[PATCH] pg_hba.conf : new auth option : clientcert=verify-full

Dear Postgresql Hackers,

as of now, pg_hba.conf allows us to enable authentification by
certificate through the auth-method "cert", in which case the user must
provide a valid certificate with a certificate common name(CN) matching
the database user's name or an entry in a pg_ident map.

Additionaly, for every other auth-method it is possible to set the
auth-option "clientcert=1", so clients must present a valid certificate
at login. The logic behind this only checks the validity of the
certificate itself, but the certificate common name(CN) is not
relevant.

I wrote a very small patch that adds another auth-option:
- clientcert=verify-full (analogous to server certificates; you could
also use 2 instead of verify-full for backwards compatibility, or
verify-ca instead of 1)
which also checks the certificate common name,
so all 3 factors get checked:
1.) auth-method, e.g. scram or md5 password passes
2.) client cert is in truststore
3.) CN is correct.

(The patch simply makes use of the function that is used for auth-
method "cert" to avoid code duplication).

Have a nice weekend,
Julian Markwort