Someone who doesn’t care about bandwidth usage decided to package both the server and client binaries in a single file… The server of course is meant to run on linux, and the client on Windows.
We get a PowerShell file
eulers_license.ps1 that contains:
binary_linuxvar containing the server code encoded in base64.
binary_winvar containing the client code also encoded in base64.
The linux binary
The linux binary is very easy to reverse. In fact by decoding it we get a python server which has a huge SQLi vuln:
lice = request.args.get("license_key")
query = "SELECT * FROM license_keys WHERE license_key = '" + lice + "';"
we can proceed with a basic SQLi like
' OR 1=1 -- and get the first part of the flag (which is the second one really):
The windows binary
The windows exe is a little bit harder to reverse. By looking at it with ghidra we understand that it must be:
- a 10 digits number
- a prime number
- it has something to do with Euler
By a combination of chance and testing we come across the number
2147483647 which is a prime number discovered by Euler.
Providing this input to the client gives us the output:
Enter eulers license key: 2147483647
Failed to contact euler.dragonsec.si for license confirmation...