Subject: [Emu] Proposed way forward: emu and channel bindings

From: Sam Hartman <[email-masked]>
Date: Fri, 14 Sep 2007 08:55:26 -0400

Hi.

One of EMU's goals is to produce methods that meet requirements of RFC
4962 and hopefully the EAP keying framework.

I've been a bit concerned about what you are going to do about channel
bindings.  It seems clear that EAP channel bindings are not mature
enough that we want to require all your methods support
them--especially not the EAP TLS draft that is on my plate now.
However channel bindings seem important for meeting the RFC 4962
requirements to authenticate all parties and limit the key scope.

So, how do we proceed?
I was discussing the issue with Tim, Russ and Jari.
They had what I think is good advice.

I'm going to ask that you show that it would be possible to extend any
method you send to me to support channel bindings in an interoperable
manner in the future.  I would want to understand that it is possible
to make it work with old clients or old EAP servers.  Once I'm
convinced it is possible to add in the future, I will be OK on the
channel bindings issue.

does this seem reasonable?

Sam Hartman
Security Area Director

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From: Yoshihiro Ohba <[email-masked]>
Date: Fri, 14 Sep 2007 09:09:52 -0400

It is possible to add, at later stage, an interopelable channel
bindings mechanism that can work with old clients and servers, by
using EAP-EXT method with running any EAP authentication method inside
it.

Yoshihiro Ohba

---

From: Sam Hartman <[email-masked]>
Date: Fri, 14 Sep 2007 10:20:10 -0400

>>>>> "Yoshihiro" == Yoshihiro Ohba <[email-masked]> writes:

    Yoshihiro> It is possible to add, at later stage, an interopelable
    Yoshihiro> channel bindings mechanism that can work with old
    Yoshihiro> clients and servers, by using EAP-EXT method with
    Yoshihiro> running any EAP authentication method inside it.

I understand this approach is possible.  One of the reasons I'm not
asking emu to solve the channel bindings problem now is that the IETF
may choose to adopt this approach.

However I am not willing to depend on this approach now.

---

From: "Joseph Salowey \(jsalowey\)" <[email-masked]>
Date: Sun, 16 Sep 2007 22:21:57 -0700

Hi Sam,

This does sound reasonable.  Some questions for the group to solidify
what it means to support channel bindings:

1) Is encryption required or is integrity protection enough.  

In my opinion integrity protection should be sufficient since channel
bindings communicate parameters that are visible from the lower layer.  

2) Should EAP channel bindings be sent from the peer to server, server
to peer, or both.  

It seems that it would be more deployable to support peer to server.  It
probably would be desirable to support both.

3) How much data is necessary to carry?

Would 100 - 200 bytes be sufficient? 

Thanks,

Joe

> -----Original Message-----
> From: Sam Hartman [mailto:[email-masked]] 
> Sent: Friday, September 14, 2007 5:55 AM
> To: [email-masked]
> Subject: [Emu] Proposed way forward: emu and channel bindings
> 
> 
> 
> Hi.
> 
> I've been a bit concerned about what you are going to do 
> about channel bindings.  It seems clear that EAP channel 
> bindings are not mature enough that we want to require all 
> your methods support them--especially not the EAP TLS draft 
> that is on my plate now.
> However channel bindings seem important for meeting the RFC 
> 4962 requirements to authenticate all parties and limit the key scope.
> 
> 
> So, how do we proceed?
> I'm going to ask that you show that it would be possible to 
> extend any method you send to me to support channel bindings 
> in an interoperable manner in the future.  I would want to 
> understand that it is possible to make it work with old 
> clients or old EAP servers.  Once I'm convinced it is 
> possible to add in the future, I will be OK on the channel 
> bindings issue.
>

---

From: Sam Hartman <[email-masked]>
Date: Mon, 17 Sep 2007 17:43:41 -0400

>>>>> "Joseph" == Joseph Salowey (jsalowey) <[email-masked]> writes:

    Joseph> 2) Should EAP channel bindings be sent from the peer to
    Joseph> server, server to peer, or both.

I hope you can avoid needing to answer this question as it could be a
bit tricky.