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_FDCWDin 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_LOOKUPright. CAP_CHFLAGSAT- An alias to
CAP_FCHFLAGSandCAP_LOOKUP. CAP_CONNECT- When not in capabilities mode, permit
connect(2) and
connectat(2) with special value
AT_FDCWDin 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_LOOKUPright. CAP_CREATE- Permit openat(2) with the
O_CREATflag. 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_LOOKUPright is also present. CAP_FCHMOD- Permit fchmod(2) and
fchmodat(2) if the
CAP_LOOKUPright is also present. CAP_FCHMODAT- An alias to
CAP_FCHMODandCAP_LOOKUP. CAP_FCHOWN- Permit fchown(2) and
fchownat(2) if the
CAP_LOOKUPright is also present. CAP_FCHOWNAT- An alias to
CAP_FCHOWNandCAP_LOOKUP. CAP_FCNTL- Permit fcntl(2). Note that only the
F_GETFL,F_SETFL,F_GETOWNandF_SETOWNcommands 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_EXECflag;CAP_READis also required. CAP_FLOCK- Permit flock(2),
fcntl(2) (with
F_GETLK,F_SETLK,F_SETLKWorF_SETLK_REMOTEflag) and openat(2) (withO_EXLOCKorO_SHLOCKflag). 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_LOOKUPright is also present. CAP_FSTATAT- An alias to
CAP_FSTATandCAP_LOOKUP. CAP_FSTATFS- Permit fstatfs(2).
CAP_FSYNC- Permit
aio_fsync(2),
fdatasync(2),
fsync(2) and
openat(2) with
O_FSYNCorO_SYNCflag. CAP_FTRUNCATE- Permit
ftruncate(2) and
openat(2) with the
O_TRUNCflag. CAP_FUTIMES- Permit futimens(2) and
futimes(2), and permit
futimesat(2) and
utimensat(2) if the
CAP_LOOKUPright is also present. CAP_FUTIMESAT- An alias to
CAP_FUTIMESandCAP_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_CHANGEandCAP_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_EVENTis 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_LOOKUPright.Warning:
CAP_LINKAT_SOURCEmakes 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 allowCAP_READmay be linked in another directory that does allowCAP_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_LOOKUPright. 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_LOOKUPright. CAP_MKFIFOAT- Permit mkfifoat(2). This right includes the
CAP_LOOKUPright. CAP_MKNODAT- Permit mknodat(2). This right includes the
CAP_LOOKUPright. CAP_MMAP- Permit mmap(2) with the
PROT_NONEprotection. CAP_MMAP_R- Permit mmap(2) with the
PROT_READprotection. This right includes theCAP_READandCAP_SEEKrights. CAP_MMAP_RW- An alias to
CAP_MMAP_RandCAP_MMAP_W. CAP_MMAP_RWX- An alias to
CAP_MMAP_R,CAP_MMAP_WandCAP_MMAP_X. CAP_MMAP_RX- An alias to
CAP_MMAP_RandCAP_MMAP_X. CAP_MMAP_W- Permit mmap(2) with the
PROT_WRITEprotection. This right includes theCAP_WRITEandCAP_SEEKrights. CAP_MMAP_WX- An alias to
CAP_MMAP_WandCAP_MMAP_X. CAP_MMAP_X- Permit mmap(2) with the
PROT_EXECprotection. This right includes theCAP_SEEKright. 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_READandCAP_SEEK. CAP_PWRITE- An alias to
CAP_SEEKandCAP_WRITE. CAP_READ- Permit aio_read(2) (
CAP_SEEKis also required), openat(2) with theO_RDONLY flag,read(2), readv(2), recv(2), recvfrom(2), recvmsg(2), pread(2) (CAP_SEEKis also required), preadv(2) (CAP_SEEKis 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_LOOKUPright.Warning:
CAP_RENAMEAT_SOURCEmakes 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 allowCAP_READmay be moved to another directory that does allowCAP_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_LOOKUPright. 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_LOOKUPright. 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_LOOKUPright. CAP_WRITE- Allow
aio_write(2),
openat(2) with
O_WRONLYandO_APPENDflags 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_CONNECTis also required. For openat(2) with theO_WRONLYflag, but without theO_APPENDflag,CAP_SEEKis also required. For aio_write(2), pwrite(2) and pwritev(2)CAP_SEEKis 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>.