一次代码审计实战案例「思路流程」
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/10d4f5678d5843679517406ad97026b7~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=uuay8ECUjbWLwrOMuFzpABihHus%3D" style="width: 50%; margin-bottom: 20px;"></div>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">前言：</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">利用这个 CMS <span style="color: black;">瞧瞧</span>能<span style="color: black;">不可</span>挖到漏洞，运气还是不错地挖到了两个，分别是 SSRF 与文件覆盖 GETSHELL，下面给<span style="color: black;">大众</span>讲解一下这次审计的思路过程。该 CMS 版本是 4.2。以下漏洞均被 CNVD 收录。</span></p>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">环境说明：</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">PHP版本用 7.0.9 就好了。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/e93f248a3178428c9c025e2335d36b0e~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=3I66tntIfNxUzstpU3iIgryNcTw%3D" style="width: 50%; margin-bottom: 20px;"></div>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">SSRF：</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">按照</span>功能点定向审计，在后台的工具栏有一个采集功能，<span style="color: black;">按照</span>经验这种功能<span style="color: black;">通常</span>存在 SSRF。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/3ceff708779c48199d547b34399da151~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=mD7r%2FLyGUhxNUqwK%2BfTva%2BS19d4%3D" style="width: 50%; margin-bottom: 20px;"></div>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/12ee971de2934982b6b97d00a071b094~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=R11ke%2BXXMIe0%2B3vI9T5F3HPszkM%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">运用</span> python3 在本地开启简易的 http 服务。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/ba434fc8ad3f4c028fafbb1a28867ecd~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=QGuSxAARbc2PsG4ZX%2Bcj3vfm290%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">点击下一步，果不其然的存在 SSRF。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/68ccacf08907408b807d26994508a45c~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=EjEuY0ic3tgfF7R0paX2nP2sZws%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">进行漏洞分析。</span></p>
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<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;">7、全套工具包</p>8、应急响应笔记
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">按照</span> burpsuite 抓到的请求包很容易定位到代码的位置。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/0ed18ef3650944ce828f713f3c6ba1ac~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=55dd4JMlUcW5HISg9Lz8UvPazaw%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;">该文件 </p>upload/plugins/sys/admin/Collect.php#Collect->add，POST 的参数cjurl 未做安全处理被传入到 $this->caiji->str <span style="color: black;">办法</span>。
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/252fc0ef60ef473580826a3e43671caa~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=vzXvjKAPmooWUBd7YgWFdCE4g%2Bs%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">那样</span><span style="color: black;">咱们</span>跟进到 $this->caiji->str <span style="color: black;">办法</span>，<span style="color: black;">然则</span> phpstorm 找不到定义该<span style="color: black;">办法</span>的位置。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/0426723d83a6443da7fbf156b42ed5af~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=oZ1yJDw47yYfBxSa6bkq6KrfnWI%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">处理</span>办法，<span style="color: black;">咱们</span><span style="color: black;">能够</span>连续按两下 Shift 键直接寻找。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/504aff8ee5d147f198d129768b22e775~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=5a8%2FKKixIvsC3LLTJrHXw%2F%2FrElI%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">跟进到 str <span style="color: black;">办法</span>后，<span style="color: black;">发掘</span> url 参数被传入 htmlall <span style="color: black;">办法</span>，继续跟进该<span style="color: black;">办法</span>。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/476716c68bca418fa319333968f8714c~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=v6Jl2QMLhVNzQaZfcf%2FzrnK8JEk%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">能够</span>看到 htmlall 方法<span style="color: black;">运用</span>了 curl 请求 url。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/70075d5946254f8eb0a4397088728f16~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=seqLUjED5Qgw6Ntlj9P8Kd%2BoE6Q%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">基本上有调用 $this->caiji->str <span style="color: black;">办法</span>的<span style="color: black;">地区</span>都存在 SSRF 漏洞。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/1ae49a7f974445b18e92a10089904691~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=gZqYRXSVeAZ5M5MS4uPYffdopNM%3D" style="width: 50%; margin-bottom: 20px;"></div>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">文件覆盖<span style="color: black;">引起</span> GETSHELL：</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">经过</span><span style="color: black;">敏锐</span>函数回溯参数过程的方式找到该漏洞。</p><span style="color: black;">
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;">在 </p>upload/cscms/app/helpers/common_helper.php#write_file <span style="color: black;">运用</span>了文件写入的<span style="color: black;">敏锐</span>函数，跟 SSRF 的 htmlall 是同一个文件。
</span>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/582ede178617487a8f26e1bb79cc446a~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=46FuVRYt4nkCK0vjXbCC9rii%2BLI%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">运用</span> Ctrl+Shift+F <span style="color: black;">查询</span><span style="color: black;">那些</span>位置调用了 write_file，在 </p>upload/plugins/sys/admin/Plugins.php#Plugins->_route_file 调用了 write_file函数，并且 $note[$key] 和 $note[$key] 的值是以字符串方式拼接到文件内容的，该内容是注释，<span style="color: black;">咱们</span><span style="color: black;">能够</span><span style="color: black;">运用</span>换行绕过。
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/bdbec19f58cc44298f461e0808ba81ef~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=mAUde8aZXRVlrdW6naK4CgyNH%2BI%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">查询</span><span style="color: black;">那些</span>位置调用了 _route_file，跟踪 $note 的值<span style="color: black;">是不是</span>可控，调用该函数的位置有<span style="color: black;">非常多</span>，<span style="color: black;">最后</span>找到一处可利用。在 </p>upload/plugins/sys/admin/Plugins.php#Plugins->setting_save 调用了 _route_file，<span style="color: black;">因为</span>该函数内容有点多，<span style="color: black;">因此</span>我将它拆分成两个界面，<span style="color: black;">有些</span>不重要的内容进行闭合。画红线的位置是调用到 _route_file 必须设置的，<span style="color: black;">能够</span>看到在标蓝色3的位置获取到了 $note 的值，分析到<span style="color: black;">这儿</span><span style="color: black;">能够</span><span style="color: black;">起始</span>复现了。
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/df3ddaf729da492ab61022e1b5a7c1a5~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=r1s2HfoEBnotS1Qg3YP%2BzVSxHDg%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">运用</span> burpsuite 抓取请求包。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/4ffe5f4a2b864d96ab9beaa168b8a334~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=iYpyzUk8JpO173Dk%2BNk%2FBYFaeYs%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">修改请求包内容写入构造好的代码，<span style="color: black;">能够</span>看到我<span style="color: black;">运用</span>了什么 %0a 换行去绕过去注释。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/d7b94c448b7446898bad3976a1d8b4d3~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=H4kBPiYTu8vF01EKQXqV77%2Fy0LQ%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;">在 </p>upload/cscms/config/dance/rewrite.php <span style="color: black;">能够</span>看到成功写入。
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/6ff631874f1545f9990f865dbbd07697~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=Xl5jwW6itW%2FJ%2B7B35lqH5T%2BRWT0%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">寻找引用 rewrite.php 的位置，懒得去看代码了，<span style="color: black;">经过</span>点击各个页面，经过不懈<span style="color: black;">奋斗</span><span style="color: black;">最终</span>在个人中心的音乐页面找到，<span style="color: black;">因此</span>你需要注册一个会员用户。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/7d9dab71c1904bb79048e04f30c09b34~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=32mEjcn%2BnE3sBNTSODKxkq4pHzI%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">重放 burpsuite 抓到的请求包，成功输出内容。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p26-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/7828e600dd3646299054d0235d9ecc53~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=i6GncgUwIWgNsfAGdXVU%2BYmgK9Q%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">到<span style="color: black;">这儿</span>其实事情还<span style="color: black;">无</span>结束，当我尝试写入恶意内容<span style="color: black;">发掘</span>被转移了。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/32efb093f8e64b9f80814de061a69281~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=zt2LYSJPV6bY9ScHUvyUp%2BpgSwA%3D" style="width: 50%; margin-bottom: 20px;"></div>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/c079660b206242518a390cf0f286e1be~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=sttbh9W3YmrHZvdhVPlU2asHpx0%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">试了 eval、shell_exec 等均被转移，<span style="color: black;">然则</span> assert <span style="color: black;">无</span>被转移，<span style="color: black;">思虑</span>到 assert 在PHP7版本之后的问题，我还是需要找一个更好的办法。懒得去看转义的代码了，我<span style="color: black;">按照</span>PHP的动态特性<span style="color: black;">运用</span>以下<span style="color: black;">办法</span>成功 RCE。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/32aaed647a3a431d867288fdd1e8edb9~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=Quc6CuWsZR5CtPc70bpTA%2Fz%2Fq%2BQ%3D" style="width: 50%; margin-bottom: 20px;"></div>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-qvj2lq49k0/3fb0d5b39d844fb8bd2d76114b0e88f7~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1729839620&x-signature=4goNSCx4t5MuLCIfUXJYMesA2Fc%3D" style="width: 50%; margin-bottom: 20px;"></div>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">总结：</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">此次代码审计<span style="color: black;">运用</span>了通用代码审计思路的两种，<span style="color: black;">第1</span>种：<span style="color: black;">按照</span>功能点定向审计、第二种：<span style="color: black;">敏锐</span>函数回溯参数过程，<span style="color: black;">无</span>用到的是通读全文代码。活用 phpstorm <span style="color: black;">能够</span>让代码审计的效率大大<span style="color: black;">增多</span>。</span></p>
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