AFAIK, the authentication is per-database, which means it has to read the database name from the client before authenticating, even if you are using certificates.
The bug in question involved the client sending an invalid database name.
Posted Apr 7, 2013 22:40 UTC (Sun) by hummassa (subscriber, #307)
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IIRC correctly my SSL/TLS, the authentication (and the start of encrypting the whole session) comes before anything else. I suppose when the client asks for connection to a database, he is already autheticated via his cert (and the dbms can check if he can effectively connect to *that* particular db).