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Some fixes

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Quentin 2021-07-14 23:25:25 +02:00
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_posts/2021-07-14-lxc-drop-capsysadmin.md
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@ -17,15 +17,17 @@ As said by Jessie Frazelle in her blog post [Setting the Record Straight: contai
> A "container" is just a term people use to describe a combination of Linux namespaces and cgroups. Linux namespaces and cgroups ARE first class objects. NOT containers.
In this article, we'll discuss the different "primitives" exposed by the Linux kernel like *namespaces*, *cgroups*, *Linux Security Modules*, *capabilities* and *seccomp*. Our container tool like LXC or Docker, which is a user space binary, will interact with these primitives. We'll see that we can interact with them through the LXC configuration file to improve (or worsen) the security of our LXC container.
The challenge when it comes to hardening a LXC container, compared to other solutions, is that there is a great probability that you'll run systemd in your container. And systemd heavily uses the primitives quoted before. Especially, systemd rely on *cgroups* to handle its services. We can also mention that many systemd daemon will be provided with a configuration that need to interact with the *capabilities*.
If you feel a bit lost with all these terms, a good start is the reading of this whitepaper by the NCCGroup: [Understanding and Hardening Linux Containers](https://www.nccgroup.trust/us/our-research/understanding-and-hardening-linux-containers/). This post is also inspired by the article written by Christian Seiler, [LXC containers without CAP\_SYS\_ADMIN under Debian Jessie](https://blog.iwakd.de/lxc-cap_sys_admin-jessie), but we'll see that, due to evolutions in the Linux kernel, the proposed configuration does not work anymore out of the box.
In this article, we'll boot a container running systemd without `CAP_SYS_ADMIN`, all other hardenings being out of scope for now.
If you feel a bit lost with containers, a good start is the reading of this whitepaper by the NCCGroup: [Understanding and Hardening Linux Containers](https://www.nccgroup.trust/us/our-research/understanding-and-hardening-linux-containers/). This post is also inspired by the article written by Christian Seiler, [LXC containers without CAP\_SYS\_ADMIN under Debian Jessie](https://blog.iwakd.de/lxc-cap_sys_admin-jessie), but we'll see that, due to evolutions in the Linux kernel, the proposed configuration does not work anymore out of the box.
## Creating a standard LXC container
Before starting, you'll need a very recent version of LXC, at least lxc-2.0.9 (not yet released as of this writing). Fortunately, you can compile it from its master branch. We'll see later why we need a such recent version.
Before starting, you'll need a very recent version of LXC, at least lxc-2.0.9.
In any case, compiling LXC is quite straightforward.
Here is a quick reminder on how to compile LXC:
```bash