Security for Routing Protocols
Routing protocols can be subject to threats such as unauthorized updates for either IPv4 or IPv6 routes. Security capabilities have been designed for routing protocols to mitigate unauthorized update threats. Some IPv6 routing protocols rely on similar mechanisms to those in IPv4 for protection, while others have incorporated IPsec for protection. These security mechanisms do not provide end-to-end security for routing protocols across multiple hops, because while they provide integrity assurance for routing protocol messages between nodes, they do not verify the integrity of messages received from other nodes that are not part of a security association. This is a major security concern for EGPs and a somewhat lesser one for IGPs.

RIP for IPv4 uses an MD5-based integrity mechanism; this was removed from RIPng. RIPng offers no integrity assurance features. Per RFC 2080, RIPng leverages IPsec for security. It should be noted that hardware vendors have not incorporated IPsec features as a configuration option, instead relying on native IPv6 IPsec support from the operating platform for protection. RIPng is suitable only for small, private networks where the threat of routing attacks is substantially reduced.

Securing OSPFv2 in a dual stack environment will protect neither the OSPFv3 protocol nor the OSPFv3 routing table. OSPFv2 allows null, password-based, or cryptographic authentication using MD5-based integrity for routing updates. The authentication fields found in OSPFv2 have been removed from the OSPFv3 packet for IPv6, so MD5 is not an authentication option. OSPFv3 offers no integrity assurance features itself and relies on IPsec AH or ESP for authentication, integrity, and confidentiality. Note that OSPFv3 uses unicast and multicast, and IKE does not work with multicast, so the default method is to use manual keying. Since replay protection cannot be provided using manual keying, OSPFv3 messages are vulnerable to replay attacks, which can lead to DoS attacks, Central Processing Unit (CPU) overload, and localized routing loops. IPsec for OSPFv3 is detailed in RFC 4552.

With routing protocols, routing integrity is usually a greater concern than confidentiality. The ESP parameter NULL indicating no encryption is generally regarded to be an acceptable choice for OSPF security.

Both IS-IS and EIGRP support simple MD5-based integrity for protecting IPv6 routing updates, similar to protecting routing updates for IS-IS and EIGRP for IPv4.

The use of BGP as an inter-AS routing protocol means that it can be subject to serious threats. Three mechanisms exist to mitigate threats to BGP. The first is the use of MD5-based integrity to protect routing updates. The second mechanism to mitigate threats to BGP is GTSM (RFC 5082). GTSM is a simple security mechanism for rejecting spoofed BGP messages based on their IP TTL or Hop Limit. The sending BGP router always uses a TTL=255, and the receiving BGP router checks that the TTL has the expected value of 255. Any packets from a remote attacker would have to travel via intervening routers, would have a smaller-than-maximum TTL, and would be dropped on receipt. Note however that a router operating as the endpoint of a tunneling protocol may not decrement the hop count upon receiving packets through the tunnel, so these could conceivably come from anywhere with TTL=255.
The third mechanism to mitigate threats to BGP is IPsec. IPsec key management can use shared secrets or public key certificates, which allow IPsec to offer scalability. GTSM has the lowest overhead of the three mechanisms, and is the easiest to configure. It also offers the least effective protection. The MD5 signature mechanism offers low overhead and effective protection, but it forces administrators to disrupt their BGP sessions at each key update, and it does not scale well. IPsec offers the most effective protection, least disruption, and best scalability. It also imposes the highest overhead (although the
overhead is still small), and it is the most complex mechanism to configure. In summary, using an MD5 checksum is certainly better than nothing, but MD5 itself can be attacked successfully, and most of these methods have no easy ways to change hash functions or even change keys. IPsec is preferable for routing protocols that support its use. All of the above security mechanisms protect against unauthorized insertion or manipulation of routing protocol messages. They do not protect against a corrupted or malfunctioning router that may construct and pass along incorrect routing information. Many approaches
to providing better end-to-end security for BGP have been proposed, but consensus on a single solution has not yet been achieved.

SourceĀ – Guidelines for the Secure Deployment of IPv6 (NIST)

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