From owner-freebsd-security@FreeBSD.ORG  Wed Dec 10 17:02:58 2003
Return-Path: <owner-freebsd-security@FreeBSD.ORG>
Delivered-To: freebsd-security@freebsd.org
Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP id D2E7016A4CE
	for <security@freebsd.org>; Wed, 10 Dec 2003 17:02:58 -0800 (PST)
Received: from tenebras.com (laptop.tenebras.com [66.92.188.18])
	by mx1.FreeBSD.org (Postfix) with SMTP id B2ED343D30
	for <security@freebsd.org>; Wed, 10 Dec 2003 17:02:57 -0800 (PST)
	(envelope-from kudzu@tenebras.com)
Received: (qmail 13890 invoked from network); 11 Dec 2003 01:02:57 -0000
Received: from sapphire.tenebras.com (HELO tenebras.com) (192.168.188.241)
  by laptop.tenebras.com with SMTP; 11 Dec 2003 01:02:57 -0000
Message-ID: <3FD7C240.4030005@tenebras.com>
Date: Wed, 10 Dec 2003 17:02:56 -0800
From: Michael Sierchio <kudzu@tenebras.com>
User-Agent: Mozilla/5.0 (X11; U; Linux i386; en-US; rv:1.5) Gecko/20031007
X-Accept-Language: en-us, zh-tw, zh-cn, fr, en, de-de
MIME-Version: 1.0
To: Brett Glass <brett@lariat.org>
References: <6.0.0.22.2.20031210115335.04c2fc50@localhost>
	<20031210093927.70c87960.amonk@gnutec.com>
	<6.0.0.22.2.20031210124332.04e94ac0@localhost>
	<16343.33321.632599.190251@oscar.buszard-welcher.com>
	<6.0.0.22.2.20031210173916.04f57be8@localhost>
In-Reply-To: <6.0.0.22.2.20031210173916.04f57be8@localhost>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
cc: Kyle Amon <amonk@gnutec.com>
cc: security@freebsd.org
Subject: Re: s/key authentication for Apache on FreeBSD?
X-BeenThere: freebsd-security@freebsd.org
X-Mailman-Version: 2.1.1
Precedence: list
List-Id: Security issues [members-only posting]
	<freebsd-security.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-security>,
	<mailto:freebsd-security-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/freebsd-security>
List-Post: <mailto:freebsd-security@freebsd.org>
List-Help: <mailto:freebsd-security-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/freebsd-security>,
	<mailto:freebsd-security-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Thu, 11 Dec 2003 01:02:58 -0000

Brett Glass wrote:

> The people in question have Palm Pilots. And, yes, in a pinch
> slips of paper could be generated. The key thing is to be able
> to get in from a public kiosk without the risk of compromised
> passwords.

The problem with S/key or OPIE authentication is that it
is sadly subject to a MITM attack, and relies on
blind trust in the server.

The challenge is not a random challenge, it is unfortunately
a sequence number and salt -- if I trick you into typing in
the one-time password with a lower sequence number than the
current one you are proper fucked.  I can then generate all of
the subsequent "one-time" passwords.

If you have a half-authenticated SSL connection, and are
conducting the exchange over it, then it should be fine.