|CAP_RIGHTS_LIMIT(2)||FreeBSD System Calls Manual||CAP_RIGHTS_LIMIT(2)|
NAMEcap_rights_limit — limit capability rights
LIBRARYStandard C Library (libc, -lc)
SYNOPSIS#include < sys/capability.h>
cap_rights_limit( int fd, const cap_rights_t *rights);
DESCRIPTIONWhen 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 VALUESUpon successful completion, the value 0 is returned; otherwise the value -1 is returned and the global variable errno is set to indicate the error.
EXAMPLESThe following example demonstrates how to limit file descriptor capability rights to allow reading only.
cap_rights_t rights; char buf; 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 = 'X'; if (write(fd, buf, sizeof(buf)) > 0) errx(1, "write() succeeded!"); if (read(fd, buf, sizeof(buf)) < 0) err(1, "read() failed");
ERRORScap_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 ALSOaccept(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)
HISTORYSupport for capabilities and capabilities mode was developed as part of the TrustedBSD Project.
AUTHORSThis function was created by <firstname.lastname@example.org> under sponsorship of the FreeBSD Foundation.
|February 23, 2013||FreeBSD|