Re: BUG #14661: authentication behavior(SCRAM-MD5)

On 05/19/2017 06:05 PM, asotolongo@gmail.com wrote:
> i think that is correct, but when i have the next configuracion:
> pg_hba.conf
> host    all             usuario         0.0.0.0/0            md5
> host    all             postgres        0.0.0.0/0            md5
>
> and my user with SCRAM encryption
> postgres=# select usename,passwd from pg_shadow ;
>  usename  |
> passwd
> ----------+-------------------------------------------------------------------------------------------------------------------------------
>  usuario  |
> SCRAM-SHA-256$4096:Fhqo2W7V4FlVQk7+$fkQJ02YBGMhePbhVnKOcHjON/VPUTDzT/pZboiwHofY=:XliKl0leu/kpN4ZGmNPnHKKWj76f7qN8lIjrY8jOVcA=
>  postgres |
> SCRAM-SHA-256$4096:5DcjppjZNyrGb0Jo$iomUsf0Mo0RSSjkwzhwHwRphhVG5EKLRRMVp/eiENuI=:XFIOQcd1nA1IKclPrVSwFym9N5dLuYB43CfI3Lf5zGA=
> (2 filas)
>
>
> and when try to  login, login successfully
> is correct this behavior?

Yeah, "md5" in pg_hba.conf really means "md5 or scram-sha-256, depending 
on what kind of password hash the user has".

The documentation at 
https://www.postgresql.org/docs/devel/static/auth-methods.html#auth-password 
tries to explain it:

> scram-sha-256 performs SCRAM-SHA-256 authentication, as described in
> RFC5802. It is a challenge-response scheme, that prevents password
> sniffing on untrusted connections. It is more secure than the md5
> method, but might not be supported by older clients.
>
> md5 allows falling back to a less secure challenge-response mechanism
> for those users with an MD5 hashed password. The fallback mechanism
> also prevents password sniffing, but provides no protection if an
> attacker manages to steal the password hash from the server, and it
> cannot be used with the db_user_namespace feature. For all other
> users, md5 works the same as scram-sha-256.


- Heikki