VIAaaS/README.md at 03a83dd6dad178be368a7b79aa756be07e4d2b0b

ViaVersion, ViaBackwards and ViaRewind translates the connections to backend server.
VIAaaS auth page stores account credentials in the player's browser local storage.
It requires a CORS Proxy for calling Mojang APIs.
Account credentials aren't sent to VIAaaS instance, though it's proxied by CORS Proxy.
The web page receives and validates the joinGame's session hash from VIAaaS instance.

Setting up server instance

Download: GitHub Actions (needs to be logged into GitHub) or JitPack

How to download and start VIAaaS server:

curl -Lf --output VIAaaS-all.jar "https://jitpack.io/com/github/ViaVersion/VIAaaS/master-SNAPSHOT/VIAaaS-master-SNAPSHOT-all.jar"
java -jar VIAaaS-all.jar

Requires Java 11
Default Minecraft: via.localhost with port 25565
Default HTTPS: https://localhost:25543/
Default WS URL: wss://localhost:25543/ws

How to create a public server

You need a DNS wildcard pointing to VIAaaS instance, like *.example.com -> 192.168.123.123. You can use DuckDNS DDNS service.
Configure the hostname in the config
Open the Minecraft port (25565)
The HTTPS page needs a valid SSL certificate, you can use Apache (with a Let's Encrypt certificate) as a reverse proxy. See apache_copypasta.txt file.

CORS Proxy

Due to Mojang API not allowing CORS request, we need to use a CORS proxy
For less chance of Mojang seeing the login as suspect, you (the player) should set up a CORS proxy on your machine.
Note the ending slash in cors-anywhere address
The default CORS Proxy is hosted at https://crp123-cors.herokuapp.com/ (source)

Usage for players

You can also connect to ```via.localhost`` and set the address parameters via web page.

Offline mode:

Connect to mc.example.net.via.localhost

Online mode:

Web login:

Go to VIAaaS auth webpage (default is https://localhost:25543/)
Listen to the username A (you'll use it to connect to the VIAaaS instance).
Add the account B (you'll use it in backend server).
Keep the page open
Connect with your account A to mc.example.com._u(account B).via.localhost
Approve the login in the webpage

Web login via token caching:

Open the web page and save your account in your browser
Send your access token to the instance
Connect with mc.example.com.via.localhost

Fabric/Forge client:

Install OpenAuthMod in your client.
Join the server: mc.example.net.via.localhost
Approve the login

Address options

Example address:

server.example.net._p25565._v1_12_2._of._uBACKUSERNAME.via.example.com
server.example.net.v_1_8.via.example.com
It's inspired by Tor2web proxies.

Address parts:

You can use (option)_(value) too, like p_25565.
server.example.net: backend server address
_p: backend port
_v: backend version (protocol id or name, replace . with _) . AUTO is default (with 1.8 as fallback).
_o: true to force online mode in frontend, false to force offline mode in frontend. If not set, it will be based on backend online mode.
_u: username to use in backend connection (default is front-end username)
via.example.com: instance address (defined in config)

WARNING

VIAaaS may trigger anti-cheats, due to block, item, movement and other differences between versions. USE AT OWN RISK.
Take care of browser local storage. Check for XSS vulnerabilities on your domain.
Check the security of CORS proxy, it will be used for calling to Mojang API.
Mojang may lock your account when API is called from a suspect IP address.

FAQ

Accounts

Why to use an online webpage for online mode?:

It's easier to maintain in that way, because providing login via chat requires encoding and decoding more packets, which reduces maintainability.
It allows your account password and token to be kept with you.

How to use Microsoft Account?:

If you are using a public VIAaaS instance, use this page https://viaversion.github.io/VIAaaS/ and configure the WebSocket address.
If you're an administrator of the instance, edit config/web/js/config.js (default is in the jar) and configure your Azure Client ID and your domain whitelist.

Connection

How to use IPv6?:

When listening to 0.0.0.0, it should listen on IPv6 too.
The hostname parser currently doesn't support direct IPv6, but you can use a DNS name with https://sslip.io/

I'm getting a DNS error/"Unknown host" while connecting to via.localhost

Try configuring via.localho.st as hostname suffix instead

How to use with Geyser?

Set the parameters in Geyser's address field:

remote:
  # The IP address of the remote (Java Edition) server
  address: 2b2t.org._v1_12_2.via.localhost

If you are using a public GeyserConnect instance: connect to a publicly available VIAaaS instance, like mc.example.com._v1_8.via.example.net as a Java Edition server.

Can I use it to connect to .onion Minecraft hidden servers?

You can use .onion addresses if the instance is proxying the backend connections to TOR. Note that VIAaaS may log your requests, and that your DNS queries may be unencrypted.

Can you support more versions / Is there some alternative?

See DirtMultiVersion and RK_01's ViaProxy server ( viaproxy.raphimc.net)

Can I customize the files of HTTP server?

Add files to config/web/ directory

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VIAaaS

Demo

How does it work?