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Re: soBGP deployment
On Sat, 21 May 2005, Steven M. Bellovin wrote:
Yet, what is the (SBGP) alternative?With SBGP, each node signs the BGP statements it's about to send out. The accuracy of the security statement is thus linked to the transmission process. With SO-BGP, the security against in-path attacks (or cut-and-paste attacks; see below) relies on a secure version of the routing registry. If an AS forgets to update its routing registry to reflect new BGP adjacencies, paths containing them will be dropped by SO-BGP listeners. If old adjacencies aren't deleted, routes that shouldn't be accepted will be. In other words, there's a lot less coupling between the transmission process and its security properties. Look at it this way: do you think that (a) most sites will publish their policies in the registry, and (b) they'll remember to update them? As Randy has noted, we have a decade of experience suggesting that neither is true.
I don't think we have much success distributing this kind of certificates in similar scenario either. At least we _do_ have some (limited) experience and even success in recording the prefixes in routing databases, and adding a signature there would be easy.
There's nothing to say the functional equivalent of certificate could also not be passed in an option or some other means as well when needed. My assumption would be that being able to use public databases would be a protocol optimization.
Compare this to the situation when BGP filtering is done by automatically generating the prefix lists. How would enhancing that to include a signature (and/or certificate) make matters worse or inefficient? Is there any reason to believe using a different approach would fare any better?
Note that the original soBGP didn't require any updates when the peering relationships changed; based on a quick look, a later extension has probably changed this.
Note that there's no technical reason AFAICS not to tie the signed origin statements to the origin's AS number, i.e., if someone would want to hijack a prefix, it would need to spoof the AS number as well. Not sure if that helps a lot, of course.Let me add a word about cut-and-paste attacks. A signed origin statement asserts that some AS owns some prefix. That statement will be readily available. A nefarious site could cut that statement from some actual BGP session and prepend it to its own path announcement. That would add a hop, but many ASs will still prefer it and route towards the apparent owner through the nefarious site. The nefarious site wouldn't forward such packets, of course; it would treat the packets as its own.
But this is a good point -- I think a fundamental question that needs to be asked is whether a sufficient security could be gained by just the originator and the verifier doing the cryptographic operations, and not requring everyone in the middle also do them (adding signatures etc.). Personally I'd certainly hope so -- because the practical deployment issues with the on-the-path signing model seem prohibitive (too much 3rd party deployment required before the solution would be useful).
Pekka Savola "You each name yourselves king, yet the
Netcore Oy kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings