Securing /tmp Partition

If you are renting a server then chances are everything is lumped in / and a small amount partitioned for /boot and some for swap. With this current setup, you have no room for making more partitions unless you have a second hard-drive. Learn how to create a secure /tmp partition even while your server is already up and running.
Recently, I found out it would be worthwhile to give /tmp it’s own partition and mount it using noexec- This would protect your system from MANY local and remote exploits of rootkits being run from your /tmp folder.

What we are doing it creating a file that we will use to mount at /tmp. So log into SSH and SU to root so we may being!

code:

cd /dev

Create 100MB file for our /tmp partition. If you need more space, make count size larger.

code:

dd if=/dev/zero of=tmpMnt bs=1024 count=100000

Make an extended filesystem for our tmpMnt file

code:

/sbin/mke2fs /dev/tmpMnt

Backup your /tmp dir- I had mysql.sock file that I needed to recreate the symbolic link for. Other programs may use it to store cache files or whatever.

code:

cd /

code:

cp -R /tmp /tmp_backup

Mount the new /tmp filesystem with noexec

code:

mount -o loop,noexec,nosuid,rw /dev/tmpMnt /tmp

code:

chmod 1777 /tmp

Copy everything back to new /tmp and remove backup

code:

cp -R /tmp_backup/* /tmp/

code:

rm -rf /tmp_backup

Now we need to add this to fstab so it mounts automatically on reboots.

code:

pico -w /etc/fstab

You should see something like this:
code:
/dev/hda3 / ext3 defaults,usrquota 1 1
/dev/hda1 /boot ext3 defaults 1 2
none /dev/pts devpts gid=5,mode=620 0 0
none /proc proc defaults 0 0
none /dev/shm tmpfs defaults 0 0
/dev/hda2 swap swap defaults 0 0

At the bottom add
code:

/dev/tmpMnt /tmp ext2 loop,noexec,nosuid,rw 0 0

(Each space is a tab)
Save it!
Ctrl + X and Y

Your done- /tmp is now mounted as noexec. You can sleep a little bit safer tonight. I created a hello world c++ and compiled it then moved it to /tmp. Upon trying to run it (even chmod +x’ed), it gives the following error:

code:
bash: ./a.out: Permission denied