Re: [secdir] SecDir review of draft-ietf-manet-dlep

["Taylor, Rick (External)" <[e-mail]>]

Hi Paul,

Thank you for the review.  A couple of quick comments:

Did you review draft-ietf-manet-dlep-15 or draft-ietf-manet-dlep-25 (the latest)?  As we have attempted to address the security comments raised by the WG and AD review.

One area we have worked hard on addressing is mandating use of RFC5082 (Generalized TTL Security) on the link between router and modem (See Section 3.1).  As you correctly state, DLEP does not have any inherent security mechanisms, and recommends link-layer security, such as 802.1X/AE, but we do mandate mechanisms to restrict the protocol to run over a single hop.  As you point out, DLEP is a control-plane protocol and does not carry any user data.

We have updated the security considerations (section 12) since draft-15, please can you see if the new verbiage addresses your valid comments?

Many thanks,

Rick Taylor

-----Original Message-----
From: Paul Hoffman [mailto:[e-mail]]
Sent: 16 November 2016 07:02
To: [e-mail]; secdir
Subject: SecDir review of draft-ietf-manet-dlep

Greetings. This is a review of draft-ietf-manet-dlep-15 for the Security Directorate. Please treat these comments as you would any IETF Last Call comments you get.

As I understand it, Dynamic Link Exchange Protocol (DLEP) is a protocol for a router and wireless modem to inform each other about characteristics of the link in order to make better routing decisions.
It runs over UDP and TCP, and is explicitly meant to be only valid on a single L2 hop directly between the modem and router. (Please let me know if I have this wrong!)

There is no security in DLEP. At the end of Section 3, it says:
    DLEP further requires that security of the implementations (e.g.,
    authentication of stations, encryption of traffic, or both) is dealt
    with by utilizing Layer 2 security techniques.  This reliance on
    Layer 2 mechanisms secures all DLEP Messages - both the UDP discovery
    Signals and the TCP control Messages.
Further, there is no mandatory-to-implement L2 security protocol; 802.1X and 802.1AE are mentioned as possibly being used, but neither is required to be implemented.

This, the specified security is pretty weak. It is not clear what advantage an attacker would get by snooping on the DLEP traffic: the values exchanged are pretty easy to determine just by watching the link.
It is also not clear what advantage an attacker would get by impersonating either party or mounting an MITM attack other than degrading the link, which an MITM could do anyways.

This feels like a classic IETF "we don't deal with security and leave it to the layer below us" protocol, which might be acceptable in this case because of the nature of the data being exchanged.

--Paul Hoffman

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