Microsoft has finally begun patching a severe security flaw in its implementation of digital-certificate basic-constraints checking which we've been ranting about for nearly a month. The stuff-up makes it possible for SSL and e-mail signature certs to be forged.
Currently, Win-NT and XP users have fixes available for their kit. This leaves Win-98, 98-SE, ME, and 2K users waiting for patches which will be 'issued shortly,' the company says. There will also be patches for numerous versions of Internet Explorer, MS-Office, and Outlook Express for the Mac. On Windows it's necessary only to fix CryptoAPI for each OS version, but on Macs the situation is reversed; each Microsoft application needs to be fixed separately -- so if you're using more than one, you'll need more than one patch.
Interestingly, MS rates this Trustworthy Computing stuff-up 'Critical', in contradiction to their earlier whitewash of the issue.
Even now, with the 'C' word plastered all over the MS bulletin, the company can't resist plugging in every bit of soft-pedal boilerplate from its original 'what, us worry?' PR offering. There is no mention of the fact that a valid certificate and key have already been circulated with SSLsniff, an exploit tool developed by Mike Benham, who first reported the issue.
There is also no mention of the way SSLsniff can be used to intercept a third party's SSL session where the victim and attacker are on the same LAN. Indeed, there's no mention of Benham himself, but that's probably due to Redmond's irritation with him for spilling the beans before they were ready to have them spilt. Of course there was always a simple workaround: Windows users could have used Mozilla for both e-mail and browsing, and simply not been troubled. For its part, MS seems not to have appreciated the the elegance of this solution.
The MS bulletin and links to the patches can be found here. ®