[Mailman-Developers] opportunistically encrypted mailman lists with Autocrypt

[holger]

Hi Jan,

On Wed, Jan 31, 2018 at 15:28 +0100, Jan Jancar wrote:
> Hi all!
> 
> On 01/25/2018 12:21 PM, holger krekel wrote:
> > Indeed, i guess a plugin should get us >90% there.  Here are my
> > current technical considerations in a quick list: 
> > 
> > - Autocrypt L1 specifies how to generate an Autocrypt key, transfer and 
> >   parse public keys and settings through headers of regular e-mails.  
> > 
> > - Mailman is to create and maintain a per-list Autocrypt account 
> >   (managed through "muacrypt") which keeps track of 
> >   subscriber's encryption settings by parsing incoming mail messages. 
> >   muacrypt in turn uses "gpg" or "gpg2" and would maintain 
> >   keyring/account data on a per-list basis.  muacrypt also implements
> >   mime-encryption and decryption and needs to intercept incoming/outgoing
> >   mails.  Can a plugin modify outgoing messages on a per-recipient basis? 
> 
> Yes a plugin can do that, although it has to go through some hoops as
> when I was making the delivery part of the plugin support I didn't want
> to change Mailman's delivery mechanisms too much, which means a plugin
> doing this will have some code duplication/boilerplate. As there are
> only 2 plugins currently([mailman-pgp] and [mailman-rest-events]), I
> think the plugin API could still evolve.

sounds good!
 
> If you would like to use a Python OpenPGP implementation you could look
> at [PGPy] and how I used it in mailman-pgp.

It's under consideration here: https://github.com/hpk42/muacrypt/issues/32
Are your experiences with pgpy indicating it's compatible with
enigmail and k9-mail? (see the questions on that issue)

> > - No special interface is needed on the mailing list web page
> >   maybe except from enabling/disabling the plugin/support. 
> 
> Plugin configuration is done through the Mailman configuration and those
> are read-only through the REST interface. However a plugin might supply
> it's own REST endpoints for example for per-list setup/configuration.

I guess read-only REST would allow for a command line interface for 
debugging or other low-level configuration wrt to autocrypt key
status for peers.  Can a plugin add per-list configuration 
options (enable/disable, maybe a choice between 2-3 policies?)

> > - With the current Autocrypt specification, a mailman list 
> >   will need to have the DMARC-mitigation "replace-from" action enabled
> >   to a) allow the list's public key to be added to outgoing mails 
> >   in an Autocrypt compliant way b) send properly signed and encrypted mails
> >   to those subscribers which are Autocrypt-capable and have a "mutual"
> >   prefer-encrypt settings (see Autocrypt spec for details "prefer-encrypt").
> >   If we get this to work nicely i think we can see about advancing the
> >   Autocrypt spec to support other ML modes (i.e. not replacing From).
> > 
> > - For a mixed set of subscribers (some with and some without Autocrypt
> >   support) mailman will send out encrypted and unencrypted mails
> >   respectively.  The status of the group might be added to a group's
> >   footer so that subscribers know about the group's security status
> >   (and get incentivized to upgrade their e-mail program).
> > 
> > Does that sound sensible? And achievable through a plugin, leaving the
> > core (largely) untouched? 
> 
> I definitely think so.
> 
> [mailman-pgp]: https://gitlab.com/J08nY/mailman-pgp
> [mailman-rest-events]: https://gitlab.com/J08nY/mailman-rest-events
> [PGPy]: https://github.com/SecurityInnovation/PGPy

thanks a bunch for your feedback and links.

holger
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