Add warning message for VirtualBox shared folders option.

Display warning to user about the VirtualBox SharedFoldersEnableSymlinksCreate
option with link to VirtualBox documentation and instructions on how the
setting can be disabled.

plugins/providers/virtualbox/synced_folder.rb

@@ -1,3 +1,4 @@
+require "fileutils"
 require "vagrant/util/platform"
 
 module VagrantPlugins
@@ -97,35 +98,51 @@ module VagrantPlugins
       # transient.
       def share_folders(machine, folders, transient)
         defs = []
+        warn_user_symlink = false
+
         folders.each do |id, data|
           hostpath = data[:hostpath]
           if !data[:hostpath_exact]
             hostpath = Vagrant::Util::Platform.cygwin_windows_path(hostpath)
           end
 
-          sharefoldersenablesymlinkscreate = true
+          enable_symlink_create = true
 
           if ENV['VAGRANT_DISABLE_VBOXSYMLINKCREATE']
-            sharefoldersenablesymlinkscreate = false
+            enable_symlink_create = false
           end
 
           unless data[:SharedFoldersEnableSymlinksCreate].nil?
-            sharefoldersenablesymlinkscreate = data[:SharedFoldersEnableSymlinksCreate]
+            enable_symlink_create = data[:SharedFoldersEnableSymlinksCreate]
           end
 
+          warn_user_symlink ||= enable_symlink_create
+
           # Only setup the shared folders that match our transient level
           if (!!data[:transient]) == transient
             defs << {
               name: os_friendly_id(id),
               hostpath: hostpath.to_s,
               transient: transient,
-              SharedFoldersEnableSymlinksCreate: sharefoldersenablesymlinkscreate
+              SharedFoldersEnableSymlinksCreate: enable_symlink_create
             }
           end
         end
 
+        if warn_user_symlink
+          display_symlink_create_warning(machine.env)
+        end
+
         driver(machine).share_folders(defs)
       end
+
+      def display_symlink_create_warning(env)
+        d_file = env.data_dir.join("vbox_symlink_create_warning")
+        if !d_file.exist?
+          FileUtils.touch(d_file.to_path)
+          env.ui.warn(I18n.t("vagrant.virtualbox.warning.shared_folder_symlink_create"))
+        end
+      end
     end
   end
 end

templates/locales/en.yml

@@ -329,7 +329,22 @@ en:
         invalid_event: |-
           %{event} is not a valid event for customization. Valid events
           are: %{valid_events}
+      warning:
+        shared_folder_symlink_create: |-
+          Vagrant is currently configured to create VirtualBox synced folders with
+          the `SharedFoldersEnableSymlinksCreate` option enabled. If the Vagrant
+          guest is not trusted, you may want to disable this option. For more
+          information on this option, please refer to the VirtualBox manual:
 
+            https://www.virtualbox.org/manual/ch04.html#sharedfolders
+
+          This option can be disabled globally with an environment variable:
+
+            VAGRANT_DISABLE_VBOXSYMLINKCREATE=1
+
+          or on a per folder basis within the Vagrantfile:
+
+            config.vm.synced_folder '/host/path', '/guest/path', SharedFoldersEnableSymlinksCreate: false
     general:
       batch_notify_error: |-
         An error occurred. The error will be shown after all tasks complete.

test/unit/plugins/providers/virtualbox/synced_folder_test.rb

@@ -19,7 +19,7 @@ describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
     machine.provider_config.finalize!
   end
 
-  describe "usable" do
+  describe "#usable?" do
     it "should be with virtualbox provider" do
       allow(machine).to receive(:provider_name).and_return(:virtualbox)
       expect(subject).to be_usable(machine)
@@ -36,7 +36,7 @@ describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
     end
   end
 
-  describe "prepare" do
+  describe "#prepare" do
     let(:driver) { double("driver") }
     let(:provider) { double("driver", driver: driver) }
     let(:folders) { {"/folder"=>
@@ -61,6 +61,8 @@ describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
 
     before do
       allow(machine).to receive(:provider).and_return(provider)
+      allow(machine).to receive(:env)
+      allow(subject).to receive(:display_symlink_create_warning)
     end
 
     it "should prepare and share the folders" do
@@ -88,7 +90,7 @@ describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
     end
   end
 
-  describe "os_friendly_id" do
+  describe "#os_friendly_id" do
     it "should not replace normal chars" do
       expect(subject.send(:os_friendly_id, 'perfectly_valid0_name')).to eq('perfectly_valid0_name')
     end
@@ -113,4 +115,89 @@ describe VagrantPlugins::ProviderVirtualBox::SyncedFolder do
       expect(subject.send(:os_friendly_id, 'foo\\bar')).to eq('foo_bar')
     end
   end
+
+  describe "#share_folders" do
+    let(:folders){ {'folder1' => {hostpath: '/vagrant', transient: true},
+      'folder2' => {hostpath: '/vagrant2', transient: false}} }
+    let(:symlink_create_disable){ nil }
+    let(:driver){ double("driver") }
+
+    before do
+      allow(subject).to receive(:display_symlink_create_warning)
+      allow(machine).to receive(:env)
+      allow(subject).to receive(:driver).and_return(driver)
+      allow(driver).to receive(:share_folders)
+      allow(ENV).to receive(:[]).with("VAGRANT_DISABLE_VBOXSYMLINKCREATE").and_return(symlink_create_disable)
+    end
+
+    it "should only add transient folder" do
+      expect(driver).to receive(:share_folders).with(any_args) do |defs|
+        expect(defs.size).to eq(1)
+      end
+      subject.send(:share_folders, machine, folders, true)
+    end
+
+    it "should display symlink create warning" do
+      expect(subject).to receive(:display_symlink_create_warning)
+      subject.send(:share_folders, machine, folders, true)
+    end
+
+    context "with create symlink globally disabled" do
+      let(:symlink_create_disable){ "1" }
+
+      it "should not enable option within definitions" do
+        expect(driver).to receive(:share_folders).with(any_args) do |defs|
+          expect(defs.first[:SharedFoldersEnableSymlinksCreate]).to be(false)
+        end
+        subject.send(:share_folders, machine, folders, true)
+      end
+
+      it "should not display symlink warning" do
+        expect(subject).not_to receive(:display_symlink_create_warning)
+        subject.send(:share_folders, machine, folders, true)
+      end
+    end
+  end
+
+  describe "#display_symlink_create_warning" do
+    let(:env){ double("env", ui: double("ui"), data_dir: double("data_dir")) }
+    let(:gate_file){ double("gate") }
+
+    before{ allow(gate_file).to receive(:to_path).and_return("PATH") }
+    after{ subject.send(:display_symlink_create_warning, env) }
+
+    context "gate file does not exist" do
+      before do
+        allow(env.data_dir).to receive(:join).and_return(gate_file)
+        allow(gate_file).to receive(:exist?).and_return(false)
+        allow(FileUtils).to receive(:touch)
+        allow(env.ui).to receive(:warn)
+      end
+
+      it "should create file" do
+        expect(FileUtils).to receive(:touch).with("PATH")
+      end
+
+      it "should output warning to user" do
+        expect(env.ui).to receive(:warn)
+      end
+    end
+
+    context "gate file does exist" do
+      before do
+        allow(env.data_dir).to receive(:join).and_return(gate_file)
+        allow(gate_file).to receive(:exist?).and_return(true)
+        allow(FileUtils).to receive(:touch)
+        allow(env.ui).to receive(:warn)
+      end
+
+      it "should not create/update file" do
+        expect(FileUtils).not_to receive(:touch).with("PATH")
+      end
+
+      it "should not output warning to user" do
+        expect(env.ui).not_to receive(:warn)
+      end
+    end
+  end
 end