Hector Martin

So realistically, the only way to recover the devices is just a custom firmware and reimplementing their servers locally?

Which, I'm not speaking to the ethics of it here, I'm just saying, would almost certainly be a violation of the anti-circumvention provisions of the DMCA.

That's not how the DMCA works. If you're replacing Sonos firmware with your own the DMCA has nothing to say, because you aren't accessing any copyrighted content.

That depends on whether the firmware is allowing you to access copyrighted code on the device when you would otherwise not be able to do so. Since that includes the rest of the code in the firmware, unless you literally write a new firmware from scratch AND the device...

... contains no other copyrighted code which you now have access to when you didn’t before, the question is not so simple as it might first appear.

If you replace the whole firmware, then there is no copyrighted code (other than the bootrom, but Sonos didn't write that) left. At most there may be crypto keys in the hardware used for streaming stuff, but you can ignore them.

I have no idea what the architecture of these devices is like so I am willing to take your word for it. If what you are saying is true, then yes, it seems likely an original firmware build would avoid the AC prohibitions, and my initial opinion was in error.

I have no idea either, but practically every device of this sort is just a chain of one or more loaders and the final image. Once you take control at any step of the process, you can replace all running code with your own and not use anything else that may incidentally be there.