[Mailman-Developers] opportunistically encrypted mailman lists with Autocrypt

[Jan Jancar]

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.

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

> 
> - 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

Cheers,
-- 
Jan
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