Authentication with NDEF message on Desfire containing signed UID via Ed25519

write_signed_ndef_on_desfire.py

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+#!/usr/bin/env python
+
+import sys
+import os
+import tempfile
+
+from binascii import hexlify
+
+from nfc_smartcard import NFCDevice, NFCError
+from sign_uid import signUid
+
+if len(sys.argv) < 2:
+    print "Usage: write_signed_ndef_on_desfire.py private_key_in_hex"
+    sys.exit(3)
+
+tempFile = None
+tempFname = None
+
+try:
+    print "Opening NFC reader"
+    nfc = NFCDevice()
+    nfc.pollNr = 0xFF #poll indefinitely
+    print "Waiting for Desfire card to appear in the reader"
+    uid_hex = hexlify(nfc.scanUID())
+    key = sys.argv[1].decode("hex")
+
+    print("Got UID %s", uid_hex)
+    signature = signUid(key, uid_hex.decode("hex"))
+    (tempFile, tempFname) = tempfile.mkstemp(dir="/tmp")
+    with tempFile:
+        tempFile.write(signature)
+except NFCError, e:
+    #this exception happens also when scanUID times out
+    print("Failed to wait for Desfire card: %s" % e)
+    sys.exit(1)
+except Exception, e:
+    print("Something went wrong when writing the signature to file:", e)
+    sys.exit(2)
+finally:
+    nfc.close()
+    nfc.unload()
+    if tempFname:
+        os.unlink(tempFname)
+
+# We'll just call the command line tools so that we don't need to copy&paste the NDEF writing code to nfc_smartcard.cpp
+print "Formatting card"
+res = os.system("mifare-desfire-format -y")
+if res != 0:
+    print "Formatting failed"
+    sys.exit(4)
+print "Creating NDEF file/application"
+res = os.system("mifare-desfire-create-ndef -y")
+if res != 0:
+    print "Creating NDEF failed"
+    sys.exit(4)
+print "Writing NDEF with signature onto Desfire"
+res = os.system("mifare-desfire-create-ndef -y -i '%'" % tempFname)
+if res != 0:
+    print "Writing NDEF failed"
+    sys.exit(4)
+
+print "All done"