
Secrets of the Medtronic MyCareLink Patient Monitor - jstanley
http://incoherency.co.uk/blog/stories/medtronic-mycarelink.html
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alphaoverlord
The mycarelink is the interface for an implantable loop recorder. That is a
small flash card sized device implanted in the chest for long term ecg
monitoring. This is not a pacemaker or a defibrillator but rather only
monitors the heart long term. It is frequently used for patients to identify
rare arrhythmias, often in the setting of unexplained fainting. This device is
purely sensing and does not have the ability to pace or shock the heart.

~~~
jstanley
Thanks! I've added an update now.

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Dwolb
OP what type of Huawei dongle is it? If it's one of the old Hi Link modems,
maybe this tutorial would work:
[https://hologram.io/docs/guide/connect/e303](https://hologram.io/docs/guide/connect/e303)

Otherwise it could be a newer MS-2131i which requires a little more
configuration.

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jstanley
It's a "K3773" as far as I can tell.

I was actually trying to use it from inside the Medtronic system, after the
graphical depictions had indicated that it had connected OK, so I'm reasonably
confident the software side was setup correctly. I just couldn't connect to
anything.

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tomrod
> Aha! So this mysteriously-named /usr/sbin/eis3920 program is responsible for
> the decryption. eis3920 is an ARM binary, but running strings on it came up
> with some items of interest:
    
    
        ...
        /sys/devices/platform/omap/omap_i2c.2/i2c-2/2-0057/eeprom
        %s%s%s%s%s
        /home/root
        .ecryptfs
        sig-cache.txt
        ecryptfs_fnek_sig=
        %s%s%s%s%s%s%s%s%s%s%s%s
        mount -t ecryptfs 
    

I'm at a bit of a loss here. What does he mean by "running strings on it"?

~~~
JshWright
It's a program that spits out all the printable strings from a binary file.

[https://en.wikipedia.org/wiki/Strings_(Unix)](https://en.wikipedia.org/wiki/Strings_\(Unix\))

EDIT: lol... we're all so helpful (4 replies all at '0 minutes ago' at the
moment)

~~~
tomrod
THIS! This is why I love hacker news. Much thanks for the pointer. I've never
actually used (or, I believe, needed to directly use) strings before. Thanks
so much.

~~~
_joel
Please be careful when running strings, if possible, don't, as it can be used
as an attack surface. Just take a look at CVE-2014-8485 if you need
clarification.

~~~
tomrod
Thank you for the heads up.

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brokenmachine
Thanks for the interesting writeup.

I loved the idea of getting the crypt key off the eeprom by editing the mount
script to log it's own arguments. Very tricky!

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trdtaylor1
Excellent writeup OP. It's great to see the same linux technology underpinning
everything in the world around us.

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valine
Great writeup. I interned for Medtronic and got to work on a web interface for
the clinician side of a CareLink like project. It's encouraging that some
energy was put into securing the monitor. Medical device companies get a bad
rap when it comes to security.

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intransigent
Pffft!

Astounding to see that some goofballs took the time to encrypt an SD card
partition, and then hide the password in immediate proximity to the ostensibly
secured resource.

Thumb to the wind, and the author MITM'd it in minutes?

Ah well, I suppose it's better to anticipate the SD card becoming separated
from the device chassis with the original eeprom password or some such blah
blah blah.

Strap yourselves in for what the future holds.

Internet of things, hurr dee durr...

