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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), accept4(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, 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 capa- bility 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 CAPABILITY_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 15.0 April 27, 2024 CAP_RIGHTS_LIMIT(2)
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUES | EXAMPLES | ERRORS | SEE ALSO | HISTORY | AUTHORS
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