Forticlient: Root Compromise -- Existing Account

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2015.1962
 FortiClient SSLVPN Linux client local privilege escalation vulnerability
                               28 July 2015

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        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           Forticlient
Publisher:         FortiGuard
Operating System:  Linux variants
Impact/Access:     Root Compromise -- Existing Account
Resolution:        Patch/Upgrade

Original Bulletin: 
   http://www.fortiguard.com/advisory/FG-IR-15-017/

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FortiClient SSLVPN Linux client local privilege escalation vulnerability

Info

Risk 	Medium 

Date 	Jul 24 2015

Impact 	Privilege Escalation

Fixed 	In Firmware 2317

Installing Forticlient SSLVPN Linux client build 2312 and lower in a home 
directory that is world readable-executable yields a privilege escalation 
vulnerability: Any local user can then exploit the helper/subroc setuid binary
to run arbitrary code with root privileges.

Impact

When subproc is called, it parses and executes "./iclean.linux.sh". Thus a 
malicious local user may create a symbolic link to subproc in the same 
directory as an "arbitrary" iclean.linux.sh. The latter will then be parsed 
and executed by subproc (i.e. with uid 0).

Affected Products

Standalone Forticlient SSLVPN Linux client build 2312 and lower.

Solutions

Upgrade to FortiClient Linux SSLVPN version 2317 or above.

Actual Exploitability varies with host systems: Ubuntu and Debian are known to
set world readable-executable epermissions on home directories by default, 
while Fedora (and most other Linux distribution) do not.

In the following example, user notvulnerable is not affected, while user 
iamvuln could be affected:

ls -l /home
total 28
drwx------. 3 notvulnerable notvulnerable 4096 Jul 21 14:26 notvulnerable
drwx---r-x. 6 iamvuln iamvuln 4096 Jul 21 14:26 iamvuln

A workaround is to apply chmod 700 to the user's home directory who installed
the Linux FortiClient SSLVPN.

Acknowledgement

Thanks to Brian Vincent.

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