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How to hide/encrypt http arguments in php?

Posted on 2008-06-17
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Last Modified: 2008-06-17
Hi

lets consider we are passing one argument like below

http://thegurbani.com/audio/index.php?file=http://www.thegurbani.com/audio/audio/kirtan/4.mp3

argument : "file=http://www.thegurbani.com/audio/audio/kirtan/4.mp3"

I want you to encrypt this argument and then at target location decrypt it.

Plz note I need this argument in normal form becoz I am catching it at target location into a php_variable.
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Question by:theredcode
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6 Comments
 
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Expert Comment

by:Roonaan
ID: 21804633
Do you have access to a database? Then you could just use file=123 or file=456 based on an primairy auto increment key.
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Expert Comment

by:rdivilbiss
ID: 21804636
Use the AES encrypt function, which is part of the mcrypt library.
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Author Comment

by:theredcode
ID: 21804775
well no database, simple argument passing

can u provide code for encrypting and decrypting.
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Expert Comment

by:rdivilbiss
ID: 21804805
Yes, a moment please.
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Accepted Solution

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rdivilbiss earned 500 total points
ID: 21805440

<?PHP
 

$iv = mcrypt_create_iv(16, MCRYPT_RAND);

$key = substr($fieldHash,0,mcrypt_get_key_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB));
 

// need to use the same key and iv to decode so save to session	

$_SESSION['key']=$key;

$_SESSION['iv']=$iv;
 

//have to pad your string to be at least 64 chars.  Can be longer.

$text = str_pad("http://www.thegurbani.com/audio/audio/kirtan/4.mp3",64);
 

//Need to Base64 encode the encrypted string or it won't pass as a URL.

$param = base64_encode(mcrypt_encrypt(MCRYPT_RIJNDAEL_128, $key, $text, MCRYPT_MODE_ECB, $iv));
 

//  how to decrypt...using saved values and base64 decrypt

$href = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $_SESSION['key'], base64_decode($param), MCRYPT_MODE_ECB, $_SESSION['iv']);
 
 

?>

<html>
 

<head>

<meta http-equiv="Content-Language" content="en-us">

<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">

<title>The link</title>

</head>
 

<body>

<p>Link with encoded param: <a href="aeslink2.php?p=<?=$param?>">The link</a></p>

<p>Decoded Param: <?=$href?></p>

</body>
 

</html>

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Expert Comment

by:rdivilbiss
ID: 21808637
That code isn't good for your purposes.  See below for better.
<?PHP

session_start();

$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);

$iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);

// save these for decoding

$_SESSION["iv"] = $iv;
 

$key = "This is a very secret key";

$_SESSION["key"] = $key;
 

//$text = "Who framed Roger Rabbit";

$text = addcslashes("http://www.thegurbani.com/audio/4.mp3","\0..\37");
 

// we will pass the length...nothing given away with that.

$len = strlen($text);
 

$crypttext = urlencode(mcrypt_encrypt(MCRYPT_RIJNDAEL_256, $key, $text, MCRYPT_MODE_ECB, $iv));

?>

<html>
 

<head>

<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">

<title>Send Encrypted URL Parameter</title>

</head>
 

<body>

<p>Hover over the URL to see what is passed.</p>

<a href="page2.php?file=<?=$crypttext?>&len=<?=$len?>">Pass It</a>

</body>
 

</html>
 
 
 

<?PHP

// page2.php

session_start();

$iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256, MCRYPT_MODE_ECB);
 

// We need the originals

$iv = $_SESSION["iv"];

$key = $_SESSION["key"];
 

// get the encrypted filename

$param=$_GET["file"];
 

// get its length

$len=$_GET["len"];
 

// decode, decrypt and perform substr to get the original file name

$filex = substr(mcrypt_decrypt(MCRYPT_RIJNDAEL_256, $key, urldecode($param), MCRYPT_MODE_ECB, $iv),0,$len);

?>
 

<html>
 

<head>

<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">

<title>Receive Encrypted File Name</title>

</head>
 

<body>

<?=$filex?>

</body>
 

</html>

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