PW4 Can OTA update package be modified?

tinman1 · 09-16-2022, 07:21 AM

Hi All,

I have been reading this forum for a few months now and it has been really useful for successfully jail breaking my Kindle so thanks very much for all your help.

I have been trying to modifying the OTA update packages available from amazon using KindleTool.

My Kindle has fw 5.11.2 and is jailbroken. I am trying to modify update_kindle_all_new_paperwhite_v2_5.13.7.bin.

So far I have extracted it using KindleTool and modified the rootfs.img.gz file. I then repacked it using the cmd:

./kindletool create recovery2 -c 0 -1 2048630901 -2 1897089723 -m 1 -p rex -b FB03 -d pw4lg imx6s11_rex/* rootfs.img.gz ../update_kindle_all_new_paperwhite_v2_5.13.7-mod.bin

I copy the .bin file to the Kindle root folder and reboot. The update fails with ERROR 4 and dmesg logs that the key length is incorrect (256 not 128). I have also tried it with the prod keys (-c 1 and -c 2) and with omitting the magic numbers and that also failed. I have also tried with 'Update Kindle' but that is always grayed out and also with MRPI.

Does anyone know if this is likely to be an error with my KindleTool args or if this is something that just can't be done on a PW4?

NiLuJe · 09-16-2022, 12:02 PM

You can't run custom recovery packages without also patching the initrd to accept your signing key.

The only practical example of that ever having been done was in @yifanlu's FW 3.x-on-the-DX thingy, IIRC (which predates KindleTool, but the concept is still the same).

(Also, as the error says, current initrds *require* a 2K signing key, while our OTA JB key is 1K, because that's the length required for the dev key slot. IIRC, there's only one 2K slot: 2).

tinman1 · 09-16-2022, 12:28 PM

Thanks for your quick reply.
I'll take a look @yifanlu's thingy although I think I might be in a chicken-egg situation here as the reason I was looking to update the OTA package was because I think serial access is blocked on the PW4 so patching initrd may not be feasible.

NiLuJe · 09-16-2022, 03:36 PM

Indeed, this is not usable as a JB vector because it requires software modification (at least it's not usable as in entry point vector)

.

09-16-2022, 07:21 AM	#1
tinman1 Junior Member Posts: 2 Karma: 10 Join Date: Sep 2022 Device: pw4	Can OTA update package be modified? Hi All, I have been reading this forum for a few months now and it has been really useful for successfully jail breaking my Kindle so thanks very much for all your help. I have been trying to modifying the OTA update packages available from amazon using KindleTool. My Kindle has fw 5.11.2 and is jailbroken. I am trying to modify update_kindle_all_new_paperwhite_v2_5.13.7.bin. So far I have extracted it using KindleTool and modified the rootfs.img.gz file. I then repacked it using the cmd: ./kindletool create recovery2 -c 0 -1 2048630901 -2 1897089723 -m 1 -p rex -b FB03 -d pw4lg imx6s11_rex/* rootfs.img.gz ../update_kindle_all_new_paperwhite_v2_5.13.7-mod.bin I copy the .bin file to the Kindle root folder and reboot. The update fails with ERROR 4 and dmesg logs that the key length is incorrect (256 not 128). I have also tried it with the prod keys (-c 1 and -c 2) and with omitting the magic numbers and that also failed. I have also tried with 'Update Kindle' but that is always grayed out and also with MRPI. Does anyone know if this is likely to be an error with my KindleTool args or if this is something that just can't be done on a PW4?

09-16-2022, 12:02 PM	#2
NiLuJe BLAM! Posts: 13,480 Karma: 26012494 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w, PW, PW2, PW5; Kobo H2O, Forma, Elipsa, Sage, C2E	You can't run custom recovery packages without also patching the initrd to accept your signing key. The only practical example of that ever having been done was in @yifanlu's FW 3.x-on-the-DX thingy, IIRC (which predates KindleTool, but the concept is still the same). (Also, as the error says, current initrds require a 2K signing key, while our OTA JB key is 1K, because that's the length required for the dev key slot. IIRC, there's only one 2K slot: 2). Last edited by NiLuJe; 09-16-2022 at 12:07 PM.

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09-16-2022, 12:28 PM	#3
tinman1 Junior Member Posts: 2 Karma: 10 Join Date: Sep 2022 Device: pw4	Thanks for your quick reply. I'll take a look @yifanlu's thingy although I think I might be in a chicken-egg situation here as the reason I was looking to update the OTA package was because I think serial access is blocked on the PW4 so patching initrd may not be feasible.

09-16-2022, 03:36 PM	#4
NiLuJe BLAM! Posts: 13,480 Karma: 26012494 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w, PW, PW2, PW5; Kobo H2O, Forma, Elipsa, Sage, C2E	Indeed, this is not usable as a JB vector because it requires software modification (at least it's not usable as in entry point vector) .

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