Nginx %00空字節執行任意代碼(php)漏洞

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空字節時與後端FastCGI處理不一致，導致可以在圖片中嵌入PHP代碼然後通過訪問xxx.jpg%00.php來執行其中的代碼

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.

<* 參考

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

*>

測試方法:

@Sebug.net   dis
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1. 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.
2.  
3. 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安全建議:

解決方案

升級nginx版本
http://nginx.org

@Sebug.net [ 2011-08-25 ]