Wednesday, January 31, 2018

experimental debian rsyslog packages

We often receive requests for Debian packages. So far, we did not package for recent Debian, as the Debian maintainer, Michael Biebl, does an excellent job. Other than us, he is a real expert on Debian policies and infrastructure.

Nevertheless, we now took his package sources and gave the Suse Open Build Service a try. In the end result, we now seem to have usable Debian packages (and more) available at:


I would be very interested in your feedback on the first incarnation of this project. Is it useful? Is it something we should continue? Do you have any problems with the packages? Other suggestions? Please let us know.

Please node: should we decide that the project is worth keeping, the above URL will change. However, it we will give sufficiently advance notice. The current version is not suggested for production systems, at least not without trying it out on test-systems first!

Saturday, January 27, 2018

docker group security risk

The Docker doc spells out that there are security concerns of adding a user to the docker group. Unfortunately, they do not precisely give what the concern is. I guess that is a "security-by-obscurity" approach trying to avoid bad things. Practice show this isn't useful: the bad guys know anyways, and the casual user has a bad time understanding the actual risk involved.

It is considerable, so let me explain at least one risk (I have not tried exhaustively check security issues):  The containers are usually defined to run as root user. This permits you to bypass permission checks on the host.

Let’s assume a $USER is inside the docker group and otherwise has just installed docker. So he can run
$ docker run -v/etc:/malicious -ti --rm alpine
# cd /malicious
# vi sudoers
.... edit, write ...
# ctl-D
As such, the user can modify system config that he could not access otherwise. It’s a real risk. If you have a one-person “personal” machine/VM where the user has sudo permissions in any case … I’d say it’s no real issue.

The story is a different one on e.g. a CI machine.  It's easy to inject bad code into public pull requests, and so it'll run on the CI platform. Usually (before spectre/meltdown...), this was guarded by the (low) permissions of the CI worker user (if you run CI with a sudo-enabled user ... nothing changed). When you enable it to use docker, you now get this new class of attack vector. Don't get me wrong: I do NOT advocate against using docker in CI. Right the opposite, it's an excellent tool there. I just want to make you aware that you need to consider and mitigate another attack vector.

simplifying rsyslog JSON generation

With RESTful APIs, like for example ElasticSearch, you need to generate JSON strings. Rsyslog will soon do this in a very easy to use way. ...