signup: Add optional Altcha to realm registration.

zproject/computed_settings.py

@@ -68,6 +68,7 @@ from .configured_settings import (
     STATIC_URL,
     SUBMIT_USAGE_STATISTICS,
     TORNADO_PORTS,
+    USING_CAPTCHA,
     USING_PGROONGA,
     ZULIP_ADMINISTRATOR,
     ZULIP_SERVICE_PUSH_NOTIFICATIONS,
@@ -462,6 +463,11 @@ if DEVELOPMENT:
 else:
     TOR_EXIT_NODE_FILE_PATH = "/var/lib/zulip/tor-exit-nodes.json"
 
+if USING_CAPTCHA:
+    ALTCHA_HMAC_KEY = get_mandatory_secret("altcha_hmac")
+else:
+    ALTCHA_HMAC_KEY = ""
+
 ########################################################################
 # SECURITY SETTINGS
 ########################################################################

zproject/default_settings.py

@@ -259,6 +259,7 @@ RATE_LIMIT_TOR_TOGETHER = False
 SEND_LOGIN_EMAILS = True
 EMBEDDED_BOTS_ENABLED = False
 
+USING_CAPTCHA = False
 DEFAULT_RATE_LIMITING_RULES = {
     # Limits total number of API requests per unit time by each user.
     # Rate limiting general API access protects the server against

zproject/urls.py

@@ -26,6 +26,7 @@ from zerver.tornado.views import (
     web_reload_clients,
 )
 from zerver.views.alert_words import add_alert_words, list_alert_words, remove_alert_words
+from zerver.views.antispam import get_challenge
 from zerver.views.attachments import list_by_user, remove
 from zerver.views.auth import (
     api_fetch_api_key,
@@ -640,6 +641,7 @@ i18n_urls = [
     # Go to organization subdomain
     path("accounts/go/", realm_redirect, name="realm_redirect"),
     # Realm creation
+    path("json/antispam_challenge", get_challenge),
     path("new/", create_realm),
     path("new/<creation_key>", create_realm, name="create_realm"),
     # Realm reactivation