nginx dynamic server_name with variable

Question

Dear StackOverflow community I am working with a third party that does not support dynamic GET requests (eg example.com?variable=somethingDynamic) thus I resotred to using custom sub-domains, however I prefer not to make a sub domain for each and every dynamic request so I have been wondering:

how can I write server_name in a way to catch two or three dynamic variables?

here is my example server block:

server {
    listen 80;
    server_name someSecretUrl_$variable1_$variable2.example.com;
    root /usr/share/campagins/campagin1;
    client_max_body_size 10000m;
    proxy_connect_timeout 30000;
    location /funnel_webhooks/test {
        return 200;
    }
    location / {
        if ($request_method = 'OPTIONS') {
            # Tell client that this pre-flight info is valid for 20 days
            add_header 'Access-Control-Max-Age' 1728000;
            add_header 'Content-Type' 'text/plain charset=UTF-8';
            add_header 'Content-Length' 0;
            add_header 'Access-Control-Allow-Origin' "$http_origin" always;
            add_header 'Access-Control-Allow-Credentials' 'true' always;
            add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
            add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With,Etag,Last-Modified,HTTP_IF_MODIFIED_SINCE,HTTP_IF_NONE_MATCH' always;
            return 204;
        }
        add_header 'Access-Control-Allow-Origin' "$http_origin" always;
        add_header 'Access-Control-Allow-Credentials' 'true' always;
        add_header 'Access-Control-Allow-Methods' 'GET, POST, PUT, DELETE, OPTIONS' always;
        add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,DNT,If-Modified-Since,Keep-Alive,Origin,User-Agent,X-Requested-With,Etag,Last-Modified,HTTP_IF_MODIFIED_SINCE,HTTP_IF_NONE_MATCH,ETag,Retry-After' always;
        add_header 'Access-Control-Expose-Headers' 'ETag,Retry-After' always;
        add_header 'Cache-Control' "must-revalidate, post-check=0, pre-check=0" always;
        rewrite ^(.*)$ $1?preMadeDataParsers=$variable1&preMadeDataParsersOnResponse=$variable2&$args break;
        proxy_buffering off;
        proxy_pass http://localhost:3000; #proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header REMOTE_ADDR $remote_addr;
    }
}

Looking at the code above you will notice I am trying to move $variable1 into a GET variable, and $variable2 into another get variable aswell, how can I achieve such a thing? thanks!

Alex Howansky · Accepted Answer · 2018-05-08 15:56:05Z

2

I wouldn't do this in nginx, I'd do this in your application. (Especially if you expect to expand on this resource.)

I would configure the server to listen on the IP with no virtual hosts at all, so that it answers any request made to the IP. Just leave out the server_name directive:

server {
    listen 1.2.3.4:80;
    ...

Then configure your DNS with a wildcard entry so that *.example.com points to that IP. Now you can hit any_string.example.com and it will resolve to your IP, get answered by the main server block, and passed to your app.

Then, inside your app, look at what hostname was requested. (In PHP for example, this is available via $_SERVER['HTTP_HOST'].) If your app determines that the requested hostname is invalid, just issue a 404 and exit. Otherwise, decode the hostname and process the request.

This way, you can add new variables and new features without editing the nginx config. You could even encode your variables in JSON then BASE64 encode them:

$vars = [
    'var1' => 'one',
    'var2' => 'two',
    'var3' => 'three',
];
$url = base64_encode(json_encode($vars));

eyJ2YXIxIjoib25lIiwidmFyMiI6InR3byIsInZhcjMiOiJ0aHJlZSJ9.example.com

Now you can pass any number of variables, with any names, including indexed and associative arrays. (Though note there is a limit to the domain name length, and you'll have to do something about the + and / characters which I'm pretty sure aren't valid in domain names.)

answered May 8, 2018 at 15:56

Alex Howansky

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1 Comment

vasilevich Over a year ago

well, in order to avoid any complications with + and / characters you could simpley url encode/decode the whole base64 string simple as that.

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