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

Dependencies

• python2
• python-lzo
• crcmod

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 )

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