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CAP_RIGHTS_LIMIT(2)	    BSD	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 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	as-
     signed all	capability rights.  Those rights can be	reduced	(but never ex-
     panded) 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 capabil-
     ity 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@dawidek.net> un-
     der sponsorship of	the FreeBSD Foundation.

BSD				March 27, 2014				   BSD
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | ERRORS | SEE ALSO | HISTORY | AUTHORS

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