PoC of python nas heuristic

tools/nasparse.py

@@ -0,0 +1,52 @@
+#!/usr/bin/python3
+import pycrate_mobile
+from pycrate_mobile import NASLTE
+import pycrate_core
+import binascii
+import sys
+import pprint
+from enum import Enum
+
+import pycrate_mobile.TS24301_EMM
+
+def parse_nas_message(buffer, uplink=None):
+    bin = binascii.unhexlify(buffer)
+    if uplink:
+        parsed = NASLTE.parse_NASLTE_MO(bin)
+    elif uplink == None: #We don't know if its an up or downlink
+        parsed = NASLTE.parse_NASLTE_MO(bin)
+        if parsed[0] == None:
+            parsed = NASLTE.parse_NASLTE_MT(bin)
+    else:
+        parsed = NASLTE.parse_NASLTE_MT(bin)
+    return parsed[0]
+
+def heur_ue_imsi_sent(msg):
+    output = "device transmitted IMSI to base station!"
+
+    if type(msg) not in [pycrate_mobile.TS24301_EMM.EMMAttachRequest, pycrate_mobile.TS24301_EMM.EMMSecProtNASMessage]: 
+        return (False, None)
+
+    if isinstance(msg, pycrate_mobile.TS24301_EMM.EMMSecProtNASMessage):
+        try:
+            msg = msg['EMMAttachRequest']
+        except pycrate_core.elt.EltErr:
+            return (False, None)
+
+    if msg['EPSAttachType']['V'].to_int() == 2:
+        return (True, output)
+    return (False, None)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) != 2:
+        print("usage: nasparse.py [hex encoded nas message]")
+        exit(1)
+        
+    buffer = sys.argv[1]
+    msg = parse_nas_message(buffer)
+    pprint.pprint(msg)
+    res = heur_ue_imsi_sent(msg)
+    if(res[0]): 
+        print(res[1])
+        exit(1)