Re: TA-2003-06 Directory Transversal Vulnerability in iWeb Server

[Rushjo@tripbit.org]

Hi akcess,


thx for your feedback. But not all of your comments are right.
First I wrote this in the advisory:

[qoute]
The vendor has reportedly been notified. But the vendor told us that is
an old bug. We don't think so.
[/ qoute]

Alright perhaps next time it will be better to mention the url of the
old bug. And of course it is an "another form of the old bug" but did
you really read the old advisory? For example the recommended solution?

[quote]
* taken from http://securityfocus.com/archive/1/318775 *

......:[ Vendor Status :

14/04/03 Initial Contact Made
15/04/03 Vendor Responded
15/04/03 Vendor Released Updated Version

......:[ Solution :

Remove old iWeb application and download and install the updated
version which can be found at:

http://ashleybrown.co.uk/downloads/iws2.exe
[/qoute]

And this is the point. We tested the "safe" iWeb Server2 and still found
this bug. So we don't think that it is fixed. Because of the reaction of
the vendor we deceided to post this here.

And of course thanks for hints to posidron's "work". He "rebuilded" this
tool with the help of your hints.


Have a lot of fun

Rushjo

[Steven M. Christey]

There are so many variants to directory traversal vulnerabilities,
especially in web servers and other software where encoding and
canonicalization is such a factor, that I have seen a number of
confusing cases such as this.

It definitely helps when the researcher who discovers a new variant
specifically references the old variant and says how the underlying
problem is different. This doesn't seem to happen too frequently,
though, and distinguishing between variants gets much more difficult
when it is not known if the vendor has fixed the original variant.

In this case, it looks like the programmer introduced what I call a
"validate-before-canonicalize" error, for lack of a better term: the
software may well strip ".." sequences from the input (the original
bug), but the programmer does this cleansing *before* the operation
that does the URL decoding (kind of like a new bug - performing
operations in the wrong order).

As programmers have slowly gotten better about avoiding the obvious
directory traversal issues, these "validate-before-canonicalize"
errors seem to be cropping up more frequently.


- Steve