In Vagrant, you have the option to mount a shared folder with two options

This would mount /vagrant/www where permissions can be changed outside of Vagrant, but not inside the VM.

config.vm.synced_folder "./www", "/vagrant/www",
  owner: "vagrant",
  group: "www-data",
  :mount_options => ["dmode=775", "fmode=664"]

This would let user change file and directory permissions within the VM.

config.vm.synced_folder "./www", "/vagrant/www",
  :nfs => true