Financial Cryptography

SSL for FC - not such good news

Some random notes on the adventure of securing FC with SSL. It seems that SSL still remains difficult to use. I've since found out that I was somewhat confused when I thought we could use one Apache, one IP# and share that across multiple SSL protected sites.

Quick brief of the problem: the SSL tunnel is set up and secured _before_ the HTTP headers tell the server what site is required. So there is no way to direct the SSL tunnel to be secured with a particular certificate, like the one for FC as opposed to the one for enhyper. That's a fundamental issue. That means that the cert used is fixed for IP#/port, and it contravenes Iang's 1st law 2nd hypothesis of good security protocols, to whit, "a good security protocol is divided into two halves, the first of which says to the second 'use this key.'" What arrogance!

I thought this was fixed in TLSv1 (which hereafter I'll assume as including SSLv3). Yes it is in this way: TLSv1 has a new extension in the HELO message to permit the browser to hint at what site it wants. No it is not in this way: Neither mozilla browsers nor Apache web servers implement the new extension! Worse, there is no agreement among the SSL and HTTPS sector as to how to do this.

Sheesh!

If you, like me, happen to think that more SSL will be useful in dealing with phishing (because Alice can use the cert/CA as a handle to her favourite bank) then you can vote and again for these two bugs. (You will need an account on Mozilla's bugzilla system, which I use mostly for an occasional vote).

If on the other hand you feel that phishing is ok, perhaps because the security system really wasn't meant to protect people from doing stupid things, or because money and fools should be parted, or because it hasn't happened to you yet, or for any of a myriad of other reasons, then ... don't vote (If I can figure out the same thing for Apache I'll post it.)

It seems that the desiderata to use SSL widely is shared by a brave few (other) fools over at CACert who have set up a Virtual hosts task force! Good for them, we will no longer have to worry about reaching old age in loneliness, muttering to ourselves that security wasn't meant to be this hard. CACert are experimenting on how to do this, but so far the work-around seems to be that you issue a cert that includes all the names of all the sites. Which means there is now no certificate-based independence between administrative sites - definately a kludge.

While on the topic of SSL & security, CACert's blog reports on a meeting between Comodo and Mozilla Foundation to mount a common front to phishing. "Some CAs and browser manufacturers" have been invited. More power to them, more talk is needed, spread the message. Start with:

"We have a problem with phishing."

and carry on to:

"It's our problem."

Gervase has done a white paper for the CA/browser summit called "mproving Authentication On The Internet." Good stuff.

Posted by iang at May 16, 2005 02:34 PM | TrackBack