Hacker News Reader

Comment by readerrrr | Hacker News Reader

Looks like this is equivalent to a dedicated usb charger.

There should be an option to enable data transfer, currently you have to physically remove it.

I would love to have something like this, if it enabled my devices to be read only; some usb flash drives have a physical button to enable that.

View on HN

Enabling for read-only in the general case simply wouldn't be possible. The device would have to know every USB protocol that could possibly be spoken and which commands are for reading and which for writing (and what to do with commands that do both).

You could maybe make now that only worked for USB storage devices and only allowed reading, but it would likely be complex and have other downsides (lack of performance and compatability issues probably) that would make it not worth it.

This would basically be a packet-inspecting firewall for USB instead of IP. I agree that this would pose a number of technical challanges as a lot of the tools and optimizations we have in IP stacks don't exist for USB, but I don't see how that would be principally impossible.

In fact, as there is a lot more standardization in USB profiles than in IP protocols, it might even be easier. I.e. if you just inspected messages of the mass storage profile and blocked everything else, you might already get pretty far. I agree that the performance problem would stay though.

I don't think you could make a IP firewall that enforced read-only either, at least not in a general case.

You'd have to have knowledge of what protocol was being spoken. Otherwise, you don't know of if a packet going back the "wrong" direction is a control mechanism (request for data, flow control, etc) or data itself. In terms of ethernet, you could possibly do UDP, but you lose any sort of error handling or flow control.

Reply on news.ycombinator.com