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.