Re: [Emu] Working Group Last Call for draft-ietf-emu-tls-eap-types
Mohit Sethi <mohit@iki.fi> Mon, 04 July 2022 20:04 UTC
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Date: Mon, 04 Jul 2022 23:04:04 +0300
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To: Alan DeKok <aland@deployingradius.com>
Cc: Joseph Salowey <joe@salowey.net>, EMU WG <emu@ietf.org>
References: <5585_1654705009_62A0CB71_5585_2706_1_CAOgPGoCmE-dQ_frOp=vV0Oc=u_=k+QZ3W9JOo_NOwFijiQppqg@mail.gmail.com> <751ee6f5-f06a-9709-4122-2f11304b97f6@iki.fi> <23836_1656962904_62C33F56_23836_2555_1_30AA13C2-D030-4D2D-B17C-654DFBEFACD2@deployingradius.com>
From: Mohit Sethi <mohit@iki.fi>
In-Reply-To: <23836_1656962904_62C33F56_23836_2555_1_30AA13C2-D030-4D2D-B17C-654DFBEFACD2@deployingradius.com>
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Subject: Re: [Emu] Working Group Last Call for draft-ietf-emu-tls-eap-types
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Hi: On 7/4/22 22:28, Alan DeKok wrote: > On Jul 4, 2022, at 2:56 PM, Mohit Sethi <mohit@iki.fi> wrote: >> Some late last call comments: >> >> 1. For PEAP and TTLS, it is no longer possible to use client certificates without phase 2 authentication. Does the same restriction apply to TEAP. I think it would make sense to add an explanation on why this was done? > I think it should be done for TEAP, too. The text could mirror TEAP: > > The practice of using client certificates with no "inner tunnel" method is forbidden when TEAP > is used with TLS 1.3. If there is a requirement to use client > certificates with no inner tunnel methods, then EAP-TLS should be used > instead of TEAP. > >> How about using server certificate in phase 1 and client certificate in phase 2 (with no further inner methods)? TEAP supports such behavior for TLS 1.2 to hide client identity? > My inclination is to forbid that for TLS 1.3. However, TEAP can do multiple inner method authentication (host + user), unlike TTLS and PEAP. Which means that it is possible to do TEAP with inner EAP-TLS, and then also inner "other method". > > Perhaps the document could just say it's NOT RECOMMENDED to do TEAP with only inner EAP-TLS. > >> Would it not be better to simply mandate at least one NewSessionTicket message? > I can see situations where resumption isn't used. You don't have to use resumption. You just need to send NewSessionTicket as a protected success indication. I thought the reason for for forbidding use of client certificates without phase 2 authentication was lack of protected success indication. Perhaps there is some other reason? This is why I wrote in my original comment: "I think it would make sense to add an explanation on why this was done? ". > >> I can think of a TTLS deployment where some peers only authenticate with client certificates while other peers authenticate with client certificates and one-time passwords in phases 2. Depending on the type of authentication, peers are put in different VLANs. > I'm not sure how that affects NewSessionTicket? > > One-time passwords in phase 2 are a significant issue with EAP methods. Where people have tried to deploy them, there are many issues. They just don't work in practice for a host of reasons. One-time password was only an example. Perhaps a wrong one. I just wanted to highlight that we were forbidding TTLS/PEAP and now TEAP deployments from using client certificates without phase 2 authentication. But there can be deployments where some peers use client certificates without phase 2 authentication while other peers use client certificates with additional phase 2 authentication (password, etc.). > > The simplest one is that the supplicant caches the inner identity, and re-uses it when the WiFi signal is lost / re-gained. While a NewSessionTicket will help here, it won't always help. There are situations where the end user will be prompted again (sometimes repeatedly!) in a short period of time. > > I would suggest that one-time passwords in phase 2 are NOT RECOMMENDED, unless the passwords can be automatically entered without human intervention. > >> 2. I don't think this makes sense: >> >> >>> Implementations SHOULD NOT use inner identities which contain an NAI >>> realm. >>> >> >>> if the inner identity does contain an NAI realm, the inner >>> realm SHOULD be either an exact copy of the outer realm, or be a >>> subdomain of the outer realm. >>> >> Eliot would agree that there are all kinds of IoT uses cases where the outer NAI has a realm of the device manufacturer while the inner NAI has a realm of the enterprise where the device is installed (or vice-versa). > I think that's best described as "surprising" from an EAP standpoint. The outer NAI is overwhelmingly used to determine routing, as with Eduroam. Having different outer / inner NAIs means that the routing is broken: > > * packets get sent to "example.com" > * the example.com server sees authentication requests for "example.net", and says "that's not me, why did you send these packets to me?" > > For the IoT case, we would never route the authentication packets to the device manufacturer. So it's not clear to me why the outer NAI has to contain that value. > > > If this is a necessary use-case, I would suggest requiring that these authentications MUST be handled locally, with no routing. > > This issue is why I was proposing to define the outer NAI realm of "@eap.arpa". Those packets are clearly labelled as "site local", and are not forwarded. > >> I also don't understand why this is bad: >> >> >>> For example, if a user >>> has an inner identity of >>> "user@example.com" >>> , then it generally makes >>> no sense to have an outer identity of "@example.org". >>> >> Most university guidelines for eduroam recommend exactly what you are trying to prevent. For example: https://www.aalto.fi/en/services/installation-instructions-for-eduroam says: > I haven't seen this recommendation in most universities. My discussions with the eduroam people make me believe that such configurations are in fact discouraged by the wider Eduroam recommendations. > >>> Review your settings in the Wi-Fi Settings window: >>> Wireless security: WPA & WPA2 Enterprise >>> Authentication: Protected EAP (PEAP) >>> Anonymous identity: anonymous@aalto.fi >>> CA certificate: ca-certificates.crt >>> PEAP version: Automatic >>> Inner authentication: MSCHAPv2 >>> Username: firstname.lastname@aalto.fi >>> Password: <your Aalto password> > Which is using the same realm for both outer / inner identities. So I don't understand why there's an issue. The draft currently says that inner identity should not have a realm. However, the example above, and many other guidance documents I have seen do use a realm in the inner identity. --Mohit > > Incidentally the recommendation violates the RFCV 7542 recommendation to just use @aalto.fi as the outer NAI. i.e. an outer *user* portion of the NAI is not needed. But both *realms* are identical for inner and outer NAIs. > >> @Joe: I am not confident that this section has had sufficient review. I am generally not comfortable with the text. This draft was anyways about TLS 1.3 for TEAP/PEAP/TTLS etc. I think this is going way beyond what the draft originally was trying to solve. > This section describes wide-spread practice in the community for about a decade. > > While the updated text is not specific to TLS 1.3 and TTLS / PEAP / FAST / TEAP, it does give guidelines to users of TTLS / etc. for TLS 1.3. WhichI think is critical for success in real-world use-cases. > >> 3. Section 2.4 says: >> >>> the response from the EAP peer MUST be either >>> EAP-Success or EAP-Failure. >>> >> I though the Success and Failure messages are sent by the EAP server? > That was a typo, already addressed in a previous comment. > >> 4. Section 4 says: >> >> >>> If either peer or server instead >>> initiates an inner tunnel method >>> >> I thought you have mandated the use of an inner tunnel method? So why the 'if'? > Resumption doesn't use an inner tunnel method. So the "if" is necessary. > > Alan DeKok. >
- [Emu] Working Group Last Call for draft-ietf-emu-… Joseph Salowey
- Re: [Emu] Working Group Last Call for draft-ietf-… Alan DeKok
- Re: [Emu] Working Group Last Call for draft-ietf-… Russ Housley
- Re: [Emu] Working Group Last Call for draft-ietf-… Alan DeKok
- Re: [Emu] Working Group Last Call for draft-ietf-… Russ Housley
- Re: [Emu] Working Group Last Call for draft-ietf-… Alan DeKok
- Re: [Emu] Working Group Last Call for draft-ietf-… Mohit Sethi
- Re: [Emu] Working Group Last Call for draft-ietf-… Alan DeKok
- Re: [Emu] Working Group Last Call for draft-ietf-… Mohit Sethi
- Re: [Emu] Working Group Last Call for draft-ietf-… Alan DeKok