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Fix accessory key generation

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This commit is contained in:
Mike A
2024-02-07 17:45:40 +01:00
parent d4a5fcef10
commit 612fe63408
2 changed files with 21 additions and 11 deletions
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26
examples/real_airtag.py
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@@ -4,25 +4,35 @@ Example showing how to retrieve the primary key of your own AirTag, or any other
This key can be used to retrieve the device's location for a single day.
"""
import plistlib
from datetime import datetime
from findmy import FindMyAccessory
# PUBLIC key that the accessory is broadcasting or has previously broadcast.
# For nearby devices, you can use `device_scanner.py` to find it.
LOOKUP_KEY = "9J5sdEARfh6h0Hr3anfNjy+vnIwETaUodv73ZA=="
PUBLIC_KEY = ""
# Path to a .plist dumped from the Find My app.
PLIST_PATH = "airtag.plist"
# == The variables below are auto-filled from the plist!! ==
with open(PLIST_PATH, "rb") as f:
device_data = plistlib.load(f)
# PRIVATE master key. 28 (?) bytes.
MASTER_KEY = b""
MASTER_KEY = device_data["privateKey"]["key"]["data"][-28:]
# "Primary" shared secret. 32 bytes.
SKN = b""
SKN = device_data["sharedSecret"]["key"]["data"]
# "Secondary" shared secret. 32 bytes.
SKS = b""
SKS = device_data["secondarySharedSecret"]["key"]["data"]
# Lookahead in time slots. Each time slot is 15 minutes.
# Should be AT LEAST the time that has passed since you paired the accessory!
MAX_LOOKAHEAD = 7 * 24 * 4
delta = datetime.now() - device_data["pairingDate"]
MAX_LOOKAHEAD = int(delta.total_seconds() / (15 * 60)) + 1
def main() -> None:
@@ -30,13 +40,13 @@ def main() -> None:
for i in range(MAX_LOOKAHEAD):
prim_key, sec_key = airtag.keys_at(i)
if LOOKUP_KEY in (prim_key.adv_key_b64, prim_key.adv_key_b64):
if PUBLIC_KEY in (prim_key.adv_key_b64, prim_key.adv_key_b64):
print("KEY FOUND!!")
print(f"This key was found at index {i}."
f" It was likely paired approximately {i * 15} minutes ago")
f" It was likely paired approximately {i * 15} minutes ago.")
print()
print("KEEP THE BELOW KEY SECRET! IT CAN BE USED TO RETRIEVE THE DEVICE'S LOCATION!")
if prim_key.adv_key_b64 == LOOKUP_KEY:
if prim_key.adv_key_b64 == PUBLIC_KEY:
print(f"PRIMARY key: {prim_key.private_key_b64}")
else:
print(f"SECONDARY key: {sec_key.private_key_b64}")

6
findmy/util/crypto.py
View File

@@ -1,7 +1,7 @@
"""Pure-python NIST P-224 Elliptic Curve cryptography. Used for some Apple algorithms."""
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives.asymmetric import ec
from cryptography.hazmat.primitives.hashes import SHA1
from cryptography.hazmat.primitives.kdf.x963kdf import X963KDF
ECPoint = tuple[float, float]
@@ -71,7 +71,7 @@ P224_P = 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF000000000000000000000001
def x963_kdf(value: bytes, si: bytes, length: int) -> bytes:
"""Single pass of X9.63 KDF with SHA1."""
return X963KDF(
algorithm=SHA1(), # noqa: S303
algorithm=hashes.SHA256(),
sharedinfo=si,
length=length,
).derive(value)
@@ -86,7 +86,7 @@ def derive_ps_key(privkey: bytes, sk: bytes) -> bytes:
"""
Derive a primary or secondary key used by an accessory.
:param pubkey: Public key generated during pairing
:param privkey: Private key generated during pairing
:param sk: Current secret key for this time period.
Use SKN to derive the primary key, SKS for secondary.
"""