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From: Jeff King <peff@peff.net>
To: Lukas Straub <lukasstraub2@web.de>
Cc: Junio C Hamano <gitster@pobox.com>,
	"Randall S. Becker" <rsbecker@nexbridge.com>,
	'git' <git@vger.kernel.org>, 'Elijah Newren' <newren@gmail.com>,
	'Brandon Williams' <bwilliams.eng@gmail.com>,
	'Johannes Schindelin' <Johannes.Schindelin@gmx.de>
Subject: Re: [RFC PATCH 0/2] Allow adding .git files and directories
Date: Thu, 20 Aug 2020 09:08:13 -0400	[thread overview]
Message-ID: <20200820130813.GC2522289@coredump.intra.peff.net> (raw)
In-Reply-To: <20200820143755.06d39a05@luklap>

On Thu, Aug 20, 2020 at 02:37:55PM +0200, Lukas Straub wrote:

> > Right now git-fsck complains about ".git" appearing in a tree, and that
> > check blocks people from pushing such trees to any hosting sites that
> > enable transfer.fsckObjects (which includes hosters like GitHub). So
> > you'd not only need to allow the behavior to be loosened for all of the
> > people using the feature, but you'd need to convince server-side hosters
> > to loosen their config. And because part of the purpose is to protect
> > downstream clients from attacks, I doubt that public hosters like GitHub
> > would do so.
> 
> I guess they can add a checkbox to their (secured) web-ui to configure
> this.

No, that would defeat the purpose. Hosting sites aren't protecting users
from themselves. They're concerned about malicious actors pushing up
objects that violate expectations and make the hosting site a vector for
attacks. Either against other parts of the site, or against downstream
users who aren't running fully-patched versions of Git (or perhaps are
running a misconfigured one, if there's a known-unsafe configuration).

I don't know of a version of Git that's vulnerable to ".git" (it should
be blocked from entering the index by verify_path()), but the fsck
checks are one layer of a multiple-layer defense against such problems
(which have helped us contain other path-related vulnerabilities).
Letting the potential attacker turn off that layer makes it pointless.

> In the worst-case where the hosting sites don't adopt this config, the user
> enables and uses this feature despite the warnings and then wants to use a
> hosting site, he can still rewrite the history. Not nice, but no disaster
> either.

In general, I do like to err on the side of providing users tools to
shoot themselves in the foot. But this feels like it crosses even my bar
for a foot-gun, especially when there are other solutions available.

-Peff

  reply	other threads:[~2020-08-20 13:08 UTC|newest]

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-08-19 16:43 Lukas Straub
2020-08-19 16:43 ` [RFC PATCH 1/2] dir/read-cache: " Lukas Straub
2020-08-19 16:43 ` [RFC PATCH 2/2] dir: Recurse into nested git repos if they aren't submodules Lukas Straub
2020-08-19 18:03 ` [RFC PATCH 0/2] Allow adding .git files and directories Junio C Hamano
2020-08-19 18:47   ` Randall S. Becker
2020-08-19 19:09     ` Junio C Hamano
2020-08-19 19:23       ` Randall S. Becker
2020-08-19 20:17       ` Jeff King
2020-08-19 20:32         ` Junio C Hamano
2020-08-19 20:38           ` Jeff King
2020-08-19 21:56             ` Randall S. Becker
2020-08-20 10:16             ` Johannes Schindelin
2020-08-20 11:34             ` Lukas Straub
2020-08-20 13:01               ` Jeff King
2020-08-21 12:39                 ` Lukas Straub
2020-08-21 13:11                   ` Randall S. Becker
2020-08-21 22:52                   ` brian m. carlson
2020-08-22 14:21                     ` Lukas Straub
2020-08-22 18:53                       ` brian m. carlson
2020-08-22 19:12                         ` Lukas Straub
2020-08-24 13:52                           ` Johannes Schindelin
2020-08-20 12:37         ` Lukas Straub
2020-08-20 13:08           ` Jeff King [this message]
2020-08-19 19:22     ` Lukas Straub
2020-08-19 18:47   ` Lukas Straub
2020-08-19 19:16     ` Randall S. Becker
2020-08-20 11:46       ` Lukas Straub

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