How to use sprite mask with trail renderer?

In the end, I use a second camera with a render texture to achieve this. First, create a camera and a raw image with the same size as my material, then output the camera view to the raw image through a render texture (I do this through code at runtime). Also, remember to set the culling mask of the camera to the trail renderer's layer.

Some example code:

 private void Start()
     {
         renderTex = new RenderTexture(size.x, size.y, 0);
         renderTex.Create();
         camera = new GameObject("Window Camera", typeof(Camera)).GetComponent<Camera>(); // I create a new game object with a camera rather than add it to the current object because I need to set the camera's pos to (0, 0, -10).
         camera.transform.parent = transform;
         camera.transform.localPosition = new Vector3(0, 0, -10); // Offset the z coord so that the camera can see stuff
         // Set the camera to be 2d
         camera.orthographic = true;
         camera.orthographicSize = transform.localScale.x / 2;
         camera.cullingMask = LayerMask.GetMask("Your Layer Here");
         camera.forceIntoRenderTexture = true; // I don't really know if I need this line, but didn't test it yet.
         camera.targetTexture = renderTex;
         image = GetComponentInChildren<RawImage>();
         image.texture = renderTex;
         image.canvas.worldCamera = camera;
     }