1. Introduction
1.1 Who needs that
2. Principles
2.1 Non reversible isolation
2.2 Isolation areas
2.3 New system calls
2.4 Limiting super-user: The capabilities system
2.5 Enhancing the capability system
2.6 Playing with the new system calls
2.6.1 Playing with /usr/sbin/chcontext
2.6.2 Playing with /usr/sbin/chcontext as root
2.6.3 Playing with /usr/sbin/chbind
2.6.4 Playing with /usr/sbin/reducecap
2.7 Unification
3. Applications
3.1 Virtual server
3.2 Per user fire-wall
3.3 Secure server/Intrusion detection
3.4 Fail over servers
4. Installation
4.1 The packages
4.2 Setting a virtual server
4.3 Basic configuration of the virtual server
4.4 Entering the virtual server
4.5 Configuring the services
4.6 Starting/Stopping the virtual server
4.7 Starting/Stopping all the virtual servers
4.8 Restarting a virtual server from inside
4.9 Executing tasks at vserver start/stop time
4.10 Issues
4.11 How real is it ?
5. Features
6. Future directions
6.1 User controlled security box
6.2 Kernel enhancements
6.2.1 Per context disk quota
6.2.2 Global limits
6.2.3 Scheduler
6.2.4 Security issues
6.2.4.1 /dev/random
6.2.4.2 /dev/pts
6.2.4.3 Network devices
7. Alternative technologies
7.1 Virtual machines
7.2 Partitioning
7.3 Limitation of those technologies
8. Conclusion
9. Download
10. References
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2.6.4 Playing with /usr/sbin/reducecap

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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.
# 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

Using /usr/sbin/reducecap

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