OpenSSL ext. improvements for authenticated cipher modes.

Hey

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.

--

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