Argon2 encryption in perl - perl

Question

I'm making simple perl script for sign up/login with Argon2 for encryption. (The credentials are taken from HTML Forms). The creation of users works fine , username and hashed password are stored in the database. The problem comes with the extraction/authentication. I'm not sure I'm using the verification properly.
#!/usr/bin/perl
use strict;
use warnings;
use Crypt::Argon2 qw/argon2id_pass argon2id_verify/;
use CGI::Simple;
use DBI;
sub get_data{
my ( $user) = #_;
my $statement = "SELECT USER_HASH FROM LOGIN_DATA WHERE USER_NAME = ?";
my $driver = "mysql";
my $database = "USERS";
my $dsn = "DBI:$driver:database=$database";
my $dataUsr = "user";
my $dataPass = "user123";
my $dbcon = DBI->connect($dsn,$dataUsr,$dataPass) or die $!;
my $preState = $dbcon->prepare($statement);
$preState->execute($user);
my #row ;
my $hash_pass;
while(#row=$preState->fetchrow_array()){
$hash_pass = $row[0];
}
return $hash_pass;
}
sub check_pass{
my ($user , $pass) = #_;
my $encoded = get_data($user);
return argon2id_verify($encoded , $pass);
}
my $cgi = CGI::Simple->new;
my $username = $cgi->param("username");
my $password = $cgi->param ("password");
check_pass($username , $password)
This are the erors when i try to run in in the terminal Use of uninitialized value in subroutine entry at checkUser.cgi line 30. Could not verify argon2id tag: Decoding failed at checkUser.cgi line 30.

Answer 1

Removing all the CGI, all the database connectivity and replacing the input with dummy values shows the same error message, so my guess is that you are not getting a result from the database:
#!/usr/bin/perl
use strict;
use warnings;
use Crypt::Argon2 qw/argon2id_pass argon2id_verify/;
sub check_pass{
my ($user , $pass) = #_;
return argon2id_verify(undef, $pass);
}
check_pass("mytest", "some-test-password-2018")
__END__
Use of uninitialized value in subroutine entry at tmp.pl line 7.
Could not verify argon2id tag: Decoding failed at tmp.pl line 7.
So the best step would be for you to isolate the problem by verifying that you actually get a result from the database.