Re: [secdir] SecDir review of draft-ietf-xmpp-3920bis-17
Yaron Sheffer <yaronf.ietf@gmail.com> Tue, 02 November 2010 11:10 UTC
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Date: Tue, 02 Nov 2010 13:10:40 +0200
From: Yaron Sheffer <yaronf.ietf@gmail.com>
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To: Peter Saint-Andre <stpeter@stpeter.im>
References: <4CC9503D.2000809@gmail.com> <4CCBA7A9.7030506@stpeter.im> <4CCE87A5.80701@gmail.com> <4CCF20E7.30401@stpeter.im>
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Cc: draft-ietf-xmpp-3920bis.all@tools.ietf.org, iesg@ietf.org, XMPP <xmpp@ietf.org>, secdir@ietf.org
Subject: Re: [secdir] SecDir review of draft-ietf-xmpp-3920bis-17
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Hi Peter, please see my comments in-line. I have removed already-closed issues. Thanks, Yaron On 11/01/2010 10:19 PM, Peter Saint-Andre wrote: > On 11/1/10 3:25 AM, Yaron Sheffer wrote: > > Hi Peter, > > > > Responding to the last part. Thanks for a constructive discussion. > > > >>> - 13.7.1.1: and most important, is the "relying party" (e.g. the > client) > >>> required to check all these rules and fail validation if any of > them is > >>> not met? > >> > >> As I understand it from my conversations with Sean when we were adding > >> this text, these rules are not set in stone within RFC 5280 and > >> therefore need to be specified by any technology that reuses PKIX. Our > >> intent was that CAs would conform to these rules, not necessarily that > >> replying parties would necessarily fail on validation if the rules were > >> violated. Here again I'll check with Sean. > >> > > Please do. In particular, trusting a non-CA to sign certificates seems > > to contradict the spirit of PKIX policies. > > Yes, I now see that you are right (see previous warning about lack of > coherence). I've provisionally updated the relevant paragraph of Section > 13.7.2 as follows, breaking it into bullets for easier readability: > > ### > > For both server certificates and client certificates, the validating > entity MUST do the following: > > 1. Attempt to verify the integrity of the certificate. > > 2. Attempt to verify that the certificate has been properly signed > by the issuing Certificate Authority. > > 3. Attempt to validate the full certification path. > > 4. Check the rules for end entity public key certificates and > certification authority certificates specified under > Section 13.7.1.1 for the general case and under either > Section 13.7.1.2 or Section 13.7.1.2 for XMPP server or client > certificates, respectively. > > 5. Check certificate revocation messages. > > If any of those validation attempts fail, either entity MAY choose to > unilaterally terminate the session. > > ### > This is all fine, other than the last sentence. There's little security value (or performance value, for that matter) in "MUST check, but only MAY choose to fail". With possible minor exceptions, these rules are all security-critical. > > >>> - 13.7.2: a silly question, but anyway: where do you say that the > >>> client's cert is correlated with the client's JID, as it appears > in the > >>> From line (when setting up the original stream and/or when > setting the > >>> stream anew after TLS negotiation)? > >> > >> Few clients include the 'from' address on the stream header and we're > >> not actively working to make sure they do, because what really matters > >> is that the client authenticates using the credentials of a registered > >> account. > >> > > Ahem, the client's 'from' attribute is a SHOULD (4.6.1). > > It is, but that's in an effort to move people in the right direction. > This matter was very unclear in RFC 3920. > > >>> And vice versa, for the server cert > >>> and the client's To header. > >> > >> For s2s communication, in essence (and using the terms of [TLS-CERTS]) > >> the initiating entity sets its reference identifier to the 'to' address > >> it communicates in the initial stream header, and the receiving entity > >> sets its reference identifier to the 'from' address communicated by the > >> initiating entity in the initial stream header (i.e., the 'from' > address > >> is the identity that the initiating entity is trying to assert). Per > >> recent list discussion Jeff Hodges and I have added a note about > that to > >> our working copy of draft-saintandre-tls-server-id-check. > >> > >> However, I agree that it would be helpful to mention this in > 3920bis, so > >> I propose that we add some text to Sections 13.7.2.1 ("Server > >> Certificates") and 13.7.2.2 ("Client Certificates")... > >> > >> ### > >> > >> 13.7.2.1. Server Certificates > >> > >> For server certificates, the rules and guidelines defined in > >> [TLS-CERTS] apply, with the proviso that the XmppAddr identifier > >> specified under Section 13.7.1.4 is allowed as a reference > >> identifier. > >> > >> The identities to be checked are set as follows: > >> > >> o The initiating entity sets its reference identifier to the 'to' > >> address it communicates in the initial stream header; i.e., > this > >> is the identity it expects the receiving entity to provide in a > >> PKIX certificate. > >> > >> o The receiving entity sets its reference identifier to the > 'from' > >> address communicated by the initiating entity in the initial > >> stream header; i.e., this is the identity that the initiating > >> entity is trying to assert. > >> > >> 13.7.2.2. Client Certificates > >> > >> When an XMPP server validates a certificate presented by a client, > >> there are three possible cases, as discussed in the following > >> sections. > >> > >> The identities to be checked are set as follows: > >> > >> o The client sets its reference identifier to the 'to' address it > >> communicates in the initial stream header; i.e., this is the > >> identity it expects the server to provide in a PKIX > certificate. > >> > >> o The server sets its reference identifier to the 'from' address > >> communicated by the initiating entity in the initial stream > >> header; i.e., this is the identity that the client is trying to > >> assert. > >> > >> ### > > Does that text seem helpful? > Yes, definitely. > >>> - 13.8: "For both confidentiality and authentication with passwords" - > >>> here you don't specify a TLS ciphersuite. > >> > >> RFC 5246 has TLS_RSA_WITH_AES_128_CBC_SHA as the mandatory-to-implement > >> ciphersuite, so that seems appropriate here. Would you recommend > >> something stronger, for example TLS_RSA_WITH_AES_256_CBC_SHA? > >> > > AES-128 is just fine. Actually there are major issues with AES-256. But > > I think this document should specify a ciphersuite, rather than rely on > > RFC 5246 for that. After all you are essentially profiling TLS. > > Done. > > There was talk in the XMPP WG of moving all MTI technologies out of the > core spec so that they could be updated more frequently. Maybe we'll do > that in the next revision cycle (which will result in a much smaller > diff). > I also think it's a good idea.
- [secdir] SecDir review of draft-ietf-xmpp-3920bis… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Florian Zeitz
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Dave Cridland
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Dave Cridland
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Yaron Sheffer
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Yaron Sheffer
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Jeffrey Hutzelman
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Kurt Zeilenga
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Yaron Sheffer
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] SecDir review of draft-ietf-xmpp-392… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Ben Campbell
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Ben Campbell
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Matthew Wild
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Philipp Hancke
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint Andre
- Re: [secdir] [xmpp] SecDir review of draft-ietf-x… Peter Saint-Andre