Possible regression: libpq + SSL aborts when user has no home directory

Using libpq 9.0.3, when an SSL connection is attempted from a client
whose EUID is not in a password database, the connection fails because
the home directory cannot be determined. With libpq 8.4.7, everything is
fine.

I encountered this issue on my mail host, where I use virtual users.
When mail is delivered, parameters such as UID, home directory, etc. are
retrieved using multiple queries against a Postgres DB.

As soon as the virtual user's UID (which does not exist in any local
password database) is determined, exim setuid()s to it. All further
queries then fail with an error similar to this one:

PGSQL connection failed: could not get home directory to locate client
certificate files
FATAL: no pg_hba.conf entry for host "1.2.3.4", user "exim4", database
"fake_name", SSL off

Looking at interfaces/libpq/fe-secure.c, it seems that such a failure
previously only occurred when sslmode was "verify-*", otherwise the
missing home dir was ignored. Now, it always fails.

It was pointed out to me that the client-side SSL stuff changed in
9.0.3, so this might be entirely valid. I was just a little suprising.

Regards,
Christian