Here is an implementation in perl:

PostgreSQL SCRAM-SHA-256 authentication

#!/usr/bin/perl
# Copyright: 2024 - Guido Brugnara <[email protected]>
# Licence: This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
use Crypt::Salt;
use Crypt::KeyDerivation qw(pbkdf2);
use Crypt::Mac::HMAC qw(hmac hmac_b64);
use Crypt::Digest::SHA256 qw(sha256_b64);
use MIME::Base64;
my $salt = Crypt::Salt::salt(16);
my $iterations = 4096;
my $password = <STDIN>;
chomp $password;
my $digest_key = pbkdf2($password, $salt, $iterations, 'SHA256', 32);
my $client_key = hmac('SHA256', $digest_key ,'Client Key');
my $b64_client_key = sha256_b64($client_key);
my $b64_server_key = hmac_b64('SHA256', $digest_key, 'Server Key');
my $b64_salt = encode_base64($salt, '');
print "SCRAM-SHA-256\$$iterations:$b64_salt\$$b64_client_key:$b64_server_key\n";