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biemster / FindMy

Query Apple's Find My network
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ValueError: Invalid EC key #58

Closed coolcodecding closed 1 month ago

coolcodecding commented 3 months ago

i have generated keys with the provided python script. then i used the ./flash_esp32.sh ADVERTISEMENT_KEY after a few minutes i run request_reports.py but get an error

200: 4 reports received. Traceback (most recent call last): File "/home/myuser/work/openhaystack/findmy/FindMy/request_reports.py", line 88, in <module> eph_key = ec.EllipticCurvePublicKey.from_encoded_point(ec.SECP224R1(), data[5:62]) File "/home/myuser/work/openhaystack/findmy/FindMy/.venv/lib/python3.10/site-packages/cryptography/hazmat/primitives/asymmetric/ec.py", line 183, in from_encoded_point return rust_openssl.ec.from_public_bytes(curve, data) ValueError: Invalid EC key.

Do you know what is the cause of this error and how could it be fixed?

coolcodecding commented 3 months ago

after digging around i found this to work, although i dont now exactly why..

adj = len(data) - 88
eph_key = ec.EllipticCurvePublicKey.from_encoded_point(ec.SECP224R1(), data[5+adj:62+adj])
shared_key = ec.derive_private_key(priv, ec.SECP224R1(), default_backend()).exchange(ec.ECDH(), eph_key)
symmetric_key = sha256(shared_key + b'\x00\x00\x00\x01' + data[5+adj:62+adj])
decryption_key = symmetric_key[:16]
iv = symmetric_key[16:]
enc_data = data[62+adj:72+adj]
tag = data[72+adj:]

Found here https://github.com/MatthewKuKanich/FindMyFlipper/issues/61#issuecomment-2065364739

biemster commented 1 month ago

duplicate of #52