.\"
.\" Copyright (c) 2008-2010 Robert N. M. Watson
.\" Copyright (c) 2012-2013 The FreeBSD Foundation
.\" All rights reserved.
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.\" This software was developed at the University of Cambridge Computer
.\" Laboratory with support from a grant from Google, Inc.
.\"
.\" Portions of this documentation were written by Pawel Jakub Dawidek
.\" under sponsorship from the FreeBSD Foundation.
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.Dd April 27, 2024
.Dt RIGHTS 4
.Os
.Sh NAME
.Nm Capability rights
.Nd Capsicum capability rights for file descriptors
.Sh DESCRIPTION
When a file descriptor is created by a function such as
.Xr fhopen 2 ,
.Xr kqueue 2 ,
.Xr mq_open 2 ,
.Xr open 2 ,
.Xr pdfork 2 ,
.Xr pipe 2 ,
.Xr shm_open 2 ,
.Xr socket 2
or
.Xr socketpair 2 ,
it is assigned all capability rights; for
.Xr accept 2 ,
.Xr accept4 2
or
.Xr openat 2 ,
it inherits capability rights from the "parent" file descriptor.
Those rights can be reduced (but never expanded) by using the
.Xr cap_rights_limit 2 ,
.Xr cap_fcntls_limit 2 and
.Xr cap_ioctls_limit 2
system calls.
Once capability rights are reduced, operations on the file descriptor will be
limited to those permitted by rights.
.Pp
The complete list of capability rights is provided below.
The
.Vt cap_rights_t
type is used to store list of capability rights.
The
.Xr cap_rights_init 3
family of functions should be used to manage the structure.
.Sh RIGHTS
Note that rights are not simple bitmasks (and cannot be bitwise-ORed together).
See
.Xr cap_rights_init 3
for details.
.Pp
The following rights are available:
.Bl -tag -width CAP_RENAMEAT_SOURCE
.It Dv CAP_ACCEPT
Permit
.Xr accept 2
and
.Xr accept4 2 .
.It Dv CAP_ACL_CHECK
Permit
.Xr acl_valid_fd_np 3 .
.It Dv CAP_ACL_DELETE
Permit
.Xr acl_delete_fd_np 3 .
.It Dv CAP_ACL_GET
Permit
.Xr acl_get_fd 3
and
.Xr acl_get_fd_np 3 .
.It Dv CAP_ACL_SET
Permit
.Xr acl_set_fd 3
and
.Xr acl_set_fd_np 3 .
.It Dv CAP_BIND
When not in capabilities mode, permit
.Xr bind 2
and
.Xr bindat 2
with special value
.Dv AT_FDCWD
in the
.Fa fd
parameter.
Note that sockets can also become bound implicitly as a result of
.Xr connect 2
or
.Xr send 2 ,
and that socket options set with
.Xr setsockopt 2
may also affect binding behavior.
.It Dv CAP_BINDAT
Permit
.Xr bindat 2 .
This right has to be present on the directory descriptor.
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_CHFLAGSAT
An alias to
.Dv CAP_FCHFLAGS
and
.Dv CAP_LOOKUP .
.It Dv CAP_CONNECT
When not in capabilities mode, permit
.Xr connect 2
and
.Xr connectat 2
with special value
.Dv AT_FDCWD
in the
.Fa fd
parameter.
This right is also required for
.Xr sendto 2
with a non-NULL destination address.
.It Dv CAP_CONNECTAT
Permit
.Xr connectat 2 .
This right has to be present on the directory descriptor.
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_CREATE
Permit
.Xr openat 2
with the
.Dv O_CREAT
flag.
.It Dv CAP_EVENT
Permit
.Xr select 2 ,
.Xr poll 2 ,
and
.Xr kevent 2
to be used in monitoring the file descriptor for events.
.It Dv CAP_EXTATTR_DELETE
Permit
.Xr extattr_delete_fd 2 .
.It Dv CAP_EXTATTR_GET
Permit
.Xr extattr_get_fd 2 .
.It Dv CAP_EXTATTR_LIST
Permit
.Xr extattr_list_fd 2 .
.It Dv CAP_EXTATTR_SET
Permit
.Xr extattr_set_fd 2 .
.It Dv CAP_FCHDIR
Permit
.Xr fchdir 2 .
.It Dv CAP_FCHFLAGS
Permit
.Xr fchflags 2
and
.Xr chflagsat 2
if the
.Dv CAP_LOOKUP
right is also present.
.It Dv CAP_FCHMOD
Permit
.Xr fchmod 2
and
.Xr fchmodat 2
if the
.Dv CAP_LOOKUP
right is also present.
.It Dv CAP_FCHMODAT
An alias to
.Dv CAP_FCHMOD
and
.Dv CAP_LOOKUP .
.It Dv CAP_FCHOWN
Permit
.Xr fchown 2
and
.Xr fchownat 2
if the
.Dv CAP_LOOKUP
right is also present.
.It Dv CAP_FCHOWNAT
An alias to
.Dv CAP_FCHOWN
and
.Dv CAP_LOOKUP .
.It Dv CAP_FCNTL
Permit
.Xr fcntl 2 .
Note that only the
.Dv F_GETFL ,
.Dv F_SETFL ,
.Dv F_GETOWN
and
.Dv F_SETOWN
commands require this capability right.
Also note that the list of permitted commands can be further limited with the
.Xr cap_fcntls_limit 2
system call.
.It Dv CAP_FEXECVE
Permit
.Xr fexecve 2
and
.Xr openat 2
with the
.Dv O_EXEC
flag;
.Dv CAP_READ
is also required.
.It Dv CAP_FLOCK
Permit
.Xr flock 2 ,
.Xr fcntl 2
(with
.Dv F_GETLK ,
.Dv F_SETLK ,
.Dv F_SETLKW
or
.Dv F_SETLK_REMOTE
flag) and
.Xr openat 2
(with
.Dv O_EXLOCK
or
.Dv O_SHLOCK
flag).
.It Dv CAP_FPATHCONF
Permit
.Xr fpathconf 2 .
.It Dv CAP_FSCK
Permit UFS background-fsck operations on the descriptor.
.It Dv CAP_FSTAT
Permit
.Xr fstat 2
and
.Xr fstatat 2
if the
.Dv CAP_LOOKUP
right is also present.
.It Dv CAP_FSTATAT
An alias to
.Dv CAP_FSTAT
and
.Dv CAP_LOOKUP .
.It Dv CAP_FSTATFS
Permit
.Xr fstatfs 2 .
.It Dv CAP_FSYNC
Permit
.Xr aio_fsync 2 ,
.Xr fdatasync 2 ,
.Xr fsync 2
and
.Xr openat 2
with
.Dv O_FSYNC
or
.Dv O_SYNC
flag.
.It Dv CAP_FTRUNCATE
Permit
.Xr ftruncate 2
and
.Xr openat 2
with the
.Dv O_TRUNC
flag.
.It Dv CAP_FUTIMES
Permit
.Xr futimens 2
and
.Xr futimes 2 ,
and permit
.Xr futimesat 2
and
.Xr utimensat 2
if the
.Dv CAP_LOOKUP
right is also present.
.It Dv CAP_FUTIMESAT
An alias to
.Dv CAP_FUTIMES
and
.Dv CAP_LOOKUP .
.It Dv CAP_GETPEERNAME
Permit
.Xr getpeername 2 .
.It Dv CAP_GETSOCKNAME
Permit
.Xr getsockname 2 .
.It Dv CAP_GETSOCKOPT
Permit
.Xr getsockopt 2 .
.It Dv CAP_IOCTL
Permit
.Xr 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
.Xr cap_ioctls_limit 2
system call.
.It Dv CAP_KQUEUE
An alias to
.Dv CAP_KQUEUE_CHANGE
and
.Dv CAP_KQUEUE_EVENT .
.It Dv CAP_KQUEUE_CHANGE
Permit
.Xr kevent 2
on a
.Xr kqueue 2
descriptor that modifies list of monitored events (the
.Fa changelist
argument is non-NULL).
.It Dv CAP_KQUEUE_EVENT
Permit
.Xr kevent 2
on a
.Xr kqueue 2
descriptor that monitors events (the
.Fa eventlist
argument is non-NULL).
.Dv CAP_EVENT
is also required on file descriptors that will be monitored using
.Xr kevent 2 .
.It Dv CAP_LINKAT_SOURCE
Permit
.Xr linkat 2
on the source directory descriptor.
This right includes the
.Dv CAP_LOOKUP
right.
.Pp
Warning:
.Dv 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
.Dv CAP_READ
may be linked in another directory that does allow
.Dv CAP_READ ,
thereby granting read access to a file that is otherwise unreadable.
.It Dv CAP_LINKAT_TARGET
Permit
.Xr linkat 2
on the target directory descriptor.
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_LISTEN
Permit
.Xr listen 2 ;
not much use (generally) without
.Dv CAP_BIND .
.It Dv CAP_LOOKUP
Permit the file descriptor to be used as a starting directory for calls such as
.Xr linkat 2 ,
.Xr openat 2 ,
and
.Xr unlinkat 2 .
.It Dv CAP_MAC_GET
Permit
.Xr mac_get_fd 3 .
.It Dv CAP_MAC_SET
Permit
.Xr mac_set_fd 3 .
.It Dv CAP_MKDIRAT
Permit
.Xr mkdirat 2 .
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_MKFIFOAT
Permit
.Xr mkfifoat 2 .
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_MKNODAT
Permit
.Xr mknodat 2 .
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_MMAP
Permit
.Xr mmap 2
with the
.Dv PROT_NONE
protection.
.It Dv CAP_MMAP_R
Permit
.Xr mmap 2
with the
.Dv PROT_READ
protection.
This right includes the
.Dv CAP_READ
and
.Dv CAP_SEEK
rights.
.It Dv CAP_MMAP_RW
An alias to
.Dv CAP_MMAP_R
and
.Dv CAP_MMAP_W .
.It Dv CAP_MMAP_RWX
An alias to
.Dv CAP_MMAP_R ,
.Dv CAP_MMAP_W
and
.Dv CAP_MMAP_X .
.It Dv CAP_MMAP_RX
An alias to
.Dv CAP_MMAP_R
and
.Dv CAP_MMAP_X .
.It Dv CAP_MMAP_W
Permit
.Xr mmap 2
with the
.Dv PROT_WRITE
protection.
This right includes the
.Dv CAP_WRITE
and
.Dv CAP_SEEK
rights.
.It Dv CAP_MMAP_WX
An alias to
.Dv CAP_MMAP_W
and
.Dv CAP_MMAP_X .
.It Dv CAP_MMAP_X
Permit
.Xr mmap 2
with the
.Dv PROT_EXEC
protection.
This right includes the
.Dv CAP_SEEK
right.
.It Dv CAP_PDGETPID
Permit
.Xr pdgetpid 2 .
.It Dv CAP_PDKILL
Permit
.Xr pdkill 2 .
.It Dv CAP_PEELOFF
Permit
.Xr sctp_peeloff 2 .
.It Dv CAP_PREAD
An alias to
.Dv CAP_READ
and
.Dv CAP_SEEK .
.It Dv CAP_PWRITE
An alias to
.Dv CAP_SEEK
and
.Dv CAP_WRITE .
.It Dv CAP_READ
Permit
.Xr aio_read 2
.Dv ( CAP_SEEK
is also required),
.Xr openat 2
with the
.Dv O_RDONLY flag,
.Xr read 2 ,
.Xr readv 2 ,
.Xr recv 2 ,
.Xr recvfrom 2 ,
.Xr recvmsg 2 ,
.Xr pread 2
.Dv ( CAP_SEEK
is also required),
.Xr preadv 2
.Dv ( CAP_SEEK
is also required),
.Xr getdents 2 ,
.Xr getdirentries 2 ,
and related system calls.
.It Dv CAP_RECV
An alias to
.Dv CAP_READ .
.It Dv CAP_RENAMEAT_SOURCE
Permit
.Xr renameat 2
on the source directory descriptor.
This right includes the
.Dv CAP_LOOKUP
right.
.Pp
Warning:
.Dv 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
.Dv CAP_READ
may be moved to another directory that does allow
.Dv CAP_READ ,
thereby granting read access to a file that is otherwise unreadable.
.It Dv CAP_RENAMEAT_TARGET
Permit
.Xr renameat 2
on the target directory descriptor.
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_SEEK
Permit operations that seek on the file descriptor, such as
.Xr lseek 2 ,
but also required for I/O system calls that can read or write at any position
in the file, such as
.Xr pread 2
and
.Xr pwrite 2 .
.It Dv CAP_SEM_GETVALUE
Permit
.Xr sem_getvalue 3 .
.It Dv CAP_SEM_POST
Permit
.Xr sem_post 3 .
.It Dv CAP_SEM_WAIT
Permit
.Xr sem_wait 3
and
.Xr sem_trywait 3 .
.It Dv CAP_SEND
An alias to
.Dv CAP_WRITE .
.It Dv CAP_SETSOCKOPT
Permit
.Xr setsockopt 2 ;
this controls various aspects of socket behavior and may affect binding,
connecting, and other behaviors with global scope.
.It Dv CAP_SHUTDOWN
Permit explicit
.Xr shutdown 2 ;
closing the socket will also generally shut down any connections on it.
.It Dv CAP_SYMLINKAT
Permit
.Xr symlinkat 2 .
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_TTYHOOK
Allow configuration of TTY hooks, such as
.Xr snp 4 ,
on the file descriptor.
.It Dv CAP_UNLINKAT
Permit
.Xr unlinkat 2
and
.Xr renameat 2 .
This right is only required for
.Xr renameat 2
on the destination directory descriptor if the destination object already
exists and will be removed by the rename.
This right includes the
.Dv CAP_LOOKUP
right.
.It Dv CAP_WRITE
Allow
.Xr aio_write 2 ,
.Xr openat 2
with
.Dv O_WRONLY
and
.Dv O_APPEND
flags set,
.Xr send 2 ,
.Xr sendmsg 2 ,
.Xr sendto 2 ,
.Xr write 2 ,
.Xr writev 2 ,
.Xr pwrite 2 ,
.Xr pwritev 2
and related system calls.
For
.Xr sendto 2
with a non-NULL connection address,
.Dv CAP_CONNECT
is also required.
For
.Xr openat 2
with the
.Dv O_WRONLY
flag, but without the
.Dv O_APPEND
or
.Dv O_TRUNC
flag,
.Dv CAP_SEEK
is also required.
For
.Xr aio_write 2 ,
.Xr pwrite 2
and
.Xr pwritev 2
.Dv CAP_SEEK
is also required.
.El
.Sh SEE ALSO
.Xr accept 2 ,
.Xr accept4 2 ,
.Xr aio_fsync 2 ,
.Xr aio_read 2 ,
.Xr aio_write 2 ,
.Xr bind 2 ,
.Xr bindat 2 ,
.Xr cap_enter 2 ,
.Xr cap_fcntls_limit 2 ,
.Xr cap_ioctls_limit 2 ,
.Xr cap_rights_limit 2 ,
.Xr chflagsat 2 ,
.Xr connect 2 ,
.Xr connectat 2 ,
.Xr extattr_delete_fd 2 ,
.Xr extattr_get_fd 2 ,
.Xr extattr_list_fd 2 ,
.Xr extattr_set_fd 2 ,
.Xr fchflags 2 ,
.Xr fchmod 2 ,
.Xr fchmodat 2 ,
.Xr fchown 2 ,
.Xr fchownat 2 ,
.Xr fcntl 2 ,
.Xr fexecve 2 ,
.Xr fhopen 2 ,
.Xr flock 2 ,
.Xr fpathconf 2 ,
.Xr fstat 2 ,
.Xr fstatat 2 ,
.Xr fstatfs 2 ,
.Xr fsync 2 ,
.Xr ftruncate 2 ,
.Xr futimes 2 ,
.Xr getdents 2 ,
.Xr getdirentries 2 ,
.Xr getpeername 2 ,
.Xr getsockname 2 ,
.Xr getsockopt 2 ,
.Xr ioctl 2 ,
.Xr kevent 2 ,
.Xr kqueue 2 ,
.Xr linkat 2 ,
.Xr listen 2 ,
.Xr mmap 2 ,
.Xr mq_open 2 ,
.Xr open 2 ,
.Xr openat 2 ,
.Xr pdfork 2 ,
.Xr pdgetpid 2 ,
.Xr pdkill 2 ,
.Xr pdwait4 2 ,
.Xr pipe 2 ,
.Xr poll 2 ,
.Xr pread 2 ,
.Xr preadv 2 ,
.Xr pwrite 2 ,
.Xr pwritev 2 ,
.Xr read 2 ,
.Xr readv 2 ,
.Xr recv 2 ,
.Xr recvfrom 2 ,
.Xr recvmsg 2 ,
.Xr renameat 2 ,
.Xr sctp_peeloff 2 ,
.Xr select 2 ,
.Xr send 2 ,
.Xr sendmsg 2 ,
.Xr sendto 2 ,
.Xr setsockopt 2 ,
.Xr shm_open 2 ,
.Xr shutdown 2 ,
.Xr socket 2 ,
.Xr socketpair 2 ,
.Xr symlinkat 2 ,
.Xr unlinkat 2 ,
.Xr write 2 ,
.Xr writev 2 ,
.Xr acl_delete_fd_np 3 ,
.Xr acl_get_fd 3 ,
.Xr acl_get_fd_np 3 ,
.Xr acl_set_fd 3 ,
.Xr acl_set_fd_np 3 ,
.Xr acl_valid_fd_np 3 ,
.Xr mac_get_fd 3 ,
.Xr mac_set_fd 3 ,
.Xr sem_getvalue 3 ,
.Xr sem_post 3 ,
.Xr sem_trywait 3 ,
.Xr sem_wait 3 ,
.Xr capsicum 4 ,
.Xr snp 4
.Sh HISTORY
Support for capabilities and capabilities mode was developed as part of the
.Tn TrustedBSD
Project.
.Sh AUTHORS
.An -nosplit
This manual page was created by
.An Pawel Jakub Dawidek Aq Mt pawel@dawidek.net
under sponsorship from the FreeBSD Foundation based on the
.Xr cap_new 2
manual page by
.An Robert Watson Aq Mt rwatson@FreeBSD.org .