RE: Source Evaluation?

I agree, Joe.  This applies to all CGI programming, not just Java, though
(which should be pointed out for anyone lurking <bg>).

Brad

> -----Original Message-----
> From: Joe Teff [mailto:JoeTeff@earthlink.net]
> Sent: Saturday, February 10, 2001 2:28 PM
> To: JAVA400-L
> Subject: RE: Source Evaluation?
> 
> 
> I would make a slight change to your routine that writes 
> dynamic data as
> HTML:
> 
>    public void writeDetail(String[] fieldList, ResultSet rs, 
> PrintWriter
> out) {
>      try {
>        while(rs.next()) {
>          out.println("</tr><tr>");
>          for(int i=0; i<fieldList.length; i++) {
> 
>            out.println("<td>" + 
> encode(rs.getString(fieldList[i]).trim()) +
> "</td>");
>          }
>        }
>      } catch (Exception e) {
>        out.println("<br>Error Message (writeDetail): " + e);
>      }
>    }
> 
> This is an example of an encode() method:
> 
>    public static String encodeData(String str) {
>      StringBuffer encoded = new StringBuffer(str.length()*2);
>      for (int i=0; i<str.length(); i++) {
>        switch (str.charAt(i)) {
>          case '<'  : encoded.append("&#60;"); break;
>          case '>'  : encoded.append("&#62;"); break;
>          case '"'  : encoded.append("&#34;"); break;
>          case '\'' : encoded.append("&#39;"); break;
>          case '%'  : encoded.append("&#37;"); break;
>          case ';'  : encoded.append("&#59;"); break;
>          case '('  : encoded.append("&#40;"); break;
>          case ')'  : encoded.append("&#41;"); break;
>          case '&'  : encoded.append("&#38;"); break;
>          case '+'  : encoded.append("&#43;"); break;
>          default   : encoded.append(str.charAt(i));
>        }
>      }
>      return encoded.toString();
>    }
> 
> This is a standard defense against one of the hacking 
> techniques. Imagine
> if someone had keyed the following into a field like an address:
> 
>     [script]alert('Hi fathead!');[/script]
> 
> (The mailing list bounced my original message because of the 
> beginning and
> ending script tags. You'll have to substiture <> for [] in my 
> example.)
> 
> Anybody that knows a little about JavaScript can see what will happen
> if this data was included in your HTML. Imagine the kind of 
> things that
> you could do.
> 
> Joe Teff
> 
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