SQL-based authentication

SQL-based authentication
You are encouraged to solve this task according to the task description, using any language you may know.

This task has three parts:

• Connect to a MySQL database (connect_db)
• Create user/password records in the following table (create_user)
• Authenticate login requests against the table (authenticate_user)

This is the table definition:

create table users (
    userid int primary key auto_increment,
    username varchar(32) unique key not null,
    pass_salt tinyblob not null,  -- a string of 16 random bytes
    pass_md5 tinyblob not null
            -- binary MD5 hash of pass_salt concatenated with the password
);

(pass_salt and pass_md5 would be binary(16) values, but MySQL versions before 5.0.15 strip trailing spaces when selecting them.)

Perl

Interpreter: perl 5.8.8

Libraries: DBI, DBD::mysql

use DBI;

 # returns a database handle configured to throw an exception on query errors
sub connect_db {
    my ($dbname, $host, $user, $pass) = @_;
    my $db = DBI->connect("dbi:mysql:$dbname:$host", $user, $pass)
        or die $DBI::errstr;
    $db->{RaiseError} = 1;
    $db
}

 # if the user was successfully created, returns its user id.
 # if the name was already in use, returns undef.
sub create_user {
    my ($db, $user, $pass) = @_;
    my $salt = pack "C*", map {int rand 256} 1..16;
    $db->do("insert ignore into users (username, pass_salt, pass_md5)
        values (?, ?, unhex(md5(concat(pass_salt, ?))))",
        undef, $user, $salt, $pass)
      and $db->{mysql_insertid} or undef
}

 # if the user is authentic, returns its user id.  otherwise returns undef.
sub authenticate_user {
    my ($db, $user, $pass) = @_;
    my $userid = $db->selectrow_array("select userid from users where
        username=? and pass_md5=unhex(md5(concat(pass_salt, ?)))",
        undef, $user, $pass);
    $userid
}

Raven

MySQL connectivity is available out of the box. Below, we do not ever send the plain text password over the wire.

 'mysql://root@localhost/test' open as mysql
'abcdefghijklmnopqrstuvwxyz0123456789' as $salt_chars

# return userid for success and FALSE for failure.
define create_user use $user, $pass
    group 16 each as i
        $salt_chars choose chr
    join as $pass_salt
     "%($pass_salt)s%($pass)s" md5 as $pass_md5
    $user copy mysql escape as $user_name
    group 'INSERT IGNORE into users (username, pass_md5, pass_salt)'
        " VALUES ('%($user_name)s', unhex('%($pass_md5)s'), '%($pass_salt)s')"
    join mysql query inserted

# return userid for success and FALSE for failure.
define authenticate_user use $user, $pass
    FALSE as $userid
    $user copy mysql escape as $user_name
    group 'SELECT userid, pass_salt, hex(pass_md5)'
        " FROM users WHERE username = '%($user_name)s'"
    join mysql query as rs
    rs selected
    if  rs fetch values into $possible_userid, $pass_salt, $pass_md5
        "%($pass_salt)s%($pass)s" md5 $pass_md5 lower =
        if  $possible_userid as $userid
    $userid

'foo' 'bar' create_user       !if "could not create user\n"       print bye
'foo' 'bar' authenticate_user !if "could not authenticate user\n" print bye

"user successfully created and authenticated!\n" print