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 Post subject: Forensics Analysis of a Flashdrive's NAND raw image
PostPosted: February 21st, 2021, 17:12 
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Joined: February 21st, 2021, 16:37
Posts: 2
Location: Europe
Hello folks,
I am an incident responder that as everyone else under lockdown is looking for some hobby to pass the time :)

For testing purposes, I took a new 128MB flashdrive that mounts a NAND flash, formatted in FAT32, added some testing files (i.e. PDF, DOC, MP3, M4,etc).
Afterwards, I removed the NAND with a hotair gun and successfully made a raw dump of it with a FT2232H + TSOP48 adaptor.

At this point I was thinking to remove the OOB data and I will endup with a FAT32 image that I can easily mount either on Win (FTK Imager) or on Linux.
But I was kinda wrong.

My gut feeling is that the NAND's content is somehow XORed by the flashdrive controller.

Does someone have more literature or eventually opensource tools that may give me more insights on:
- How to approach the analysis of a raw dump from a flashdrive?
- How to analyze this raw dump?
- How to figure out the type of "weak encryption used"?

Image


Usually, for embedded devices... I simply dump the NAND, remove the OOB and try to decompress the FS used (i.e. UBIFS, JFFS2, etc.)
But in this case I feel lost with this thingy of having a controller in the middle that XORs the data.
I am aware that there are commercial tools able to automatically analyze the "encrypted" data and return the files in the FS... but my purpose here is rather to learn and work on a FOSS tool to achieve similar point.


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 Post subject: Re: Forensics Analysis of a Flashdrive's NAND raw image
PostPosted: February 23rd, 2021, 18:58 
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Joined: October 3rd, 2005, 0:40
Posts: 3441
Location: Hungary
as you said there might be xor (it is not possible to tell by the pic you linked, coz that's just the area containing the usb descriptor looking stuff), but the content is 'shuffled' too as a result of write leveling.
It is never a single click solution. As i said in the other post.

pepe

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 Post subject: Re: Forensics Analysis of a Flashdrive's NAND raw image
PostPosted: February 23rd, 2021, 19:06 
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Joined: September 8th, 2009, 18:21
Posts: 13017
Location: Australia
Could you upload the image, including the OOB data? I would be interested in learning something as well. :-)

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 Post subject: Re: Forensics Analysis of a Flashdrive's NAND raw image
PostPosted: February 24th, 2021, 10:52 
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Joined: May 13th, 2019, 7:50
Posts: 280
Location: Nederland
https://youtu.be/MKC_Xl5sP6Y

http://adreca.net/NAND-Flash-Data-Recovery-Cookbook.pdf

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