bug#37744: Per-user profile directory hijack (CVE-2019-17365 for Nix)

[Ludovic Courtès]

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---

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’.