From 8291c814c54d87c7958304e471a5c5c013417e45 Mon Sep 17 00:00:00 2001
From: Mark Sapiro <mark@msapiro.net>
Date: Tue, 5 Jun 2018 12:14:08 -0700
Subject: Extend BLOCK_SPAMHAUS_LISTED_IP_SUBSCRIBE for IPv6. Fix string
 formatting for Python 2.6.

---
 Mailman/Utils.py | 28 +++++++++++++++++++++-------
 NEWS             |  4 +++-
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/Mailman/Utils.py b/Mailman/Utils.py
index cdc82366..6038667b 100644
--- a/Mailman/Utils.py
+++ b/Mailman/Utils.py
@@ -79,6 +79,12 @@ try:
 except ImportError:
     dns_resolver = False
 
+try:
+    import ipaddress
+    have_ipaddress = True
+except ImportError:
+    have_ipaddress = False
+
 EMPTYSTRING = ''
 UEMPTYSTRING = u''
 CR = '\r'
@@ -1498,13 +1504,21 @@ def xml_to_unicode(s, cset):
 def banned_ip(ip):
     if not dns_resolver:
         return False
-    parts = ip.split('.')
-    if len(parts) != 4:
-        return False
-    lookup = '{}.{}.{}.{}.zen.spamhaus.org'.format(parts[3],
-                                                   parts[2],
-                                                   parts[1],
-                                                   parts[0])
+    if have_ipaddress:
+        try:
+            uip = unicode(ip, encoding='us-ascii', errors='replace')
+            ptr = ipaddress.ip_address(uip).reverse_pointer
+        except ValueError:
+            return False
+	lookup = '{0}.zen.spamhaus.org'.format('.'.join(ptr.split('.')[:-2]))
+    else:
+        parts = ip.split('.')
+        if len(parts) != 4:
+            return False
+        lookup = '{0}.{1}.{2}.{3}.zen.spamhaus.org'.format(parts[3],
+                                                           parts[2],
+                                                           parts[1],
+                                                           parts[0])
     resolver = dns.resolver.Resolver()
     try:
         ans = resolver.query(lookup, dns.rdatatype.A)
diff --git a/NEWS b/NEWS
index ff4debae..e037982c 100644
--- a/NEWS
+++ b/NEWS
@@ -26,7 +26,9 @@ Here is a history of user visible changes to Mailman.
 
     - A new BLOCK_SPAMHAUS_LISTED_IP_SUBSCRIBE setting has been added to
       enable blocking web subscribes from IPv4 addresses listed in Spamhaus
-      SBL, CSS or XBL.
+      SBL, CSS or XBL.  It will work with IPv6 addresses if Python's
+      py2-ipaddress module is installed.  The module can be installed via pip
+      if not included in your Python.
 
   i18n
 
-- 
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