full-disclosure - Re: File system recursion and symlinks: A never-ending story (and how to bring it to an end for me)

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Date: Mon, 30 May 2011 17:09:38 -0700
From: Andrew Farmer <andfarm@...il.com>
To: coderman <coderman@...il.com>
Cc: full-disclosure@...ts.grok.org.uk
Subject: Re: File system recursion and symlinks: A
	never-ending story (and how to bring it to an end for me)

On 2011-05-30, at 16:27, coderman wrote:
> On Mon, May 30, 2011 at 6:56 AM, halfdog <me@...fdog.net> wrote:
>> 
>> It seems that quite a few backup applications are (or were) vulnerable
>> to special combined symlink/timing attacks on pathname components before
>> the last one (so O_NOFOLLOW does not help).
>> ...
>> Please let me know, if ... you
>> have good reason, that the kernel interface is not the point, where this
>> issue could be addressed most efficiently.
> 
> use lvm snapshots for backups, either directly at volume level or
> mounting a read-only snapshot and running backup over that static
> filesystem state.

LVM snapshots have some nasty gotchas, though:

https://bugs.launchpad.net/lvm2/+bug/360237

They also don't solve the problem of restoring a fragment of data (e.g, a single accidentally deleted file) from a backup in an untrustworthy environment.
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