RE: [PHP] what do i need to disable

[Robert Cummings]

On Thu, 2007-02-08 at 15:32 -0700, Don wrote:
> > I asked this question awhile ago and never really visited the issue till
> > now. The response I got showed me how to disable everything, but I want to
> > allow basic html tags.
> 
> 
> http://us3.php.net/strip_tags
> 
> You can use the optional second parameter to specify tags which should not
> be stripped. 
> 
> HTH,
> 
> Brad
> 
> 
> I ended up using strip_tags (thanks Brad)
> 
> But to disable other ways of getting javascript to run I also included
> this....
> 
> $pattern =
> array('/(javascript)/','/([jJ(&#106)][aA(&#97)][vV(&#118)][aA(&#97)][sS(&#11
> 5)][cC(&#99)][rR(&#114)][iI(&#105)][pP(&#112)][tT(&#116)])/','/(\.[jJ(&#106)
> ][sS(&#115)])/','/([xX][sS(&#115)][sS(&#115)])/','/([xX][mM][lL])/');
> 
> $candidateNewBio = preg_replace($pattern, '', $candidateNewBio);
> 
> Is this worthwhile or a waste of time, because it seems to really protect
> your site, you need have a contingency for every possible attack.... And I
> don't even know how some of this stuff is even working with my level of
> understanding

Like a previous poster said... you need to be smarter than that. Markup
the entire document via htmlspecialchars() then replace basic tags with
real tags. So...

<?php

    $safe = htmlspecialchars( $content );
    $safe = str_replace( '&lt;b&gt;', '<b>', $safe );

?>

Better yet, switch to something like BBCode. Why you ask... because
let's say you do the following:

<?php

    $safe = strip_tags( $content, '<b>' );

?>

All Joe Hacker needs to do is submit the following:

-----
This is tricky <b onmouseover="document.location = 'www.mypr0n.com';">
-----

This line of attack is clearly warned about in the documentation for
strip_tags().

Cheers,
Rob.
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