Subject: [Ietf-krb-wg] Where are we with the preauth nonce discussion

From: Sam Hartman <[email-masked]>
Date: Mon, 01 Aug 2011 09:49:35 -0400

I'm hoping that discussion continues to a point where we reach consensus
by the time IETF LC starts.
Have things died down because people are in agreement? If so, I missed
the agreement. Or did the ball get dropped?
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From: Greg Hudson <[email-masked]>
Date: Mon, 01 Aug 2011 10:35:39 -0400

> by the time IETF LC starts.

I was going to propose text, but then you wrote something which made me
think I should wait until IETF last call.

Based on the last message from Gareth
(https://lists.anl.gov/pipermail/ietf-krb-wg/2011-July/009492.html) I
think we have agreement to add a timestamp to PA-OTP-ENC-REQUEST and use
it in 2-pass mode instead of PA-ENC-TS-ENC.  I'll propose specific text
later in the day.

(I still feel like the nonce and PA-OTP-ENC-REQUEST are unnecessary
complexity in the most common expected use case, which is where the
client and reply key are equal to the armor key.  But I think I am too
late in the process to be trying to remove complexity at that level of
detail.)

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From: Sam Hartman <[email-masked]>
Date: Mon, 01 Aug 2011 11:15:18 -0400

>>>>> "Greg" == Greg Hudson <[email-masked]> writes:

    Greg> On Mon, 2011-08-01 at 09:49 -0400, Sam Hartman wrote:
    >> I'm hoping that discussion continues to a point where we reach
    >> consensus by the time IETF LC starts.

    Greg> I was going to propose text, but then you wrote something
    Greg> which made me think I should wait until IETF last call.

    Greg> Based on the last message from Gareth
    Greg> (https://lists.anl.gov/pipermail/ietf-krb-wg/2011-July/009492.html)
    Greg> I think we have agreement to add a timestamp to
    Greg> PA-OTP-ENC-REQUEST and use it in 2-pass mode instead of
    Greg> PA-ENC-TS-ENC.  I'll propose specific text later in the day.

Note that I see a higher bar for changing the ASN.1 structure at this
point than I see for changing the form of the nonce field.  In
particular I'll want to hear from all the folks who have indicated
implementation work in the past if we're going to change the module
post-WG-LC.
I think that means the folks from Cybersafe, Linus and Redhat.
Am I missing any parties?
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From: Greg Hudson <[email-masked]>
Date: Tue, 02 Aug 2011 01:43:56 -0400

On Mon, 2011-08-01 at 11:15 -0400, Sam Hartman wrote:
> point than I see for changing the form of the nonce field.

Well, in that case, I suggest changing the text in section 4.1 from:
        
        This nonce string MUST be as long as the longest key length of
        the symmetric key types that the KDC supports and MUST be chosen
        randomly.

to

        This nonce string MUST contain a randomly chosen component at
        least as long as the longest key length of the symmetric key
        types that the KDC will include PA-ETYPE-INFO2 entries for in
        the reply.

The KDC can then compose a nonce out of a random component and a
timestamp.

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From: Sam Hartman <[email-masked]>
Date: Tue, 02 Aug 2011 07:06:17 -0400

OK, I'd like to hear comments on this proposed change. Even if you've
expressed support for similar concepts in the past, express support now.
We'll count Greg in favor without another message from him.:-)

Sam Hartman
Kerberos Working Group Co-Chair
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From: <[email-masked]>
Date: Thu, 4 Aug 2011 07:04:20 -0400

I am happy with the proposed change.

> -----Original Message-----
> From: [email-masked] [mailto:ietf-krb-wg-
> [email-masked]] On Behalf Of Sam Hartman
> Sent: 02 August 2011 12:06
> To: Greg Hudson
> Cc: [email-masked]; Sam Hartman
> Subject: Re: [Ietf-krb-wg] Where are we with the preauth nonce
> discussion
>

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From: Greg Hudson <[email-masked]>
Date: Thu, 04 Aug 2011 10:30:46 -0400

Apologies for muddling up the process, but after looking at the
definition of the client key a bit further, I came up with a simpler way
to express the length requirement:

        This nonce string MUST contain a randomly chosen component at
        least as long as the armor key length.

The client key is going to be either the armor key, or KRB-FX-CF2 of the
armor key and another key of the same type.  So there shouldn't be any
need to talk about the lengths of other key types.  This text should be
much simpler for implementors.

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From: Sam Hartman <[email-masked]>
Date: Thu, 04 Aug 2011 10:52:48 -0400

>>>>> "Greg" == Greg Hudson <[email-masked]> writes:

    Greg> Apologies for muddling up the process, but after looking at
    Greg> the definition of the client key a bit further, I came up with
    Greg> a simpler way to express the length requirement:

    Greg>         This nonce string MUST contain a randomly chosen
    Greg> component at least as long as the armor key length.

Speaking as an individual, I support this wording assuming Gareth has no
objection.

Speaking as a chair, I'd like to hear from Gareth  and at least one
other proponent.
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From: <[email-masked]>
Date: Mon, 8 Aug 2011 04:19:19 -0400

I have no objections to this change.

> From: Sam Hartman [mailto:[email-masked]]
> Sent: 04 August 2011 15:53
> To: Greg Hudson
> Cc: Richards, Gareth; [email-masked]; [email-masked]

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From: "Henry B. Hotz" <[email-masked]>
Date: Mon, 8 Aug 2011 10:38:13 -0700

+1  (Much more to the point.)

>> Speaking as a chair, I'd like to hear from Gareth  and at least one

------------------------------------------------------
The opinions expressed in this message are mine,
not those of Caltech, JPL, NASA, or the US Government.
[email-masked], or [email-masked]

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From: Linus Nordberg <[email-masked]>
Date: Wed, 17 Aug 2011 18:38:35 +0200

Sam Hartman <[email-masked]> wrote
Thu, 04 Aug 2011 10:52:48 -0400:

|     Greg>         This nonce string MUST contain a randomly chosen
|     Greg> component at least as long as the armor key length.
| 
| Speaking as an individual, I support this wording assuming Gareth has no
| objection.
| 
| Speaking as a chair, I'd like to hear from Gareth  and at least one
| other proponent.

I like this change.

---

From: Linus Nordberg <[email-masked]>
Date: Wed, 17 Aug 2011 22:08:46 +0200

|     Greg> Apologies for muddling up the process, but after looking at
|     Greg> the definition of the client key a bit further, I came up with
|     Greg> a simpler way to express the length requirement:
| 
|     Greg>         This nonce string MUST contain a randomly chosen
|     Greg> component at least as long as the armor key length.
| 
| Speaking as an individual, I support this wording assuming Gareth has no
| objection.
| 
| Speaking as a chair, I'd like to hear from Gareth  and at least one
| other proponent.

I like this change.