SSH: TerrapinAttack
Terrapin Attack: Breaking SSH Channel Integrity By Sequence Number Manipulation
mitm条件下，操纵handshake sequence计数，drop关键extinfo，实施downgrade attack。
symmetric cipher mode影响, something synced is influnenced by seq number。
核心还是full transcript hash，参考sequence number reset, handshake与record互不影响；end-of-communication message，标识h结束。