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 features useful for  summa-
       rizing 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 capabilites are a comma sepa-
                             rated 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 set-
                             groups(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  exam-
                             ple, 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 <morganATkernel.org>.

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)