Programming interfaces when using MD5 authentication

Hi,

I apologise in advance if this is considered the wrong list to post  
onto. I couldn't find specific details for joining a DBD::Pg style  
mailing list so I'm hoping this is something that's relatively well  
known about by general PostgreSQL developers anyway.

Using Perl to program interfaces to PostgreSQL, and had previously  
misunderstood how md5 password authentication worked, so I'm now re- 
doing it, but struggling to find out how DBD::Pg might be used to  
actually authenticate by passing an md5 of the password instead of the  
real thing.

I understand from various reading that the md5 should be a double- 
process consisting of:

phase1 = md5(password  username)
password_to_use = md5(phase1  salt)

What I don't understand is how to "extract" the salt required to  
complete the second phase.

Effectively what I'm hoping for is to be able to do something along  
the lines of:

---------------------------------------------------------------
#!/usr/local/bin/perl -w

use strict;
use DBI;
use Digest::MD5 qw(md5_hex);
use DBD::Pg;

my $user = "currentuser";
my $pass = md5_hex("supersecretpassword" . $user);

my $dbh = DBI->connect("dbi:Pg:dbname=monitoring","$user",$pass,  
{ PrintError => 1 });
if (defined($dbh)) {
	$dbh->disconnect();
	print "Successful\n";
} else {
	print "Failed!!\n";
}
---------------------------------------------------------------

In the above, if I prepend "md5" to the $pass variable I obviously get  
what exactly matches the content of the pg_shadow table entry for the  
given user ... however, either way the connection isn't successful  
because (from what I've been able to discern) I actually need to submit:

md5  md5($pass  salt)

Can DBD::Pg be used for these connections? If anyone has experience in  
this I'd much appreciate your thoughts or suggestions. (I realise the  
"connect" function is from DBI, but it seems to me that the use of the  
salt required to properly authenticate will be specific somehow to  
DBD::Pg usage.)

Cheers,

Preston.

--
Preston de Guise
http://www.enterprisesystemsbackup.com