matrix-docker-ansible-deploy/docs/configuring-playbook-shared-secret-auth.md

Setting up the Shared Secret Auth password provider module (optional, advanced)

The playbook can install and configure matrix-synapse-shared-secret-auth for you.

See that project's documentation to learn what it does and why it might be useful to you.

If you decide that you'd like to let this playbook install it for you, you need some configuration (inventory/host_vars/matrix.<your-domain>/vars.yml) like this:

matrix_synapse_ext_password_provider_shared_secret_auth_enabled: true
matrix_synapse_ext_password_provider_shared_secret_auth_shared_secret: YOUR_SHARED_SECRET_GOES_HERE

You can generate a strong shared secret with a command like this: pwgen -s 64 1

Authenticating only using a password provider

If you wish for users to authenticate only against configured password providers (like this one), without consulting Synapse's local database, feel free to disable it:

matrix_synapse_password_config_localdb_enabled: false