From: "Ludovic Courtès" <ludo@gnu.org>
To: Maxime Devos <maximedevos@telenet.be>
Cc: 47584@debbugs.gnu.org
Subject: bug#47584: Race condition in ‘copy-account-skeletons’: possible privilege escalation.
Date: Sat, 03 Apr 2021 22:33:18 +0200 [thread overview]
Message-ID: <87mtufw1kh.fsf@gnu.org> (raw)
In-Reply-To: <1a6ed722dfdd96dc8d53f939aa8e440ca7c29213.camel@telenet.be> (Maxime Devos's message of "Sat, 03 Apr 2021 18:09:16 +0200")
Maxime Devos <maximedevos@telenet.be> skribis:
> The attack consists of the user being logged in after the account
> skeletons have been copied to the home directory, but before the
> owner of the account skeletons have been set. The user then deletes
> a copied account skeleton (e.g. @file{$HOME/.gdbinit}) and replaces
> it with a symbolic link to a file not owned by the user, such as
> @file{/etc/shadow}.
>
> The activation code then changes the ownership
> of the file the symbolic link points to instead of the symbolic
> link itself. At that point, the user has read-write access
> to the target file.
In the draft blog post, you mention that the attack cannot be carried
out when protected symlinks are enabled. This is now the case by
default on Guix System¹, so in that case, a system upgraded from a
commit after March 16th is unaffected.
Ludo’.
¹ https://issues.guix.gnu.org/47013#13
next prev parent reply other threads:[~2021-04-03 20:34 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-03 16:09 bug#47584: Race condition in ‘copy-account-skeletons’: possible privilege escalation Maxime Devos
2021-04-03 16:22 ` Maxime Devos
2021-04-03 16:32 ` Maxime Devos
2021-04-03 20:15 ` Ludovic Courtès
2021-04-03 16:26 ` Maxime Devos
2021-04-03 20:45 ` Ludovic Courtès
2021-04-03 20:49 ` Ludovic Courtès
2021-04-04 13:29 ` Maxime Devos
2021-04-03 20:27 ` Ludovic Courtès
2021-04-03 20:33 ` Ludovic Courtès [this message]
2021-04-04 7:36 ` Maxime Devos
2021-04-05 19:54 ` Ludovic Courtès
2021-04-06 9:56 ` Maxime Devos
2021-04-06 11:57 ` Ludovic Courtès
2021-04-07 18:28 ` Maxime Devos
2022-10-21 9:31 ` Maxime Devos
2022-10-28 16:03 ` bug#47584: [DRAFT PATCH v2 0/4] Fix race condition in mkdir-p/perms Maxime Devos
2022-10-28 16:04 ` bug#47584: [PATCH 1/3] guile-next: Update to 3.0.8-793fb46 Maxime Devos
2022-10-28 16:04 ` bug#47584: [PATCH 2/3] WIP gnu: Change the Guile used for activation to one that has 'openat' Maxime Devos
2022-10-28 16:04 ` bug#47584: [PATCH 3/3] activation: Fix TOCTTOU in mkdir-p/perms Maxime Devos
2022-10-28 16:05 ` bug#47584: [PATCH 1/3] guile-next: Update to 3.0.8-793fb46 Maxime Devos
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