https://blog.devobass-will.win/categories/miscellaneous/Recent content in Miscellaneous on Library of DevoruinaHugoen-USSun, 12 Oct 2025 12:20:16 +0700https://blog.devobass-will.win/posts/wannagame-freshmen-2025/Sun, 12 Oct 2025 12:20:16 +0700https://blog.devobass-will.win/posts/wannagame-freshmen-2025/<h1 id="catwithasteg">CatWithASteg<a href="#catwithasteg" class="heading-anchor" aria-label="Link to this section"><svg class="h-4 w-4" aria-hidden="true" xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24"><g fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2"><path d="M10 13a5 5 0 0 0 7.54.54l3-3a5 5 0 0 0-7.07-7.07l-1.72 1.71"/><path d="M14 11a5 5 0 0 0-7.54-.54l-3 3a5 5 0 0 0 7.07 7.07l1.71-1.71"/></g></svg></a></h1><ul> <li>We are given a file named <code>hiden.jpg</code>, which is an invalid <code>.jpg</code> file.</li> <li>Reading the file&rsquo;s header, we are met with:</li> </ul> <div class="code-block-container border-border bg-card my-6 overflow-hidden rounded-xl border shadow-sm transition-all duration-200 ease-out hover:-translate-y-0.5 hover:shadow-md" data-code-block data-code-id="code-0" data-collapsible="true" data-default-state="expanded" data-collapsed="false" data-auto-collapse-lines="30" data-auto-collapse-height="400" data-collapsed-height="120" > <div class="code-block-header bg-muted/30 border-border flex items-center justify-between border-b px-4 py-3" > <div class="flex items-center gap-2"> <div class="text-muted-foreground shrink-0"> <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M10 20l4-16m4 4l4 4-4 4M6 16l-4-4 4-4" /> </svg> </div> <span class="text-muted-foreground text-sm font-medium"> BASH </span> </div> <div class="flex items-center gap-2"> <button class="collapse-code-btn text-muted-foreground hover:text-primary hover:bg-primary/10 focus:ring-primary/20 flex items-center gap-1.5 rounded-md px-2 py-1 text-xs font-medium transition-all duration-200 ease-out focus:ring-2 focus:outline-none" type="button" data-code-action="toggle-collapse" data-label-expand="Expand" data-label-collapse="Collapse" title="Collapse" aria-label="Collapse" aria-controls="code-0" aria-expanded="true" > <span class="collapse-chevron transition-transform duration-200 ease-out"> <svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7" /> </svg> </span> <span class="collapse-text hidden sm:inline">Collapse</span> </button> <button class="copy-code-btn text-muted-foreground hover:text-primary hover:bg-primary/10 focus:ring-primary/20 flex items-center gap-1.5 rounded-md px-2 py-1 text-xs font-medium transition-all duration-200 ease-out focus:ring-2 focus:outline-none" type="button" data-code-action="copy" data-label-copy="Copy" data-label-copied="Copied" title="Copy" aria-label="Copy" > <span class="copy-icon"> <svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 16H6a2 2 0 01-2-2V6a2 2 0 012-2h8a2 2 0 012 2v2m-6 12h8a2 2 0 002-2v-8a2 2 0 00-2-2h-8a2 2 0 00-2 2v8a2 2 0 002 2z" /> </svg> </span> <span class="copy-text hidden sm:inline">Copy</span> </button> </div> </div> <div class="code-block-content relative" id="code-0"> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-bash" data-lang="bash"><span style="display:flex;"><span>$ hexdump -C hiden.jpg | head </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000000</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">23</span> <span style="color:#ae81ff">45</span> <span style="color:#ae81ff">67</span> <span style="color:#ae81ff">89</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">23</span> <span style="color:#ae81ff">45</span> <span style="color:#ae81ff">67</span> <span style="color:#ae81ff">89</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">23</span> <span style="color:#ae81ff">45</span> <span style="color:#ae81ff">67</span> <span style="color:#ae81ff">89</span> <span style="color:#ae81ff">01</span> |.#Eg..#Eg..#Eg..| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000010</span> <span style="color:#ae81ff">23</span> <span style="color:#ae81ff">45</span> <span style="color:#ae81ff">67</span> <span style="color:#ae81ff">89</span> aa aa aa aa ff 8d ff 0e <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">10</span> 4a <span style="color:#ae81ff">46</span> |<span style="color:#75715e">#Eg...........JF|</span> </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000020</span> <span style="color:#ae81ff">49</span> <span style="color:#ae81ff">46</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">60</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">60</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> ff e1 <span style="color:#ae81ff">00</span> be |IF.....<span style="color:#e6db74">`</span>.<span style="color:#e6db74">`</span>......| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000030</span> <span style="color:#ae81ff">45</span> <span style="color:#ae81ff">78</span> <span style="color:#ae81ff">69</span> <span style="color:#ae81ff">66</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> 4d 4d <span style="color:#ae81ff">00</span> 2a <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">08</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">06</span> |Exif..MM.*......| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000040</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">12</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">03</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> 1a <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">05</span> |................| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000050</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">56</span> <span style="color:#ae81ff">01</span> 1b <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">05</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> |.......V........| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000060</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> 5e <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">28</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">03</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">02</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> |...^.<span style="color:#f92672">(</span>..........| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000070</span> <span style="color:#ae81ff">02</span> <span style="color:#ae81ff">13</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">03</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">87</span> <span style="color:#ae81ff">69</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">04</span> |.............i..| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000080</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">66</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">60</span> |.......f.......<span style="color:#e6db74">`</span>| </span></span><span style="display:flex;"><span><span style="color:#ae81ff">00000090</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">60</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">01</span> <span style="color:#ae81ff">00</span> <span style="color:#ae81ff">06</span> <span style="color:#ae81ff">90</span> <span style="color:#ae81ff">00</span> |.......<span style="color:#e6db74">`</span>........|</span></span></code></pre></div> <div hidden data-code-source>$ hexdump -C hiden.jpg | head 00000000 01 23 45 67 89 01 23 45 67 89 01 23 45 67 89 01 |.#Eg..#Eg..#Eg..| 00000010 23 45 67 89 aa aa aa aa ff 8d ff 0e 00 10 4a 46 |#Eg...........JF| 00000020 49 46 00 01 01 01 00 60 00 60 00 00 ff e1 00 be |IF.....`.`......| 00000030 45 78 69 66 00 00 4d 4d 00 2a 00 00 00 08 00 06 |Exif..MM.*......| 00000040 01 12 00 03 00 00 00 01 00 01 00 00 01 1a 00 05 |................| 00000050 00 00 00 01 00 00 00 56 01 1b 00 05 00 00 00 01 |.......V........| 00000060 00 00 00 5e 01 28 00 03 00 00 00 01 00 02 00 00 |...^.(..........| 00000070 02 13 00 03 00 00 00 01 00 01 00 00 87 69 00 04 |.............i..| 00000080 00 00 00 01 00 00 00 66 00 00 00 00 00 00 00 60 |.......f.......`| 00000090 00 00 00 01 00 00 00 60 00 00 00 01 00 06 90 00 |.......`........|</div> <div class="collapse-overlay to-card/90 pointer-events-none absolute inset-0 bg-linear-to-b from-transparent via-transparent opacity-0 transition-opacity duration-300" hidden > <button class="collapse-overlay-btn text-muted-foreground bg-card/80 border-border/50 hover:bg-primary/10 hover:text-primary hover:border-primary/30 absolute bottom-4 left-1/2 flex -translate-x-1/2 items-center justify-center rounded-full border p-2 backdrop-blur-sm transition-all duration-200" type="button" data-code-action="expand" aria-label="Expand" title="Expand" > <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7" /> </svg> </button> </div> </div> </div> <ul> <li>We can see garbage date from line 0 to 10, from <code>01</code> to <code>aa</code>. To fix this, we need to extract the image by writing this file to another file, but skipping the first 24 bytes.</li> </ul> <div class="code-block-container border-border bg-card my-6 overflow-hidden rounded-xl border shadow-sm transition-all duration-200 ease-out hover:-translate-y-0.5 hover:shadow-md" data-code-block data-code-id="code-1" data-collapsible="true" data-default-state="expanded" data-collapsed="false" data-auto-collapse-lines="30" data-auto-collapse-height="400" data-collapsed-height="120" > <div class="code-block-header bg-muted/30 border-border flex items-center justify-between border-b px-4 py-3" > <div class="flex items-center gap-2"> <div class="text-muted-foreground shrink-0"> <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M10 20l4-16m4 4l4 4-4 4M6 16l-4-4 4-4" /> </svg> </div> <span class="text-muted-foreground text-sm font-medium"> SH </span> </div> <div class="flex items-center gap-2"> <button class="collapse-code-btn text-muted-foreground hover:text-primary hover:bg-primary/10 focus:ring-primary/20 flex items-center gap-1.5 rounded-md px-2 py-1 text-xs font-medium transition-all duration-200 ease-out focus:ring-2 focus:outline-none" type="button" data-code-action="toggle-collapse" data-label-expand="Expand" data-label-collapse="Collapse" title="Collapse" aria-label="Collapse" aria-controls="code-1" aria-expanded="true" > <span class="collapse-chevron transition-transform duration-200 ease-out"> <svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7" /> </svg> </span> <span class="collapse-text hidden sm:inline">Collapse</span> </button> <button class="copy-code-btn text-muted-foreground hover:text-primary hover:bg-primary/10 focus:ring-primary/20 flex items-center gap-1.5 rounded-md px-2 py-1 text-xs font-medium transition-all duration-200 ease-out focus:ring-2 focus:outline-none" type="button" data-code-action="copy" data-label-copy="Copy" data-label-copied="Copied" title="Copy" aria-label="Copy" > <span class="copy-icon"> <svg class="h-3 w-3" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M8 16H6a2 2 0 01-2-2V6a2 2 0 012-2h8a2 2 0 012 2v2m-6 12h8a2 2 0 002-2v-8a2 2 0 00-2-2h-8a2 2 0 00-2 2v8a2 2 0 002 2z" /> </svg> </span> <span class="copy-text hidden sm:inline">Copy</span> </button> </div> </div> <div class="code-block-content relative" id="code-1"> <div class="highlight"><pre tabindex="0" style="color:#f8f8f2;background-color:#272822;-moz-tab-size:4;-o-tab-size:4;tab-size:4;-webkit-text-size-adjust:none;"><code class="language-sh" data-lang="sh"><span style="display:flex;"><span>$ dd <span style="color:#66d9ef">if</span><span style="color:#f92672">=</span>hiden.jpg of<span style="color:#f92672">=</span>fixed.jpg bs<span style="color:#f92672">=</span><span style="color:#ae81ff">1</span> skip<span style="color:#f92672">=</span><span style="color:#ae81ff">24</span> </span></span><span style="display:flex;"><span>5857+1 records in </span></span><span style="display:flex;"><span>5857+1 records out </span></span><span style="display:flex;"><span><span style="color:#ae81ff">140589</span> bytes <span style="color:#f92672">(</span><span style="color:#ae81ff">141</span> kB, <span style="color:#ae81ff">137</span> KiB<span style="color:#f92672">)</span> copied, 0.000000000001 s, 9999.99 TB/s</span></span></code></pre></div> <div hidden data-code-source>$ dd if=hiden.jpg of=fixed.jpg bs=1 skip=24 5857&#43;1 records in 5857&#43;1 records out 140589 bytes (141 kB, 137 KiB) copied, 0.000000000001 s, 9999.99 TB/s</div> <div class="collapse-overlay to-card/90 pointer-events-none absolute inset-0 bg-linear-to-b from-transparent via-transparent opacity-0 transition-opacity duration-300" hidden > <button class="collapse-overlay-btn text-muted-foreground bg-card/80 border-border/50 hover:bg-primary/10 hover:text-primary hover:border-primary/30 absolute bottom-4 left-1/2 flex -translate-x-1/2 items-center justify-center rounded-full border p-2 backdrop-blur-sm transition-all duration-200" type="button" data-code-action="expand" aria-label="Expand" title="Expand" > <svg class="h-4 w-4" fill="none" stroke="currentColor" viewBox="0 0 24 24" xmlns="http://www.w3.org/2000/svg"> <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M19 9l-7 7-7-7" /> </svg> </button> </div> </div> </div> <ul> <li>However, it&rsquo;s still not a valid image because byte at 02 and 04 are wrong. Using tools like <code>dhex</code>, we fix the two bytes <code>8d</code> and <code>0e</code> into <code>d8</code> and <code>e0</code>, the resulting image is: <figure class="image-figure not-prose my-8" data-lightbox-enabled=" true " data-gallery-type="auto" data-image-width="0" data-image-height="0" data-image-src="https://hackmd.io/_uploads/HkXX7JB6xe.jpg" > <div class="image-container"> <img src="https://hackmd.io/_uploads/HkXX7JB6xe.jpg" alt="fixed" loading="lazy" decoding="async" data-gallery-src="https://hackmd.io/_uploads/HkXX7JB6xe.jpg" data-gallery-alt="fixed" data-gallery-title="" /></div> </figure> </li> </ul> <p>Flag: <code>W1{Y0u_4r3_v3ry_g00d_m3ow!}</code></p>