#48730 [Opn->Bgs]: Problems to decrypt an encrypted string with RIJNDAEL_256 and ECB_MODE

 ID:               48730
 Updated by:       [email protected]
 Reported By:      johanna at neiatec dot com
-Status:           Open
+Status:           Bogus
 Bug Type:         mcrypt related
 Operating System: OpenBSD and linuxes
 PHP Version:      5.2.10
 New Comment:

Thank you for taking the time to write to us, but this is not
a bug. Please double-check the documentation available at
http://www.php.net/manual/ and the instructions on how to report
a bug at http://bugs.php.net/how-to-report.php

You can not trim the encoded string, as there might be required
trailing 0's or something like that. Remove the trim from the following
line and it works:

$enc = base64_encode(trim($enc));



Previous Comments:
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[2009-06-30 05:15:28] johanna at neiatec dot com

Just to make it clear, this problem is with MCRYPT_RIJNDAEL_128 and
MCRYPT_RIJNDAEL_256. The example I posted is with 128 but if changed to
256 it doesn't work either.

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[2009-06-30 05:01:50] johanna at neiatec dot com

Description:
------------
RIJNDAEL_256 with ECB_MODE does not work everytime properly, here is
the example of a string that is encrypted and then cannot get decrypted
to the original.

Reproduce code:
---------------
$string =
"numero_documento_funcionario:=:31194443#&#seccional:=:Principal#&#correo_funcionario:=:[email protected]#&#fecha_solicitud:=:2009-04-30
00:00:00#&#numero_radicacion:=:000001#&#numero_camara:=:36###198";
echo "To encrypt: <br /><br />\n";
$key = "9c08eb33218aa11eb8f1423f85d5f554";
echo $string."<br /><br />\nEncrypted: <br /><br />\n";
$encrypted = cifrar($string, $key);
echo $encrypted."<br /><br />\nDecrypted ??: <br /><br />\n";
echo descifrar($encrypted, $key)."<br /><br /><br /><br />\n";

    function cifrar($message, $key){
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128,
MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        $enc=mcrypt_encrypt(MCRYPT_RIJNDAEL_128,$key, $message,
MCRYPT_MODE_ECB, $iv);
        $enc = base64_encode(trim($enc));
        return $enc;
    }
    function descifrar($enc, $key){
        $enc = base64_decode(trim($enc));
        $iv_size = mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128,
MCRYPT_MODE_ECB);
        $iv = mcrypt_create_iv($iv_size, MCRYPT_RAND);
        return trim(mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $key, $enc,
MCRYPT_MODE_ECB, $iv));
    } 
    

Expected result:
----------------
I expect the decrypted string to be just the same as the original
string.

Actual result:
--------------
The last characters are not decrypted properly. And this just happens
with this very string, if you change any character, add or take away any
character, it works. But it is a flaw as strings as this one are
generated by my application and it fails at times.


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