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Showing posts from October, 2010

.NET Padding Oracle Attack,, and the Microsoft Recommended Workarounds

For some stupid reason, Whenever GoDaddy sees h t t p s : / / it turns it into a link and removes the scheme. This even happens if you edit the html manually. Because of this sillyness, I've used https:\\ below.

Since I first heard of the Padding Oracle issue, I've wanted to use it to exploit a site. I had that chance this week. Alex Lauerman and I muddled our way through this confusing (at least to me) attack scenario.

The attack is dependent on the server responding differently to an error in the decryption process vs an error in the application due to invalid data. The different response codes tells us whether or not the padding is valid or invalid. If you want to read more on the background of the issue, check out the great post over at

Now that we have a bit of the background covered, back to the site. Upon quick inspection we saw that 404 and 500 errors are redirected to the same error page. Bantha Herders! How did we know this? The 404 result was easy to t…