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| ▲ | hypeatei 2 hours ago | parent [-] | | Just enabling ECH doesn't stop this, firewalls can see it and mangle the data to force a downgrade because most servers need to support older protocols. It's more accurate to say that once sites only support ECH, then they'll be forced to stop downgrading or deal with angry users. | | |
| ▲ | ronsor an hour ago | parent | next [-] | | TLS 1.3, including the ECH extension, does not permit downgrading, unless your implementation is broken. Trying to downgrade or strip extensions from any TLS 1.3 connection will simply break the connection. | | |
| ▲ | hypeatei an hour ago | parent [-] | | In the wild, that's not true at all[0][1]. The corporate firewall at my employer actually wasn't able to block ECH until they updated it then it was able to block sites as usual. 0: https://community.fortinet.com/t5/FortiGate/Technical-Tip-Ho... 1: https://docs.broadcom.com/doc/symantec-ech-whitepaper (see page 8) | | |
| ▲ | dilyevsky 33 minutes ago | parent | next [-] | | I ready the FortiGate link and this is the gist: The DNS filter setting on the FortiGate analyzes the DoH traffic and strips out the ECH parameters sent by the DNS server in the DoH response. If the client does not receive those parameters, it cannot encrypt the inner SNI, so it will send it in clear text.
So basically they mess with DoH ECH config and trigger fallback behavior in the clients. I don't think any browsers do this yet but I think this loophole is not gonna last. | |
| ▲ | dilyevsky 43 minutes ago | parent | prev [-] | | This is literally impossible. What your corp fw likely does is mitm outer SNI because your IT department installed your company CA in every client's trust store. So unless you do that at national level your only other option is to block ECH entirely. Edit: actually totally possible but you need build quantum computer with sufficient cubits first =) |
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| ▲ | hsbauauvhabzb 43 minutes ago | parent | prev [-] | | Is there even a push for ECH? I don’t imagine big tech and other powerful players particularly want it. |
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