Among Us Wireshark Dissector

This repo contains a Wireshark Lua plugin to tag and analyze packets running on the Among Us UDP ports. It registers a new protocol and parses all packets. Currently, a lot of the protocol is fully analyzed. One caveat to this dissector is that it is stateless: if a field requires context from a previous packet, only the representation of the field as it appears in the packet will be shown (so numerical ID instead of resolving to a player name). However, this also means that the dissector will never be in a unknown bad state and give wrong info.

Installation

Install the lua plugin by cloning this repo and dropping the among_us_dissector.lua in your device specific plugin folder

Read this: https://www.wireshark.org/docs/wsug_html_chunked/ChPluginFolders.html
Windows: %APPDATA%\Wireshark\plugins
macOS: %APPDIR%/Contents/PlugIns/wireshark if installed as an application bundle, or INSTALLDIR/lib/wireshark/plugins if installed seperately
Linux/Unix-like OSes: ~/.local/lib/wireshark/plugins

Basic Usage

First, open up wireshark on the interface that the client is sending through (localhost if running a local server)
Filter output by protocol amongus in the filter bar
View packet dissection in the tree

Filter examples

View Among Us protocol UDP packets only: amongus
View only Among Us reliable packets: amongus and amongus.packet_format eq Reliable or amongus and amongus.packet_format eq 1
Remove Pings and ACKs from the view: amongus and !(amongus.packet_format eq Ping or amongus.packet_format eq Acknowledgement)
View only GameData payload packets (reliable and unreliable packets): amongus and amongus.payload_type eq GameData

The valid names/numbers for amongus.packet_format and amongus.payload_type and amongus.game_data are:

 Packet_Format = {
     Unreliable = 0,
     Reliable = 1,
     Hello = 8,
     Disconnect = 9,
     Acknowledgement = 10,
     Ping = 12,
 }
 
 Payload_Type = {
     CreateGame = 0,
     JoinGame = 1,
     StartGame = 2,
     RemoveGame = 3,
     RemovePlayer = 4,
     GameData = 5,
     GameDataTo = 6,
     JoinedGame = 7,
     EndGame = 8,
     GetGameList1 = 9,
     AlterGame = 10,
     KickPlayer = 11,
     WaitForHost = 12,
     Redirect = 13,
     RedirectMasterServer = 14,
     GetGameList2 = 16
 }
Game_Data_Part_Type = {
    Data = 1,
    RPC = 2,
    Spawn = 4,
    Despawn = 5,
    SceneChange = 6,
    Ready = 7,
    ChangeSettings = 8
}

Contributions and Issues

Contributions are welcome, just open a pull request to the dev branch.

Please open an issue on the Github tracker if you have a packet that doesn't get dissected (or gets dissected incorrectly)

Worked On:

Fields for protocol. Packet Format (Reliable, Hello, etc) and Payload Type (JoinGame, GameData, etc)

To Do:

Add more fields to allow easy filtering
Document fields once created
Better code style (Use tables to index and retreive parsing functions for each packet format type)
Might be converted to a C plugin if I can get compilation working properly

Credits

Thank you to the Among Us Protocol Wiki and everyone in the Impostor discord