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Reverse engineering my router's firmware with binwalk

embeddedbits.org

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Re: Reverse engineering my router's firmware with binwalk

#61

Post by mml »

ggcdn wrote: post #51

A slightly related question for HNers: Is there any easy tool for a non-cs guy to reverse engineer a binary file containing numbers and text in some specific format? I have to work with some old structural analysis software. The material and element definitions come in an obscure file format ".PF3CMP". I know it contains text like the material names, and numbers/letters for the material properties. Ultimately its my…

related possibly? what domain is this file from?

https://techdocs.broadcom.com/content/broadcom/techdocs/us/e...

Re: Reverse engineering my router's firmware with binwalk

#62

Post by ggcdn »

mml wrote: post #61
ggcdn wrote: post #51

A slightly related question for HNers: Is there any easy tool for a non-cs guy to reverse engineer a binary file containing numbers and text in some specific format? I have to work with some old structural analysis software. The material and element definitions come in an obscure file format ".PF3CMP". I know it contains text like the material names, and numbers/letters for the material properties. Ultimately its my…

related possibly? what domain is this file from? https://techdocs.broadcom.com/content/broadcom/techdocs/us/e...

thanks but sadly not, its from a structural analysis program called PERFORM-3D.

I've contacted the developer but they will not release the format of the files to me.

Re: Reverse engineering my router's firmware with binwalk

#63

Post by ggcdn »

Youden wrote: post #53
ggcdn wrote: post #51

A slightly related question for HNers: Is there any easy tool for a non-cs guy to reverse engineer a binary file containing numbers and text in some specific format? I have to work with some old structural analysis software. The material and element definitions come in an obscure file format ".PF3CMP". I know it contains text like the material names, and numbers/letters for the material properties. Ultimately its my…

I don't know of any straightforward tools, most people I've seen reverse engineer a format do it with a hex editor and writing custom scripts. It's not directly relevant but the best I've seen is this presentation about reverse engineering the protocol used to communicate within a car: https://www.youtube.com/watch?v=KkgxFplsTnM It uses some techniques that might be relevant, like monitoring different parts of a file…

Ok thanks, I'll take a look. It's possible for me to generate these files for each of the various material settings so I can manually 'diff' them, simillar to what you're describing

Re: Reverse engineering my router's firmware with binwalk

#64

Post by PeterisP »

ggcdn wrote: post #51

A slightly related question for HNers: Is there any easy tool for a non-cs guy to reverse engineer a binary file containing numbers and text in some specific format? I have to work with some old structural analysis software. The material and element definitions come in an obscure file format ".PF3CMP". I know it contains text like the material names, and numbers/letters for the material properties. Ultimately its my…

Depending on how weird the format is, it might be more efficient to reverse-engineer the file-reading routines of that program which can work with these files.

Re: Reverse engineering my router's firmware with binwalk

#65

Post by bradknowles »

fencepost wrote: post #43
josteink wrote: post #20

Did I read the blog wrong, or was the stock firmware too based on a OpenWRT kernel? That would be pretty hilarious if it was true.

I'm pretty sure a lot of stock firmware is based on OpenWRT or used to be, though I'm pretty sure most of them lag well behind the current version. I haven't paid much attention for a while, but I think a lot were based on Kamikaze which is more than 10 years old now. For the vendors with access to closed-source drivers and chipset info they can likely support devices not supported on the open source packages. Edit:…

Ubiquiti is based on Vyatta.

Re: Reverse engineering my router's firmware with binwalk

#66

Post by hiisukun »

hyper_reality wrote: post #60

It's a good article but there are much easier ways to use binwalk than presented here. In the first example he uses the "--signature" and "--term" flags, these are unnecessary. Running binwalk with no flags will produce the same output. To extract part of the file, he also uses dd with the "skip" and "count" options painfully calculated. You can just use: binwalk --dd='.*' img.bin and it will extract everything that…

Just a quick note to be careful extracting what binwalk considers to be 'everything' (such as the pattern above, or a -e for known file types) on larger files. Sometimes there will be a higher amount of matches than you might expect (such as in a .pcap file). You could magically extract gigabytes of data from a 100MB file, which may be unhelpful and takes a long time.

Re: Reverse engineering my router's firmware with binwalk

#69

Post by voltagex_ »

ggcdn wrote: post #51

A slightly related question for HNers: Is there any easy tool for a non-cs guy to reverse engineer a binary file containing numbers and text in some specific format? I have to work with some old structural analysis software. The material and element definitions come in an obscure file format ".PF3CMP". I know it contains text like the material names, and numbers/letters for the material properties. Ultimately its my…

Something like this may help: https://ide.kaitai.io/, but I've found it a bit overwhelming.

It might be easiest to just start writing a utility that parses it, first making guesses and then refining as you generate and test more files like you mentioned in another reply. You already know what the magic bytes are at the start of the file - PF3CMP.

Re: Reverse engineering my router's firmware with binwalk

#70

Post by wtallis »

ChuckNorris89 wrote: post #5
bluesign wrote: post #4

Earlier quoted context omitted.

It is mostly related to drivers to soc, not about paying devs

So how did OpenWRT manage to build firmware with up to date components for it? The Qualcomm chips inside of it seem fairly modern for such an old kernel.

Qualcomm networking chips mostly have open-source drivers, which are mostly upstreamed to the mainline Linux kernel releases. So there's nothing really holding back kernel versions on that hardware, other than the regular maintenance burden of keeping a Linux distro up to date—which few OEMs are interested in doing. Broadcom by contrast is less friendly to open-source, and their closed-source drivers can preclude kernel updates.
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