Allele Security Alert
Untrusted Search Path
London Trust Media
Private Internet Access (PIA) VPN Client
Private Internet Access (PIA) VPN Client for macOS v82
Private Internet Access (PIA) VPN Client for macOS v1.2.1+
Proof of concept
A vulnerability in the London Trust Media Private Internet Access (PIA) VPN Client v82 for macOS could allow an authenticated, local attacker to run arbitrary code with elevated privileges.
The PIA macOS openvpn_launcher binary is setuid root. This program is called during the connection process and executes several operating system utilities to configure the system. The networksetup utility is called using relative paths. A local unprivileged user can execute arbitrary commands as root by creating a networksetup trojan which will be executed during the connection process. This is possible because the PATH environment is not reset prior to executing the OS utility.
All steps are executed as a low privileged user.
Step 1 – Create a script named networksetup with the following two lines. This PoC will send the output of the id command to wall. This will show that its running with root privileges(uid=0).
#!/bin/sh echo "$0: $(/usr/bin/id)"|/usr/bin/wall
Step 2 – Make the networksetup script executable.
chmod 755 networksetup
Step 3 – Execute run.sh to open the PIA GUI client while prepending the current working directory($PWD) to the PATH environment variable. This ensures that the trojan networksetup script is executed first because relative paths are used.
env "PATH=$PWD:$PATH" /Applications/Private\ Internet\ Access.app/Contents/MacOS/run.sh
Step 4 – Login and connect to the VPN
During the connection process networksetup will be executed as root and see a wall message will be broadcasted showing the output of id command with uid=0.
PIA macOS Privilege Escalation: Untrusted Search Path
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Last modified: June 25, 2019