fix(lease): read the owner's home from the account, not $HOME

scripts/private_owner_allowlist.py

@@ -7,6 +7,7 @@
 import json
 import os
 from pathlib import Path
+import pwd
 import re
 import stat
 import sys
@@ -21,8 +22,17 @@ def allowed(repo, *, environ=None, platform=None, home=None, uid=None):
     """Fail closed on malformed, inaccessible or non-owner Mac runtime policy."""
     env = os.environ if environ is None else environ
     platform = sys.platform if platform is None else platform
-    home = Path.home() if home is None else Path(home)
     uid = os.geteuid() if uid is None else uid
+    # The account's home from the password database, never $HOME: Memo Bridge runs this script
+    # as the ledger child with HOME pointed at a private gh configuration directory
+    # (memo-bridge server/coordinator/credentials.mjs ghChildEnv), so Path.home() would name
+    # that directory and the owner's policy file would never match.
+    if home is None:
+        try:
+            home = pwd.getpwuid(uid).pw_dir
+        except (KeyError, OSError):
+            return False
+    home = Path(home)
     if (platform != "darwin" or env.get("MEMO_BRIDGE_HOST") != "mac" or
             env.get("MEMO_BRIDGE_AGENT_MODE") != "runtime" or
             env.get("MEMO_BRIDGE_MAC_RUNTIME_ENABLED") != "enabled" or

tests/test_private_owner_allowlist.py

@@ -69,5 +69,19 @@ def test_refuses_wrong_schema_extra_keys_and_duplicate_repos(self):
             self.path.chmod(0o600)
             self.assertFalse(self.allowed())
 
+    def test_home_comes_from_the_account_not_the_environment(self):
+        # The Memo Bridge ledger child runs with HOME set to a private gh configuration directory.
+        account = type("pw", (), {"pw_dir": str(self.home)})()
+        with patch.object(policy.pwd, "getpwuid", return_value=account) as lookup, \
+                patch.dict(os.environ, {"HOME": str(self.home / "gh-config")}):
+            self.assertTrue(policy.allowed(CDKF, environ=self.env, platform="darwin", uid=os.geteuid()))
+        lookup.assert_called_once_with(os.geteuid())
+        other = type("pw", (), {"pw_dir": str(self.home / "someone-else")})()
+        with patch.object(policy.pwd, "getpwuid", return_value=other):
+            self.assertFalse(policy.allowed(CDKF, environ=self.env, platform="darwin", uid=os.geteuid()))
+        with patch.object(policy.pwd, "getpwuid", side_effect=KeyError("no such uid")):
+            self.assertFalse(policy.allowed(CDKF, environ=self.env, platform="darwin", uid=os.geteuid()))
+
+
 if __name__ == "__main__":
     unittest.main()