From 1514f17aa60772f48839130f9a5071b9ffe15213 Mon Sep 17 00:00:00 2001
From: Andrew Godwin <andrew@aeracode.org>
Date: Thu, 23 May 2013 16:14:27 +0100
Subject: [PATCH] Rotate CSRF token on login

---
 django/contrib/auth/__init__.py         |  2 ++
 django/contrib/auth/tests/test_views.py | 40 ++++++++++++++++++++++++-
 django/middleware/csrf.py               |  8 +++++
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/django/contrib/auth/__init__.py b/django/contrib/auth/__init__.py
index e032038775..029193d582 100644
--- a/django/contrib/auth/__init__.py
+++ b/django/contrib/auth/__init__.py
@@ -3,6 +3,7 @@ import re
 from django.conf import settings
 from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.utils.module_loading import import_by_path
+from django.middleware.csrf import rotate_token
 
 from .signals import user_logged_in, user_logged_out, user_login_failed
 
@@ -84,6 +85,7 @@ def login(request, user):
     request.session[BACKEND_SESSION_KEY] = user.backend
     if hasattr(request, 'user'):
         request.user = user
+    rotate_token(request)
     user_logged_in.send(sender=user.__class__, request=request, user=user)
 
 
diff --git a/django/contrib/auth/tests/test_views.py b/django/contrib/auth/tests/test_views.py
index a6bea47877..fe1d7fb52f 100644
--- a/django/contrib/auth/tests/test_views.py
+++ b/django/contrib/auth/tests/test_views.py
@@ -12,18 +12,21 @@ from django.contrib.auth.models import User
 from django.core import mail
 from django.core.exceptions import SuspiciousOperation
 from django.core.urlresolvers import reverse, NoReverseMatch
-from django.http import QueryDict
+from django.http import QueryDict, HttpRequest
 from django.utils.encoding import force_text
 from django.utils.html import escape
 from django.utils.http import urlquote
 from django.utils._os import upath
 from django.test import TestCase
 from django.test.utils import override_settings
+from django.middleware.csrf import CsrfViewMiddleware
+from django.contrib.sessions.middleware import SessionMiddleware
 
 from django.contrib.auth import SESSION_KEY, REDIRECT_FIELD_NAME
 from django.contrib.auth.forms import (AuthenticationForm, PasswordChangeForm,
                 SetPasswordForm, PasswordResetForm)
 from django.contrib.auth.tests.utils import skipIfCustomUser
+from django.contrib.auth.views import login as login_view
 
 
 @override_settings(
@@ -460,6 +463,41 @@ class LoginTest(AuthViewsTestCase):
         # the custom authentication form used by this login asserts
         # that a request is passed to the form successfully.
 
+    def test_login_csrf_rotate(self, password='password'):
+        """
+        Makes sure that a login rotates the currently-used CSRF token.
+        """
+        # Do a GET to establish a CSRF token
+        # TestClient isn't used here as we're testing middleware, essentially.
+        req = HttpRequest()
+        CsrfViewMiddleware().process_view(req, login_view, (), {})
+        req.META["CSRF_COOKIE_USED"] = True
+        resp = login_view(req)
+        resp2 = CsrfViewMiddleware().process_response(req, resp)
+        csrf_cookie = resp2.cookies.get(settings.CSRF_COOKIE_NAME, None)
+        token1 = csrf_cookie.coded_value
+
+        # Prepare the POST request
+        req = HttpRequest()
+        req.COOKIES[settings.CSRF_COOKIE_NAME] = token1
+        req.method = "POST"
+        req.POST = {'username': 'testclient', 'password': password, 'csrfmiddlewaretoken': token1}
+        req.REQUEST = req.POST
+
+        # Use POST request to log in
+        SessionMiddleware().process_request(req)
+        CsrfViewMiddleware().process_view(req, login_view, (), {})
+        req.META["SERVER_NAME"] = "testserver"  # Required to have redirect work in login view
+        req.META["SERVER_PORT"] = 80
+        req.META["CSRF_COOKIE_USED"] = True
+        resp = login_view(req)
+        resp2 = CsrfViewMiddleware().process_response(req, resp)
+        csrf_cookie = resp2.cookies.get(settings.CSRF_COOKIE_NAME, None)
+        token2 = csrf_cookie.coded_value
+
+        # Check the CSRF token switched
+        self.assertNotEqual(token1, token2)
+
 
 @skipIfCustomUser
 class LoginURLSettings(AuthViewsTestCase):
diff --git a/django/middleware/csrf.py b/django/middleware/csrf.py
index 98974f011a..1b5732fbbf 100644
--- a/django/middleware/csrf.py
+++ b/django/middleware/csrf.py
@@ -53,6 +53,14 @@ def get_token(request):
     return request.META.get("CSRF_COOKIE", None)
 
 
+def rotate_token(request):
+    """
+    Changes the CSRF token in use for a request - should be done on login
+    for security purposes.
+    """
+    request.META["CSRF_COOKIE"] = _get_new_csrf_key()
+
+
 def _sanitize_token(token):
     # Allow only alphanum
     if len(token) > CSRF_KEY_LENGTH: