Escaping from a jail with root privileges on the host

[Marin Atanasov Nikolov]

Hello,

Today I've managed to escape from a jail by accident and ended up with
root access to the host's filesystem.

Here's what I did:

 * Using ezjail for managing my jails
 * Verified in FreeBSD 9.0-BETA3 and 9.0-RC3
 * This works only when I use sudo, and cannot reproduce if I execute
everything as root

First, created a folder *inside* the jail and cd to it:

 host$ sudo ezjail-admin console jail-test

 jail-test# id
 uid=0(root) gid=0(wheel) groups=0(wheel),5(operator)

 jail-test# mkdir ~/jail-folder
 jail-test# cd ~/jail-folder

 jail-test# pwd
 /root/jail-folder

Then from the host machine I've moved this folder to the cwd.

host$ pwd
/usr/home/mra

host$ sudo mv /home/jails/jail-test/root/jail-folder .

And then here's where the jail ends up :)

 jail-test# pwd
 /usr/home/mra/jail-folder

>From here on the Jail's root user has full root privileges to the
host's filesystem.

Not sure if it is sudo or jail issue, and would be nice if someone
with more experience can check this up :)

Regards,
Marin

-- 
Marin Atanasov Nikolov

dnaeon AT gmail DOT com
daemon AT unix-heaven DOT org
http://www.unix-heaven.org/