NAME
cap_random_buf —
library for getting entropy in
capability mode
LIBRARY
library “libcap_random”
SYNOPSIS
#include
<sys/nv.h>
#include <libcasper.h>
#include
<casper/cap_random.h>
int
cap_random_buf(cap_channel_t
*chan, void *buf,
size_t nbytes);
DESCRIPTION
The functioncap_random_buf()
is equivalent to
arc4random_buf(3) except that the connection to the
system.random service needs to be provided.
EXAMPLES
The following example first opens a capability to casper and then
uses this capability to create the system.random
casper service to obtain entropy.
cap_channel_t *capcas, *caprandom;
unsigned char buf[16];
int i;
/* Open capability to Casper. */
capcas = cap_init();
if (capcas == NULL)
err(1, "Unable to contact Casper");
/* Enter capability mode sandbox. */
if (cap_enter() < 0 && errno != ENOSYS)
err(1, "Unable to enter capability mode");
/* Use Casper capability to create capability to the system.random service. */
caprandom = cap_service_open(capcas, "system.random");
if (caprandom == NULL)
err(1, "Unable to open system.random service");
/* Close Casper capability, we don't need it anymore. */
cap_close(capcas);
/* Obtain entropy. */
if (cap_random_buf(caprandom, buf, sizeof(buf)) < 0)
err(1, "Unable to obtain entropy");
for (i = 0; i < sizeof(buf); i++)
printf("%.2x ", buf[i]);
printf("\n");
SEE ALSO
AUTHORS
The cap_random service was implemented by
Pawel Jakub Dawidek
<pawel@dawidek.net>
under sponsorship from the FreeBSD Foundation.
This manual page was written by
Mariusz Zaborski
<oshogbo@FreeBSD.org>.