Does the DryOS-shell allows access to the internal file systems ?

tiwe2019

Does the DryOS-shell allows access to the internal file systems ?

« on: 18 / August / 2019, 18:10:40 »

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Hello,

I want to access kernel, config and data files of my DryOS (PIXMA) system, and copy it to USB/Card or via WLAN/USB-OTG.

Therefore I had a deeper look into the visible command set of the DryOS shell, but did not found any file or mount commands (my shell access : https://chdk.fandom.com/wiki/DryOS_PIXMA_Printer_Shell). Also I wonder if there is another console next to this DryOS-shell as this seems not the native command shell to me. There is very little DryOS information around, so any tip how this OS deals with its file system would be very interesting to get forward. Thanks a lot, TiWe.

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reyalp

12686

Re: Does the DryOS-shell allows access to the internal file systems ?

« Reply #1 on: 18 / August / 2019, 20:49:45 »

Nice work on that

The Dry shell on powershots does not include filesystem access. EvShell and Canon basic do. I don't know if either exist on the printer, and I don't think either is directly accessible from dryshell on the cameras.

The task and extask commands should give you a list of running tasks.

xd and xm should allow you to execute arbitrary code, with enough work.

If you can find a firmware update for your printer, reverse engineering that might provide some useful clues. You could also likely dump your firmware slowly using xd and some scripting.

A previous printer hack was https://chdk.setepontos.com/index.php?topic=11902.0 although I'm not sure significant details were ever published.

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Don't forget what the H stands for.

tiwe2019

Re: Does the DryOS-shell allows access to the internal file systems ?

« Reply #2 on: 08 / September / 2019, 16:33:42 »

Thanks for the hints. I attach a list of all 105 DryOS commands with some explanation I gatherd. It seems to me that this shell is limited to manufacturing diagnostic. I am going forward to access the system's NOR flash and some analytics, maybe I find options to emulate system or to activate a real OS command line shell. The printer hack you mentioned I had read before also and it has in deed very little DryOS info. BR, TiWe.

DryOS-Commands v7 tx.zip (35.97 kB - downloaded 26 times.)

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reyalp

12686

Re: Does the DryOS-shell allows access to the internal file systems ?

« Reply #3 on: 08 / September / 2019, 17:42:15 »

Quote from: tiwe2019 on 08 / September / 2019, 16:33:42

Thanks for the hints. I attach a list of all 105 DryOS commands with some explanation I gatherd. It seems to me that this shell is limited to manufacturing diagnostic.

Yeah dry shell is pretty limited on powershots.

FWIW, if you can script interaction with the serial console, it seems like it shouldn't be a huge amount of effort to dump RAM/ROM that way. If you get a dump of the firmware, finding a place you can use xm execute arbitrary code should be pretty straightforward.

edit:
Saw your talk comment on the wiki. That "welcome" message on your wiki talk from me is auto-generated, we really don't use talk for much. The forum is much better for discussion. I don't think the wiki lets you attach spreadsheet files. You could link your post with the attachment from a wiki page, or host it elsewhere like a google doc.

« Last Edit: 08 / September / 2019, 23:35:36 by reyalp »

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leecher

Re: Does the DryOS-shell allows access to the internal file systems ?

« Reply #4 on: 17 / January / 2020, 05:04:20 »

During my unsuccessful search for a way to reset the waste ink counter to revive a broken printer where the ServiceTool refused to do so by telling me that the function is not available on the printer (Error 002), I wrote some simple utilities to download and unpack Canon PIXMA printer firmware. It seems that it's also using DryOS.
Maybe it's interesting for your research?
https://github.com/leecher1337/pixma

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