Wildcard *.localhost SSL with Nginx and Chrome

Question

I've attempted to set up a wildcard *.localhost for HTTP and HTTPS with Nginx proxying requests to localhost:3000. DNSmasq is used for resolving *.localhost to 127.0.0.1.

Everything works fine for HTTP, but HTTPS connections receive the following error in Google Chrome:

There are issues with the site's certificate chain (net::ERR_CERT_COMMON_NAME_INVALID).

The certificate is a self-signed certificate that I've added to Chrome via settings, and was generated with the following command:

openssl req -x509 -sha256 -newkey rsa:2048 -keyout localhost.key -out localhost.crt -days 3650 -nodes

The Subject is as follows:

Subject: C=AU, ST=Western Australia, L=Perth, O=Zephon, CN=*.localhost

My Nginx config is as follows:

server {
    listen       80;
    listen       443 ssl; 

    server_name  localhost;

    ssl_certificate /etc/nginx/ssl/localhost.crt;
    ssl_certificate_key /etc/nginx/ssl/localhost.key;

    location / {
        proxy_pass          http://localhost:3000;
        proxy_http_version  1.1;
        proxy_set_header    Host             $host;
        proxy_set_header    Upgrade          $http_upgrade;
        proxy_set_header    Connection       "upgrade";
        proxy_set_header    X-Real-IP        $remote_addr;
        proxy_set_header    X-Forwarded-For  $proxy_add_x_forwarded_for;
        proxy_set_header    X-Client-Verify  SUCCESS;
        proxy_set_header    X-Client-DN      $ssl_client_s_dn;
        proxy_set_header    X-SSL-Subject    $ssl_client_s_dn;
        proxy_set_header    X-SSL-Issuer     $ssl_client_i_dn;
        proxy_read_timeout 1800;
        proxy_connect_timeout 1800;
    }
}

Answer 1

So ultimately the answer seems to be that you simply can't create a certificate for *.localhost that Chrome will accept.

My solution was to change to using *.dev.localhost instead, which worked a treat.

Answer 2

It's actually fully possible. What it's not is particularly well documented.

https://letsencrypt.org/docs/certificates-for-localhost/#making-and-trusting-your-own-certificates shows how to generate your own localhost certificate

openssl req -x509 -out localhost.crt -keyout localhost.key \
  -newkey rsa:2048 -nodes -sha256 \
  -subj '/CN=localhost' -extensions EXT -config <( \
    printf "[dn]\nCN=localhost\n[req]\ndistinguished_name = dn\n[EXT]\nsubjectAltName=DNS:localhost\nkeyUsage=digitalSignature\nextendedKeyUsage=serverAuth")

You can then work out what extras signing a wildcard certificate needs. I believe this is as simple as providing a *. prefix (glob wildcard syntax) source

Installing a self-signed cert is documented elsewhere on stackoverlow regarding linux

Windows IDK, Mac IDC