Re: Web Forms filtered with SQL constraints

[tie <tie () ankh morp org>]

Hi Bénoni,

Getting the source of your JavaScript code is always possible - no 
matter what tricks you apply. Denying right-click, hover over or 
whatever else you can think of will not save your code from prying eyes. 
After all , the code is transmitted in clear text between you and the 
server . You can use many applications (apart from browsers) to get the 
source - see Achilles for example. Hiding your JavaScript sources 
however, should not be your concern.

JavaScript is a CLIENT-side scripting language.  It is getting 
interpreted on the CLIENT side. And client=attacker. The attacker has 
full control on any code that is executed on his PC. So, the attacker 
can easily just skip your JavaScript checks and here you are with 
unverified input. You don't need to see/analyze the validation checks 
when you can just skip them :)

You cannot provide security through JavaScript. It is only used to 
provide convenience to your 'legal' visitors. Your server-side .ASP 
scripts should NEVER rely on client-side input validation. Big No-No here.

Instead, you should verify the input inside your .ASP scripts, on the 
server side. Validate them, as there is no client-side checking at all - 
there is really none,  from the attacker's point of view.

Regards,
tie

Bénoni MARTIN wrote:

> Hi list !
>
> I was wondering how to solve the 2 following problems: I have ASP (not ASP.NET) formulaires people have to fill in. To avoid 
> SQ injection attacks and other tricks, I have set up some Jscript filtering on each field (i.e. for instance a name can just 
> be alphabet's characters and no figures :) ), and I am planning to do the same on my Database (setting up constraints).
>
>
> But I have 2 questions:
>         - How can I hide my Jscript filtering from the user ? When I want to see the source, everything is diaplayed, quite normal :( 
> ... Maybe it's not so good to tell people what I have done to filter them :) I saw some sites where it is impossible to see the 
> source, impossible to "hoover the site", impossible even to print ... But I have not been able to find on the net how to do 
> this :(
>
>         - How can I deal with possible SQL errors within an ASP page ? I mean, if a field has been filled in, bypass my Jscript 
> filtering (no matter how), and gets to the database but is then "stopped" by an SQL onstraint, how do I raise this 
> error on an ASP page without diplaying an explicit error (giving the user the name of my database for instance) ?
>
> Cheers for any clue, I am lost on this topic :(
>
>
>
>