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Date: Sat, 31 Jan 2015 15:53:02 +0000
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Subject: OpenSSL ext. improvements for authenticated cipher modes.
From: leight@gmail.com (Leigh)

Hi list,

A couple of bug reports have highlighted the fact that our
openssl_encrypt and openssl_decrupt functions have no way of getting
or setting tags required for authenticated cipher modes (i.e. GCM,
CCM, OCB (not sure if this is available in OpenSSL)).

https://bugs.php.net/bug.php?id=68962
https://bugs.php.net/bug.php?id=67304

Further to this, we have no way of setting any associated data.

I think we absolutely must provide a method for users to be able to
use authenticated encryption, and would like some opinions on how much
flexibility we give users, and the best method for exposing this
functionality.

At the very basic end of the spectrum, we could have openssl_get_tag
and openssl_set_tag, or add an extra parameter to the end of
openssl_encrypt and openssl_decrypt (pass by ref for encrypt, like
preg $matches) this would cover the majority of use cases.

However I absolutely think that the associated data also needs to be
supported, and possibly the ability to change the tag length.

At this point we're starting to get into the territory where an
$options array is needed, or we add a lot of parameters to the end of
functions. I don't really think it's good to add up to 3 more params
to these functions.

What do you guys and girls think is the best way of tackling this?

Cheers,

Leigh.