From 79722177560725652b4844a8e68662ff7744a09a Mon Sep 17 00:00:00 2001
From: Scott Kitterman <scott@kitterman.com>
Date: Tue, 5 Nov 2019 21:36:06 -0500
Subject: [PATCH] DKIM.verify: Refactor to minimize code duplication in
 dkim.asyncsupport.

---
 dkim/__init__.py     | 25 ++++++++++++++++---------
 dkim/asyncsupport.py | 21 +--------------------
 2 files changed, 17 insertions(+), 29 deletions(-)

diff --git a/dkim/__init__.py b/dkim/__init__.py
index ce84159..720af97 100644
--- a/dkim/__init__.py
+++ b/dkim/__init__.py
@@ -888,15 +888,11 @@ class DKIM(DomainSigner):
     self.signature_fields = dict(sigfields)
     return b'DKIM-Signature: ' + res
 
-  #: Verify a DKIM signature.
-  #: @type idx: int
-  #: @param idx: which signature to verify.  The first (topmost) signature is 0.
-  #: @type dnsfunc: callable
-  #: @param dnsfunc: an option function to lookup TXT resource records
-  #: for a DNS domain.  The default uses dnspython or pydns.
-  #: @return: True if signature verifies or False otherwise
-  #: @raise DKIMException: when the message, signature, or key are badly formed
-  def verify(self,idx=0,dnsfunc=get_txt):
+
+  def verify_headerprep(self, idx=0):
+    """Non-DNS verify parts to minimize asyncio code duplication."""
+
+
     sigheaders = [(x,y) for x,y in self.headers if x.lower() == b"dkim-signature"]
     if len(sigheaders) <= idx:
         return False
@@ -916,7 +912,18 @@ class DKIM(DomainSigner):
 
     include_headers = [x.lower() for x in re.split(br"\s*:\s*", sig[b'h'])]
     self.include_headers = tuple(include_headers)
+    return sig, include_headers, sigheaders
 
+  #: Verify a DKIM signature.
+  #: @type idx: int
+  #: @param idx: which signature to verify.  The first (topmost) signature is 0.
+  #: @type dnsfunc: callable
+  #: @param dnsfunc: an option function to lookup TXT resource records
+  #: for a DNS domain.  The default uses dnspython or pydns.
+  #: @return: True if signature verifies or False otherwise
+  #: @raise DKIMException: when the message, signature, or key are badly formed
+  def verify(self,idx=0,dnsfunc=get_txt):
+    sig, include_headers, sigheaders = self.verify_headerprep(idx=0)
     return self.verify_sig(sig, include_headers, sigheaders[idx], dnsfunc)
 
 
diff --git a/dkim/asyncsupport.py b/dkim/asyncsupport.py
index dc856af..226cc42 100644
--- a/dkim/asyncsupport.py
+++ b/dkim/asyncsupport.py
@@ -94,26 +94,7 @@ class DKIM(dkim.DKIM):
 
 
   async def verify(self,idx=0,dnsfunc=get_txt_async):
-    sigheaders = [(x,y) for x,y in self.headers if x.lower() == b"dkim-signature"]
-    if len(sigheaders) <= idx:
-        return False
-
-    # By default, we validate the first DKIM-Signature line found.
-    try:
-        sig = dkim.parse_tag_value(sigheaders[idx][1])
-        self.signature_fields = sig
-    except dkim.InvalidTagValueList as e:
-        raise dkim.MessageFormatError(e)
-
-    self.logger.debug("sig: %r" % sig)
-
-    dkim.validate_signature_fields(sig)
-    self.domain = sig[b'd']
-    self.selector = sig[b's']
-
-    include_headers = [x.lower() for x in re.split(br"\s*:\s*", sig[b'h'])]
-    self.include_headers = tuple(include_headers)
-
+    sig, include_headers, sigheaders = self.verify_headerprep(idx=0)
     return await self.verify_sig(sig, include_headers, sigheaders[idx], dnsfunc)