Security releases issued
Today the Django team is issuing multiple releases -- Django 1.3.5, Django 1.4.3, and Django 1.5 beta 2 -- as part of our security process.
All users are encouraged to upgrade Django immediately.
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
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:
- 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.
- All of Django's own built-in views -- primarily in the
authentication system -- which allow user-supplied redirect targets
is_safe_urlto validate the supplied URL.
The issues resulting in this security release are present in the following versions of Django:
- Django development master branch (officially, 1.6-pre-alpha at this time).
- Django 1.5 prerelease branch (source of the 1.5 alpha and beta releases).
- Django 1.4.
- Django 1.3.
Patches have been applied to Django's master development branch, and to the 1.5, 1.4 and 1.3 release branches, which resolve the issues described above. The patches may be obtained directly from the following changesets:
- Development master branch: changeset 27560924ec1e567be4727ef8d7dfc4d3879c048c for the Host header issue, and changeset a2f2a399566dd68ce7e312fff5a5ba857066797d for the redirect issue.
- 1.5 release branch: changeset 77b06e41516d8136b56c040cba7e235b14750bfb for the Host header issue, and changeset fce1fa0f7fb984d4e76eb81ffc3cb9826046c3b5 for the redirect issue.
- 1.4 release branch: changeset 319627c184e71ae267d6b7f000e293168c7b6e09 for the Host header issue, and changeset b2ae0a63aeec741f1e51bac9a95a27fd635f9652 for the redirect issue.
- 1.3 release branch: changeset 2da4ace0bc1bc1d79bf43b368cb857f6f0cd6b1b for the Host header issue, and changeset 1515eb46daa0897ba5ad5f0a2db8969255f1b343 for the redirect issue.
The following new releases have been issed:
- Django 1.5 beta 2 (download | checksums)
- Django 1.4.3 (download | checksums)
- Django 1.3.5 (download | checksums)
As Django's development branch is currently in a pre-alpha state, and the 1.5 branch is in a beta state, users are strongly advised not to be running production deployments from them; if you are currently doing so, however, you are urged to upgrade imediately to the latest HEAD of the appropriate branch, which contains the above patches.
The followup to the Host header issue came from the reporter of the previous issue, James Kettle. The potential problems with the redirect code were spotted independently by user "Gunnar" in Trac, and by committer Florian Apolloner.
General notes regarding security reporting
As always, we ask that potential security issues be reported via private email to email@example.com, and not via Django's Trac instance or the django-developers list. Please see our security policies for further information.
Posted by James Bennett on December 10, 2012