dns.resolver.zone_for_name() would return the wrong answer sometimes if the response had a CNAME or DNAME

2 files changed, 13 insertions, 5 deletions

diff --git a/ChangeLog b/ChangeLog
index 45a660b..4a06474 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2010-10-31  Bob Halley  <halley@dnspython.org>
 
+	* dns/resolver.py (zone_for_name): A query name resulting in a
+	  CNAME or DNAME response to a node which had an SOA was incorrectly
+	  treated as a zone origin.  In these cases, we should just look
+	  higher.
+
 	* Added zonediff.py to examples.  This program compares two zones
 	  and shows the differences either in diff-like plain text, or
 	  HTML.  Thanks to Dennis Kaarsemaker for contributing this
diff --git a/dns/resolver.py b/dns/resolver.py
index edeac01..f803eb6 100644
--- a/dns/resolver.py
+++ b/dns/resolver.py
@@ -754,9 +754,12 @@ def zone_for_name(name, rdclass=dns.rdataclass.IN, tcp=False, resolver=None):
     while 1:
         try:
             answer = resolver.query(name, dns.rdatatype.SOA, rdclass, tcp)
-            return name
+            if answer.rrset.name == name:
+                return name
+            # otherwise we were CNAMEd or DNAMEd and need to look higher
         except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer):
-            try:
-                name = name.parent()
-            except dns.name.NoParent:
-                raise NoRootSOA
+            pass
+        try:
+            name = name.parent()
+        except dns.name.NoParent:
+            raise NoRootSOA