Nginx %00空字节执行任意代码(php)漏洞

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本文介绍了一个存在于旧版本Nginx中的安全漏洞，该漏洞允许攻击者利用特定请求执行任意PHP代码。当Nginx接收到包含%00空字节的URL时，如果该URL指向的是被Nginx服务的文件（例如图片），攻击者可以通过构造恶意请求使这些文件作为PHP脚本执行。文章提供了漏洞的触发条件、影响范围以及缓解措施。

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漏洞版本:

nginx 0.5.*
nginx 0.6.*
nginx 0.7 <= 0.7.65
nginx 0.8 <= 0.8.37

漏洞描述:

Possible Arbitrary Code Execution with Null Bytes, PHP, and Old Versions of nginx

Ngnix在遇到%00空字节时与后端FastCGI处理不一致，导致可以在图片中嵌入PHP代码然后通过访问xxx.jpg%00.php来执行其中的代码

In vulnerable versions of nginx, null bytes are allowed in URIs by default (their presence is indicated via a variable named zero_in_uri defined in ngx_http_request.h). 

Individual modules have the ability to opt-out of handling URIs with null bytes. However, not all of them do; in particular, the FastCGI module does not.

<* 参考

https://nealpoole.com/blog/2011/07/possible-arbitrary-code-execution-with-null-bytes-php-and-old-versions-of-nginx/

测试方法:

@Sebug.net dis
本站提供程序(方法)可能带有攻击性,仅供安全研究与教学之用,风险自负!

   The attack itself is simple: a malicious user who makes a request to http://example.com/file.ext%00.php causes file.ext to be parsed as PHP.
 
 If an attacker can control the contents of a file served up by nginx (ie: using an avatar upload form) the result is arbitrary code execution. This vulnerability can not be mitigated by nginx configuration settings like try_files or PHP configuration settings like cgi.fix_pathinfo: the only defense is to upgrade to a newer version of nginx or to explicitly block potentially malicious requests to directories containing user-controlled content.

Sebug安全建议:

解决方案

升级nginx版本
http://nginx.org

@Sebug.net [ 2011-08-25 ]