Ubuntu Manpage: reducecap - The reducecap utility is used to lower the capability ceiling of a process and

Provided by: util-vserver_0.30.216-pre3120-1.4_amd64

NAME

       reducecap - The reducecap utility is used to lower the capability ceiling of a process and
       child process.

SYNTAX

       reducecap [options] <command arguments>

DESCRIPTION

       The reducecap utility is used to lower the capability  ceiling  of  a  process  and  child
       process. Even setuid program won't be able to grab more capabilities.

OPTIONS

--secure Removes all dangerous capabilities from the process executed.Specificly it
removes:
CAP_LINUX_IMMUTABLE CAP_NET_BROADCAST CAP_NET_ADMIN, CAP_NET_RAW CAP_IPC_LOCK
CAP_IPC_OWNER CAP_SYS_MODULE CAP_SYS_RAWIO CAP_SYS_PACCT CAP_SYS_ADMIN CAP_SYS_BOOT
CAP_SYS_NICE CAP_SYS_RESOURCE CAP_SYS_TIME CAP_MKNOD.

Leaving the following capabilities: CAP_CHOWN CAP_DAC_OVERRIDE CAP_DAC_READ_SEARCH
CAP_FOWNER CAP_FSETID CAP_KILL CAP_SETGID CAP_SETUID CAP_NET_BIND_SERVICE
CAP_SYS_CHROOT CAP_SYS_PTRACE CAP_SYS_TTY_CONFIG CAP_LEASE CAP_QUOTACTL

--show Shows the current process capabilities.

--flag sets the security context flags. The option may be repeated several times. Here are
the values:

lock: The security context can't be changed. The process is trapped in this
context. This is generally used for vservers because yoy do not want them to
hide in new security context.

sched: Each process in a security context contribute (lower) to the general
priority of every processes in the context. Mostly, all processes in a
security context take as much CPU together as one process not bound to this
flag. Said again differently, a vserver having 100 active processes won't get
more CPU than another vserver with a single active process.

nproc: The "ulimit -u N" setting becomes global to the security context. It means
the security context is not allowed to have more than N processes.

private: No other processes, even root in security context 0, is allowed to
enter this security context. Once a security context is setup with this
flag, it is on its own. This also means that root in security context 0 won't
be able to kill or interact with those processes.

hideinfo: Hides various information in /proc.

--LINUX_IMMUTABLE

--NET_BIND_SERVICE

--NET_BROADCAST

--NET_ADMIN

--NET_RAW

--IPC_LOCK

--IPC_OWNER

--SYS_MODULE

--SYS_RAWIO

--SYS_PACCT

--SYS_ADMIN

--SYS_BOOT

--SYS_NICE

--SYS_RESOURCE

--SYS_TIME

--MKNOD

All these options remove one capability. These options may be used after the
--secure option to remove more capabilities.

FILES

       /usr/sbin/reducecap

EXAMPLES

       # You are not root now # What is the current capability ceiling  cat  /proc/self/status  #
       The   capBset   line   presents  mostly  1s.   /usr/sbin/reducecap  --secure  /bin/sh  cat
       /proc/self/status # The capBset now shows many more 0s.  # The capEff shows  all  0s,  you
       have  no  privilege  now  # We su to root su cat /proc/self/status # capEff is much better
       now, but there are still many 0s #  Now  we  try  to  see  if  we  are  really  root  tail
       /var/log/messages  # So far so good, we see the content /sbin/ifconfig eth0 /sbin/ifconfig
       eth0 down # No way, we can't configure  the  interface.  In  fact  #  we  have  lost  most
       privilege normally assigned to root exit

       Please contribute some more, if you feel it's important.

AUTHORS

       This  Man page was written by Klavs Klavsen <kl@vsen.dk> and based upon the helpful output
       from  the  program  itself  and   the   documentation   on   the   Virtual   Server   site
       <http://www.solucorp.qc.ca/miscprj/s_context.hc?prjstate=1&nodoc=0>