added feature to send email once the user is blocked based on username

defender/config.py

@@ -93,6 +93,12 @@ def get_setting(variable, default=None):
 
 USE_CELERY = get_setting("DEFENDER_USE_CELERY", False)
 
+EMAIL_USER_ON_ACCOUNT_LOCKED = get_setting("DEFENDER_EMAIL_USER_ON_ACCOUNT_LOCKED", False)
+# A 'user' instance is passed as context to lockout email template
+LOCKOUT_EMAIL_TEMPLATE_PATH = get_setting("DEFENDER_LOCKOUT_EMAIL_TEMPLATE_PATH", "defender/lockout_email.html")
+
+DEFAULT_FROM_EMAIL = get_setting("DEFENDER_DEFAULT_FROM_EMAIL")
+
 STORE_ACCESS_ATTEMPTS = get_setting("DEFENDER_STORE_ACCESS_ATTEMPTS", True)
 
 # Used by the management command to decide how long to keep access attempt

defender/templates/defender/lockout_email.html

@@ -0,0 +1,6 @@
+Hi {{ user.username }},
+<br>
+<br>
+Your account has been locked out due to too many failed login attempts. 
+Please contact the administrator to unlock your account.
+<br>

defender/utils.py

@@ -8,6 +8,9 @@
 from django.shortcuts import render
 from django.core.validators import validate_ipv46_address
 from django.core.exceptions import ValidationError
+from django.core.mail import send_mail
+from django.contrib.auth import get_user_model
+from django.template.loader import render_to_string
 from django.utils.module_loading import import_string
 
 from .connection import get_redis_connection
@@ -23,6 +26,7 @@
 REDIS_SERVER = get_redis_connection()
 
 LOG = logging.getLogger(__name__)
+User = get_user_model()
 
 
 def is_valid_ip(ip_address):
@@ -270,6 +274,8 @@ def block_username(username):
         REDIS_SERVER.set(key, "blocked")
     if not already_blocked:
         send_username_block_signal(username)
+        if config.EMAIL_USER_ON_ACCOUNT_LOCKED:
+            send_account_locked_email_to_user(username)
 
 
 def record_failed_attempt(ip_address, username):
@@ -460,3 +466,25 @@ def add_login_attempt_to_db(
         store_login_attempt(
             user_agent, ip_address, username, http_accept, path_info, login_valid
         )
+
+
+def send_account_locked_email_to_user(username:str):
+    """ Send an email to the user to notify them that their account has been locked """
+    try:
+        user = User.objects.get(username=username)
+    except User.DoesNotExist:
+        # TODO: Handle the case where the user does not exist
+        return
+
+    html_message = render_to_string(config.LOCKOUT_EMAIL_TEMPLATE_PATH, {"user": user})
+    plan_text_message = f"Hi {user.username}, Your account has been locked due to too many failed login attempts.Please contact an admin to unlock your account."
+    send_mail(
+        'Account Locked',
+        plan_text_message,
+        from_email=config.DEFAULT_FROM_EMAIL,
+        recipient_list=[user.email],
+        html_message=html_message, 
+        fail_silently=False
+    )
+
+