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Date: Sat, 1 Mar 2014 20:50:15 -0500
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To: Nikita Popov <nikita.ppv@gmail.com>
Cc: PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Stricter error handling in mcrypt extension
From: theanomaly.is@gmail.com (Sherif Ramadan)

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On Sat, Mar 1, 2014 at 7:12 PM, Nikita Popov <nikita.ppv@gmail.com> wrote:

> Hi internals!
>
> I would like to add a number of additional error checks in
> php_mcrypt_do_crypt - which affects the mcrypt_encrypt, mcrypt_decrypt and
> mcrypt_{BLOCK_CHAINING_MODE} userland functions.
>
> The proposed changes are:
>  * Throw a warning and return bool(false) if the IV size is invalid. The
> old behavior was to throw a warning and use a NUL-byte IV.
>  * Throw a warning and return bool(false) if no IV was specified, but the
> block chaining mode requires an IV. The old behavior was to throw a warning
> and use a NUL-byte IV.
>  * Throw a warning and return bool(false) if the key size is invalid. The
> old behavior was to **silently** pad the string to the next valid key size
> with NUL bytes or, if the key is too long, to throw a warning and truncate
> it to the maximum valid key size.
>
> An implementation of these changes can be found in the PR
> https://github.com/php/php-src/pull/610.
>
> The reason why I'd like to make the mcrypt input handling stricter is to
> ensure that incorrectly implemented encryption will fail and fail
> violently. With the current lax input checking it is very easy to
> completely compromise confidentiality through simple mistakes - like using
> a password as the encryption key.
>
> Thanks,
> Nikita
>
> PS: I'm running this change by the list because stricter error handling is
> technically a BC break. Of course this change is targeting PHP 5.6 only.
>


I think that's a good idea given the number of people I've heard complaints
from about confusion around using mcrypt and the default NUL-byte IV. My
only concern is, isn't it a bit late in the game to push this to 5.6? Or is
that when we're at beta? Overall I think it's a smart change though despite
the BC.

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