Re: New Web Vulnerability - Cross-Site Tracing (fwd)

For anyone interested, you won't likely see my response on bugtraq since my message was rejected for using profanity ("half-assed") and I do not wish to modify it and resubmit.

• Forwarded message ---------- Date: Wed, 22 Jan 2003 12:11:25 -0800 (PST) From: Marc Slemko <marcs@znep.com> To: bugtraq@securityfocus.com Subject: Re: New Web Vulnerability - Cross-Site Tracing

On Wed, 22 Jan 2003, Pete Soderling wrote:

> I thought this news might interest the group ...
>
> ExtremeTech (http://extremetech.com) just released an article on a new type of vulnerability recently reported to CERT, Cross-Site Tracing (XST).
>
> "After months of extensive research, San Jose California-based WhiteHat Security has unmasked a flaw in one of the Web's cornerstone protocols which places all e-commerce sites, as well as scores of Internet users, in jeopardy.
>
> This threat was discovered by application security research firm WhiteHat, and is detailed in David's story below. White Hat Security was started by a former CTO from Ungermann-Bass, and an Information Security officer at Yahoo!."
>
> Read the entire post at: http://www.extremetech.com/article2/0,3973,841047,00.asp

Wow, what a misinformed article. The whitepaper available on WhiteHat's site is better (http://www.whitehatsec.com/news.html) but it still requires very careful reading to appreciate what parts of it are talking about things that are due to other known holes and which are actually news.

Essentially what it boils down to is that Microsoft's "httponly" cookie hack is half-assed, and doesn't really work very well in reality, and that because MS has a horribly record of cross domain security holes that they refuse to patch in a timely manner then somehow this hole is a new all pervasive attack.

Trying to pass all this off as some flaw in TRACE is... obscene. Combining existing holes that already have a huge exposure, then adding in a few little new pieces appears to be a strategy designed to hype the importance of the issue.

The only new thing here is that this provides a way to get HTTP basic authentication credentials and, while this is indeed a notable discovery, it is unfortuante that is presented in the overhyped way it is. It has been possible to obtain basic auth credentials in the past both from browsers that improperly allowed newline characters to be embedded in fields in the request (allowing the authorization to end up in the request body) and browsers that could be tricked into thinking they are sending a request to site x while really sending to site y, but AFAIK those holes are all fixed in any recent versions of common browsers.

The reality is that there are many cases where the server returns information to the user that is confidential. TRACE is one of those. Embedding session IDs in returned links is one (very commonly done on app servers that support cookie based session tracking with a fallback to url based). Returning a user's bank account number when they view their account is another. I don't see trying to disable every way that the server can send sensitive data to the browser as being a very effective path to try to take to solve such issues.

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The bottom line: Why do you even need to steal the user's authentication token if you have full access to get their browser to submit requests and the ability to grab the contents of the results? And having access to those two things is exactly what this whitepaper is assuming. Yes, there is a small incremental exposure to being able to take the authentication token away with you and use it yourself but that is marginal compared to the exposure from the holes being assumed to be there before the new TRACE issue can be exploited. Received on Wed Jan 22 18:30:24 2003