On Aug 16, 2008, at 9:35 PM, Dean Anderson wrote:
- If Mal cracks someone else's server, that server still doesn't have the bank's certificate, and won't have the bank's dns domain, either. So the browser should think that it got the wrong certificate.
No, that wasn't my point. My point is that sometimes browsers will warn you if you submit a form to a non-SSL server. So an attacker can get rid of that warning by suborning an SSL server and directing your response toward it. You won't get a warning that your data is being submitted over an insecure link, because it's not. The link is perfectly secure - the problem is that it's the wrong link, and someone's listening on the other end who shouldn't be.
You can change browsers so that they warn you when you submit a form to a secure form on a server that's not the one that served you the form, but AFAIK browsers right now do not warn you in this situation, and it's not at all uncommon for legitimate web sites to redirect you in this way.
The user should always check that they have the right certificate and that it verifies correctly.
A security regime that depends on the user doing this has no hope of success.
In fact, the basic defense that users have is that if things look funny, they may decide not to proceed. It's an extremely thin line of defense, but it's all the average user has, because all of the checks you propose that the user make require technical knowledge that even an intelligent user who's not a practitioner in our field would not have.
So any attack that can make things not look funny is a valuable attack. And the Kaminsky attack is such an attack. You're right that it's not the only one, but eliminating it still has appreciable value.
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