Adding pico-fido-tool for enabling some configs.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>

tools/pico-fido-tool.py

@@ -0,0 +1,84 @@
+from fido2.ctap2.config import Config
+from fido2.ctap2 import Ctap2
+from fido2.hid import CtapHidDevice
+from fido2.utils import bytes2int, int2bytes
+
+from cryptography.hazmat.primitives.asymmetric import ec
+from cryptography.hazmat.primitives.kdf.hkdf import HKDF
+from cryptography.hazmat.primitives.serialization import Encoding, PublicFormat
+from cryptography.hazmat.primitives.ciphers.aead import ChaCha20Poly1305
+from cryptography.hazmat.primitives import hashes
+
+from enum import IntEnum
+from binascii import hexlify
+
+class VendorConfig(Config):
+
+    class PARAM(IntEnum):
+        VENDOR_COMMAND_ID         = 0x01
+        VENDOR_AUT_KEY_AGREEMENT  = 0x02
+        VENDOR_AUT_CT             = 0x03
+
+    class CMD(IntEnum):
+        CONFIG_AUT           = 0x03e43f56b34285e2
+        CONFIG_KEY_AGREEMENT = 0x1831a40f04a25ed9
+
+    class RESP(IntEnum):
+        KEY_AGREEMENT = 0x01
+
+    def __init__(self, ctap, pin_uv_protocol=None, pin_uv_token=None):
+        super().__init__(ctap, pin_uv_protocol, pin_uv_token)
+
+    def enable_device_aut(self):
+        ret = self._call(
+            Config.CMD.VENDOR_PROTOTYPE,
+            {
+                VendorConfig.PARAM.VENDOR_COMMAND_ID: VendorConfig.CMD.CONFIG_KEY_AGREEMENT,
+            },
+        )
+        peer_cose_key = ret[VendorConfig.RESP.KEY_AGREEMENT]
+
+        sk = ec.generate_private_key(ec.SECP256R1())
+        pn = sk.public_key().public_numbers()
+        pb = sk.public_key().public_bytes(Encoding.X962, PublicFormat.UncompressedPoint)
+        key_agreement = {
+            1: 2,
+            3: -25,  # Per the spec, "although this is NOT the algorithm actually used"
+            -1: 1,
+            -2: int2bytes(pn.x, 32),
+            -3: int2bytes(pn.y, 32),
+        }
+
+        x = bytes2int(peer_cose_key[-2])
+        y = bytes2int(peer_cose_key[-3])
+        pk = ec.EllipticCurvePublicNumbers(x, y, ec.SECP256R1()).public_key()
+        shared_key = sk.exchange(ec.ECDH(), pk)
+
+        xkdf = HKDF(
+            algorithm=hashes.SHA256(),
+            length=12+32,
+            salt=None,
+            info=pb
+        )
+        print(hexlify(shared_key))
+        kdf_out = xkdf.derive(shared_key)
+        key_enc = kdf_out[12:]
+        iv = kdf_out[:12]
+        print(hexlify(kdf_out))
+        print(hexlify(pb))
+        chacha = ChaCha20Poly1305(key_enc)
+        ct = chacha.encrypt(iv, b"\x69"*32, pb)
+        self._call(
+            Config.CMD.VENDOR_PROTOTYPE,
+            {
+                VendorConfig.PARAM.VENDOR_COMMAND_ID: VendorConfig.CMD.CONFIG_AUT,
+                VendorConfig.PARAM.VENDOR_AUT_KEY_AGREEMENT: key_agreement,
+                VendorConfig.PARAM.VENDOR_AUT_CT: ct
+            },
+        )
+
+dev = next(CtapHidDevice.list_devices(), None)
+
+vcfg = VendorConfig(Ctap2(dev))
+
+vcfg.enable_device_aut()