In this reverse challenge we were given a ELF (look at generic_crackme_redux):

So the first thing to do is to open it in ghidra and understand the business logic:

This is the main function:


We are asked to input a string, then is called a check function on the input, the core of the check is:


So the flag is:
```
flag{70517}
```

Original writeup (https://github.com/pwnsticciotti/writeups/tree/master/redpwnCTF/generic_crackme_redux).