cgi.fix_pathinfo=1时终极解决Nginx文件类型错误解析漏洞的方法

关于漏洞原理参见 nginx文件类型错误解析漏洞 ，最开始是直接把php.ini中设置 cgi.fix_pathinfo = 0想一劳永逸解决。不过后来发现其导致PHP的超全局变量 $_SERVER['PHP_SELF']为空于是有些程序会出错（比如Discuz会拼接出错误图片头像路径）。于是考虑在保持 cgi.fix_pathinfo =1时如何避免漏洞。网上搜索到的解决办法挺多比如 再提供一种解决Nginx文件类型错误解析漏洞的方法 ，因为 ifisEvil   加上正则判断存在漏判问题，所以尝试使用其他方式解决。

 经过试验找到一个终极解决办法，用try_files替代if判断文件

try_files $fastcgi_script_name =404;

 debug日志中会有类似判断

*308 trying to use file: "/robots.txt/a.php" "/var/htdoc/mychery.net/robots.txt/a.php"

 之前在网上搜索到一个办法，经过测试是无效的

try_files $request_filename =404;  #无效的用法！

 debug日志如下，判断路径重复拼接是错误的

*339 trying to use file: "/var/htdoc/mychery.net/robots.txt/a.php" "/var/htdoc/mychery.net/var/htdoc/mychery.net/robots.txt/a.php"

 

 

可以把正确的判断命令加入到fastcgi.conf中：

fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
fastcgi_param QUERY_STRING $query_string;
fastcgi_param REQUEST_METHOD $request_method;
fastcgi_param CONTENT_TYPE $content_type;
fastcgi_param CONTENT_LENGTH $content_length;

fastcgi_param SCRIPT_NAME $fastcgi_script_name;
fastcgi_param REQUEST_URI $request_uri;
fastcgi_param DOCUMENT_URI $document_uri;
fastcgi_param DOCUMENT_ROOT $document_root;
fastcgi_param SERVER_PROTOCOL $server_protocol;

fastcgi_param GATEWAY_INTERFACE CGI/1.1;
fastcgi_param SERVER_SOFTWARE nginx/$nginx_version;

fastcgi_param REMOTE_ADDR $remote_addr;
fastcgi_param REMOTE_PORT $remote_port;
fastcgi_param SERVER_ADDR $server_addr;
fastcgi_param SERVER_PORT $server_port;
fastcgi_param SERVER_NAME $server_name;

# PHP only, required if PHP was built with --enable-force-cgi-redirect
fastcgi_param REDIRECT_STATUS 200;

try_files $fastcgi_script_name =404;

然后在location中引用它：

location ~ \.php$ {
    fastcgi_pass unix:/tmp/phpfpm/php-fpm.sock;
    include   fastcgi.conf;
}

  另外，nginx官方推荐使用try_files替代if相应功能。