Recently the Gentoo hardened project seems to have some serious bugs, particularly with the grsec kernel. I have been forced to switch to CentOS 6 and configure it to act similarly to Gentoo/grsec.
One of the biggest draws to grsec is the process hiding feature. CentOS 6 uses selinux and I decided to stay with it. Lucky for me, support for process hiding was added around kernel version 3.3.X
Mount /proc with the hidepid option.
I will show you the steps required to use hidepid with CentOS 6. These directions may not translate easily to other distributions of Linux.
Installing a Version 3.X.X Kernel
server ~ # wget http://elrepo.org/linux/kernel/el6/x86_64/RPMS/kernel-ml-3.5.0-2.el6.elrepo.x86_64.rpm server ~ # rpm -i kernel-ml-3.5.0-2.el6.elrepo.x86_64.rpm server ~ # new-kernel-pkg --mkinitrd --install --make-default --depmod 3.5.0-2.el6.elrepo.x86_64 server ~ # reboot
Figuring Out Where to Enable hidepid
hidepid is a mount option for /proc, but it seems that it does not work when added to /etc/fstab. Once you reboot, the system will clearly tell you /proc is mounted with hidepid but nothing happens. I've found that this feature does not work unless you remount /proc.
This might be a bug, so my instructions will be a workaround as opposed to a proper way to do it.
More About hidepid
hidepid comes in three settings:
- hidepid=0 - Disabled, no point in setting this
- hidepid=1 - Enabled, hides processes not belonging to the user, user can still learn processes VIA other means
- hidepid=2 - Enabled, hides processes not belonging to the user, user may not learn processes VIA other means
Find the following lines: if [ ! -e /proc/mounts ]; then mount -n -t proc /proc /proc mount -n -t sysfs /sys /sys >/dev/null 2>&1 fi Insert the following after 'fi': mount /proc -o remount,hidepid=2
Please be aware that adding the option to "mount -n -t proc /proc /proc" has not worked for me and only remounting works.
(psamp@test) (/home/psamp) $ ps aux USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND psamp 1366 0.0 0.0 108344 1868 pts/0 Ss+ 18:51 0:00 -bash psamp 1415 0.0 0.0 108344 1868 pts/1 Ss 19:29 0:00 -bash psamp 1477 0.0 0.0 110220 1144 pts/1 R+ 20:32 0:00 ps aux