# Consent Tracking - Synapse

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# 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 configuration and this document refer to the “privacy policy”: agreement with a privacy policy is one particular use of this feature, but of course administrators 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.

### Enabling consent tracking at registration

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.

### Constructing the consent URI

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.)