web：[GXYCTF2019]BabyUpload（文件上传、一句话木马、文件过滤）-编程知识

web：[GXYCTF2019]BabyUpload（文件上传、一句话木马、文件过滤）

题目

页面显示为文件上传

随便上传一个文件看看

上传一个文本文件显示

上传了一个图片显示

上传包含一句话木马的图片

上传了一个包含php一句话木马的文件，显示如上

换一个写法

上传成功

尝试上传.htaccess，上传失败，用抓包修改文件后缀

返回题目首页，找到了题目源码

<?php
session_start();
echo "<meta http-equiv=\"Content-Type\" content=\"text/html; charset=utf-8\" /> 
<title>Upload</title>
<form action=\"\" method=\"post\" enctype=\"multipart/form-data\">
上传文件<input type=\"file\" name=\"uploaded\" />
<input type=\"submit\" name=\"submit\" value=\"上传\" />
</form>";
error_reporting(0);
if(!isset($_SESSION['user'])){$_SESSION['user'] = md5((string)time() . (string)rand(100, 1000));
}
if(isset($_FILES['uploaded'])) {$target_path  = getcwd() . "/upload/" . md5($_SESSION['user']);$t_path = $target_path . "/" . basename($_FILES['uploaded']['name']);$uploaded_name = $_FILES['uploaded']['name'];$uploaded_ext  = substr($uploaded_name, strrpos($uploaded_name,'.') + 1);$uploaded_size = $_FILES['uploaded']['size'];$uploaded_tmp  = $_FILES['uploaded']['tmp_name'];if(preg_match("/ph/i", strtolower($uploaded_ext))){die("后缀名不能有ph！");}else{if ((($_FILES["uploaded"]["type"] == "") || ($_FILES["uploaded"]["type"] == "image/jpeg") || ($_FILES["uploaded"]["type"] == "image/pjpeg")) && ($_FILES["uploaded"]["size"] < 2048)){$content = file_get_contents($uploaded_tmp);if(preg_match("/\<\?/i", $content)){die("诶，别蒙我啊，这标志明显还是php啊");}else{mkdir(iconv("UTF-8", "GBK", $target_path), 0777, true);move_uploaded_file($uploaded_tmp, $t_path);echo "{$t_path} succesfully uploaded!";}}else{die("上传类型也太露骨了吧！");}}
}
?>

文件后缀名为image/jpeg，抓包修改文件后缀名