Sunday, December 6, 2009

A Threat Model for SSL

I traced a link to my post How fast are Debian-flawed certificates being re-issued? to SSL Shopper, a new site for me, and I looked back through their news items and found a link to an SSL Threat model proposed by Ivan Ristić, the principle author of ModSecurity and a leader in Apache security.

Referring to the origins of his threat model, Ivan states that

SSL is easy to use but also very easy to use incorrectly. The ecosystem, which is built of the specifications, the implementations, the CAs and the PKI, is full of traps, each of which is very easy to fall into. Once I started to spend significant time thinking about SSL I set out to build a model of the ecosystem, for my own education and to ensure that I understand it all. That's how I arrived to the SSL Threat Model.

His threat model is represented as a FreeMind map, available as a graphic as shown below. The threat model considers clients, servers, PKI, protocols, users and attacks, and perhaps the model needs to be updated in light of the new The TLS Renegotiation Attack.

image

Ivan admits that the model needs some additional clarification, but it is probably more useful as a published draft rather than waiting for him to find the time to perfect the model (the same reasoning lead me to releasing my outline of a password book).

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