[OpenAFS] teardrop attack

[Jeffrey Altman]

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David:

I'm a bit puzzled.  Quoting Wikipedia "A Teardrop attack involves
sending mangled IP fragments with overlapping, over-sized payloads to
the target machine."  The goal is to trip bugs in the operating system's
IP fragment re-assembly code that can cause the machine to crash.

The vulnerable Windows versions are Windows 3.1, Windows 95, and NT4,
and Linux kernels older than 2.0.32 and 2.1.63.

Is the client machine configured to send jumbograms?

Is there some other reason that packets are being fragmented?

Given that the machines that are vulnerable to the attack
are so old, is there still a reason to turn on this protection
in the firewall?

Jeffrey Altman


David R Boldt wrote:
> 
> Recently one of our data site managers reported that
> a "teardrop attack" had occurred against one of our
> AFS file servers, as been reported by the firewall,
> and wanted us to check to make sure that nothing had
> been compromised on the server.
> 
> About two years ago one of our offices had the peculiar
> issue of not being able to copy large files into AFS
> ("large" not being well-defined). After much debugging
> we discovered that the local office firewall was seeing
> sustained AFS traffic as a teardrop attack, and would
> then automatically block the connection.  The file
> copy would time out, and the firewall seeing a reduced
> level of traffic would decide that the attack had ended
> and would reopen the connection. Copying small files did
> not trigger a firewall response.
> 
> Armed with this experience we quickly confirmed that in
> fact the teardrop attack was simply an AFS user. In this
> case the firewall equipment is a Juniper ISG2000. We have
> been told that there is no tuning available for teardrop
> attack filtering, it is either enabled or disabled for
> the entire network.
> 
> Just wanted to report this in case somebody else
> bumps into a similar issue.
> 
> 
>                     -- David Boldt
>                        <dboldt@usgs.gov>
> 
> 
>   "People who get nostalgic about childhood were obviously never children."
>    --Bill Watterson (Calvin and Hobbes)

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