linux-kernel - Re: [PATCH] netfilter: nfnetlink_cthelper: Add missing permission checks

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Date:   Mon, 4 Dec 2017 11:32:00 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Kevin Cernekee <cernekee@...omium.org>
Cc:     netfilter-devel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netfilter: nfnetlink_cthelper: Add missing permission
 checks

On Sun, Dec 03, 2017 at 12:12:45PM -0800, Kevin Cernekee wrote:
> The capability check in nfnetlink_rcv() verifies that the caller
> has CAP_NET_ADMIN in the namespace that "owns" the netlink socket.
> However, nfnl_cthelper_list is shared by all net namespaces on the
> system.

Right, we need per-netns support for nfnetlink_cthelper.

> An unprivileged user can create user and net namespaces
> in which he holds CAP_NET_ADMIN to bypass the netlink_net_capable()
> check:

Applied to nf, thanks.
[...]
> I think xt_osf has the same issue with respect to xt_osf_fingers.
> Also, it looks like nlmon devices created in an unprivileged netns can
> see netlink activity from the init namespace.

A fix that one would be good too.