zalgonoise/gasp repository overview

⁠gasp

⁠Google App Specific Password Validator

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.

⁠Generating an App Specific Password

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

⁠Mutt configuration file

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:[email protected]}"
set use_from = yes
set envelope_from = yes

set smtp_url = "smtps://${APP_USER:[email protected]}@smtp.gmail.com:465/"
set smtp_pass = "${APP_PASS:-secretpassword}"
set imap_user = "${APP_USER:[email protected]}"
set imap_pass = "${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

⁠Deploying the container and testing Gmail access

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