Alcatel-Lucent OmniSwitch Web Interface Weak Session ID

[Aerosol]

Advisory: Alcatel-Lucent OmniSwitch Web Interface Weak Session ID

During a penetration test, RedTeam Pentesting discovered a vulnerability
in the management web interface of an Alcatel-Lucent OmniSwitch 6450.
This interface uses easily guessable session IDs, which allows attackers
to authenticate as a currently logged-in user and perform administrative
tasks.


Details
=======

Product: Alcatel-Lucent OmniSwitch 6450, 6250, 6850E, 9000E, 6400, 6855
Affected Versions:
  AOS 6.4.5.R02
  AOS 6.4.6.R01
  AOS 6.6.4.R01
  AOS 6.6.5.R02
Fixed Versions:
  AOS 6.6.5.80.R02
  AOS 6.6.4.309.R01
Vulnerability Type: Session Management - low identifier entropy
Security Risk: high
Vendor URL: http://enterprise.alcatel-lucent.com/?product=OmniSwitch6450&page=overview
Vendor Status: fixed version released
Advisory URL: https://www.redteam-pentesting.de/advisories/rt-sa-2015-003
Advisory Status: published
CVE: CVE-2015-2804
CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2015-2804


Introduction
============

"The Alcatel-Lucent OmniSwitch 6450 Gigabit and Fast Ethernet Stackable LAN
Switches are the latest value stackable switches in the OmniSwitch family of
products. The OmniSwitch 6450 was specifically built for versatility offering
optional upgrade paths for 10 Gigabit stacking, 10 Gigabit Ethernet uplinks,
from Fast to Gigabit user ports (L models) and Metro Ethernet services."

(from the vendor's homepage)


More Details
============

The management web interface of the OmniSwitch 6450 can be accessed using a web
browser via HTTP. A switch with the example IP 192.0.2.1 is accessible via
the following URL:

http://192.0.2.1/

A client is then redirected to the following URL:

http://192.0.2.1/web/content/index.html

For unauthenticated users the URL displays a login form and sets a session
cookie with a session ID. A request to the URL with the command line HTTP
client cURL shows the Set-Cookie header:

  $ curl -I http://192.0.2.1/web/content/index.html
  HTTP/1.1 200 OK
  Date: Tue, 17 Mar 2015 08:25:42 GMT
  Server: Agranat-EmWeb/R5_2_4
  [...]
  Set-Cookie: session=sess_11012;PATH=/

The session cookie has the name "session" and its value begins with the
string "sess_". By repeatedly requesting the URL with cURL it became obvious
that the suffix is always a number between 1 and 32,000. This suggests that
there are only about 32,000 possible session IDs, resulting in only 15 bits
of entropy. Our tests showed that it was possible to get a throughput of about
50 HTTP requests per second, this means that in order to try every possible
session ID an attacker will need at most 11 minutes. On average, the time it
takes to find a valid session ID for an active user is even lower.


Proof of Concept
================

For an attacker it is very easy to distinguish between a valid and an invalid
session ID by looking at the HTTP response size. During our tests, requesting
an invalid session ID always returned the login form, which was 3027 bytes
in length. With a valid session ID, the management web interface is
returned by the webserver and the response is larger.

A number of requests in the range of the possible session cookies can be easily
executed using wfuzz [0]:

------------------------------------------------------------------------
./wfuzz.py -z range,1-32000 --hl 3027 -H "Cookie: session=sess_FUZZ" http://192.0.2.1/web/content/index.html
------------------------------------------------------------------------


Workaround
==========

Administrators should avoid using the management web interface and use the
serial console or administrate the switch over SSH instead. The web interface
can be disabled by executing the following commands:

  no ip service http
  no ip service secure-http

If the web interface is needed, it must be ensured that only authorised persons
are able to even connect to the web server. In addition, the HTTP session
timeout can be lowered to one minute with the following command:

  session timeout http 1


Fix
===

Upgrade the firmware to a fixed version.


Security Risk
=============

The vulnerability poses a high risk. An attacker can easily authenticate to a
switch with the privileges of another user who is currently logged in. The
attack is simple and fast. The only precondition is that a user is already
using the switch during the attack. Attackers might actively trick
administrators into logging in by social engineering.


Timeline
========

2015-03-16 Vulnerability identified
2015-03-25 Customer approves disclosure to vendor
2015-03-26 CVE number requested
2015-03-31 CVE number assigned
2015-04-01 Vendor notified
2015-04-02 Vendor acknowledged receipt of advisories
2015-04-08 Requested status update from vendor, vendor is investigating
2015-04-29 Requested status update from vendor, vendor is still investigating
2015-05-22 Requested status update from vendor
2015-05-27 Vendor is working on the issue
2015-06-05 Vendor notified customers
2015-06-08 Vendor provided details about affected versions
2015-06-10 Advisory released


References
==========

[0] https://github.com/xmendez/wfuzz


RedTeam Pentesting GmbH

Source