lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:   Mon, 8 May 2017 15:23:59 +0200
From:   Daniel Gruss <daniel.gruss@...k.tugraz.at>
To:     Thomas Garnier <thgarnie@...gle.com>
CC:     kernel list <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        "clementine.maurice@...k.tugraz.at" 
        <clementine.maurice@...k.tugraz.at>,
        "moritz.lipp@...k.tugraz.at" <moritz.lipp@...k.tugraz.at>,
        Michael Schwarz <michael.schwarz@...k.tugraz.at>,
        Richard Fellner <richard.fellner@...dent.tugraz.at>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Ingo Molnar <mingo@...nel.org>,
        "anders.fogh@...ta-adan.de" <anders.fogh@...ta-adan.de>
Subject: Re: [kernel-hardening] [RFC, PATCH] x86_64: KAISER - do not map
 kernel in user mode

On 05.05.2017 10:23, Daniel Gruss wrote:
>>  - How this approach prevent the hardware attacks you mentioned? You
>> still have to keep a part of _text in the pagetable and an attacker
>> could discover it no? (and deduce the kernel base address).
>
> These parts are moved to a different section (.user_mapped) which is at a possibly predictable location - the location
> of the randomized parts of the kernel is independent of the location of .user_mapped.
> The code/data footprint for .user_mapped is quite small, helping to reduce or eliminate the attack surface...

We just discussed that in our group again: although we experimented with this part, it's not yet included in the patch. 
The solution we sketched is, as I wrote, we map the required (per-thread) variables in the user CR3 to a fixed location 
in memory. During the context switch, only this fixed part remains mapped but not the randomized pages. This is not a 
lot of work, because it's just mapping a few more pages and fixing a 1 or 2 lines in the context switch.

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ