Follow CNAMES when looking up key records when using DNS (pydns)

(LP: #1856421)

ChangeLog

@@ -1,3 +1,7 @@
+Version 1.0.1
+    - Follow CNAMES when looking up key records when using DNS (pydns)
+      (LP: #1856421)
+
 2019-12-09 Version 1.0.0
     - Add support for RFC 8460 tlsrpt DKIM signature processing (LP: #1847020)
     - Add async support with aiodns for DKIM verification (ARC not supported)

dkim/dnsplug.py

@@ -44,7 +44,10 @@ def get_txt_pydns(name, timeout=5):
     response = DNS.DnsRequest(name, qtype='txt', timeout=timeout).req()
     if not response.answers:
         return None
-    return b''.join(response.answers[0]['data'])
+    for answer in response.answers:
+        if answer['typename'].lower() == 'txt':
+            return b''.join(answer['data'])
+    return None
 
 
 # No longer used since it doesn't support timeout