5 ms·

It’s too late. Whole countries block all eSNI requests, so it’s always going to fail open.

by saddlerustle 4y ago

coldsauce 4y ago
Yeah, I believe China doesn't even allow TLSv1.3
- tialaramex 4y ago
  Not allowing TLS 1.3 means nothing (no modern web sites) works. Modern browsers and servers both speak TLS 1.3 and if they can't they give up. Some things don't work in China, but China wouldn't have a thriving economy if nothing was working. So no, they did not block TLS 1.3 although it's interesting how this rumour seems to have self-popularised. China blocks certain popular sites, but it does not block whole protocols or protocol versions. This is actually a small triumph for the people responsible for RFC 8446. With previous iterations of TLS it was always discovered shortly after release that idiots broke stuff and so a "fallback" was necessary to allow you to speak the previous version. Such fallback is dangerous because an adversary can thus forcibly downgrade you to an older protocol, and thus attack old protocols even if the new protocol is safe. How is it done? That is, how does TLS 1.3 avoid downgrade attacks? When a TLS 1.3 server finds itself talking to somebody over TLS 1.2 (for example maybe a rather archaic web browser is connecting) it scribbles over some of the bytes labelled "random" in its Hello message. It scribbles 44 4F 57 4E 47 52 44 01. Which in ASCII spells "DOWNGRD". Those bytes don't mean anything special in TLS 1.2, they're just a strange coincidence. But if you're a TLS 1.3 client, seeing those bytes means a Downgrade attack was attempted. So you immediately give up, you are being attacked. So you might think well, a bad guy could just change those bytes blind right? Nope. The "random" field is used by both parties to choose parameters they're going to verify in a moment to check everything is safe. If you can change the bytes the values will be different and the connection fails anyway.
  - _8j50 4y ago
    They can ban tls 1.3 internally and do tls1.3 post intercept to the server.
  - psyfi 4y ago
    > Some things don't work in China, but China wouldn't have a thriving economy if nothing was working. Any company who does not want to lose a market of ~18% of global population will make sure it complies (example: Apple). We need to think about real life here and not just technical implementation
_8j50 4y ago
Well then hopefully tech people will soon wrap their head around the fact that political problems are best solved politically. You can't write tech that overrides the authority of governments but you can override or change governments.
- denton-scratch 4y ago
  > You can't write tech that overrides the authority of governments Really? Tor springs to mind.
  - _8j50 4y ago
    Same. What's your point? VPNs also bypass government blocks. It's a cat and mouse game, they block vpns and guards as they see fit when they have a good reason to. Look at tor, if a country tls decrypts everything and blocks connections that can't be decrypted can it still bypass their blocks? Just because not every government is doing it does not mean Tor can't be blocked. Hell, countries allow-list connections to allowed sites if they want. Breaking their laws may make you feel edgy but that sort of "revolution exporting" many in other countries consider it a form of neo-colonialism where you undermine their sovreignity and self-determination.
    - denton-scratch 4y ago
      You're right; ultimately, if you have total power, you can just block the internet.
    - mindslight 4y ago
      > many in other countries consider it a form of neo-colonialism where you undermine their sovreignity and self-determination. Only if by "their" you mean the ruling class, and by "self-determination" you mean their ability to control others. You can't really say their opinions represent the will of the people, especially when it's the people themselves ultimately choosing to engage in "illegal" activities. And sure, "the will of the people" bakes in two very western individual/collectivist values. But as I get older I'm learning to not play the relativism card as much. We should certainly be critical of our culture - but to the point of making it better, not handicapping its spread. Plus there's still a very easy answer for the poor oppressed tyrant who doesn't like freedom of communication - shut down all Internet connections.

It’s too late. Whole countries block all eSNI requests, so it’s always going to fail open.

coldsauce 4y ago

Yeah, I believe China doesn't even allow TLSv1.3

tialaramex 4y ago
Not allowing TLS 1.3 means nothing (no modern web sites) works. Modern browsers and servers both speak TLS 1.3 and if they can't they give up. Some things don't work in China, but China wouldn't have a thriving economy if nothing was working. So no, they did not block TLS 1.3 although it's interesting how this rumour seems to have self-popularised. China blocks certain popular sites, but it does not block whole protocols or protocol versions. This is actually a small triumph for the people responsible for RFC 8446. With previous iterations of TLS it was always discovered shortly after release that idiots broke stuff and so a "fallback" was necessary to allow you to speak the previous version. Such fallback is dangerous because an adversary can thus forcibly downgrade you to an older protocol, and thus attack old protocols even if the new protocol is safe. How is it done? That is, how does TLS 1.3 avoid downgrade attacks? When a TLS 1.3 server finds itself talking to somebody over TLS 1.2 (for example maybe a rather archaic web browser is connecting) it scribbles over some of the bytes labelled "random" in its Hello message. It scribbles 44 4F 57 4E 47 52 44 01. Which in ASCII spells "DOWNGRD". Those bytes don't mean anything special in TLS 1.2, they're just a strange coincidence. But if you're a TLS 1.3 client, seeing those bytes means a Downgrade attack was attempted. So you immediately give up, you are being attacked. So you might think well, a bad guy could just change those bytes blind right? Nope. The "random" field is used by both parties to choose parameters they're going to verify in a moment to check everything is safe. If you can change the bytes the values will be different and the connection fails anyway.
- _8j50 4y ago
  They can ban tls 1.3 internally and do tls1.3 post intercept to the server.
- psyfi 4y ago
  > Some things don't work in China, but China wouldn't have a thriving economy if nothing was working. Any company who does not want to lose a market of ~18% of global population will make sure it complies (example: Apple). We need to think about real life here and not just technical implementation

_8j50 4y ago

Well then hopefully tech people will soon wrap their head around the fact that political problems are best solved politically. You can't write tech that overrides the authority of governments but you can override or change governments.

denton-scratch 4y ago
> You can't write tech that overrides the authority of governments Really? Tor springs to mind.
- _8j50 4y ago
  Same. What's your point? VPNs also bypass government blocks. It's a cat and mouse game, they block vpns and guards as they see fit when they have a good reason to. Look at tor, if a country tls decrypts everything and blocks connections that can't be decrypted can it still bypass their blocks? Just because not every government is doing it does not mean Tor can't be blocked. Hell, countries allow-list connections to allowed sites if they want. Breaking their laws may make you feel edgy but that sort of "revolution exporting" many in other countries consider it a form of neo-colonialism where you undermine their sovreignity and self-determination.
  - denton-scratch 4y ago
    You're right; ultimately, if you have total power, you can just block the internet.
  - mindslight 4y ago
    > many in other countries consider it a form of neo-colonialism where you undermine their sovreignity and self-determination. Only if by "their" you mean the ruling class, and by "self-determination" you mean their ability to control others. You can't really say their opinions represent the will of the people, especially when it's the people themselves ultimately choosing to engage in "illegal" activities. And sure, "the will of the people" bakes in two very western individual/collectivist values. But as I get older I'm learning to not play the relativism card as much. We should certainly be critical of our culture - but to the point of making it better, not handicapping its spread. Plus there's still a very easy answer for the poor oppressed tyrant who doesn't like freedom of communication - shut down all Internet connections.