https://anthr4ce.github.io/tags/nullcon-goa-hackim-2025/Recent content in Nullcon-Goa-Hackim-2025 on Anthrace | CTF WriteupsHugoen-usMon, 10 Feb 2025 00:00:00 +0000https://anthr4ce.github.io/ctf-writeups/nullcon-goa-hackim-2025/web/crahp/Mon, 10 Feb 2025 00:00:00 +0000https://anthr4ce.github.io/ctf-writeups/nullcon-goa-hackim-2025/web/crahp/<hr> <h1 id="web-challenge---crc-hash-collision-exploit"> Web Challenge - CRC Hash Collision Exploit <a class="heading-link" href="#web-challenge---crc-hash-collision-exploit"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h1> <hr> <h2 id="challenge-description"> Challenge Description <a class="heading-link" href="#challenge-description"> <i class="fa-solid fa-link" aria-hidden="true" title="Link to heading"></i> <span class="sr-only">Link to heading</span> </a> </h2> <p>In this challenge, we are provided with the source code of a PHP script along with two hints:</p> <ul> <li><strong>Hint 1</strong>: <a href="https://www.php.net/manual/en/function.crc32.php#28012" class="external-link" target="_blank" rel="noopener">PHP documentation link for crc32()</a></li> <li><strong>Hint 2</strong>: <a href="https://stackoverflow.com/questions/507041/crc8-check-in-php/73305496#73305496" class="external-link" target="_blank" rel="noopener">A PHP CRC8 implementation</a></li> </ul> <p>The goal is to retrieve the <strong>flag</strong> by bypassing an authentication mechanism based on <strong>CRC hashes</strong>.</p>