I remember in TLS 1.3, a middle box can not modify a single byte in the negotiation, or otherwise, the connection fails (a checksum validation on server and cli

I remember in TLS 1.3, a middle box can not modify a single byte in the negotiation, or otherwise, the connection fails (a checksum validation on server and client side). TLS 1.2 somehow has this but the coverage is less (it only happens for chipers etc).