Send out emails with links to extend an account's validity period

synapse/config/emailconfig.py

@@ -71,6 +71,8 @@ class EmailConfig(Config):
             self.email_notif_from = email_config["notif_from"]
             self.email_notif_template_html = email_config["notif_template_html"]
             self.email_notif_template_text = email_config["notif_template_text"]
+            self.email_expiry_template_html = email_config["expiry_template_html"]
+            self.email_expiry_template_text = email_config["expiry_template_text"]
 
             template_dir = email_config.get("template_dir")
             # we need an absolute path, because we change directory after starting (and
@@ -120,7 +122,7 @@ class EmailConfig(Config):
 
     def default_config(self, config_dir_path, server_name, **kwargs):
         return """
-        # Enable sending emails for notification events
+        # Enable sending emails for notification events or expiry notices
         # Defining a custom URL for Riot is only needed if email notifications
         # should contain links to a self-hosted installation of Riot; when set
         # the "app_name" setting is ignored.
@@ -142,6 +144,9 @@ class EmailConfig(Config):
         #   #template_dir: res/templates
         #   notif_template_html: notif_mail.html
         #   notif_template_text: notif_mail.txt
+        #   # Templates for account expiry notices.
+        #   expiry_template_html: notice_expiry.html
+        #   expiry_template_text: notice_expiry.txt
         #   notif_for_new_users: True
         #   riot_base_url: "http://localhost/riot"
         """

synapse/config/registration.py

@@ -21,12 +21,26 @@ from synapse.util.stringutils import random_string_with_symbols
 
 
 class AccountValidityConfig(Config):
-    def __init__(self, config):
-        self.enabled = (len(config) > 0)
+    def __init__(self, config, synapse_config):
+        self.enabled = config.get("enabled", False)
+        self.renew_by_email_enabled = ("renew_at" in config)
 
-        period = config.get("period", None)
-        if period:
-            self.period = self.parse_duration(period)
+        if self.enabled:
+            if "period" in config:
+                self.period = self.parse_duration(config["period"])
+            else:
+                raise ConfigError("'period' is required when using account validity")
+
+            if "renew_at" in config:
+                self.renew_at = self.parse_duration(config["renew_at"])
+
+            if "renew_email_subject" in config:
+                self.renew_email_subject = config["renew_email_subject"]
+            else:
+                self.renew_email_subject = "Renew your %(app)s account"
+
+        if self.renew_by_email_enabled and "public_baseurl" not in synapse_config:
+            raise ConfigError("Can't send renewal emails without 'public_baseurl'")
 
 
 class RegistrationConfig(Config):
@@ -40,7 +54,9 @@ class RegistrationConfig(Config):
                 strtobool(str(config["disable_registration"]))
             )
 
-        self.account_validity = AccountValidityConfig(config.get("account_validity", {}))
+        self.account_validity = AccountValidityConfig(
+            config.get("account_validity", {}), config,
+        )
 
         self.registrations_require_3pid = config.get("registrations_require_3pid", [])
         self.allowed_local_3pids = config.get("allowed_local_3pids", [])
@@ -86,11 +102,31 @@ class RegistrationConfig(Config):
         #
         #enable_registration: false
 
-        # Optional account validity parameter. This allows for, e.g., accounts to
-        # be denied any request after a given period.
+        # Optional account validity configuration. This allows for accounts to be denied
+        # any request after a given period.
+        #
+        # ``enabled`` defines whether the account validity feature is enabled. Defaults
+        # to False.
+        #
+        # ``period`` allows setting the period after which an account is valid
+        # after its registration. When renewing the account, its validity period
+        # will be extended by this amount of time. This parameter is required when using
+        # the account validity feature.
+        #
+        # ``renew_at`` is the amount of time before an account's expiry date at which
+        # Synapse will send an email to the account's email address with a renewal link.
+        # This needs the ``email`` and ``public_baseurl`` configuration sections to be
+        # filled.
+        #
+        # ``renew_email_subject`` is the subject of the email sent out with the renewal
+        # link. ``%%(app)s`` can be used as a placeholder for the ``app_name`` parameter
+        # from the ``email`` section.
         #
         #account_validity:
+        #  enabled: True
         #  period: 6w
+        #  renew_at: 1w
+        #  renew_email_subject: "Renew your %%(app)s account"
 
         # The user must provide all of the below types of 3PID when registering.
         #