Re: nf_conntrack: Infoleak via CTA_ID and CTA_EXPECT_ID

From: Richard Weinberger
Date: Wed Jul 12 2017 - 17:26:48 EST


Am 01.07.2017 um 12:35 schrieb Florian Westphal:
>>> Perhaps we can place that in a new extension (its not needed in any
>>> fastpath ops)?
>> To get rid of the infoleak we have to re-introduce the id field in struct nf_conn
>> and struct nf_conntrack_expect.
> Why will this not work?

You are right, when we compute the ID from the whole object, it should be fine.

>> Otherwise have nothing to compare against in the conntrack/expect remove case.
> Not following, sorry. The id is not used anywhere except when we send
> info to userspace.
> The compare on removal is not needed afaics, and its also not used when
> doing lookup to begin with, so we can just recompute it?

Isn't this a way too much overhead?

I personally favor Pablo's per-cpu counter approach.
That way the IDs are unique again and we get rid of the info leak without
much effort.