How to allow Tor browser to access local port?

Question

I'm interested in using the Tor browser with a Trezor. Trezor uses something called the "Trezor Bridge" to communicate between the browser and the device. (It is also called trezord, and is found here: https://github.com/trezor/trezord). The Trezor Bridge, once installed, is accessed on one's computer via the following address: https://localback.net:21324/

This address is readily accessible from an ordinary web browser, but from within the Tor browser, this address appears to be completely blocked.

I've tried going into the Network settings and adding 127.0.0.1 to the "No proxy for" list of addresses, but this had no effect. I then tried adding localback.net to the "No proxy for" list of addresses, and the only thing that changed is that the error message when trying to reach https://localback.net:21324 changed from "Unable to connect" to "Unable to find the proxy server".

What is the correct way to allow the Tor browser to communicate with the device via this address/port?

Answer 1

There is no "correct" way.

What's happening is that Tor Browser is configured to use Tor for all outbound connections, when you try to visit 127.0.0.1 on your browser, you try to negotiate with Tor to ask it to make a connection over the Tor network to 127.0.0.1, this obviously makes no sense and is therefor rejected.

One option might be to set an exception in the proxy settings. Edit -> Preferences -> Advanced -> Network -> Connection -> Settings, and add 127.0.0.1 to the 'No Proxy For' list. However, this opens you up to attacks where a website might try to access local services to get them to make connections outside of the Tor network or to leak identifying information, which is why such exceptions are not set and it is recommended not to do this.