Understanding the challenge

We can download the files for the challenge using wget [file link].

Let’s then use unzip [file] to unzip the zip file.

We are given a zip file with 3 folders and a .sh (shell script) file.

Navigating to the file using cd [folder]/, we can then read the file using cat [file] so that we may begin understanding how this file works.

We see that the program first chooses a random number between 1 and 1000,

 target=$(( (RANDOM % 1000) + 1 ))

it then reads the inputted guess, and if the guess is valid (only contains numbers between 0 and 9),

if ! [[ "$guess" =~ ^[0-9]+$ ]]; then

checks if the guess is higher or lower than the target number. It then prints a corresponding message to keep the player’s guesses on the right track.

if (( guess < target )); then
                    echo "Higher! Try again."
                elif (( guess > target )); then
                    echo "Lower! Try again."

Understanding this, let’s attempt the challenge.

Method

We use the ssh command to connect to the provided port and address, inputting the provided password when prompted.

We can then begin guessing the number.

Upon guessing the right number, we get the flag.