CAPSH(1) User Commands CAPSH(1)
NAME
capsh - capability shell wrapper
SYNOPSIS
capsh [OPTION]...
DESCRIPTION
Linux capability support and use can be explored and constrained with this tool. This tool provides a handy
wrapper for certain types of capability testing and environment creation. It also provides some debugging fea‐
tures useful for summarizing capability state.
OPTIONS
The tool takes a number of optional arguments, acting on them in the order they are provided. They are as fol‐
lows:
--print Display prevailing capability and related state.
-- [args] Execute /bin/bash with trailing arguments. Note, you can use -c 'command to execute' for
specific commands.
== Execute capsh again with remaining arguments. Useful for testing exec() behavior.
--caps=cap-set Set the prevailing process capabilities to those specified by cap-set. Where cap-set is
a text-representation of capability state as per cap_from_text(3).
--drop=cap-list Remove the listed capabilities from the prevailing bounding set. The capabilites are a
comma separated list of capabilities as recognized by the cap_from_name(3) function. Use
of this feature requires that the capsh program is operating with CAP_SETPCAP in its
effective set.
--inh=cap-list Set the inheritable set of capabilities for the current process to equal those provided
in the comma separated list. For this action to succeed, the prevailing process should
already have each of these capabilities in the union of the current inheritable and per‐
mitted capability sets, or the capsh program is operating with CAP_SETPCAP in its effec‐
tive set.
--user=username Assume the identity of the named user. That is, look up the user's uid and gid with get‐
pwuid(3) and their group memberships with getgrouplist(3) and set them all.
--uid=id Force all uid values to equal id using the setuid(2) system call.
--gid=<id> Force all gid values to equal id using the setgid(2) system call.
--groups=<id-list> Set the supplementary groups to the numerical list provided. The groups are set with the
setgroups(2) system call.
--keep=<0|1> In a non-pure capability mode, the kernel provides liberal privilege to the super-user.
However, it is normally the case that when the super-user changes uid to some lesser
user, then capabilities are dropped. For these situations, the kernel can permit the
process to retain its capabilities after a setuid(2) system call. This feature is known
as keep-caps support. The way to activate it using this script is with this argument.
Setting the value to 1 will cause keep-caps to be active. Setting it to 0 will cause
keep-caps to deactivate for the current process. In all cases, keep-caps is deactivated
when an exec() is performed. See --secbits for ways to disable this feature.
--secbits=N XXX - need to document this feature.
CapPrm: ffffffffffffffff
CapEff: fffffffffffffeff
CapBnd: ffffffffffffffff
This option provides a quick way to decode a capability vector represented in this form.
For example, the missing capability from this effective set is 0x0100. By running:
capsh --decode=0x0100
we observe that the missing capability is: cap_setpcap.
--supports=xxx As the kernel evolves, more capabilities are added. This option can be used to verify
the existence of a capability on the system. For example, --supports=cap_syslog will
cause capsh to promptly exit with a status of 1 when run on kernel 2.6.27. However,
when run on kernel 2.6.38 it will silently succeed.
EXIT STATUS
Following successful execution the tool exits with status 0. Following an error, the tool immediately
exits with status 1.
AUTHOR
Written by Andrew G. Morgan <[email protected]>.
REPORTING BUGS
Please report bugs to the author.
SEE ALSO
libcap(3), getcap(8),setcap(8) and capabilities(7).
libcap 2 2011-04-24 CAPSH(1)
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