RE: A more detailed description of the Jura F90 vulnerability.

Have you shared all of this with the manufacturer first?


-----Original Message-----
From: Craig Wright [mailto:Craig.Wright@xxxxxxxxxx]
Sent: Tuesday, June 17, 2008 11:10 PM
To: security-basics@xxxxxxxxxxxxxxxxxxxxxxx; bugtraq@xxxxxxxxxxxxxxxxx
Subject: A more detailed description of the Jura F90 vulnerability.

The issue is a lack of input validation. OWASP would be a great
learning exercise for the coders on this product. It seems to be
assumed that only trust-worthy users will connect only to trust-worthy
sites. I could not find any evidence of input validation.

Through the magic of Web Scarab and Paros proxy, one can capture the
Internet communications used by the F90 Internet Connection Kit
software. What you soon see is that the software does not account for
either bypassing the local application and changing the input or in
spoofed and re-directed sites.

The software does not validate the site it gets the information from
nor does it sufficiently validate the input to the software.

At the moment as I think there are so few people as crazy as I am who
actually have to have a gadget just as it is Internet connected; this
is not likely to become a widespread attack vector.

The software is an oversized web proxy with other stuff to connect to
the coffee machine thrown in. Jura did not make the assumption that an
evil attacker could purposefully modify and publish "evil" coffee

I have been taking the updated SANS@Home 610 course. I have a GREM,
Lenny and the other guys have added an additional component to the
Reverse Engineering Malware Course. So I had to take it.

The course focuses on analysing and reversing malware, but IDA and
work on binaries of all types and the bad combination of a bottle of
good resiling and 9 coffees after midnight is not a good combination.
Hence I decided to attack my coffee maker and the control software.

There are certain aspects of code (like the ever faithful GETS()
function) that should be beaten from existence. Others need to be
securely configured such that all the required variable fields are
entered correctly (see SPRINTF()). Unfortunately the coders at Jura
not consider that "bad people" would ever attack a coffee maker ;).

There are 2 main attacks that I have noted,
1 Loading a malicious setting or recipe into the device causing
"coffee overflow" etc.
2 More seriously, not validating the input correctly coupled
a lack of authorisation of the source and nothing to stop invalid data
at the host means that malformed strings can be fed to the software
that can either crash the system or if crafted correctly run a binary
on the host.

So, as most people who check this list I no doubt know, not validating
input is bad. Trusting the web as you have a piece of custom software
that is closed source and a belief that users are all nice is bad.

Craig Wright GSE-Compliance

PS for DMCA compliance reasons I would state that I was not reversing
the software, but rather inputting unusual coffee recipes that had a
strange binary flavour ;)

Craig Wright
Manager, Risk Advisory Services

Direct : +61 2 9286 5497
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