Mac OS X 10.10.2 kernel extension heap overflow resulting in LPE

[Luca Todesco <info () qwertyoruiop com>]

Hello,

I have recently found an exploitable heap overflow in a core OS X driver.
Particularly, the injectString function is vulnerable to an heap overflow and can be triggered without privileges of 
any kind.


The vulnerable function can be seen at 
http://opensource.apple.com/source/IOHIDFamily/IOHIDFamily-503.200.2/IOHIDSystem/IOHIDSecurePromptClient.cpp


I wrote a weaponized poc at http://github.com/kpwn/vpwn.


The KASLR leak included is not reliable across macs. It works only on Macs with AMD (no FirePro) GPUs. (Tested on a 
last gen 5K Retina iMac). 
It was the only one I'd sacrifice for a public PoC because of that constraint.
It's disabled by default too, but it's trivial to enable it by editing lsym_priv.h.


It does not completely clean up it's own mess, so running ioreg after running the PoC will likely crash your box. 


The particular IOKit service has been involved in a CVE in October. It had functions that could literally not be used 
without crashing the kernel. 
There still are other unsafe functions in that very same file. Apple has disabled the service in particular on the 
latest 10.10.3 beta possible due to those other bugs. I do not believe they are aware of this issue in particular. But 
this is pure speculation, and it doesn't matter in the end, since the vulnerability cannot be triggered anymore.


Let me know what you think and sorry for the wall of text,
Luca Todesco.
-qwertyoruiop

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