We are going to create a local domain like app.local, Create a self-signed wildcard certificate which will works for subdomains as well and point the domain to a locally running site.

Generate a self signed certificate

https://www.brainbytez.nl/tutorials/linux-tutorials/create-a-self-signed-wildcard-ssl-certificate-openssl/

1. Create the CA Private Key

    openssl genrsa -out MyPrivate.key 2048
   

2. Generate the CA Root certificate

    openssl req -x509 -new -nodes -key CAPrivate.key -sha256 -days 365 -out CAPrivate.pem
   

3. Create a Private Key

    openssl genrsa -out MyPrivate.key 2048
   

4. Generate the CSR

    openssl req -new -key MyPrivate.key -extensions v3_ca -out MyRequest.csr
   

5. Create extensions file to specify subjectAltName

   Create an extensions file named: openssl.ss.cnf

    basicConstraints=CA:FALSE
    subjectAltName=DNS:*.mydomain.tld
    extendedKeyUsage=serverAuth
   

   Replace "mydomain.tld" with your own domain like app.local.

6. Generate the Certificate using the CSR

    openssl x509 -req -in MyRequest.csr -CA CAPrivate.pem -CAkey CAPrivate.key -CAcreateserial -extfile openssl.ss.cnf -out MyCert.crt -days 365 -sha256
   

Install and configure Nginx ProxyManager

Follow this up to date guide to install and setup Nginx Proxy Manager

Configure SSL certificate in Nginx

1. Go to SSL Certificates tab in Nginx Proxy Manager Dashboard

   

2. Click "Add SSL Certificate"

   

3. Choose "Custom"

   

4. Choose "MyPrivate.key" as Certificate Key and "MyCert.crt" as Certificate which were generated during certificate generation step [1] and save it.

   

Add a Proxy Host

1. Click on Dashboard and Go to Proxy Hosts

   

2. Click on Add Proxy Host

   

3. Enter the details

   

   1. Domain names: Your domain name and subdomains

   2. Forward IP: Local Network IP address of your machine in local network. Note: 127.0.0.1 or localhost will not work here and cause 502 error later on. So use the local network address assigned by your router.

   3. Port: The port address in which your service is running.

   4. Go to SSL tab and choose the previously uploaded SSL Certificate and click Save.

4. Notes:

   1. If your subdomain should point to multiple servers running on different ports, then create separate proxy host entry for each domain or subdomain. If your application handles the domain and subdomain routing then include all domains as well as subdomains in the same entry.

   2. If your application does not serve in the host mode by default, make sure your application is running in host mode. Otherwise your application will not be accessible in local network. Different framework have different commands to serve in host mode. Common command is to include `--host` in the serve command.

Configure /etc.hosts

1. Open a hosts file with sudo

    sudo nano /etc/hosts
   

2. Add your required entries like this. Any domain or subdomain should point to 127.0.0.1

   

That's it. Now when you visit your domain from the same machine, you should be able to visit your services and applications. Make sure your application or server is running and serving in host mode and configured port address.