Full Disclosure mailing list archives
Re: DLL hijacking with Autorun on a USB drive
From: Dan Kaminsky <dan () doxpara com>
Date: Fri, 27 Aug 2010 10:08:08 -0400
h0h0h0. There be history, Larry. Short version: Go see how many DLLs exist outside of c:\windows\system32. Look, ye mighty, and despair when you realize all those apps would be broken by CWD DLL blocking. Longer version: Unix has always had the tradition of a system administrator. When it went consumer, it went straight to package management -- something it could do, because a) there just aren't that many apps and b) they're mostly open source, so distros can legally fix things up. Windows comes from a different direction: Many, many consumer facing apps, very few of them open source, users installing for themselves, no package manager. Among other things, this introduces the concept of: Which DLLs should you load? Suppose you have ten applications, each using foo.dll. Should they all use foo.dll from c:\windows\system32? Maybe, maybe not. There are many possible versions that might be in there, and they might or might not work. You can push your version of foo.dll into c:\windows\system32. Great, you'll work fine, but there's nine other apps you might break. You can use a local foo.dll. Now you can have your lib and they can have theirs. Welcome to DLL hell. There's been a lot of work in fixing this situation, but not from the security perspective. I know we're masters of righteous indignation, but I have to emphasize -- while there's probably an actual vuln somewhere using this methodology, nothing's been found yet. Changing something with only a tenuous link to security, with such a massive impact on whether applications run or not? Yeah, not exactly surprised it's still there. On Fri, Aug 27, 2010 at 7:20 AM, Larry Seltzer <larry () larryseltzer com>wrote:
Clearly desktops need to be able to run arbitrary code. That’s what they’re there for. Why wouldn’t eliminating the CWD from the DLL search order fix the problem? I asked Microsoft about this ( http://blogs.pcmag.com/securitywatch/2010/08/list_of_dll_vulnerability_wind.php) and they said the obvious answer, that it would break too many customer installations. And I guess it would break a bunch of them, but there really isn’t a good reason for anyone to load a DLL from the CWD, is there? I think they dropped the ball on this at Vista time. They made so many other changes for security reasons then that forced users and developers to change practice that this one wouldn’t have been such a big stink. And they’ve known about the basic problem for 10 years (and should have known earlier, since it was a UNIX attack beforehand).
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Current thread:
- Re: DLL hijacking with Autorun on a USB drive, (continued)
- Re: DLL hijacking with Autorun on a USB drive Dan Kaminsky (Aug 26)
- Re: DLL hijacking with Autorun on a USB drive Valdis . Kletnieks (Aug 26)
- Re: DLL hijacking with Autorun on a USB drive Dan Kaminsky (Aug 26)
- Re: DLL hijacking with Autorun on a USB drive Larry Seltzer (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Valdis . Kletnieks (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Dan Kaminsky (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Valdis . Kletnieks (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Christian Sciberras (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Valdis . Kletnieks (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Michal (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Dan Kaminsky (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Larry Seltzer (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Dan Kaminsky (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Christian Sciberras (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Dan Kaminsky (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Larry Seltzer (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Arthur Orr (Aug 28)
- Re: DLL hijacking with Autorun on a USB drive Larry Seltzer (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive Florian Weimer (Aug 27)
- Re: DLL hijacking with Autorun on a USB drive coderman (Aug 30)
- Re: DLL hijacking with Autorun on a USB drive paul . szabo (Aug 26)