HackTheBox Challenge Low Logic (Hardware)

Challenge Synopsis

I have this simple chip, I want you to understand how it’s works and then give me the output. (Source)

Enumeration

In this challenge, we are given 2 files - chip.jpg and input.csv.

❯ head input.csv
in0,in1,in2,in3
1,0,0,1
1,1,0,0
0,1,1,0
0,0,1,0
1,1,0,1
1,0,0,1
0,0,0,0
0,0,1,0
0,0,0,0

Analysing the diagram in chip.jpg, we can observe that there are 2 AND Gates and 1 OR Gate.

Exploitation

We can craft our script to take in the values from input.csv and find out the outputs using the logical gates.

❯ cat solve.py
#!/usr/bin/python3

import csv

def solve(input_file):

  results = []
  
  with open(input_file, mode='r') as csvfile:
    csvreader = csv.reader(csvfile, delimiter=',')
    next(csvreader) # start from second row

    # Read inputs from input.csv
    for row in csvreader:
        input1 = int(row[0])
        input2 = int(row[1])
        input3 = int(row[2])
        input4 = int(row[3])

        and_output1 = input1 & input2
        and_output2 = input3 & input4

        final_output = and_output1 | and_output2

        results.append(str(final_output))
    
    return ''.join(results)

input_file = 'input.csv'

output = solve(input_file)
print(output)

❯ ./solve.py
010010000101010001000010011110110011010001011111010001110011000000110000011001000101111101000011011011010011000000110101010111110011001101111000001101000110110101110000011011000011001101111101

Take the binary output and convert it to ASCII in CyberChef.

Flag: HTB{4_G00d_Cm05_3x4mpl3}