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Attacking XML Processing

Nicolas Gregoire has been professionally hacking things for more than twelve years. After defending a start-up against some motivated russian hackers (true story!), he spent 4 years doing pentesting and then became an internal security auditor for one of largest French PKI’s. At the beginning of 2011, he left this job to create Agarri, a small company where he finds bugs for customers or for fun. His main research area is XML technologies at large, with a unreasonable attraction for XSLT.

Questions and Answers

1. Would you suggest that we all use the “No-Script” addon? I.e. the popular firefox/ chrome addon that blocks a lot of scripts or is that just for XSS?

I didn’t do any specific testing but I don’t think that noscript will instruct your browser not to execute XSLT Code. Noscript is really for JavaScript and we are more [interested] in the XML components triggering XSLT; I mean it’s not configurable by noscript.

2. Is there a “checklist” to prevent XML common hacks

Not really at the moment. There are several efforts, for example the SSRF bible and I have a wiki related to XSLT exploits and vulnerabilities but it’s not very up to date so I should spend more time on that. There is no absolute reference but if you are interested you can just attend major conferences like Black Hat or Hackinthebox. Look to the XML content and you will see some [good] documentation – but [there is] no ready “checklist”

3. Which is the best pentesting tool to use to text for XML vulnerabilities?

It’s an answer similar to the previous question. There are a lot of people doing things on their own but there is no unity between the two. I mainly publish my exploit code in metasploit format. There is no all-in-one tool to test for XML vulnerabilities.

4. Are XML hacks going to become more prevalent on Smartphone – is there a smart phone OS that does a better job to prevent XML hacks?

I didn’t have a look at the Smartphon side from an XML point of view. The only thing I tried was exploitation of the Apple browser on an iPad tablet with web kit vulnerability and it is was working fine. I don’t see any conclusive point for Smartphone versus server side enterprise servers for example.

You mentioned before that there is a community and that it is getting more active. Is there an XML website or a community website that you can point the audience to?

There is nothing specific – we know each other there is nothing public. It [is] a good idea but always a lot of effort to set up a website or wiki or anything like that.

What is the future of XML and XLST – do you see the code becoming harder to hack – will it become more “hack-proof”

If there are several researchers or attackers looking for vulnerabilities then vendors will have to react and increase the security of their components but it only works for vendors that are already convinced that they need to have a secure application.

I mean, if you are only using a small library doing XML processing you [might not] pay much security attention. It’s ok for big vendors which can react. I think there will [continue] to be a lot of problems in the future.

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