Add another RFC data based test

dkim/tests/data/rfc6376.signed.msg

@@ -0,0 +1,19 @@
+DKIM-Signature: v=1; a=ed25519-sha256; c=simple/simple; 
+ d=football.example.com; i=@football.example.com; 
+ q=dns/txt; s=brisbane; t=1518460054; h=from : to : 
+ subject : date : message-id : from : subject : date; 
+ bh=4bLNXImK9drULnmePzZNEBleUanJCX5PIsDIFoH4KTQ=; 
+ b=9/dsDChY0YMTtD5Eyw3wx7x22BlSJP7M5ECbJ7GWrR45nXlTCGb8l0YB
+ o0wBLR++X5LqmsxXaOYLLJe46l10AQ==
+From: Joe SixPack <joe@football.example.com>
+To: Suzie Q <suzie@shopping.example.net>
+Subject: Is dinner ready?
+Date: Fri, 11 Jul 2003 21:00:37 -0700 (PDT)
+Message-ID: <20030712040037.46341.5F8J@football.example.com>
+
+Hi.
+
+We lost the game.  Are you hungry yet?
+
+Joe.
+

dkim/tests/test_dkim_ed25519.py

@@ -55,6 +55,7 @@ class TestSignAndVerify(unittest.TestCase):
         self.message = read_test_data("ed25519test.msg")
         self.message2 = read_test_data("ed25519test2.msg")
         self.message3 = read_test_data("rfc6376.msg")
+        self.message4 = read_test_data("rfc6376.signed.msg")
         self.key = read_test_data("ed25519test.key")
         self.rfckey = read_test_data("rfc8032_7_1.key")
 
@@ -98,6 +99,19 @@ p=11qYAYKxCrfVS/7TyWQHOg7hcvPapiMlrwIaaPcHURo="""
                 res = dkim.verify(sig + self.message3, dnsfunc=self.dnsfunc)
                 self.assertTrue(res)
 
+    def test_rfc8032_previous_verifies(self):
+        # A message previously signed using RFC 8032 sample keys verifies after being signed.
+        for header_algo in (b"simple", b"relaxed"):
+            for body_algo in (b"simple", b"relaxed"):
+                sig = dkim.sign(
+                    self.message3, b"brisbane", b"football.example.com", self.rfckey,
+                    canonicalize=(header_algo, body_algo), signature_algorithm=b'ed25519-sha256')
+                print(header_algo, body_algo)
+                print(sig)
+                d = dkim.DKIM(self.message4)
+                res = d.verify(dnsfunc=self.dnsfunc)
+                self.assertTrue(res)
+
     def test_simple_signature(self):
         # A message verifies after being signed with SHOULD headers
         for header_algo in (b"simple", b"relaxed"):