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 features 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 follows:
--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 capabilities 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 permitted capability sets, or the
capsh program is operating with CAP_SETPCAP in
its effective set.
--user=username Assume the identity of the named user. That is,
look up the user's uid and gid with getpwuid(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.
--chroot=path Execute the chroot(2) system call with the new
root-directory (/) equal to path. This operation
requires CAP_SYS_CHROOT to be in effect.
--forkfor=sec
--killit=sig
--decode=N This is a convenience feature. If you look at
/proc/1/status there are some capability related
fields of the following form:
CapInh: 0000000000000000
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 <morgan@kernel.org>.
REPORTING BUGS
Please report bugs to the author.
SEE ALSO
libcap(3), getcap(8),setcap(8) and capabilities(7).
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