Subject: Re: [core] OSCORE Inner/Outer duplication

From: Göran Selander <[email-masked]>
Date: Fri, 4 May 2018 12:36:15 +0000

Hi Michael,

Thanks for comments. The last sentence of the paragraph you referred to is
a remnant from an older version of the specification. The processing of
Inner and Outer are dependent on the message field in question, so in fact
neither this statement nor the the statement you suggested are valid in
general. We will try to make the description more clear on this point in
the next update.

Thanks
Göran

On 2018-04-28, 19:34, "core on behalf of Michael Richardson"
<[email-masked] on behalf of [email-masked]> wrote:

>
>section 4.0 of draft-ietf-core-object-security ends with:
>
>   An OSCORE message may contain both an Inner and an Outer instance of
>   a certain CoAP message field.  Inner message fields are intended for
>   the receiving endpoint, whereas Outer message fields are used to
>   enable proxy operations.  Inner and Outer message fields are
>   processed independently.
>
>In Outer instance of a CoAP message field will be integrity protected if
>it's
>in the class I message area.  Changes to it would cause the integrity
>check
>to fail and the entire message to be rejected.  Such a message field is
>effectively read-only to proxies.
>
>If the message field instance is in the class U bucket, then it could be
>modified by proxies.  If an instance also exists in the E or I buckets,
>then a receiver could determine if the copy in U bucket had been modified,
>assuming it is reasonable for the message fields to be the same!
>
>I think that the above text in section 4.0 should indicate that the two
>occurances of the fields (Inner and Outer) are semantically different, and
>receivers SHOULD NOT attempt to make sure they are identical.
>
>OSCORE uses this in 4.1.3.5.  No-Response in different ways, for instance.
>
>-- 
>Michael Richardson <[email-masked]>, Sandelman Software Works
> -= IPv6 IoT consulting =-
>
>
>