Most of us believe that using cryptographic authentication methods (MD5, etc) for the routing protocols running inside our networks really makes them very secure. Well, not really ..
We have published RFC 6039 that explains how each routing protocol can be exploited despite using the cryptographic authentication mechanisms endorsed by the IETF community.
To cite an example, a simple IP header attack on OSPF or RIP can result in the two adjacent routers bringing down the peering relationship between them. This can, in the worst case, blackhole a substantial amount of data traffic inside the network, something that will certainly not go well with the customers!
So how can an OSPF adjacency be brought down?
OSPF neighbors on the broadcast, NBMA and point-to-multipoint networks are identified by the IP address in the IP header. Because the IP header is not covered by the MAC in the cryptographic authentication scheme as described in RFC 2328, an attack can be made exploiting this vulnerability.
R1 sends an authenticated HELLO to R2. This HELLO is captured and replayed back to R1, changing the source IP in the IP header to that of R2.
R1 not finding itself in HELLO would deduce that the connection is not bidirectional and would bring down the adjacency!
The RFC also discusses some issues that we found with Bidirectional Forwarding Detection (BFD) protocol thats very frequently used in the service provider networks.