Authentication with NDEF message on Desfire containing signed UID via Ed25519

README.md

@@ -28,10 +28,16 @@ It is much more general in use than to use it as authenthicator to open door.
 
 You need just to run `make`. Additional dependencies:
 
-- [libnfc](https://github.com/nfc-tools/libnfc/releases), already present in Raspbian 8 repositories
+- [libnfc](https://github.com/nfc-tools/libnfc/releases), in Debian and Ubuntu as libnfc-dev
+- [libfreefare](https://github.com/nfc-tools/libfreefare), in Debian and Ubuntu install libfreefare-bin and libfreefare-dev
+- [python-axolotl-curve25519](https://github.com/tgalal/python-axolotl-curve25519), in Ubuntu and Debian install python-axolotl-curve25519
 - [SWIG](http://www.swig.org/)
 - [WiringPi2 pythonic binding](https://github.com/WiringPi/WiringPi2-Python) (for switching lock on Raspberry)
 
+All dependencies except for wiring can be installed via:
+
+`apt install libnfc-dev libfreefare-bin and libfreefare-dev python-axolotl-curve25519 swig3.0`
+
 ## Howto
 
 1. Create the database
@@ -44,18 +50,29 @@ You need just to run `make`. Additional dependencies:
 
 3. Add some users
 
-  - either authenthication by UID, e.g.:
+  - either authentication by UID, e.g.:
 
-        brmdoor_adduser.py -c brmdoor_nfc.config -a uid 34795FCC SomeUserName
+        ./brmdoor_adduser.py -c brmdoor_nfc.config -a uid 34795FCC SomeUserName
 
-  - authenthication by Yubikey's HMAC-SHA1 programmed on slot 2
+  - authentication by Yubikey's HMAC-SHA1 programmed on slot 2
 
-        brmdoor_adduser.py -c brmdoor_nfc.config -a hmac 40795FCCAB0701 SomeUserName 000102030405060708090a0b0c0d0e0f31323334
+        ./brmdoor_adduser.py -c brmdoor_nfc.config -a hmac 40795FCCAB0701 SomeUserName 000102030405060708090a0b0c0d0e0f31323334
 
-  - to program Yubikey slot 2 to use HMAC with given key, use:
+  - to program Yubikey slot 2 to use HMAC with given key (requires package `yubikey-personalization`), use:
 
         ykpersonalize -2 -ochal-resp -ohmac-sha1 -ohmac-lt64 -oserial-api-visible
         
+  - authentication using signed UID as NDEF message on Desfire:
+  
+        ./brmdoor_adduser.py -c brmdoor.config -a ndef 04631982cc2280 SomeUserName"
+  
+  - you need to generate Ed25519 keypair, store the private key somewhere safe and put the public in config file
+  
+        ./generate_ed25519_keypair.py
+        
+  - you need to program the Desfire card to have the signature
+       
+
 Finally, run the daemon:
 
         sudo python brmdoor_nfc_daemon.py brmdoor_nfc.config

brmdoor_adduser.py

@@ -27,7 +27,6 @@ def addUidAuth(cursor, uid_hex, nick):
         print >> sys.stderr, "UID must be in proper hex encoding"
         sys.exit(1)
         
-
 def addHmacAuth(cursor, uid_hex, nick, key_hex):
     """
     Add user authenticated by Yubikey HMAC-SHA1. UID should be in hex, 4, 7
@@ -48,12 +47,28 @@ def addHmacAuth(cursor, uid_hex, nick, key_hex):
         print >> sys.stderr, "UID and key must be in proper hex encoding"
         sys.exit(1)
 
+def addNdefAuth(cursor, uid_hex, nick):
+    """
+    Add user authenticated by NDEF message on Desfire. UID should be in hex, 4, 7 or 10 bytes long.
+    """
+    try:
+        uid_hex.decode("hex")
+        sql = """INSERT INTO authorized_desfires
+            (uid_hex, nick)
+            values (?, ?)
+        """
+        sql_data = (uid_hex, nick)
+        cursor.execute(sql, sql_data)
+    except TypeError:
+        print >> sys.stderr, "UID must be in proper hex encoding"
+        sys.exit(1)
+
 if __name__ == "__main__":
     parser = OptionParser()
     parser.add_option("-c", "--config", action="store", type="string", dest="config",
         help="Configuration file")
     parser.add_option("-a", "--authtype", action="store", type="string", dest="authtype",
-        help="Authenthication type - uid or hmac")
+        help="Authenthication type - uid, hmac or ndef")
     (opts, args) = parser.parse_args()
 
     if opts.config is None:
@@ -61,9 +76,9 @@ if __name__ == "__main__":
         parser.print_help()
         sys.exit(1)
         
-    if opts.authtype not in ["uid", "hmac"]:
+    if opts.authtype not in ["uid", "hmac", "ndef"]:
         print >> sys.stderr, "You must specify authentication type via -a option!"
-        print >> sys.stderr, "Acceptable choices: uid, hmac"
+        print >> sys.stderr, "Acceptable choices: uid, hmac, ndef"
         sys.exit(1)
         
     config = BrmdoorConfig(opts.config)
@@ -83,6 +98,13 @@ if __name__ == "__main__":
             print >> sys.stderr, "brmdoor_adduser.py -c brmdoor.config -a hmac 40795FCCAB0701 SomeUserName 000102030405060708090a0b0c0d0e0f31323334"
             sys.exit(1)
         addHmacAuth(cursor, args[0], args[1], args[2])
+    elif opts.authtype == "ndef":
+        if len(args) < 2:
+            print >> sys.stderr, "You must two additional arguments, hex UID and nick"
+            print >> sys.stderr, "Example:"
+            print >> sys.stderr, "brmdoor_adduser.py -c brmdoor.config -a ndef 34795FCC SomeUserName"
+            sys.exit(1)
+    addNdefAuth(cursor, args[0], args[1])
 
     conn.commit()
     conn.close()

brmdoor_authenticator.py

@@ -4,6 +4,8 @@ import hmac
 import hashlib
 import logging
 
+import axolotl_curve25519 as curve
+
 from nfc_smartcard import NFCError
 
 
@@ -128,7 +130,7 @@ class YubikeyHMACAuthenthicator(object):
                 if not rapdu.valid or rapdu.sw() != 0x9000:
                     raise NFCError("HMAC - response SW is not 0x9000")
             except NFCError, e:
-                logging.debug("Yubikey HMAC command failed: %s" % e.what())
+                logging.info("Yubikey HMAC command failed: %s" % e.what())
                 return None
             
         if not self.hmacCheck(secretKey, challenge, rapdu.data()):
@@ -141,6 +143,61 @@ class YubikeyHMACAuthenthicator(object):
         """Closes connection to database"""
         self.conn.close()
 
+class DesfireEd25519Authenthicator(object):
+    """
+    Reads NDEF message from Desfire and it must be signed binary value of UID
+    """
+    def __init__(self, filename, nfcReader, pubKey):
+        """
+        Connects to database by given filename and later checks UIDs
+        using the pubkey (given as binary string).
+        """
+        #again autocommit mode
+        self.conn = sqlite3.connect(filename, isolation_level=None)
+        self.nfcReader = nfcReader
+        self.pubKey = pubKey
+
+    def signatureCheck(self, uid, signature):
+        """
+        Returns true iff uid (as binary) is the message signed by signature (binary string)
+        """
+        verified = curve.verifySignature(self.pubKey, uid, signature) == 0
+        return verified
+
+
+    def checkUIDSignature(self, uid_hex):
+        """
+        Checks if UID is in database. If so, it retrieves NDEF which should be signature of the UID
+        @param uid_hex: uid to match in hex
+        @returns UidRecord instance if found, None otherwise
+        """
+        cursor = self.conn.cursor()
+        sql = "SELECT nick FROM authorized_desfires WHERE UPPER(uid_hex)=?"
+        sql_data =(uid_hex.upper(),)
+
+        cursor.execute(sql, sql_data)
+        record = cursor.fetchone()
+
+        if record is None:
+            return None
+
+        nick = record[0]
+
+        try:
+            ndefSignature = self.nfcReader.readDesfireNDEF()
+            if self.signatureCheck(uid_hex.decode("hex"), ndefSignature):
+                return UidRecord(uid_hex, nick)
+            else:
+                logging.info("Signature check failed for Desfire NDEF for UID %s", uid_hex)
+                return None
+        except NFCError, e:
+            logging.info("Desfire read NDEF failed: %s" % e.what())
+            return None
+
+    def shutdown(self):
+        """Closes connection to database"""
+        self.conn.close()
+
 #test routine
 if __name__ == "__main__":
     authenticator = UidAuthenticator("test_uids_db.sqlite")

brmdoor_nfc.config.sample

@@ -8,6 +8,8 @@
 #	Unlocker is just dummy test class. 
 [brmdoor]
 auth_db_filename = test_uids_db.sqlite
+#corresponding private key = 10ee85f987e7682d9acf24ab07ff0e302ee4cdd426f83a055d3a337a4f01314b
+desfire_ed25519_pubkey = 4c625187d79fdee97a6af48cb8f854e7f313c8158de94e667e1509bd26617d27
 #lock_opened_secs = 5
 #unknown_uid_timeout_secs = 5
 log_file = -

brmdoor_nfc_daemon.py

@@ -9,7 +9,7 @@ from binascii import hexlify
 
 
 from nfc_smartcard import NFCDevice, NFCError
-from brmdoor_authenticator import UidAuthenticator, YubikeyHMACAuthenthicator
+from brmdoor_authenticator import UidAuthenticator, YubikeyHMACAuthenthicator, DesfireEd25519Authenthicator
 import unlocker
 
 class BrmdoorConfigError(ConfigParser.Error):
@@ -40,6 +40,7 @@ class BrmdoorConfig(object):
         self.config.read(filename)
         
         self.authDbFilename = self.config.get("brmdoor", "auth_db_filename")
+        self.desfirePubkey = self.config.get("brmdoor", "desfire_ed25519_pubkey")
         self.lockOpenedSecs = self.config.getint("brmdoor", "lock_opened_secs")
         self.unknownUidTimeoutSecs = self.config.getint("brmdoor", "unknown_uid_timeout_secs")
         self.logFile = self.config.get("brmdoor", "log_file")
@@ -65,6 +66,7 @@ class NFCScanner(object):
         """
         self.authenticator = UidAuthenticator(config.authDbFilename)
         self.hmacAuthenticator = None
+        self.desfireAuthenticator = None
         self.unknownUidTimeoutSecs = config.unknownUidTimeoutSecs
         self.lockOpenedSecs = config.lockOpenedSecs
         
@@ -82,6 +84,10 @@ class NFCScanner(object):
         self.hmacAuthenticator = YubikeyHMACAuthenthicator(
             config.authDbFilename, self.nfc
         )
+        self.desfireAuthenticator = DesfireEd25519Authenthicator(
+            config.authDbFilename, self.nfc,
+            config.desfirePubkey
+        )
         #self.nfc.pollNr = 0xFF #poll indefinitely
         while True:
             try:
@@ -125,6 +131,14 @@ class NFCScanner(object):
             self.unlocker.unlock()
             return
 
+        #test for Desfire NDEF auth
+        record = self.desfireAuthenticator.checkUIDSignature(uid_hex)
+
+        if record is not None:
+            logging.info("Unlocking after Desfire NDEF ed25519 check for UID %s", record)
+            self.unlocker.unlock()
+            return
+
         logging.info("Unknown UID %s", uid_hex)
         time.sleep(self.unknownUidTimeoutSecs)
         

create_authenticator_db.py

@@ -28,5 +28,10 @@ if __name__ == "__main__":
                key_hex TEXT,
                nick TEXT)
     """)
+    cursor.execute("""CREATE TABLE authorized_desfires(
+        id INTEGER PRIMARY KEY AUTOINCREMENT,
+        uid_hex TEXT,
+        nick TEXT)
+    """)
     conn.commit()
     conn.close()

generate_ed25519_keypair.py

@@ -0,0 +1,19 @@
+#!/usr/bin/env python2
+
+"""
+Used to generate keypair for signing NDEF messages for Mifare NDEF authentication
+"""
+
+import os
+import axolotl_curve25519 as curve
+
+from binascii import hexlify
+
+random32 = os.urandom(32)
+
+private_key = curve.generatePrivateKey(random32)
+public_key = curve.generatePublicKey(private_key)
+
+print "private key in hex:", hexlify(private_key)
+print "public key in hex :", hexlify(public_key)
+

sign_uid.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python2
+
+import sys
+import os
+import axolotl_curve25519 as curve
+
+def signUid(private_key, uid):
+    """
+    Create an Ed25519 signature for UID
+    :param private_key: Binary representation of Ed25519 key
+    :param uid: UID, decoded to binary from hex
+    :return: singature in binary format
+    """
+    random64 = os.urandom(64)
+    signature = curve.calculateSignature(random64, private_key, uid)
+    return signature
+
+if __name__ == "__main__":
+
+    if len(sys.argv) < 3:
+        print >> sys.stderr, "Usage: sign_uid.py uid_hex ed25519_private_key_hex"
+        print >> sys.stderr, "Outputs binary signature, you will probably want to redirect it to a file"
+        sys.exit(1)
+
+    private_key = sys.argv[3].decode("hex")
+    uid_bin = sys.argv[1].decode("hex")
+    sys.stdout.write(signUid(private_key, uid_bin))

test_nfc.py

@@ -51,10 +51,11 @@ print "Available tests: %s" % ", ".join(sorted(tests.keys()))
 print "Selected test: %s" % apdu_test
 
 # select apdus according to test name
-hex_apdus = tests[apdu_test]
-apdus = [hex_apdu.replace(" ","").decode("hex") for hex_apdu in hex_apdus]
+if apdu_test in tests:
+    hex_apdus = tests[apdu_test]
+    apdus = [hex_apdu.replace(" ","").decode("hex") for hex_apdu in hex_apdus]
 
-try:
+    try:
         nfc = NFCDevice()
         uid = nfc.scanUID()
         print "UID", hexlify(uid)
@@ -76,5 +77,22 @@ try:
         nfc.close()
         print "Device is opened:", nfc.opened()
         nfc.unload()
-except NFCError, e:
+    except NFCError, e:
+        print "Reading UID failed:", e.what()
+elif apdu_test == "desfire-ndef4":
+    try:
+        nfc = NFCDevice()
+        uid = nfc.scanUID()
+        print "UID", hexlify(uid)
+        #nfc.close()
+        #nfc.open()
+
+        ndef = nfc.readDesfireNDEF()
+        print ndef
+        print "Device is opened:", nfc.opened()
+        print "Closing device"
+        nfc.close()
+        print "Device is opened:", nfc.opened()
+        nfc.unload()
+    except NFCError, e:
         print "Reading UID failed:", e.what()

unlocker.py

@@ -1,5 +1,4 @@
 import time
-import wiringpi2 as wiringpi
 
 class Unlocker(object):
     """Abstract class/interface for Unlocker object.
@@ -35,6 +34,7 @@ class UnlockerWiringPi(Unlocker):
     """
 
     def __init__(self, config):
+        import wiringpi2 as wiringpi
         Unlocker.__init__(self, config)
         wiringpi.wiringPiSetupGpio() # pin numbers follow P1 GPIO header
         self.lockPin = self.config.getint("UnlockerWiringPi", "lock_pin")
@@ -43,6 +43,7 @@ class UnlockerWiringPi(Unlocker):
     def unlock(self):
         """Unlocks lock at configured pin by pulling it high.
         """
+        import wiringpi2 as wiringpi
         wiringpi.digitalWrite(self.lockPin, 1)
         time.sleep(self.lockOpenedSecs)
         wiringpi.digitalWrite(self.lockPin, 0)
@@ -52,5 +53,6 @@ class UnlockerWiringPi(Unlocker):
         Lock the lock back. Meant to be used when program is shut down
         so that lock is not left disengaged.
         """
+        import wiringpi2 as wiringpi
         wiringpi.digitalWrite(self.lockPin, 0)
 

write_signed_ndef_on_desfire.py

@@ -0,0 +1,62 @@
+#!/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"