add --nfc flag to use NFC apdu media

Author: yrichard-ledger

speculos/main.py

@@ -269,6 +269,7 @@ def main(prog=None) -> int:
     parser.add_argument('-t', '--trace', action='store_true', help='Trace syscalls')
     parser.add_argument('-u', '--usb', default='hid', help='Configure the USB transport protocol, '
                                                            'either HID (default) or U2F')
+    parser.add_argument('--nfc', action='store_true', help='Use NFC transport instead of USB')
 
     group = parser.add_argument_group('network arguments')
     group.add_argument('--apdu-port', default=9999, type=int, help='ApduServer TCP port')
@@ -473,7 +474,7 @@ def main(prog=None) -> int:
         use_bagl=use_bagl,
         automation=automation_path,
         automation_server=automation_server,
-        transport=args.usb)
+        transport='nfc' if args.nfc else args.usb)
 
     button = None
     if args.button_port:

speculos/mcu/nfc.py

@@ -0,0 +1,75 @@
+"""
+Forward NFC packets between the MCU and the SE
+"""
+
+from abc import ABC, abstractmethod
+from construct import Int8ub, Int16ub, Int16ul, Struct
+import binascii
+import enum
+import logging
+
+
+class SephNfcTag(enum.IntEnum):
+    NFC_APDU_EVENT = 0x1C
+    NFC_EVENT = 0x1E
+
+
+class NFC:
+    def __init__(self, _queue_event_packet):
+        self._queue_event_packet = _queue_event_packet
+        self.packets_to_send = []
+        self.MTU=140
+        self.rx_sequence = 0
+        self.rx_size = 0
+        self.rx_data = []
+
+        self.logger = logging.getLogger("nfc")
+
+
+    def handle_rapdu_chunk(self, data):
+        """concatenate apdu chunks into full apdu"""
+
+        # example of data
+        # 0000050000002b3330000409312e302e302d72633104e600000008362e312e302d646508352e312e302d6465010001009000
+
+        # only APDU packets are suported
+        if data[2] != 0x05:
+            return None
+
+        sequence = int.from_bytes(data[3:5], 'big')
+        if self.rx_sequence != sequence:
+            print(f"Unexpected sequence number:{sequence}")
+            return None
+
+        if sequence == 0:
+            self.rx_size = int.from_bytes(data[5:7], "big")
+            self.rx_data = data[7:]
+        else:
+            self.rx_data.append(data[5:])
+
+        if len(self.rx_data) == self.rx_size:
+            #prepare for next call
+            self.rx_sequence = 0
+            return self.rx_data
+        
+        return None
+
+
+    def apdu(self, data):
+        chunks: List[bytes] = []
+        data_len = len(data)
+
+        while len(data) > 0:
+            size = self.MTU-5
+            chunks.append(data[:size])
+            data = data[size:]
+
+        for i, chunk in enumerate(chunks):
+            # ledger protocol header
+            header = bytes([0x00, 0x00, 0x05]) # APDU
+            header += i.to_bytes(2, "big")
+            # first packet contains the size of full buffer
+            if i == 0:
+                header += data_len.to_bytes(2, "big")
+
+            self._queue_event_packet(SephNfcTag.NFC_APDU_EVENT, header+chunk)

speculos/mcu/seproxyhal.py

@@ -9,6 +9,7 @@
 
 from speculos.observer import BroadcastInterface, TextEvent
 from . import usb
+from . import nfc
 from .automation import Automation
 from .display import DisplayNotifier, IODevice
 from .nbgl import NBGL
@@ -30,6 +31,9 @@ class SephTag(IntEnum):
     USB_CONFIG = 0x4f
     USB_EP_PREPARE = 0x50
 
+    NFC_RAPDU = 0x4A
+    NFC_POWER = 0x34
+
     REQUEST_STATUS = 0x52
     RAPDU = 0x53
     PLAY_TUNE = 0x56
@@ -261,6 +265,7 @@ def __init__(self,
         self.automation_server = automation_server
         self.events: List[TextEvent] = []
         self.refreshed = False
+        self.transport = transport
 
         self.status_event = threading.Event()
         self.socket_helper = SocketHelper(self._socket, self.status_event)
@@ -270,7 +275,10 @@ def __init__(self,
                                                    self.socket_helper.wait_until_tick_is_processed)
         self.time_ticker_thread.start()
 
-        self.usb = usb.USB(self.socket_helper.queue_packet, transport=transport)
+        usb_transport = transport if transport in ['hid', 'u2f'] else 'hid'
+        self.usb = usb.USB(self.socket_helper.queue_packet, transport=usb_transport)
+
+        self.nfc = nfc.NFC(self.socket_helper.queue_packet)
 
         self.ocr = OCR(model, use_bagl)
 
@@ -449,6 +457,13 @@ def can_read(self, screen: DisplayNotifier):
             assert isinstance(screen.display.gl, NBGL)
             screen.display.gl.hal_draw_image_file(data)
 
+        elif tag == SephTag.NFC_RAPDU:
+            data = self.nfc.handle_rapdu_chunk(data)
+            if data:
+                for c in self.apdu_callbacks:
+                    c(data)
+                screen.display.forward_to_apdu_client(data)
+
         else:
             self.logger.error(f"unknown tag: {tag:#x}")
             sys.exit(0)
@@ -506,7 +521,10 @@ def to_app(self, packet: bytes):
             tag, packet = packet[4], packet[5:]
             self.socket_helper.queue_packet(SephTag(tag), packet)
         else:
-            self.usb.xfer(packet)
+            if self.transport == 'nfc':
+                self.nfc.apdu(packet)
+            else:
+                self.usb.xfer(packet)
 
     def get_tick_count(self):
         return self.socket_helper.get_tick_count()