Merge pull request #125 from pajowu/pajowu/aligment

Add option to align FindMyAccessories key generation

examples/real_airtag.py

@@ -4,6 +4,7 @@ Example showing how to fetch locations of an AirTag, or any other FindMy accesso
 
 from __future__ import annotations
 
+import argparse
 import logging
 import sys
 from pathlib import Path
@@ -30,10 +31,15 @@ ANISETTE_LIBS_PATH = "ani_libs.bin"
 logging.basicConfig(level=logging.INFO)
 
 
-def main(plist_path: str) -> int:
+def main(plist_path: Path, alignment_plist_path: Path | None) -> int:
     # Step 0: create an accessory key generator
-    with Path(plist_path).open("rb") as f:
-        airtag = FindMyAccessory.from_plist(f)
+    with plist_path.open("rb") as f:
+        f2 = alignment_plist_path.open("rb") if alignment_plist_path else None
+
+        airtag = FindMyAccessory.from_plist(f, f2)
+
+        if f2:
+            f2.close()
 
     # Step 1: log into an Apple account
     print("Logging into account")
@@ -56,10 +62,9 @@ def main(plist_path: str) -> int:
 
 
 if __name__ == "__main__":
-    if len(sys.argv) < 2:
-        print(f"Usage: {sys.argv[0]} <path to accessory plist>", file=sys.stderr)
-        print(file=sys.stderr)
-        print("The plist file should be dumped from MacOS's FindMy app.", file=sys.stderr)
-        sys.exit(1)
+    parser = argparse.ArgumentParser()
+    parser.add_argument("plist_path", type=Path)
+    parser.add_argument("--alignment_plist_path", default=None, type=Path)
+    args = parser.parse_args()
 
-    sys.exit(main(sys.argv[1]))
+    sys.exit(main(args.plist_path, args.alignment_plist_path))

findmy/accessory.py

@@ -95,6 +95,8 @@ class FindMyAccessory(RollingKeyPairSource, Serializable[FindMyAccessoryMapping]
         name: str | None = None,
         model: str | None = None,
         identifier: str | None = None,
+        alignment_date: datetime | None = None,
+        alignment_index: int | None = None,
     ) -> None:
         """
         Initialize a FindMyAccessory. These values are usually obtained during pairing.
@@ -116,6 +118,14 @@ class FindMyAccessory(RollingKeyPairSource, Serializable[FindMyAccessoryMapping]
         self._name = name
         self._model = model
         self._identifier = identifier
+        self._alignment_date = alignment_date if alignment_date is not None else paired_at
+        self._alignment_index = alignment_index if alignment_index is not None else 0
+        if self._alignment_date.tzinfo is None:
+            self._alignment_date = self._alignment_date.astimezone()
+            logger.warning(
+                "Alignment datetime is timezone-naive. Assuming system tz: %s.",
+                self._alignment_date.tzname(),
+            )
 
     @property
     def master_key(self) -> bytes:
@@ -173,25 +183,27 @@ class FindMyAccessory(RollingKeyPairSource, Serializable[FindMyAccessoryMapping]
         secondary_offset = 0
 
         if isinstance(ind, datetime):
-            # number of 15-minute slots since pairing time
-            ind = (
+            # number of 15-minute slots since alignment
+            slots_since_alignment = (
                 int(
-                    (ind - self._paired_at).total_seconds() / (15 * 60),
+                    (ind - self._alignment_date).total_seconds() / (15 * 60),
                 )
                 + 1
             )
+            ind = self._alignment_index + slots_since_alignment
+
             # number of slots until first 4 am
-            first_rollover = self._paired_at.astimezone().replace(
+            first_rollover = self._alignment_date.astimezone().replace(
                 hour=4,
                 minute=0,
                 second=0,
                 microsecond=0,
             )
-            if first_rollover < self._paired_at:  # we rolled backwards, so increment the day
+            if first_rollover < self._alignment_date:  # we rolled backwards, so increment the day
                 first_rollover += timedelta(days=1)
             secondary_offset = (
                 int(
-                    (first_rollover - self._paired_at).total_seconds() / (15 * 60),
+                    (first_rollover - self._alignment_date).total_seconds() / (15 * 60),
                 )
                 + 1
             )
@@ -213,6 +225,7 @@ class FindMyAccessory(RollingKeyPairSource, Serializable[FindMyAccessoryMapping]
     def from_plist(
         cls,
         plist: str | Path | dict | bytes | IO[bytes],
+        key_alignment_plist: IO[bytes] | None = None,
         *,
         name: str | None = None,
     ) -> FindMyAccessory:
@@ -247,6 +260,16 @@ class FindMyAccessory(RollingKeyPairSource, Serializable[FindMyAccessoryMapping]
         model = device_data["model"]
         identifier = device_data["identifier"]
 
+        alignment_date = None
+        index = None
+        if key_alignment_plist:
+            alignment_data = plistlib.load(key_alignment_plist)
+
+            alignment_date = alignment_data["lastIndexObservationDate"].replace(
+                tzinfo=timezone.utc,
+            )
+            index = alignment_data["lastIndexObserved"]
+
         return cls(
             master_key=master_key,
             skn=skn,
@@ -255,6 +278,8 @@ class FindMyAccessory(RollingKeyPairSource, Serializable[FindMyAccessoryMapping]
             name=name,
             model=model,
             identifier=identifier,
+            alignment_date=alignment_date,
+            alignment_index=index,
         )
 
     @override