Hardened/Overview of POSIX capabilities
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POSIX capabilities are a partitioning of the all powerful root privilege into a set of distinct privileges.
- 1 CAP_CHOWN
- 2 CAP_DAC_OVERRIDE
- 3 CAP_DAC_READ_SEARCH
- 4 CAP_FOWNER
- 5 CAP_FSETID
- 6 CAP_FS_MASK
- 7 CAP_KILL
- 8 CAP_SETGID
- 9 CAP_SETUID
- 10 CAP_SETPCAP
- 11 CAP_LINUX_IMMUTABLE
- 12 CAP_NET_BIND_SERVICE
- 13 CAP_NET_BROADCAST
- 14 CAP_NET_ADMIN
- 15 CAP_NET_RAW
- 16 CAP_IPC_LOCK
- 17 CAP_IPC_OWNER
- 18 CAP_SYS_MODULE
- 19 CAP_SYS_RAWIO
- 20 CAP_SYS_CHROOT
- 21 CAP_SYS_PTRACE
- 22 CAP_SYS_PACCT
- 23 CAP_SYS_ADMIN
- 24 CAP_SYS_BOOT
- 25 CAP_SYS_NICE
- 26 CAP_SYS_RESOURCE
- 27 CAP_SYS_TIME
- 28 CAP_SYS_TTY_CONFIG
- 29 CAP_MKNOD
- 30 CAP_LEASE
CAP_CHOWN In a system with the [_POSIX_CHOWN_RESTRICTED] option defined, this overrides the restriction of changing file ownership and group ownership.
CAP_DAC_OVERRIDE Override all DAC access, including ACL execute access if [_POSIX_ACL] is defined. Excluding DAC access covered by CAP_LINUX_IMMUTABLE.
CAP_DAC_READ_SEARCH Overrides all DAC restrictions, regarding read and search on files and directories, including ACL restrictions, if [_POSIX_ACL] is defined. Excluding DAC access covered by CAP_LINUX_IMMUTABLE.
CAP_FOWNER Overrides all restrictions about allowed operations on files, where file owner ID must be equal to the user ID, except where CAP_FSETID is applicable. It doesn't override MAC and DAC restrictions.
CAP_FSETID Overrides the following restrictions, that the effective user ID shall match the file owner ID, when setting the S_ISUID and S_ISGID bits on that file; that the effective group ID (or one of the supplementary group IDs) shall match the file owner ID when setting the S_ISGID bit on that file; that the S_ISUID and S_ISGID bits are cleared on successful return from chown(2) (not implemented).
CAP_FS_MASK Used to decide between falling back on the old suser() or fsuser().
CAP_KILL Overrides the restriction, that the real or effective user ID of a process, sending a signal, must match the real or effective user ID of the process, receiving the signal.
CAP_SETGID Allows setgid(2) manipulation; Allows setgroups(2); Allows forged gids on socket credentials passing.
CAP_SETUID Allows set*uid(2) manipulation (including fsuid); Allows forged pids on socket credentials passing.
CAP_SETPCAP Transfer any capability in your permitted set to any pid, remove any capability in your permitted set from any pid.
CAP_LINUX_IMMUTABLE Allow modification of S_IMMUTABLE and S_APPEND file attributes.
CAP_NET_BIND_SERVICE Allows binding to TCP/UDP sockets below 1024; Allows binding to ATM VCIs below 32.
CAP_NET_BROADCAST Allow broadcasting, listen to multicast.
CAP_NET_ADMIN Allow interface configuration; Allow administration of IP firewall, masquerading and accounting; Allow setting debug option on sockets; Allow modification of routing tables; Allow setting arbitrary process / process group ownership on sockets; Allow binding to any address for transparent proxying; Allow setting TOS (type of service); Allow setting promiscuous mode; Allow clearing driver statistics; Allow multicasting; Allow read/write of devicespecific registers; Allow activation of ATM control sockets.
CAP_NET_RAW Allow use of RAW sockets; Allow use of PACKET sockets.
CAP_IPC_LOCK Allow locking of shared memory segments; Allow mlock and mlockall (which doesn't really have anything to do with IPC).
CAP_IPC_OWNER Override IPC ownership checks.
CAP_SYS_MODULE Insert and remove kernel modules modify kernel without limit; Modify cap_bset.
CAP_SYS_RAWIO Allow ioperm/iopl access; Allow sending USB messages to any device via /proc/bus/usb.
CAP_SYS_CHROOT Allow use of chroot().
CAP_SYS_PTRACE Allow ptrace() of any process.
CAP_SYS_PACCT Allow configuration of process accounting.
CAP_SYS_ADMIN Allow configuration of the secure attention key; Allow administration of the random device; Allow examination and configuration of disk quotas; Allow configuring the kernel's syslog (printk behaviour); Allow setting the domainname; Allow setting the hostname; Allow calling bdflush(); Allow mount() and umount(), setting up new smb connection; Allow some autofs root ioctls; Allow nfsservctl; Allow VM86_REQUEST_IRQ; Allow to read/write pci config on alpha; Allow irix_prctl on mips (setstacksize); Allow flushing all cache on m68k (sys_cacheflush); Allow removing semaphores; Used instead of CAP_CHOWN to "chown" IPC message queues, semaphores and shared memory; Allow locking/unlocking of shared memory segment; Allow turning swap on/off; Allow forged pids on socket credentials passing; Allow setting readahead and flushing buffers on block devices; Allow setting geometry in floppy driver; Allow turning DMA on/off in xd driver; Allow administration of md devices (mostly the above, but some extra ioctls); Allow tuning the ide driver; Allow access to the nvram device; Allow administration of apm_bios, serial and bttv (TV) device; Allow manufacturer commands in isdn CAPI support driver; Allow reading nonstandardized portions of pci configuration space; Allow DDI debug ioctl on sbpcd driver; Allow setting up serial ports; Allow sending raw qic117 commands; Allow enabling/disabling tagged queuing on SCSI controllers and sending arbitrary SCSI commands; Allow setting encryption key on loopback filesystem.
CAP_SYS_BOOT Allow use of reboot().
CAP_SYS_NICE Allow raising priority and setting priority on other (different UID) processes; Allow use of FIFO and roundrobin (realtime) scheduling on own processes and setting the scheduling algorithm used by another process.
CAP_SYS_RESOURCE Override resource limits. Set resource limits; Override quota limits; Override reserved space on ext2 filesystem; Modify data journaling mode on ext3 filesystem (uses journaling resources); NOTE: ext2 honors fsuid when checking for resource overrides, so you can override using fsuid too; Override size restrictions on IPC message queues; Allow more than 64hz interrupts from the realtime clock; Override max number of consoles on console allocation; Override max number of keymaps.
CAP_SYS_TIME Allow manipulation of system clock; Allow irix_stime on mips; Allow setting the realtime clock.
CAP_SYS_TTY_CONFIG Allow configuration of tty devices; Allow vhangup() of tty.
CAP_MKNOD Allow the privileged aspects of mknod().
CAP_LEASE Allow taking of leases on files.
This article is based on a document formerly found on our main website gentoo.org.
The following people have contributed to the original document: Ned Ludd, Adam Mondl
They are listed here as the Wiki history does not provide for any attribution. If you edit the Wiki article, please do not add yourself here; your contributions are recorded on the history page.