instruo-ctf/src/banananana.html at main · gradientgeeks/instruo-ctf · GitHub

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<!DOCTYPE html>
<html lang="en">
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    <title>Banananana - Instruo CTF 2025</title>
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                    <h1 class="text-4xl font-bold text-white">Banananana 🍌</h1>
                </div>
                <div class="flex flex-wrap gap-3">
                    <span class="inline-flex items-center px-3 py-1 rounded-full text-sm font-medium bg-gray-700 text-white">Steganography</span>
                    <span class="inline-flex items-center px-3 py-1 rounded-full text-sm font-medium bg-orange-700 text-white">200 pts</span>
                    <span class="inline-flex items-center px-3 py-1 rounded-full text-sm font-medium bg-yellow-600 text-white">Medium</span>
                </div>
            </div>

            <div class="content-section">
                <h2 class="text-2xl font-bold mb-4">Challenge Information</h2>
                <ul class="space-y-2">
                    <li><strong>Challenge Name:</strong> Banananana</li>
                    <li><strong>Category:</strong> Steganography</li>
                    <li><strong>Points:</strong> 200 pts</li>
                    <li><strong>Teams Solved:</strong> 11</li>
                    <li><strong>Description:</strong> "Obama loves banana. But the peels are scattered everywhere. Can you clean this mess and reveal what's lurking beneath all this?"</li>
                    <li><strong>File:</strong> banananana.wav</li>
                    <li><strong>Flag:</strong> <code class="text-green-600">EOF{hidden_among_bananananananana}</code></li>
                </ul>
            </div>

            <div class="content-section">
                <h2 class="text-2xl font-bold mb-4">Solution Methodology</h2>

                <h3 class="text-xl font-semibold mb-3 mt-4">Step 1: Initial Thoughts</h3>
                <p class="mb-3">The word <em>banana</em> being repeated and the reference to <em>peels</em> suggested that the data might be hidden in the file's metadata or text strings rather than deep frequency analysis.</p>
                <p class="mb-3">The challenge was in the <strong>Steg</strong> category, so the first step was to extract readable text.</p>

                <h3 class="text-xl font-semibold mb-3 mt-6">Step 2: String Extraction</h3>
                <p class="mb-3">I decided to use the <code>strings</code> command — a simple yet effective tool to extract printable characters from binary files:</p>
                <pre><code class="language-bash">strings banananana.wav | grep EOF</code></pre>
                <p class="mb-3">This command looks for any lines containing the keyword <code>EOF</code>, which is often used in CTF challenges to denote hidden messages or flag formats.</p>

                <h3 class="text-xl font-semibold mb-3 mt-6">Step 3: Discovery</h3>
                <p class="mb-3">The output revealed the following lines:</p>
                <pre><code>EOF_BEC
;EOF{hidden_among_bananananananana}</code></pre>
                <p class="mb-3">Clearly, the flag was right there, hidden among the extracted text — just as the challenge hinted.</p>

                <div class="bg-green-50 border-l-4 border-green-400 p-4 mt-4">
                    <p class="font-semibold text-green-700"><strong>Flag:</strong> <code class="text-green-600">EOF{hidden_among_bananananananana}</code></p>
                    <p class="text-sm mt-2">Hidden among the bananas, just like the challenge description suggested! 🍌</p>
                </div>
            </div>

            <div class="content-section">
                <h2 class="text-2xl font-bold mb-4">Key Insights</h2>

                <h3 class="text-xl font-semibold mb-3">Why This Challenge Works</h3>
                <ul class="list-disc list-inside space-y-2 mb-4">
                    <li>Simple steganography using embedded text in audio file</li>
                    <li>The "peels" metaphor referred to extracting the outer layer (strings)</li>
                    <li>No complex audio analysis needed - just text extraction</li>
                    <li>Demonstrates that not all audio steg requires spectrograms</li>
                </ul>

                <h3 class="text-xl font-semibold mb-3 mt-6">Tools Used</h3>
                <ul class="list-disc list-inside space-y-2">
                    <li><code>strings</code> - Extract printable strings from binary</li>
                    <li><code>grep</code> - Search for EOF pattern</li>
                </ul>

                <h3 class="text-xl font-semibold mb-3 mt-6">Alternative Methods</h3>
                <pre><code class="language-bash"># Method 1: View all strings
strings banananana.wav | less

# Method 2: Save strings to file
strings banananana.wav > output.txt
cat output.txt | grep "EOF"

# Method 3: Use hexdump
hexdump -C banananana.wav | grep -i "eof"</code></pre>

                <h3 class="text-xl font-semibold mb-3 mt-6">Summary Table</h3>
                <table class="w-full border-collapse border border-gray-300 mt-4">
                    <thead>
                        <tr class="bg-gray-100">
                            <th class="border border-gray-300 px-4 py-2">Step</th>
                            <th class="border border-gray-300 px-4 py-2">Action</th>
                            <th class="border border-gray-300 px-4 py-2">Result</th>
                        </tr>
                    </thead>
                    <tbody>
                        <tr>
                            <td class="border border-gray-300 px-4 py-2">1</td>
                            <td class="border border-gray-300 px-4 py-2">Analyzed the <code>.wav</code> file</td>
                            <td class="border border-gray-300 px-4 py-2">Contained hidden data</td>
                        </tr>
                        <tr>
                            <td class="border border-gray-300 px-4 py-2">2</td>
                            <td class="border border-gray-300 px-4 py-2">Used <code>strings</code> with <code>grep EOF</code></td>
                            <td class="border border-gray-300 px-4 py-2">Found embedded text</td>
                        </tr>
                        <tr>
                            <td class="border border-gray-300 px-4 py-2">3</td>
                            <td class="border border-gray-300 px-4 py-2">Extracted flag in <code>EOF{}</code> format</td>
                            <td class="border border-gray-300 px-4 py-2">Success!</td>
                        </tr>
                    </tbody>
                </table>
            </div>

            <div class="content-section bg-gradient-to-r from-yellow-50 to-orange-50">
                <h2 class="text-2xl font-bold mb-4">Challenge Theme</h2>
                <p class="mb-3">The challenge cleverly uses the banana theme:</p>
                <ul class="list-disc list-inside space-y-2">
                    <li><strong>"Obama loves banana"</strong> - Cultural reference to add humor</li>
                    <li><strong>"Peels scattered everywhere"</strong> - Metaphor for extracting the outer layer (strings)</li>
                    <li><strong>"Clean this mess"</strong> - Filter the noise to find the flag</li>
                    <li><strong>"bananananananana"</strong> - Multiple repetitions hiding the flag</li>
                </ul>
                <p class="mt-4 italic">A fun, straightforward steganography challenge that teaches the importance of basic forensic tools! 🍌</p>
            </div>
        </div>
    </div>

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