Updates for key validation:

- Check the start and stop bytes of the RFID message in addition to the
  expected length to prevent crashes.
- There is no need to re-lock the door if it was never unlocked.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

doors.py

@@ -154,8 +154,8 @@ RFID_SERIAL = serial.Serial(RFID_PATH, 2400, timeout=1)
 def read_key():
     RFID_SERIAL.reset_input_buffer() # Clear input buffer before reading
     string = RFID_SERIAL.read(12)
-    if len(string) > 0:
-        key = string[1:11].decode() #exclude start x0A and stop x0D bytes
+    if len(string) == 12 and string[0] == 0xA and string[-1] == 0xD:
+        key = string[1:11].decode() #exclude start 0xA and stop 0xD bytes
         if key.isalnum():
             return key;
     return None
@@ -166,7 +166,7 @@ def read_rfid():
         if key and verify_key(key):
             unlock_door()
             time.sleep(5) # block for 5 seconds before resetting door
-        lock_door()
+            lock_door()
         flush_keys()
     except Exception as e:
         print(e)