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Date: Wed, 22 Nov 2017 15:27:11 -0700
From: Kurt Seifried <kseifrie@...hat.com>
To: oss-security@...ts.openwall.com
Cc: Bram Moolenaar <Bram@...lenaar.net>
Subject: Re: Re: Security risk of server side text editing ...

Can you post a summary of the issues, it sounds like more than one CVE will be needed, thanks.


-Kurt





> On Nov 22, 2017, at 15:17, Solar Designer <solar@...nwall.com> wrote:
> 
>> On Fri, Nov 17, 2017 at 11:35:15AM +0100, Bram Moolenaar wrote:
>> Please check out patch 8.0.1300.
> 
> Thanks.  Personally, I don't have much to add.  This continues to do
> what I find are weird and wrong things, so any implementation issues are
> secondary to that.  I suppose you have some rationale for preserving the
> old behavior of propagating the edited file's permissions onto related
> temporary files, but I'm unaware of good reasons for that.
> 
> If it's about users' collaboration, then I don't see a good reason for
> other users in the group, even if they could access the original file
> via group permissions, to also have access to recovery and backup files.
> 
> As to the patch itself, aside from it propagating the possibly unsafe
> permissions on purpose (I mean unsafe such as in Hanno's original
> example, but also applying to backup files), it's also risky in
> temporarily setting umask to 0.  On some systems, this could mean libc
> or the kernel creating files with unsafe permissions if anything goes
> very wrong during this time - e.g., a coredump.  Checking st_ino is OK
> as a hardening measure, but might not always be sufficient: inode number
> reuse is possible if the original file could have been deleted.
> I suppose st_dev is not checked because of the use of O_NOFOLLOW, but I
> guess Vim can be built on systems without working O_NOFOLLOW as well?
> 
> In case anyone wants to review the patch for real, I've attached it to
> this message, and here it is on GitHub (for expanding of the context):
> 
> https://github.com/vim/vim/commit/cd142e3369db8888163a511dbe9907bcd138829c
> 
> Alexander
> <8.0.1300>

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