diff --git a/django/template/defaultfilters.py b/django/template/defaultfilters.py index e876c555f3..e32b7f7a5f 100644 --- a/django/template/defaultfilters.py +++ b/django/template/defaultfilters.py @@ -12,8 +12,8 @@ from django.utils import formats from django.utils.dateformat import format, time_format from django.utils.encoding import iri_to_uri from django.utils.html import ( - avoid_wrapping, conditional_escape, escape, escapejs, linebreaks, - strip_tags, urlize as _urlize, + avoid_wrapping, conditional_escape, escape, escapejs, + json_script as _json_script, linebreaks, strip_tags, urlize as _urlize, ) from django.utils.safestring import SafeData, mark_safe from django.utils.text import ( @@ -82,6 +82,15 @@ def escapejs_filter(value): return escapejs(value) +@register.filter(is_safe=True) +def json_script(value, element_id): + """ + Output value JSON-encoded, wrapped in a ', + element_id, mark_safe(json_str) + ) + + def conditional_escape(text): """ Similar to escape(), except that it doesn't operate on pre-escaped strings. diff --git a/docs/ref/templates/builtins.txt b/docs/ref/templates/builtins.txt index 634adf42e3..a4e0a0d455 100644 --- a/docs/ref/templates/builtins.txt +++ b/docs/ref/templates/builtins.txt @@ -1782,6 +1782,46 @@ For example:: If ``value`` is the list ``['a', 'b', 'c']``, the output will be the string ``"a // b // c"``. +.. templatefilter:: json_script + +``json_script`` +--------------- + +.. versionadded:: 2.1 + +Safely outputs a Python object as JSON, wrapped in a `` + +The resulting data can be accessed in JavaScript like this: + +.. code-block:: javascript + + var el = document.getElementById('hello-data'); + var value = JSON.parse(el.textContent || el.innerText); + +XSS attacks are mitigated by escaping the characters "<", ">" and "&". For +example if ``value`` is ``{'hello': 'world&'}``, the output is: + +.. code-block:: html + + + +This is compatible with a strict Content Security Policy that prohibits in-page +script execution. It also maintains a clean separation between passive data and +executable code. + .. templatefilter:: last ``last`` diff --git a/docs/releases/2.1.txt b/docs/releases/2.1.txt index 52519170db..ae3dd67bc9 100644 --- a/docs/releases/2.1.txt +++ b/docs/releases/2.1.txt @@ -205,7 +205,8 @@ Signals Templates ~~~~~~~~~ -* ... +* The new :tfilter:`json_script` filter safely outputs a Python object as JSON, + wrapped in a ``' + ) diff --git a/tests/utils_tests/test_html.py b/tests/utils_tests/test_html.py index e6d1fe9a59..e2ebce4556 100644 --- a/tests/utils_tests/test_html.py +++ b/tests/utils_tests/test_html.py @@ -4,8 +4,8 @@ from datetime import datetime from django.test import SimpleTestCase from django.utils.functional import lazystr from django.utils.html import ( - conditional_escape, escape, escapejs, format_html, html_safe, linebreaks, - smart_urlquote, strip_spaces_between_tags, strip_tags, + conditional_escape, escape, escapejs, format_html, html_safe, json_script, + linebreaks, smart_urlquote, strip_spaces_between_tags, strip_tags, ) from django.utils.safestring import mark_safe @@ -147,6 +147,28 @@ class TestUtilsHtml(SimpleTestCase): self.check_output(escapejs, value, output) self.check_output(escapejs, lazystr(value), output) + def test_json_script(self): + tests = ( + # "<", ">" and "&" are quoted inside JSON strings + (('&<>', '')), + # "<", ">" and "&" are quoted inside JSON objects + ( + {'a': ''}, + '' + ), + # Lazy strings are quoted + (lazystr('&<>'), ''), + ( + {'a': lazystr('')}, + '' + ), + ) + for arg, expected in tests: + with self.subTest(arg=arg): + self.assertEqual(json_script(arg, 'test_id'), expected) + def test_smart_urlquote(self): items = ( ('http://öäü.com/', 'http://xn--4ca9at.com/'),