From: Bob Halley <halley@dnspython.org>
Date: Mon, 21 Dec 2020 15:11:30 +0000 (-0800)
Subject: resolve_chaining() should not go into an infinite loop if the qtype is
X-Git-Tag: v2.1.0~10
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0cadb332e9946fb404fe70a0ba2775733f6a6824;p=thirdparty%2Fdnspython.git

resolve_chaining() should not go into an infinite loop if the qtype is
CNAME and there is no answer [Issue #610].
---

diff --git a/dns/message.py b/dns/message.py
index 9824e700..5c35dbc7 100644
--- a/dns/message.py
+++ b/dns/message.py
@@ -776,6 +776,9 @@ class QueryMessage(Message):
                     except KeyError:
                         # Exit the chaining loop
                         break
+                else:
+                    # Exit the chaining loop
+                    break
         if count >= MAX_CHAIN:
             raise ChainTooLong
         if self.rcode() == dns.rcode.NXDOMAIN and rrset is not None:
diff --git a/tests/test_message.py b/tests/test_message.py
index 8ebcd054..ec964584 100644
--- a/tests/test_message.py
+++ b/tests/test_message.py
@@ -550,6 +550,20 @@ class MessageTestCase(unittest.TestCase):
         with self.assertRaises(dns.exception.FormError):
             r.resolve_chaining()
 
+    def test_resolve_chaining_no_infinite_loop(self):
+        r = dns.message.from_text('''id 1
+flags QR
+;QUESTION
+www.example. IN CNAME
+;AUTHORITY
+example. 300 IN SOA . . 1 2 3 4 5
+''')
+        # passing is actuall not going into an infinite loop in this call
+        (qname, min_ttl, rrset) = r.resolve_chaining()
+        self.assertEqual(qname, dns.name.from_text('www.example.'))
+        self.assertEqual(min_ttl, 5)
+        self.assertIsNone(rrset)
+
     def test_bad_text_questions(self):
         with self.assertRaises(dns.exception.SyntaxError):
             dns.message.from_text('''id 1