Provided by: libcap2-bin_2.66-4ubuntu1_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

       capsh takes a number of optional arguments, acting on them in the order they are provided.
       They are as follows:

       --help Display the list of commands supported by capsh.

       --print
              Display prevailing capability and related state.

       --current
              Display prevailing capability state, 1e capabilities and IAB vector.

       -- [args]
              Execute /bin/bash with trailing  arguments.  Note,  you  can  use  -c  'command  to
              execute' for specific commands.

       -+ [args]
              Uses  cap_launch(3)  to  fork  a  child to execute the shell. When the child exits,
              capsh exits with the status of the child or 1  in  the  case  that  the  child  was
              terminated by a signal.

       == [args]
              Execute  capsh  again  with  the  remaining  arguments.  Useful  for testing exec()
              behavior. Note, PATH is searched when the running capsh was found via  the  shell's
              PATH  searching.  If  the exec occurs after a --chroot=/some/path argument the PATH
              located binary may not be resolve to the same binary  as  that  running  initially.
              This behavior is an intended feature as it can complete the chroot transition.

       =+ [args]
              Uses  cap_launch(3)  to  fork  a  child to re-execute capsh. When this child exits,
              capsh exits with the status of the child or 1  in  the  case  that  the  child  was
              terminated by a signal.

       --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 capsh 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  capsh  should  be  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 using
              cap_setuid(3)   and   cap_setgroups(3).   Following  this  command,  the  effective
              capabilities will be cleared, but the permitted set will not  be,  so  the  running
              program is still privileged.

       --mode Display the prevailing libcap mode as guessed by the cap_get_mode(3) function.

       --mode=<mode>
              Force the program into a cap_set_mode(3) security mode. This is a set of securebits
              and prevailing capability arrangement recommended for its  pre-determined  security
              stance.

       --modes
              Lists all of the libcap modes supported by --mode=<mode>.

       --inmode=<mode>
              Confirm that the prevailing mode is that specified in <mode>, or exit with a status
              1.

       --uid=id
              Force all UID values to equal id using the setuid(2) system call. This argument may
              require explicit preparation of the effective set.

       --cap-uid=<uid>
              use the cap_setuid(3) function to set the UID of the current process. This performs
              all preparations for setting the UID without dropping capabilities in the  process.
              Following this command the prevailing effective capabilities will be lowered.

       --is-uid=<id>
              Exit with status 1 unless the current UID equals <id>.

       --gid=<id>
              Force all GID values to equal id using the setgid(2) system call.

       --is-gid=<id>
              Exit with status 1 unless the current GIQ equals <id>.

       --groups=<gid-list>
              Set  the  supplementary  groups  to the numerical list provided. The groups are set
              with the setgroups(2) system call. See --user for a more convenient  way  of  doing
              this.

       --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 program 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 --secbitsand--mode
              for ways to disable this feature.

       --secbits=N
              Set   the  security-bits  for  the  program.   This  is  done  using  the  prctl(2)
              PR_SET_SECUREBITS operation.  The list of supported bits and their meaning  can  be
              found  in the <sys/secbits.h> header file. The program will list these bits via the
              --print command.  The argument is expressed as a numeric bitmask,  in  any  of  the
              formats  permitted by strtoul(3).  An alternative to this bit-twiddling is embedded
              in the --mode* commandline arguments.

       --chroot=/some/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
              This  command  causes  the program to fork a child process for so many seconds. The
              child will sleep that long and then exit with status 0. The purpose of this command
              is  to  support  exploring the way processes are killable in the face of capability
              changes. See the --killit command. Only one fork can be active at a time.

       --killit=sig
              This commands causes a --forkfor child to be kill(2)d with  the  specified  signal.
              The  command  then  waits for the child to exit.  If the exit status does not match
              the signal being used to kill it, the capsh program exits with status 1.

       --explain=cap_xxx
              Give a brief textual description of what privileges the specified capability  makes
              available to a running program. Note, instead of cap_xxx, one can provide a decimal
              number and capsh will look up the corresponding capability's description.

       --shell=/full/path
              This option changes the shell that is invoked when the argument == is encountered.

       --strict
              This option toggles the suppression of subsequent attempts  to  fixup  --caps=  and
              --inh=  arguments.  That  is,  when  the prevailing Effective flag does not contain
              CAP_SETPCAP the to be raised Inheritable Flag values (in strict mode)  are  limited
              to  those  in  the  Permitted  set. The strict mode defaults to off. Supplying this
              argument an even number of times restores this default behavior.

       --suggest=phrase
              Scan each of the textual descriptions of capabilities, known to capsh, and  display
              all descriptions that include phrase.

       --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:   0000003fffffffff
              CapEff:   0000003fffffffff
              CapBnd:   0000003fffffffff
              CapAmb:   0000000000000000

              This option provides a quick way to decode a capability vector represented in  this
              hexadecimal form.  Here's an example that decodes the two lowest capability bits:

              $ capsh --decode=3
              0x0000000000000003=cap_chown,cap_dac_override

       --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.

       --has-p=xxx
              Exit with status 1 unless the permitted vector has capability xxx raised.

       --has-ambient
              Performs a check to see if the running kernel  supports  ambient  capabilities.  If
              not, capsh exits with status 1.

       --has-a=xxx
              Exit with status 1 unless the ambient vector has capability xxx raised.

       --has-b=xxx
              Exit  with  status 1 unless the bounding vector has capability xxx in its (default)
              non-blocked state.

       --iab=xxx
              Attempts to set  the  IAB  tuple  of  inheritable  capability  vectors.   The  text
              conventions used for xxx are those of cap_iab_from_text(3).

       --addamb=xxx
              Adds the specified ambient capability to the running process.

       --delamb=xxx
              Removes the specified ambient capability from the running process.

       --noamb
              Drops all ambient capabilities from the running process.

       --noenv
              Suppresses  overriding of the HOME and USER environment variables when a subsequent
              --user argument is processed.

       --quiet
              This argument is ignored unless it is the first one. If present, it suppresses  the
              capsh runtime check to confirm the running libcap is recent enough that it can name
              all of the kernel supported capability values.

EXIT STATUS

       Following successful execution, capsh exits with  status  0.  Following  an  error,  capsh
       immediately exits with status 1.

AUTHOR

       Written by Andrew G. Morgan <morgan@kernel.org>.

REPORTING BUGS

       Please report bugs via:

       https://bugzilla.kernel.org/buglist.cgi?component=libcap&list_id=1090757

SEE ALSO

       libcap(3),    cap_from_text(3),   cap_iab(3)   capabilities(7),   captree(8),   getcap(8),
       getpcaps(8), and setcap(8).