A simple and lightweight Docker image for validating Google App-Specific Passwords via Gmail and Mutt.

Uses simple authentication (over TLS1.3) to access a Gmail inbox from a headless environment (using the mutt email client for Linux), using Google's required App Passwords method.

This simple system allows access to certain service's API's to many types of environment in a secure manner - without providing your real password.

As such, Google allows you to provision your less secure applications with authentication methods for them to work, and for your account to be safe.

Covered by Google Support

1. Head over to your Google Account.
2. On the left-hand drawer, open Security
3. Under the section Signing in with Google, open App Passwords
4. Select the app you'd like to generate a password, for this we need to use Gmail
5. For the device select Other and provide it a name, such as mutt
6. Copy the resulting 16-character-long string to a safe place.
   • Google will not reveal this password again.
   • You will need to use it as an environment variable when running this container

By default, the Mutt configuration file is adequate to access Gmail (as of March 2020). This file is created by the entrypoint.sh script, and is placed under /data/muttrc.

The default configuration file is populated with the following environment variables, defined when you start the container:

• APP_USER: The email address for you Google Account
• APP_PASS: The App Password generated in your Google Account to access Gmail

And is dumped with cat via heredocs into /data/muttrc:

   cat << EOF >> muttrc
set from = "${APP_USER:-user@example.com}"
set use_from = yes
set envelope_from = yes

set smtp_url = "smtps://${APP_USER:-user@example.com}@smtp.gmail.com:465/"
set smtp_pass = "${APP_PASS:-secretpassword}"
set imap_user = "${APP_USER:-user@example.com}"
set imap_pass = "${APP_PASS:-secretpassword}"
set folder = "imaps://imap.gmail.com:993"
set spoolfile = "+INBOX"
set ssl_force_tls = yes
EOF

Mutt is, in turn, ran with this configuration file:

mutt -F /data/muttrc

Simply load the variables to your environment (or define them when running the container):

docker run --rm -ti \
-e APP_USER=${APP_USER} \
-e APP_PASS=${APP_PASS} \
zalgonoise/gasp

To access your inbox, add anything as a parameter, after the repo/container reference:

docker run --rm -ti \
-e APP_USER=${APP_USER} \
-e APP_PASS=${APP_PASS} \
zalgonoise/gasp \
mail

Or if you'd like to run a custom .muttrc file, you can load it into the container as /data/muttrc, so it is loaded instead of the default one. Be sure to inclue your password in your .rc file in both SMTP/IMAP fields:

docker run --rm -ti \
-v /path/to/.muttrc:/data/muttrc \
-e APP_USER=${APP_USER} \
zalgonoise/gasp

~ ZalgoNoise ~ 2020