Fix nsec3_hash() with salt==None.

The documentation claims that it supports salt==None, but it caused a
TypeError.

diff --git a/dns/dnssec.py b/dns/dnssec.py
index bf5ce1e8556d8dbc6fa4342137b9293e42e2ea25..0e3143d87e28a544df6c9b7f060c2885e9001df9 100644 (file)
--- a/dns/dnssec.py
+++ b/dns/dnssec.py
@@ -548,7 +548,9 @@ def nsec3_hash(domain, salt, iterations, algorithm):
         raise ValueError("Wrong hash algorithm (only SHA1 is supported)")
 
     salt_encoded = salt
-    if isinstance(salt, str):
+    if salt is None:
+        salt_encoded = b''
+    elif isinstance(salt, str):
         if len(salt) % 2 == 0:
             salt_encoded = bytes.fromhex(salt)
         else: