[1.8.x] Fixed #24161 -- Stored the user primary key as a serialized value in the session.

This allows using a UUIDField primary key along with the JSON session
serializer.

Thanks to Trac alias jamesbeith for the report and Simon Charette
for the initial patch.

Backport of 0f7f5bc9e7 from master

django/contrib/auth/__init__.py

@@ -53,6 +53,12 @@ def _clean_credentials(credentials):
     return credentials
 
 
+def _get_user_session_key(request):
+    # This value in the session is always serialized to a string, so we need
+    # to convert it back to Python whenever we access it.
+    return get_user_model()._meta.pk.to_python(request.session[SESSION_KEY])
+
+
 def authenticate(**credentials):
     """
     If the given credentials are valid, return a User object.
@@ -93,7 +99,7 @@ def login(request, user):
         session_auth_hash = user.get_session_auth_hash()
 
     if SESSION_KEY in request.session:
-        if request.session[SESSION_KEY] != user.pk or (
+        if _get_user_session_key(request) != user.pk or (
                 session_auth_hash and
                 request.session.get(HASH_SESSION_KEY) != session_auth_hash):
             # To avoid reusing another user's session, create a new, empty
@@ -102,7 +108,7 @@ def login(request, user):
             request.session.flush()
     else:
         request.session.cycle_key()
-    request.session[SESSION_KEY] = user.pk
+    request.session[SESSION_KEY] = user._meta.pk.value_to_string(user)
     request.session[BACKEND_SESSION_KEY] = user.backend
     request.session[HASH_SESSION_KEY] = session_auth_hash
     if hasattr(request, 'user'):
@@ -158,7 +164,7 @@ def get_user(request):
     from .models import AnonymousUser
     user = None
     try:
-        user_id = request.session[SESSION_KEY]
+        user_id = _get_user_session_key(request)
         backend_path = request.session[BACKEND_SESSION_KEY]
     except KeyError:
         pass

tests/auth_tests/models/__init__.py

@@ -5,9 +5,10 @@ from .invalid_models import (
     CustomUserBadRequiredFields,
 )
 from .with_foreign_key import CustomUserWithFK, Email
+from .uuid_pk import UUIDUser
 
 __all__ = (
     'CustomPermissionsUser', 'CustomUserNonUniqueUsername',
     'CustomUserNonListRequiredFields', 'CustomUserBadRequiredFields',
-    'CustomUserWithFK', 'Email', 'IsActiveTestUser1',
+    'CustomUserWithFK', 'Email', 'IsActiveTestUser1', 'UUIDUser',
 )

tests/auth_tests/models/uuid_pk.py

@@ -0,0 +1,13 @@
+import uuid
+
+from django.contrib.auth.models import AbstractUser
+from django.contrib.auth.tests.custom_user import RemoveGroupsAndPermissions
+from django.db import models
+
+with RemoveGroupsAndPermissions():
+    class UUIDUser(AbstractUser):
+        """A user with a UUID as primary key"""
+        id = models.UUIDField(default=uuid.uuid4, primary_key=True)
+
+        class Meta:
+            app_label = 'auth'

tests/auth_tests/test_auth_backends.py

@@ -3,7 +3,9 @@ from __future__ import unicode_literals
 from datetime import date
 
 from django.conf import settings
-from django.contrib.auth import BACKEND_SESSION_KEY, authenticate, get_user
+from django.contrib.auth import (
+    BACKEND_SESSION_KEY, SESSION_KEY, authenticate, get_user,
+)
 from django.contrib.auth.backends import ModelBackend
 from django.contrib.auth.hashers import MD5PasswordHasher
 from django.contrib.auth.models import AnonymousUser, Group, Permission, User
@@ -13,7 +15,7 @@ from django.core.exceptions import ImproperlyConfigured, PermissionDenied
 from django.http import HttpRequest
 from django.test import TestCase, modify_settings, override_settings
 
-from .models import CustomPermissionsUser
+from .models import CustomPermissionsUser, UUIDUser
 
 
 class CountingMD5PasswordHasher(MD5PasswordHasher):
@@ -287,6 +289,18 @@ class CustomUserModelBackendAuthenticateTest(TestCase):
         self.assertEqual(test_user, authenticated_user)
 
 
+@override_settings(AUTH_USER_MODEL='auth.UUIDUser')
+class UUIDUserTests(TestCase):
+
+    def test_login(self):
+        """
+        A custom user with a UUID primary key should be able to login.
+        """
+        user = UUIDUser.objects.create_user(username='uuid', password='test')
+        self.assertTrue(self.client.login(username='uuid', password='test'))
+        self.assertEqual(UUIDUser.objects.get(pk=self.client.session[SESSION_KEY]), user)
+
+
 class TestObj(object):
     pass