Update check_email to handle hosts without an A record (either AAAA only or MX only)

ceo/members.py

@@ -5,14 +5,14 @@ This module contains functions for registering new members, registering
 members for terms, searching for members, and other member-related
 functions.
 
-Transactions are used in each method that modifies the database. 
+Transactions are used in each method that modifies the database.
 Future changes to the members database that need to be atomic
 must also be moved into this module.
 """
 import os, re, subprocess, ldap, socket
 from ceo import conf, ldapi, terms, remote, ceo_pb2
 from ceo.excep import InvalidArgument
-
+import dns.resolver
 
 ### Configuration ###
 
@@ -179,11 +179,16 @@ def check_email(email):
         if c in ('"', "'", ',', '|', '$', '/', '#', ':'):
             return 'Invalid character in address: %s' % c
 
+    # Start by searching for host record
     host = match.group(1)
     try:
-        ip = socket.gethostbyname(host)
+        ip = socket.getaddrinfo(host, None)
     except:
-        return 'Invalid host: %s' % host
+        # Check for MX record
+        try:
+            dns.resolver.query(host, 'MX')
+        except:
+            return 'Invalid host: %s' % host
 
 
 def current_email(username):
@@ -433,7 +438,7 @@ def set_shell(userid, shell):
 def create_club(username, name):
     """
     Creates a UNIX user account with options tailored to CSC-hosted clubs.
-    
+
     Parameters:
         username - the desired UNIX username
         name     - the club name
@@ -449,7 +454,7 @@ def create_club(username, name):
     # check username format
     if not username or not re.match(cfg['username_regex'], username):
         raise InvalidArgument("username", username, "expected format %s" % repr(cfg['username_regex']))
-    
+
     try:
         request = ceo_pb2.AddUser()
         request.type = ceo_pb2.AddUser.CLUB