VIAaaS

VIAaaS - ViaVersion acetylsalicylic acid as a Service - Standalone ViaVersion proxy

Public instances: https://github.com/ViaVersion/VIAaaS/wiki/List-of-Public-Instances

Discord: https://viaversion.com/discord

How does it work?

• ViaVersion, ViaBackwards and ViaRewind translates the connections to backend server.
• VIAaaS auth page stores account credentials in the player's browser local storage. Check for XSS vulnerabilities on your domain.
• Due to technical/security reasons, it requires a CORS Proxy for calling Mojang APIs, which may make Mojang see that as suspicious and reset/block your account password if the IP address seems suspect.
• Account credentials aren't sent to VIAaaS instance, though it's intermediated by CORS Proxy.
• VIAaaS receives a session hash from instance and then authenticates the session hash with Mojang.

Setting up server instance

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

How to start VIAaaS server:

java -jar VIAaaS-all.jar

• Requires Java 11
• Default Minecraft: viaaas.localhost with port 25565
• Default WS URL: wss://localhost:25543/ws

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

Setting up cors-anywhere on local machine:

git clone https://github.com/Rob--W/cors-anywhere
cd cors-anywhere
npm install
node server.js

• It will be available at http://localhost:8080/

My cors-anywhere instance:

• If you trust me, you can use https://crp123-cors.herokuapp.com/ (source)

Usage for players

Usage for offline mode:

• Connect to mc.example.com.viaaas.localhost

Usage for online mode:

• You can use two accounts (avoids Bad Login error), the same account for front-end and back-end connections, or use _of (offline mode in frontend, unencrypted and with no username verification).
• Go to VIAaaS auth webpage
• Configure CORS proxy, see above in "CORS Proxy" section
• Listen to the username A you'll use to connect to the proxy.
• Add the account B to VIAaaS page which you'll use in _u(account B) parameter below.
• Connect to mc.example.com._u(account B).viaaas.localhost (_u parameter can be removed if you are using the same username)
• Approve the login in auth webpage
• If you use the same online mode account, your client may show Bad Login. You can use a mod like Auth Me or ReAuth for reauthenticating the client.

Example address: server.example.com._p25565._v1_12_2._of._uBACKUSERNAME.viaaas.example.com (similar to Tor2web proxies)

Address parts:

• server.example.com: backend server address
• _p: backend port
• _v: backend version (protocol id or name with underline instead of dots). AUTO is default and 1.8 is fallback if it fails.
• _o: t to force online mode in frontend, f to disable online mode in frontend. If not set, it will be based on backend online mode.
• _u: username to use in backend connection
• viaaas.example.com: hostname suffix (defined in config)

WARNING

• VIAaaS may trigger anti-cheats, due to block, item, movement and other differences between versions. USE AT OWN RISK
• VIAaaS server instance may have security vulnerabilities, make sure to block the ports in firewall
• Take care of browser local storage. Check for XSS vulnerabilities on your domain.
• Check the security of CORS proxy, it will intermediate Mojang API calls.
• Mojang may lock your account when API is called from a suspect IP address

FAQ

VIAaaS is stuck when connecting with online mode:

• Your system may have low entropy, see https://wiki.archlinux.org/index.php/Rng-tools

My Microsoft account <18 years old is not able to log in, it's giving XSTS error:

• Add your account to a family (see https://wiki.vg/Microsoft_Authentication_Scheme#Authenticate_with_XSTS)

Why a online webpage for online mode?:

• It's easier to maintain in that way, because providing a chat with login requires encoding and decoding more packets which change through versions.
• It allows your account password and token to be kept with you

How to use IPv6?:

• When listening to 0.0.0.0, it should listen on IPv6 too.
• To use IPv6 in backend address, you need to use a instance with IPv6 connectivity. The hostname parser currently doesn't support direct IPv6, but you can use a DNS name.

How to use with Geyser?

• Currently you need to set the parameters (at least the hostname) in Geyser's address field:

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

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

How to connect to 1.7.10 and lower servers with a newer client?

• Use DirtMultiVersion