[Last-Call] Opsdir last call review of draft-ietf-suit-mud-06

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Reviewer: Susan Hares
Review result: Has Issues

Overall comment:
Qualifications: I am not an expert on SUIT implementations or an operator of
networks using SUIT. Therefore, my issues may be covered by some general
security considerations in a document I am not aware of.

General comments to authors:  This feature is clearly described in this
document. Brendan and Hannes did an excellent job of writing the document.

Security/Operational Issues:

The security of MUD URLs may move the attacks from individual devices to the
MUD Manager. (Instead of a single lemming going over the cliff, a MUD manager
may send many lemmings over the cliff). This document does not seem to consider
the operational issues in the MUD Manager or provide mechanisms on how to check
for these attacks (e.g. Yang modules with operational state).

1. An Attack on the MUD Manager can shut down or subvert the entire network.

It is not clear how the operator knows an attack on the MUD Manager is happening
or occurred. If the MUD Manager pulls in broken SUIT manifests and
then pulls in broken software/firmware based on the SUIT manifests
how does the operator know?  In other words what device watches
that the MUD Manager is not subverted via a management protocol?

I do not see any operational state in the MUD Yang module [RFC8620 section 2.1]
It would seem natural to have some operational state in the MUD Manager reports
manifest state. Yang's notif protocols could report any manifest state change
(over secure TLS connections) to a centralized security server.

2. For secure URLs transmitted by 802.1X with certificates,
Why are these not a "double-check" on the validity of the software?

Again, it would seem natural to utilize these secure certificates as
"double-checks" on the MUD Manager being "in-sync"  with the devices.

3. As a less secure double-check on being "in-sync", is the reporting of
 MUD URL sent via MUD Devices via DHCP or LLDAP that is not what is in the
 manifest.

These reporting features are useful in transition scenarios as well as
detecting attacks on the MUD manager.

Editorial nits:

1. section 1, last paragraph, sentence 2

Old text: /can get/
New text: /has/

English grammar

2. Just for my sanity, would you check the following text is correct

$$SUIT_severable-members-extensions //= (
  suit-manifest-mud => bstr .cbor SUIT_MUD_container
)
It appears you are looking to define a CBOR Type for the
the SUIT_MOD_container is defined in the text.

What I think I'm missing is the .cbor value for SUIT.
It looks correct, but I could  not derive this from draft-ietf-suit-manifest-24:

SUIT_Severable_Manifest_Members = (
  ? suit-payload-fetch => bstr .cbor SUIT_Command_Sequence,
  ? suit-install => bstr .cbor SUIT_Command_Sequence,
  ? suit-text => bstr .cbor SUIT_Text_Map,
  * $$SUIT_severable-members-extensions,
)

And your IANA definitions of:

IANA is requested to add a new value to the SUIT envelope elements registry
created with [I-D.ietf-suit-manifest]: Label: TBD2 [[Value allocated from the
standards action address range]]

Name: Manufacturer Usage Description (MUD)
Reference: [[TBD: This document]]

Again, this may be due to my incomplete understanding.
This is why this is a NIT rather than an Issue.



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