Newsgroup: it.comp.sicurezza.windows
Titolo: Multiple Vulnerabilities in Alcatel ADSL Modems (lungo...)

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CERT Advisory CA-2001-08 Multiple Vulnerabilities in Alcatel ADSL
Modems
   Original release date: April 10, 2001
   Last revised: --
   Source: CERT/CC
   A complete revision history can be found at the end of this file.
Systems Affected
     * Alcatel Speed Touch Home ADSL Modem
     * Alcatel 1000 ADSL Network Termination Device
Overview
   The San Diego Supercomputer Center (SDSC) has recently discovered
   several vulnerabilities in the Alcatel Speed Touch Asymmetric
Digital
   Subscriber Line (ADSL) modem. These vulnerabilities are the result
of
   weak authentication and access control policies and exploiting them
   will lead to one or more of the following: unauthorized access,
   unauthorized monitoring, information leakage, denial of service,
and
   permanent disability of affected devices.
   The SDSC has published additional information regarding these
   vulnerabilities at
 
http://security.sdsc.edu/self-help/alcatel/
I. Description
   VU#211736 - Alcatel ADSL modems grant unauthenticated TFTP access
via
   Bounce Attacks
   Alcatel ADSL modems allow unauthenticated Trivial File Transfer
   Protocol (TFTP) access from the local area network (LAN) as a
method
   to update firmware and to make configuration changes to the device.
In
   conjunction with one of several common vulnerabilities, a remote
   attacker may be able to gain unauthenticated access as well.
   For example, if a system on the LAN side of the ADSL modem has the
UDP
   echo service enabled, a remote attacker may be able to spoof
packets
   such that the ADSL modem will believe that this traffic originated
   from the local network. By sending a packet to the UDP echo service
   with a spoofed source port of 69 (TFTP) and a source address of
   255.255.255.255, the system providing the echo service can be
tricked
   into sending a TFTP packet to the ADSL modem. If a system offering
   this service is accessible from the Internet it may be possible to
use
   the system to attack the ADSL modem.
   Any mechanism for "bouncing" UDP packets off systems on the LAN
side
   of the network may potentially allow a remote attacker to gain TFTP
   access to the device. Gaining TFTP access to the device allows the
   remote attacker to essentially gain complete control of the device.
   VU#243592 - Alcatel ADSL modems provide EXPERT administrative
account
   with an easily reversible encrypted password
   Alcatel ADSL modems contain a special account (EXPERT) for gaining
   privileged access to the device. This account is secured via a
   challenge-response password authentication mechanism. While the use
of
   such a mechanism is commendable, the algorithm used is not
   sufficiently strong. Attackers who know the algorithm used to
compute
   the response can compute the correct response using information
given
   to them during the login process.
   Because the EXPERT account is accessible via TELNET, HTTP, and FTP,
   the ADSL modem must have an IP address that is accessible from the
   Internet to exploit this vulnerability. Alcatel ADSL products do
not
   enable this feature over the wide area network (WAN) interface by
   default. Note however, that an attacker with TFTP access may be
able
   to reconfigure the device to enable this feature.
   This authentication mechanism is present even if the user has set a
   user supplied password.
   Any problem or vulnerability on your internal network that allows
an
   intruder to communicate with the modem may lead to its compromise,
   including Trojan horses, compromised systems, or other "bounce"
   vulnerabilities like the FTP bounce vulnerability described in
 
http://www.cert.org/tech_tips/ftp_port_attacks.html
   VU#212088 - Alcatel ADSL modems contain a null default password
   The Alcatel Speed Touch ADSL modem ships with a null default
password,
   permitting unauthenticated access via TELNET, HTTP, and FTP. As
with
   the EXPERT account vulnerability, the device must have an
externally
   accessible IP address. 
   VU#490344 - Alcatel ADSL modems provide unauthenticated TFTP access
   via physical access to the WAN interface
   To allow your ISP to upgrade the firmware of the ADSL modem
remotely,
   unauthenticated TFTP access is provided to users with physical
access
   to the wire on the WAN side of the modem. While this access is
   normally used by your ISP, it could also be abused by an attacker
with
   physical access to the wire outside of your home.
II. Impact
   VU#211736 - Alcatel ADSL modems grant unauthenticated TFTP access
via
   Bounce Attacks
   A remote attacker may be able to gain access to perform TFTP
   operations. These operations include
     * inspection of configuration data
     * recovery and setting of passwords
     * inspection and updates to the firmware
     * destructive updates to the firmware
     * malicious custom updates to the firmware
   Note that the Alcatel ADSL modems do not provide any mechanism for
   determining the validity of firmware updates, so a remote attacker
may
   be able to install custom firmware that operated as a distributed
   denial of service client or a network sniffer. Similarly, an
attacker
   could produce an invalid firmware revision that would disable the
   device completely, leaving victims no alternative but to return the
   disabled unit to the manufacturer. 
   VU#243592 - Alcatel ADSL modems provide EXPERT administrative
account
   with an easily reversible encrypted password
   Attackers who are able to connect to the ADSL modem can enter a
   predictable user ID and password to gain privileged access to the
   device. This access can be used to reconfigure the device,
potentially
   introducing additional security weaknesses. 
   VU#212088 - Alcatel ADSL modems contain a null default password
   Unless the user or Internet service provider changes the default
   password of an affected device, a remote attacker can access the
modem
   via TELNET, HTTP, or FTP. In the case of TELNET and HTTP, this
   vulnerability grants the attacker read and write access to device
   configuration. For FTP, this vulnerability allows the attacker to
   browse the file structure of the affected device. 
   VU#490344 - Alcatel ADSL modems provide unauthenticated TFTP access
   via physical access to the WAN interface
   An attacker with physical access to your wire may be able to gain
   unauthenticated TFTP access to the device with the same impacts as
   described in the "bounce" vulnerability (VU#211736).
III. Solution
Set a password for your ADSL modem
          Because the Alcatel ADSL modems ship without a password by
          default, an attacker may be able to gain access if this
          password has not been set. Users are encouraged to set a
          password when the device is first configured. This solution
          does not protect you from all of the vulnerabilities
described
          above. In particular, a user supplied password does not
prevent
          the use of the EXPERT account.
Block malicious traffic at your network perimeter
          If you have a home firewall product you may be able to
prevent
          the TFTP UDP bounce attack by filtering one or more of the
          following types of traffic:
          + packets with spoofed source addresses
          + packets with a source address of 255.255.255.255
          + packets with a destination port of echo (or other "simple"
            services)
          Note that intruders who are able to gain access to your
local
          area network may be able to gain unauthenticated TFTP access
          using mechanisms other than the TFTP UDP bounce method.
Appendix A. - Vendor Information
   This appendix contains information provided by vendors for this
   advisory. When vendors report new information to the CERT/CC, we
   update this section and note the changes in our revision history.
If a
   particular vendor is not listed below, we have not received their
   comments.
Alcatel
          ALCATEL SPEED TOUCH ADSL MODEM SECURITY INFORMATION
          About security of Modems and Networks
          Security issues can be divided into two main areas: network
          security and user security, more particularly user's content
          security.
          Wide Area Network (WAN) security is about protecting a
network
          from malicious usage. Security can be guaranteed at all
network
          levels except at Customer Premise Equipment (CPE), since
such
          equipment is not directly controlled by an Operator or an
ISP.
          This is true for any type of CPE, such as telephones,
analogue,
          DSL or cable modems and fax machines. Security can only be
          guaranteed at the network level for an Operator's, ISP's or
          private network. This means that a network should stay
          operational at all times. Alcatel has built this type of
          security in its DSLAM (operated by the service provider).
          User security is about protecting the content and local area
          network of an end-user. This type of security has to be
          implemented on Local Area Network (LAN) or PC level at
customer
          premises.
          This is standard practice for any network connection (leased
          lines, cable modem, DSL). Such modems provide connectivity
not
          security. Security of content for the user can be reinforced
at
          the LAN level by installing a dedicated firewall HW/SW,
either
          on the server or on the PC or by installing a dedicated
          firewall device, although Alcatel provides also DSL modems
          which have firewall security Statement. Private and LAN
          security is in the responsibility of the user.
          There are many soft and hardware products on the market to
          ensure security, including those from Alcatel.
          Modem security
          Firstly, people have been able to alter firmware on the
modem.
          This is a standard feature foreseen in some of the Speed
Touch
          modems to allow SW upgrades locally or remotely. Access from
          the LAN interface into the modem is not a security problem,
          since the modem belongs to the person who is using it.
However,
          via a protection mechanism a feature is foreseen so that
nobody
          can do that remotely (or via the WAN/DSL interface). This
          protection mechanism guarantees that nobody from outside can
          access the modem and make changes.
          This protection can be switched off locally by the modem
owner,
          in case the service provider wants to do upgrades. This
process
          is normally managed by the service provider, and the service
          provider explains to the end-user how to disactivate the
          protection and re-activate again. To avoid security
problems,
          this feature is not explained in the user manual.
          Alcatel ships all modems with the protection activated,
          however, it's easy for a modem owner to disactivate the
          protection, since this is documented on the Alcatel website.
          However, if a user disactivates this, he's also responsible
for
          activating it again.
          Secondly, the method of getting into the modem is more
advanced
          and it is a standard practice used by hackers. The way it
works
          is that they fake local communication via the WAN interface
by
          using an ECHO port on a UNIX server connected to LAN
network.
          The modem assumes communication comes from the modem owner
and
          is secure. However, this is an old security problem in all
data
          communication networks and is solved by means of a firewall.
          Firewall's are standard practice for each well managed
          communication network. Recommendation that Alcatel gives is
to
          install a dedicated firewall or firewall software, or make
use
          of the Alcatel Speed Touch modem with Firewall capabilities.
          (See URL: 
http://www.alcatel.com/consumer/dsl/prodprofw.htm
)
     _________________________________________________________________
   The CERT Coordination Center would like to thank Tom Perrine and
   Tsutomu Shimomura of the San Diego Supercomputer Center for
notifying
   us about this problem and their help in constructing this advisory.
     _________________________________________________________________
   Authors: This document is based on research by the SDSC and was
   written by Cory Cohen, Jeffrey P. Lanza, and John Shaffer.
______________________________________________________________________
   This document is available from:
 
http://www.cert.org/advisories/CA-2001-08.html
______________________________________________________________________
CERT/CC Contact Information
   Email: 
ce...@cert.org
          Phone: 
+1 412-268-7090
 (24-hour hotline)
          Fax: 
+1 412-268-6989
          Postal address:
          CERT Coordination Center
          Software Engineering Institute
          Carnegie Mellon University
          Pittsburgh PA 15213-3890
          U.S.A.
   CERT personnel answer the hotline 08:00-20:00 EST(GMT-5) /
EDT(GMT-4)
   Monday through Friday; they are on call for emergencies during
other
   hours, on U.S. holidays, and on weekends.
Using encryption
   We strongly urge you to encrypt sensitive information sent by
email.
   Our public PGP key is available from
 
http://www.cert.org/CERT_PGP.key
   If you prefer to use DES, please call the CERT hotline for more
   information.
Getting security information
   CERT publications and other security information are available from
   our web site
 
http://www.cert.org/
   To subscribe to the CERT mailing list for advisories and bulletins,
   send email to 
majo...@cert.org
. Please include in the body of
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   message
   subscribe cert-advisory
   * "CERT" and "CERT Coordination Center" are registered in the U.S.
   Patent and Trademark Office.
______________________________________________________________________
   NO WARRANTY
   Any material furnished by Carnegie Mellon University and the
Software
   Engineering Institute is furnished on an "as is" basis. Carnegie
   Mellon University makes no warranties of any kind, either expressed
or
   implied as to any matter including, but not limited to, warranty of
   fitness for a particular purpose or merchantability, exclusivity or
   results obtained from use of the material. Carnegie Mellon
University
   does not make any warranty of any kind with respect to freedom from
   patent, trademark, or copyright infringement.
     _________________________________________________________________
   Conditions for use, disclaimers, and sponsorship information
   Copyright 2001 Carnegie Mellon University.
   Revision History
April 10, 2001:  Initial release


Newsgroups: it.comp.sicurezza.varie
Subject: Re: [REQ - INFO] Backdoor Alcatel
Date: Wed, 11 Apr 2001 08:46:01 GMT
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