netdev - Re: nf_conntrack: Infoleak via CTA_ID and CTA_EXPECT

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Date:   Fri, 30 Jun 2017 21:55:47 +0200
From:   Florian Westphal <fw@...len.de>
To:     Richard Weinberger <richard@....at>
Cc:     Florian Westphal <fw@...len.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        David Miller <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        David Gstir <david@...ma-star.at>, kaber@...sh.net,
        "keescook@...omium.org" <keescook@...omium.org>
Subject: Re: nf_conntrack: Infoleak via CTA_ID and CTA_EXPECT_ID

Richard Weinberger <richard@....at> wrote:
> Florian,
> 
> Am 30.06.2017 um 21:35 schrieb Florian Westphal:
> > Richard Weinberger <richard@....at> wrote:
> >> Hi!
> >>
> >> I noticed that nf_conntrack leaks kernel addresses, it uses the memory address
> >> as identifier used for generating conntrack and expect ids..
> >> Since these ids are also visible to unprivileged users via network namespaces
> >> I suggest reverting these commits:
> > 
> > Why not use a hash of the address?
> 
> Would also work. Or xor it with a random number.
> 
> On the other hand, for user space it would be more useful when the conntrack id
> does not repeat that often. That's why I favor the good old counter method.
> Currently the conntrack id is reused very fast.
> e.g. in one of our applications we use the conntack id via NFQUEUE and watch the
> destroy events via conntrack. It happens regularly that a new connection has the
> same id than a different connection we saw some moments before, before we receive
> the destroy event from the conntrack socket.

Perhaps we can place that in a new extension (its not needed in any
fastpath ops)?