> For Microsoft supported protocol suite PEAP/TTLS/TEAP - are you planning to
> find the common method of TLS 1.3 support for all three or you just want to
> release TLS 1.3 support at the same time for all three?
It’s not our intention to try to force the same solution for every method. We
plan to update our implementations at the same time, since we anticipate the
updates will be similar (though not necessarily identical).
>Could this method work? Should we make it more clearly specified? Or should we
>change the protocol to arrive explicitly to the understanding which type
>(MSK/EMSK) of IMSK[j] to use?
You clarification is what I understood the intention of the RFC to be as well,
and makes sense to me. I don’t think there needs to be a protocol update if
this clarification sounds good to all parties. I would welcome Jouni’s thoughts
as the filer of the errata.
Jorge
From: Emu <emu-boun...@ietf.org> On Behalf Of Oleg Pekar
Sent: Wednesday, April 15, 2020 9:25 AM
To: Jorge Vergara <jovergar=40microsoft....@dmarc.ietf.org>
Cc: EMU WG <emu@ietf.org>
Subject: Re: [Emu] draft-dekok-emu-tls-eap-types discussion
Hi Jorge,
For Microsoft supported protocol suite PEAP/TTLS/TEAP - are you planning to
find the common method of TLS 1.3 support for all three or you just want to
release TLS 1.3 support at the same time for all three?
For TEAP errata 5770:
Technically TEAP RFC suggests the implicit method of taking the correct IMSK[j]
and all the subsequent keys after each inner method via negotiation taking
place in Crypto-Binding TLV exchange.
Let's say we are on the inner method number j that supports both MSK and EMSK
and we are server which implementation generates both MSK and EMSK for this
inner method. We generated keys according to the rules below - two sets, for
IMSK[j] derived from inner method EMSK and for IMSK[j] equal to inner method
MSK. Because we don't know whether client implementation supports both MSK and
EMSK.
S-IMCK[0] = session_key_seed
For j = 1 to n-1 do
IMCK[j] = TLS-PRF(S-IMCK[j-1], "Inner Methods Compound Keys",
IMSK[j], 60)
S-IMCK[j] = first 40 octets of IMCK[j]
CMK[j] = last 20 octets of IMCK[j]
So we have two CMK[j] and we create Crypto-Binding TLV with both Compound MAC
for MSK and EMSK. The client sends Crypto-Binding TLV in response and we can
understand from it whether it supports EMSK for this inner method or not. And
here we can decide which version of IMCK[j] to take for this inner method -
derived from EMSK or MSK. This is just not explicitly specified in the RFC.
Could this method work? Should we make it more clearly specified? Or should we
change the protocol to arrive explicitly to the understanding which type
(MSK/EMSK) of IMSK[j] to use?
Thanks
Oleg
On Wed, Apr 8, 2020 at 12:09 AM Jorge Vergara
<jovergar=40microsoft....@dmarc.ietf.org<mailto:40microsoft....@dmarc.ietf.org>>
wrote:
>Microsoft has already said that they won't rev their EAP-TLS implementation
>until they can also rev PEAP.
PEAP/TTLS/TEAP - we (Microsoft) believe all should be addressed at the same
time and will postpone TLS 1.3 support until such a time as we are able to make
the updates together.
>* should the document drop references to TEAP?
> Given Jouni Malinen's comments on implementing TEAP, it may be worth simply
> noting that we're waiting for a TEAP update document
I've reviewed the current errata, and acknowledge their validity, but am not
sure that any of them would impact this document.
The most relevant errata to this document seems to be
https://www.rfc-editor.org/errata/eid5770<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Fwww.rfc-editor.org%2Ferrata%2Feid5770&data=02%7C01%7Cjovergar%40microsoft.com%7C5d8493e9a66549355c6508d7e1599c5f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637225647341455297&sdata=VWIJTVrYLPWmg6JOPrWbiwtUJGHktaFoxGusqldLHrg%3D&reserved=0>.
As noted in the errata, the calculation of keys becomes confusing when methods
export both MSK and EMSK because it is not clearly specified which value
IMCK[j] should take on during the calculation of S-IMCK[j]. The addition of
clarifying information is welcome, but I don't believe this ambiguity currently
prevents a compliant implementation - for example, an implementation could
avoid this ambiguity by choosing to use either the MSK/EMSK exclusively, and
communicating that to the server via the Compound MAC TLV. The server can then
make a policy decision on whether it is accepting of this decision by the
client and follow suit, or reject the client.
The specifics of resolving this particular errata is a digression from my main
point - I believe a clarification can be added to the main TEAP document at a
future time without impacting the contents of this document. Ambiguity about
which IMCK to use in S-IMCK calculation should not impact the definition of the
cryptographic calculations.
On the document contents themselves, I have this review: The key derivation
proposed for TEAP/FAST uses the definition from FAST, which is not identical to
the TEAP derivation. Namely, FAST used MSK[j] in the derivation, but TEAP uses
IMSK[j], which may be equivalent in some cases, but may not in others where the
inner method exports an EMSK.
Specifically, I believe this line of section 2.2 should change from
IMCK[j] = TLS-Exporter("EXPORTER: Inner Methods Compound Keys",
S-IMCK[j-1] | MSK[j], 60)
To
IMCK[j] = TLS-Exporter("EXPORTER: Inner Methods Compound Keys",
S-IMCK[j-1] | IMSK[j], 60)
For TEAP.
Jorge
-----Original Message-----
From: Emu <emu-boun...@ietf.org<mailto:emu-boun...@ietf.org>> On Behalf Of Alan
DeKok
Sent: Friday, April 3, 2020 1:48 PM
To: EMU WG <emu@ietf.org<mailto:emu@ietf.org>>
Subject: [Emu] draft-dekok-emu-tls-eap-types discussion
https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Fdraft-dekok-emu-tls-eap-types-01&data=02%7C01%7Cjovergar%40microsoft.com%7C2c42095edc4e4cd61ce408d7d8106200%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637215437188744711&sdata=ndLp%2FSzsDlX%2FKYx0UR0uf77rHgCjGej4kdZPpywuD9Q%3D&reserved=0<https://nam06.safelinks.protection.outlook.com/?url=https%3A%2F%2Ftools.ietf.org%2Fhtml%2Fdraft-dekok-emu-tls-eap-types-01&data=02%7C01%7Cjovergar%40microsoft.com%7C5d8493e9a66549355c6508d7e1599c5f%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C637225647341455297&sdata=h%2F8Z6wcmGQBYyAbu6TtYM8TDl6VuhzzN3V9w4rxcATo%3D&reserved=0>
I haven't seen much discussion on the document. There are still some open
questions:
* should it be published simultaneously with draft-ietf-emu-eap-tls13?
If so, we need some consensus on this document, and quick.
If not, when do we publish this draft? Microsoft has already said that they
won't rev their EAP-TLS implementation until they can also rev PEAP.
* Should the document simply drop references to FAST?
It looks like the effort has moved to TEAP.
Perhaps we should note that FAST cannot be used with TLS 1.3, and that TEAP
should be used instead
* should the document drop references to TEAP?
Given Jouni Malinen's comments on implementing TEAP, it may be worth simply
noting that we're waiting for a TEAP update document
* Without FAST / TEAP, the document is about 4 pages of text. Is there
anything controversial, missing, etc?
* What are the barriers to adoption and publication?
Alan DeKok.
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