From c401ae9a7dfb1a94a8a61927ed541d6f93089587 Mon Sep 17 00:00:00 2001 From: Tim Graham Date: Mon, 17 Oct 2016 12:14:49 -0400 Subject: [PATCH] [1.8.x] Fixed CVE-2016-9014 -- Validated Host header when DEBUG=True. This is a security fix. --- django/http/request.py | 9 +++++---- docs/ref/settings.txt | 10 +++++++--- docs/releases/1.8.16.txt | 22 ++++++++++++++++++++++ tests/requests/tests.py | 29 +++++++++++++++-------------- 4 files changed, 49 insertions(+), 21 deletions(-) diff --git a/django/http/request.py b/django/http/request.py index 398cf20dfb..c680a39eab 100644 --- a/django/http/request.py +++ b/django/http/request.py @@ -85,12 +85,13 @@ class HttpRequest(object): if server_port != ('443' if self.is_secure() else '80'): host = '%s:%s' % (host, server_port) - # There is no hostname validation when DEBUG=True - if settings.DEBUG: - return host + # Allow variants of localhost if ALLOWED_HOSTS is empty and DEBUG=True. + allowed_hosts = settings.ALLOWED_HOSTS + if settings.DEBUG and not allowed_hosts: + allowed_hosts = ['localhost', '127.0.0.1', '[::1]'] domain, port = split_domain_port(host) - if domain and validate_host(domain, settings.ALLOWED_HOSTS): + if domain and validate_host(domain, allowed_hosts): return host else: msg = "Invalid HTTP_HOST header: %r." % host diff --git a/docs/ref/settings.txt b/docs/ref/settings.txt index 382ce2edfc..d6f6e7c937 100644 --- a/docs/ref/settings.txt +++ b/docs/ref/settings.txt @@ -108,14 +108,18 @@ If the ``Host`` header (or ``X-Forwarded-Host`` if list, the :meth:`django.http.HttpRequest.get_host()` method will raise :exc:`~django.core.exceptions.SuspiciousOperation`. -When :setting:`DEBUG` is ``True`` or when running tests, host validation is -disabled; any host will be accepted. Thus it's usually only necessary to set it -in production. +When :setting:`DEBUG` is ``True`` and ``ALLOWED_HOSTS`` is empty, the host +is validated against ``['localhost', '127.0.0.1', '[::1]']``. This validation only applies via :meth:`~django.http.HttpRequest.get_host()`; if your code accesses the ``Host`` header directly from ``request.META`` you are bypassing this security protection. +.. versionchanged:: 1.8.16 + + In older versions, ``ALLOWED_HOSTS`` wasn't checked if ``DEBUG=True``, but + it's now checked to prevent a DNS rebinding attack. + .. setting:: ALLOWED_INCLUDE_ROOTS ALLOWED_INCLUDE_ROOTS diff --git a/docs/releases/1.8.16.txt b/docs/releases/1.8.16.txt index aa5d9cccea..9cd82d8d7a 100644 --- a/docs/releases/1.8.16.txt +++ b/docs/releases/1.8.16.txt @@ -19,3 +19,25 @@ the ``manage.py test --keepdb`` option or if the user has an active session (such as an attacker's connection). A randomly generated password is now used for each test run. + +DNS rebinding vulnerability when ``DEBUG=True`` +=============================================== + +Older versions of Django don't validate the ``Host`` header against +``settings.ALLOWED_HOSTS`` when ``settings.DEBUG=True``. This makes them +vulnerable to a `DNS rebinding attack +`_. + +While Django doesn't ship a module that allows remote code execution, this is +at least a cross-site scripting vector, which could be quite serious if +developers load a copy of the production database in development or connect to +some production services for which there's no development instance, for +example. If a project uses a package like the ``django-debug-toolbar``, then +the attacker could execute arbitrary SQL, which could be especially bad if the +developers connect to the database with a superuser account. + +``settings.ALLOWED_HOSTS`` is now validated regardless of ``DEBUG``. For +convenience, if ``ALLOWED_HOSTS`` is empty and ``DEBUG=True``, the following +variations of localhost are allowed ``['localhost', '127.0.0.1', '::1']``. If +your local settings file has your production ``ALLOWED_HOSTS`` value, you must +now omit it to get those fallback values. diff --git a/tests/requests/tests.py b/tests/requests/tests.py index f4a8aead92..87fb0c91fe 100644 --- a/tests/requests/tests.py +++ b/tests/requests/tests.py @@ -673,21 +673,22 @@ class HostValidationTests(SimpleTestCase): request.get_host() @override_settings(DEBUG=True, ALLOWED_HOSTS=[]) - def test_host_validation_disabled_in_debug_mode(self): - """If ALLOWED_HOSTS is empty and DEBUG is True, all hosts pass.""" - request = HttpRequest() - request.META = { - 'HTTP_HOST': 'example.com', - } - self.assertEqual(request.get_host(), 'example.com') + def test_host_validation_in_debug_mode(self): + """ + If ALLOWED_HOSTS is empty and DEBUG is True, variants of localhost are + allowed. + """ + valid_hosts = ['localhost', '127.0.0.1', '[::1]'] + for host in valid_hosts: + request = HttpRequest() + request.META = {'HTTP_HOST': host} + self.assertEqual(request.get_host(), host) - # Invalid hostnames would normally raise a SuspiciousOperation, - # but we have DEBUG=True, so this check is disabled. - request = HttpRequest() - request.META = { - 'HTTP_HOST': "invalid_hostname.com", - } - self.assertEqual(request.get_host(), "invalid_hostname.com") + # Other hostnames raise a SuspiciousOperation. + with self.assertRaises(SuspiciousOperation): + request = HttpRequest() + request.META = {'HTTP_HOST': 'example.com'} + request.get_host() @override_settings(ALLOWED_HOSTS=[]) def test_get_host_suggestion_of_allowed_host(self):