## Preview:
![](https://github.com/0xWerz/CTF-writeups/blob/main/GDG-Algiers-2022/jail/red-diamond/img/desc.png?raw=true)
## WalkthroughConnecting to the server:> nc -v jail.chal.ctf.gdgalgiers.com 1303
if we pass `"` as a input it response with a error, and we see that it handled with the eval function:
> The Eval function evaluates the string expression and returns its value. For example, Eval("1 + 1") returns 2. If you pass to the Eval function a string that contains the name of a function, the Eval function returns the return value of the function.
![](https://github.com/0xWerz/CTF-writeups/blob/main/GDG-Algiers-2022/jail/red-diamond/img/res_err.png?raw=true)
So if i try to pass the system function with a system commmand it might work fine.
![](https://github.com/0xWerz/CTF-writeups/blob/main/GDG-Algiers-2022/jail/red-diamond/img/ls.png?raw=true)
We can cat the flag by replacing `ls` with `cat flag.txt` again.  