Subject: [Isis-wg] What cryptographic protections are there for IS-IS today?

From: Radia Perlman <[email-masked]>
Date: Fri, 02 Nov 2007 12:20:21 -0700

What cryptographic protections are currently specified for IS-IS, and what
mechanisms are generally deployed, if any?

For instance, is there:

a) (public key based) digital signature on LSP (in which case, how are the
public keys of all the routers known to all the routers in the area?)

b) per-link shared keys for protecting neighbor-neighbor router messages
(Hello, SNP, possibly even forwarded LSPs that aren't cryptographically
protect by the source). I remember from DECnet that there was
a shared per-link key, where each router was configured with a single 
secret to use
when it initiates control  messages, and a set of ones that it can use 
to verify
received control messages

c) per-area shared keys, where all routers in the same area are configured
with the same key (or set of keys so you can gracefully rollover from 
one key
to another), and all IS-IS msgs (Hellos, LSPs, SNPs) are cryptographically
protected by the router that initiated that message. (meaning, that R1 puts
something like an HMAC on its LSP, and when R2 forwards R1's LSP, R2
leaves R1's HMAC

If these things are in specs, can you point me to the specs? And even if 
they are,
how widely deployed are they?

Thanks,

Radia

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From: Tony Li <[email-masked]>
Date: Sat, 3 Nov 2007 15:34:48 -0700

Hi Radia,

> mechanisms are generally deployed, if any?

The primary protection currently can be found in RFC 3567.   You  
might also want to refer to draft-ietf-isis-hmac-sha-03, tho this  
seems to have expired (!!!?!).

I can't speak firsthand to deployment, but my general feeling is that  
it is "under-deployed".

> public keys of all the routers known to all the routers in the area?)

No, it's shared only private key today, with the obvious drawbacks.   
It's a pragmatic compromise against the obvious real world attacks.

> a shared per-link key, where each router was configured with a  
> single secret to use
> when it initiates control  messages, and a set of ones that it can  
> use to verify

Yes, but see the RFC.

> with the same key (or set of keys so you can gracefully rollover  
> from one key

Yes, but usually the implementation is to use per-area keys on LSPs  
and then per-link keys on per-link PDUs.

Tony