ID: 49317
User updated by: jinger dot jiang at autodesk dot com
Reported By: jinger dot jiang at autodesk dot com
Status: Bogus
Bug Type: mcrypt related
Operating System: Vista, Windows2003
PHP Version: 5.2.10
New Comment:
It has been solved by remove the 'trim' function. Thanks.
Previous Comments:
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[2009-08-21 09:44:27] jinger dot jiang at autodesk dot com
Sorry for uncomplete code, the $key is not empty.
Here is the complete code:
$key="testlink";
function encrypt($plain_text) {
$plain_text = trim($plain_text);
$iv = substr(md5($key), 0,mcrypt_get_iv_size
(MCRYPT_CAST_256,MCRYPT_MODE_CFB));
$c_t = mcrypt_cfb (MCRYPT_CAST_256, $key, $plain_text,
MCRYPT_ENCRYPT, $iv);
$ret = trim(chop(base64_encode($c_t)));
return $ret;
}
function decrypt($c_t) {
$c_t = trim(chop(base64_decode($c_t)));
$iv = substr(md5($key), 0,mcrypt_get_iv_size
(MCRYPT_CAST_256,MCRYPT_MODE_CFB));
$p_t = mcrypt_cfb (MCRYPT_CAST_256, $key, $c_t, MCRYPT_DECRYPT,
$iv);
$ret = trim(chop($p_t));
return $ret;
}
------------------------------------------------------------------------
[2009-08-21 09:18:46] der...@php.net
Sorry, but your problem does not imply a bug in PHP itself. For a
list of more appropriate places to ask for help using PHP, please
visit http://www.php.net/support.php as this bug system is not the
appropriate forum for asking support questions. Due to the volume
of reports we can not explain in detail here why your report is not
a bug. The support channels will be able to provide an explanation
for you.
Thank you for your interest in PHP.
function decrypt($c_t) {
$c_t = trim(chop(base64_decode($c_t)));
That is broken, you might remove *required* \0 characters at the end of
the string. Where did you find this as example (because I've seen it
reported more often)?
------------------------------------------------------------------------
[2009-08-21 08:56:20] sjoerd-php at linuxonly dot nl
Thank you for your bug report.
In your example, the variable $key is not defined. Although the
behavior you report can still be considered a bug, it only seem to
happen when $key is empty. Supplying a correct key fixes your problem
and is useful from a security point of view.
------------------------------------------------------------------------
[2009-08-21 07:37:18] jinger dot jiang at autodesk dot com
Description:
------------
I use the function mcrypt_cfb(..,MCRYPT_ENCRYPT,.) to encrypt a
password valued 'Zx57Kl36', then I use mcrypt_cfb(..,MCRYPT_DECRYPT,..)
to decrypt the value, it changed to 'Zx57Kl3'.
I also have tried 'Zx57Kl32', 'Zx57Kl34' and 'Zx57Kl35', these value is
changed to 'Zx57Kl3' too after decrypt. But 'Zx57Kl30', 'Zx57Kl31' etc
are correct after decrypt.
Reproduce code:
---------------
My code:
//$plain_text can be 'Zx57Kl36' etc.
function encrypt($plain_text) {
$plain_text = trim($plain_text);
$iv = substr(md5($key), 0,mcrypt_get_iv_size
(MCRYPT_CAST_256,MCRYPT_MODE_CFB));
$c_t = mcrypt_cfb (MCRYPT_CAST_256, $key, $plain_text,
MCRYPT_ENCRYPT, $iv);
$ret = trim(chop(base64_encode($c_t)));
return $ret;
}
function decrypt($c_t) {
$c_t = trim(chop(base64_decode($c_t)));
$iv = substr(md5($key), 0,mcrypt_get_iv_size
(MCRYPT_CAST_256,MCRYPT_MODE_CFB));
$p_t = mcrypt_cfb (MCRYPT_CAST_256, $key, $c_t, MCRYPT_DECRYPT,
$iv);
$ret = trim(chop($p_t));
return $ret;
}
Expected result:
----------------
$ret=encrypt('Zx57Kl36');
$ret=decrypt($ret);
then $ret should be 'Zx57Kl36' but not 'Zx57Kl3'.
Actual result:
--------------
$ret=encrypt('Zx57Kl36');
$ret=decrypt($ret);
$ret equals to 'Zx57Kl3'. It should be 'Zx57Kl36'.
------------------------------------------------------------------------
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Edit this bug report at http://bugs.php.net/?id=49317&edit=1
