[horde] Setup OAuth2 with Horde-Imp

[Louis-Philippe Allard]

Hello,

I am trying to setup Protonmail and their bridge to replace GMail as  
Horde's email backend server on my selfhosted VPS.  However its  
looking more complicated than expected (sigh).

In the meantime, I have until May 30th to setup OAuth2 to be able to  
continue using Gmail. Thanks Google...

However, I cannot find any instructions on how to do so, and the  
maillist is very quiet these days.

The way my system is setup is that Gmail's credentials are used by IMP  
for Horde's authentication (hordeauth => true in  
imp/backends.local.php).

GMail's IMAP server is setup also in imp/backends.local.php  
(imap.gmail.com:993) and to send emails, Gmail's SMTP server is setup  
under Horde's config > Mailer section (smtp.gmail.com:587).

Just to be sure I understand the "mechanics" involved here, can  
someone just confirm this statement:  On my setup, IMP passes the  
credentials received at the login page to GMail's server which accepts  
them.  IMP receiving a successful reply from GMail, it lets the user  
enter (authenticate) into Horde.  Email sync'ing (folder structure,  
receiving emails, etc) is done via the IMP's backends.local.php (IMAP  
section), and sending email from this VPS is accomplished via the  
Mailer section of Horde using GMail's SMTP server.

Everything else in Horde (calendar, contacts, task lists, notes,  
tickets, etc) has never been setup to be stored remotely.  It is  
stored in Horde's MYSQL database.

If I lose connectivity to GMail, I CANNOT LOGIN to Horde.  This is a  
major issue.

I need IMP to handle OAuth2 to be able to use GMail's IMAP.

I need Horde to handle OAuth2 to be able to use GMail's SMTP.

Question 1:  How can I setup a local authentication that would NOT  
rely on external servers?  This VPS is behind a strong FW so I am OK  
with standard USR:PSW combination.
Question 2:  Is it possible to setup OAuth2 to be able to use GMail's  
IMAP and SMTP servers?

Hopefully the maillist is still alive and well  and someone can guide/help me!

Thank you !!
  Louis-Philippe Allard
lp.allard.1 at gmail.com
Sent using Horde Groupware on GNU/Linux