RAND_egd3ssl
Query entropy gathering daemon
Usage
#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);
Overview
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.
Releases
13 releases since Debian 3.0 (Woody); the text changed 12 times.