Buuctf PHPweb

考点

• PHP回调函数
• 反序列化代码执行
• 系统命令执行（find查找文件）

参考连接：PHP命令执行&代码执行

WP

页面读取不到什么信息，抓个包看到传了俩个参数
func，p。猜测可能是function和parameter。

试试一下查看源代码

   <?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...");
        }
    }
    ?>

    $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...");
        }
    }

过滤了一些函数，$result的类型必须是string，查看目录的scandir命令用不上了，尝试读取flag.php也无果。发现有一个类和没有过滤unserialize函数，可以试试反序列化执行

但是没有关于flag的文件，试试find命令
find / -name ‘*flag*’：查找根目录及其子目录下文件名里有flag的文件。
最后打开就OK了