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>.