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Date: Sun, 1 Feb 2015 17:57:04 +0000
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To: Leigh <leight@gmail.com>
Cc: Jason Gerfen <jason.gerfen@gmail.com>, PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=20cf302667fcc59e9f050e0a90a0
Subject: Re: [PHP-DEV] OpenSSL ext. improvements for authenticated cipher modes.
From: bukka@php.net (Jakub Zelenka)

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Hey

On Sat, Jan 31, 2015 at 4:21 PM, Leigh <leight@gmail.com> wrote:

> On 31 January 2015 at 16:13, Jason Gerfen <jason.gerfen@gmail.com> wrote:
> > On Sat, Jan 31, 2015 at 8:53 AM, Leigh <leight@gmail.com> wrote:
> >> 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.
> >>
> >
> > I think exposing this to the user will only cause confusion and allow
> users
> > to implement mistakes to the algorithm and mode usage.
> >
>
> set/get tag functions are alto my least favourite options.
>
> >
> > 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()
> >
> > That coupled with the use of the
> >
> > EVP_CIPHER_CTX_ctrl()
> >
> > should provide the needed functionality as described in
> >
> http://wiki.openssl.org/index.php/EVP_Authenticated_Encryption_and_Decryption
> > the documentation for using the EVP authenticated modes for
> > encryption/decryption.
> >
>
> Thanks, I have done some cursory research into how it should be
> implemented, but I wanted this discussion to be about how we should
> present the functionality to the user. Implementation details can come
> second once we have a consensus on what is/isn't too much, and what
> method we should use to allow this functionality to be used.
>
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> PHP Internals - PHP Runtime Development Mailing List
> To unsubscribe, visit: http://www.php.net/unsub.php
>
>

Hey,

I have already implemented all of this in crypto ext (
https://github.com/bukka/php-crypto ) and also added support for streams
(e.g.
https://github.com/bukka/php-crypto/blob/master/tests/stream_filters_cipher_gcm_dec_read.phpt
)
and objective context. However crypto is and probably quite some time will
be in the dev stability. I have put that work on hold for some time (due to
php 7 api changes) but plan to resume it soon.

Anyway this is a bit different as it is a bit more complex and bit too much
for openssl ext. The thing is that the symmetric cypto functions are just
openssl_encrypt and openssl_decrypt and they don't have any context. I'm
not sure how the proposed openssl_*et_tag would work without context. The
options array makes definitely more sense to me. It's basically what I used
for stream context ( some doc can be found here:
https://github.com/bukka/php-crypto/issues/8 ). The only problem is how to
get the resulted tag. I used stream meta array for that in crypto streams.
If we don't want to break BC, then we would probably need another ref param
openssl_encrypt. Something like:

string openssl_encrypt ( string $data , string $method , string $password
[, mixed $options = NULL [, string $iv = "" [, string &$tag = NULL ] ] ] )

The options would be overloaded for BC (if it's int, then the same as
before or you can use array for further options as AAD...).

What's you thoughts?

Btw. I think I could do or help with the implementation if there is an
interest in that feature in PHP 7 . It would be sort of port from crypto
where I also have bunch of test for that (supported are just ccm and gcm).

Cheers

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