itle: InstantHMI - EoP: User to ADMIN
CWE Class: CWE-276: Incorrect Default Permissions
Date: 01/06/2016
Vendor: Software Horizons
Product: InstantHMI
Version: 6.1 
Download link: http://www.instanthmi.com/ihmisoftware.htm
Tested on: Windows 7 x86, fully patched
Release mode: no bugbounty program, public release
 
Installer Name: IHMI61-PCInstall-Unicode.exe
MD5: ee3ca3181c51387d89de19e89aea0b31
SHA1: c3f1929093a3bc28f4f8fdd9cb38b1455d7f0d6f
 
- 1. Introduction: -
During a standard installation (default option) the installer 
automatically creates a folder named "IHMI-6" in the root drive. 
No other location can be specified during standard installation.
 
As this folder receives default permissions AUTHENTICATED USERS 
are given the WRITE permission. 
 
Because of this they can replace binaries or plant malicious 
DLLs to obtain elevated, administrative level, privileges.
 
- 2. Technical Details/PoC: -
A. Obtain and execute the installer. 
 
B. Observe there is no prompt for the installation location.
 
C. Review permissions under the Explorer Security tab or run icacls.exe
 
Example:
 
IHMI-6 BUILTIN\Administrators:(I)(F)
       BUILTIN\Administrators:(I)(OI)(CI)(IO)(F)
       NT AUTHORITY\SYSTEM:(I)(F)
       NT AUTHORITY\SYSTEM:(I)(OI)(CI)(IO)(F)
       BUILTIN\Users:(I)(OI)(CI)(RX)
       NT AUTHORITY\Authenticated Users:(I)(M)
       NT AUTHORITY\Authenticated Users:(I)(OI)(CI)(IO)(M)
 
Successfully processed 1 files; Failed processing 0 files
 
D. Change the main executable: InstantHMI.exe with a malicious copy. 
 
E. Once executed by an administrator our code will run 
under administrator level privileges.
 
- 3. Mitigation: -
A. Install under "c:\program files" or "C:\Program Files (x86)"
 
B. set appropriate permissions on the application folder.
 
- 4. Author: -
sh4d0wman