how to properly secure non-ssl logins (php + ajax)

[Lea Kissner]

[Moderator's note: top posting is not considered good form. --Perry]

Hi Rene,

I suspect from reading this quickly that you may not be a cryptographer. I'd
highly suggest that you borrow one for a bit before you go ahead with this.
I'm having a bit of trouble reading exactly what you want to do, but I am
fairly sure that this isn't as secure as you'd like. (Heck, I can probably
help you out with this, but not today because I'm swamped.)

Thanks,
Lea

On Sun, Feb 15, 2009 at 4:30 AM, Rene Veerman <rene7705 at gmail.com> wrote:

> Hi.
>
> Recently, on both the jQuery(.com) and PHP mailinglists, a question has
> arisen on how to properly secure a login form for a non-ssl web-application.
> But the replies have been "get ssl".. :(
>
> I disagree, and think that with a proper layout of authentication
> architecture, one can really secure a login system without having the
> administrative overhead of installing SSL everywhere, and the monetary cost
> for a SSL certificate for each domain.
>
> I wish to code such a solution into a really-free library (so probably LGPL
> or GPL + MIT) over the next 2 to 5 months.
> This library would be a complete SQL, PHP & javascript package (jQuery
> "plugged in"), targetted for the novice programmer.
>
> I'm halfway (or more?) there, i think.
> For my own CMS, i have taken the following approach, which i'd like to hear
> your improvements on:
>
> (For onewayHash() i have MD5 and SHA256 implementations in both JS and
> PHP..)
>
> //// SQL:
>
> create table users (
>  user_id                   integer,
>  user_login_name      varchar(250),
>  user_login_hash      varchar(250),
>  user_password_hash   varchar(250),
> ....other fields....
> primary key (user_id)
> );
>
> create table preferences (
>  pref_system_hash   varchar(250)
> ....
> );
>
> //// PHP (pseudo-code) , on system installation:
>   preferences.pref_system_hash = onewayHash ( randomStringLength(100) );
>
> //// PHP , on user-create:
>
>  users[user_id].user_login_hash = onewayHash(user_login_name +
> preferences.pref_system_hash);
>  users[user_id].user_password_hash = onewayHash ("someGooodPasswordNot" +
> preferences.pref_system_hash);
>
> //// PHP, on request of a login form:
>
>  challenge = makeNewChallenge ();
>       //checks since when [browser IP] has last received a new challenge,
> if < threshold : make a new challenge. else return old challenge.
>      //a challenge is a random string (+ special chars) pushed through the
> onewayHash function.
>
>  html = '
>      <form id="loginForm">
>         <input type="hidden" id="sh" name="sh"
> value="preferences.pref_system_hash">
>         <input type="hidden" id="ch" name="ch" value="challenge">
>         <input id="plain_user" name="plain_user"/>
>         <input id="plain_pass" name="plain_pass"/>
>         <input type="hidden" id="user_hash" name="user_hash"/>
>         <input type="hidden" id="pass_hash" name="pass_hash"/>
>      </form>
>   ';
>   sendHTMLtoBrowser (html);
>
> //// Javascript: on page with login form:
>
>   jQuery('#loginForm').submit (function () {
>         var sh = jQuery('#sh')[0]; //same for ch, plain_user, plain_pass,
> all the inputs in the html form.
>         ....
>
>         user_hash = onewayHash ( onewayHash ( plain_user.value + sh.value )
> + challenge );
>         //same for pass_hash basically
>
>         plain_user.value = ''; //clear out the plain text fields so they
> dont get transmitted (same for plain_pass ofcourse)
>
>         jQuery.ajax ( /* submit login form through POST, handle results */
> )
>   }
>
>
> //// PHP, on receiving the login form data:
>
>      // walk through all the records in users table, for each, calculate:
>         user_hash = onewayHash ( users[user_id].user_login_hash + challenge
> );
>         pass_hash = onewayHash ( users[user_id].user_password_hash +
> challenge );
>
>      // if they match what was sent, then it's the user we're looking for
> with the right password, so their $_SESSION['authenticated_user'] = updated.
>
> ////
>
>
> If you have a completely alternative way of securing a non-ssl login form,
> i'd like to hear about it too.
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