Having switched to Nginx a while ago, I was recently asked to use Apache for a client installation. There have been some significant changes in 2.4 from 2.2, include the 'Requires' option. I also wanted to create a virtualhost entry for Munin on this machine. It took a little while to figure this out, in particular on Apache 2.4. I'm also using the built-in cron task to generate graphs.
For a little while now I've wanted to be able to chroot both SFTP and SHH accounts on one of my multi-user VPSs.
SFTP on its own is not so difficult. OpenSSH 4.9p1 and above includes the ChrootDirectory directive. And an SFTP chroot is a little more forgiving in so far as it doesn't actually require any supporting system or userpsace services (a shell, ls, cp, etc.), which is why you often see ChrootDirectory accompanied with
ForceCommand internal-sftp which will prevent SSH access altogether.
What I'd like to do is create a restricted environment for both SSH and SFTP.
I spent a little while looking at a very interesting project from Olivier Sessink called Jailkit. Jailkit has most of what I was looking for but, it has quite a few moving parts, including the need to replace a users shell with a special Jailkit shim that hands over to Jailkit. This is okay but it means changes to passwd are required, and editing your
/etc/ssh/sshd_config to use
Subsystem sftp /usr/lib/openssh/sftp-server and not
Subsystem sftp internal-sftp if you want to chroot and jail both SFTP and SHH logins.
It turns out that OpenSSH gets us most of the way there with the ChrootDirectory directive.
And so here are the steps required to create a minimal chroot jail on Ubuntu 12.04 LTS.
I recently suffered a UDP flood attack on my little virtual private server (VPS) and thought I'd describe the steps I went through to discover and fix the problem.
Periodically, my server would stall and become unresponsive. It was effectively dead, although not down. These 'stalling' events would last from 5-20 minutes, and then the server would come back up. Looking at my Munin charts told me that my public ethernet interface (eth0) was being flooded. Here's a particularly bad day: