December 10, 2012
\nDjango 1.4.3 addresses two security issues present in previous Django releases\nin the 1.4 series.
\nPlease be aware that this security release is slightly different from previous\nones. Both issues addressed here have been dealt with in prior security updates\nto Django. In one case, we have received ongoing reports of problems, and in\nthe other we’ve chosen to take further steps to tighten up Django’s code in\nresponse to independent discovery of potential problems from multiple sources.
\nSeveral earlier Django security releases focused on the issue of poisoning the\nHTTP Host header, causing Django to generate URLs pointing to arbitrary,\npotentially-malicious domains.
\nIn response to further input received and reports of continuing issues\nfollowing the previous release, we’re taking additional steps to tighten Host\nheader validation. Rather than attempt to accommodate all features HTTP\nsupports here, Django’s Host header validation attempts to support a smaller,\nbut far more common, subset:
\nHostnames must consist of characters [A-Za-z0-9] plus hyphen (‘-’) or dot\n(‘.’).
IP addresses – both IPv4 and IPv6 – are permitted.
Port, if specified, is numeric.
Any deviation from this will now be rejected, raising the exception\ndjango.core.exceptions.SuspiciousOperation.
Also following up on a previous issue: in July of this year, we made changes to\nDjango’s HTTP redirect classes, performing additional validation of the scheme\nof the URL to redirect to (since, both within Django’s own supplied\napplications and many third-party applications, accepting a user-supplied\nredirect target is a common pattern).
\nSince then, two independent audits of the code turned up further potential\nproblems. So, similar to the Host-header issue, we are taking steps to provide\ntighter validation in response to reported problems (primarily with third-party\napplications, but to a certain extent also within Django itself). This comes in\ntwo parts:
\n1. A new utility function, django.utils.http.is_safe_url, is added; this\nfunction takes a URL and a hostname, and checks that the URL is either\nrelative, or if absolute matches the supplied hostname. This function is\nintended for use whenever user-supplied redirect targets are accepted, to\nensure that such redirects cannot lead to arbitrary third-party sites.
2. All of Django’s own built-in views – primarily in the authentication system\n– which allow user-supplied redirect targets now use is_safe_url to\nvalidate the supplied URL.