On Thu, 22 Jun 2006 13:18:35 -0400, Ron Bonica <rbonica@juniper.net> wrote:
Steve,
In Section 1 of your draft, you say:
"The proper solution involves some sort of key management protocol. Apart from the complexity of such things, RFC 2385 was not written with key changes in mind. In particular, there is no KeyID field in the option, which means that even a key management protocol would run into the same problem.
Fortunately, a heuristic permits key change despite this protocol deficiency."
Why not correct the protocol deficiency by introducing a new option that includes a KeyID? Wouldn't that approach provide a more comprehensive solution to the problem?
That's a much better long-term strategy, though the exact mechanism still has to be defined. But it's literally years before that will be usable, especially because both ends of a connection need to be upgraded before it delivers any benefits. That is especially problematic for the interISP case. We both agree that key change is (a) necessary, and (b) very difficult with 2385. The longer-term issue is where "there" his, and that's what your draft addresses; my draft is about how to get from "here" to "there". --Steven M. Bellovin, http://www.cs.columbia.edu/~smb
On 22-jun-2006, at 23:17, Steven M. Bellovin wrote:
Why not correct the protocol deficiency by introducing a new option that includes a KeyID? Wouldn't that approach provide a more comprehensive solution to the problem?
That's a much better long-term strategy, though the exact mechanism still has to be defined. But it's literally years before that will be usable, especially because both ends of a connection need to be upgraded before it delivers any benefits.
If you want benefits when only one end is upgraded, your mechanism for concurrent keys could be used like this: - the upgraded side installs the new key - the upgraded side keeps using the old key - the non-upgraded side installs the new key - the upgraded side detects that the other side uses the new key and switches over itself - the old key is removed from the upgraded side This way, it all goes down when the non-upgraded side installs the key: they can immediately see the problem if there is some kind of issue with the key (for instance someone entered it incorrectly). It still makes sense to add stuff that allows both ends to manage the key rollover when they're both upgraded, since in that case something like the above won't work. I think something like this would work well: - announce key rollover capability at session connect - when a new key is configured, send a hash of it to the other side - other side doesn't have the key yet so says "reject" - other side is also configured with the new key, sends a hash - first side sees hashes match, starts sending with the new key and says "accept" Bonus points: when no key is configured, one of the routers generates one at session start and sends it over in the clear. This protects equally well against session reset attacks as a preconfigured key, but obviously it can be sniffed by someone with access to the infrastructure.
We both agree that key change is (a) necessary, and (b) very difficult with 2385.
How often do you think keys should change? I've never had anyone ask to change keys for about 50 session-years.
How often do you think keys should change?
Arguably, any time someone who had access to the key is no longer supposed to have such access.
I've never had anyone ask to change keys for about 50 session-years.
I guess the question the question is whether that's because they really never needed to, really didn't think about, or really didn't want to suffer the hassle and so just accepted the risk. DS
participants (3)
-
David Schwartz -
Iljitsch van Beijnum -
Steven M. Bellovin