phpcgi.fixpathinfo,Nginx+PHPCGI的安全漏洞：fix_pathinfo

如果你正在使用nginx&＃43;php&＃xff0c;请关注。

表像&＃xff1a;

具体的重现过程&＃xff0c;用php代码修改后缀名后上传&＃xff0c;比如说www.xxx.com/1.jpg&＃xff0c;访问的时候用www.xxx.com/1.jpg/xxx.php 这段jpg代码将会被执行&＃xff01;&＃xff01;&＃xff01;

http://docs.php.net/manual/zh/ini.core.php

cgi.fix_pathinfo “1″ PHP_INI_ALL 从 PHP 4.3.0 起可用 请注意&＃xff1a;默认为1

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 ~ "^(.&＃43;\.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&＃39;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&＃39;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&＃61;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 (script_path_translated &&

(script_path_translated_len &＃61; strlen(script_path_translated)) > 0 &&

(script_path_translated[script_path_translated_len-1] &＃61;&＃61; &＃39;/&＃39; ||

....//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… So…

解决办法&＃xff1a;

1.修改php.ini中的cgi.cgi.fix_pathinfo为0(即使你在php.ini中没有搜到&＃xff0c;也要设置&＃xff0c;没有搜到表示默认为1)

2.判断文件上传类型时使用严格的判断&＃xff0c;至于怎么判断&＃xff0c;参见&＃xff1a;http://www.54chen.com/php-tech/php-upload-file-types-to-determine-the-complete-program-and-php-nginx-upload-size-and-complete-control-program.html

3.把nginx的判断正则修改为去除/

if ( $fastcgi_script_name ~ \..*\/.*php ) {

return 403;

}