Partially equivalent to commit abf5ef6c22d2 ("apparmor: Allow pasta
to remount /proc, access entries under its own copy"): we should
allow pasta to remount /proc. It still works otherwise, but further
UID remapping in nested user namespaces (e.g. pasta in pasta) won't.

Reported-by: Laurent Jacquot <jk@lutty.net>
Link: https://bugs.passt.top/show_bug.cgi?id=79#c3
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

This reverts commit 3fb3f0f7a59498bdea1d199eecfdbae6c608f78f: it was
meant as a patch for Fedora 37 (and no later versions), not something
I should have merged upstream.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

If passt is started with --fd to talk over a pre-opened UNIX domain
socket, we don't really know what label might be associated to it,
but at least for an unconfined_t socket, this bit of policy wouldn't
belong to anywhere else: enable that here.

This is rather loose, of course, but on the other hand passt will
sandbox itself into an empty filesystem, so we're not really adding
much to the attack surface except for what --fd is supposed to do.

Reported-by: Matej Hrica <mhrica@redhat.com>
Link: https://bugzilla.redhat.com/show_bug.cgi?id=2247221
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

With current selinux-policy-37.22-1.fc37.noarch, and presumably any
future update for Fedora 37, the user_namespace class is not
available, so statements using it prevent the policy from being
loaded.

If a class is not defined in the base policy, any related permission
is assumed to be enabled, so we can safely drop those.

Link: https://bugzilla.redhat.com/show_bug.cgi?id=2237996
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

...now it gets ugly. If we use pasta without an existing target
namespace, and run commands directly or spawn a shell, and keep
the pasta_t domain when we do, they won't be able to do much: a
shell might even start, but it's not going to be usable, or to
even display a prompt.

Ideally, pasta should behave like a shell when it spawns a command:
start as unconfined_t and automatically transition to whatever
domain is associated in the specific policy for that command. But
we can't run as unconfined_t, of course.

It would seem natural to switch to unconfined_t "just before", so
that the default transitions happen. But transitions can only happen
when we execvp(), and that's one single transition -- not two.

That is, this approach would work for:

  pasta -- sh -c 'ip address show'

but not for:

  pasta -- ip address show

If we configure a transition to unconfined_t when we run ip(8), we'll
really try to start that as unconfined_t -- but unconfined_t isn't
allowed as entrypoint for ip(8) itself, and execvp() will fail.

However, there aren't many different types of binaries pasta might
commonly run -- for example, we're unlikely to see pasta used to run
a mount(8) command.

Explicitly set up domain transition for common stuff -- switching to
unconfined_t for bin_t and shells works just fine, ip(8), ping(8),
arping(8) and similar need a different treatment.

While at it, allow commands we spawn to inherit resource limits and
signal masks, because that's what happens by default, and don't
require AT_SECURE sanitisation of the environment (because that
won't happen by default). Slightly unrelated: we also need to
explicitly allow pasta_t to use TTYs, not just PTYs, otherwise
we can't keep stdin and stdout open for shells.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

This is needed to monitor filesystem-bound namespaces and quit when
they're gone -- this feature never really worked with SELinux.

Fixes: 745a9ba4284c ("pasta: By default, quit if filesystem-bound net namespace goes away")
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Acked-by: Richard W.M. Jones <rjones@redhat.com>

That's what we actually need to check networking-related sysctls,
to scan for bound ports, and to manipulate bits of network
configuration inside pasta's target namespaces.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Acked-by: Richard W.M. Jones <rjones@redhat.com>

Somehow most of this used to work on older kernels, but now we need
to explicitly permit setuid, setgid, and setcap capabilities, as well
as read-only access to passwd (as we support running under a given
login name) and sssd library facilities.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Kernel commit ed5d44d42c95 ("selinux: Implement userns_create hook")
seems to just introduce a new functionality, but given that SELinux
implements a form of mandatory access control, introducing the new
permission breaks any application (shipping with SELinux policies)
that needs to create user namespaces, such as passt and pasta for
sandboxing purposes.

Add the new 'allow' rules. They appear to be backward compatible,
kernel-wise, and the policy now requires the new 'user_namespace'
class to build, but that's something distributions already ship.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>

There's no reason to use wildcards, and we don't want any
similarly-named binary (not that I'm aware of any) to risk being
associated to passt_exec_t and pasta_exec_t by accident.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Richard W.M. Jones <rjones@redhat.com>