Miscellaneous Projects » SuperSignal AP 2820V

h1. Flashing

There are several way to flash partitions (e.g. updating) manually:

* using @/usr/sbin/ubiupdatevol@:

<pre>

ubiupdatevol version 1.2 - a tool to write data to UBI volumes.

Usage: ubiupdatevol <UBI volume node file name> [-t] [-s <size>] [-h] [-V] [--truncate]

			[--size=<size>] [--help] [--version] <image file>

Example 1: ubiupdatevol /dev/ubi0_1 fs.img - write file "fs.img" to UBI volume /dev/ubi0_1

Example 2: ubiupdatevol /dev/ubi0_1 -t - wipe out UBI volume /dev/ubi0_1

-t, --truncate             truncate volume (wipe it out)

-s, --size=<bytes>         bytes in input, if not reading from file

-h, --help                 print help message

-V, --version              print program version

</pre>

* using @/APP/dev_only/swupd.sh@

<pre>

swupd.sh - update flash partitions on the target

Easy mode:

   using NFS: swupd.sh -i<IP> -p<PATH>

   where:

   <IP>   = IP address of your VM (defaults to 192.168.16.18)

   <PATH> = path of NFS directory (defaults to /home/femto/ftpdata)

   using wget: swupd.sh -w<URL>

   where:

   <URL>  = URL to fetch images from (e.g. ftp://user:pass@host/path)

Expert mode: (stay away from them!)

   -k update kernel

   -r update root fs

   -a update application partition

   -u update unitdata partition

   -c update caldata partition

   -x toggle banks

   -z don't reboot after successful update

   -o<str> Pass option string <str> to wget

</pre>

@/etc/init.d/flash_update@ takes care of flashing all partitions at once (also done during boot in @/etc/init.d/rcS@).

Lastly the operator can also flash images remotely through @/APP/bin/oam_start@.

h1. Secure boot

h2. System

The partition signatures (kernel, rootfs, data) are stored in @/dev/mtdblock2/bootdata.ini@ (the only file in the @bootdata@ partition).

While @bootdata@ is not signed itself, it only contains the signatures.

You can also see the content using @/APP/dev_only/cat_bootdata.sh@

The corresponding public key seems to be burned in the OTP section of the CPU, providing secure boot (this has not been verified).

@bootdata.ini@ also defines which system will be booted (A or B).

The file is updated using @/APP/dev_only/write_bootdata.sh@

For the [[Bootlog]] the femtocell seems to use "secure boot":

# the Percello bootrom verifies the Percello bootloader:

<pre>

Percello bootrom version 1.2.8

...

Board: Secure mode

...

Secured device - OTP2: verification ...PASSED

Secured device - OTP3: verification ...PASSED

Running Percello bootloader

PASSED

</pre>

# the Percello bootloader loader the Sagemcom FM-loader

<pre>

Nand execute: load_addr: 3fe0000

Percello bootloader version 0.6 (from NAND)

</pre>

# the Sagemcom FM-loader verifies the signatures of the kernel, rootfs, and app partitions

<pre>

Sagemcom FM-loader v2.0.4-11

Boot 1 (cold) into main system, secured

...

Unit key found and verified

TrustStor signature check passed

Group A signature check passed

Kernel A signature check passed

Root file system A signature check passed

Application file system A signature check passed

</pre>

You can check if secure boot has been activated using @cat /proc/prc6000/otp_data/boot/secured@ but it is unclear how the signatures are verified.

h2. Operator

The @unidata@ (mtd3) signature is checked in @/etc/init.d/flash_update@ (called by @/etc/init.d/rcS@) using @/boot/bc_cli -u${PARTNUM_UNITDATA} -q@ (with PARTNUM_UNITDATA=3):

* hash is sha1sum of 0x2000 (8192) first bytes

* signature is at 0x2000 (after the cramfs indicated size)

* public key is first 256 bytes of @/caldata/unitkey.bin@

It the signature check fails, @unidata_backup@ is used.

If this signature check fails too, it enters recovery mode

@caldata@ in mounted without check (in @/etc/init.d/flash_update@)