RE: Firewall comparison in Data Communications

David T. Smith (dsmithuswebcks.com)
Wed, 02 Jun 1999 07:07:16 -0400

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At 08:17 AM 5/31/99 -0400, Brian Steele wrote:
><newbie-mode>What's a "source-routed packet"? And what danger does it pose
>to a Firewall?</newbie-mode>
>
>Brian
>
>

In brief, a source routed packet is an IP packet that includes its own
routing information. If you enable source-routed processing then you are
supposed to reply to the packet with the same route as it sent you:

The wily hacker creates a packet

TO: HQ.corp.com
FR: field.corp.com
Source-route option: wily.hacker.hack
<<Packet innards>>

With source routing turned on the reply goes:

To: Field.corp.com
Fr: HQ.corp.com
Source-route option: wily.hacker.hack
<<packet innards>>

And you have a man in the middle. Wily can simply masquerade as field and
be trusted by HQ.

DTS
D A V I D T . S M I T H
Principal Consultant, Network Solutions
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