CAP_RIGHTS_LIMIT(2)

NAME
cap_rights_limit, cap_rights_get - manage capability rights

LIBRARY
libc

SYNOPSIS
#include <sys/capability.h>
int
cap_rights_limit(int fd, cap_rights_t rights);
int
cap_rights_get(int fd, cap_rights_t *rightsp);

DESCRIPTION
When a file descriptor is created by a function such as 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.

A bitmask of capability rights assigned to a file descriptor can be obtained with the cap_rights_get() system call.

RIGHTS
The following rights may be specified in a rights mask:

CAP_ACCEPT
    Permit accept(2) and accept4(2).

CAP_ACL_CHECK
    Permit checking of an ACL on a file descriptor; there is no cross-reference for this system call.

CAP_ACL_DELETE
    Permit acl_delete_fd_np(3).

CAP_ACL_GET
    Permit acl_get_fd(3) and acl_get_fd_np(3).

CAP_ACL_SET
    Permit acl_set_fd(3) and acl_set_fd_np(3).

CAP_BIND
    Permit bind(2). Note that sockets can also become bound implicitly as a result of connect(2) or send(2), and that socket options set with setsockopt(2) may also affect binding behavior.

CAP_BINDAT
    Permit bindat(2). This right has to be present on the directory descriptor.

CAP_CONNECT
    Permit connect(2); also required for sendto(2) with a non-NULL destination address.

CAP_CONNECTAT
    Permit connectat(2). This right has to be present on the directory descriptor.

CAP_CREATE
    Permit openat(2) with the O_CREAT flag.

CAP_EVENT
    Permit select(2), poll(2), and kevent(2) to be used in monitoring the file descriptor for events.

CAP_FEXECVE
    Permit fexecve(2) and openat(2) with the O_EXEC flag; CAP_READ will also be required.

CAP_EXTATTR_DELETE
    Permit extattr_delete_fd(2).

CAP_EXTATTR_GET
    Permit extattr_get_fd(2).

CAP_EXTATTR_LIST
    Permit extattr_list_fd(2).

CAP_EXTATTR_SET
    Permit extattr_set_fd(2).

CAP_FCHDIR
    Permit fchdir(2).

CAP_FCHFLAGS
    Permit fchflags(2) and chflagsat(2).

CAP_CHFLAGSAT
    An alias to CAP_FCHFLAGS.

CAP_FCHMOD
    Permit fchmod(2) and fchmodat(2).

CAP_FCHMODAT
    An alias to CAP_FCHMOD.

CAP_FCHOWN
    Permit fchown(2) and fchownat(2).

CAP_FCHOWNAT
    An alias to CAP_FCHOWN.

CAP_FCNTL
    Permit fcntl(2). Note that only the F_GETFL, F_SETFL, F_GETOWN and F_SETOWN commands require this capability right. Also note that the list of permitted commands can be further limited with the cap_fcntls_limit(2) system call.

CAP_FLOCK
    Permit flock(2), fcntl(2) (with F_GETLK, F_SETLK or F_SETLKW flag) and openat(2) (with O_EXLOCK or O_SHLOCK flag).

CAP_FPATHCONF
    Permit fpathconf(2).

CAP_FSCK
    Permit UFS background-fsck operations on the descriptor.

CAP_FSTAT
    Permit fstat(2) and fstatat(2).

CAP_FSTATAT
    An alias to CAP_FSTAT.

CAP_FSTATFS
    Permit fstatfs(2).

CAP_FSYNC
    Permit aio_fsync(2), fsync(2) and openat(2) with O_FSYNC or O_SYNC flag.

CAP_FTRUNCATE
    Permit ftruncate(2) and openat(2) with the O_TRUNC flag.

CAP_FUTIMES
    Permit futimes(2) and futimesat(2).

CAP_FUTIMESAT
    An alias to CAP_FUTIMES.

CAP_GETPEERNAME
    Permit getpeername(2).

CAP_GETSOCKNAME
    Permit getsockname(2).

CAP_GETSOCKOPT
    Permit getsockopt(2).

CAP_IOCTL
    Permit ioctl(2). Be aware that this system call has enormous scope, including potentially global scope for some objects. The list of permitted ioctl commands can be further limited with the cap_ioctls_limit(2) system call.

CAP_KEVENT
    Permit kevent(2); CAP_EVENT is also required on file descriptors that will be monitored using kevent(2).

CAP_LINKAT
    Permit linkat(2) and renameat(2). This right is required for the destination directory descriptor.

CAP_LISTEN
    Permit listen(2); not much use (generally) without CAP_BIND.

CAP_LOOKUP
    Permit the file descriptor to be used as a starting directory for calls such as linkat(2), openat(2), and unlinkat(2).

CAP_MAC_GET
    Permit mac_get_fd(3).

CAP_MAC_SET
    Permit mac_set_fd(3).

CAP_MKDIRAT
    Permit mkdirat(2).

CAP_MKFIFOAT
    Permit mkfifoat(2).

CAP_MKNODAT
    Permit mknodat(2).

CAP_MMAP
    Permit mmap(2) with the PROT_NONE protection.

CAP_MMAP_R
    Permit mmap(2) with the PROT_READ protection. This also implies CAP_READ and CAP_SEEK rights.

CAP_MMAP_W
    Permit mmap(2) with the PROT_WRITE protection. This also implies CAP_WRITE and CAP_SEEK rights.

CAP_MMAP_X
    Permit mmap(2) with the PROT_EXEC protection. This also implies CAP_SEEK right.

CAP_MMAP_RW
    Implies CAP_MMAP_R and CAP_MMAP_W.

CAP_MMAP_RX
    Implies CAP_MMAP_R and CAP_MMAP_X.

CAP_MMAP_WX
    Implies CAP_MMAP_W and CAP_MMAP_X.

CAP_MMAP_RWX
    Implies CAP_MMAP_R, CAP_MMAP_W and CAP_MMAP_X.

CAP_PDGETPID
    Permit pdgetpid(2).

CAP_PDKILL
    Permit pdkill(2).

CAP_PDWAIT
    Permit pdwait4(2).

CAP_PEELOFF
    Permit sctp_peeloff(2).

CAP_POLL_EVENT

CAP_POST_EVENT

CAP_PREAD
    Implies CAP_SEEK and CAP_READ.

CAP_PWRITE
    Implies CAP_SEEK and CAP_WRITE.

CAP_READ
    Allow aio_read(2), openat with the O_RDONLY flag, read(2), recv(2), recvfrom(2), recvmsg(2) and related system calls.

CAP_RECV
    An alias to CAP_READ.

CAP_RENAMEAT
    Permit renameat(2). This right is required for the source directory descriptor.

CAP_SEEK
    Permit operations that seek on the file descriptor, such as lseek(2), but also required for I/O system calls that can read or write at any position in the file, such as pread(2) and pwrite(2).

CAP_SEM_GETVALUE
    Permit sem_getvalue(3).

CAP_SEM_POST
    Permit sem_post(3).

CAP_SEM_WAIT
    Permit sem_wait(3) and sem_trywait(3).

CAP_SEND
    An alias to CAP_WRITE.

CAP_SETSOCKOPT
    Permit setsockopt(2); this controls various aspects of socket behavior and may affect binding, connecting, and other behaviors with global scope.

CAP_SHUTDOWN
    Permit explicit shutdown(2); closing the socket will also generally shut down any connections on it.

CAP_SYMLINKAT
    Permit symlinkat(2).

CAP_TTYHOOK
    Allow configuration of TTY hooks, such as snp(4), on the file descriptor.

CAP_UNLINKAT
    Permit unlinkat(2) and renameat(2). This right is only required for renameat(2) on the destination directory descriptor if the destination object already exists and will be removed by the rename.

CAP_WRITE
    Allow aio_write(2), openat(2) with O_WRONLY and O_APPEND flags, send(2), sendmsg(2), sendto(2), write(2), and related system calls. For sendto(2) with a non-NULL connection address, CAP_CONNECT is also required. For openat(2) with the O_WRONLY flag, but without the O_APPEND flag, CAP_SEEK is also required.

RETURN VALUES

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]
    rights contains requested rights not present in the current rights mask associated with the given file descriptor.

cap_rights_get() succeeds unless:

[EBADF]
    The fd argument is not a valid active descriptor.

[EFAULT]
    The rightsp argument points at an invalid address.

SEE ALSO
accept(2), aio_fsync(2), aio_read(2), aio_write(2), bind(2), bindat(2), cap_enter(2), cap_fcntls_limit(2), cap_ioctls_limit(2), cap_rights_limit(2), connect(2), connectat(2), dup(2), dup2(2), extattr_delete_fd(2), extattr_get_fd(2), extattr_list_fd(2), extattr_set_fd(2), fchflags(2), fchown(2), fcntl(2), fexecve(2), fhopen(2), flock(2), fpathconf(2), fstat(2), fstatfs(2), fsync(2), ftruncate(2), futimes(2), getpeername(2), getsockname(2), getsockopt(2), ioctl(2), kevent(2), kqueue(2), linkat(2), listen(2), mmap(2), mq_open(2), open(2), openat(2), pdfork(2), pdgetpid(2), pdkill(2), pdwait4(2), pipe(2), poll(2), pread(2), pwrite(2), read(2), recv(2), recvfrom(2), recvmsg(2), renameat(2), sctp_peeloff(2), select(2), send(2), sendmsg(2), sendto(2), setsockopt(2), shm_open(2), shutdown(2), socket(2), socketpair(2), symlinkat(2), unlinkat(2), write(2), acl_delete_fd_np(3), acl_get_fd(3), acl_get_fd_np(3), acl_set_fd_np(3), cap_limitfd(3), libcapsicum(3), mac_get_fd(3), mac_set_fd(3), sem_getvalue(3), sem_post(3), sem_trywait(3), sem_wait(3), capsicum(4), snp(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> under sponsorship of the FreeBSD Foundation.

BUGS
This man page should list the set of permitted system calls more specifically for each capability right.

Capability rights sometimes have unclear indirect impacts, which should be documented, or at least hinted at.