D-Link Access Point DWL-900AP+ TFTP Vulnerability

[<security () rionero com>]

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ETHEREANET-NCC Security Report EN-NCC-20021014-04
D-Link Access Point DWL-900AP+ TFTP Vulnerability

Date discovered:    Fri, 11 Oct 2002
Vendor notified on: Mon, 14 Oct 2002
Date published:     Mon, 21 Oct 2002

Vendor Reference:   D-Link US Support Case-ID DL204488
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Overview
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While evaluating the D-Link DWL-900AP+ Access Point/Bridge, we
discovered a severe vulnerability that could be exploited by a
potential intruder to gain full administrative access to the device.


Description
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D-Link's DWL-900AP+ is a WiFi/802.11b Access Point with enhanced
22Mbps transfer mode (aka "802.11b+") and proprietary bridging
functions, tipically targeted at SOHO installation.
The device can be connected to an existing wired network by mean of
a standard 10/100 ethernet port and can be configured by using a
javascript-enabled HTTP client (WEB browser) pointed at its IP
address.

Although undocumented, the device features also an embedded TFTP
(Trivial File Transfer Protocol) server which can be used to obtain
critical data: by requesting a file named "config.img", an intruder
receive a binary image of the device configuration which contains,
among others, the following informations:

  - the "admin" password required by the HTTP user interface
  - the WEP encryption keys
  - the network configuration data (addresses, SSID, etc.)

Such data are returned in cleartext and may be accessed by any
wired/wireless client. Note that if the device is configured to use a
"public" IP address and a valid "gateway" (connected to the Internet)
is specified in the wired LAN configuration screen, the TFTP service
(hence the crititical data) could be accessed world-wide.


Additional info
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In addition to the above mentioned "config.img", the following
undocumented files are also accessible via the TFTP protocol:

  - eeprom.dat
  - mac.dat
  - wtune.dat
  - rom.img
  - normal.img

the latest one being the (compressed) firmware image as uploaded to
the device. We did not investigate further, so the above list is to
be intended as NOT exaustive.


Tested devices
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Model No: DWL-900AP+ (FCC-ID: KA2DWL900AP-PLUS)
H/W:      B1
F/W:      2.1 & 2.2

The vulnerability has been observed with both 2.1 & 2.2 firmware
revisions.


Solutions
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There are NO known solutions or workarounds at the moment. A firmware
upgrade is urged from the vendor. A complete report of the
vulnerability was sent to D-Link's International Support
<techs () dlinksupport com> on Mon, 14 Oct 2002 and was assigned
the case-id: DL204488.


Discovered by
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Rocco Rionero, <rock () rionero com>


Note about potentially affected re-branded devices (NOT VERIFIED)
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The DWL-900AP+ appears to be based on a device originally developed
by "Global Sun Technology Inc.": as the same device is also sold with
other brands, the vulnerability MAY apply to any of them. Potentially
affected devices include the following access points:

  - ALLOY GL-2422AP-S
  - EUSSO GL2422-AP
  - LINKSYS WAP11-V2.2
  - WISECOM GL2422AP-0T

Please, note: NONE of the above was tested.


Disclaimer
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All information in this report are subject to change without any
advanced notices neither mutual consensus; the report itself is
released as it is. Neither the author, nor the parts (if any)
involved in the distributions of this report are responsible for any
risks of occurrences caused by applying the information included.


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ETHEREANET Control Center <ncc () ethereanet net>
ETHEREANET Security Administration <security () ethereanet net>
RIONERO Network Security Administration <security () rionero com>