Replacing $http_referer with your own using nginx?

Question

Nginx

Greetings!
The link is generated with via secure_link_md5 "$my_header$arg_e$sec";
Where $my_header is specified by $http_referer, and if the client did not pass the referer, then the $http_x_customheader header is valid, which is passed successfully, everything works through the map

map $http_referer $my_header {
default $http_referer;
"" $http_x_customheader;
}

It is possible to transfer content through google cast, which changes the referer to its own, and so on. the link is no longer given.
in the logs

"GET .m3u8?st=lqG8gzdWj2Xo75A9MguidA&e=1600341610 HTTP/2.0" status=200 395 refer="https://domain.com/test.html" "Mozilla/5.0 (Linux; Android 10; SM-N975F) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.101 Mobile Safari/537.36"

"GET .m3u8?st=lqG8gzdWj2Xo75A9MguidA&e=1600341610 HTTP/2.0" status=403 169 refer="https://www.gstatic.com/cast/sdk/default_receiver/1.0/app.html?skin=https://www.gstatic.com/eureka/player/0000/skins/cast/skin.css" "Mozilla/5.0 (Linux; Android 5.1.1; Build/LMY48N) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.54 Safari/537.36 CrKey/1.47.216070"

Tried different ifs with no success.
Please tell me what and how to prescribe for this case?