#37744 Insecure permissions on /var/guix/profiles/per-user (CVE-2019-18192)

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Date: Wed, 16 Oct 2019 21:58:39 +0200
From: Julien Lepiller <julien@lepiller.eu>
To: Ludovic Courtès <ludo@gnu.org>
Subject: Re: bug#37744: Per-user profile directory hijack (CVE-2019-17365
 for Nix)
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Le Wed, 16 Oct 2019 19:05:44 +0200,
Ludovic Courtès <ludo@gnu.org> a écrit :

> Hi!
> 
> Thanks for your feedback Tobias, Florian, and Julien!
> 
> Taking that into account, I propose this (I’ve also changed the title
> to make it hopefully clearer):
> 
> --8<---------------cut here---------------start------------->8---
>  (entry (commit "FIXME")
>         (title (en "Insecure @file{/var/guix/profiles/per-user}
> permissions")) (body
>          (en "The default user profile, @file{~/.guix-profile},
> points to @file{/var/guix/profiles/per-user/$USER}.  Until now,
> @file{/var/guix/profiles/per-user} was world-writable, allowing the
> @command{guix} command to create the @code{$USER} sub-directory.
> 
> On a multi-user system, this allowed a malicious user to create and
> populate that @code{$USER} sub-directory for another user that had
> not yet logged in. Since @code{/var/@dots{}/$USER} is in
> @code{$PATH}, the target user could end up running attacker-provided
> code.  See @uref{https://issues.guix.gnu.org/issue/37744} for more
> information.
> 
> This is now fixed by letting @command{guix-daemon} create these
> directories on behalf of users and removing the world-writable
> permissions on @code{per-user}.  On multi-user systems, we recommend
> updating the daemon now. To do that, run @code{sudo guix pull} if
> you're on a foreign distro, or run @code{guix pull && sudo guix
> system reconfigure @dots{}} on Guix System.  In both cases, make sure
> to restart the service afterwards, with @code{herd} or
> @code{systemctl}."))) --8<---------------cut
> here---------------end--------------->8---

pour le français (n'hésite pas à reprendre le texte si tu trouves à
redire :)) :

titre : Permissions laxistes pour @file{/var/guix/profiles/per-user}

corps : Le profil utilisateur par défaut, @file{~/.guix-profile},
pointe vers @file{/var/guix/profiles/per-user/$USER}.  Jusqu'à
maintenant, @file{/var/guix/profiles/per-user} était disponible en
écriture pour tout le monde, ce qui permettait à la commande
@command{guix} de créér le sous-répertoire @code{$USER}.

Sur un système multi-utilisateur, cela permet à un utilisateur
malveillant de créer et de remplir le sous-répertoire @code{USER} pour
n'importe quel utilisateur qui ne s'est jamais connecté.  Comme
@code{/var/@dots{}/$USER} fait partie de @code{$PATH}, l'utilisateur
ciblé pouvait exécuter des programmes fournis par l'attaquant.  Voir
@uref{https://issues.guix.gnu.org/issue/37744} pour plus de détails.

Cela est maintenant corrigé en laissant à @command{guix-daemon} le soin
de créer ces répertoire pour le compte des utilisateurs et en
supprimant les permissions en écriture pour tout le monde sur
@code{per-user}.  Nous te recommandons de mettre à jour le démon
immédiatement.  Pour cela, lance @code{sudo guix pull} si tu es sur
une distro externe ou @code{guix pull && sudo guix system reconfigure
@dots{}} sur le système Guix.  Dans tous les cas, assure-toi ensuite de
redémarrer le service avec @code{herd} ou @code{systemctl}.

> 
> If this is fine with you, I hereby request translation of this entry.
> :-)
> 
> I’ll commit the change within a few hours if there are no objections.
> 
> Ludo’.
> 
> 
> 

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