https://github.com/containers/bubblewrap
It's the base for Flatpack, the thing that makes Flatpack be sandboxed.
I use it to run Claude Code / Codex / Gemini CLI, to make sure that they have a limited / fake view of my system.
You can bind directories into it, or overlay them into it, restrict other kinds of access.
If Docker is a thing in a scale between a VM and your OS, Bubblewrap is a thing a scale between Docker and your OS. You use your OS, instead of installing and managing an OS like you do with Docker, but you get filesystem and process isolation like with Docker.
Though I had an issue where I cannot use `--new-session`, which is kind of dangerous to not use, but you can get around it if you use seccomp to block ioctl calls, and ptrace.
How do you know what permissions are required by an application, to write a bubblewrap script?
In AppArmor, you exercise the application and aa-logprof suggests permissions requested by application. If you know AppArmor, usually you can refine those suggestions and write a profile. It may not be ideal, as aa-logprof’s permissions are multiple choice suggestions, require user knowledge and may be too broad or specific, but it could work. You will see that there are many and all kinds of permissions, and there is no way that you will be able to guess them without aa-logprof.
What is the equivalent of aa-logprof in bubblewrap and how do you find the required permissions?
Moreover it vendores patched gcc compiler, so the entire toolchain is reproducible too as well.
How cool is that?! For the record golang brings it further - its entire package registry containing +40mln packages is bit by bit reproducible.
This allows independent people to check that provided binaries don't contain malicious stuff for instance. Ultimately, it lets you download binaries instead of rebuilding everything yourself locally if the binaries have been independently reproduced.
You might be interested in checking:
is it a common practice?
bwrap --dev-bind /dev /dev --tmpfs /tmp -- labwc
bwrap --dev-bind /dev /dev --tmpfs /tmp -- kwin_wayland konsole
bwrap --dev-bind /dev /dev --tmpfs /tmp -- startplasma-wayland
That's obviously super permissive, but from there can take things away to expose as much or little of the host system as needed.
For my system I'm working on making a few bwrapped "zones". E.g. start a terminal that can see a certain subset of files, and can configure whether it should use gpu or not, have internet or not, have access to local network or not, etc. A bit more project/environment focused than bwrapping programs one by one.
But firejail needs root privilege, so there are arguments that it may actually reduce the security, because even though it sandboxes some applications, non-privilege processes may gain privilege if there is a flaw in the fire jail itself.
Firejail is also criticized for complexity.
Complexity? It just supports a lot of stuff. See the manual page. It seems simple enough to me.
Complexity referred to large code base and attack surface.
I haven’t tried it myself. I would be interested knowing, whether it might lower the security in some cases. Maybe it’s useful to sandbox apps that don’t have flatpaks.
Still, it can happen of course, particularly with memory-unsafe languages. Conversely without root privileges you have to sacrifice strength of your sandbox, widening the vulnerability window in the app you were trying to constrain to begin with.
Meanwhile bubblewrap relies on user namespaces, which come with their own set of security problems. They are disabled by default in many distributions for that reason.
My gut sense is that flatpak gets much more scrutiny since it ships, and firejail is typically not shipped, but another package as far as I can tell (maybe in some specialized distros?).