Capabilities - ArchWiki

# Capabilities

Capabilities (POSIX 1003.1e) provide fine-grained control over superuser permissions, allowing use of the root user to be avoided. A setuid binary can be replaced with a more minimal set of capabilities. Many packages make use of capabilities, such as CAP_NET_RAW being used for the `ping` and `ping6` binaries provided by iputils.

It is considered a bug if a package has overly permissive capabilities, so these cases should be reported rather than listed here. A capability essentially equivalent to root access (CAP_SYS_ADMIN) or trivially allowing root access (CAP_DAC_OVERRIDE) does not count as a bug since Arch does not support any MAC/RBAC systems.

Warning: Many capabilities enable trivial privilege escalation. For examples and explanations see Brad Spengler's post False Boundaries and Arbitrary Code Execution.

## Prerequisites

You need to install libcap, for setting file capabalities that are extended attributes, with the utility setcap.

## Other programs that benefit from capabilities

The following packages do not have files with the setuid attribute but require root privileges to work. By enabling some capabilities, regular users can use the program without privilege elevation.

### beep

    # setcap cap_dac_override,cap_sys_tty_config+ep /usr/bin/beep

### chvt

    # setcap cap_dac_read_search,cap_sys_tty_config+ep /usr/bin/chvt

### iftop

    # setcap cap_net_raw+ep /usr/bin/iftop

### mii-tool

    # setcap cap_net_admin+ep /usr/bin/mii-tool

## Useful commands

Find setuid-root files:

    $ find /usr/bin /usr/lib -perm /4000 -user root

Find setgid-root files:

    $ find /usr/bin /usr/lib -perm /2000 -group root

## See also

- Man Page capabilities(7) setcap(8) getcap(8)
- DeveloperWiki:Security#Replacing_setuid_with_capabilities

Category:

- Security