From: Maxime Devos <maximedevos@telenet.be>
To: "Ludovic Courtès" <ludo@gnu.org>
Cc: 47584@debbugs.gnu.org
Subject: bug#47584: Race condition in ‘copy-account-skeletons’: possible privilege escalation.
Date: Tue, 06 Apr 2021 11:56:23 +0200 [thread overview]
Message-ID: <00621260aa43f1918aaf0f0bb2318bf359b826c3.camel@telenet.be> (raw)
In-Reply-To: <87zgycqzfz.fsf@gnu.org>
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On Mon, 2021-04-05 at 21:54 +0200, Ludovic Courtès wrote:
> [...]
>
> OK. It does mean that the bug is hardly exploitable in practice: you
> have to be able to log in at all,
Yes.
> and if you’re able to log in, you have
> to log in precisely within the 1s (or less) that follows account
> creation, which sounds challenging (TCP + SSH connection establishment
> is likely to take as much time or more,
Is logging in possible when the home directory doesn't exist?
It isn't possible from the console. I guess it isn't possible from SSH
either.
If it is possible,
then the window would be somewhat larger I think. Account creation is done
at activation time, while creating home directories is done as a shepherd
service (see account-service-type in gnu/system/shadow.scm).
> likewise for typing in your password.)
An attacker could copy and paste, or have used a single-character password,
to save some time.
> It’s also one-time chance.
Yes.
> Do I get it right?
I think so, except the window might be larger (but still a one-time chance).
> Does it warrant as strong messaging as for the recent daemon
> ‘--keep-failed’ vulnerability?
As it is a one-time chance, with a limited window, and only under specific
circumstances (creating a new user account), I don't think so. But I would
still recommend to upgrade. Does the blog post have ‘too strong messaging’?
Greetings,
Maxime
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next prev parent reply other threads:[~2021-04-06 9:57 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
2021-04-04 7:36 ` Maxime Devos
2021-04-05 19:54 ` Ludovic Courtès
2021-04-06 9:56 ` Maxime Devos [this message]
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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