LIBRARY

Lb libc

SYNOPSIS

In sys/capability.h Ft int Fn cap_rights_limit int fd const cap_rights_t *rights

DESCRIPTION

When a file descriptor is created by a function such as accept(2), accept4(2), fhopen(2), kqueue(2), mq_open2, open(2), openat(2), pdfork(2), pipe(2), shm_open2, socket(2) or socketpair(2), it is assigned all capability rights. Those rights can be reduced (but never expanded) by using the Fn cap_rights_limit system call. Once capability rights are reduced, operations on the file descriptor will be limited to those permitted by Fa rights .

The Fa rights argument should be prepared using cap_rights_init3 family of functions.

Capability rights assigned to a file descriptor can be obtained with the cap_rights_get3 function.

The complete list of the capability rights can be found in the rights(4) manual page.

RETURN VALUES

Rv -std

EXAMPLES

The following example demonstrates how to limit file descriptor capability rights to allow reading only.

cap_rights_t rights;
char buf[1];
int fd;
fd = open("/tmp/foo", O_RDWR);
if (fd < 0)
        err(1, "open() failed");
if (cap_enter() < 0)
        err(1, "cap_enter() failed");
cap_rights_init(&setrights, CAP_READ);
if (cap_rights_limit(fd, &setrights) < 0)
        err(1, "cap_rights_limit() failed");
buf[0] = 'X';
if (write(fd, buf, sizeof(buf)) > 0)
        errx(1, "write() succeeded!");
if (read(fd, buf, sizeof(buf)) < 0)
        err(1, "read() failed");

HISTORY

Support for capabilities and capabilities mode was developed as part of the TrustedBSD Project.

AUTHORS

This function was created by An Pawel Jakub Dawidek Aq [email protected] under sponsorship of the FreeBSD Foundation.