Allow callers to override the DNS function used by verify().

dkim/__init__.py

@@ -396,7 +396,7 @@ def sign(message, selector, domain, privkey, identity=None, canonicalize=(Simple
 
     return sig + "\r\n"
 
-def verify(message, debuglog=None):
+def verify(message, debuglog=None, dnsfunc=dnstxt):
     """Verify a DKIM signature on an RFC822 formatted message.
 
     @param message: an RFC822 formatted message (with either \\n or \\r\\n line endings)
@@ -548,7 +548,7 @@ def verify(message, debuglog=None):
             print >>debuglog, "body hash mismatch (got %s, expected %s)" % (base64.b64encode(bodyhash), sig['bh'])
         return False
 
-    s = dnstxt(sig['s']+"._domainkey."+sig['d']+".")
+    s = dnsfunc(sig['s']+"._domainkey."+sig['d']+".")
     if not s:
         return False
     a = re.split(r"\s*;\s*", s)