- Return an empty list (as expected) when no AR headers are found or no AR

arc stamps are found and the chain terminated (LP: #1748146)

ChangeLog

@@ -1,6 +1,9 @@
 UNRELEASED Version 0.7.1
     - Update ed25519 tests, including using sample keys from RFC 8032 Section
       7.1 and the sample message from RFC 6376
+    - Return an empty list (as expected) when no AR headers are found or no AR
+      arc stamps are found and the chain terminated (LP: #1748146)
+
 2018-02-07 Version 0.7.0
     - Initial ed25519 implementation based on draft-ietf-dcrup-dkim-crypto
       experimental - IETF draft, design not finalized, See README for details

dkim/__init__.py

@@ -863,7 +863,7 @@ class ARC(DomainSigner):
 
     if len(auth_headers) == 0:
       self.logger.debug("no AR headers found, chain terminated")
-      return b''
+      return []
 
     # consolidate headers
     results_lists = [raw.replace(srv_id + b';', b'').strip() for (raw, parsed) in auth_headers]
@@ -876,7 +876,7 @@ class ARC(DomainSigner):
     arc_results = [res for res in parsed_auth_results.results if res.method == 'arc']
     if len(arc_results) == 0:
       self.logger.debug("no AR arc stamps found, chain terminated")
-      return b''
+      return []
     elif len(arc_results) != 1:
       self.logger.debug("multiple AR arc stamps found, failing chain")
       chain_validation_status = CV_Fail