主页又是个登陆。第一时间想到是sql注入。
抓包看看,然而单引号被过滤了。试了下斜杠。直接跳转到了hack.php
先放着。然后既然有登陆。那就试着register.php。
果然有。
注册个单引号用户。如果存在二次注入。就会报错。
登陆
随便翻翻。看见URL那个参数。base64搞一手。先偷index.php源码
由于page=guest。我猜测真实文件就是guest.php，那么我们直接写index就好了
index.php
<?php
require_once "function.php";
if(isset($_SESSION['login'] )){
Header("Location: user.php?page=info");
}
else{
include "templates/index.html";
}
?>
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");
}
?>
config.php
<?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();
$mysqli=null;
die();
}
?>
register.php
<?php
require_once "function.php";
if($_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");
}
?>
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";
?>
之前在function.php中。有一段过滤函数。ffffflag之类的。用的是parse_url和parse_str来判断URL中是否有危险字符。
而parse_url都是可以绕过了。在域名后面多加两个/即可绕过
尝试包含下
接着去访问html，有个文件上传。burp抓包看看
?????????????404。靶场出问题了？
这里。我试了下文件包含。发现文件存在。其实是html表单写错了
抓包修改下请求路径就好了
上传文件直接返回文件内容。再会过去看下源码
<?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);
}
?>
将路径和文件名拼接。文件名我们可控
然后执行cat 文件名|base64 -w 0
这条命令的意思是。将文件内容base64编码
最后通过下面的img标签输出
。这。赤裸裸的命令执行。啥也没过滤。先在本地测试下
会将ls的执行结果以base64输出
得到文件名
去根目录查看
环境的目录就是在./var下。所以..就到了根目录。用/会报错。估计是转义了后面的"。
尝试了下直接cat ../flag_23333
报错了can not move
php文件上传时。将缓存文件移动到目标目录由于存在特殊字符。就会报错
由于我们可以执行任意命令。那么直接base64解密。然后解密。传入
123.php;`echo Y2F0IC9mbGFnXzIzMzMzMw==|base64 -d`
由于会先执行反引号内的命令。先将base64解密。成为cat /flag_23333,然后传入|bas64 -w 0输出
