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NAME
Capability rights — Capsicum capability rights for file descriptors
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
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.
RIGHTS
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 When not in capabilities mode, permit bind(2) and bindat(2) with special value
AT_FDCWD in the fd parameter. 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_CHFLAGSAT An alias to CAP_FCHFLAGS and CAP_LOOKUP.
CAP_CONNECT When not in capabilities mode, permit connect(2) and connectat(2) with special value
AT_FDCWD in the fd parameter. This right is 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 present.
CAP_FCHMOD Permit fchmod(2) and fchmodat(2) if the CAP_LOOKUP right is also present.
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 present.
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 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), fdatasync(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 futimens(2) and futimes(2), and permit futimesat(2) and utimensat(2) if the
CAP_LOOKUP right is also present.
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 An alias to CAP_KQUEUE_CHANGE and CAP_KQUEUE_EVENT.
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_SOURCE Permit linkat(2) on the source directory descriptor. This right includes the
CAP_LOOKUP right.
Warning: CAP_LINKAT_SOURCE makes it possible to link files in a directory for which
file descriptors exist that have additional rights. For example, a file stored in a
directory that does not allow CAP_READ may be linked in another directory that does
allow CAP_READ, thereby granting read access to a file that is otherwise unreadable.
CAP_LINKAT_TARGET Permit linkat(2) on the target 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_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_SOURCE Permit renameat(2) on the source directory descriptor. This right includes the
CAP_LOOKUP right.
Warning: CAP_RENAMEAT_SOURCE makes it possible to move files to a directory for
which file descriptors exist that have additional rights. For example, a file
stored in a directory that does not allow CAP_READ may be moved to another directory
that does allow CAP_READ, thereby granting read access to a file that is otherwise
unreadable.
CAP_RENAMEAT_TARGET Permit renameat(2) on the target 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 scope.
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 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. 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 required.
SEE 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)
HISTORY
Support for capabilities and capabilities mode was developed as part of the TrustedBSD Project.
AUTHORS
This manual page was created by Pawel Jakub Dawidek <pawel@dawidek.net> under sponsorship from the
FreeBSD Foundation based on the cap_new(2) manual page by Robert Watson <rwatson@FreeBSD.org>.
Debian February 28, 2019 RIGHTS(4)