bash_loop.md

Bash Loop

---

Question

We found a program that is hiding a flag but requires you to guess the number it is thinking of. Chances are Linux has an easy way to try all the numb$

HINTS

Either use SSH or use the Web Shell to get onto the shell server and navigate to the correct directory. Then do a quick Google search on 'bash loops'.$

---

Solution

1. First i nagivate to the directory:- /problems/77ad2ec283d51f7b1ddc449ffe109e0b

   cd /problems/77ad2ec283d51f7b1ddc449ffe109e0b in the terminal.

2. Then i saw two files was their

   cd /problems/77ad2ec283d51f7b1ddc449ffe109e0b in the terminal.

   A> BashLoop (Binary file) 
   B> Flag (But we don't had permisson to open the flag file directely.

3. Then i tried to execute that Binary file And it says

   $./Bashloop
   "What number am I thinking of? It is between 0 and 4096"

4. So if we do

   ./Bashloop 3

   Then it says

   $ ./bashloop 1337
   Nope. Pick another number between 0 and 4096
   
   ```text
   
   

5. So now read the hint It says:-

   Then do a quick Google search on 'bash loops'. You may need to use grep to filter out the responses as well!
   

So now we can use FOR loop link https://ryanstutorials.net/bash-scripting-tutorial/bash-loops.php Read about for loop their, Now lets make for last payload we can use any number from 0 to 4096 then

for spirit in {0..4096};do /problems/77ad2ec283d51f7b1ddc449ffe109e0b/bashloop $spirit |grep -v "Nope. Pick another number between 0 and 4096"; done

and we got the flag

$ for spirit in {0..4096}; do /problems/77ad2ec283d51f7b1ddc449ffe1
09e0b/bashloop $spirit |grep -v "Nope. Pick another number bet
ween 0 and 4096"; done

Yay! That's the number! Here be the flag: 9963698b982d491536db
b9cec73a417e

Thanks :)

@spiritedwolf