==========================
Django 1.4.3 release notes
==========================

*December 10, 2012*

Django 1.4.3 addresses two security issues present in previous Django releases
in the 1.4 series.

Please be aware that this security release is slightly different from previous
ones. Both issues addressed here have been dealt with in prior security updates
to Django. In one case, we have received ongoing reports of problems, and in
the other we've chosen to take further steps to tighten up Django's code in
response to independent discovery of potential problems from multiple sources.

Host header poisoning
---------------------

Several earlier Django security releases focused on the issue of poisoning the
HTTP Host header, causing Django to generate URLs pointing to arbitrary,
potentially-malicious domains.

In response to further input received and reports of continuing issues
following the previous release, we're taking additional steps to tighten Host
header validation. Rather than attempt to accommodate all features HTTP
supports here, Django's Host header validation attempts to support a smaller,
but far more common, subset:

* Hostnames must consist of characters ``[A-Za-z0-9]`` plus hyphen ('-') or dot
  ('.').
* IP addresses -- both IPv4 and IPv6 -- are permitted.
* Port, if specified, is numeric.

Any deviation from this will now be rejected, raising the exception
:exc:`django.core.exceptions.SuspiciousOperation`.

Redirect poisoning
------------------

Also following up on a previous issue: in July of this year, we made changes to
Django's HTTP redirect classes, performing additional validation of the scheme
of the URL to redirect to (since, both within Django's own supplied
applications and many third-party applications, accepting a user-supplied
redirect target is a common pattern).

Since then, two independent audits of the code turned up further potential
problems. So, similar to the Host-header issue, we are taking steps to provide
tighter validation in response to reported problems (primarily with third-party
applications, but to a certain extent also within Django itself). This comes in
two parts:

1. A new utility function, ``django.utils.http.is_safe_url``, is added; this
function takes a URL and a hostname, and checks that the URL is either
relative, or if absolute matches the supplied hostname. This function is
intended for use whenever user-supplied redirect targets are accepted, to
ensure that such redirects cannot lead to arbitrary third-party sites.

2. All of Django's own built-in views -- primarily in the authentication system
-- which allow user-supplied redirect targets now use ``is_safe_url`` to
validate the supplied URL.
