Validate provided synced_folders types for access (#1644)

Reject any 9p synced folders that the user does not have read access to
the host path where using qemu sessions. This is because the VM will
launched with the user permissions instead of system permissions and
will fail to come up if trying to add a path that is not readable to be
mounted into the guest.

Additionally flag that virtiofs may not be supported with qemu sessions,
but do not reject in case support is added in the future.

Fixes: #1430

lib/vagrant-libvirt/config.rb

@@ -3,6 +3,7 @@
 require 'cgi'
 
 require 'vagrant'
+require 'vagrant/action/builtin/mixin_synced_folders'
 
 require 'vagrant-libvirt/errors'
 require 'vagrant-libvirt/util/resolvers'
@@ -10,6 +11,8 @@ require 'vagrant-libvirt/util/resolvers'
 module VagrantPlugins
   module ProviderLibvirt
     class Config < Vagrant.plugin('2', :config)
+      include Vagrant::Action::Builtin::MixinSyncedFolders
+
       # manually specify URI
       # will supersede most other options if provided
       attr_accessor :uri
@@ -1149,6 +1152,20 @@ module VagrantPlugins
           end
         end
 
+        # if run via a session, then qemu will be run with user permissions, make sure the user
+        # has permissions to access the host paths otherwise there will be an error triggered
+        if machine.provider_config.qemu_use_session
+          synced_folders(machine).fetch(:"9p", []).each do |_, options|
+            unless File.readable?(options[:hostpath])
+              errors << "9p synced_folder cannot mount host path #{options[:hostpath]} into guest #{options[:guestpath]} when using qemu session as executing user does not have permissions to read the directory on the user."
+            end
+          end
+
+          unless synced_folders(machine)[:"virtiofs"].nil?
+            machine.ui.warn("Note: qemu session may not support virtiofs for synced_folders, use 9p or enable use of qemu:///system context unless you know what you are doing")
+          end
+        end
+
         errors = validate_sysinfo(machine, errors)
 
         { 'Libvirt Provider' => errors }

spec/unit/config_spec.rb

@@ -688,7 +688,7 @@ describe VagrantPlugins::ProviderLibvirt::Config do
   def assert_valid
     subject.finalize!
     errors = subject.validate(machine).values.first
-    expect(errors).to be_empty
+    expect(errors).to be_empty, lambda { "received errors unexpectedly: #{errors}" }
   end
 
   describe '#validate' do
@@ -892,6 +892,87 @@ describe VagrantPlugins::ProviderLibvirt::Config do
         expect{ subject.finalize! }.to raise_error('Only two floppies may be attached at a time')
       end
     end
+
+    context 'with synced_folders' do
+      let(:vagrantfile) do
+        <<-EOF
+        Vagrant.configure('2') do |config|
+          config.vm.box = "vagrant-libvirt/test"
+          config.vm.define :test
+
+          config.vm.synced_folder "/path/to/share", "/srv", type: "#{type}"
+        end
+        EOF
+      end
+      let(:driver) { instance_double(::VagrantPlugins::ProviderLibvirt::Driver) }
+
+      before do
+        allow(machine.provider).to receive(:driver).and_return(driver)
+        allow(driver).to receive_message_chain('connection.client.libversion').and_return(6_002_000)
+      end
+
+      context 'when type is 9p' do
+        let(:type) { "9p" }
+
+        context 'when using qemu:///session' do
+          before do
+            subject.qemu_use_session = true
+          end
+
+          it 'should validate if user can read host path' do
+            expect(File).to receive(:readable?).with('/path/to/share').and_return(true)
+
+            assert_valid
+          end
+
+          it 'should reject if user does not have read access to host path' do
+            expect(File).to receive(:readable?).with('/path/to/share').and_return(false)
+
+            assert_invalid
+          end
+        end
+
+        context 'when using qemu:///system' do
+          before do
+            subject.qemu_use_session = false
+          end
+
+          it 'should validate without checking if user has read access to host path' do
+            expect(File).to_not receive(:readable?)
+
+            assert_valid
+          end
+        end
+      end
+
+      context 'when type is virtiofs' do
+        let(:type) { "virtiofs" }
+
+        context 'when using qemu:///session' do
+          before do
+            subject.qemu_use_session = true
+          end
+
+          it 'should warn that it may not be supported' do
+            expect(ui).to receive(:warn).with(/Note: qemu session may not support virtiofs for synced_folders.*/)
+
+            assert_valid
+          end
+        end
+
+        context 'when using qemu:///system' do
+          before do
+            subject.qemu_use_session = false
+          end
+
+          it 'should not emit a warning message' do
+            expect(ui).to_not receive(:warn)
+
+            assert_valid
+          end
+        end
+      end
+    end
   end
 
   describe '#merge' do