Single Signon, how?

[Trek]

I've done several forum searches here as well as the web in general and haven't really found anything that has answered the question. Several threads about people doing it, but not how they did it.

In short, I have two systems. When someone logs into the "other" system, I want them to seamlessly (ie, behind the scenes) be logged into vB as well.

Ideally I would have a function that I could call that I would pass the Username and password the user has entered (from the other system) into it, have this function authenticate whether it's a good match or not. If it's a good match, it should log the person into vB and return a true value, if it fails, it should return either just false or an error message.

Any help on this would be very much appreciated, thanks!

--------------- Added [DATE]1284609922[/DATE] at [TIME]1284609922[/TIME] ---------------

Ok, I'm getting closer, could use help though! =)

Using the below code in any PHP file, replace the DOMAIN, USERNAME and PASSWORD areas with appropriate info.

When you run it, it says "Thank you USERNAME for logging in." and all looks well. However, you aren't actually logged in. Seems as though it just passes the general verification, but doesn't do any of the session variables and/or cookies.

That's where I need the help, any idea what next?

<?
    $forum_root = "http://www.DOMAIN.com/";
    $login_page_url = $forum_root."login.php?do=login";
    $postfields["vb_login_username"] = "USERNAME";
    $postfields["vb_login_password"] = "PASSWORD";

    $ch = curl_init();
    curl_setopt($ch, CURLOPT_URL, $login_page_url);
    curl_setopt($ch, CURLOPT_POST, 1);
    curl_setopt($ch, CURLOPT_TIMEOUT, 100);
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

    $postfields["s"] = "";
    $postfields["SECURITYTOKEN"] = "guest";
    $postfields["do"] = "login";
    //$postfields["vb_login_md5password"] = "";
    //$postfields["vb_login_md5password_utf"] = "";

    ?>
    <script type="text/javascript" src="<? echo $forum_root; ?>clientscript/vbulletin_md5.js?v=406"></script>
    <SCRIPT LANGUAGE="JavaScript" TYPE="TEXT/JAVASCRIPT">
    <!--
        md5hash(vb_login_password, vb_login_md5password, vb_login_md5password_utf, 0)
    //-->
    </SCRIPT>

    <?
    curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
    $cdata = curl_exec($ch);
    curl_close($ch);
    
    echo "<hr>$cdata<hr>";
    

?>

--------------- Added [DATE]1284666786[/DATE] at [TIME]1284666786[/TIME] ---------------

No one? Not even a nudge in the right direction?