RAND_EGD

Section: OpenSSL (3)
Updated: 2020-07-28
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NAME

RAND_egd, RAND_egd_bytes, RAND_query_egd_bytes - query entropy gathering daemon

SYNOPSIS

 #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);

DESCRIPTION

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.

RETURN VALUES

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.

COPYRIGHT

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>.