How to whitelist images with nginx after 30 days?

Question

Nginx

Images are uploaded via ftp. They are rendered via nginx.

How to create a rule: if a picture is older than 30 days, then only the white list of ip addresses can view it?

That is, nginx must see its lifetime before giving the picture. I found that I can sort of solve it through expires modified 30d, but I don’t know how to proceed.