND_egd_bytes(). If buf is not NULL, then the data is copied to the buffer and RAND_add() is not called.
OpenSSL can be configured at build time to try to use the EGD for seeding automatically.
RAND_egd() and RAND_egd_bytes() return the number of bytes read from the daemon on success, or -1 if the connection failed or the daemon did not return enough data to fully seed the PRNG.
RAND_query_egd_bytes() returns the number of bytes read from the daemon on success, or -1 if the connection failed.
RAND_add(3), RAND_bytes(3), RAND(7)
Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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 <https://www.openssl.org/source/license.html>.
The man pages RAND_egd_bytes.3ssl(3) and RAND_query_egd_bytes.3ssl(3) are aliases of RAND_egd.3ssl(3).