decompressing u-boot/PPCBoot image

[tmetro-blu-5a1Jt6qxUNc at public.gmane.org (Tom Metro)]

A while ago I purchased an IP camera, in large part because it said it 
ran Linux. It's manufactured by a Taiwanese company (but I'm not sure 
who), and sold by a US distributor[1], which has since discontinued 
carrying it, but it still appeared to be carried elsewhere[2].

Shortly after receiving it I sent a request to the reseller for the 
source code, which was ignored (though they responded to other tech 
support issues). If I had not been in a rush to deploy the camera, I 
would have sent it back at that point. Now that they've discontinued 
carrying the product, I might be able to get the name of the 
manufacturer out of them, and I'll try contacting the manufacturer 
directly, but I'm not too hopeful.

So I was looking at the firmware update the reseller supplied to me to 
see what might be learned from it, and whether it presented any 
opportunities for hacking into the device. The file they sent has a .gz 
extension, implying gzip of course, but gzip doesn't recognize it. The 
'file' command reports that it is a "u-boot/PPCBoot image." Googling 
that or portions of that hasn't told me much, but this posting:

http://lkml.indiana.edu/hypermail/linux/kernel/0404.2/1394.html

suggests that this type of file can contain a gzip image at an offset (I 
presume following a boot loader of sorts), so I scanned through the file 
looking for the first 4-bytes that seem to signify a gzip file, and 
found nothing. Same for a bzip2 header. Yet the data stream appears 
random, as compressed data would.

Does anyone know how to decompress a u-boot/PPCBoot image file?
How about a source of information on the file format? Does PPC refer to 
Power PC architecture? u-boot seems to show up frequently in the context 
of USB booting.

1. http://www.gadspot.com/
2. http://ipcamerastore.ecrater.com/product.php?pid=2161747

  -Tom

-- 
Tom Metro
Venture Logic, Newton, MA, USA
"Enterprise solutions through open source."
Professional Profile: http://tmetro.venturelogic.com/