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     Capability rights — Capsicum capability rights for file descriptors


     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 assigned all capability rights.  Those rights can be reduced (but never
     expanded) by using the cap_rights_limit(2), cap_fcntls_limit(2) and cap_ioctls_limit(2)
     system calls.  Once capability rights are reduced, operations on the file descriptor will be
     limited to those permitted by rights.

     The complete list of capability rights is provided below.  The cap_rights_t type is used to
     store list of capability rights.  The cap_rights_init(3) family of functions should be used
     to manage the structure.


     The following rights may be specified in a rights mask:

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

     CAP_ACL_CHECK       Permit acl_valid_fd_np(3).

     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.  This right includes the CAP_LOOKUP right.


     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.  This right includes the CAP_LOOKUP right.

     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_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) if the CAP_LOOKUP right is also

     CAP_FCHMOD          Permit fchmod(2) and fchmodat(2) if the CAP_LOOKUP right is also

     CAP_FCHMODAT        An alias to CAP_FCHMOD and CAP_LOOKUP.

     CAP_FCHOWN          Permit fchown(2) and fchownat(2) if the CAP_LOOKUP right is also

     CAP_FCHOWNAT        An alias to CAP_FCHOWN and CAP_LOOKUP.

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

     CAP_FLOCK           Permit flock(2), fcntl(2) (with F_GETLK, F_SETLK, F_SETLKW or
                         F_SETLK_REMOTE 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) if the CAP_LOOKUP right is also present.

     CAP_FSTATAT         An alias to CAP_FSTAT and CAP_LOOKUP.

     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) if the CAP_LOOKUP right is also

     CAP_FUTIMESAT       An alias to CAP_FUTIMES and CAP_LOOKUP.

     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_KQUEUE_CHANGE   Permit kevent(2) on a kqueue(2) descriptor that modifies list of
                         monitored events (the changelist argument is non-NULL).

     CAP_KQUEUE_EVENT    Permit kevent(2) on a kqueue(2) descriptor that monitors events (the
                         eventlist argument is non-NULL).  CAP_EVENT is also required on file
                         descriptors that will be monitored using kevent(2).

     CAP_LINKAT          Permit linkat(2) and renameat(2) on the destination directory
                         descriptor.  This right includes the CAP_LOOKUP right.

     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).  This right includes the CAP_LOOKUP right.

     CAP_MKFIFOAT        Permit mkfifoat(2).  This right includes the CAP_LOOKUP right.

     CAP_MKNODAT         Permit mknodat(2).  This right includes the CAP_LOOKUP right.

     CAP_MMAP            Permit mmap(2) with the PROT_NONE protection.

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

     CAP_MMAP_RW         An alias to CAP_MMAP_R and CAP_MMAP_W.

     CAP_MMAP_RWX        An alias to CAP_MMAP_R, CAP_MMAP_W and CAP_MMAP_X.

     CAP_MMAP_RX         An alias to CAP_MMAP_R and CAP_MMAP_X.

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

     CAP_MMAP_WX         An alias to CAP_MMAP_W and CAP_MMAP_X.

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

     CAP_PDGETPID        Permit pdgetpid(2).

     CAP_PDKILL          Permit pdkill(2).

     CAP_PDWAIT          Permit pdwait4(2).

     CAP_PEELOFF         Permit sctp_peeloff(2).

     CAP_PREAD           An alias to CAP_READ and CAP_SEEK.

     CAP_PWRITE          An alias to CAP_SEEK and CAP_WRITE.

     CAP_READ            Permit aio_read(2) (CAP_SEEK is also required), openat(2) with the
                         O_RDONLY flag, read(2), readv(2), recv(2), recvfrom(2), recvmsg(2),
                         pread(2) (CAP_SEEK is also required), preadv(2) (CAP_SEEK is also
                         required) and related system calls.

     CAP_RECV            An alias to CAP_READ.

     CAP_RENAMEAT        Permit renameat(2).  This right is required on the source directory
                         descriptor.  This right includes the CAP_LOOKUP right.

     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

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

     CAP_SYMLINKAT       Permit symlinkat(2).  This right includes the CAP_LOOKUP right.

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

     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.  This right
                         includes the CAP_LOOKUP right.

     CAP_WRITE           Allow aio_write(2), openat(2) with O_WRONLY and O_APPEND flags set,
                         send(2), sendmsg(2), sendto(2), write(2), writev(2), pwrite(2),
                         pwritev(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.  For aio_write(2), pwrite(2) and pwritev(2) CAP_SEEK is also


     accept(2), accept4(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), chflagsat(2),
     connect(2), connectat(2), extattr_delete_fd(2), extattr_get_fd(2), extattr_list_fd(2),
     extattr_set_fd(2), fchflags(2), fchmod(2), fchmodat(2), fchown(2), fchownat(2), fcntl(2),
     fexecve(2), fhopen(2), flock(2), fpathconf(2), fstat(2), fstatat(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), preadv(2),
     pwrite(2), pwritev(2), read(2), readv(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), writev(2),
     acl_delete_fd_np(3), acl_get_fd(3), acl_get_fd_np(3), acl_set_fd(3), acl_set_fd_np(3),
     acl_valid_fd_np(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)


     Support for capabilities and capabilities mode was developed as part of the TrustedBSD


     This manual page was created by Pawel Jakub Dawidek <> under sponsorship
     from the FreeBSD Foundation based on cap_new(2) manual page by
     Robert Watson <>.