If you use rootless Podman on a Redhat-derived distribution (which means Selinux), along with a non-root user in your container itself, you're in for a world of pain.
Either the machine is a single security domain, in which case running as root is no issue, or it's not and you need actual isolation in which case run VMs with Firecracker/Kata containers/etc.
Rootless is indeed a world of pain for dubious security promises.
If I just want to run a random Docker container, I'm grateful I can get at least "some security" without paying as much in setup/debugging/performance.
Of course, ideally I wouldn't have to choose and the thing that runs the container would be able to run it perfectly securely without me having to know that. But I appreciate any movement in that direction, even if it's not perfect.
There are existing tools that fill this gap (Singularity/Apptainer). But, there is always friction when you have to use a specialized tool versus the default. For me, this is a core usecase for rootless containers.
For the reduced feature set we need from containers in bioinformatics, rootless is pretty straightforward. You could get largely the same benefits from chroots.
Where I think the issues start is when you start to use networking, subuids, or other features that require root-level access. At this level, rootless because a tedious exercise in configuration that probably isn’t worth the effort. The problem is, the features I need will be different from the features you need. Satisfying all users in a secure was may not be worth it.
Most likely gp is having issues with volumes and hasn’t figured out how to mix the :z and :Z attribute to bind mounts. Or the containers are trying to do something that security-wise is a big no-no.
In my experience SELinux defaults have been much wiser than me and every time i had issues i ended up learning a better way to do what i wanted to do.
Other than that… it essentially just works.
One thing which just occurred to me, maybe it's possible to have a [container] and a [service].user in a quadlet?
Must not be a good sysadmin then. SELinux improves the security and software like podman can be relatively easily be made to work with it.
I use podman on my Fedora Workstation with selinux set to enforce without issues
(Should live at https://forgejo.org/docs/v12.0/admin/actions/docker-access/ once it is finished up, if anyone runs into the comment after the draft is gone.)
A good reference answer: https://unix.stackexchange.com/questions/651198/podman-volum...
TL;DR: lowercase if a file from the host is shared with a container or a volume is shared between multiple containers. Uppercase in the same scenario if you want the container to take an exclusive lock on the volumes/files (very unlikely).
I'm using dind too, but this requires privileged runners...
I'm sure what you wrote here is true but i cant fathom how. Maybe its a rh specific issue? (Like how ubuntu breaks rootless bwrap by default)
I can't see how any kind of sensible security evaluation process would reach that conclusion. If you trust your users you don't need rootless, if you don't trust your users rootless containers aren't good enough. I suspect people do rootless because it seems easy and catches a few accidental mistakes rather than it being a legitimate security measure.
These are almost always multi-tennant with differing levels of trust and experience between users. The data processed here can often have data access agreements or laws that limit who can see what data. You can’t have a poorly configured container exposing data, for example. So, the number of people who have root access is very limited. Normal users running workflows would all be required to run code rootless.
My point is: If figuring things out with podman is similar to my experience, I understand why people don't want to do that. Do they have a definitive page dedicated to setting up Selinux for podman, that is well maintained and guaranteed to solve all Selinux issues, and allows me to use bind mounts with readonly permission?
With podman, RedHat made an effort to make SElinux work. With Docker, as third-party-software, no proper SElinux config was ever written. With Docker, there is no hope at all that you'd get SElinux to work.
With podman, there is hope, as long as all your containers and usecases are simple, "well-behaved" and preferrably also RedHat-based and SElinux-aware. In the easy cases, podman + SElinux will just work. But unfortunately, containers are the means to get crappy software running, where the developers were too lazy to do proper packaging/installation/configuration/integration. So most cases are not easy and will not work with SElinux, if you don't have infinite time to write your own config...