From: Jeff Bryner (jbryner1@yahoo.com)
Date: Thu Mar 25 2004 - 12:06:06 EST
--- "Lachniet, Mark" wrote:
> Actually, I believe .NET does convert the naughty strings to safe
> representations that are not interpreted as HTML by the browser, in
> the
> body anyway...
I just dealt with this in an app yesterday. It doesn't do any of that
automatically..you've got to catch the exception at the application
(not page) level and then explicitly handle the validation exception.
You can turn the validation off and then htmlencode input, but that
defeats the whole purpose of the css validation check. I think this is
one area where msoft has done what people have been asking for years.
Turn security on by default, make it a distinct choice to take handling
unsafe input on yourself and give you the tools to do it.
> However, it does *not* do this in the headers - esp. the "Location:"
> header. But how difficult is this to exploit in the real world?
It would be interesting to try some of the caching vulnerabilities, or
inject something in the server variables which also aren't
checked...haven't had time yet.
> > -----Original Message-----
> > From: Frank Knobbe [mailto:frank@knobbe.us]
> > But isn't that all it does? I mean, you are still left with
> > converting the content of the caught string yourself, using
> > HTMLEncode or similar.
If you try/catch the exception, otherwise your web application will
barf up a server error. (it treats it as a http 500 error) i.e. if .net
catches it and you don't you'll never see the string.
> > In other words, all it does is detect that dangerous
> > characters are present. It doesn't protect you by converting them.
It interrupts the application on detection of dangerous strings. You've
got to code specifically for receiving dangerous strings that it
detects.
> > Which means you are still left to do the conversion (and
> > space trimming, and cutting to maxlength....) yourself...
True, it's not a check for sql injection or buffer overflow or format
string protection. Just a css validation check. Got to use those
regular expressions....
=====
Jeff
-----------------------
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