Support SHA* based authenticators

Author: Guillaume Valadon

scapy/layers/ntp.py

@@ -452,10 +452,10 @@ def guess_payload_class(self, payload):
         """
         plen = len(payload)
 
-        if plen > _NTP_AUTH_MD5_TAIL_SIZE:
-            return NTPExtensions
-        elif plen == _NTP_AUTH_MD5_TAIL_SIZE:
+        if plen - 4 in [16, 20, 32, 64]:  # length of MD5, SHA1, SHA256, SHA512
             return NTPAuthenticator
+        elif plen > _NTP_AUTH_MD5_TAIL_SIZE:
+            return NTPExtensions
 
         return Packet.guess_payload_class(self, payload)
 

test/regression.uts

@@ -9579,6 +9579,12 @@ assert(p.version == 4)
 assert(p.mode == 3)
 assert(p.stratum == 2)
 
+= NTPAuthenticator
+
+s = hex_bytes("000c2962f268d094666d23750800450000640db640004011a519c0a80364c0a80305a51e007b0050731a2300072000000000000000000000000000000000000000000000000000000000000000000000000052c7bc1dda64b97d0000000bcdc3825dbf6b7ad02886ff45aa8b2eaf7ac78bc1")
+p = Ether(s)
+assert NTPAuthenticator in p and p[NTPAuthenticator].key_id == 3452142173
+
 
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