[1.7.x] Fixed a settings leak possibility in the date template filter.

This is a security fix.

django/utils/formats.py

@@ -31,6 +31,24 @@ ISO_INPUT_FORMATS = {
 }
 
 
+FORMAT_SETTINGS = frozenset([
+    'DECIMAL_SEPARATOR',
+    'THOUSAND_SEPARATOR',
+    'NUMBER_GROUPING',
+    'FIRST_DAY_OF_WEEK',
+    'MONTH_DAY_FORMAT',
+    'TIME_FORMAT',
+    'DATE_FORMAT',
+    'DATETIME_FORMAT',
+    'SHORT_DATE_FORMAT',
+    'SHORT_DATETIME_FORMAT',
+    'YEAR_MONTH_FORMAT',
+    'DATE_INPUT_FORMATS',
+    'TIME_INPUT_FORMATS',
+    'DATETIME_INPUT_FORMATS',
+])
+
+
 def reset_format_cache():
     """Clear any cached formats.
 
@@ -85,6 +103,8 @@ def get_format(format_type, lang=None, use_l10n=None):
     be localized (or not), overriding the value of settings.USE_L10N.
     """
     format_type = force_str(format_type)
+    if format_type not in FORMAT_SETTINGS:
+        return format_type
     if use_l10n or (use_l10n is None and settings.USE_L10N):
         if lang is None:
             lang = get_language()

docs/releases/1.7.11.txt

@@ -4,7 +4,20 @@ Django 1.7.11 release notes
 
 *Under development*
 
-Django 1.7.11 fixes a data loss bug in 1.7.10.
+Django 1.7.11 fixes a security issue and a data loss bug in 1.7.10.
+
+Fixed settings leak possibility in ``date`` template filter
+===========================================================
+
+If an application allows users to specify an unvalidated format for dates and
+passes this format to the :tfilter:`date` filter, e.g.
+``{{ last_updated|date:user_date_format }}``, then a malicious user could
+obtain any secret in the application's settings by specifying a settings key
+instead of a date format. e.g. ``"SECRET_KEY"`` instead of ``"j/m/Y"``.
+
+To remedy this, the underlying function used by the ``date`` template filter,
+``django.utils.formats.get_format()``, now only allows accessing the date/time
+formatting settings.
 
 Bugfixes
 ========

tests/i18n/tests.py

@@ -828,6 +828,9 @@ class FormattingTests(TestCase):
                 '<input id="id_date_added" name="date_added" type="hidden" value="31.12.2009 06:00:00" />; <input id="id_cents_paid" name="cents_paid" type="hidden" value="59,47" />'
             )
 
+    def test_format_arbitrary_settings(self):
+        self.assertEqual(get_format('DEBUG'), 'DEBUG')
+
 
 class MiscTests(TestCase):