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nginx/CVE-2013-4547/README.md

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+# Nginx Filename Logic Vulnerability (CVE-2013-4547)
+
+[中文版本(Chinese version)](README.zh-cn.md)
+
+Nginx is a web server that can be used as a reverse proxy, load balancer, mail proxy, and HTTP cache. Nginx 0.8.41 through 1.4.3 and 1.5.x before 1.5.7 allows remote attackers to bypass intended restrictions via an unescaped space character in a URI.
+
+This vulnerability is not directly related to code execution. The main cause is the incorrect parsing of request URIs, which leads to incorrect retrieval of user-requested filenames, resulting in privilege bypass and code execution as side effects.
+
+For example, when Nginx matches requests ending with .php, it sends them to fastcgi for parsing. A common configuration looks like this:
+
+```
+location ~ \.php$ {
+    include        fastcgi_params;
+
+    fastcgi_pass   127.0.0.1:9000;
+    fastcgi_index  index.php;
+    fastcgi_param  SCRIPT_FILENAME  /var/www/html$fastcgi_script_name;
+    fastcgi_param  DOCUMENT_ROOT /var/www/html;
+}
+```
+
+Under normal circumstances (with pathinfo disabled), only files with .php extensions are sent to fastcgi for parsing.
+
+However, in the presence of CVE-2013-4547, when we request `1.gif[0x20][0x00].php`, this URI matches the regular expression `\.php$` and enters this Location block. But after entering, Nginx incorrectly identifies the requested file as `1.gif[0x20]` and sets it as the value of `SCRIPT_FILENAME` to send to fastcgi.
+
+Fastcgi then parses based on the value of `SCRIPT_FILENAME`, ultimately resulting in a parsing vulnerability. Therefore, we only need to upload a file ending with a space to make PHP parse it.
+
+Here's another example. Many websites restrict backend access to specific IPs:
+
+```
+location /admin/ {
+    allow 127.0.0.1;
+    deny all;
+}
+```
+
+We can request the following URI: `/test[0x20]/../admin/index.php`. This URI won't match the location pattern `/admin/`, thus bypassing the IP verification. However, the actual requested file is `/test[0x20]/../admin/index.php`, which resolves to `/admin/index.php`, successfully accessing the backend. (This requires having a directory called "test ": this is a Linux system feature. If a directory doesn't exist, even when jumping to the parent directory, it will throw a file not found error. Windows doesn't have this restriction)
+
+References:
+
+ - http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-4547
+ - https://blog.werner.wiki/file-resolution-vulnerability-nginx/
+ - http://www.91ri.org/9064.html
+
+## Environment Setup
+
+Run the following command to start a Nginx server 1.4.2:
+
+```
+docker compose up -d
+```
+
+After the environment starts, visit `http://your-ip:8080/` to see an upload page.
+
+## Vulnerability Reproduce
+
+This server uses blacklist validation, and we cannot upload files with .php extensions. We need to exploit CVE-2013-4547. We upload a "1.gif " (note the space at the end):
+
+![](01.png)
+
+Visit `http://your-ip:8080/uploadfiles/1.gif[0x20][0x00].php`, and you'll find that PHP has been parsed:
+
+![](02.png)
+
+Note: [0x20] is a space, [0x00] is `\0`, and these characters don't need to be encoded.

nginx/CVE-2013-4547/README.zh-cn.md

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+# Nginx 文件名逻辑漏洞（CVE-2013-4547）
+
+Nginx 是一款Web服务器，可以作为反向代理、负载均衡、邮件代理、HTTP缓存等。Nginx 0.8.41 到 1.4.3 和 1.5.x 之前的版本存在一个文件名解析漏洞，允许远程攻击者绕过一些特定的限制，执行原本不允许执行的文件。
+
+这个漏洞的原理是，Nginx错误地解析了请求的URI，错误地获取到用户请求的文件名，导致出现权限绕过、代码执行等连带影响。
+
+举个例子，比如，Nginx匹配到.php结尾的请求，就发送给fastcgi进行解析，常见的写法如下：
+
+```
+location ~ \.php$ {
+    include        fastcgi_params;
+
+    fastcgi_pass   127.0.0.1:9000;
+    fastcgi_index  index.php;
+    fastcgi_param  SCRIPT_FILENAME  /var/www/html$fastcgi_script_name;
+    fastcgi_param  DOCUMENT_ROOT /var/www/html;
+}
+```
+
+正常情况下（关闭pathinfo的情况下），只有.php后缀的文件才会被发送给fastcgi解析。
+
+而存在CVE-2013-4547的情况下，我们请求`1.gif[0x20][0x00].php`，这个URI可以匹配上正则`\.php$`，可以进入这个Location块；但进入后，Nginx却错误地认为请求的文件是`1.gif[0x20]`，就设置其为`SCRIPT_FILENAME`的值发送给fastcgi。
+
+fastcgi根据`SCRIPT_FILENAME`的值进行解析，最后造成了解析漏洞。
+
+所以，我们只需要上传一个空格结尾的文件，即可使PHP解析之。
+
+再举个例子，比如很多网站限制了允许访问后台的IP：
+
+```
+location /admin/ {
+    allow 127.0.0.1;
+    deny all;
+}
+```
+
+我们可以请求如下URI：`/test[0x20]/../admin/index.php`，这个URI不会匹配上location后面的`/admin/`，也就绕过了其中的IP验证；但最后请求的是`/test[0x20]/../admin/index.php`文件，也就是`/admin/index.php`，成功访问到后台。（这个前提是需要有一个目录叫"test "：这是Linux系统的特点，如果有一个不存在的目录，则即使跳转到上一层，也会爆文件不存在的错误，Windows下没有这个限制）
+
+参考链接：
+
+ - http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2013-4547
+ - https://blog.werner.wiki/file-resolution-vulnerability-nginx/
+ - http://www.91ri.org/9064.html
+
+## 漏洞环境
+
+执行如下命令启动一个Nginx 1.4.2服务器：
+
+```
+docker compose up -d
+```
+
+环境启动后，访问`http://your-ip:8080/`即可看到一个上传页面。
+
+## 漏洞复现
+
+这个环境是黑名单验证，我们无法上传php后缀的文件，需要利用CVE-2013-4547。我们上传一个"1.gif "，注意后面的空格：
+
+![](01.png)
+
+访问`http://your-ip:8080/uploadfiles/1.gif[0x20][0x00].php`，即可发现PHP已被解析：
+
+![](02.png)
+
+注意，[0x20]是空格，[0x00]是`\0`，这两个字符都不需要编码。

nginx/CVE-2013-4547/docker-compose.yml

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+services:
+ nginx:
+   image: vulhub/nginx:1.4.2
+   volumes:
+    - ./nginx.conf:/usr/local/nginx/conf/nginx.conf
+    - ./index.php:/usr/local/nginx/html/index.php
+   ports:
+    - "8080:80"
+ php:
+   image: vulhub/php:5.6-fpm
+   command: 
+    - bash
+    - -c
+    - "mkdir -p /var/www/html/uploadfiles && chown -R www-data:www-data /var/www/html/uploadfiles && php-fpm"
+   volumes:
+    - ./index.php:/var/www/html/index.php
+    - ./www.conf:/usr/local/etc/php-fpm.d/zz-docker.conf

nginx/CVE-2013-4547/index.php

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+<?php
+if (!empty($_FILES)):
+
+// Check for errors
+if($_FILES['file_upload']['error'] > 0){
+    die('An error ocurred when uploading.');
+}
+
+// Check filesize
+if(!is_uploaded_file($_FILES['file_upload']['tmp_name'])) {
+    die('File is not uploaded file');
+}
+
+$ext = pathinfo($_FILES['file_upload']['name'], PATHINFO_EXTENSION);
+if (empty($ext) || in_array($ext, ['php', 'php3', 'php5', 'phtml'])) {
+    die('Unsupported filetype uploaded.');
+}
+
+$new_name = __DIR__ . '/uploadfiles/' . $_FILES['file_upload']['name'];
+if(!move_uploaded_file($_FILES['file_upload']['tmp_name'], $new_name)){
+    die('Error uploading file - check destination is writeable.');
+}
+
+die('File uploaded successfully: ' . $new_name);
+
+else:
+?>
+<form method="post" enctype="multipart/form-data">
+    File: <input type="file" name="file_upload">
+    <input type="submit">
+</form>
+<?php
+endif;

nginx/CVE-2013-4547/nginx.conf

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+worker_processes  1;
+
+events {
+    worker_connections  1024;
+}
+
+
+http {
+    include       mime.types;
+    default_type  application/octet-stream;
+
+    sendfile        on;
+    keepalive_timeout  65;
+
+    server {
+        listen       80;
+        server_name  localhost;
+        root   html;
+        index  index.php;
+
+        charset utf-8;
+
+        location ~ \.php$ {
+           root           html;
+           include        fastcgi_params;
+
+           fastcgi_pass   php:9000;
+           fastcgi_index  index.php;
+           fastcgi_param  SCRIPT_FILENAME  /var/www/html$fastcgi_script_name;
+           fastcgi_param  DOCUMENT_ROOT /var/www/html;
+        }
+    }
+}

nginx/CVE-2013-4547/www.conf

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+[global]
+daemonize = no
+
+[www]
+listen = 9000
+security.limit_extensions = 
+php_admin_flag[cgi.fix_pathinfo] = off