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Setting up Matrix Authentication Service (optional)

This playbook can install and configure Matrix Authentication Service (MAS) - a service operating alongside your existing Synapse homeserver and providing better authentication, session management and permissions in Matrix.

Matrix Authentication Service is an implementation of MSC3861: Next-generation auth for Matrix, based on OAuth 2.0/OIDC and still work in progress, tracked at the areweoidcyet.com website.

Before going through with starting to use Matrix Authentication Service, make sure to read:

If you've already been using Synapse and have user accounts in its database, you can migrate to Matrix Authentication Service.

Reasons to use Matrix Authentication Service

You may be wondering whether you should make the switch to Matrix Authentication Service (MAS) or keep using your existing authentication flow via Synapse (password-based or OIDC-enabled).

Matrix Authentication Service is still an experimental service and not a default for this Ansible playbook.

The Expectations section contains a list of what works and what doesn't (some services don't work with MAS yet), as well as the relative irreversability of the migration process.

Below, we'll try to highlight some potential reasons for switching to Matrix Authentication Service:

  • To use SSO in Element X. The old Synapse OIDC login flow is only supported in old Element clients and will not be supported in Element X. Element X will only support the new SSO-based login flow provided by MAS, so if you want to use SSO with Element X, you will need to switch to MAS.

  • To help drive adoption of the "Next-generation auth for Matrix" by switching to what's ultimately coming anyway

  • To help discover (and potentially fix) MAS integration issues with this Ansible playbook

  • To help discover (and potentially fix) MAS integration issues with various other Matrix components (bridges, bots, clients, etc.)

  • To reap some of the security benefits that Matrix Authentication Service offers, as outlined in the Better authentication, session management and permissions in Matrix article.

Prerequisites

Expectations

This section details what you can expect when switching to the Matrix Authentication Service (MAS).

  • ❌ Synapse password providers will need to be disabled. You can no longer use shared-secret-auth, rest-auth, LDAP auth, etc. When the authentication flow is handled by MAS (not by Synapse anymore), it doesn't make sense to extend the Synapse authentication flow with additional modules. Many bridges used to rely on shared-secret-auth for doing double-puppeting (impersonating other users), but most (at least the mautrix bridges) nowadays use Appservice Double Puppet as a better alternative. Older/maintained bridges may still rely on shared-secret-auth, as do other services like matrix-corporal.

  • ❌ Certain tools like synapse-admin do not have full compatibility with MAS yet. synapse-admin already supports login with access token, browsing users (which Synapse will internally fetch from MAS) and updating user avatars. However, editing users (passwords, etc.) now needs to happen directly against MAS using the MAS Admin API, which synapse-admin cannot interact with yet.

  • ❌ Some services experience issues when authenticating via MAS:

  • ❌ Encrypted appservices do not work yet (related to MSC4190 and PR 17705 for Synapse), so all bridges/bots that rely on encryption will fail to start (see this issue for Hookshot). You can use these bridges/bots only if you keep end-to-bridge encryption disabled (which is the default setting).

  • ⚠️ You will need to have email sending configured (see Adjusting email-sending settings), because Matrix Authentication Service still insists on having a verified email address for each user going through the new SSO-based login flow. It's also possible to work around email deliverability issues if your email configuration is not working.

  • ⚠️ Migrating an existing Synapse homeserver to Matrix Authentication Service is possible, but requires some playbook-assisted manual work. Migration is reversible with no or minor issues if done quickly enough, but as users start logging in (creating new login sessions) via the new MAS setup, disabling MAS and reverting back to the Synapse user database will cause these new sessions to break.

  • ⚠️ Migrating an existing Synapse homeserver to Matrix Authentication Service does not currently seem to preserve the "admin" flag for users (as found in the Synapse database). All users are imported as non-admin - see element-hq/matrix-authentication-service#3440. You may need update the Matrix Authentication Service's database manually and adjust the can_request_admin column in the users table to true for users that need to be administrators (e.g. UPDATE users SET can_request_admin = true WHERE username = 'someone';)

  • ⚠️ Delegating user authentication to MAS causes your Synapse server to be completely dependant on one more service for its operations. MAS is quick & lightweight and should be stable enough already, but this is something to keep in mind when making the switch.

  • ⚠️ If you've got OIDC configured in Synapse, you will need to migrate your OIDC configuration to MAS by adding an Upstream OAuth2 configuration.

  • ⚠️ A compatibility layer is installed - all /_matrix/client/*/login (etc.) requests will be routed to MAS instead of going to the homeserver. This is done both publicly (e.g. https://matrix.example.com/_matrix/client/*/login) and on the internal Traefik entrypoint (e.g. https://matrix-traefik:8008/_matrix/client/*/login) which helps addon services reach the homeserver's Client-Server API. You typically don't need to do anything to make this work, but it's good to be aware of it, especially if you have a custom webserver setup.

  • ✅ Your existing login sessions will continue to work (you won't get logged out). Migration will require a bit of manual work and minutes of downtime, but it's not too bad.

  • ✅ Various clients (Cinny, Element Web, Element X, FluffyChat) will be able to use the new SSO-based login flow provided by Matrix Authentication Service

  • ✅ The old login flow (called m.login.password) will still continue to work, so clients (old Element Web, etc.) and bridges/bots that don't support the new OIDC-based login flow will still work. Going through the old login flow does not require users to have a verified email address, as is the case for the new SSO-based login flow.

  • ✅ Registering users via the playbook's register-user tag remains unchanged. The playbook automatically does the right thing regardless of homeserver implementation (Synapse, Dendrite, etc.) and whether MAS is enabled or not. When MAS is enabled, the playbook will forward user-registration requests to MAS. Registering users via the command-line is no longer done via the /matrix/synapse/bin/register script, but via /matrix/matrix-authentication-service/bin/register-user.

  • ✅ Users that are prepared by the playbook (for bots, bridges, etc.) will continue to be registered automatically as expected. The playbook automatically does the right thing regardless of homeserver implementation (Synapse, Dendrite, etc.) and whether MAS is enabled or not. When MAS is enabled, the playbook will forward user-registration requests to MAS.

Installation flows

New homeserver

For new homeservers (which don't have any users in their Synapse database yet), follow the Adjusting the playbook configuration instructions and then proceed with Installing.

Existing homeserver

Other homeserver implementations (Dendrite, Conduit, etc.) do not support integrating wtih Matrix Authentication Service yet.

For existing Synapse homeservers:

Adjusting the playbook configuration

To enable Matrix Authentication Service, add the following configuration to your inventory/host_vars/matrix.example.com/vars.yml file:

matrix_authentication_service_enabled: true

# Generate this encryption secret with: `openssl rand -hex 32`
matrix_authentication_service_config_secrets_encryption: ''

# When migrating an existing homeserver to Matrix Authentication Service, uncomment the line below.
# Learn more about the migration process in the "Marking an existing homeserver for migration" section below.
# For brand-new installations which start directly on MAS, this line can be removed.
# matrix_authentication_service_migration_in_progress: true

In the sub-sections that follow, we'll cover some additional configuration options that you may wish to adjust.

There are many other configuration options available. Consult the defaults/main.yml file in the matrix-authentication-service role to discover them.

Adjusting the Matrix Authentication Service URL

By default, this playbook installs the Matrix Authentication Service on the matrix. subdomain, at the /auth path (https://matrix.example.com/auth). This makes it easy to install it, because it doesn't require additional DNS records to be set up. If that's okay, you can skip this section.

By tweaking the matrix_authentication_service_hostname and matrix_authentication_service_path_prefix variables, you can easily make the service available at a different hostname and/or path than the default one.

Example additional configuration for your inventory/host_vars/matrix.example.com/vars.yml file:

# Change the default hostname and path prefix
matrix_authentication_service_hostname: auth.example.com
matrix_authentication_service_path_prefix: /

Marking an existing homeserver for migration

The configuration above instructs existing users wishing to migrate to add matrix_authentication_service_migration_in_progress: true to their configuration.

This is done temporarily. The migration steps are described in more detail in the Migrating an existing Synapse homeserver to Matrix Authentication Service section below.

Upstream OAuth2 configuration

To make Matrix Authentication Service delegate to an existing upstream OAuth 2.0/OIDC provider, you can use its upstream_oauth2.providers setting.

The playbook exposes a matrix_authentication_service_config_upstream_oauth2_providers variable for controlling this setting.

Click to expand the example configuration:

Example additional configuration for your inventory/host_vars/matrix.example.com/vars.yml file:

matrix_authentication_service_config_upstream_oauth2_providers:
  - # A unique identifier for the provider
    # Must be a valid ULID
    id: 01HFVBY12TMNTYTBV8W921M5FA
    # The issuer URL, which will be used to discover the provider's configuration.
    # If discovery is enabled, this *must* exactly match the `issuer` field
    # advertised in `<issuer>/.well-known/openid-configuration`.
    issuer: https://example.com/
    # A human-readable name for the provider,
    # which will be displayed on the login page
    #human_name: Example
    # A brand identifier for the provider, which will be used to display a logo
    # on the login page. Values supported by the default template are:
    #  - `apple`
    #  - `google`
    #  - `facebook`
    #  - `github`
    #  - `gitlab`
    #  - `twitter`
    #brand_name: google
    # The client ID to use to authenticate to the provider
    client_id: mas-fb3f0c09c4c23de4
    # The client secret to use to authenticate to the provider
    # This is only used by the `client_secret_post`, `client_secret_basic`
    # and `client_secret_jwk` authentication methods
    #client_secret: f4f6bb68a0269264877e9cb23b1856ab
    # Which authentication method to use to authenticate to the provider
    # Supported methods are:
    #   - `none`
    #   - `client_secret_basic`
    #   - `client_secret_post`
    #   - `client_secret_jwt`
    #   - `private_key_jwt` (using the keys defined in the `secrets.keys` section)
    token_endpoint_auth_method: client_secret_post
    # Which signing algorithm to use to sign the authentication request when using
    # the `private_key_jwt` or the `client_secret_jwt` authentication methods
    #token_endpoint_auth_signing_alg: RS256
    # The scopes to request from the provider
    # In most cases, it should always include `openid` scope
    scope: "openid email profile"
    # How the provider configuration and endpoints should be discovered
    # Possible values are:
    #  - `oidc`: discover the provider through OIDC discovery,
    #     with strict metadata validation (default)
    #  - `insecure`: discover through OIDC discovery, but skip metadata validation
    #  - `disabled`: don't discover the provider and use the endpoints below
    #discovery_mode: oidc
    # Whether PKCE should be used during the authorization code flow.
    # Possible values are:
    #  - `auto`: use PKCE if the provider supports it (default)
    #    Determined through discovery, and disabled if discovery is disabled
    #  - `always`: always use PKCE (with the S256 method)
    #  - `never`: never use PKCE
    #pkce_method: auto
    # The provider authorization endpoint
    # This takes precedence over the discovery mechanism
    #authorization_endpoint: https://example.com/oauth2/authorize
    # The provider token endpoint
    # This takes precedence over the discovery mechanism
    #token_endpoint: https://example.com/oauth2/token
    # The provider JWKS URI
    # This takes precedence over the discovery mechanism
    #jwks_uri: https://example.com/oauth2/keys
    # How user attributes should be mapped
    #
    # Most of those attributes have two main properties:
    #   - `action`: what to do with the attribute. Possible values are:
    #      - `ignore`: ignore the attribute
    #      - `suggest`: suggest the attribute to the user, but let them opt out
    #      - `force`: always import the attribute, and don't fail if it's missing
    #      - `require`: always import the attribute, and fail if it's missing
    #   - `template`: a Jinja2 template used to generate the value. In this template,
    #      the `user` variable is available, which contains the user's attributes
    #      retrieved from the `id_token` given by the upstream provider.
    #
    # Each attribute has a default template which follows the well-known OIDC claims.
    #
    claims_imports:
      # The subject is an internal identifier used to link the
      # user's provider identity to local accounts.
      # By default it uses the `sub` claim as per the OIDC spec,
      # which should fit most use cases.
      subject:
        #template: "{% raw %}{{ user.sub }}{% endraw %}"
      # The localpart is the local part of the user's Matrix ID.
      # For example, on the `example.com` server, if the localpart is `alice`,
      #  the user's Matrix ID will be `@alice:example.com`.
      localpart:
        #action: force
        #template: "{% raw %}{{ user.preferred_username }}{% endraw %}"
      # The display name is the user's display name.
      displayname:
        #action: suggest
        #template: "{% raw %}{{ user.name }}{% endraw %}"
      # An email address to import.
      email:
        #action: suggest
        #template: "{% raw %}{{ user.email }}{% endraw %}"
        # Whether the email address must be marked as verified.
        # Possible values are:
        #  - `import`: mark the email address as verified if the upstream provider
        #     has marked it as verified, using the `email_verified` claim.
        #     This is the default.
        #   - `always`: mark the email address as verified
        #   - `never`: mark the email address as not verified
        #set_email_verification: import

💡 Refer to the upstream_oauth2.providers setting for the most up-to-date schema and example for providers. The value shown above here may be out of date.

⚠️ The syntax for existing OIDC providers configured in Synapse is slightly different, so you will need to adjust your configuration when switching from Synapse OIDC to MAS upstream OAuth2.

⚠️ When migrating an existing homeserver which contains OIDC-sourced users, you will need to:

Adjusting DNS records

If you've changed the default hostname, you may need to adjust your DNS records to point the Matrix Authentication Service domain to the Matrix server.

See Configuring DNS for details about DNS changes.

If you've decided to use the default hostname, you won't need to do any extra DNS configuration.

Installing

Now that you've adjusted the playbook configuration and your DNS records, you can run the playbook with playbook tags as below:

ansible-playbook -i inventory/hosts setup.yml --tags=setup-all,start

Notes:

  • The shortcut commands with the just program are also available: just install-all or just setup-all

    just install-all is useful for maintaining your setup quickly (2x-5x faster than just setup-all) when its components remain unchanged. If you adjust your vars.yml to remove other components, you'd need to run just setup-all, or these components will still remain installed. Note these shortcuts run the ensure-matrix-users-created tag too.

  • If you're in the process of migrating an existing Synapse homeserver to MAS, you should now follow the rest of the steps in the Migrating an existing Synapse homeserver to Matrix Authentication Service guide.

💡 After installation, you should verify that Matrix Authentication Service is installed correctly.

Migrating an existing Synapse homeserver to Matrix Authentication Service

Our migration guide is loosely based on the upstream Migrating an existing homeserver guide.

Migration is done via a tool called syn2mas, which the playbook could run for you (in a container).

The installation + migration steps are like this:

  1. Adjust your configuration to disable the integration between the homeserver and MAS. This is done by uncommenting the matrix_authentication_service_migration_in_progress: true line.

  2. Perform the initial installation. At this point:

    • Matrix Authentication Service will be installed. Its database will be empty, so it cannot validate existing access tokens or authentication users yet.

    • The homeserver will still continue to use its local database for validating existing access tokens.

    • Various compatibility layer URLs are not yet installed. New login sessions will still be forwarded to the homeserver, which is capable of completing them.

    • The matrix-user-creator role would be suppressed, so that it doesn't automatically attempt to create users (for bots, etc.) in the MAS database. These user accounts likely already exist in Synapse's user database and could be migrated over (via syn2mas, as per the steps below), so creating them in the MAS database would have been unnecessary and potentially problematic (conflicts during the syn2mas migration).

  3. Consider taking a full backup of your Postgres database. This is done just in case. The syn2mas migration tool does not delete any data, so it should be possible to revert to your previous setup by merely disabling MAS and re-running the playbook (no need to restore a Postgres backup). However, do note that as users start logging in (creating new login sessions) via the new MAS setup, disabling MAS and reverting back to the Synapse user database will cause these new sessions to break.

  4. Migrate your data from Synapse to Matrix Authentication Service using syn2mas

  5. Adjust your configuration again, to:

  • remove the matrix_authentication_service_migration_in_progress: false line

  • if you had been using OIDC providers configured in Synapse, remove all Synapse OIDC-related configuration (matrix_synapse_oidc_*) to prevent it being in conflict with the MAS OIDC configuration

  1. Perform the installation again. At this point:

    • The homeserver will start delegating authentication to MAS.

    • The compatibility layer URLs will be installed. New login sessions will be completed by MAS.

  2. Verify that Matrix Authentication Service is installed correctly

Migrate your data from Synapse to Matrix Authentication Service using syn2mas

We don't ask you to run the syn2mas migration advisor command, because it only gives you the green light if your Synapse configuration (homeserver.yaml) is configured in a way that's compatible with MAS (delegating authentication to MAS; disabling Synapse's password config; etc.). Until we migrate your data with the syn2mas tool, we intentionally avoid doing these changes to allow existing user sessions to work.

You can invoke the syn2mas tool via the playbook by running the playbook's matrix-authentication-service-syn2mas tag. We recommend first doing a dry-run and then a real migration.

Configuring syn2mas

If you're using OIDC with Synapse, you will need to Configuring upstream OIDC provider mapping for syn2mas.

If you only have local (non-OIDC) users in your Synapse database, you can likely run syn2mas as-is (without doing additional configuration changes).

When you're done with potentially configuring syn2mas, proceed to doing a dry-run and then a real migration.

Configuring upstream OIDC provider mapping for syn2mas

If you have existing OIDC users in your Synapse user database (which will be the case if when using OIDC with Synapse), you may need to pass an additional --upstreamProviderMapping argument to the syn2mas tool to tell it which provider (on the Synapse side) maps to which other provider on the MAS side.

If you don't do this, syn2mas would report errors like this one:

[FATAL] migrate - [Failed to import external id 4264b0f0-4f11-4ddd-aedb-b500e4d07c25 with oidc-keycloak for user @alice:example.com: Error: Unknown upstream provider oidc-keycloak]

Below is an example situation and a guide for how to solve it.

If in matrix_synapse_oidc_providers your provider idp_id is (was) named keycloak, in the Synapse database users would be associated with the oidc-keycloak provider (note the oidc- prefix that was added automatically by Synapse to your idp_id value).

The same OIDC provider may have an id of 01HFVBY12TMNTYTBV8W921M5FA on the MAS side, as defined in matrix_authentication_service_config_upstream_oauth2_providers (see the Upstream OAuth2 configuration section above).

To tell syn2mas how the Synapse-configured OIDC provider maps to the new MAS-configured OIDC provider, add this additional configuration to your inventory/host_vars/matrix.example.com/vars.yml file:

# Adjust the mapping below to match your provider IDs on the Synapse side and the MAS side.
# Don't forget that Synapse automatically adds an `oidc-` prefix to provider ids defined in its configuration.
matrix_authentication_service_syn2mas_process_extra_arguments:
  - "--upstreamProviderMapping oidc-keycloak:01HFVBY12TMNTYTBV8W921M5FA"

Performing a syn2mas dry-run

Having configured syn2mas, we recommend doing a dry-run first to verify that everything will work out as expected.

A dry-run would not cause downtime, because it avoids stopping Synapse.

To perform a dry-run, run:

just run-tags matrix-authentication-service-syn2mas -e matrix_authentication_service_syn2mas_dry_run=true

Observe the command output (especially the last line of the the syn2mas output). If you are confident that the migration will work out as expected, you can proceed with a real migration.

Performing a real syn2mas migration

Before performing a real migration make sure:

  • you've familiarized yourself with the expectations

  • you've performed a Postgres backup, just in case

  • you're aware of the irreversibility of the migration process without disruption after users have created new login sessions via the new MAS setup

  • you've configured syn2mas, especially if you've used OIDC with Synapse

  • you've performed a syn2mas dry-run and don't see any issues in its output

To perform a real migration, run the matrix-authentication-service-syn2mas tag without the matrix_authentication_service_syn2mas_dry_run variable:

just run-tags matrix-authentication-service-syn2mas

Having performed a syn2mas migration once, trying to do it again will report errors for users that were already migrated (e.g. "Error: Unknown upstream provider oauth-delegated").

Verify that Matrix Authentication Service is installed correctly

After installation, run the doctor subcommand of the mas-cli command-line tool to verify that MAS is installed correctly.

You can do it:

  • either via the Ansible playbook's matrix-authentication-service-mas-cli-doctor tag: just run-tags matrix-authentication-service-mas-cli-doctor

  • or by running the mas-cli script on the server (which invokes the mas-cli tool inside a container): /matrix/matrix-authentication-service/bin/mas-cli doctor

If successful, you should see some output that looks like this:

💡 Running diagnostics, make sure that both MAS and Synapse are running, and that MAS is using the same configuration files as this tool.
✅ Matrix client well-known at "https://example.com/.well-known/matrix/client" is valid
✅ Homeserver is reachable at "http://matrix-synapse:8008/_matrix/client/versions"
✅ Homeserver at "http://matrix-synapse:8008/_matrix/client/v3/account/whoami" is reachable, and it correctly rejected an invalid token.
✅ The Synapse admin API is reachable at "http://matrix-synapse:8008/_synapse/admin/v1/server_version".
✅ The Synapse admin API is reachable with authentication at "http://matrix-synapse:8008/_synapse/admin/v1/background_updates/status".
✅ The legacy login API at "https://matrix.example.com/_matrix/client/v3/login" is reachable and is handled by MAS.

Management

You can use the mas-cli command-line tool (exposed via the /matrix/matrix-authentication-service/bin/mas-cli script) to perform administrative tasks against MAS.

This documentation page already mentions:

There are other sub-commands available. Run /matrix/matrix-authentication-service/bin/mas-cli to get an overview.

User registration

After Matrix Authentication Service is installed, users need to be managed there (unless you're managing them in an upstream OAuth2 provider).

You can register users new users as described in the Registering users documentation (via mas-cli manage register-user or the Ansible playbook's register-user tag).

Working around email deliverability issues

Because Matrix Authentication Service still insists on having a verified email address for each user, you may need to work around email deliverability issues if your email-sending configuration is not working.

Matrix Authentication Service attempts to verify email addresses by sending a verification email to the address specified by the user whenever they log in to an account without a verified email address.

If email delivery is not working, you can retrieve the email configuration code from the Matrix Authentication Service's logs (journalctl -fu matrix-authentication-service).

Alternatively, you can use the mas-cli management tool to manually verify email addresses for users. Example: /matrix/matrix-authentication-service/bin/mas-cli manage verify-email some.username email@example.com