Adding version checking to wemo module

Addresses Github Issue 11452 by parsing out the version
information returned in /setup.xml. New code then performs
a version check, and then alerts the user to whether or not
it is likely the remote host is vulnerable given that version
check.

modules/exploits/linux/upnp/belkin_wemo_upnp_exec.rb

@@ -22,7 +22,8 @@ class MetasploitModule < Msf::Exploit::Remote
       },
       'Author'             => [
         'phikshun', # Discovery, UFuzz, and modules
-        'wvu'       # Crock-Pot testing and module
+        'wvu',      # Crock-Pot testing and module
+        'nstarke'   # Version-checking research and implementation
       ],
       'References'         => [
         ['URL', 'https://web.archive.org/web/20150901094849/http://disconnected.io/2014/04/04/universal-plug-and-fuzz/'],
@@ -82,16 +83,38 @@ class MetasploitModule < Msf::Exploit::Remote
     )
 
     if res && res.code == 200 && res.body.include?('urn:Belkin:device:')
-      vprint_good('Wemo-enabled device detected')
-      return CheckCode::Appears
+      print_good('Wemo-enabled device detected')
+    else
+      print_error('This does not appear to be a wemo-enabled device')
+      return
+    end
+
+    begin
+      version_text = res.get_xml_document.to_s
+      version_text =~ /WeMo_WW_?([\d]*[.][\d]*[.][\d]*)/ && $1 && version = (Gem::Version.new($1))
+      print_status("Found version: #{version.to_s}")
+    rescue
+      print_error('Error parsing version information from xml')
+      return
+    end
+
+    if version && version < Gem::Version.new('2.00.8643')
+      print_good('Firmware version appears to be vulnerable')
+      CheckCode::Appears
+    else
+      print_warning('Firmware version appears not to be vulnerable')
+      CheckCode::Safe
     end
 
-    CheckCode::Safe
   end
 
   def exploit
     checkcode = check
 
+    unless checkcode || datastore['ForceExploit']
+      fail_with(Failure::Unknown, 'Set ForceExploit to override')
+    end
+
     unless checkcode == CheckCode::Appears || datastore['ForceExploit']
       fail_with(Failure::NotVulnerable, 'Set ForceExploit to override')
     end