Unpacking U-Boot image file

[trewio]

How to extract files from U-Boot image file, LZMA-compressed?

Is there a Python script that can do this properly?

[Rustom Mody]

On Wednesday, April 9, 2014 9:36:40 PM UTC+5:30, trewio wrote:
> How to extract files from U-Boot image file, LZMA-compressed?
>
> Is there a Python script that can do this properly?

For lzma theres this (recent) python library
https://docs.python.org/dev/library/lzma.html

Though you might just be better off with the command-line xz unxz etc

After that.. whats the U-boot format?

[Adnan Sadzak]

I belive you are trying to decompress some router images or router backup/config files?

Check if maybe LZS.

Rustom gave You starting point.

--
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[trewio]

I need decompress image(modem), and I deciced use some Python script or utility which capable run on Python for Windows OS.

[trewio]

U-Boot format: hmm, I'm not sure, can someone specify Python script that will help me deterermine U-boot format used? [for Python for Windows OS]

Note: I need Python script for Python under Windows OS.

> ----- Original Message -----
> From: Rustom Mody
> Sent: 04/09/14 08:18 PM
> To: pytho...@python.org
> Subject: Re: Unpacking U-Boot image file
>

[lagu...@mail.com]

I know about Binwalk, it can run on Linux OS only. I am looking for Python script that can run on Windows too.

Thank you.
 

 

 

----- Original Message -----

From: Adnan Sadzak

Sent: 04/09/14 11:37 PM

To: trewio

Subject: Re: Unpacking U-Boot image file

 

Oh then see Craig's page [0]. You can find in deepth explanation about some tools (Linux) that is used to desompress and mount filesystems/images. From my experience you should find first read modem tehnical documentation. Find out what kind of firmware is using. You won't find just script to decompress those images.

 

[0] http://www.devttys0.com/2011/05/reverse-engineering-firmware-linksys-wag120n/

 

Cheers

 

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https://mail.python.org/mailman/listinfo/python-list

 

 

 

[Dave Angel]

"trewio" <lagu...@mail.com> Wrote in message:

> How to extract files from U-Boot image file, LZMA-compressed?
>
> Is there a Python script that can do this properly?
>

Use the lzma module in Python 3.3 for starters

--
DaveA

[Dave Angel]

"trewio" <lagu...@mail.com> Wrote in message:

> U-Boot format: hmm, I'm not sure, can someone specify Python script that will help me deterermine U-boot format used? [for Python for Windows OS]
>
> Note: I need Python script for Python under Windows OS.
>
>
>> ----- Original Message -----
>> From: Rustom Mody
>> Sent: 04/09/14 08:18 PM
>> To: pytho...@python.org
>> Subject: Re: Unpacking U-Boot image file
>>
>> On Wednesday, April 9, 2014 9:36:40 PM UTC+5:30, trewio wrote:

>> > How to extract files from U-Boot image file, LZMA-compressed?
>> >
>> > Is there a Python script that can do this properly?
>>

>> For lzma theres this (recent) python library
>> https://docs.python.org/dev/library/lzma.html
>>
>> Though you might just be better off with the command-line xz unxz etc
>>
>> After that.. whats the U-boot format?
>> --
>> https://mail.python.org/mailman/listinfo/python-list
>
>

Good job starting 3 separate threads for same question. Sorry I
answered the first one.
--
DaveA

[Rhodri James]

On Wed, 09 Apr 2014 18:18:56 +0100, Rustom Mody <rusto...@gmail.com>
wrote:

The Fine Manual (http://www.denx.de/wiki/view/DULG/UBootImages) isn't very
forthcoming, sadly;

"U-Boot operates on "image" files which can be basically anything,
preceeded by a special header; see the definitions in include/image.h for
details; basically, the header defines the following image properties

* Target Operating System
* Target CPU Architecture
* Compression Type
* Load Address
* Entry Point
* Image Name
* Image Timestamp"

I suspect taking this apart may be a little involved.

--
Rhodri James *-* Wildebeest Herder to the Masses

[Rustom Mody]

On Friday, April 11, 2014 3:31:50 AM UTC+5:30, Rhodri James wrote:
> On Wed, 09 Apr 2014 18:18:56 +0100, Rustom Mody

> > After that.. whats the U-boot format?
>
> The Fine Manual (http://www.denx.de/wiki/view/DULG/UBootImages) isn't very
> forthcoming, sadly;
>
> "U-Boot operates on "image" files which can be basically anything,
> preceeded by a special header; see the definitions in include/image.h for
> details; basically, the header defines the following image properties
>
> * Target Operating System
> * Target CPU Architecture
> * Compression Type
> * Load Address
> * Entry Point
> * Image Name
> * Image Timestamp"
>
>
> I suspect taking this apart may be a little involved.

If its a binary format, you (OP) may want to look at
https://pypi.python.org/pypi/construct/2.5.1

Of course you will have to read/get the C struct and write the corresponding
"Construct"

You may want to ask on a U-boot forum for more details.

[Grant Edwards]

Not really. For the format you're talking about (single-file uImage),
you can extract the data like so:

data = open("foobar.uImage","rb").read()[64:]

Then just uncompress 'data' as desired.

If you want to look at individual fields in the heaer, here's the
structure:

#define IH_MAGIC 0x27051956 /* Image Magic Number */
#define IH_NMLEN 32 /* Image Name Length */

typedef struct image_header
{
uint32_t ih_magic; /* Image Header Magic Number */
uint32_t ih_hcrc; /* Image Header CRC Checksum */
uint32_t ih_time; /* Image Creation Timestamp */
uint32_t ih_size; /* Image Data Size */
uint32_t ih_load; /* Data Load Address */
uint32_t ih_ep; /* Entry Point Address */
uint32_t ih_dcrc; /* Image Data CRC Checksum */
uint8_t ih_os; /* Operating System */
uint8_t ih_arch; /* CPU architecture */
uint8_t ih_type; /* Image Type */
uint8_t ih_comp; /* Compression Type */
uint8_t ih_name[IH_NMLEN]; /* Image Name */
} image_header_t;

Header fields are all in network byte order (bit-endian).

However, there's also a "multi-file" uImage format that I suspect is
what the OP is referring to (since he says he needs to extract "files"
from a uImage file).

http://www.isysop.com/unpacking-and-repacking-u-boot-uimage-files/

In that case, the "Image Type" field will be set to 4, and the 'data'
field starts with a list of 32-bit image size values (network byte
order, terminated by 0x00000000). That list is then followed by the
image data.

Here's a Python 2.7 program that reads the uImage header, prints some
stuff and then reads the data for the image(s). What to _do_ with the
data for the image(s) is left as an exercise for the gentle reader.

-------------------------------------8<-------------------------------------
#!/usr/bin/python

import sys,struct

f = open(sys.argv[1],"rb")

(ih_magic, ih_hcrc, ih_time, ih_size, ih_load, ih_ep, ih_dcrc,
ih_os, ih_arch, ih_type, ih_comp, ih_name) \
= struct.unpack("!IIIIIIIBBBB32s",f.read(64))

print "magic=%08x type=%d size=%d name='%s'" % (ih_magic, ih_type, ih_size, ih_name)

if ih_type == 4:
# multi-file: read image lengths from data
imagesizes = []
while 1:
size, = struct.unpack("!I",f.read(4))
if size == 0:
break
imagesizes.append(size)
else:
# single-file
imagesizes = [ih_size]

print imagesizes

images = [f.read(size) for size in imagesizes]

print [len(image) for image in images]

extradata = f.read()

if extradata:
print "%d bytes of extra data" % len(extradata)

-------------------------------------8<-------------------------------------










--
Grant Edwards grant.b.edwards Yow! The Korean War must
at have been fun.
gmail.com