gnus-cloud native GnuTLS AEAD support

gnus-cloud native GnuTLS AEAD support

[Ted Zlatanov]

I've pushed scratch/tzz/gnus-cloud-aead with a proposed implementation
to use the native GnuTLS AEAD symmetric ciphers for gnus-cloud storage.
While this specifically is for IMAP articles, the implementation can
encrypt/decrypt any unibyte text data using AEAD ciphers.

Reasons to implement it this way:

* no dependency on external tools
* low risk: optional storage method for non-critical data

TODO:

* move the new code out to a library, either in core or in the GNU ELPA
* document, factor some things out
* add a checker function to read-passwd for min/max etc. requirements

It worked well in my testing. Comments and suggestions welcome.

Ted

Re: gnus-cloud native GnuTLS AEAD support

[Eli Zaretskii]

> From: Ted Zlatanov <tzz@lifelogs.com>
> Date: Thu, 14 Dec 2017 00:15:14 -0500
> 
> I've pushed scratch/tzz/gnus-cloud-aead with a proposed implementation
> to use the native GnuTLS AEAD symmetric ciphers for gnus-cloud storage.
> While this specifically is for IMAP articles, the implementation can
> encrypt/decrypt any unibyte text data using AEAD ciphers.
> 
> Reasons to implement it this way:
> 
> * no dependency on external tools
> * low risk: optional storage method for non-critical data
> 
> TODO:
> 
> * move the new code out to a library, either in core or in the GNU ELPA
> * document, factor some things out
> * add a checker function to read-passwd for min/max etc. requirements
> 
> It worked well in my testing. Comments and suggestions welcome.

Did you test this code with non-ASCII text?  There are some tricky
shenanigans with multibyte text in the associated gnutls.c functions,
and you are using base64-encode-region, which will signal an error if
any non-ASCII characters are found in the region it is invoked on.  So
I'd suggest to have that tested.

And then there are the TODOs, of course.

Thanks.