Parsing extracted i.MX NAND flash

[Rogan Dawes]

On Thu, Nov 21, 2024 at 12:42:16PM +0800, Zhihao Cheng wrote:
> ? 2024/11/20 23:51, Rogan Dawes ??:
> > On Mon, Nov 18, 2024 at 07:39:39PM +0200, Rogan Dawes wrote:
> >> Hi folks,
> >>
> >> I have an i.MX6 target I am trying to get a shell on. It is using High
> >> Assurance Boot and various other configurations to prevent this. My
> >> current approach is to remove the flash, extract the filesystems, modify
> >> one that is not subject to HAB, then put it all back, in order to enable
> >> a shell.
> >>
> >> I have removed the flash, and extracted its contents using an Xgecu
> >> flash reader. Now I need to parse the FCB and extract the actual data
> >> from the dump. I have found imx-nand-tools, but this doesn't work due to
> >> bitrot (the bchlib dependency has moved on while imx-nand-tools has not
> >> been updated).
> > 
> > I was able to get imx-nand-tools working by pinning the version of the
> > bchlib dependency to v0.14.0, and have been able to obtain a "clean"
> > flash image. Still trying to mount the various UBI filesystems, as I get
> > the following errors:
> > 
> > [360972.710050] ubi0: default fastmap pool size: 8
> > [360972.710055] ubi0: default fastmap WL pool size: 4
> > [360972.710056] ubi0: attaching mtd5
> > [360972.710099] ubi0 error: validate_ec_hdr [ubi]: bad VID header offset 2048, expected 512
> 
> Hi Rogan,
> How did you use ubiattach? ubiattach -O 512?  Try 'ubiattach -O2048'.

Hi,

I simply ran it without any specific offset options:

sudo ubiattach -m 5

which produced the panic in my previous mail..

If I try with -O 2048, this is what I get:

$ sudo ubiattach -O 2048 -m 5
[sudo] password for rogan:
ubiattach: error!: cannot attach mtd5
           error 22 (Invalid argument)

[614006.620517] ubi0: default fastmap pool size: 8
[614006.620520] ubi0: default fastmap WL pool size: 4
[614006.620521] ubi0: attaching mtd5
[614006.620749] ubi0: scanning is finished
[614006.620787] ubi0 error: vtbl_check [ubi]: bad CRC at record 11: 0xc8e5abb1, not 0xf116c36b
[614006.620816] Volume table record 11 dump:
[614006.620818] 	reserved_pebs   0
[614006.620819] 	alignment       0
[614006.620820] 	data_pad        0
[614006.620821] 	vol_type        0
[614006.620834] 	upd_marker      0
[614006.620835] 	name_len        0
[614006.620836] 	name            NULL
[614006.620838] ubi0 error: vtbl_check [ubi]: bad CRC at record 11: 0xc8e5abb1, not 0xf116c36b
[614006.620848] Volume table record 11 dump:
[614006.620849] 	reserved_pebs   0
[614006.620850] 	alignment       0
[614006.620851] 	data_pad        0
[614006.620852] 	vol_type        0
[614006.620852] 	upd_marker      0
[614006.620853] 	name_len        0
[614006.620854] 	name            NULL
[614006.620855] ubi0 error: process_lvol [ubi]: both volume tables are corrupted
[614006.620872] ubi0 error: ubi_attach_mtd_dev [ubi]: failed to attach mtd5, error -22

Regards,

Rogan