我们先看看源码
源码
代码语言：javascript复制$is_upload = false;
$msg = null;
if (isset($_POST['submit'])) {
if (file_exists(UPLOAD_PATH)) {
$deny_ext = array(".php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess");
$file_name = trim($_FILES['upload_file']['name']);
$file_ext = strrchr($file_name, '.');
$file_ext = strtolower($file_ext); //转换为小写
$file_ext = str_ireplace('::$DATA', '', $file_ext);//去除字符串::$DATA
$file_ext = trim($file_ext); //首尾去空
if (!in_array($file_ext, $deny_ext)) {
$temp_file = $_FILES['upload_file']['tmp_name'];
$img_path = UPLOAD_PATH.'/'.$file_name;
if (move_uploaded_file($temp_file, $img_path)) {
$is_upload = true;
} else {
$msg = '上传出错！';
}
} else {
$msg = '此文件类型不允许上传！';
}
} else {
$msg = UPLOAD_PATH . '文件夹不存在,请手工创建！';
}
}看看上面的代码都限制了多少吧，大小写，加空格，加字符串，黑名单，好多限制。。。。。
1.txt.php",".php5",".php4",".php3",".php2",".html",".htm",".phtml",".pht",".pHp",".pHp5",".pHp4",".pHp3",".pHp2",".Html",".Htm",".pHtml",".jsp",".jspa",".jspx",".jsw",".jsv",".jspf",".jtml",".jSp",".jSpx",".jSpa",".jSw",".jSv",".jSpf",".jHtml",".asp",".aspx",".asa",".asax",".ascx",".ashx",".asmx",".cer",".aSp",".aSpx",".aSa",".aSax",".aScx",".aShx",".aSmx",".cEr",".sWf",".swf",".htaccess"
这个时候可以采用一种方法来绕过，因为靶场是搭建在windows上的，所以windows有一个特性，windows系统自动去掉不符合规则符号后面的内容，什么意思呢？举个栗子
比如你新建了一个1.txt文件，然后你将名称改为1.txt.试试，虽然会有下面的警告，但是windows还是会默认去掉后面的.，名字还是变成了1.txt
这个时候我们就可以利用.来绕过限制了，因为strrchr函数会将上传的文件名后缀处理为.php.，当上传到win机器上时又会将后面的.去掉，然后后缀就又会被还原成.php，这样就可以执行了，下面演示一下
首先上传1.php文件并抓包，在burp修改文件后缀名为.php.
测试链接
PS:此方法只适用于windows主机
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本文链接：https://cloud.tencent.com/developer/article/1920632
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