Refactor load_pk_from_dns to reduce code duplication between async and non-async.

dkim/__init__.py

@@ -425,8 +425,7 @@ def fold(header, namelen=0, linesep=b'\r\n'):
             return pre + header
 
 
-def load_pk_from_dns(name, dnsfunc, timeout=5):
+def evaluate_pk(name, s):
-  s = dnsfunc(name, timeout=timeout)
   if not s:
       raise KeyFormatError("missing public key: %s"%name)
   try:
@@ -475,6 +474,12 @@ def load_pk_from_dns(name, dnsfunc, timeout=5):
   return pk, keysize, ktag, seqtlsrpt
 
 
+def load_pk_from_dns(name, dnsfunc=get_txt, timeout=5):
+  s = dnsfunc(name, timeout=timeout)
+  pk, keysize, ktag, seqtlsrpt = evaluate_pk(name, s)
+  return pk, keysize, ktag, seqtlsrpt
+
+
 #: Abstract base class for holding messages and options during DKIM/ARC signing and verification.
 class DomainSigner(object):
   # NOTE - the first 2 indentation levels are 2 instead of 4

dkim/asyncsupport.py

@@ -59,7 +59,6 @@ async def get_txt_async(name, timeout=5):
         result = await query(name, 'TXT')
     except aiodns.error.DNSError:
         result = None
-    print('result', result)
 
     if result:
         return result[0].text
@@ -69,51 +68,7 @@ async def get_txt_async(name, timeout=5):
 
 async def load_pk_from_dns_async(name, dnsfunc, timeout=5):
   s = await dnsfunc(name, timeout=timeout)
-  if not s:
+  pk, keysize, ktag, seqtlsrpt = dkim.evaluate_pk(name, s)
-      raise dkim.KeyFormatError("missing public key: %s"%name)
-  try:
-      if type(s) is str:
-        s = s.encode('ascii')
-      pub = dkim.parse_tag_value(s)
-  except dkim.InvalidTagValueList as e:
-      raise dkim.KeyFormatError(e)
-  try:
-      if pub[b'v'] != b'DKIM1':
-          raise dkim.KeyFormatError("bad version")
-  except KeyError as e:
-      # Version not required in key record: RFC 6376 3.6.1
-      pass
-  try:
-      if pub[b'k'] == b'ed25519':
-          pk = nacl.signing.VerifyKey(pub[b'p'], encoder=nacl.encoding.Base64Encoder)
-          keysize = 256
-          ktag = b'ed25519'
-  except KeyError:
-      pub[b'k'] = b'rsa'
-  if pub[b'k'] == b'rsa':
-      try:
-          pk = dkim.parse_public_key(base64.b64decode(pub[b'p']))
-          keysize = dkim.bitsize(pk['modulus'])
-      except KeyError:
-          raise dkim.KeyFormatError("incomplete public key: %s" % s)
-      except (TypeError,dkim.UnparsableKeyError) as e:
-          raise dkim.KeyFormatError("could not parse public key (%s): %s" % (pub[b'p'],e))
-      ktag = b'rsa'
-  if pub[b'k'] != b'rsa' and pub[b'k'] != b'ed25519':
-      raise dkim.KeyFormatError('unknown algorithm in k= tag: {0}'.format(pub[b'k']))
-  seqtlsrpt = False
-  try:
-      # Ignore unknown service types, RFC 6376 3.6.1
-      if pub[b's'] != b'*' and pub[b's'] != b'email' and pub[b's'] != b'tlsrpt':
-          pk = None
-          keysize = None
-          ktag = None
-          raise dkim.KeyFormatError('unknown service type in s= tag: {0}'.format(pub[b's']))
-      elif pub[b's'] == b'tlsrpt':
-          seqtlsrpt = True
-  except:
-      # Default is '*' - all service types, so no error if missing from key record
-      pass
   return pk, keysize, ktag, seqtlsrpt
 
 class DKIM(dkim.DKIM):