UBIFS Dumper

This tool can be used to view or extract the contents of UBIFS images.

About UBIFS

UBIFS is a filesystem specifically designed for used on NAND flash chips. NAND flash is organized in eraseblocks. Eraseblocks can be erased, appended to, and read. Erasing is a relatively expensive operation, and can be done only a limited number of times.

An UBIFS image contains four abstraction layers:

• eraseblocks
• volumes
• b-tree nodes
• inodes

Each eraseblock contains info on how often it has been erased, and which volume it belongs to. A volume contains a b-tree database with keys for:

• inodes, indexed by inode number
• direntries, indexed by inode number + name hash
• datablocks, indexed by inode number + block number

The inodes are basically a standard unix filesystem, with direntries, regular files, symlinks, devices, etc.

mounting images on linux

modprobe nandsim first_id_byte=0x2c second_id_byte=0xac third_id_byte=0x90 fourth_id_byte=0x26
nandwrite /dev/mtd0   firmware-image.ubi 
modprobe ubi mtd=/dev/mtd0,4096
mount -t ubifs  -o ro /dev/ubi0_0 mnt

This will mount a ubi image for a device with eraseblock size 0x40000. If your image has a blocksize of 0x20000, use fourth_id_byte=0x15, and specify a pagesize of 2048 with the second modprobe line.

Usage

View the contents of the /etc/passwd file in the filesystem image image.ubi:

python ubidump.py  -c /etc/passwd  image.ubi

List the files in all the volumes in image.ubi:

python ubidump.py  -l  image.ubi

View the contents of b-tree database from the volumes in image.ubi:

python ubidump.py  -d  image.ubi

Extract an unsupported volume type, so you can analyze it with other tools:

python ubidump.py  -v 0 --saveraw unknownvol.bin  image.ubi

Note that often ubi images contain squashfs volumes, which can be extracted using tools like unsquashfs or rdsquashfs

Install

Install the required python modules using:

pip install -r requirements.txt

or as a pip package:

pip install ubidump

You may need to manually install your operarating system libraries for lzo first:

on linux:

apt install liblzo2-dev

on MacOS:

brew install lzo

maybe you need to build the python library like this:

LDFLAGS=-L/usr/local/lib CFLAGS=-I/usr/local/include/lzo pip3 install python-lzo

When you need zstd compression, you will need to install the zstandard module.

Dependencies

• python2 or python3
• python-lzo ( >= 1.09, which introduces the 'header=False' argument )
• crcmod
• optional: zstandard

TODO

• add option to select a volume
• add option to select a older master node
• parse the journal
• analyze b-tree structure for unused nodes
• analyze fs structure for unused inodes, dirents
• verify that data block size equals the size mentioned in the inode.
• add support for ubifs ( without the ubi layer )
• add option to extract a raw volume.

References

• the ubifs/mtd tools http://linux-mtd.infradead.org/
• git repos can be found here

Similar tools

• another python tool on github
  • does not support listing files.
• a closed source windows tool here
• ubi-utils/ubidump.c on the mtd mailinglist

Author

Willem Hengeveld itsme@xs4all.nl