[apparmor] Apparmor and Docker - capabilities and network flags not working

[werner_kienzler]

Hallo,

> is docker using user namespaces, or network namespaces?
Good question - I didn't enable "user namespace isolation" in the docker daemon (so I don't set "userns-remap" in "/etc/docker/daemon.json"), so I assume I'm using network namespaces? But I don't have deeper knowledge in this topic - should I run some test here or configure something?


> What is your kernel version? And do you have any none-upstream patches on it.
I use an up to date kernel of my dirstro, which is 5.17.9. It is 100% vanilla and has no patches applied to it.

Greetings

Werner



------- Original Message -------
John Johansen <john.johansen at canonical.com> schrieb am Sonntag, 22. Mai 2022 um 1:09 nachm.:


> On 5/21/22 14:55, werner_kienzler wrote:
>
> > Hello,
> >
> > I try to use AppArmor in conjunction with docker, as in the example explained in the docker docs:
> > https://docs.docker.com/engine/security/apparmor/ https://docs.docker.com/engine/security/apparmor/
> >
> > I want to describe my problems with this example. I copied over the example policy from this website to
> >
> > /etc/apparmor.d/docker-nginx
> >
> > Then I parsed the profile:
> > $ sudo apparmor_parser -r -W /etc/apparmor.d/docker-nginx
> >
> > and "aa-status" shows, that the profile is loaded.
> > Starting docker like:
> >
> > $ sudo docker run --security-opt "apparmor=docker-nginx" -p 80:80 -d --name apparmor-nginx nginx
> >
> > Works like expected - "aa-status" shows, that the resulting docker processes are confined and if I do e.g.
> > $ sudo docker container exec -it apparmor-nginx dash
> >
> > I'm ending in a shell (despite "dash" bein explicitly denied in the profile), but Apparmor works as expected, e.g. executing:
> > # touch /boot/testfile
> >
> > in the container is not possible (permission denied).
> >
> > So I tried to restrict the profile further. Since I don't want to bind the container to a privileged port (< 1024), I thought I don't need
> >
> > capability net_bind_service,
> >
> > in the Apparmor profile.
> > So I removed the corresponding line in the profile and reloaded the profile. To get sure, that everything goes smooth, I did (after removing the corresponding line):
> >
> > $ sudo aa-teardown
> > $ sudo apparmor_parser -r -W /etc/apparmor.d/docker-nginx
> >
> > Then I stopped and removed the container:
> > $ sudo docker stop apparmor-nginx && sudo docker rm apparmor-nginx
> >
> > and restarted it - but again on port 80 (which I expected not to work, since the capability was removed):
> > $ sudo docker run --security-opt "apparmor=docker-nginx" -p 80:80 -d --name apparmor-nginx nginx
> >
> > But it worked. I could access the nginx server on "http://localhost:80 http://localhost:80" in my host browser.
> >
> > I tried further to disable net access completely and removed the following lines:
> >
> > network inet tcp,
> > network inet udp,
> > network inet icmp,
> >
> > and replaced it with:
> >
> > deny network,
> >
> > Again I reloaded the profiles:
> >
> > $ sudo aa-teardown
> > $ sudo apparmor_parser -r -W /etc/apparmor.d/docker-nginx
> >
> > restarted the container:
> > $ sudo docker stop apparmor-nginx && sudo docker rm apparmor-nginx
> > $ sudo docker run --security-opt "apparmor=docker-nginx" -p 80:80 -d --name apparmor-nginx nginx
> >
> > Which works fine - despite the missing capabilities and the "deny network" directive.
> > Then I started again a session in the container:
> > $ sudo docker container exec -it apparmor-nginx dash
>
>
> is docker using user namespaces, or network namespaces?
>
> > And e.g. a
> > # curl www.google.com http://www.google.com
> >
> > is working - I get the expected output, despite "deny network".
> > So my main concerns are:
> > 1. despite disabling "capability net_bind_service" I can bind to port 80
> > 2. despite "deny network" I can use curl
> >
> > I'm using Arch Linux on the host, with Apparmor 3.0.4 and docker 1.20.10.16.
>
> What is your kernel version? And do you have any none-upstream patches on it.
>
> > Can anybody help me with this problem? From my point of view this should not be possible, or can anybody give me an explanation?
> >
> > Thanks
> >
> > Werner