13. Security Considerations

As this document describes a security protocol, many aspects of security interest are described in the relevant sections. This section points out issues which may not be obvious in other sections.

Cache Validation: In order for a collection of caches as described in Section 11 to guarantee a consistent view, they need to be given consistent trust anchors to use in their internal validation process. Distribution of a consistent trust anchor is assumed to be out of band.

Cache Peer Identification: The router initiates a transport connection to a cache, which it identifies by either IP address or fully qualified domain name. Be aware that a DNS or address spoofing attack could make the correct cache unreachable. No session would be established, as the authorization keys would not match.

Transport Security: The RPKI relies on object, not server or transport, trust. That is, the IANA root trust anchor is distributed to all caches through some out-of-band means and can then be used by each cache to validate certificates and ROAs all the way down the tree. The inter-cache relationships are based on this object security model; hence, the inter-cache transport can be lightly protected.

However, this protocol document assumes that the routers cannot do the validation cryptography. Hence, the last link, from cache to router, is secured by server authentication and transport-level security. This is dangerous, as server authentication and transport have very different threat models than object security.

So the strength of the trust relationship and the transport between the router(s) and the cache(s) are critical. You're betting your routing on this.

While we cannot say the cache must be on the same LAN, if only due to the issue of an enterprise wanting to offload the cache task to their upstream ISP(s), locality, trust, and control are very critical issues here. The cache(s) really SHOULD be as close, in the sense of controlled and protected (against DDoS, MITM) transport, to the router(s) as possible. It also SHOULD be topologically close so that a minimum of validated routing data are needed to bootstrap a router's access to a cache.

The identity of the cache server SHOULD be verified and authenticated by the router client, and vice versa, before any data are exchanged.

Transports which cannot provide the necessary authentication and integrity (see Section 9) must rely on network design and operational controls to provide protection against spoofing/corruption attacks. As pointed out in Section 9, TCP-AO is the long-term plan. Protocols which provide integrity and authenticity SHOULD be used, and if they cannot, i.e., TCP is used as the transport, the router and cache MUST be on the same trusted, controlled network.