Support in Synapse for tracking agreement to server terms and conditions

Synapse 0.30 introduces support for tracking whether users have agreed to the terms and conditions set by the administrator of a server - and blocking access to the server until they have.

There are several parts to this functionality; each requires some specific configuration in homeserver.yaml to be enabled.

Note that various parts of the configuation and this document refer to the "privacy policy": agreement with a privacy policy is one particular use of this feature, but of course adminstrators can specify other terms and conditions unrelated to "privacy" per se.

Collecting policy agreement from a user

Synapse can be configured to serve the user a simple policy form with an "accept" button. Clicking "Accept" records the user's acceptance in the database and shows a success page.

To enable this, first create templates for the policy and success pages. These should be stored on the local filesystem.

These templates use the Jinja2 templating language, and docs/privacy_policy_templates gives examples of the sort of thing that can be done.

Note that the templates must be stored under a name giving the language of the template - currently this must always be en (for "English"); internationalisation support is intended for the future.

The template for the policy itself should be versioned and named according to the version: for example 1.0.html. The version of the policy which the user has agreed to is stored in the database.

Once the templates are in place, make the following changes to homeserver.yaml:

  1. Add a user_consent section, which should look like:

    user_consent:
  template_dir: privacy_policy_templates
  version: 1.0

    template_dir points to the directory containing the policy templates. version defines the version of the policy which will be served to the user. In the example above, Synapse will serve privacy_policy_templates/en/1.0.html.

  2. Add a form_secret setting at the top level:

    form_secret: "<unique secret>"

    This should be set to an arbitrary secret string (try pwgen -y 30 to generate suitable secrets).

    More on what this is used for below.

  3. Add consent wherever the client resource is currently enabled in the listeners configuration. For example:

    listeners:
  - port: 8008
    resources:
      - names:
        - client
        - consent

Finally, ensure that jinja2 is installed. If you are using a virtualenv, this should be a matter of pip install Jinja2. On debian, try apt-get install python-jinja2.

Once this is complete, and the server has been restarted, try visiting https://<server>/_matrix/consent. If correctly configured, this should give an error "Missing string query parameter 'u'". It is now possible to manually construct URIs where users can give their consent.

  1. Add the following to your configuration:

    user_consent:
  require_at_registration: true
  policy_name: "Privacy Policy" # or whatever you'd like to call the policy

  2. In your consent templates, make use of the public_version variable to see if an unauthenticated user is viewing the page. This is typically wrapped around the form that would be used to actually agree to the document:

    {% if not public_version %}
  <!-- The variables used here are only provided when the 'u' param is given to the homeserver -->
  <form method="post" action="consent">
    <input type="hidden" name="v" value="{{version}}"/>
    <input type="hidden" name="u" value="{{user}}"/>
    <input type="hidden" name="h" value="{{userhmac}}"/>
    <input type="submit" value="Sure thing!"/>
  </form>
{% endif %}

  3. Restart Synapse to apply the changes.

Visiting https://<server>/_matrix/consent should now give you a view of the privacy document. This is what users will be able to see when registering for accounts.

It may be useful to manually construct the "consent URI" for a given user - for instance, in order to send them an email asking them to consent. To do this, take the base https://<server>/_matrix/consent URL and add the following query parameters:

  • u: the user id of the user. This can either be a full MXID (@user:server.com) or just the localpart (user).

  • h: hex-encoded HMAC-SHA256 of u using the form_secret as a key. It is possible to calculate this on the commandline with something like:

    echo -n '<user>' | openssl sha256 -hmac '<form_secret>'

    This should result in a URI which looks something like: https://<server>/_matrix/consent?u=<user>&h=68a152465a4d....

Note that not providing a u parameter will be interpreted as wanting to view the document from an unauthenticated perspective, such as prior to registration. Therefore, the h parameter is not required in this scenario. To enable this behaviour, set require_at_registration to true in your user_consent config.

Sending users a server notice asking them to agree to the policy

It is possible to configure Synapse to send a server notice to anybody who has not yet agreed to the current version of the policy. To do so:

  • ensure that the consent resource is configured, as in the previous section

  • ensure that server notices are configured, as in the server notice documentation.

  • Add server_notice_content under user_consent in homeserver.yaml. For example:

    user_consent:
  server_notice_content:
    msgtype: m.text
    body: >-
      Please give your consent to the privacy policy at %(consent_uri)s.

    Synapse automatically replaces the placeholder %(consent_uri)s with the consent uri for that user.

  • ensure that public_baseurl is set in homeserver.yaml, and gives the base URI that clients use to connect to the server. (It is used to construct consent_uri in the server notice.)

Blocking users from using the server until they agree to the policy

Synapse can be configured to block any attempts to join rooms or send messages until the user has given their agreement to the policy. (Joining the server notices room is exempted from this).

To enable this, add block_events_error under user_consent. For example:

user_consent:
  block_events_error: >-
    You can't send any messages until you consent to the privacy policy at
    %(consent_uri)s.

Synapse automatically replaces the placeholder %(consent_uri)s with the consent uri for that user.

ensure that public_baseurl is set in homeserver.yaml, and gives the base URI that clients use to connect to the server. (It is used to construct consent_uri in the error.)