OSEC

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From: Steven Griffin (sgriffinBAYSTARCAPITAL.COM)
Date: Tue Mar 27 2001 - 14:34:20 CST

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    I have recently found a bug in the latest firmware
    (6.0.0.0) of SonicWall's Tele2 and SOHO firewalls.

    Product details:
    http://www.sonicwall.com/products/tele/details.html
    http://www.sonicwall.com/products/soho/details.html

    Bug disovery:
    I was recently configuring the Tele2 and SOHO
    versions of these firewalls in a gateway to gateway
    VPN using IPSec with IKE pre-shared keys. The
    home office gateway was a Cisco PIX 520 running
    the PIX OS 5.2(4). The Tele2 and SOHO firewalls
    were recently upgraded to the 6.0.0.0 firmware.
    The IPSec configuration was ESP-3DES ESP-MD5-
    HMAC. During my configuration setup I noticed that I
    could not configure an IKE pre-shared key longer
    than 48 bytes. Doing so caused the the 2nd phase
    IKE negotiation to fail on the PIX.

    I contacted the vendor (SonicWall) and reported the
    problem. They have replicated the problem and
    confirmed that it is indeed a bug in their firmware.
    I asked them for permission to inform BugTraq and
    they responded that it was indeed alright to post this
    here provided that I inform you that I found the bug
    and that to say that they will provide a fix for this
    problem as soon as possible.

    Security concern:
    Obviously the limitation of using only a 48 byte key
    as opposed to using a full 128 byte key degrades the
    overall security of the firewall.

    Workarounds:
    Do not use pre-shared keys. Use certificates, your
    own or from a third party CA, instead.

    If you must use pre-shared keys:
      Use only static gateway addresses if possible.
      Use a different key for each gateway.
      Turn on Perfect Forwared Secrecy.
      Set your key expiration time to a shorter interval.

    Configuration information for duplication:
    note: IP Addresses have been removed.

    PIX 520 with OS 5.2(4) relavant config:
    access-list 119 permit ip xxx.xxx.xxx.xxx
    xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx
    access-list nonat permit ip xxx.xxx.xxx.xxx
    xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx xxx.xxx.xxx.xxx

    sysopt connection permit-ipsec
    sysopt ipsec pl-compatible

    crypto ipsec transform-set SonicFirewall esp-3des
    esp-md5-hmac
    crypto map Sonic-map 19 ipsec-isakmp
    crypto map Sonic-map 19 match address 119
    crypto map Sonic-map 19 set peer xxx.xxx.xxx.xxx
    crypto map Sonic-map 19 set transform-set
    SonicFirewall
    crypto map Sonic-map interface outside

    isakmp enable outside
    isakmp key <48-byte key here> address
    xxx.xxx.xxx.xxx netmask xxx.xxx.xxx.xxx
    isakmp identity address
    isakmp policy 19 authentication pre-share
    isakmp policy 19 encryption 3des
    isakmp policy 19 hash md5
    isakmp policy 19 group 1
    isakmp policy 19 lifetime 28800

    SonicWall with firmware 6.0.0.0
    Note: sonicwall config is web based so I will post
    field names. datatypes in square brackets "[ ]" and
    field values after a colon ":" IP addresses have also
    been removed.

    Summary Tab:
    Enable VPN checkbox: Checked
    Disable all VPN Windows Networking (NetBIOS)
    broadcast [checkbox]: UnChecked
    Enable Fragmented Packet Handling [checkbox]:
    Checked

    Configuration Tab:
    Security Association [drop-down listbox]: SonicToPIX
    IPSec Keying Mode [drop-down listbox]: IKE using
    pre-shared secret
    Name [textbox] SonicToPix
    Disable This SA [checkbox]:UnChecked
    IPSec Gateway Address [textbox]:xxx.xxx.xxx.xxx
    Require XAUTH/RADIUS(only allows VPN clients)
    [checkbox]:UnChecked
    Enable Windows Networking (NetBIOS) broadcast
    [checkbox]:Checked
    Enable Perfect Forward Secrecy
    [checkbox]:UnChecked
    SA Life time (secs) [textbox]:28800
    Encryption Method [drop-down listbox]:Strong
    Encrypt and Authenticate (ESP 3DES HMAC MD5)
    Shared Secret [textbox]:<48-byte key here>
    Destination Networks: [sub window]:
            IP Address [textbox]:xxx.xxx.xxx.xxx
            SubnetMask [textbox]:xxx.xxx.xxx.xxx

    Disclaimer and closing:
    I must say that I am not a security expert and I do not
    claim to be one. My opinions are my own. Use my
    opinions and the information in this posting at your
    own risk. My intention for posting this information is
    to inform the BugTraq community about a possible
    security concern.

    Steven Griffin
    sgriffinbaystarcapital.com