Am 27.10.2014 um 23:20 schrieb Lennart Poettering:
On Mon, 27.10.14 20:16, Michael Scherer (m...@zarb.org) wrote:

On Mon, Oct 27, 2014 at 03:38:37PM +0100, Lennart Poettering wrote:
On Sat, 11.10.14 21:57, m...@zarb.org (m...@zarb.org) wrote:

From: Michael Scherer <m...@zarb.org>

Since apparmor need to access /proc to communicate with the kernel,
any unit setting / as readonly will be unable to also use the
AppArmorProfile setting, as found on debian bug 760526.

A unit that sets /proc to read-only is broken anyway, I don't think we
should work around that. or am I missing something here?

When a unit set / as readonly, /proc seems to become readonly too.

Yes, it ReadOnlyDirectories= is recursive. People doing that should
use ReadWriteDirectories=/proc to open up /proc again.

Note that ReadOnlyDirectories= and ReadWriteDirectories= are low-level
functionality. If you use it you really should know what you do. This
is different from ProtectSystem= which is a lot more high-level and
doesn't require you to think about all the details.

And I would count setting /proc as readonly ( or unreadable ) as a hardening
measure to reduce the attack surface.

Well, people can do whatever they want, but write access to /proc is
part of the Linux API, there's ton of functionality that processes
need access to that is only available via writes to /proc. You cannot
really take this away, except for trivial programs. systemd is really
not the place to push for read-only /proc/self/...

The APIs in /proc are generally useful APIs, you cannot just declare
them unnecessary, take them away and assume things to still work

in fact you can even set

InaccessibleDirectories=/proc
InaccessibleDirectories=/sys

and httpd, trafficserver, dovecot, postfix, spamassassin, clamd and what not else just works without any single issue

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