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Impersonation backend for Django
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README.rst

Django Impersonate Auth

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Django Impersonate Auth is a simple drop in authentication backend that allows superusers to impersonate regular users in the system.

Impersonation is handled by signing in using the target user's username and the superuser's username and password, separated by a specific character, as the password.

Getting Started

To install this library, you can simply run

pip install -e git+https://github.com/JordanReiter/django-impersonate-auth.git#egg=django-impersonate-auth

Then add

'impersonate_auth.backends.ImpersonationBackend',

to the AUTHENTICATION_BACKENDS setting. If you don't currently have a value for AUTHENTICATION_BACKENDS, you can add this to your settings file, which includes the default backend plus the impersonation backend (both are required to function correctly):

AUTHENTICATION_BACKENDS = [
    'django.contrib.auth.backends.ModelBackend',
    'impersonate_auth.backends.ImpersonationBackend',
]

Usage

Using the default separator, a colon, here is an example of how to impersonate another (non superuser) user:

  • Normal User:
    Username: testuser
    Password: 12345
  • Super User:
    Username: superuser
    Password: 987654321
  • Super User impersonating Normal User:
    Username: testuser
    Password: superuser:987654321

Settings

The default separator is a colon (:), but this can be changed using the IMPERSONATE_AUTH_SEPARATOR setting. The following code changes it to an exclamation mark:

IMPERSONATE_AUTH_SEPARATOR = '!'

With this setting, in the example above, Super User would impersonate Normal User using the password superuser!987654321.

Important: because the username and password are separated by this character, it's essential to choose a character that would never be found in a username. For most login purposes, the colon : is a good choice because it is neither a legal character for a Django username or for an email address. [1]

Using Custom Authentication Backends

The package provides a mixin, ImpersonationBackendMixin, which should provide all the necessary code to implement impersonation for any authentication backend which uses a combination of username and password. The backend uses the USERNAME_FIELD property of the user model, so if you use a custom User model which uses a different field (for example, E-mail address) then it will still work correctly.

Adding impersonation to your custom backend just means creating a new class that extends both your existing and ImpersonationBackendMixin. For example, imagine a very insecure authentication backend called SillyBackend where the password is simply the username spelled backwards:

from django.contrib.auth.backends import ModelBackend
from django.contrib.auth import get_user_model

class SillyBackend(ModelBackend):
    '''
    A silly backend where the password for a user is their email address backwards.
    '''
    def authenticate(self, request=None, username=None, password=None):
        UserModel = get_user_model()
        try:
            silly_user = UserModel.objects.get_by_natural_key(username)
        except UserModel.DoesNotExist:
            silly_user = None
        if silly_user and password and password[::-1] == username:
            return silly_user

In order to implement the impersonation functionality, you would add the following code to your backends.py file:

from impersonate_auth.backends import ImpersonationBackendMixin

class SillyImpersonationBackend(ImpersonationBackendMixin, SillyBackend):
    def __init__(self, *args, **kwargs):
        super(SillyImpersonationBackend, self).__init__(*args, **kwargs)

No other coding needed! Just make sure to add path.to.backends.SillyImpersonationBackend to your AUTHENTICATION_BACKENDS setting.

Signals

In order to log or track impersonation, each time you log in using an impersonation login, a user_impersonated signal is sent. If it fails, a user_impersonation_failed signal is triggered. Note that these signals are only triggered if the login would have been a success with the correct login. That is, they are not triggered if the user you are trying to impersonate does not exist or would not be available for some other reason (e.g. they are inactive).

Credits

Thanks to Daniele Faraglia <https://github.com/joke2k> and the django-environ project <https://github.com/joke2k/django-environ>. Both my .travis.yml file and this readme were partially modeled on the respective files from that project.

User fdemmer on Reddit pointed out that if passwords contain the separator (normally a colon) this would cause an error as the code was written. It's fixed in this version. <https://www.reddit.com/r/django/comments/8x4ett/djangoimpersonateauth_a_simple_dropin/e21stvc/>

[1]Yes, colons are allowed, but only in the quoted string area of an email address. Since that's used just for display and not the actual email address, we can (hopefully) assume that users won't include it. Other characters that fall under this characters include (),:;<>[\] See RFC 3696, Section 4.1: <https://tools.ietf.org/html/rfc3696#section-4.1>

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