From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ludovic =?UTF-8?Q?Court=C3=A8s?= <ludo@gnu.org>
Subject: bug#37744: Per-user profile directory hijack (CVE-2019-17365 for Nix)
Date: Tue, 15 Oct 2019 14:34:46 +0200
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References: <87o8yjsr8o.fsf@gnu.org> <87blujsqq0.fsf@gnu.org>
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In-Reply-To: <87y2xno85o.fsf@nckx> (Tobias Geerinckx-Rice's message of "Mon,
 14 Oct 2019 13:53:35 +0200")
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To: Tobias Geerinckx-Rice <me@tobias.gr>
Cc: 37744@debbugs.gnu.org, guix-security@gnu.org

Hi!

Tobias Geerinckx-Rice <me@tobias.gr> skribis:

> The 1777 is obviously very bad, no question.  However: question:
>
> Ludovic Court=C3=A8s =E5=86=99=E9=81=93=EF=BC=9A
>> I don=E2=80=99t see how to let the daemon create =E2=80=98per-user/$USER=
=E2=80=99 on behalf
>> of
>> the client for clients connecting over TCP.  Or we=E2=80=99d need to add=
 a
>> challenge mechanism or authentication.
>
> I need more cluebat please: say I'm an attacker and connect to your
> daemon (over TCP, why not), asking it to create an empty
> =E2=80=98per-user/ludo=E2=80=99.

You wouldn=E2=80=99t be able to do that because over TCP because the daemon
can=E2=80=99t tell what user you are.

Note that TCP has to be explicitly enabled through =E2=80=98guix-daemon
--listen=3D0.0.0.0=E2=80=99.  It=E2=80=99s meant for cluster setups where y=
ou have one
head node that clients connect to from remote nodes.

I suppose we won=E2=80=99t be able to address the problem in this particular
setup, unless we had some authentication mechanism like I wrote above
(it could be a challenge like the MIT-MAGIC-COOKIE.)

Ludo=E2=80=99.