Playing around with u-boot_mod under LEDE

For Developers
1

Dear friends,

I would like to play around with uboot on a WDR-3600v1 to provide a completely free solution around LEDE. I am concerned that there might be backdoors in some bootloaders. This is quite a concern for companies.

At first, I would like to be able to flash a fresh uboot on my WDR3600 using;

However, the uboot mtd seems to be read-only (which is good for security). However, do you know how to flash it. Should you also port uboot mtd from OpenWRT to LEDE?

Kind regards,

2

You are correct, standard release OpenWrt/LEDE builds do not allow flashing of the u-boot mtd, as a precaution.

To flash u-boot, you either

  • need a OpenWrt/LEDE build that has this restriction disabled or build one yourself
  • use the old u-boot to flash a new one -- this is more cumbersome because you need to go in via UART/serial, and I believe it's not always possible because some of the manufacturers' u-boots are restricted and/or stripped down

pepe2k himself did the work on the former option already. https://github.com/pepe2k/u-boot_mod/releases has a big archive containing an (now older) OpenWrt 14.07 you can temporarily flash on your router that allows u-boot flashing and even comes with helper scripts to achieve it. Yes, your WDR3600 is included.

3

Thanks takimata. I was going to either rebuild my own firmware or use OpenWRT and will keep you informed.


Starting from official release "2014-11-19", you will find ready OpenWrt images, with unlocked u-boot
partition, embedded U-Boot image and dedicated small script for easy
update process inside release tarball. All you need to do is download
last release, select proper OpenWrt image for your device, install it
and invoke one command: u-boot-upgrade:

It may be done silently.

4

Even if it is marked "read-only" you might be able to "unlock" it with the little package called "mtd-rw'.

5

Used OpenWRT 14.07 from there to flash u-boot_mod on WDR3600 and 740N v4, after that sysupgraded to LEDE.

6

Hi, any idea if wNdr4300 (netgear not TP-L) is supported?. I'like to overclock it.

7

No netgear in currently supportded devices list.

8

Finally, no time to play around with encrypted root and boot. Sorry and thank you for your support.

9

I flashed an image for MR-3040 and bricked the device. It doesn't boot any more.
It flashes al LEDs.

10

WARNING: Flashing uboot can irreversably brick your router unless you have JTAG access. If you can't risk losing the device don't do it unless you have JTAG (at least...or replacement flash chips and you can remove the old one (desolder) and put in the (solder) the new one.

11

I managed to reflash it using UART.

1 Like
12

Works for me (tm).

13

I made a stupid mistake. Works for me too.

The u-boot is super. Thanks a lot.

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14

Is there a menuconfig option to unlock the uboot partition, or do we just need to go remove the read-only attribute in DTS?

15

The later (or using kmod-mtd-rw).

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16

im searching for every mention of this mod because i had trouble finding info\documentation for begginners on installing and using the uboot mod. so i pieced it together and made this video to help. https://www.youtube.com/watch?v=i4A321qDbTU&t=174s

1 Like