Getting not found error for downloading document while logged in "PUBLIC user" in website sale. 

in my controller:

attachments = request.env['ir.attachment'].sudo().search(  [('res_id', '=', order.id)])

in my  xml

 <t t-foreach="attachments" t-as="attachment">

  <a target="_blank" t-attf-href="/web/content/#{attachment.id}?download=1" t-esc="attachment.datas_fname" class="fa fa-download"/>

I can able to download in users, but i'm getting not found err in public user