linux-kernel - Re: [PATCH v4] Protected FIFOs and regular files

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Date:   Tue, 10 Apr 2018 14:23:17 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Salvatore Mesoraca <s.mesoraca16@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        Alan Cox <gnomes@...rguk.ukuu.org.uk>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        David Laight <David.Laight@...lab.com>,
        Ian Campbell <ijc@...lion.org.uk>,
        Jann Horn <jannh@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Pavel Vasilyev <dixlor@...il.com>,
        Solar Designer <solar@...nwall.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Tobin C. Harding" <me@...in.cc>
Subject: Re: [PATCH v4] Protected FIFOs and regular files

On Wed, Feb 28, 2018 at 1:22 AM, Salvatore Mesoraca
<s.mesoraca16@...il.com> wrote:
> 2018-02-27 21:22 GMT+01:00 Kees Cook <keescook@...omium.org>:
>> On Tue, Feb 27, 2018 at 11:47 AM, Kees Cook <keescook@...omium.org> wrote:
>>> On Tue, Feb 27, 2018 at 3:00 AM, Salvatore Mesoraca
>>> <s.mesoraca16@...il.com> wrote:
>>>> Disallows open of FIFOs or regular files not owned by the user in world
>>>> writable sticky directories, unless the owner is the same as that of
>>>> the directory or the file is opened without the O_CREAT flag.
>>>> The purpose is to make data spoofing attacks harder.
>>>> This protection can be turned on and off separately for FIFOs and regular
>>>> files via sysctl, just like the symlinks/hardlinks protection.
>>>> This patch is based on Openwall's "HARDEN_FIFO" feature by Solar
>>>> Designer.
>>>>
>>>> This is a brief list of old vulnerabilities that could have been prevented
>>>> by this feature, some of them even allow for privilege escalation:
>>>> CVE-2000-1134
>>>> CVE-2007-3852
>>>> CVE-2008-0525
>>>> CVE-2009-0416
>>>> CVE-2011-4834
>>>> CVE-2015-1838
>>>> CVE-2015-7442
>>>> CVE-2016-7489
>>>>
>>>> This list is not meant to be complete. It's difficult to track down
>>>> all vulnerabilities of this kind because they were often reported
>>>> without any mention of this particular attack vector.
>>>> In fact, before hardlinks/symlinks restrictions, fifos/regular
>>>> files weren't the favorite vehicle to exploit them.
>>>>
>>>> Suggested-by: Solar Designer <solar@...nwall.com>
>>>> Suggested-by: Kees Cook <keescook@...omium.org>
>>>> Signed-off-by: Salvatore Mesoraca <s.mesoraca16@...il.com>
>>>> [...]
>>>
>>> I think this looks great.
>>>
>>> Acked-by: Kees Cook <keescook@...omium.org>
>>
>> Tested-by: Kees Cook <keescook@...omium.org>
>
> Awesome! Thank you very much for your help!

Salvatore, do you want to send this again as a v5 with my two
follow-up patches, as I have them here:
https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git/log/?h=kspp/userspace/protected-creat

or would you like me to send those? I would expect this series to land
via the -mm tree, since that tends to be the catch-all. (In which
case, the series should be To: akpm with everyone else in Cc.)

-Kees

-- 
Kees Cook
Pixel Security