[secdir] [http-auth] secdir review of draft-ietf-httpauth-basicauth-update-06 -- security considerations on timing/guessing attacks

Julian Reschke <julian.reschke@gmx.de> Fri, 20 February 2015 14:01 UTC

Return-Path: <julian.reschke@gmx.de>
X-Original-To: secdir@ietfa.amsl.com
Delivered-To: secdir@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 453B61A879A; Fri, 20 Feb 2015 06:01:03 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_PASS=-0.001] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 1w2gi39ABW2C; Fri, 20 Feb 2015 06:01:01 -0800 (PST)
Received: from mout.gmx.net (mout.gmx.net [212.227.15.15]) (using TLSv1.2 with cipher DHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 946801A87E3; Fri, 20 Feb 2015 06:01:01 -0800 (PST)
Received: from [192.168.1.26] ([217.91.35.233]) by mail.gmx.com (mrgmx003) with ESMTPSA (Nemesis) id 0M6Ana-1XeEvY1Z1O-00y9uj; Fri, 20 Feb 2015 15:00:34 +0100
Message-ID: <54E73DF9.5050501@gmx.de>
Date: Fri, 20 Feb 2015 15:00:25 +0100
From: Julian Reschke <julian.reschke@gmx.de>
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0
MIME-Version: 1.0
To: Daniel Kahn Gillmor <dkg@fifthhorseman.net>, http-auth@ietf.org
References: <874mqjd49v.fsf@alice.fifthhorseman.net> <54E50FC3.9080708@gmx.de> <871tllbw2c.fsf@alice.fifthhorseman.net> <54E6348A.3080606@gmx.de> <87mw49ac9h.fsf@alice.fifthhorseman.net> <54E648B9.6030606@gmx.de> <9A93C4F9-C14E-410E-81B7-E36E05270FD2@gbiv.com> <877fvda2tp.fsf@alice.fifthhorseman.net> <CA60C432-436E-4982-9982-50E3B803F01A@gbiv.com>
In-Reply-To: <CA60C432-436E-4982-9982-50E3B803F01A@gbiv.com>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
X-Provags-ID: V03:K0:f+CNl1Yjj3irXYTUBnIu6nnFWHJB75gFXI3dHJWb4o0Mt4I49eN WgCs/MUYGnDmKdgFygIVGwg0BEr05F2lHR4jtiqzO4mg8ZQrXfbSXbxmjIvHr4msjQb3hLN 2IIRECaVKI/l47nxdn/j4tBrbcp0St9oQjjQr1Yx3yb5POOvWuZBEQ7DYBcbv5ZLNE2xA9k heloIDyY48KYFzu5Nd18g==
X-UI-Out-Filterresults: notjunk:1;
Archived-At: <http://mailarchive.ietf.org/arch/msg/secdir/6wUVmTgfS-wiVPiwdOPfOnM8uK4>
Cc: secdir@ietf.org, Julian Reschke <julian.reschke@gmx.de>, "Roy T. Fielding" <fielding@gbiv.com>, "http-auth@ietf.org" <http-auth@ietf.org>, iesg@ietf.org, draft-ietf-httpauth-basicauth-update.all@tools.ietf.org
Subject: [secdir] [http-auth] secdir review of draft-ietf-httpauth-basicauth-update-06 -- security considerations on timing/guessing attacks
X-BeenThere: secdir@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: Security Area Directorate <secdir.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/secdir>, <mailto:secdir-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/secdir/>
List-Post: <mailto:secdir@ietf.org>
List-Help: <mailto:secdir-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/secdir>, <mailto:secdir-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 20 Feb 2015 14:01:03 -0000

On 2015-02-20 01:10, Roy T. Fielding wrote:
> ...
>>> A more reasonable thing to say is that any authentication system that
>>> allows a client to perform more than three failed authentication attempts
>>> on a single connection, or more than ten on a single account over multiple
>>> connections, is likely to be vulnerable to password guessing attacks.
>>> Timing attacks then become completely irrelevant.
>>
>> This is an interesting suggestion, and should be useful against more
>> than just timing attacks.  How should that filter be applied?  It seems
>> like it could create some sort of denial of service attack vector if
>> it's not done judiciously (e.g. Alice tries to lock out Bob by faking
>> bad logins from Bob).
>
> Yes, what I've seen is typically implemented as a temporary lock-out
> on the order of minutes -- long enough to prevent iterative attack
> techniques, but short enough that a user wouldn't mind.  It is also
> sometimes combined with an alert to the user.  How to implement it
> correctly depends on the overall web server architecture, such as
> whether the block is only per-server or covers an entire domain.
>
> I don't think we need to describe specifically how to implement it.
> ...

As this advice applies is not specific to Basic: how about putting this 
on our TODO list for RFC 7235bis?

Best regards, Julian