Seal catalog publication Git metadata

tests/test_release_catalog_publication.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import hashlib
 import json
 import os
 from pathlib import Path
@@ -26,12 +27,65 @@ from govoplan_release.publisher import (  # noqa: E402
     verify_committed_publication,
     verify_remote_branch_head,
     verify_remote_publication,
+    _git_bytes,
     _sanitized_git_environment,
+    _seal_git_metadata_file,
     _trusted_npm_command,
 )
 
 
 class ReleaseCatalogPublicationTests(unittest.TestCase):
+    def test_publication_git_writes_ignore_permissive_operator_umask(self) -> None:
+        with tempfile.TemporaryDirectory() as temp_dir:
+            repository = Path(temp_dir) / "website"
+            repository.mkdir()
+            self._git(repository, "init", "--quiet")
+            payload_number = 0
+            while True:
+                payload = f"private publication object {payload_number}\n".encode()
+                header = f"blob {len(payload)}\0".encode()
+                expected_object = hashlib.sha1(
+                    header + payload,
+                    usedforsecurity=False,
+                ).hexdigest()
+                object_parent = repository / ".git" / "objects" / expected_object[:2]
+                if not object_parent.exists():
+                    break
+                payload_number += 1
+
+            previous_umask = os.umask(0o002)
+            try:
+                object_id = (
+                    _git_bytes(
+                        repository,
+                        "hash-object",
+                        "-w",
+                        "--stdin",
+                        input_bytes=payload,
+                    )
+                    .decode("ascii")
+                    .strip()
+                )
+            finally:
+                os.umask(previous_umask)
+
+            object_path = object_parent / expected_object[2:]
+            self.assertEqual(expected_object, object_id)
+            self.assertEqual(os.geteuid(), object_parent.stat().st_uid)
+            self.assertEqual(0o700, object_parent.stat().st_mode & 0o777)
+            self.assertEqual(os.geteuid(), object_path.stat().st_uid)
+            self.assertEqual(0o400, object_path.stat().st_mode & 0o777)
+
+    def test_publication_git_metadata_is_sealed_after_git_writes(self) -> None:
+        with tempfile.TemporaryDirectory() as temp_dir:
+            metadata = Path(temp_dir) / "index"
+            metadata.write_bytes(b"index")
+            metadata.chmod(0o664)
+
+            _seal_git_metadata_file(metadata, label="test index")
+
+            self.assertEqual(0o600, metadata.stat().st_mode & 0o777)
+
     def test_publication_git_identity_is_fixed_and_non_personal(self) -> None:
         with patch.dict(
             os.environ,