5 ms·

The snooping of unencrypted SNI in the TLS handshake is a known weakness that is still mostly unresolved despite four years of standardization effort. The encry

The snooping of unencrypted SNI in the TLS handshake is a known weakness that is still mostly unresolved despite four years of standardization effort. The encrypted SNI work has been revised and updated to encrypted ClientHello and is still technically an IETF draft and not yet formalized in an RFC: https://datatracker.ietf.org/doc/draft-ietf-tls-esni/ https://datatracker.ietf.org/doc/draft-ietf-tls-esni/ That said, CloudFlare, Firefox, and Chromium teams have all been working toward the evolving spec so one can hope that soon with eCH and DNS-over-HTTPS we will be able to have clients securely connect to servers without broadcasting the hostname to which they are connecting.

dweekly 4y ago
Follow along on Chromium support here: https://bugs.chromium.org/p/chromium/issues/detail?id=1091403 https://bugs.chromium.org/p/chromium/issues/detail?id=109140...
aorth 4y ago
Wait I'm confused. I remember reading a bunch of reports about how China started blocking TLS 1.3 because of encrypted SNI (eSNI) years ago?
- dweekly 4y ago
  I don't know anything about that (and I'm pretty sure TLS 1.3 doesn't mandate ECH since ECH isn't even finished standardizing!) but you can check to see if your browser supports ECH by visiting https://tls-ech.dev/ https://tls-ech.dev/
- tialaramex 4y ago
  Some people interested in the Great Firewall wrote up weirdness they saw with one particular prototype of eSNI years back. A game of Telephone later this became nonsense like "China blocks TLS 1.3" but actually if you do that what you get isn't web sites stripped of protection but connection errors. Which is indeed what happens for some sites from the other side of the Great Firewall, but we just say China blocks those sites, because that is what they do. Protocol versions are not crucial to them. The current iteration of ECH is designed to be GREASEd which means browsers might just always do ECH with dummy values regardless, so either you block or you don't, you won't be able to selectively block ECH. This doesn't magically prevent the Great Firewall from working but does mean specifically host matching is degraded as intended.
  - 6502nerdface 4y ago
    > A game of Telephone Funny enough the children's "telephone game" is, in many Commonwealth countries, apparently called "Chinese whispers," at least according to my Londoner colleagues.
    - vmilner 4y ago
      Yes, I’m British and when American friends first used the word “Telephone” in conversation I was very confused.
vbezhenar 4y ago
And it means that state firewalls will just block all CDNs.
- novok 4y ago
  The idea is you force them to choose the entire effective internet or nothing, which is not an economic self own even most dictatorships are willing to make. These firewalls are an exercise in having your cake and eating it too.
  - vbezhenar 4y ago
    CDNs are not entire effective internet. Also I'm not well-educated in that area, but I would expect that CDNs would allocate dedicated IP ranged for big customers like Microsoft or Apple. So state can ban more selectively, white-listing those ranges.
  - saurik 4y ago
    But it doesn't end there... they block the CDN that implements this feature, and then the CDN's customers--who probably didn't care much about the benefits this gives to some of their users but are now losing access to some large customer base--start complaining and migrating off the CDN, which results in the CDN pulling back on the feature. And we know this is what will happen as this is effectively what happened with domain fronting--where you simply use the wrong SNI instead of hiding it entirely--with all the large CDNs actively "fixing" this feature to prevent their customer's websites from being blocked by firewalls because of users who were using this to get around hostname restrictions.
    - novok 4y ago
      Yup it's a cat and mouse game, and how much money these dictators represent. Thankfully? in the case of Iran, many customers do not want to interact with Iran because of US export regulations, so if it breaks that, all the better ironically enough.
      - 4y ago

dweekly 4y ago

Follow along on Chromium support here: https://bugs.chromium.org/p/chromium/issues/detail?id=1091403 https://bugs.chromium.org/p/chromium/issues/detail?id=109140...

aorth 4y ago

Wait I'm confused. I remember reading a bunch of reports about how China started blocking TLS 1.3 because of encrypted SNI (eSNI) years ago?

dweekly 4y ago
I don't know anything about that (and I'm pretty sure TLS 1.3 doesn't mandate ECH since ECH isn't even finished standardizing!) but you can check to see if your browser supports ECH by visiting https://tls-ech.dev/ https://tls-ech.dev/
tialaramex 4y ago
Some people interested in the Great Firewall wrote up weirdness they saw with one particular prototype of eSNI years back. A game of Telephone later this became nonsense like "China blocks TLS 1.3" but actually if you do that what you get isn't web sites stripped of protection but connection errors. Which is indeed what happens for some sites from the other side of the Great Firewall, but we just say China blocks those sites, because that is what they do. Protocol versions are not crucial to them. The current iteration of ECH is designed to be GREASEd which means browsers might just always do ECH with dummy values regardless, so either you block or you don't, you won't be able to selectively block ECH. This doesn't magically prevent the Great Firewall from working but does mean specifically host matching is degraded as intended.
- 6502nerdface 4y ago
  > A game of Telephone Funny enough the children's "telephone game" is, in many Commonwealth countries, apparently called "Chinese whispers," at least according to my Londoner colleagues.
  - vmilner 4y ago
    Yes, I’m British and when American friends first used the word “Telephone” in conversation I was very confused.

vbezhenar 4y ago

And it means that state firewalls will just block all CDNs.

novok 4y ago
The idea is you force them to choose the entire effective internet or nothing, which is not an economic self own even most dictatorships are willing to make. These firewalls are an exercise in having your cake and eating it too.
- vbezhenar 4y ago
  CDNs are not entire effective internet. Also I'm not well-educated in that area, but I would expect that CDNs would allocate dedicated IP ranged for big customers like Microsoft or Apple. So state can ban more selectively, white-listing those ranges.
- saurik 4y ago
  But it doesn't end there... they block the CDN that implements this feature, and then the CDN's customers--who probably didn't care much about the benefits this gives to some of their users but are now losing access to some large customer base--start complaining and migrating off the CDN, which results in the CDN pulling back on the feature. And we know this is what will happen as this is effectively what happened with domain fronting--where you simply use the wrong SNI instead of hiding it entirely--with all the large CDNs actively "fixing" this feature to prevent their customer's websites from being blocked by firewalls because of users who were using this to get around hostname restrictions.
  - novok 4y ago
    Yup it's a cat and mouse game, and how much money these dictators represent. Thankfully? in the case of Iran, many customers do not want to interact with Iran because of US export regulations, so if it breaks that, all the better ironically enough.
    - 4y ago