netdev - Re: [PATCH] TCP: add option for silent port knocking with integrity protection

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:	Thu, 12 Dec 2013 12:43:59 +0100
From:	Christian Grothoff <grothoff@...tum.de>
To:	Jacob Appelbaum <jacob@...elbaum.net>
CC:	Andi Kleen <andi@...stfloor.org>,
	Stephen Hemminger <stephen@...workplumber.org>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org, knock@...net.org
Subject: Re: [PATCH] TCP: add option for silent port knocking with integrity
 protection

On 12/12/2013 11:19 AM, Jacob Appelbaum wrote:
> I think that generally, I would prefer if the code didn't use MD5 but
> otherwise, I don't see any real risk of adding an exploitable hole. It
> seems silly to disable it by default though - ideally, I'd like a sysctl
> to ensure that Tor could use this without making the user recompile
> their kernel. That is more of a pain than running a userspace helper, I
> think.
> 
> All the best,
> Jacob

Given that the output is truncated to 32 bits and that performance (SYN
flood) is also a concern, AND that the original TCP SQN generation is
also MD5-based (and we want to look the same), what disadvantage do you
see over MD5?  Given the truncation to 32 bits, I don't think a stronger
hash would do anything for us.

As for it being disabled by default, we did this with respect to
kernel submission guidelines which we understood said that features
should _initially_ always be submitted with disabled-by-default
(presumably so that until they have stabilized, nobody is harmed
unless they explicitly activate the code).

I don't see the point in having a sysctl, as applications have to
explicitly request it anyway.

-Christian

Download attachment "0x48426C7E.asc" of type "application/pgp-keys" (8570 bytes)

Download attachment "signature.asc" of type "application/pgp-signature" (260 bytes)