Full Disclosure mailing list archives
Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website.
From: Nick FitzGerald <nick () virus-l demon co uk>
Date: Fri, 16 Jul 2004 12:10:33 +1200
Seth Alan Woolley to me:
The correct solution to all such problems is simply to reject the content as malformed. And guess what will happen when you do that? Several really crappy web design products will disappear because the folk using them will drop them because no-one can see their pages _and_ the rest will suddenly become very inetrested in producing properly compliant content, as they should have been from the outset. Playing "guess what the moron really meant" is a recipe for being screwed, so let's get over the previous "need" to "see it at all cost" and get some sense back into what folk are doing...It wouldn't affect too many products to fix this. I would be hard-pressed to find _any+. I would think the fact that IE didn't interpret the malformed script tag would lead all developers to fix any and all occurrances of the problem in real production code. Because of this only XSS attempts are really going to be blocked by a fix. It was behavior only seen in Mozilla. None of the other browsers do it. And the last comment of mine to the bug explained why it's possible to fix the tags without breaking anything unless it is highly suspect. When you're repairing a script tag, close the tag at the first whitespace character, not before the next tag so that anybody can stick whatever attributes into the entity they want. Fixed. Leave the other tags to interpret liberally if you want. I mostly care about the script tag and the object and iframe tags, especially -- anything with src or href attributes. The general fix would be to close the tag before the text 'src=' or 'href=' and any other attribute like this.
And you don't see the problem with that? Hint -- "and any other attribute like this". Sounds like blacklisting or "default allow" to me. Now, what does the theory _AND_ history tell us about such (hint) stupiidities? Do you know what they all are? What about the ones that will be added in the future -- no, they won't be a problem, surely the Mozilla (and Opera and IE and ...) developers will simply add special handling for them too when they arise and of course, everyone who uses Mozilla (or whatever browser) updates to the latest, greatest version immediately it is released so there will never be any exposure going forward...
It's a simple fix and not fixed it makes XSS a lot easier on many common web tools. (Early versions of the popular blog tool MovableType, for example, had this bug.)
And that attitude is a large part of why we're in the security mess we're in. "It'll be right" might be good enough for government work, but it certainly sucks when it comes to security awareness issues... Broken input is broken input and apart from in incredibly simple systems with highly constrained and limited possible valid input options (and even then by far not always), thinking you can accept such input and "tweak" it to "fix" it is one of the keys that opens the gate to the fool's paradise. There are plenty of such key-holders at MS but shouldn't Mozilla developers be above that? I know it's a hard marketing battle to win when your competitor is the 800lb gorilla _AND_ they do all the stupid dirty tricks as well, but if you're going to compete on quality and/or standards compliance and/or security issues, at least try to do a reasonable job of _those_ things rather than lowering yourself to Microsoft's level. Regards, Nick FitzGerald _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
Current thread:
- Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Seth Alan Woolley (Jul 14)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Barry Fitzgerald (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Nick FitzGerald (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Barry Fitzgerald (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Seth Alan Woolley (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Nick FitzGerald (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Seth Alan Woolley (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Nick FitzGerald (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Barry Fitzgerald (Jul 15)
- Re: Exploits in websites due to buggy input validation where mozilla is at fault as well as the website. Seth Alan Woolley (Jul 15)