feat: security hardening — SSRF guard, template sandbox timeout, webhook log prune, auth & backup polish

- Add outbound URL validation (SSRF) for webhook/Discord/Slack/ntfy/Matrix dispatch
- Template renderer: input/output caps and thread-based render timeout
- Webhook log filter: strip Authorization/signature/token-like headers; atomic prune
- Auth/JWT/backup/config tightening; misc frontend UX fixes

packages/server/src/notify_bridge_server/api/backup.py

@@ -31,6 +31,23 @@ def _backup_dir():
     return app_config.data_dir / "backups"
 
 
+def _resolve_backup_file(filename: str):
+    """Validate filename and resolve to a path strictly inside the backup dir."""
+    if not filename.startswith("backup-") or not filename.endswith(".json"):
+        raise HTTPException(status_code=404, detail="Backup file not found")
+    if "/" in filename or "\\" in filename or ".." in filename or "\x00" in filename:
+        raise HTTPException(status_code=404, detail="Backup file not found")
+    base = _backup_dir().resolve()
+    candidate = (base / filename).resolve()
+    try:
+        candidate.relative_to(base)
+    except ValueError:
+        raise HTTPException(status_code=404, detail="Backup file not found")
+    if not candidate.is_file():
+        raise HTTPException(status_code=404, detail="Backup file not found")
+    return candidate
+
+
 # ---------------------------------------------------------------------------
 # Export
 # ---------------------------------------------------------------------------
@@ -194,9 +211,7 @@ async def download_backup_file(
     user: User = Depends(require_admin),
 ):
     """Download a specific backup file."""
-    filepath = _backup_dir() / filename
-    if not filepath.is_file() or not filename.startswith("backup-"):
-        raise HTTPException(status_code=404, detail="Backup file not found")
+    filepath = _resolve_backup_file(filename)
 
     try:
         content = json.loads(filepath.read_text(encoding="utf-8"))
@@ -215,9 +230,6 @@ async def delete_backup_file(
     user: User = Depends(require_admin),
 ):
     """Delete a specific backup file."""
-    filepath = _backup_dir() / filename
-    if not filepath.is_file() or not filename.startswith("backup-"):
-        raise HTTPException(status_code=404, detail="Backup file not found")
-
+    filepath = _resolve_backup_file(filename)
     filepath.unlink()
     return {"deleted": filename}