As with many exploits, remote and local file inclusions are only a problem at the end of the encoding. Of course, it takes a second person to have it. Now, this article will hopefully give you an idea of protecting your website and most importantly your code from a file iclusion exploit. I’ll give example codes in PHP format.
Obviously this should not be used. The $ page entry is not fully cleared. $ page input is directed directly to the damn web page, which is a big “NO”. Always remove any input passing through the browser. When the user clicks on “File” to visit “files.php” when he visits the web page, something will appear like this.
Now, if no one has cleared the input in the $ page variable, we can have it pointed to what we want. If hosted on a unix / linux server, we can display the password as configuration files for shaded or uncleaned variable input.
Probably where the $ page variable was originally placed on the page, we get the google.com homepage. This is where the codder
can be hurt. We all know what c99 (shell) can do, and if coders are careful, they may be included in the page, allowing users to surf through sensitive files and contacts at the appropriate time. Let’s look at something simpler that can happen on a web page. The faster and more dirty use of RFI exploitation is to your advantage. Now, create a file named “test.php” and put the following code in it and save it.
```
<? Php
passthru ($ _ GET [cmd]);
?>
```
Now this file is something you can use to your advantage to include it on a page with RFI exploitation. The passthru () command in PHP is very evil, and many hosts call it “out of service for security reasons”. With this code in test.php, we can send a request to the web page, including file inclusion exploit.
This unix machine will also extract the file / etc / passwd using the cat command. Now we know how to exploit RFI exploit, now we need to know how to hold it and make it impossible for anyone to execute the command, and how to include remote pages on your server. First, we can disable passthru (). But anything on your site can use it again (hopefully not). But this is the only thing you can do. I suggest cleaning the inputs as I said before. Now, instead of just passing variables directly to the page, we can use a few PHP-proposed structures within functions. Initially, chop () from perl was adapted to PHP, which removes whitespaces from an array. We can use it like this.
```
<ahref=index.php?page=file1.php> Files </a>
<? Php
$ page = chop ($ _ GET [page]);
include ($ page);
?>
```
There are many functions that can clear string. htmlspecialchars ()
htmlentities (), stripslashes () and more. In terms of confusion, I prefer to use my own functions. We can do a function in PHP that can clear everything for you, here I’ve prepared something easy and quick about this course for you.
```
<? Php
function cleanAll ($ input) {
$ input = strip_tags ($ input);
$ input = htmlspecialchars ($ input);
return ($ input);
}
?>
```
Now I hope you can see what’s going on inside this function, so you can add yours. I would suggest using the str_replace () function and there are a lot of other functions to clear them. Be considerate and stop the RFI & LFI exploit frenzy!
2. Include http://example.com/index.php?page=/proc/$PID/fd/$FD with $PID = PID of the process (can be bruteforced) and $FD the filedescriptor (can be bruteforced too)
