virt-aa-helper: generate rules for passthrough input devices

Input devices can passthrough an event device. This currently works only via
hotplug where the AppArmor label is created via the domain label callbacks.

This adds the virt-aa-helper support for passthrough input devices to generate
rules for the needed paths from the initial guest definition as well.

Example in domain xml:
  <input type='passthrough' bus='virtio'>
          <source evdev='/dev/input/event0' />
  </input>
Works to start now and creates:
  "/dev/input/event0" rw,

Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1757085Acked-by: NJamie Strandboge <jamie@canonical.com>
Signed-off-by: NChristian Ehrhardt <christian.ehrhardt@canonical.com>

src/security/virt-aa-helper.c

@@ -1157,6 +1157,14 @@ get_files(vahControl * ctl)
         }
     }
 
+    for (i = 0; i < ctl->def->ninputs; i++) {
+        if (ctl->def->inputs[i] &&
+                ctl->def->inputs[i]->type == VIR_DOMAIN_INPUT_TYPE_PASSTHROUGH) {
+            if (vah_add_file(&buf, ctl->def->inputs[i]->source.evdev, "rw") != 0)
+                goto cleanup;
+        }
+    }
+
     for (i = 0; i < ctl->def->nnets; i++) {
         if (ctl->def->nets[i] &&
                 ctl->def->nets[i]->type == VIR_DOMAIN_NET_TYPE_VHOSTUSER &&

tests/virt-aa-helper-test

@@ -359,6 +359,9 @@ testme "0" "hugepages" "-r -u $valid_uuid -F /run/hugepages/kvm/\*\*" "$test_xml
 sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,<graphics.*>,<graphics type='vnc' socket='/var/lib/libvirt/qemu/myself.vnc'><listen type='address' address='0.0.0.0'/></graphics>,g" "$template_xml" > "$test_xml"
 testme "0" "vnc socket" "-r -u $valid_uuid" "$test_xml"
 
+sed -e "s,###UUID###,$uuid,g" -e "s,###DISK###,$disk1,g" -e "s,</devices>,<input type='passthrough' bus='virtio'><source evdev='$disk2' /></input></devices>,g" "$template_xml" > "$test_xml"
+testme "0" "input dev passthrough" "-r -u $valid_uuid" "$test_xml"
+
 testme "0" "help" "-h"
 
 echo "" >$output