Reverse Engineering Galaxy Communication Service - Environment Setup

Software we need:

Windows 11 VM (Can be any Windows machine or VM)
Proxifier (it’s paid but we can use 30 day trial)
Custom mitmproxy build
Official Galaxy client
Game that makes use of SDK

Everything we are going to do here will happen only in a VM, you can also try to run Galaxy in Wine, however I couldn’t find any Proxifier alternatives

Proxifier setup

Download and install Proxifier and add proxy settings as follows

Add a proxification rule to route all connections from GalaxyCommunication.exe through proxy.

Also add a rule to prevent loops

Note: Executable can be different for you depending on which Python version you have.

Mitmproxy setup

Follow the development setup steps from CONTRIBUTING.md to install mitmproxy

Now temporarly add proxification rule for your web browser in Proxifier and launch mitmproxy on port we configured. For me it’s mitmproxy -p 8080

Go to mitm.it and download .pem and .p12 certificate formats
Open C:\ProgramData\GOG.com\Galaxy\redists\rootCA.pem in the text editor
Paste .pem file contents you downloaded at the end
Save changes

Make Galaxy Communication accept your cert

As for now make sure you are using mitmproxy fork I linked earlier since that one includes CRL support, that’s not available upstream currently.

Import .p12 certificate you downloaded earlier into Trusted Root Certification Authorities