Say I have a public server with a service (email, web server, etc) that’s accessible through https://myservice.example.com, and I would like to restrict that service with a VPN. How do I do that?
I know how to setup a VPN. I know how to use some of the services through that VPN. But see, if I want to use that VPN, I connect my client to that VPN, then I get the subnet of that VPN, say 10.10.100.0, through which I can access the devices by address.
But I see some services offer things like https://myservice.example.com, and they only work when that VPN is connected. How does that work? Is it just some DNS setting at the domain level or there’s more to it?
Just… stop making it accessible from the Internet? Whatever you did to allow it through your firewall, just remove that rule.
I’ve been managing servers for over 10 years, and I never have felt stupider, and I still don’t understand how to do this. Everyone is making a comment that I don’t understand.
Let’s talk internet 101, and please tell me where I’m wrong.
You make a request to https://myservice.example.com. The DNS responds to a query giving you an IP address, say 1.2.3.4. Now the client software makes another request to 1.2.3.4:433 (say if we’re attempting to access an https server, binding the SNI address to the SSL/TLS header). The request will be sent to that server, and the server will respond. In what part of all this process can the VPN can do anything?
Normally if you want to access a device through VPN, you make a request to a WHOLE other ip address in another subnet on another (virtual) device locally. It has absolutely nothing to do with 1.2.3.4. It’s something like 10.10.100.X… or similar. How will my domain, myservice.example.com, route to that address, 10.10.100.X? Is it as dumb and simple as routing there? Or is there more to it? It doesn’t sound right to make the DNS server record point to 10.10.100.X.
It is that simple. Make the dns entry point to your vpn subnet 10.10.100.X. The way it works is anyone not on your vpn won’t be able to resolve the ip address and will get an error. Anyone on the vpn will be able to resolve the ip address and connect via the vpn connection.
The part people are talking about that is likely confusing you is that if your service is already available via your actual ip address 1.2.3.4 then you have a security concern since anyone can access 1.2.3.4 even without your domain name pointing there. They are encouraging you to make sure your 1.2.3.4 network doesn’t allow access but updating your firewall settings to make sure it blocks connections that are not made via your vpn subnet of 10.10.100.X
Okay, the others are a little short for what you need.
Your VPN needs it’s own DNS. With that DNS you can route the traffic internally from the VPN subnet to the server. Then you can set the server up to only take requests from that subnet either via firewall or the reverse proxy.
100%.Or set host file entries on each endpoint to resolve the mail.domain.com to your internal ip that’s available only over vpn. Not going to be easy on mobiles.
There is an assumption though that the mail server has an internal IP address wherever you are hosting. That might not be true. I would always put the public IP on the firewall and then NAT with specific port 25 in to the private IP of the server, but who knows what this particular OP has done.
Probably they have the service configured to only listen into the interface of the VPN.
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Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I’ve seen in this thread:
Fewer Letters More Letters DNS Domain Name Service/System HTTP Hypertext Transfer Protocol, the Web IP Internet Protocol NAT Network Address Translation SSL Secure Sockets Layer, for transparent encryption TLS Transport Layer Security, supersedes SSL VPN Virtual Private Network VPS Virtual Private Server (opposed to shared hosting) nginx Popular HTTP server
8 acronyms in this thread; the most compressed thread commented on today has 19 acronyms.
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Set myservice.example.com to an internal address like 10.10.100.x. Those addresses are not routable on the public internet. They can only be reached from a local network which the VPN tunnels you into.
If your VPN also supplies DNS to clients, can also add a private zone if its supported so nobody can resolve that internal address except those clients.