zlacker

>>codero+(OP)
Note that this happens even when using a BlueCoat proxy in non-MITM mode. BlueCoat tries to "analyze" TLS connections, and rejects anything it doesn't understand. This exact issue occurred with TLS 1.2 back when BlueCoat only understood 1.1/1.0.

In this case, it doesn't sound like they're reverting it because of overall breakage, but rather because it breaks the tool that would otherwise be used to control TLS 1.3 trials and other configuration. Firefox had a similar issue, where they temporarily used more conservative settings for their updater than for the browser itself, to ensure that people could always obtain updates that might improve the situation.

>>JoshTr+w
Rejecting anything it doesn't understand sounds like a bug to me. If it sees that it's TLS, it should attempt a protocol downgrade. There's absolutely no reason for this to break, as TLS 1.3 exists alongside TLS 1.2 (For now).

>>codero+31
It's a security feature, often malware will send encrypted traffic over 443 in an attempt to bypass firewalls. If BlueCoat can't understand the traffic, it drops it as it assumes it's malicious.

>>234dd5+x6
But the traffic is totally understandable -- the right action does not require knowing what TLS 1.3 is.

The way it is supposed to work is as following: there is a protocol negotiation when the connection is established (which is obviously unencrypted), which contains TLS version supported. If MITM proxy does not understand the version, it can just change these bytes to force hosts to negotiate at a lower version.

So the only reason BlueCoat fails is because the authors failed to implement force version downgrade.