D-Link DWL-1000AP can be compromised because of SNMP configuration
From: Jonathan Strine (jstrine@netpanel.com)Date: 12/21/01
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Date: 21 Dec 2001 19:26:55 -0000 From: Jonathan Strine <jstrine@netpanel.com> To: bugtraq@securityfocus.com('binary' encoding is not supported, stored as-is)
Here is a message that I sent to D-Link support
regarding this vulnerability:
-- Start email --
I currently own a DWL-1000AP Wireless Access
point. My firmware version is 3.2.28 #483 (Aug 23
2001). I run my access point using 128-bit WEP, a
non-default admin password, a non-default SSID
name, and I disallow all MACs except for those
explicitly allowed. Knowing that the DWL-1000AP
used SNMP, I performed a MIB walk to obtain the
available counters that I could monitor. In the
process I found a weakness in the product which
could potentially allow an attacker to hijack the
access point.
I first performed the MIB walk using the read-only
SNMP community of public (which was simply a
educated guess on my part, but nontheless the
default read-only community for most devices). I was
surprised to find the "admin password" (for this
example my password was "snowball") to the access
point listed in clear text in OID
1.3.6.1.4.1.937.2.1.2.2.0 as a string value. Next I
setup my SNMP utility to use "snowball" as the write
community, and I was able to reset the value stored
in that OID to any arbitrary value. A quick check by
accessing the HTTP configuration page of the
access point showed that the password was indeed
changed.
This means that anyone armed with a simple SNMP
utility which can perform read and write operations,
the read community name (which defaults to "public"
with no way to change it using D-Link's config
software), and access to the network connected to
the ethernet port of the access point could hijack the
access point and either simply configure it to allow
them access to the wireless network or completely
change the configuration and cause a denial of
service.
The only protection currently offered by the access
point against this attack is the lock access point
procedure. While this is effective, I do not believe
that it is practical. The access point may be mounted
in a hard to access area, for example, in which case
a simple configuration change would require physical
access to the device, which may be impractical in all
situations.
A more practical solution would be to give the user
the ability to set both the read-only (found in OID
1.3.6.1.4.1.937.2.1.2.1.0) and write community
names. This can currently be done, as I have tested,
by using an SNMP utility to write to the read-only
community OID. By changing that community, an
attacker would have to sniff SNMP packets accross
the network or otherwise figure out the read-only
community, a more difficult task than simply using
the default read-only community for most SNMP
devices. By giving the user the ability to control the
read-only community value through the HTTP
configuration, it would be a very simple task for that
user to change the value during the initial setup and
thus increase the security of the access point.
I realize that the most secure method is the lock
access point method. However, I believe that the
simple ability to change the read-only community
name has enough security value and is simple
enough not to be overlooked and should be integrated
into your configuration software.
-- End email --
D-Link responded with this unsatisfactory message:
-- Start email --
Dear Valued Customer,
In regards to your e-mail, I agree however the
dwl-1000 is
intended for residential use. It doesn't put of
enough wireless
signal to cause much concern of hackers. The
hacker would have to be
sitting outside you house by the window.
Thank you for your technical question and
feedback. If you are
continuing to have problems, please contact our
live support at
800-758-5489
or resubmit the problem at
http://www.dlink.com/tech/contact/.
Thank You,
D-Link US Technical Support
949-790-5290
-- End email --
I find D-Link's response to be unsatisfactory,
considering how easy it would be to allow a user to
change the read community name. Until D-Link
decides to do anything, I'd encourage anyone who
has a DWL-1000AP to use an SNMP utility to change
the read community stored in OID
(1.3.6.1.4.1.937.2.1.2.1.0).
Jonathan Strine
jstrine@netpanel.com
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