accessory: Integrate .plist reading into library

examples/real_airtag.py

@@ -3,13 +3,11 @@ Example showing how to fetch locations of an AirTag, or any other FindMy accesso
 """
 from __future__ import annotations
 
-import plistlib
-from datetime import datetime, timedelta, timezone
 from pathlib import Path
 
 from _login import get_account_sync
 
-from findmy import FindMyAccessory, KeyPair
+from findmy import FindMyAccessory
 from findmy.reports import RemoteAnisetteProvider
 
 # URL to (public or local) anisette server
@@ -18,37 +16,11 @@ ANISETTE_SERVER = "http://localhost:6969"
 # Path to a .plist dumped from the Find My app.
 PLIST_PATH = Path("airtag.plist")
 
-# == The variables below are auto-filled from the plist!! ==
-
-with PLIST_PATH.open("rb") as f:
-    device_data = plistlib.load(f)
-
-# PRIVATE master key. 28 (?) bytes.
-MASTER_KEY = device_data["privateKey"]["key"]["data"][-28:]
-
-# "Primary" shared secret. 32 bytes.
-SKN = device_data["sharedSecret"]["key"]["data"]
-
-# "Secondary" shared secret. 32 bytes.
-SKS = device_data["secondarySharedSecret"]["key"]["data"]
-
-# "Paired at" timestamp (UTC)
-PAIRED_AT = device_data["pairingDate"].replace(tzinfo=timezone.utc)
-
-
-def _gen_keys(airtag: FindMyAccessory, _from: datetime, to: datetime) -> set[KeyPair]:
-    keys = set()
-    while _from < to:
-        keys.update(airtag.keys_at(_from))
-
-        _from += timedelta(minutes=15)
-
-    return keys
-
 
 def main() -> None:
     # Step 0: create an accessory key generator
-    airtag = FindMyAccessory(MASTER_KEY, SKN, SKS, PAIRED_AT)
+    with PLIST_PATH.open("rb") as f:
+        airtag = FindMyAccessory.from_plist(f)
 
     # Step 1: log into an Apple account
     print("Logging into account")

findmy/accessory.py

@@ -6,9 +6,10 @@ Accessories could be anything ranging from AirTags to iPhones.
 from __future__ import annotations
 
 import logging
+import plistlib
 from abc import ABC, abstractmethod
-from datetime import datetime, timedelta
-from typing import Generator, overload
+from datetime import datetime, timedelta, timezone
+from typing import IO, Generator, overload
 
 from typing_extensions import override
 
@@ -143,6 +144,30 @@ class FindMyAccessory(RollingKeyPairSource):
 
         return possible_keys
 
+    @classmethod
+    def from_plist(cls, plist: IO[bytes]) -> FindMyAccessory:
+        """Create a FindMyAccessory from a .plist file dumped from the FindMy app."""
+        device_data = plistlib.load(plist)
+
+        # PRIVATE master key. 28 (?) bytes.
+        master_key = device_data["privateKey"]["key"]["data"][-28:]
+
+        # "Primary" shared secret. 32 bytes.
+        skn = device_data["sharedSecret"]["key"]["data"]
+
+        # "Secondary" shared secret. 32 bytes.
+        if "secondarySharedSecret" in device_data:
+            # AirTag
+            sks = device_data["secondarySharedSecret"]["key"]["data"]
+        else:
+            # iDevice
+            sks = device_data["secureLocationsSharedSecret"]["key"]["data"]
+
+        # "Paired at" timestamp (UTC)
+        paired_at = device_data["pairingDate"].replace(tzinfo=timezone.utc)
+
+        return cls(master_key, skn, sks, paired_at)
+
 
 class AccessoryKeyGenerator(KeyGenerator[KeyPair]):
     """KeyPair generator. Uses the same algorithm internally as FindMy accessories do."""