[1.5.x] Prevented data leakage in contrib.admin via query string manipulation.

This is a security fix. Disclosure following shortly.

django/contrib/admin/exceptions.py

@@ -0,0 +1,6 @@
+from django.core.exceptions import SuspiciousOperation
+
+
+class DisallowedModelAdminToField(SuspiciousOperation):
+    """Invalid to_field was passed to admin view via URL query string"""
+    pass

django/contrib/admin/options.py

@@ -275,6 +275,24 @@ class BaseModelAdmin(six.with_metaclass(forms.MediaDefiningClass)):
         clean_lookup = LOOKUP_SEP.join(parts)
         return clean_lookup in self.list_filter or clean_lookup == self.date_hierarchy
 
+    def to_field_allowed(self, request, to_field):
+        opts = self.model._meta
+
+        try:
+            field = opts.get_field(to_field)
+        except FieldDoesNotExist:
+            return False
+
+        # Make sure at least one of the models registered for this site
+        # references this field.
+        registered_models = self.admin_site._registry
+        for related_object in opts.get_all_related_objects():
+            if (related_object.model in registered_models and
+                    field == related_object.field.rel.get_related_field()):
+                return True
+
+        return False
+
     def has_add_permission(self, request):
         """
         Returns True if the given request has permission to add an object.

django/contrib/admin/views/main.py

@@ -12,6 +12,7 @@ from django.utils.translation import ugettext, ugettext_lazy
 from django.utils.http import urlencode
 
 from django.contrib.admin import FieldListFilter
+from django.contrib.admin.exceptions import DisallowedModelAdminToField
 from django.contrib.admin.options import IncorrectLookupParameters
 from django.contrib.admin.util import (quote, get_fields_from_path,
     lookup_needs_distinct, prepare_lookup_value)
@@ -58,7 +59,10 @@ class ChangeList(object):
             self.page_num = 0
         self.show_all = ALL_VAR in request.GET
         self.is_popup = IS_POPUP_VAR in request.GET
-        self.to_field = request.GET.get(TO_FIELD_VAR)
+        to_field = request.GET.get(TO_FIELD_VAR)
+        if to_field and not model_admin.to_field_allowed(request, to_field):
+            raise DisallowedModelAdminToField("The field %s cannot be referenced." % to_field)
+        self.to_field = to_field
         self.params = dict(request.GET.items())
         if PAGE_VAR in self.params:
             del self.params[PAGE_VAR]

docs/releases/1.4.14.txt

@@ -47,3 +47,18 @@ and the ``RemoteUserBackend``, a change to the ``REMOTE_USER`` header between
 requests without an intervening logout could result in the prior user's session
 being co-opted by the subsequent user. The middleware now logs the user out on
 a failed login attempt.
+
+Data leakage via query string manipulation in ``contrib.admin``
+===============================================================
+
+In older versions of Django it was possible to reveal any field's data by
+modifying the "popup" and "to_field" parameters of the query string on an admin
+change form page. For example, requesting a URL like
+``/admin/auth/user/?pop=1&t=password`` and viewing the page's HTML allowed
+viewing the password hash of each user. While the admin requires users to have
+permissions to view the change form pages in the first place, this could leak
+data if you rely on users having access to view only certain fields on a model.
+
+To address the issue, an exception will now be raised if a ``to_field`` value
+that isn't a related field to a model that has been registered with the admin
+is specified.

docs/releases/1.5.9.txt

@@ -47,3 +47,18 @@ and the ``RemoteUserBackend``, a change to the ``REMOTE_USER`` header between
 requests without an intervening logout could result in the prior user's session
 being co-opted by the subsequent user. The middleware now logs the user out on
 a failed login attempt.
+
+Data leakage via query string manipulation in ``contrib.admin``
+===============================================================
+
+In older versions of Django it was possible to reveal any field's data by
+modifying the "popup" and "to_field" parameters of the query string on an admin
+change form page. For example, requesting a URL like
+``/admin/auth/user/?pop=1&t=password`` and viewing the page's HTML allowed
+viewing the password hash of each user. While the admin requires users to have
+permissions to view the change form pages in the first place, this could leak
+data if you rely on users having access to view only certain fields on a model.
+
+To address the issue, an exception will now be raised if a ``to_field`` value
+that isn't a related field to a model that has been registered with the admin
+is specified.

tests/regressiontests/admin_views/tests.py

@@ -16,11 +16,12 @@ from django.core.files import temp as tempfile
 from django.core.urlresolvers import reverse
 # Register auth models with the admin.
 from django.contrib import admin
+from django.contrib.admin.exceptions import DisallowedModelAdminToField
 from django.contrib.admin.helpers import ACTION_CHECKBOX_NAME
 from django.contrib.admin.models import LogEntry, DELETION
 from django.contrib.admin.sites import LOGIN_FORM_KEY
 from django.contrib.admin.util import quote
-from django.contrib.admin.views.main import IS_POPUP_VAR
+from django.contrib.admin.views.main import IS_POPUP_VAR, TO_FIELD_VAR
 from django.contrib.admin.tests import AdminSeleniumWebDriverTestCase
 from django.contrib.auth import REDIRECT_FIELD_NAME
 from django.contrib.auth.models import Group, User, Permission, UNUSABLE_PASSWORD
@@ -557,6 +558,19 @@ class AdminViewBasicTest(TestCase):
         response = self.client.get("/test_admin/admin/admin_views/workhour/?employee__person_ptr__exact=%d" % e1.pk)
         self.assertEqual(response.status_code, 200)
 
+    def test_disallowed_to_field(self):
+        with self.assertRaises(DisallowedModelAdminToField):
+            response = self.client.get("/test_admin/admin/admin_views/section/", {TO_FIELD_VAR: 'missing_field'})
+
+        # Specifying a field that is not refered by any other model registered
+        # to this admin site should raise an exception.
+        with self.assertRaises(DisallowedModelAdminToField):
+            response = self.client.get("/test_admin/admin/admin_views/section/", {TO_FIELD_VAR: 'name'})
+
+        # Specifying a field referenced by another model should be allowed.
+        response = self.client.get("/test_admin/admin/admin_views/section/", {TO_FIELD_VAR: 'id'})
+        self.assertEqual(response.status_code, 200)
+
     def test_allowed_filtering_15103(self):
         """
         Regressions test for ticket 15103 - filtering on fields defined in a
@@ -2138,10 +2152,9 @@ class AdminSearchTest(TestCase):
         """Ensure that the to_field GET parameter is preserved when a search
         is performed. Refs #10918.
         """
-        from django.contrib.admin.views.main import TO_FIELD_VAR
-        response = self.client.get('/test_admin/admin/auth/user/?q=joe&%s=username' % TO_FIELD_VAR)
+        response = self.client.get('/test_admin/admin/auth/user/?q=joe&%s=id' % TO_FIELD_VAR)
         self.assertContains(response, "\n1 user\n")
-        self.assertContains(response, '<input type="hidden" name="t" value="username"/>', html=True)
+        self.assertContains(response, '<input type="hidden" name="%s" value="id"/>' % TO_FIELD_VAR, html=True)
 
     def test_exact_matches(self):
         response = self.client.get('/test_admin/admin/admin_views/recommendation/?q=bar')