bionic (1) capsh.1.gz

Provided by: libcap2-bin_2.25-1.2_amd64 bug

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).