Unable to use valid_referers if server_name is set by a env. variable

[venomone]

Hello,

im currently facing an issue, imagin the following nginx.conf:

env NGINX_SERVERNAMES;
...
server {
        set_by_lua $curr_server_name 'return os.getenv("NGINX_SERVERNAMES")';
        server_name $curr_server_name;
        valid_referers none blocked server_names;

i would expect that "server_names" is using server_name which i again load by a env. variable "env NGINX_SERVERNAMES;"
but for some reason NGINX openresty/nginx returns the following error at the log:

2020/02/05 12:23:59 [emerg] 151#151: conflicting parameter "$curr_server_name" in /etc/nginx/nginx.conf:185

So how can i use valid_referers together with my server_name variable on openresty?

I also tryd the following:

valid_referers none blocked server_names $curr_server_name;
valid_referers none blocked $curr_server_name;

Which is also not working as expected.

[agentzh]

@venomone It seems that you're having a directive running order issue. Do you know that set_by_lua always runs after server_name even if you put the former before the latter in the nginx.conf file?

[venomone]

@agentzh no i was not aware f it. im using openresty now since a week or so and im still thinking the NGINX way here i guess. So is there any solution for this problem?

[agentzh]

@venomone Easy. For your purposes, you can just do the “Referer” request header check all in Lua, like, say, in rewrite_by_lua_block.

[venomone]

Do you maybe have a full example here, maybe a copy-paste example from you config or so. currently you have to derive everything yourself. Would be awesome, thank you.

[agentzh]

@venomone You can use the ngx.var API to fetch the Referer request header and then check it against the dynamic value you set. It should be trivial enough. Consult the ngx_lua manual for more details about these API functions and directives. I don't have the time to prepare example code for every open source user. Sorry. You may also ask in the openresty-en mailing list for further assistant for example. This place is for bug report only.