Serious problem within authentication subsystem in 7.0

Hi,

Ok, I know the mailing list web page states: YOU MUST TRY ELSEWHERE FIRST! and
this should, technically speaking, be reported as a bug however given that the
security implications are potentially severe I thought here would be best in
the first instance.

I have only briefly looked into this problem as I have just now discovered it.
Essentially, in our environment, we require password authentication as a
defacto. However it appears that once a user has authenticated with the
backend it is possible for that user to trivially assume root dba privileges or
privileges of any other dba user.

To demonstrate the problem:

Consider two systems:

pgsqlserver 192.168.1.1 - backend system
pgsqlclient 192.168.1.2 - client system

Our pg_hba.conf (on pgsqlserver) now looks something similar to:

local all password
host all 127.0.0.1 255.255.255.255 password
host all 192.168.1.2 255.255.255.255 password

Now making connections from pgsqlclient (192.168.1.2) would require password
authentication. To show that this works, entering an incorrect passwd...

pgsqlclient:/home/matt 11:33am > psql -h pgsqlserver -U matt matt
Password:
psql: Password authentication failed for user 'matt'

Now a correct password:

pgsqlclient:/home/matt 11:36am > psql -h pgsqlserver -U matt matt
Password:
Welcome to psql, the PostgreSQL interactive terminal.

Type: \copyright for distribution terms
\h for help with SQL commands
\? for help on internal slash commands
\g or terminate with semicolon to execute query
\q to quit

matt=>

Ok, so at the top level password authentication works, now to the problem...

Once authenticated it is possible to trivially assume another users identity
without further authentication e.g.

matt=> \c template1 postgres
You are now connected to database template1 as user postgres.
template1=#

Or, assume any other users identity:

matt=> \c www www
You are now connected to database www as user www.
www=>

Ouch.

I have not tested to see if this is specific to the password authentication
method or a general problem relating to any of the supported methods and I have
limited time to investigate this at the moment.

Is there anyone who specifically maintains the authentication subsystem that I
could communicate with directly? I would be interested to offer whatever
assistance I can.

Regards,
Matt.