Re: [secdir] secdir review of draft-harkins-salted-eap-pwd-06
Simon Josefsson <simon@josefsson.org> Sat, 24 September 2016 09:16 UTC
Return-Path: <simon@josefsson.org>
X-Original-To: secdir@ietfa.amsl.com
Delivered-To: secdir@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 0BEA112B6A4; Sat, 24 Sep 2016 02:16:47 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.201
X-Spam-Level:
X-Spam-Status: No, score=-4.201 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_MED=-2.3, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
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 bk-9ivDcabpm; Sat, 24 Sep 2016 02:16:45 -0700 (PDT)
Received: from duva.sjd.se (duva.sjd.se [IPv6:2001:9b0:1:1702::100]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 9E80412B65A; Sat, 24 Sep 2016 02:16:44 -0700 (PDT)
Received: from latte.josefsson.org ([IPv6:2001:9b0:104:42::a86]) (authenticated bits=0) by duva.sjd.se (8.14.4/8.14.4/Debian-4+deb7u1) with ESMTP id u8O9GSq0029158 (version=TLSv1/SSLv3 cipher=AES128-GCM-SHA256 bits=128 verify=NOT); Sat, 24 Sep 2016 11:16:30 +0200
Date: Sat, 24 Sep 2016 11:16:22 +0200
From: Simon Josefsson <simon@josefsson.org>
To: Dan Harkins <dharkins@lounge.org>
Message-ID: <20160924111622.6d1308ce@latte.josefsson.org>
In-Reply-To: <66a779c8-d87b-7c70-c7cf-7eabc48f9880@lounge.org>
References: <87fuosqtkh.fsf@latte.josefsson.org> <66a779c8-d87b-7c70-c7cf-7eabc48f9880@lounge.org>
X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu)
MIME-Version: 1.0
Content-Type: multipart/signed; micalg="pgp-sha256"; boundary="Sig_/jFWRtLRbl4z4umFBeer7kxB"; protocol="application/pgp-signature"
X-Virus-Scanned: clamav-milter 0.99.2 at duva.sjd.se
X-Virus-Status: Clean
Archived-At: <https://mailarchive.ietf.org/arch/msg/secdir/ZfXgpN9wyA9Pka6DgdqsJQgPCZ8>
Cc: draft-harkins-salted-eap-pwd.all@ietf.org, iesg@ietf.org, secdir@ietf.org
Subject: Re: [secdir] secdir review of draft-harkins-salted-eap-pwd-06
X-BeenThere: secdir@ietf.org
X-Mailman-Version: 2.1.17
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: <https://mailarchive.ietf.org/arch/browse/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: Sat, 24 Sep 2016 09:16:47 -0000
Den Fri, 23 Sep 2016 10:37:25 -0700 skrev Re: [secdir] secdir review of draft-harkins-salted-eap-pwd-06: > > Hi Simon, > > On 9/22/16 12:31 AM, Simon Josefsson wrote: > > Hello, > > > > I have reviewed this document as part of the security directorate's > > ongoing effort to review all IETF documents being processed by the > > IESG. These comments were written primarily for the benefit of the > > security area directors. Document editors and WG chairs should > > treat these comments just like any other last call comments. > > Thank you for your review and comments. Hi Dan. Thanks for quick response. > > This document adds support for salted password databases to EAP-pwd > > (RFC5931). I believe the document is Not Ready for the following > > reasons: > > > > 1) The introduction and security considerations fails to > > acknowledge that password salting is not sufficient to protect > > against real-world password recovery attacks. Iterative constructs > > are needed. This knowledge is old, PBKDF2/RFC2898 (which is one > > standard technique to address the problem) was published in 2000 > > and has been widely deployed since then. The document should > > mention this aspect. There have been many successful attacks > > against pure-salted password databases in the real world, for > > example: https://en.wikipedia.org/wiki/2012_LinkedIn_hack > > The intent is to support existing databases that RFC 5931 could > not. I guess it deserves to be mentioned in case someone wants to > create a new salted password database. I will add something regarding > real-world attacks to recover passwords given a salted/encrypted > database. Thank you. I believe the experience and understanding in this field is that it is not responsible to publish a document suggesting to use only salted password databases today, or even 10 years ago. Anything in that direction should come with serious warnings that you are doing something that the community believe is a bad idea, combined with guidelines on how to do it properly (PBKDF2/scrypt). It seems we are on the same page here, and the detail is how to get the document to say that. > > 2) Code points for the pre-processing techniques PBKDF2 (RFC > > 2898) and scrypt (RFC 7914) should be added, to support use of best > > security practices. > > Great suggestion, I will add these. Thank you. Some way to encode the PBKDF2/scrypt parameters in the salt field is required, which require some additional specification work. I am happy to review text here. > > 3) There are interop concerns with crypt() when discussion about > > which crypt algorithms (DES, MD5, etc) are to be used is lacking. > > The page <https://en.wikipedia.org/wiki/Crypt_%28C%29> mentions a > > couple of algorithms, but several others exist out there. Consider > > if the server tells the client to use an exotic crypt() schema like > > BSDi or NTHASH, and the client does not support this algorithm. > > The document should discuss the sub-negotiation problem. The > > document should mention what happens when the server choses an > > algorithm the client doesn't support. The document should > > recommend that servers use widely-implemented schemas, like DES, > > md5, or sha256. > > Yes, there needs to be something to deal with failure of a client > to support a server's crypt algorithm. Since this is not a dynamic > sort of thing-- oh, you don't like BSDi, how about sha256?-- so I > think the only option is failure, but it should be mentioned. Agreed. Failure appears like the only option, but it should be made clear. It should also be made clear that servers ought to pick common algorithms to avoid this problem, even though the strategy isn't 100%. > > 4) Introducing a new pre-processing technique like > > OpaqueString+SHA1 or OpaqueString+crypt() add complexity. As far > > as I understand, there are no password databases with > > OpaqueString-processed passwords which are hashed with SHA-1 or > > crypt out there today. Thus there is no interop argument for > > introducing the methods. Please confirm that the intention is to > > introduce these methods as new ideas. Then let me suggest that you > > only describe OpaqueString+SHA256 and skip OpaqueString+SHA1, > > OpaqueString+SHA512, OpaqueString+crypt. This reduces complexity > > and does not cause a reduction of security. > > Actually no, these aren't for new databases. There has to be some > canonical way to deal with "international" character sets. RFC 5931 > used to refer to SASLprep but that's been obsoleted. So I MUST now > refer to OpaqueString. > > I went to the OpaqueString tutorial a couple of IETFs ago and asked > whether passwords treated with SASLprep would map 1:1 to passwords > treated with OpaqueString and the answer I got was something like, > "uhm, well, I'm not sure. I think so." So the expectation is that a > passphrase of "Eu amo São Paulo" (with the problematic diacritical) > in an existing database created by SASLprep could be used with salted > EAP-pwd and the corresponding OpaqueString pre-processing technique. > And that means that every non-internationalized salting technique > needs an OpaqueString version, including SHA1 and crypt. I do not understand. Are you saying that you know of implemented/deployed password databases that uses PRECIS OpaqueString processed passwords that are salted and then hashed, the way described by your document? This would surprise me greatly, but of course it is not impossible. In my experience, people who are aware of PRECIS/OpaqueString for password processing are aware of iterated password processing algorithms like PBKDF2. I would say more people are aware of PBKDF2 than PRECIS/OpaqueString. Or are you saying that your intent is to support existing deployed SASLprep prepared databases? Do you know of any that use each of SHA1, SHA256, SHA512 or crypt()? Or was the addition of all algorithms for completness? SASLprep and OpaqueString are not the same algorithm, and they don't map 1:1, otherwise there wouldn't be any need to have two algorithms. If the intent is to support existing salted+hashed password databases with SASLprep, refering to OpaqueString won't work. This may be a similar situation as with iterated vs non-iterated algorithms. You could include SASLprep for legacy reasons, but recommend use of OpaqueString going forward. Same as including SHA1(salt|password) for legacy but recommend use of PBKDF2/scrypt going forward. > > Further, password databases with HTTP Digest MD5 passwords are > > widely used. For added legacy compatibility, consider support it > > too. This is not a show stopper, but failure to mentioning it in > > the context of deployed password databases appears to me like an > > elephant in the room. Where there conscious reasons for not > > including it? It may be worth stating those reasons in the > > document, if that is the case. > > Good suggestion. I'll add MD5 too. Refer to RFC 7616 for details, it is not as easy as MD5(salt|password), and the document covers SHA-256 and SHA-512/256 too. If you add this, you will need to discuss what the username and realm should be. I don't think you must add this if you have no direct use for it, but acknowledging this widely deployed salted password database appears relevant. It is more important to add PBKDF2/scrypt in my opinion. Thanks, /Simon
- [secdir] secdir review of draft-harkins-salted-ea… Simon Josefsson
- Re: [secdir] secdir review of draft-harkins-salte… Dan Harkins
- Re: [secdir] secdir review of draft-harkins-salte… Simon Josefsson
- Re: [secdir] secdir review of draft-harkins-salte… Kathleen Moriarty
- Re: [secdir] secdir review of draft-harkins-salte… Stefan Winter
- Re: [secdir] secdir review of draft-harkins-salte… Simon Josefsson
- Re: [secdir] secdir review of draft-harkins-salte… Simon Josefsson
- Re: [secdir] secdir review of draft-harkins-salte… Dan Harkins
- Re: [secdir] secdir review of draft-harkins-salte… Simon Josefsson
- Re: [secdir] secdir review of draft-harkins-salte… Dan Harkins