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(crazyinsomniac) Re: Turn JavaScript off on HomeNodes

by crazyinsomniac (Prior)
on Sep 03, 2001 at 10:17 UTC ( #109821=note: print w/ replies, xml ) Need Help??


in reply to Turn JavaScript off on HomeNodes

That will not adequately strip javascript.

Slashdot|MS Security: On A Path As Clear As It Is Reliable pointed me to Expert hacks Hotmail in 1 line of code which in turn pointed me here, which reveals that STYLE tags in netscape will execute the stuff enclosed in style tags as javascript, if the TYPE attribute of the style tag is "application/x-javascript".

Your code: 56: $str=~s/<script[^>]*>.*?<\/script[^>]*>//igs if $$USER{jsoff};

My addition (you're welcome to improve):

#!/usr/bin/perl -w use strict; my $string = q|<STYLE TYPE="application/x-javascript" Language='Englis +h' TYPE="application/x-javascript">|; printf "%s\n", $string; $string =~ s<STYLE\s([^>]*)> { my $trt = $1; # $trt =~ s!type=\S+?(\s|"|')!TYPE="text/css"!igs; $trt =~ s!type=\S+?[ '"]!TYPE="text/css"!igs; qq(<STYLE $trt>) }eigsx; printf "%s\n", $string;
Also evil are object, applet and embed tags (i'm sure there are others).

update: a slightly smarter version

#!/usr/bin/perl -w use strict; my $string = q|<STYLE TYPE="application/x-javascript" Language='Englis +h' TYPE="application/x-javascript">|; printf "%s\n", $string; $string =~ s<STYLE\s([^>]*>) { my $trt = $1; # $trt =~ s!type=\S+?(\s|"|')!TYPE="text/css"!igs; $trt =~ s!type=\S+?[ '">]!TYPE="text/css"!igs; $trt .= '>' if substr($trt,-1,1) ne '>'; qq(<STYLE $trt) }eigsx; printf "%s\n", $string;
update: OeufMayo says in the cb, what about: <a href="#" onClick="alert('evil javascript here');">

Well I thought htmlScreen would take care of it, but you do override the filter

$str.=htmlcode('parselinks','doctext,override'); ... in parselinks ... $text=htmlScreen($text,$APPROVED) unless $overridefilter eq "override" +;

 
___crazyinsomniac_______________________________________
Disclaimer: Don't blame. It came from inside the void

perl -e "$q=$_;map({chr unpack qq;H*;,$_}split(q;;,q*H*));print;$q/$q;"


Comment on (crazyinsomniac) Re: Turn JavaScript off on HomeNodes
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Re (tilly) 2: Turn JavaScript off on HomeNodes
by tilly (Archbishop) on Sep 03, 2001 at 17:40 UTC
    A few well-chosen RE substitutions cannot be safe. But the safe approach would be a major change to the overall parsing logic of the site, and I am loathe to tackle that without a fair block of time and a safe development environment to play around in.
Re: (crazyinsomniac) Re: Turn JavaScript off on HomeNodes
by Ven'Tatsu (Deacon) on Sep 04, 2001 at 02:39 UTC
    Also beware of onMouseOver, onMouseMove, onMouseOut, and onError. They can start a script with out the user making any obvious interaction. Realty any /\son.+/ in a tag should get killed.

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