fix(state): restrict sensitive store file permissions (salvage #30917)

gateway/platforms/api_server.py

@@ -35,6 +35,7 @@
 import sqlite3
 import time
 import uuid
+from pathlib import Path
 from typing import Any, Dict, List, Optional
 
 try:
@@ -337,10 +338,12 @@ def __init__(self, max_size: int = MAX_STORED_RESPONSES, db_path: str = None):
                 db_path = str(get_hermes_home() / "response_store.db")
             except Exception:
                 db_path = ":memory:"
+        self._db_path: Optional[str] = db_path if db_path != ":memory:" else None
         try:
             self._conn = sqlite3.connect(db_path, check_same_thread=False)
         except Exception:
             self._conn = sqlite3.connect(":memory:", check_same_thread=False)
+            self._db_path = None
         # Use shared WAL-fallback helper so response_store.db degrades
         # gracefully on NFS/SMB/FUSE-mounted HERMES_HOME (same filesystem
         # issue addressed for state.db/kanban.db — see
@@ -361,6 +364,31 @@ def __init__(self, max_size: int = MAX_STORED_RESPONSES, db_path: str = None):
             )"""
         )
         self._conn.commit()
+        # response_store.db contains conversation history (tool payloads,
+        # prompts, results). Tighten to owner-only after creation so other
+        # local users on a shared box can't read it. Run once at __init__
+        # rather than after every commit — chmod-on-every-write is wasted
+        # syscalls on a hot path.
+        self._tighten_file_permissions()
+
+    def _tighten_file_permissions(self) -> None:
+        """Force owner-only permissions on the DB and SQLite sidecars."""
+        if not self._db_path:
+            return
+        for candidate in (
+            Path(self._db_path),
+            Path(f"{self._db_path}-wal"),
+            Path(f"{self._db_path}-shm"),
+        ):
+            try:
+                if candidate.exists():
+                    candidate.chmod(0o600)
+            except OSError:
+                logger.debug(
+                    "Failed to restrict response store permissions for %s",
+                    candidate,
+                    exc_info=True,
+                )
 
     def get(self, response_id: str) -> Optional[Dict[str, Any]]:
         """Retrieve a stored response by ID (updates access time for LRU)."""

hermes_cli/webhook.py

@@ -11,8 +11,10 @@
 """
 
 import json
+import os
 import re
 import secrets
+import tempfile
 import time
 from pathlib import Path
 from typing import Dict
@@ -23,6 +25,7 @@
 
 
 _SUBSCRIPTIONS_FILENAME = "webhook_subscriptions.json"
+_SUBSCRIPTIONS_FILE_MODE = 0o600
 
 
 def _hermes_home() -> Path:
@@ -48,12 +51,33 @@ def _load_subscriptions() -> Dict[str, dict]:
 def _save_subscriptions(subs: Dict[str, dict]) -> None:
     path = _subscriptions_path()
     path.parent.mkdir(parents=True, exist_ok=True)
-    tmp_path = path.with_suffix(".tmp")
-    tmp_path.write_text(
-        json.dumps(subs, indent=2, ensure_ascii=False),
-        encoding="utf-8",
+    # webhook_subscriptions.json contains per-route HMAC secrets — write
+    # via tempfile + chmod 0o600 before the atomic rename so a permissive
+    # umask cannot leave the secrets readable to other local users in the
+    # window between create and rename.
+    fd, tmp_name = tempfile.mkstemp(
+        prefix=f".{path.name}.",
+        suffix=".tmp",
+        dir=path.parent,
+        text=True,
     )
-    atomic_replace(tmp_path, path)
+    tmp_path = Path(tmp_name)
+    try:
+        with os.fdopen(fd, "w", encoding="utf-8") as fh:
+            json.dump(subs, fh, indent=2, ensure_ascii=False)
+            fh.flush()
+            os.fsync(fh.fileno())
+        os.chmod(tmp_path, _SUBSCRIPTIONS_FILE_MODE)
+        atomic_replace(tmp_path, path)
+        # Re-assert after rename in case the destination existed with a
+        # broader mode and atomic_replace preserved it.
+        os.chmod(path, _SUBSCRIPTIONS_FILE_MODE)
+    except Exception:
+        try:
+            tmp_path.unlink(missing_ok=True)
+        except OSError:
+            pass
+        raise
 
 
 def _get_webhook_config() -> dict:

tests/gateway/test_api_server.py

@@ -14,6 +14,8 @@
 
 import asyncio
 import json
+import os
+import stat
 import time
 import uuid
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -128,6 +130,37 @@ def test_eviction_clears_conversation_mapping(self):
         # resp_2 mapping should still be intact
         assert store.get_conversation("chat-b") == "resp_2"
 
+    @pytest.mark.skipif(os.name == "nt", reason="POSIX mode bits are platform-specific")
+    def test_file_store_created_owner_only_under_permissive_umask(self, tmp_path):
+        """response_store.db must be 0o600 on creation even under umask 022."""
+        db_path = tmp_path / "response_store.db"
+        store = None
+        old_umask = os.umask(0o022)
+        try:
+            store = ResponseStore(max_size=10, db_path=str(db_path))
+            store.put(
+                "resp_secret",
+                {
+                    "response": {"id": "resp_secret"},
+                    "conversation_history": [{"role": "tool", "content": "dummy-marker"}],
+                },
+            )
+        finally:
+            os.umask(old_umask)
+            if store is not None:
+                store.close()
+
+        assert stat.S_IMODE(db_path.stat().st_mode) == 0o600
+        # WAL/SHM sidecars are owner-only too when present. WAL mode may be
+        # unavailable on some filesystems (NFS/SMB) — only assert when the
+        # sidecar files actually exist.
+        for sidecar in (
+            db_path.with_name(db_path.name + "-wal"),
+            db_path.with_name(db_path.name + "-shm"),
+        ):
+            if sidecar.exists():
+                assert stat.S_IMODE(sidecar.stat().st_mode) == 0o600
+
 
 # ---------------------------------------------------------------------------
 # _IdempotencyCache

tests/hermes_cli/test_webhook_cli.py

@@ -3,6 +3,7 @@
 import json
 import os
 import pytest
+import stat
 from argparse import Namespace
 from pathlib import Path
 
@@ -145,6 +146,31 @@ def test_corrupted_file(self):
         path.write_text("broken{{{")
         assert _load_subscriptions() == {}
 
+    @pytest.mark.skipif(os.name == "nt", reason="POSIX mode bits are platform-specific")
+    def test_save_creates_secret_file_owner_only_under_permissive_umask(self):
+        old_umask = os.umask(0o022)
+        try:
+            _save_subscriptions({"demo": {"secret": "TOPSECRET", "prompt": "x"}})
+        finally:
+            os.umask(old_umask)
+
+        path = _subscriptions_path()
+        assert stat.S_IMODE(path.stat().st_mode) == 0o600
+        assert "TOPSECRET" in path.read_text(encoding="utf-8")
+
+    @pytest.mark.skipif(os.name == "nt", reason="POSIX mode bits are platform-specific")
+    def test_save_narrows_existing_broad_secret_file_mode(self):
+        # Simulate a pre-existing 0o644 file from before this hardening landed.
+        path = _subscriptions_path()
+        path.parent.mkdir(parents=True, exist_ok=True)
+        path.write_text(json.dumps({"old": {"secret": "stale", "prompt": "x"}}))
+        path.chmod(0o644)
+
+        _save_subscriptions({"demo": {"secret": "FRESH", "prompt": "x"}})
+
+        assert stat.S_IMODE(path.stat().st_mode) == 0o600
+        assert "FRESH" in path.read_text(encoding="utf-8")
+
 
 class TestWebhookEnabledGate:
     def test_blocks_when_disabled(self, capsys, monkeypatch):