Episodes
mihaic195 said almost 2 years ago on Active Storage Uploads Behind a CDN :
  with Variants, the link looks like this:  
variants/rsoao6al0qs6i7ufbzm5x2nw4hr1/cabe6e2a3218e12456787572cfb5ee71459383cdd72e19a0f5bacea3b3987208
which yields a 403 from Cloudfront. 
I have the image_processing gem installed.