“Signal is being blocked in Venezuela and Russia. The app is a popular choice for encrypted messaging and people trying to avoid government censorship, and the blocks appear to be part of a crackdown on internal dissent in both countries…”
Maybe I’ve misunderstood how it works. I thought that when connecting to a matrix instance you would point to the domain name and the text file would be on a standard location (as with /robots.txt or all the files in /.well-known/) so it would be easily discoverable. In fact I just checked and matrix does use /.well-known/ so one should be able to identify matrix servers by querying these URLs. Unless their is a way to use a non-standard location, but that would require further configuration on the client I guess.
And just to answer your question, the only way to find some hidden file would be to brute force. This could obviously be extremely time consuming if the URL is long and random enough, especially if you add rate limiting (this last thing could be circumvented by using multiple IPs to scan, which would be easy for a state actor).
Edit: I’ve just realized I wasn’t answering to the same person, the first part of the message was more for @TarantulaFudge@startrek.website
Yeah the main thing is that the ports and addresses can change and it’s nbd. From a firewall perspective, it’s impossible to block them all. Especially when the clients are doing mundane https requests. Even if the server goes down or partial connectivity, the channel can still be used.
But this seems easy to automatically block, no? If a client is querying an unknown domain check for some Matrix related data in /.well-known/ and add it to the block list if there is. And since the servers are publicly advertising the port used you just need to periodically check the list of known matrix domains you are creating in the first step.
Russia is already doing DPI and blocking ESNI so that seems easy. A more widespread usage of ECH would help everyone, as is Signal advocating, but that’s not the case yet.
