django-defender
A simple Django reusable app that blocks people from brute forcing login attempts. The goal is to make this as fast as possible, so that we do not slow down the login attempts.
We will use a cache so that it doesn't have to hit the database in order to check the database on each login attempt. The first version will be based on Redis, but the goal is to make this configurable so that people can use whatever backend best fits their needs.
Sites using django-defender
If you are using defender on your site, submit a PR to add to the list.
Documentation
Documentation is available on Read the Docs:
https://django-defender.readthedocs.io
Features
Log all login attempts to the database
Support for reverse proxies with different headers for IP addresses
Rate limit based on
- Username
- IP address
Use Redis for the blacklist
Configuration
Redis server
- Host
- Port
- Database
- Password
- Key prefix
Block length
Number of incorrect attempts before block
95% code coverage
Full documentation
Ability to store login attempts to the database
Management command to clean up login attempts database table
Admin pages
- List of blocked usernames and IP addresses
- List of recent login attempts
- Ability to unblock people
Can be easily adapted to custom authentication method.
Signals are sent when blocking username or IP
Admin pages
Requirements
- Python: 3.7, 3.8, 3.9, 3.10, PyPy
- Django: 3.x, 4.x
- Redis: 5.x, 6.x, 7.x
Installation
Download code, and run setup in one of the following ways depending on the method.
To install the production ready version from PyPI:
pip install django-defenderTo install the development version from source code after download:
python setup.py installTo install the master branch development version from the GitHub repository:
pip install -e git+http://github.com/kencochran django-defender.git#egg=django_defender-devFirst of all, you must add this project to your list of INSTALLED_APPS in
settings.py
INSTALLED_APPS = [
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.sites',
# ...
'defender',
# ...
]Next, install the FailedLoginMiddleware middleware
MIDDLEWARE_CLASSES = [
'django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'defender.middleware.FailedLoginMiddleware',
]If you want to manage the blocked users via the Django admin, then add the
following to your urls.py
urlpatterns = [
path('admin/defender/', include('defender.urls')), # defender admin
path('admin/', admin.site.urls), # normal admin
# your own patterns follow...
]Migrations
You will need to create tables in your database that are necessary for operation.
python manage.py migrate defenderManagement commands
cleanup_django_defender
If you have a website with a lot of traffic, the AccessAttempts table will get full pretty quickly. If you don't need to keep the data for auditing purposes there is a management command to help you keep it clean.
It will look at your DEFENDER_ACCESS_ATTEMPT_EXPIRATION setting to determine
which records will be deleted. Default if not specified, is 24 hours.
$ python manage.py cleanup_django_defenderYou can set this up as a daily or weekly cron job to keep the table size down.
# run at 12:24 AM every morning.
24 0 * * * /usr/bin/python manage.py cleanup_django_defender >> /var/log/django_defender_cleanup.logLong term goals
- Pluggable backends, so people can use something other than Redis
- Email users when their account is blocked
- Add a whitelist for username and ip's that we will never block (admin's, etc)
- Add a permanent black list for IP addresses
- Scan for known proxy IPs and do not block requests coming from those (improve the chances that a good IP is blocked)
- Add management command to prune old (configurable) login attempts.
Performance
The goal of defender is to make it as fast as possible so that it doesn't slow down the login process. In order to make sure our goals are met we need a way to test the application to make sure we are on the right track. The best way to do this is to compare how fast a normal Django login takes with defender and django-axes.
The normal django login, would be our baseline, and we expect it to be the fastest of the 3 methods, because there are no additional checks happening.
The defender login would most likely be slower then the django login, and hopefully faster then the django-axes login. The goal is to make it as little of a difference between the regular raw login, and defender.
The django-axes login speed, will probably be the slowest of the three since it does more checks and does a lot of database queries.
The best way to determine the speed of a login is to do a load test against an application with each setup, and compare the login times for each type.
Load testing
In order to make sure we cover all the different types of logins, in our load test we need to have more then one test.
- All success: We will do a load test with nothing but successful logins.
- Mixed: some success some failure: We will load test with some successful logins and some failures to see how the failure effect the performance.
- All Failures: We will load test with all failure logins and see the difference in performance.
We will need a sample application that we can use for the load test, with the only difference is the configuration where we either load defender, axes, or none of them.
We can use a hosted load testing service, or something like jmeter. Either way we need to be consistent for all of the tests. If we use jmeter, we should have our jmeter configuration for others to run the tests on their own.
Results of load tests
We will post the results here. We will explain each test, and show the results along with some charts.
Why not django-axes
django-axes is great but it puts everything in the database, and this causes a bottle neck when you have a lot of data. It slows down the auth requests by as much as 200-300ms. This might not be much for some sites, but for others it is too long.
This started out as a fork of django-axes, and is using as much of their code as possible, and removing the parts not needed, and speeding up the lookups to improve the login.
How django-defender works
- When someone tries to login, we first check to see if they are currently blocked. We check the username they are trying to use, as well as the IP address. If they are blocked, goto step 5. If not blocked go to step 2.
- They are not blocked, so we check to see if the login was valid. If valid go to step 6. If not valid go to step 3.
- Login attempt wasn't valid. Add their username and IP address for this attempt to the cache. If this brings them over the limit, add them to the blocked list, and then goto step 5. If not over the limit goto step 4.
- Login was invalid, but not over the limit. Send them back to the login screen to try again.
- User is blocked: Send them to the blocked page, telling them they are blocked, and give an estimate on when they will be unblocked.
- Login is valid. Reset any failed login attempts, and forward to their destination.
Cache backend
Defender uses the cache to save the failed attempts.
Cache keys
Counters:
- prefix:failed:ip:[ip] (count, TTL)
- prefix:failed:username:[username] (count, TTL)
Booleans (if present it is blocked):
- prefix:blocked:ip:[ip] (true, TTL)
- prefix:blocked:username:[username] (true, TTL)
Customizing django-defender
You have a couple options available to you to customize django-defender a bit.
These should be defined in your settings.py file.
DEFENDER_LOGIN_FAILURE_LIMIT: Int: The number of login attempts allowed before a record is created for the failed logins. [Default:3]DEFENDER_LOGIN_FAILURE_LIMIT_USERNAME: Int: The number of login attempts allowed on a username before a record is created for the failed logins. [Default:DEFENDER_LOGIN_FAILURE_LIMIT]DEFENDER_LOGIN_FAILURE_LIMIT_IP: Int: The number of login attempts allowed from an IP before a record is created for the failed logins. [Default:DEFENDER_LOGIN_FAILURE_LIMIT]DEFENDER_BEHIND_REVERSE_PROXY: Boolean: Is defender behind a reverse proxy? [Default:False]DEFENDER_REVERSE_PROXY_HEADER: String: the name of the http header with your reverse proxy IP address [Default:HTTP_X_FORWARDED_FOR]DEFENDER_LOCK_OUT_BY_IP_AND_USERNAME: Boolean: Locks a user out based on a combination of IP and Username. This stops a user denying access to the application for all other users accessing the app from behind the same IP address. [Default:False]DEFENDER_DISABLE_IP_LOCKOUT: Boolean: If this is True, it will not lockout the users IP address, it will only lockout the username. [Default: False]DEFENDER_DISABLE_USERNAME_LOCKOUT: Boolean: If this is True, it will not lockout usernames, it will only lockout IP addresess. [Default: False]DEFENDER_COOLOFF_TIME: Int: If set, defines a period of inactivity after which old failed login attempts and username/ip lockouts will be forgotten. An integer, will be interpreted as a number of seconds. If 0, neither the failed login attempts nor the username/ip locks will expire. [Default:300]DEFENDER_ATTEMPT_COOLOFF_TIME: Int: If set, overrides the period of inactivity after which old failed login attempts will be forgotten set by DEFENDER_COOLOFF_TIME. An integer, will be interpreted as a number of seconds. If 0, the failed login attempts will not expire. [Default:DEFENDER_COOLOFF_TIME]DEFENDER_LOCKOUT_COOLOFF_TIME: Int or List: If set, overrides the period of inactivity after which username/ip lockouts will be forgotten set by DEFENDER_COOLOFF_TIME. An integer, will be interpreted as a number of seconds. A list of integers, will be interpreted as a number of seconds for users with the integer's index being how many previous lockouts (up to some maximum) occurred in the lastDEFENDER_ACCESS_ATTEMPT_EXPIRATIONhours. If the property is set to 0 or [], the username/ip lockout will not expire. [Default:DEFENDER_COOLOFF_TIME]DEFENDER_LOCKOUT_TEMPLATE: String: [Default:None] If set, specifies a template to render when a user is locked out. Template receives the following context variables:cooloff_time_seconds: The cool off time in secondscooloff_time_minutes: The cool off time in minutesfailure_limit: The number of failures before you get blocked.
DEFENDER_USERNAME_FORM_FIELD: String: the name of the form field that contains your users usernames. [Default:username]DEFENDER_CACHE_PREFIX: String: The cache prefix for your defender keys. [Default:defender]DEFENDER_LOCKOUT_URL: String: The URL you want to redirect to if someone is locked out.DEFENDER_REDIS_URL: String: the redis url for defender. [Default:redis://localhost:6379/0] (Example with password:redis://:mypassword@localhost:6379/0)DEFENDER_REDIS_PASSWORD_QUOTE: Boolean: if special character in redis password (like '@'), we can quote passwordurllib.parse.quote("password!@#"), and set to True. [Default:False]DEFENDER_REDIS_NAME: String: the name of your cache client on the CACHES django setting. If set,DEFENDER_REDIS_URLwill be ignored. [Default:None]DEFENDER_STORE_ACCESS_ATTEMPTS: Boolean: If you want to store the login attempt to the database, set to True. If False, it is not saved [Default:True]DEFENDER_USE_CELERY: Boolean: If you want to use Celery to store the login attempt to the database, set to True. If False, it is saved inline. [Default:False]DEFENDER_ACCESS_ATTEMPT_EXPIRATION: Int: Length of time in hours for how long to keep the access attempt records in the database before the management command cleans them up. [Default:24]DEFENDER_GET_USERNAME_FROM_REQUEST_PATH: String: The import path of the function that access username from request. If you want to use custom function to access and process username from request - you can specify it here. [Default:defender.utils.username_from_request]
Rationale for using DEFENDER_ATTEMPT_COOLOFF_TIME and DEFENDER_LOCKOUT_COOLOFF_TIME
While using DEFENDER_COOLOFF_TIME alone is sufficent for most use cases, when using defender in some specific scenarios such as in a high security setting, developers may wish to have finer
grained control over how long invalid login attempts are "remembered" while under consideration for lockout compared to the time those lockout keys are actually locked out from the system.
DEFENDER_ATTEMPT_COOLOFF_TIME and DEFENDER_LOCKOUT_COOLOFF_TIME allow for this exact fine grained configuration.
We can also take a low security and low scale example like a high school's website. Such a website might be run on some of the school's computers and administrated by the school's IT staff and computer
science teachers (if lucky enough to have any). In this scenario we can imagine that there are significant portions of the website accessible without authentication, but logging in to the website could
provide access to some relatively privileged information such as the student's name, email, grades, and class schedule. Finally since there is an email linked with the account, we will assume that there
is password reset functionality which unblocks the account when completed. In such a case, one could imagine that there is no need to remember failed logins for long periods of time since the application
would simply wish to protect against potential denial of service attacks. This could be accomplished keeping DEFENDER_ATTEMPT_COOLOFF_TIME low, say 30 seconds, and setting DEFENDER_LOCKOUT_COOLOFF_TIME
to something much higher like 600 seconds. By keeping DEFENDER_ATTEMPT_COOLOFF_TIME low and locking out bad actors for significant periods of time by setting DEFENDER_LOCKOUT_COOLOFF_TIME high,
rapid brute force login attacks will still be defeated and their small server will have more space in their cache for other data. And by providing password reset functionality as described above, these hypothetical
administrators could limit their required involvement in unblocking real users while retaining the intended accessibility of their website.
While the previous example is somewhat contrived, the full power of these configurations is demonstrated with the following explanation and example.
When DEFENDER_STORE_ACCESS_ATTEMPTS is True, DEFENDER_LOCKOUT_COOLOFF_TIME can also be configured as a list of integers. When configured as a list,
the number of previous failed login attempts for the configured lockout key is divided by DEFENDER_LOGIN_FAILURE_LIMIT to produce an intentionally overestimated count
of the number of failed logins for the period defined by DEFENDER_ACCESS_ATTEMPT_EXPIRATION. This ends up being an overestimate because the time between the failed login attempts
is not considered when doing this calculation. While this may seem harsh, in some specific scenarios the additional protection against slower attacks can be worth thepotentialinconvenience
caused to real users of the system.
One such example of this could be a public web accessible web application that houses sensitive information of it's users (let's say personal financial records).
The application and data therein should be accessible with minimal interruption, however security is integral so delays can be tolerated up to a point.
Under these circumstances we may have a desire to simply set DEFENDER_COOLOFF_TIME to a very large integer or even 0 for maximum protection. But this would mean that
if a real userdoesget locked out of the system, we will need an administrator to manually unblock them which of course is cumbersome and costly.
By setting DEFENDER_ATTEMPT_COOLOFF_TIME to a large enough number, let's say 600 and setting DEFENDER_LOCKOUT_COOLOFF_TIME to a list of increasing integers (ie. [60, 120, 300, 600, 0]) we can
protect our theoretical application comprably to if we had simply set DEFENDER_COOLOFF_TIME to 600 while disrupting our users significantly less.
Adapting to other authentication methods
defender can be used for authentication other than Django authentication system.
E.g. if django-rest-framework authentication has to be protected from brute force attack, a custom authentication method can be implemented.
There's sample BasicAuthenticationDefender class based on djangorestframework.BasicAuthentication:
import base64
import binascii
from django.utils.translation import gettext_lazy as _
from rest_framework import HTTP_HEADER_ENCODING, exceptions
from rest_framework.authentication import (
BasicAuthentication,
get_authorization_header,
)
from defender import utils
from defender import config
class BasicAuthenticationDefender(BasicAuthentication):
def get_username_from_request(self, request):
auth = get_authorization_header(request).split()
return base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')[0]
def authenticate(self, request):
auth = get_authorization_header(request).split()
if not auth or auth[0].lower() != b'basic':
return None
if len(auth) == 1:
msg = _('Invalid basic header. No credentials provided.')
raise exceptions.AuthenticationFailed(msg)
elif len(auth) > 2:
msg = _('Invalid basic header. Credentials string should not contain spaces.')
raise exceptions.AuthenticationFailed(msg)
if utils.is_already_locked(request, get_username=self.get_username_from_request):
detail = "You have attempted to login {failure_limit} times, with no success." \
"Your account is locked for {cooloff_time_seconds} seconds" \
"".format(
failure_limit=config.FAILURE_LIMIT,
cooloff_time_seconds=config.LOCKOUT_COOLOFF_TIME[
defender_utils.get_lockout_cooloff_time(username=self.get_username_from_request(request))
]
)
raise exceptions.AuthenticationFailed(_(detail))
try:
auth_parts = base64.b64decode(auth[1]).decode(HTTP_HEADER_ENCODING).partition(':')
except (TypeError, UnicodeDecodeError, binascii.Error):
msg = _('Invalid basic header. Credentials not correctly base64 encoded.')
raise exceptions.AuthenticationFailed(msg)
userid, password = auth_parts[0], auth_parts[2]
login_unsuccessful = False
login_exception = None
try:
response = self.authenticate_credentials(userid, password)
except exceptions.AuthenticationFailed as e:
login_unsuccessful = True
login_exception = e
utils.add_login_attempt_to_db(request,
login_valid=not login_unsuccessful,
get_username=self.get_username_from_request)
# add the failed attempt to Redis in case of a failed login or resets the attempt count in case of success
utils.check_request(request,
login_unsuccessful=login_unsuccessful,
get_username=self.get_username_from_request)
if login_unsuccessful:
raise login_exception
return responseTo make it work add BasicAuthenticationDefender to DEFAULT_AUTHENTICATION_CLASSES above all other authentication methods in your settings.py.
Adapting to other authentication methods :- django-rest-auth in djangorestframework
defender can be incorporated with the combination of django-rest-framework and django-rest-auth which can be used to authenticate users.
Reference
Below is a sample BasicAuthenticationDefender class based on rest_framework.authentication.TokenAuthentication which uses django-rest-auth library for user authentication.
import base64
import binascii
from django.conf import settings
from django.contrib.auth import get_user_model, authenticate
from django.contrib.auth.forms import PasswordResetForm, SetPasswordForm
from django.contrib.auth.tokens import default_token_generator
from django.utils.http import urlsafe_base64_decode as uid_decoder
from django.utils.translation import ugettext_lazy as _
from django.utils.encoding import force_text
from rest_framework import serializers, exceptions, HTTP_HEADER_ENCODING
from rest_framework.exceptions import ValidationError
from defender import utils as defender_utils
from defender import config
from rest_framework.authentication import (
get_authorization_header,
)
# Get the UserModel
UserModel = get_user_model()
class BasicAuthenticationDefender(serializers.Serializer):
username = serializers.CharField(required=False, allow_blank=True)
email = serializers.EmailField(required=False, allow_blank=True)
password = serializers.CharField(style={'input_type': 'password'})
def authenticate(self, **kwargs):
request = self.context['request']
if hasattr(settings, 'ACCOUNT_AUTHENTICATION_METHOD'):
login_field = settings.ACCOUNT_AUTHENTICATION_METHOD
else:
login_field = 'username'
userid = self.username_from_request(request, login_field)
if defender_utils.is_already_locked(request, username=userid):
detail = "You have attempted to login {failure_limit} times with no success. "
.format(
failure_limit=config.FAILURE_LIMIT,
cooloff_time_seconds=config.LOCKOUT_COOLOFF_TIME[defender_utils.get_lockout_cooloff_time(username=userid)]
)
raise exceptions.AuthenticationFailed(_(detail))
login_unsuccessful = False
login_exception = None
try:
response = authenticate(request, **kwargs)
if response == None:
login_unsuccessful = True
msg = _('Unable to log in with provided credentials.')
# raise exceptions.ValidationError(msg)
login_exception = exceptions.ValidationError(msg)
except exceptions.AuthenticationFailed as e:
login_unsuccessful = True
login_exception = e
defender_utils.add_login_attempt_to_db(request,
login_valid=not login_unsuccessful,
username=userid)
user_not_blocked = defender_utils.check_request(request,
login_unsuccessful=login_unsuccessful,
username=userid)
if user_not_blocked and not login_unsuccessful:
return response
raise login_exception
def _validate_email(self, email, password):
user = None
if email and password:
user = self.authenticate(email=email, password=password)
else:
msg = _('Must include "email" and "password".')
raise exceptions.ValidationError(msg)
return user
def _validate_username(self, username, password):
user = None
if username and password:
user = self.authenticate(username=username, password=password)
else:
msg = _('Must include "username" and "password".')
raise exceptions.ValidationError(msg)
return user
def _validate_username_email(self, username, email, password):
user = None
if email and password:
user = self.authenticate(email=email, password=password)
elif username and password:
user = self.authenticate(username=username, password=password)
else:
msg = _('Must include either "username" or "email" and "password".')
raise exceptions.ValidationError(msg)
return user
def validate(self, attrs):
username = attrs.get('username')
email = attrs.get('email')
password = attrs.get('password')
user = None
if 'allauth' in settings.INSTALLED_APPS:
from allauth.account import app_settings
# Authentication through email
if app_settings.AUTHENTICATION_METHOD == app_settings.AuthenticationMethod.EMAIL:
user = self._validate_email(email, password)
# Authentication through username
elif app_settings.AUTHENTICATION_METHOD == app_settings.AuthenticationMethod.USERNAME:
user = self._validate_username(username, password)
# Authentication through either username or email
else:
user = self._validate_username_email(username, email, password)
else:
# Authentication without using allauth
if email:
try:
username = UserModel.objects.get(
email__iexact=email).username()
except UserModel.DoesNotExist:
pass
if username:
user = self._validate_username_email(username, '', password)
# Did we get back an active user?
if user:
if not user.is_active:
msg = _('User account is disabled.')
raise exceptions.ValidationError(msg)
else:
msg = _('Unable to log in with provided credentials.')
raise exceptions.ValidationError(msg)
# If required, is the email verified?
if 'rest_auth.registration' in settings.INSTALLED_APPS:
from allauth.account import app_settings
if app_settings.EMAIL_VERIFICATION == app_settings.EmailVerificationMethod.MANDATORY:
email_address = user.emailaddress_set.get(email=user.email)
if not email_address.verified:
raise serializers.ValidationError(
_('E-mail is not verified.'))
attrs['user'] = user
return attrs
def username_from_request(self, request, login_field):
user_data = request._data
return user_data[login_field]To make it work add BasicAuthenticationDefender to REST_AUTH_SERIALIZERS dictionary in your settings.py under the key LOGIN_SERIALIZER.
For example, in your settings.py add the below line,
REST_AUTH_SERIALIZERS = {
'LOGIN_SERIALIZER': '<path to your basic authentication defender python file>.BasicAuthenticationDefender',
}Adapting for password reset forms
defender can be adapted for Django’s PasswordResetView to prevent too many submissions.
We need to create some new views that subclass Django’s built-in LoginView, PasswordResetView & PasswordResetConfirmView — then use these views in our urls.py as replacements for Django’s built-ins.
The views block based on email address submitted on the password reset view. This is different than the default implementation (which uses username), so we have to be careful to clean up after ourselves on sign-in & completed password reset.
from defender import utils as def_utils
from django.contrib.auth import views as auth_views
class UserSignIn(auth_views.LoginView):
def form_valid(self, form):
"""Force clear all the cached Defender statues for the authenticated user’s email address."""
super_valid = super().form_valid(form)
def_utils.check_request(self.request, False, username=form.get_user().email)
return super_valid
class PasswordResetBruteForceProtectedView(auth_views.PasswordResetView):
def get(self, request, *args, **kwargs):
"""Confirm the user isn’t already blocked by IP before showing the password reset view."""
if def_utils.is_already_locked(request):
return def_utils.lockout_response(request)
return super().get(request, *args, **kwargs)
def post(self, request, *args, **kwargs):
"""
Confirm the user isn’t already blocked by IP before allowing form POST.
Also, force log this form POST as a single entry in the Defender cache, against the submitted email address.
"""
if def_utils.is_already_locked(request):
return def_utils.lockout_response(request)
def_utils.check_request(
request, login_unsuccessful=True, username=request.POST.get("email")
)
return super().post(request, *args, **kwargs)
class PasswordResetConfirmBruceForceProtectedView(auth_views.PasswordResetConfirmView):
def get(self, request, *args, **kwargs):
"""Confirm the user isn’t already blocked by IP before showing the password confirm view."""
if def_utils.is_already_locked(request):
return def_utils.lockout_response(request)
return super().get(request, *args, **kwargs)
def post(self, request, *args, **kwargs):
"""Confirm the user isn’t already blocked by IP before allowing form POST for the password change confirmation."""
if def_utils.is_already_locked(request):
return def_utils.lockout_response(request)
return super().post(request, *args, **kwargs)
def form_valid(self, form):
"""Force clear all the cached Defender statues for the user’s email address after successfully changing their password."""
super_valid = super().form_valid(form)
def_utils.check_request(
self.request, login_unsuccessful=False, username=self.user.email
)
return super_validDjango signals
django-defender will send signals when blocking a username or an IP address. To set up signal receiver functions:
from django.dispatch import receiver
from defender import signals
@receiver(signals.username_block)
def username_blocked(username, **kwargs):
print("%s was blocked!" % username)
@receiver(signals.ip_block)
def ip_blocked(ip_address, **kwargs):
print("%s was blocked!" % ip_address)Running tests
Tests can be run, after you clone the repository and having Django installed, like:
PYTHONPATH=$PYTHONPATH:$PWD django-admin test defender --settings=defender.test_settingsWith Code coverage:
PYTHONPATH=$PYTHONPATH:$PWD coverage run --source=defender $(which django-admin) test defender --settings=defender.test_settingsReleasing
python setup.py sdisttwine upload dist/*