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CAP_RIGHTS_LIMIT(2)	       System Calls Manual	     CAP_RIGHTS_LIMIT(2)

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 fhopen(2),
     kqueue(2), mq_open(2), open(2), pdfork(2), pipe(2), shm_open(2),  socket(2)
     or  socketpair(2), it is assigned all capability rights; for accept(2), ac-
     cept4(2) or openat(2), it inherits capability rights from the "parent" file
     descriptor.  Those rights can be reduced (but never expanded) by using  the
     cap_rights_limit() system call.  Once capability rights are reduced, opera-
     tions 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.

     [ENOSYS]		The running kernel was compiled without options CAPABIL-
			ITY_MODE.

     [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
     The cap_rights_limit() function first appeared in FreeBSD 8.3.  Support for
     capabilities and capabilities mode was developed as part of the  TrustedBSD
     Project.

AUTHORS
     This  function was created by Pawel Jakub Dawidek <pawel@dawidek.net> under
     sponsorship of the FreeBSD Foundation.

FreeBSD ports 15.1		 April 27, 2024 	     CAP_RIGHTS_LIMIT(2)

Want to link to this manual page? Use this URL:
<https://man.freebsd.org/cgi/man.cgi?query=cap_rights_limit&sektion=2&manpath=FreeBSD+15.1-RELEASE+and+Ports>

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