The Hypocrisy Weblog

It is possible for a malicious site visitor to register a special username and gain administrative privileges on your Wordpress Blog. (Described below)

It is recommended to update now!

Wordpress 2.5 Cookie Integrity Protection Vulnerability

Original release date: 2008-04-25
Last revised: 2008-04-25
Latest version: http://www.cl.cam.ac.uk/users/sjm217/advisories/wordpress-cookie-integrity.txt
CVE ID: CVE-2008-1930
Source: Steven J. Murdoch <http://www.cl.cam.ac.uk/users/sjm217/>

Systems Affected:

Wordpress 2.5

Overview:

An attacker, who is able to register a specially crafted username on
a Wordpress 2.5 installation, is able to generate authentication
cookies for other chosen accounts.

This vulnerability exists because it is possible to modify
authentication cookies without invalidating the cryptographic
integrity protection.

If a Wordpress blog is configured to freely permit account creation,
a remote attacker can gain Wordpress-administrator access and then
elevate this to arbitrary code execution as the web server user.

The vulnerability is fixed in Wordpress 2.5.1

I. Description

Since version 2.5, Wordpress authenticates logged-in users through a
cryptographically protected cookie, based on papers by Fu et al [1]
and Liu et al [2]. This measure was introduced partly in response to
vulnerability CVE-2007-6013 [3,4].

The new cookies are of the form:

“wordpress_”.COOKIEHASH = USERNAME . “|” . EXPIRY_TIME . “|” . MAC

Where:

COOKIEHASH:  MD5 hash of the site URL (to maintain cookie uniqueness)
USERNAME:    The username for the authenticated user
EXPIRY_TIME: When cookie should expire, in seconds since start of epoch
MAC:         HMAC-MD5(USERNAME . EXPIRY_TIME) under a key derived
from a secret and USERNAME . EXPIRY_TIME.

The flaw in this scheme is that USERNAME and EXPIRY_TIME are not
delimited in the MAC calculation. Hence the cookie may be modified,
without altering MAC, provided that the concatenation of USERNAME and
EXPIRY_TIME remains unchanged.

This class of vulnerability, the cryptographic splicing attack, was
commented on by Fu et al [1], but Wordpress does not employ their
recommended defence.

An attacker wishing to exploit this vulnerability would therefore
create an unprivileged account with its username starting with
“admin”. The cookie returned on logging into this account can then be
manipulated so as to be valid for the administrator account.

II. Impact

A remote attacker, who can create an account with specially crafted
username, is able to gain administrator level access to the Wordpress
installation. Through standard techniques, this can be escalated to
arbitrary PHP code execution as the web server system user.

III. Solution

Upgrade to Wordpress 2.5.1

Workarounds:

- De-select “Anyone can register” in the Membership section of
General Settings to disable account creation.

References:

[1] Dos and Don’ts of Client Authentication on the Web,
Kevin Fu, Emil Sit, Kendra Smith, Nick Feamster
http://pdos.csail.mit.edu/papers/webauth:tr.pdf
[2] A Secure Cookie Protocol,
Alex X. Liu, Jason M. Kovacs, Chin-Tser Huang, Mohamed G. Gouda
http://www.cse.msu.edu/~alexliu/publications/Cookie/cookie.pdf
[3] Wordpress Cookie Authentication Vulnerability: CVE-2007-6013
Steven J. Murdoch,
http://www.cl.cam.ac.uk/users/sjm217/advisories/wordpress-cookie-auth.txt
[4] http://trac.wordpress.org/ticket/5367

Timeline:

2008-04-22: security@wordpress.com notified
Confirmation of receipt received
2008-04-25: Wordpress 2.5.1 released incorporating patch
Vulnerability notice published

Reference: [Link]

cnet’s web 2.0 blog, “Webware” has announced it’s Webware 100 winners-list. The question is now; how is this list relevant to anyone in the Internet-business? Each and every category, 10 of them, has 10 winners each – and each and every site on the top 100-list anyone who’s involved in working with the Internet (in any way) have heard of.

The categories are; Browsing, Communications, Community, Data, Entertainment, Media, Mobile, Productivity and Commerce, Publishing, Reference.

Surely, it is a good ego boost for the people behind the services to get recognition, but does it serve any journalistic purpose? I am not so sure about that; Rafe Needleman and the Webware crew are preaching for the already saved. There is no internal ranking of the sites in the individual categories – so how do I as a visitor know which site got more votes than the other? (Yes, alright – they do have a list of the over-all top 10 and the sites that got over 1000 votes, though it doesn’t show the internal ranking in between the sites within each category. Perhaps the over-all statistic material wasn’t enough?! I don’t know…)

From my own perspective I am glad that the swizz army-knife-like site Netvibes, which deserves more media coverage – as it is a really nice service to keep track on all your communication needs ranging from rss-feeds (sites, forums, email, blogs etc), to email, to skype, to.. yeah – you get the idea.

Google was the company with most services in the top 100-list, yet this is not surprising as they are the biggest site on the Internet.

To the Webware authors; Please make the list more detailed the next time and get a broader statistic foundation (aka get more people to vote on the list), then we’re talking about a relevant list.

From the Wordpress blog:

“It’s new release time. The latest in our venerable 2.0 series, which now counts over 1.2 million downloads, is available for download immediately, and we suggest everyone upgrade as this includes security fixes. We’re breaking the tradition of naming releases after jazz musicians to congratulate Ryan Boren on his new son (and first WP baby) Ronan.”

There are a number of changes / fixes to this spectacular  publishing software, and the most important ones are listed here.

Personally I consider the security fix to wp-db backup to be the most important, but also changes such as plugins are sorted by plugin name, instead of filename and that the authors dropdown is now sorted by display_name handy as well. (Not to mention that “make_clickable()” no longer adds links within links)

Speaking about wordpress-hacks; I’m about to install a tag-cloud plugin, anyone have experience of this? Aka; You have installed such a plugin with good results?