Re: [dtn] [EXT] I-D Action: draft-ietf-dtn-bpsec-cose-01.txt

All,
This last change to the BPSec COSE Context document addresses the only two 
open issues in the gitlab project. The substantive change is to modify the AAD 
parameter and definition to allow a single BPSec block to include any other 
combination of blocks in the bundle as AAD. In this way a single MAC or 
signature can verify the presence and/or contents of any number of blocks. 
This allows disparate use cases all the way between signing just the primary 
block (e.g. authenticate the bundle itself) to encrypting or signing the 
payload block while ensuring that a set of companion blocks (e.g. data labels, 
flow labels) are present and unchanged.

One side effect that this kind of behavior brings to light is the fact that 
these kinds of restrictions are not visible to middleboxes (e.g. routers or 
gateways) without deep inspection of security blocks. Does it sound helpful to 
use block flags [1] to signal to handlers of the bundle that either:
 * The block cannot be modified (because it is covered by some security 
operation)
 * The block-type-specific data cannot be decoded (because it was encrypted, 
or potentially compressed/modified by some future block)

This would not affect this COSE Context document; it would be a separate thing 
to discuss. I think there is value in informing middleboxes of this kind of 
information without requiring it to deeply inspect the bundle (decode any 
block-type-specific data) especially because some sources of this information 
require specific order of block processing to obtain and also requires the 
ability to handle not-yet-defined security contexts (or other future block 
types that impose these constraints).

Thoughts and feedback are welcome,
Brian S.

[1] 
https://www.iana.org/assignments/bundle/bundle.xhtml#block-processing-control

> -----Original Message-----
> From: dtn <dtn-bounces@ietf.org> On Behalf Of internet-drafts@ietf.org
> Sent: Thursday, June 1, 2023 1:02 PM
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> Subject: [EXT] [dtn] I-D Action: draft-ietf-dtn-bpsec-cose-01.txt
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> A New Internet-Draft is available from the on-line Internet-Drafts 
> directories.
> This Internet-Draft is a work item of the Delay/Disruption Tolerant
> Networking (DTN) WG of the IETF.
>
>    Title           : DTN Bundle Protocol Security (BPSec) COSE Context
>    Author          : Brian Sipos
>    Filename        : draft-ietf-dtn-bpsec-cose-01.txt
>    Pages           : 45
>    Date            : 2023-06-01
>
> Abstract:
>    This document defines a security context suitable for using CBOR
>    Object Signing and Encryption (COSE) algorithms within Bundle
>    Protocol Security (BPSec) integrity and confidentiality blocks.  A
>    profile for COSE, focused on asymmetric-keyed algorithms, and for
>    PKIX certificates are also defined for BPSec interoperation.
>
> The IETF datatracker status page for this Internet-Draft is:
> https://datatracker.ietf.org/doc/draft-ietf-dtn-bpsec-cose/
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> https://www.ietf.org/archive/id/draft-ietf-dtn-bpsec-cose-01.html
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> A diff from the previous version is available at:
> https://author-tools.ietf.org/iddiff?url2=draft-ietf-dtn-bpsec-cose-01
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Re: [dtn] [EXT] I-D Action: draft-ietf-dtn-bpsec-cose-01.txt

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