Automating compliance checks

With the configuration baseline for a technical service being described fully (see the first, second and third post in this series), it is time to consider the validation of the settings in an automated manner. The preferred method for this is to use Open Vulnerability and Assessment Language (OVAL), which is nowadays managed by the Center for Internet Security, abbreviated as CISecurity. Previously, OVAL was maintained and managed by Mitre under NIST supervision, and Google searches will often still point to the old sites. However, documentation is now maintained on CISecurity's github repositories.

But I digress...

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Documenting a rule

In the first post I talked about why configuration documentation is important. In the second post I looked into a good structure for configuration documentation of a technological service, and ended with an XCCDF template in which this documentation can be structured.

The next step is to document the rules themselves, i.e. the actual content of a configuration baseline.

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Structuring a configuration baseline

A good configuration baseline has a readable structure that allows all stakeholders to quickly see if the baseline is complete, as well as find a particular setting regardless of the technology. In this blog post, I'll cover a possible structure of the baseline which attempts to be sufficiently complete and technology agnostic.

If you haven't read the blog post on documenting configuration changes, it might be a good idea to do so as it declares the scope of configuration baselines and why I think XCCDF is a good match for this.

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Documenting configuration changes

IT teams are continuously under pressure to set up and maintain infrastructure services quickly, efficiently and securely. As an infrastructure architect, my main concerns are related to the manageability of these services and the secure setup. And within those realms, a properly documented configuration setup is in my opinion very crucial.

In this blog post series, I'm going to look into using the Extensible Configuration Checklist Description Format (XCCDF) as the way to document these. This first post is an introduction to XCCDF functionally, and what I position it for.

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SELinux and extended permissions

One of the features present in the August release of the SELinux user space is its support for ioctl xperm rules in modular policies. In the past, this was only possible in monolithic ones (and CIL). Through this, allow rules can be extended to not only cover source (domain) and target (resource) identifiers, but also a specific number on which it applies. And ioctl's are the first (and currently only) permission on which this is implemented.

Note that ioctl-level permission controls isn't a new feature by itself, but the fact that it can be used in modular policies is.

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SELinux Userspace 2.7

A few days ago, Jason "perfinion" Zaman stabilized the 2.7 SELinux userspace on Gentoo. This release has quite a few new features, which I'll cover in later posts, but for distribution packagers the main change is that the userspace now has many more components to package. The project has split up the policycoreutils package in separate packages so that deployments can be made more specific.

Let's take a look at all the various userspace packages again, learn what their purpose is, so that you can decide if they're needed or not on a system. Also, when I cover the contents of a package, be aware that it is based on the deployment on my system, which might or might not be a complete installation (as with Gentoo, different USE flags can trigger different package deployments).

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Authenticating with U2F

In order to further secure access to my workstation, after the switch to Gentoo sources, I now enabled two-factor authentication through my Yubico U2F USB device. Well, at least for local access - remote access through SSH requires both userid/password as well as the correct SSH key, by chaining authentication methods in OpenSSH.

Enabling U2F on (Gentoo) Linux is fairly easy. The various guides online which talk about the pam_u2f setup are indeed correct that it is fairly simple. For completeness sake, I've documented what I know on the Gentoo Wiki, as the pam_u2f article.

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Using nVidia with SELinux

Yesterday I've switched to the gentoo-sources kernel package on Gentoo Linux. And with that, I also attempted (succesfully) to use the propriatary nvidia drivers so that I can enjoy both a smoother 3D experience while playing minecraft, as well as use the CUDA support so I don't need to use cloud-based services for small exercises.

The move to nvidia was quite simple, as the nvidia-drivers wiki article on the Gentoo wiki was quite easy to follow.

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Switch to Gentoo sources

You've might already read it on the Gentoo news site, the Hardened Linux kernel sources are removed from the tree due to the grsecurity change where the grsecurity Linux kernel patches are no longer provided for free. The decision was made due to supportability and maintainability reasons.

That doesn't mean that users who want to stick with the grsecurity related hardening features are left alone. Agostino Sarubbo has started providing sys-kernel/grsecurity-sources for the users who want to stick with it, as it is based on minipli's unofficial patchset. I seriously hope that the patchset will continue to be maintained and, who knows, even evolve further.

Personally though, I'm switching to the Gentoo sources, and stick with SELinux as one of the protection measures. And with that, I might even start using my NVidia graphics card a bit more, as that one hasn't been touched in several years (I have an Optimus-capable setup with both an Intel integrated graphics card and an NVidia one, but all attempts to use nouveau for the one game I like to play - minecraft - didn't work out that well).

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