Re: strange behavior of pg_hba.conf file

On 11/22/23 09:03, Atul Kumar wrote:
> The entries that I changed were to replace the md5 with scram-sha-256 
> and remove unnecessary remote IPs.

FYI from:

https://www.postgresql.org/docs/current/auth-password.html

md5

     The method md5 uses a custom less secure challenge-response 
mechanism. It prevents password sniffing and avoids storing passwords on 
the server in plain text but provides no protection if an attacker 
manages to steal the password hash from the server. Also, the MD5 hash 
algorithm is nowadays no longer considered secure against determined 
attacks.

     The md5 method cannot be used with the db_user_namespace feature.

     To ease transition from the md5 method to the newer SCRAM method, 
if md5 is specified as a method in pg_hba.conf but the user's password 
on the server is encrypted for SCRAM (see below), then SCRAM-based 
authentication will automatically be chosen instead.

> 
> But it has nothing to do with connecting the server locally with "psql 
> -d postgres -U postgres -h localhost"

The error:

no pg_hba.conf entry for host "::1", user "postgres", database "postgres


says it does and the error is correct as you do not have an IPv6 entry 
for localhost in pg_hba.conf. At least in the snippet you showed us.


> 
> But when I try to connect it locally I get this error. So it is related 

When you say connect locally do you mean to localhost or to local(socket)?

> to local connections only and when I pass the hostname or ip of the 
> server it works fine without any issue.
> 
> 
> Regards.
> 

-- 
Adrian Klaver
adrian.klaver@aklaver.com