NAME
cap_rights_limit — limit capability rights
LIBRARY
Standard C Library (libc, −lc)
SYNOPSIS
#include <sys/capsicum.h>
int
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_open(2), open(2), openat(2), pdfork(2), pipe(2), shm_open(2), socket(2) or socketpair(2), it is assigned all capability rights. Those rights can be reduced (but never expanded) by using the cap_rights_limit() system call. Once capability rights are reduced, operations on the file descriptor will be limited to those permitted by rights.
The rights argument should be prepared using cap_rights_init(3) family of functions.
Capability rights assigned to a file descriptor can be obtained with the cap_rights_get(3) function.
The complete list of the capability rights can be found in the rights(4) manual page.
RETURN VALUES
Upon successful completion, the value 0 is returned; otherwise the value −1 is returned and the global variable errno is set to indicate the error.
EXAMPLES
The following example demonstrates how to limit file descriptor capability rights to allow reading only.
cap_rights_t
setrights;
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"); |
ERRORS
cap_rights_limit() succeeds unless:
[EBADF]
The fd argument is not a valid active descriptor.
[EINVAL]
An invalid right has been requested in rights.
[ENOTCAPABLE]
The rights argument contains capability rights not present for the given file descriptor. Capability rights list can only be reduced, never expanded.
SEE ALSO
accept(2), accept4(2), cap_enter(2), fhopen(2), kqueue(2), mq_open(2), open(2), openat(2), pdfork(2), pipe(2), read(2), shm_open(2), socket(2), socketpair(2), write(2), cap_rights_get(3), cap_rights_init(3), err(3), capsicum(4), rights(4)
HISTORY
Support for capabilities and capabilities mode was developed as part of the TrustedBSD Project.
AUTHORS
This function was created by Pawel Jakub Dawidek <pawel [AT] dawidek.net> under sponsorship of the FreeBSD Foundation.
BSD March 27, 2014 BSD