fix(V-009): reject path traversal in SessionEntry.from_dict and harden _ensure_loaded

Addresses PR #9560 review comments: applies the CWE-22 fix to current main
(post-PR #458 rebase) and adds the requested regression tests.

- SessionEntry.from_dict now raises ValueError for session_key or session_id
  containing '..' or starting with '/' or '\' (directory traversal guard)
- SessionStore._ensure_loaded moves per-entry validation inside the loop so
  one malicious/corrupt entry is skipped with a warning instead of aborting
  the entire sessions.json load
- Adds TestSessionEntryFromDictTraversalValidation (5 cases) and
  TestEnsureLoadedSkipsInvalidEntries covering the skip-not-abort behavior

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gateway/session.py

@@ -576,7 +576,7 @@ class SessionEntry:
         session_key = data["session_key"]
         session_id = data["session_id"]
 
-        # Validate path-sensitive fields to prevent directory traversal attacks
+        # Validate path-sensitive fields to prevent directory traversal (CWE-22)
         for _field, _val in (("session_key", session_key), ("session_id", session_id)):
             if _val and (".." in str(_val) or str(_val).startswith(("/", "\\"))):
                 raise ValueError(
@@ -786,12 +786,11 @@ class SessionStore:
             try:
                 with open(sessions_file, "r", encoding="utf-8") as f:
                     data = json.load(f)
-                    for key, entry_data in data.items():
-                        try:
-                            self._entries[key] = SessionEntry.from_dict(entry_data)
-                        except (ValueError, KeyError):
-                            # Skip entries with unknown/removed platform values
-                            continue
+                for key, entry_data in data.items():
+                    try:
+                        self._entries[key] = SessionEntry.from_dict(entry_data)
+                    except (ValueError, KeyError) as e:
+                        print(f"[gateway] Warning: Skipping invalid session entry {key!r}: {e}")
             except Exception as e:
                 print(f"[gateway] Warning: Failed to load sessions: {e}")
 

tests/gateway/test_session.py

@@ -1046,6 +1046,78 @@ class TestWhatsAppIdentifierPublicHelpers:
         assert canonical_whatsapp_identifier("") == ""
 
 
+class TestSessionEntryFromDictTraversalValidation:
+    """Regression: from_dict must reject traversal sequences in session_key/session_id."""
+
+    BASE = {
+        "session_key": "agent:main:local:dm",
+        "session_id": "abc123",
+        "created_at": "2026-01-01T00:00:00",
+        "updated_at": "2026-01-01T00:00:00",
+    }
+
+    def _entry(self, **overrides):
+        from gateway.session import SessionEntry
+        return {**self.BASE, **overrides}
+
+    def test_valid_entry_loads(self):
+        from gateway.session import SessionEntry
+        entry = SessionEntry.from_dict(self._entry())
+        assert entry.session_id == "abc123"
+
+    def test_session_id_dotdot_raises(self):
+        from gateway.session import SessionEntry
+        with pytest.raises(ValueError, match="session_id"):
+            SessionEntry.from_dict(self._entry(session_id="../../etc/passwd"))
+
+    def test_session_key_dotdot_raises(self):
+        from gateway.session import SessionEntry
+        with pytest.raises(ValueError, match="session_key"):
+            SessionEntry.from_dict(self._entry(session_key="agent:main:../../secret"))
+
+    def test_session_id_absolute_unix_raises(self):
+        from gateway.session import SessionEntry
+        with pytest.raises(ValueError, match="session_id"):
+            SessionEntry.from_dict(self._entry(session_id="/etc/passwd"))
+
+    def test_session_id_absolute_windows_raises(self):
+        from gateway.session import SessionEntry
+        with pytest.raises(ValueError, match="session_id"):
+            SessionEntry.from_dict(self._entry(session_id="\\windows\\system32\\config"))
+
+
+class TestEnsureLoadedSkipsInvalidEntries:
+    """Regression: one bad sessions.json entry must not block valid entries from loading."""
+
+    def test_invalid_entry_skipped_valid_entry_loads(self, tmp_path):
+        import json
+        from gateway.session import SessionStore
+        from gateway.config import GatewayConfig
+
+        sessions_file = tmp_path / "sessions.json"
+        sessions_file.write_text(json.dumps({
+            "bad:key": {
+                "session_key": "bad:key",
+                "session_id": "../../evil",
+                "created_at": "2026-01-01T00:00:00",
+                "updated_at": "2026-01-01T00:00:00",
+            },
+            "agent:main:local:dm": {
+                "session_key": "agent:main:local:dm",
+                "session_id": "good123",
+                "created_at": "2026-01-01T00:00:00",
+                "updated_at": "2026-01-01T00:00:00",
+            },
+        }), encoding="utf-8")
+
+        store = SessionStore(sessions_dir=tmp_path, config=GatewayConfig())
+        store._ensure_loaded()
+
+        assert "bad:key" not in store._entries
+        assert "agent:main:local:dm" in store._entries
+        assert store._entries["agent:main:local:dm"].session_id == "good123"
+
+
 class TestSessionStoreEntriesAttribute:
     """Regression: /reset must access _entries, not _sessions."""