Subject: [PATCH django-impersonate] add option for auto-expiring impersonate sesions, implements #45

From: Leonhard Kuboschek <[email-masked]>
Date: Tue, 24 Nov 2020 11:25:39 +0100

# HG changeset patch
# User Leonhard Kuboschek <[email-masked]>
# Date 1606156336 -3600
#      Mon Nov 23 19:32:16 2020 +0100
# Node ID c574577f8c34d7f3d4575c98f14ee807c3b6d5e2
# Parent  1e3192bbb6762d1756fd203d28714620ef43da15
add option for auto-expiring impersonate sesions, implements #45

diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -395,6 +395,13 @@
 
 Default is `True`
 
+    MAX_DURATION
+
+A number specifying the maximum allowed duration of impersonation 
+sessions in **seconds**.
+
+Default is `None`
+
 Admin
 =====
 
diff --git a/README.rst b/README.rst
--- a/README.rst
+++ b/README.rst
@@ -464,6 +464,15 @@
 
 Default is ``True``
 
+::
+
+    MAX_DURATION
+
+A number specifying the maximum allowed duration of impersonation 
+sessions in **seconds**.
+
+Default is `None`
+
 Admin
 =====
 
diff --git a/impersonate/middleware.py b/impersonate/middleware.py
--- a/impersonate/middleware.py
+++ b/impersonate/middleware.py
@@ -1,6 +1,9 @@
 # -*- coding: utf-8 -*-
+from datetime import datetime, timedelta, tzinfo
+
 from django.http import HttpResponseNotAllowed
 from django.utils.deprecation import MiddlewareMixin
+from django.utils import timezone
 
 from .helpers import User, check_allow_for_uri, check_allow_for_user
 from .settings import settings
@@ -12,6 +15,18 @@
         request.impersonator = None
 
         if request.user.is_authenticated and '_impersonate' in request.session:
+            if settings.MAX_DURATION:
+                if '_impersonate_start' not in request.session:
+                    return
+
+                start_time = timezone.datetime.fromtimestamp(request.session['_impersonate_start'], timezone.utc)
+                
+                if datetime.now(timezone.utc) - start_time > timedelta(seconds=settings.MAX_DURATION):
+                    del request.session['_impersonate']
+                    del request.session['_impersonate_start']
+
+                    return
+
             new_user_id = request.session['_impersonate']
             if isinstance(new_user_id, User):
                 # Edge case for issue 15
diff --git a/impersonate/settings.py b/impersonate/settings.py
--- a/impersonate/settings.py
+++ b/impersonate/settings.py
@@ -23,6 +23,7 @@
     'ADMIN_DELETE_PERMISSION': False,
     'ADMIN_ADD_PERMISSION': False,
     'ADMIN_READ_ONLY': True,
+    'MAX_DURATION': None,
 }

diff --git a/impersonate/tests.py b/impersonate/tests.py
--- a/impersonate/tests.py
+++ b/impersonate/tests.py
@@ -22,6 +22,7 @@
 from distutils.version import LooseVersion
 from unittest.mock import PropertyMock, patch
 from urllib.parse import urlencode, urlsplit
+from datetime import datetime, timedelta, timezone
 
 import django
 from django.urls import include, path
@@ -110,11 +111,12 @@
             return None
         self.middleware = ImpersonateMiddleware(dummy_get_response)
 
-    def _impersonated_request(self, use_id=True):
+    def _impersonated_request(self, use_id=True, _impersonate_start=None):
         request = self.factory.get('/')
         request.user = self.superuser
         request.session = {
             '_impersonate': self.user.pk if use_id else self.user,
+            '_impersonate_start': _impersonate_start
         }
         self.middleware.process_request(request)
 
@@ -133,6 +135,45 @@
         '''
         self._impersonated_request(use_id=False)
 
+    @override_settings(IMPERSONATE={'MAX_DURATION': 3600})
+    def test_impersonated_request_with_max_duration(self):
+        self._impersonated_request(_impersonate_start=datetime.now(timezone.utc).timestamp())
+
+    @override_settings(IMPERSONATE={'MAX_DURATION': 3600})
+    def test_reject_without_start_time(self):
+        ''' Test to ensure that requests without a start time
+            are rejected when MAX_DURATION is set
+        '''
+        request = self.factory.get('/')
+        request.user = self.superuser
+        request.session = {
+            '_impersonate': self.user.pk,
+        }
+        self.middleware.process_request(request)
+
+        self.assertEqual(request.user, self.superuser)
+        self.assertFalse(request.user.is_impersonate)
+
+
+    @override_settings(IMPERSONATE={'MAX_DURATION': 3600})
+    def test_reject_expired_impersonation(self):
+        ''' Test to ensure that requests with a start time before (now - MAX_DURATION)
+            are rejected
+        '''
+        request = self.factory.get('/')
+        request.user = self.superuser
+        request.session = {
+            '_impersonate': self.user.pk,
+            '_impersonate_start': (datetime.now(timezone.utc) - timedelta(seconds=3601)).timestamp()
+        }
+        self.middleware.process_request(request)
+
+        self.assertEqual(request.user, self.superuser)
+        self.assertFalse(request.user.is_impersonate)
+        self.assertNotIn('_impersonate', request.session)
+        self.assertNotIn('_impersonate_start', request.session)
+
+
     def test_not_impersonated_request(self, use_id=True):
         """Check the real_user request attr is set correctly when **not** impersonating."""
         request = self.factory.get('/')
diff --git a/impersonate/views.py b/impersonate/views.py
--- a/impersonate/views.py
+++ b/impersonate/views.py
@@ -1,9 +1,11 @@
 # -*- coding: utf-8 -*-
+from datetime import datetime
 import logging
 
 from django.db.models import Q
 from django.http import Http404
 from django.shortcuts import get_object_or_404, redirect, render
+from django.utils import timezone
 
 from .decorators import allowed_user_required
 from .helpers import (
@@ -36,6 +38,7 @@
         raise Http404('Invalid value given.')
     if check_allow_for_user(request, new_user):
         request.session['_impersonate'] = new_user.pk
+        request.session['_impersonate_start'] = datetime.now(tz=timezone.utc).timestamp()
         prev_path = request.META.get('HTTP_REFERER')
         if prev_path:
             request.session[