| Network Working Group | M. Richardson |
| Internet-Draft | SSW |
| Intended status: Informational | March 03, 2014 |
| Expires: September 04, 2014 |
security architecture for 6top: requirements and structure
draft-richardson-6tisch-security-architecture-01
This document details minimal layer-2 requirements for 6top use in industrial settings, and a few options for accomplishing this. The layer-2 mechanism is then extended to provide for per-node authentication and authorization of the node/PCE communications. This internet-draft is intended for later inclusion into the 6tisch architecture document.
This might be the worst written internet draft yet. You have been warned
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The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].
As outlined in [I-D.ietf-roll-security-threats] there are a number of threats in LLNs, and in RPL which are solved if there is layer-2 security. The requirement is therefore to provide keying for the layer-2 security features: encryption and integrity protection.
In addition to serving to protect the routing traffic against attacks, use of the layer-2 access control serves as adminission control to the network. It is therefore part of the layer-2 join process to authenticate the new node, as well as authorize it to join the network. The admission control SHOULD be controlled by autonomic certificates, see section X.
In addition to authorization a node to join the network, the node agree to provide authorization to a PCE in order for the 6top protocol to run. This protocol, described in section X of 6tisch architecture (this) document and in [6top], permits the PCE to program a timeslot schedule into the node.
So, the second part of the 6tisch security requirements is to establish the identities of the the node and the PCE, and to establish an authorization that permits the new node to be programmed by the PCE.
As explained in [I-D.behringer-autonomic-network-framework] the layer-2 identity of the node will be given by a certificate signed by the vendor of the node. The vendor's certificate authority is loaded into the (PANA) Authorization Server, and permits the AS to authenticate the node.
The vendor provides a certificate (chain) to the (PANA) Authorization Server (PAS) attesting to that the PAS is the rightful owner/controller of the node. This permits the node to validate that the network it is joining is the correct network. This process permits the bootstrap of one of the layer-2 security mechanism(s) describe in sections below.
The same set of trust relationships can then permit the PAS to act as an Authorization Server (now, in the context of [I-D.gerdes-core-dcaf-authorize]). The PCE and it's Authorization Manager (AM, again from [I-D.gerdes-core-dcaf-authorize]) can now get a ticket to permit it to write the timeslot schedule. In option 2, below, it also permits updates to the security parameters.
This is an adaptation of the process described in [ZigBeeIP], section and expounded upon in section 6.3: "Network Discovery", 6.4: "Network Selection", and 6.5, "Node Joining". The process is abridged below.
The MAC beacon facility is used. A critical difference in 6tisch from ZigBee IP is that because nodes transmit and receive according to their own schedule, every node is in essence a coordinator. While nodes may sleep a lot, they will not in general be sleep Hosts, from a ZigBee IP point of view, and MLE is not necessary.
Each response to the Beacon is a potential network-joining-parent.
As an option, it may be desireable for this document to define a well known NetworkID.
The PANA payloads MUST be relayed by the chosen network-joining-parent. It is assumed that the PANA Authentication Agent is co-located with the PCE, if there is a PCE.
As per section 8.3.4 of [ZigBeeIP], the PANA process runs over UDP using link-layer addressing. The process is first the PANA initialization (PCI, PAR:S, PAN:S), followed by EAP initialization (EAP-Request, EAP-Response), which negotiates the identity, and then EAP-TLS starts, consisting of (TLS(Start), TLS(ClientHello), TLS(ServerHello), TLS(ServerKeyExchange), TLS(ClientKeyExchange), and TLS(ChangeCipherSpec)).
When the TLS is done, the EAP derives new network security material, and sends it encrypted using the Encr-Encap AVP described in [RFC6786].
QUESTION: can we find a way for the authorization protocol, such as described in draft-gerdes-core-dcaf-authorize-01, to run simultaenously with the authentication system if we assume that the dcaf AS is also the PANA Authentication Server/Agent
In the context of draft-selander-core-access-control, the new node that is joining is the resource server, and the origin client is the PCE.
This is an adaptation of the process described in [HART], section 6.6.3.
In this process, the new node joins using a well-known layer-2 "JOIN" key. It brings up the layer-3, using 6loWPAN Neighbour Discovery to learn of the 6lowpan contexts, and then uses RPL to join a well-known DODAG as a leaf node.
Nodes which have capacity for new joining nodes will respond to the RPL DIS messages. Once connected, the new node uses regular unicasted IP datagrams to contact an Authorization Manager (in the context of [I-D.gerdes-core-dcaf-authorize]). The negotiation with the Authorization Manager (AM) uses the autonomic certificates as described above to establish the trust relationship.
Once the relationship is up, the AM needs to signal the PCE that it has a new authorized node, and the PCE can now (acting as a [I-D.gerdes-core-dcaf-authorize] Client), get a Ticket to update the node.
The PCE then writes both a new timeslot schedule, and also writes new security parameters that permit the node to fully join the network. Appropriate layer-2 keys are updated, as well as any appropriate layer-3 RPL credentials. MLE may be used to establish pair-wise keying, as appropriate to the timeslot schedule.