现在普遍的Nginx + PHP cgi的做法是在配置文件中，通过正则匹配设置SCRIPT_FILENAME，今天又发现了一个这种方式的安全漏洞。比如，有，那么通过构造如下的URL，就可以看到fake.jpg的二进制内容：
为什么会这样呢?比如，如下的nginx conf：
location ~ \.php($|/) {fastcgi_pass 127.0.0.1:9000;
fastcgi_index index.php;
set $script $uri;
set $path_info "";
if ($uri ~ "^(.+\.php)(/.*)") {
set $script $1;
set $path_info $2;
}
include fastcgi_params;
fastcgi_param SCRIPT_FILENAME $document_root$script;
fastcgi_param SCRIPT_NAME $script;
fastcgi_param PATH_INFO $path_info;
}
通过正则匹配以后，SCRIPT_NAME会被设置为"fake.jpg/foo.php"，继而构造成SCRIPT_FILENAME传递个PHP CGI，但是PHP又为什么会接受这样的参数，并且把a.jpg解析呢？
这就要说到PHP的cgi SAPI中的参数，fix_pathinfo了：
; cgi.fix_pathinfo provides *real* PATH_INFO/PATH_TRANSLATED support for CGI. PHP's; previous behaviour was to set PATH_TRANSLATED to SCRIPT_FILENAME，and to not grok
; what PATH_INFO is. For more information on PATH_INFO，see the cgi specs. Setting
; this to 1 will cause PHP CGI to fix it's paths to conform to the spec. A setting
; of zero causes PHP to behave as before. Default is 1. You should fix your scripts
; to use SCRIPT_FILENAME rather than PATH_TRANSLATED.
cgi.fix_pathinfo=1 如果开启了这个选项，那么就会触发在PHP中的如下逻辑：/*
* if the file doesn't exist，try to extract PATH_INFO out
* of it by stat'ing back through the 'http://down.chinaz.com/'
* this fixes url's like /info.php/test
*/
if (script_path_translated &&
(script_path_translated_len = strlen(script_path_translated)) > 0 &&
(script_path_translated[script_path_translated_len-1] == 'http://down.chinaz.com/' ||
....//以下省略. 到这里，PHP会认为SCRIPT_FILENAME是fake.jpg，而foo.php是PATH_INFO，然后PHP就把fake.jpg当作一个PHP文件来解释执行…所以这个隐患的危害是巨大的。对于一些论坛来说，如果上传一个图片(实际上是恶意的PHP脚本)，继而构造这样的访问请求。
所以，大家如果有用这种服务器搭配的，请排查，如果有隐患，请把fix_pathinfo设置为0关闭(默认是开启的)。设置为
另: 我认为这个和Nginx没啥关系，不属于Nginx的漏洞. 是配置的问题，现在到处都在说是Nginx的Bug，不妥不妥.