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Date: Sat, 31 Jan 2015 09:13:52 -0700
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To: Leigh <leight@gmail.com>
Cc: PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a11332018db40ee050df50103
Subject: Re: [PHP-DEV] OpenSSL ext. improvements for authenticated cipher modes.
From: jason.gerfen@gmail.com (Jason Gerfen)

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On Sat, Jan 31, 2015 at 8:53 AM, Leigh <leight@gmail.com> wrote:

> 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=3D68962
> https://bugs.php.net/bug.php?id=3D67304
>
> 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.
>
>
=E2=80=8BI think exposing this to the user will only cause confusion and al=
low
users to implement mistakes to the algorithm and mode usage.=E2=80=8B



> 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.
>
> --
> PHP Internals - PHP Runtime Development Mailing List
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>
>
According to the OpenSSL documentation regarding encryption/decryption
using CCM, GCM & OCB modes for authenticated usage would require the
additions of the following constants:

EVP_CTRL_OCB_SET_TAGLEN
EVP_CTRL_SET_IVLEN
EVP_CTRL_GET_TAG
EVP_CTRL_CCM_SET_L
EVP_CTRL_CCM_SET_IVLEN
EVP_aes_256_gcm()
EVP_aes_128_gcm()
=E2=80=8B

=E2=80=8BThat coupled with the use of the =E2=80=8B

EVP_CIPHER_CTX_ctrl()

=E2=80=8Bshould provide the needed functionality =E2=80=8Bas described in
http://wiki.openssl.org/index.php/EVP_Authenticated_Encryption_and_Decrypti=
on
the documentation for using the EVP authenticated modes for
encryption/decryption.

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