章 32. 隐藏 PHP

一般而言,通过隐藏的手段提高安全性被认为是作用不大的做法。但某些情况下,尽可能的多增加一份安全性都是值得的。

一些简单的方法可以帮助隐藏 PHP,这样做可以提高攻击者发现系统弱点的难度。在 php.ini 文件里设置 expose_php = off ,可以减少他们能获得的有用信息。

另一个策略就是让 web 服务器用 PHP 解析不同扩展名。无论是通过 .htaccess 文件还是 Apache 的配置文件,都可以设置能误导攻击者的文件扩展名:

例子 32-1. 把 PHP 隐藏为另一种语言

# 使PHP看上去像其它的编程语言
AddType application/x-httpd-php .asp .py .pl
或者干脆彻底隐藏它:

例子 32-2. 使用未知的扩展名作为 PHP 的扩展名

# 使 PHP 看上去像未知的文件类型
AddType application/x-httpd-php .bop .foo .133t
或者把它隐藏为 HTML 页面,这样所有的 HTML 文件都会通过 PHP 引擎,会为服务器增加一些负担:

例子 32-3. 用 HTML 做 PHP 的文件后缀

# 使 PHP 代码看上去像 HTML 页面
AddType application/x-httpd-php .htm .html
要让此方法生效,必须把 PHP 文件的扩展名改为以上的扩展名。这样就通过隐藏来提高了安全性,虽然防御能力很低而且有些缺点。


add a note add a note User Contributed Notes
simon at carbontwelevedesign dot co dot uk
10-Aug-2006 08:31
I use the following in the .htaccess document

<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule . /index.php [L]
</IfModule>

then the following simple code

<?php

$permalinks
= explode("/",$_SERVER['REQUEST_URI']);

$varone = $permalinks[1];
$vartwo = $permalinks[2];

...

?>
marpetr at NOSPAM dot gmail dot com
11-Apr-2006 08:18
I think the best way to hide PHP on Apache and Apache itself is this:

httpd.conf
-------------
# ...
# Minimize 'Server' header information
ServerTokens Prod
# Disable server signature on server generated pages
ServerSignature Off
# ...
# Set default file type to PHP
DefaultType application/x-httpd-php
# ...

php.ini
------------
; ...
expose_php = Off
; ...

Now the URLs will look like this:
http://my.server.com/forums/post?forumid=15

Now hacker knows only that you are using Apache.
ahmad at unikomcenter dot com
06-Mar-2006 02:05
I am use this script to hidding PHP:

index.php
--------------
<?php

// PARSING QUERY STRING
$QS=explode("&",$_SERVER['QUERY_STRING']);
$QS=explode('/',$QS[0]);

// IF Modul is Undefined set it to index
if (!$QS[0]) $MODUL='index';
else
$MODUL=strtolower($QS[0]);

// WE can make a Variable $_QUERY
// for alternative _GET
for ($i=1;$i<count($QS);$i+=2)
{
  
$_QUERY[$NVAR]=$NVAR=$QS[$i];
   $
$NVAR=$QS[$i+1];
}

// Check the Modul is exists?
if (!file_exists("modul_directory/{$MODUL}.php"))
  
$MODUL="index";

#### THIS IS EXAMPLE TO IMPLEMENTATION THE SCRIPT
// Load The Template
include("template.php");
// Load The Module
include("modul_directory/{$MODUL}.php");
// Load The Footer
include("footer.php");

?>

we can access the modul in URL like this:
=================================

www.example.com/?forum/topic/20
- it mean load the modul forum.php, and set the _QUERY['topic']=20

www.foo.com/?voting/id/54/type/piechart&choice=2
- it mean load the modul voting.php, and set the _QUERY['id']=54 and _QUERY['type']='piechart' and set _GET['choice']=2
eric at ericwing dot net
21-Jan-2006 01:20
Something that has not been mentioned here is also the PHPSESSION id that will be displayed in the URL when passing it from page to page using GET.  If users have cookies set to off, this will be visible. This can be reset before any session_start() call with ini_set(). Be aware however that this can't be changed in this way if you use autho session start.
dyer85 at gmail dot com
31-Dec-2005 04:55
Although it's probably obvious to most people, Yavuz Darendelioglu's post below utilizes a method that will only work on a *nix OS, not Windows, and probably not Mac.

Also, his regex uses some superfluous matching, instead, write the redirect like so: (you don't really need to use absolute path when redirecting to a resource on the same server, either):

RedirectMatch (?:awstats|xmlrpc) /deny.php
28-Dec-2005 11:29
Even you hide your PHP, requests for bugy scripts still come.
No matter whether you have the script on your server or not.

You can make an additional step for those requests. Since the host now trying that buggy script  then, in the future when a new bug arises it will be tried  by that host again with a high possibility. So banning that host completey at its first attempt may be a good idea. For  this,

1- Add Permanent links for those requests in your httpd.conf:
RedirectMatch permanent (.*)awstats(.*)$ http://your_server/your_script.html

RedirectMatch permanent (.*)xmlrpc(.*)$ http://your_server/your_script.html
and add whatever you want to ban.

2- Write following code in your_script.html
<?
$host
= $_SERVER['REMOTE_ADDR'];
$dropit = "iptables -A INPUT -i eth0 -p tcp -s $host -m multiport --destination-ports 80,25,22 -j DROP";
shell_exec($dropit);
exit
?>

Yavuz Darendelioglu
user at pampelhuber dot invalid
18-Dec-2005 08:32
It is unnecessary, to let every Pampelhuber inspect your 'php.ini' files.
Put the following into the .htaccess of your htdocuments' root:

#Obscure 'php.ini' files (where they exist)
RedirectMatch 404 .*php\.ini$
jtw90210
30-Jun-2005 04:19
In order to get the PATH_INFO to work in order to pass parameters using a hidden program/trailing slash/"pretty url" in more recent versions of PHP you MUST add "AcceptPathInfo On" to your httpd.conf.

AddType application/x-httpd-php .php .html
AcceptPathInfo On

Try it out with your phpinfo page and you'll be able to search for PATH_INFO.

http://yourserver.com/myphpinfo.php/showmetheway

If you want to drop the .php use one or both of these:
DefaultType application/x-httpd-php
ForceType application/x-httpd-php
26-May-2005 04:06
You could also do this in .htaccess when you use Apache and your configuration allows you to override :

<Files test>
   ForceType application/x-httpd-php
</Files>

That way, you can use the URL test?pop=true without having to fake it by using test/index.php.

See the Apache manual for more info: http://httpd.apache.org/docs/mod/mod_mime#forcetype
benjamin at sonntag dot fr
25-May-2005 12:14
In response to the previous messages, for apache, there is a easier way to set files without "." to be executed by PHP, just put this in a ".htaccess" file :

DefaultType  application/x-httpd-php
dimitar at bastun dot net
18-Jan-2005 01:13
In case there are an Internal Server error(error 500) using the old code below in an .htaccess file, you can replace it with the code modification that must solve the problem.

Old code
-----------

<Files ~ "^[^\.]+$">
       ForceType application/x-httpd-php
</Files>

Replacement of the code above(code modification)
------------------------------------------------------------

AddHandler server-parsed .php
<Files ~ "^[^\.]+$">
SetHandler application/x-httpd-php
</Files>

Regards,
Dimitar Tanev
Nikolai-Zujev-(at)-Gmail-dot-Com
23-Sep-2004 03:22
Assign files w/o extension to php interpreter
without using ReWrite module

[clip httpd.conf]

<Files ~ "^[^\.]+$">
       ForceType application/x-httpd-php
</Files>

[/clip]
php at vfmedia dot de
15-Jun-2004 09:21
Ive found an easy way to hide php code and the uri is searchable by google and others...(only for unix or linux)

At first I have some rules in my hide.conf (i made an extra .conf for it (apache 2.0))

For example when I want to mask the index.php

<Files index>
 ForceType application/x-httpd-php
 </Files>

My problem is, that my code should be readable...

so I made an extra folder for example srv/www/htdocs/static_output

My phpcode is in the includefolder....(for ex. mnt/source/index.php)

Then I made a link in the shell  > ln mnt/source/index.php srv/www/htdocs/static_output/index

So the code is readable (with .php extension) in my includefolder and there is only the link in the srv folder without extension(which is called by the browser...).
12-May-2004 11:20
Keep in mind, if your really freaked out over hiding PHP, GD will expose you.

Go ahead - make an image with GD and open with a text editor.. Somewhere in there you'll see a comment with gd & php all over it.
php at user dot net
11-Apr-2004 09:36
What about this in a .htaccess file :

RewriteEngine on
RewriteRule    ^$    /index.php    [L]
RewriteRule    ^([a-zA-Z0-9\-\_/]*)/$    /$1/index.php    [L]
RewriteRule    ^([a-zA-Z0-9\-\_/]*)\.(html|htm)$    /$1.php    [L]
RewriteRule    ^([a-zA-Z0-9\-\_/]*)$    /$1.php    [L]

Typing "sub.domain.foo/anything" loads "/anything/index.php" if 'anything' is a directory, else it loads "/anything.php".

I'm sure you can find mutch better, but it works great on my site :)
mmj
14-Mar-2004 09:58
You can see if somebody's using PHP just by adding the following to the end of the URL:
?=PHPB8B5F2A0-3C92-11d3-A3A9-4C7B08C10000
If the page is using PHP, this will show the PHP credits.

Setting expose_php to Off in php.ini prevents this.
Elora at alexandria dot cc
14-Feb-2004 07:30
<bminton at efn dot org>'s suggestion won't work. All someone has to do is look at "foo.com/dir/" and try "foo.com/dir/index.html", "foo.com/dir/index.php", "foo.com/dir/index.cgi", until no 403/404 is returned.
ldemailly at qualysNOSPAM dot com
28-Oct-2003 12:17
adding MultiViews to your apache Options config
lets you hide/omit .php in the url without any rewriting, etc...
l0rdphi1 at liquefyr dot com
21-Jul-2003 07:02
More fun includes files without file extensions.

Simply add that ForceType application/x-httpd-php bit to an Apache .htaccess and you're set.

Oh yea, it gets even better when you play with stuff like the following:

substr($_SERVER['PATH_INFO'],1);

e.g. www.yoursite.com/somepage/55

And:

foreach ( explode('/',$_SERVER['PATH_INFO']) as $pair ) {
   list($key,$value) = split('=',$pair,2);
   $param[$key] = stripslashes($value);
}

e.g. www.yoursite.com/somepage/param1=value1/param2=value2/etc=etc

Enjoy =)
Bryce Nesbitt at Obviously.COM
28-Mar-2003 12:24
Using the .php extension for all your scripts is not necessary, and in fact can be harmful (by exposing too much information about your server, and by limiting what you can do in the future without breaking links). There are several ways to hide your .php script extension:

(1) Don't hard code file types at all.  Don't specify any dots, and most web servers will automatically find your .php, .html, .pdf, .gif or other matching file. This is called canonical URL format:
     www.xxxxxx.com/page
   www.xxxxxx.com/directory/
This gives you great flexibility to change your mind in the future, and prevents Windows browsers from making improper assumptions about the file type.

(2) In an Apache .htaccess file use:
   RewriteEngine on
   RewriteRule page.html page.php

(3) Force the webserver to interpret ALL .html files as .php:
   AddType application/x-httpd-php .php3 .php .html
bminton at efn dot org
28-Feb-2003 04:05
Another technique is to have every file be named index.php and be in it's own directory.  Then instead of using for instance http://my.site/foo.php you could use http://my.site/foo/ where foo is a directory with a file called index.php in it.
30-Jan-2003 02:53
PS. If you want to use pretty URLs (i.e. hide your .php extensions) AND you have safe-mode=on, the previous example (ForceType) won't work for you.  The problem is that safe-mode forces Apache to honor trailing characters in a requested URL.  This means that:

http://www.foo.com/home

would still be processed by the home script in our doc root, but for:

http://www.foo.com/home/contact_us.html

apache would actually look for the /home/contact_us.html file in our doc root.

The best solution I've found is to set up a virtual host (which I do for everything, even the default doc root) and override the trailing characters handling within the virtual host.  So, for a virtual host listening on port 8080, the apache directives would look like this:

<VirtualHost *:8080>
   DocumentRoot /web/doc_root
   Alias /home "/web/doc_root/home.php"
   AcceptPathInfo On
</VirtualHost>

Some people might question why we are overriding the trailing characters handling (with the AcceptPathInfo directive) instead of just turning safe-mode=off.  The reason is that safe mode sets global limitations on the entire server, which can then be turned on or left off for each specific virtual host.  This is the equivilent of blocking all connections on a firewall, and then opening up only the ones you want, which is a lot safer than leaving everything open globally, and assuming your programmers will never overlook a possible security hole.
Azureash
28-Jan-2003 08:34
Another way to hide your .php extensions is to use the Apache ForceType directive (which is often referred to as pretty URLs.)  Basically you force Apache to parse a file as PHP that matches the trailing directory name in your URL.

For example, place this directive in your Apache httpd.conf file:
<Location /home>
     ForceType application/x-httpd-php
</Location>

and create a php file name "home" in your doc root.  This file should not have a .php extension, and can be a php template file.  Combined with a function to strip out URL parameters, this can create a new templating system, which can effectively hide your file extensions.

In this example,
http://www.foo.com/home/bar.html

would actually use the home script we created, and then the "bar.html" could be used to specify content to include.
Kevin Vincent
23-Jan-2003 09:43
Just a thought but if you have changed the extensions that php interprets I would assume you've also changed header.php and footer.php files to the new extension.

EG:

index.php, somefile.php, header.php, footer.php...

Change the Apache directive so PHP interprets .kev files and rename your files:

index.kev, somefile.kev, header.kev, footer.kev

If you leave header and footer as PHP files then it won't understand how to interpret them.
sth at panix dot com
05-Aug-2002 03:45
The flipside to this is, if you're running a version of
PHP/Apache which is not known to have exploitable bugs (usually the latest stable version at the time), and an attacker sees this, they may give up before even trying. If they don't, they may continue to attempt their exploit(s).

It really depends on the type of attacker. The educated, security advisory reading attacker vs. script kiddie on the street.

If you're keeping up on patches, version exposition should not be a problem for you.
m1tk4 at hotmail dot com
23-Jul-2002 08:53
I usually do:

<code>
RewriteEngine on<br>
RewriteOptions inherit<br>
RewriteRule (.*)\.htm[l]?(.*) $1.php$2 [nocase]<br>
</code>

in .htaccess. You'll need mod_rewrite installed for this .
yasuo_ohgaki at yahoo dot com
26-Jan-2002 07:59
To hide PHP, you need following php.ini settings

expose_php=Off
display_errors=Off

and in httpd.conf

ServerSignature Off
(min works, but I prefer off)
istvan dot takacsNOSPAM at hungax dot com
31-Dec-2001 01:42
And use the
ServerTokens min
directive in your httpd.conf to hide installed PHP modules in apache.