• 1
howdy! thanks for the quality writeup; i added you as a friend to track anything more of this nature (most friend requests i get these days are spam).

Response from the exploit author

These are not my comments, they are the comments of Brad Spengler, the author of the really cool exploit I mentioned. He commented off of the blog, but gave permission to post his comments here.

First off, of all people/companies, Red Hat surely knows that stolen SSH credentials or guessed passwords isn't an esoteric entry vector.

NX+ASLR by itself is enough to deter someone from trying to inject a kernel exploit like this one within a network-facing process. The thing that does the most to keep a process compromised by memory corruption bugs from doing things it shouldn't is the SELinux feature a 3rd party developed, execmod -- basically PaX's MPROTECT feature (remember when Ingo argued against it?)

Second, it's a little disingenuous to try to prop up the security of SELinux by bringing up the Wine issue. How many webservers do you know of that run X and Wine? The real entry vector here is webservers (say with some vulnerable php / SQL injection bug) or other multi-user machines, not desktops where people would be running Wine (as a multi-user desktop with Wine would almost certainly involve some sort of physical access as well).

So in the cases where the exploit would have been actually used, by default, SELinux removed security that would have existed had SELinux been disabled.

And from reading Dan Walsh's blog, it looks as though the problem is quite a bit larger and won't be remedied fully anytime soon because
1) There still hasn't been a CVE for it yet, which demonstrates from Red Hat's end that this isn't important to them
2) Dan Walsh gave the command for all exploit writers to use to be able to mmap at 0 even if unconfined_t isn't allowed to do it in the future
3) He's also said that RHEL5 by default will continue to allow unconfined_t to mmap at 0 for compatability purposes.

Though I believe based on the current patch submitted to LKML, 2&3 will only apply when mmap_min_addr is disabled (though then the compatability argument doesn't make much sense, as users may be expecting to be able to mmap there (since they've been able to for who knows how long -- I haven't seen anyone from Fedora or Red Hat quantify this yet) and with the new kernel they'll be unable to without disabling mmap_min_addr).


The pulseaudio/personality trick

FYI, the pulseaudio/personality trick didn't come from Brad but from Tavis Ormandy and Julien Tinnes

Re: The pulseaudio/personality trick

I have never read something like this.
Great stuff!

  • 1

Log in