Re: [PATCH v2 0/1] selinux: Transition to pasta_t in containers

[Stefano Brivio <sbrivio@redhat.com>]

On Thu, 15 May 2025 23:11:02 -0600
Max Chernoff <git@maxchernoff.ca> wrote:

> Hi Stefano,
> 
> On Thu, 2025-05-15 at 17:55 +0200, Stefano Brivio wrote:
> > Instead of these three "unsorted" rules:
> >  
> > > +allow pasta_t container_runtime_t:fifo_file write;  
> >
> > ...as I mentioned, changing this to:
> >
> > allow pasta_t container_runtime_t:fifo_file { write getattr };
> >
> > fixes the remaining warning. And I think it should be "grouped"
> > together with the TCP socket stuff above, that is, just after:
> >
> > corenet_tcp_bind_generic_node(pasta_t)
> >
> > because it's something we need for (loopback) TCP connections, together
> > with TCP sockets.  
> 
> Done.
> 
> > > +allow pasta_t self:cap_userns { setgid setuid };  
> >
> > Strictly speaking, this part shouldn't be needed, see points 7. and c.
> > at:
> >
> >   https://bugzilla.redhat.com/show_bug.cgi?id=2330512#c10
> >
> > ...unfortunately, I never got any feedback about those and I haven't
> > found the time to fix this in kernel either, so, sure, let's keep this
> > rule to avoid noise. We could group this together with capabilities
> > stuff, that is, just after:
> >
> > allow pasta_t self:cap_userns { setpcap sys_admin sys_ptrace net_admin net_bind_service };
> >
> > (but separated, so that we can drop them without code churn) and maybe
> > add a comment referencing:
> >
> >   https://bugzilla.redhat.com/show_bug.cgi?id=2330512#c10
> >
> > and the fact that setuid() and setgid() are always called with the current
> > UID and GID in the detached user namespace.  
> 
> If the denial is harmless (as mentioned in the bug), why not make it
> "dontaudit"? I've tested it out and it seems to work fine for me.

Because it reminds me I should send a kernel fix every time I see it ;)
but that's not a good reason to scare users, so I think your approach
is valid.

> > > +allow pasta_t tmpfs_t:filesystem getattr;  
> >
> > This is needed regardless of Podman, getattr was simply missing from:
> >
> > allow pasta_t tmpfs_t:filesystem mount;
> >
> > so I would rather add it there, together with mount.  
> 
> Done.
> 
> > > +# Allow pasta to bind to any port
> > > +bool pasta_allow_bind_any_port true;
> > > +if (pasta_allow_bind_any_port) {
> > > +	allow pasta_t port_type:icmp_socket { accept getopt name_bind };
> > > +	allow pasta_t port_type:tcp_socket { accept getopt name_bind name_connect };
> > > +	allow pasta_t port_type:udp_socket { accept getopt name_bind };
> > > +}  
> 
> I renamed this to "pasta_bind_all_ports" since that better matches the
> preexisting booleans "git_session_bind_all_unreserved_ports",
> "mozilla_plugin_bind_unreserved_ports", and "tor_bind_all_unreserved_ports".

Ah, right, thanks for checking.

> > > -/usr/bin/pasta			system_u:object_r:pasta_exec_t:s0
> > > -/usr/bin/pasta.avx2		system_u:object_r:pasta_exec_t:s0
> > > -/tmp/pasta\.pcap		system_u:object_r:pasta_log_t:s0
> > > -/var/run/pasta\.pid		system_u:object_r:pasta_pid_t:s0
> > > +/usr/bin/pasta			                               system_u:object_r:pasta_exec_t:s0
> > > +/usr/bin/pasta.avx2		                               system_u:object_r:pasta_exec_t:s0
> > > +/tmp/pasta\.pcap		                               system_u:object_r:pasta_log_t:s0
> > > +/var/run/pasta\.pid		                               system_u:object_r:pasta_pid_t:s0
> > > +/run/user/%{USERID}/netns                              system_u:object_r:ifconfig_var_run_t:s0
> > > +/run/user/%{USERID}/containers/networks/rootless-netns system_u:object_r:ifconfig_var_run_t:s0  
> 
> I also corrected the whitespace here to use tabs (instead of the awful tab-space
> mix that I accidentally used).
> 
> Also, when this commit is eventually packaged, you'll need to run restorecon on
> /run/; otherwise you won't be able to start any containers until you log out and
> back in. I think that %selinux_relabel_post should handle this, but I'm not sure
> if it excludes /run/ or not.

Oops, thanks for mentioning that. I indeed ran restorecon -R /run
manually to test your change, and I thought %selinux_relabel_post would
indeed take care of it on upgrades.

But it looks like it doesn't. I checked with /var/run/pasta.pid and the
label doesn't get fixed. fixfiles(8) has a:

        find /var/run \( -context "*:${UNLABELED}*" -o -context "*:${UNDEFINED}*" \) -exec chcon --no-dereference --reference /var/run {} \;

which shouldn't however affect this. I couldn't quite find out where
the issue is. Worst case, I'll add an explicit restorecon(8) call in
the spec file (feel free to propose a change for that too, of
course...).

-- 
Stefano