Security Advisory: Netopia R9100 DSL router

By:  Stephen Friedl (steve@unixwiz.net)
Date:  8 May 2000

Short summary:

  The Netopia R9100 permits a user not authorized with a
  special security password to neverthless modify the SNMP
  community strings, including enabling SNMP access that should
  be disabled.

Device Summary:

  The Netopia R9100 is an Ethernet-to-Ethernet router intended
  mainly for the DSL and cable modem markets, and it supports
  NAT and various kinds of tunneling. It is managed with telnet,
  HTTP, and with SNMP from either the inside or the outside
  Ethernet interfaces.

  Product information on this device can be found at:

    http://www.netopia.com/equipment/routers/r9100/

  One of the many setup screens permits the setting of SNMP
  community names, both RO and RW, and setting the entries
  to blanks effectively disables SNMP access.  The security
  setup screen (which requires a separate password from that
  used during login) can be configured to restrict access to
  any of the SNMP screens.

Vulnerability:

  The R9100 has a command-line mode that is reached by typing
  control-N after the user has passed the initial login test.
  At the "#" prompt one can then do most management of the device.
  This includes the setting of SNMP community strings in spite
  of the limitation imposed by the administrator:

    # set snmp community RO wookie
  or
    # set snmp community RW wookie

Impact:
  Relatively low. The exploit can only be attempted by those
  with existing access login to the device, and it doesn't seem
  terribly common to have users allowed to manage nearly everything
  except the SNMP strings.

Workaround:
  Deny access to users who can't be trusted.

Versions Tested:
  v4.6.2 (the latest) is the only version tested. Older
    versions probably vulnerable also.
  Other similar Netopia products possibly vulnerable also

Response from Netopia:

  The new behavior will be when SNMP access is disabled in the
  Security screen, and an attempt is made to configure the SNMP
  read-write string via the Command Line and Telnet, the user
  will get an error: -400 Access Denied.

  This fix will be in the next release of firmware, version 4.7
  (approx. end of May)

Steve

---
Stephen J Friedl|Software Consultant|Tustin, CA|  +1 714 544-6561
3B2-kind-of-guy |I speak for me only|  KA8CMY  |steve@unixwiz.net