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                             Luigi Auriemma

Application:  Abyss webserver
              http://www.aprelium.com
Versions:     minors than 1.2
Platforms:    Linux version only
Bug:          Bypassing of password protected folders authorization on
              FAT32 filesystems
              (but rarely users use Linux to run a webserver on a FAT32
              partition)
Exploitation: remote through browser
Date:         08 Dec 2003
Author:       Luigi Auriemma
              e-mail: aluigi@autistici.org
              web:    aluigi.org


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1) Introduction
2) Bug
3) The Code
4) Fix


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===============
1) Introduction
===============


Abyss webserver is a nice and tiny free closed-source web server
developed for Win32, Linux x86, MacOS and FreeBSD platforms.


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======
2) Bug
======


The bug is a protection bypassing but it happens only on Linux when the
protected folder is on a FAT32 system. Probably is a bit unusual that
someone uses a webserver for Linux to share a FAT32 directory but Abyss
is very useful for fast configurations and for personal usages so
this is not a rare case (... in fact I have found this bug just because
I was sharing a FAT32 dir...).

Practically if the admin runs Abyss webserver on Linux and has a FAT32
directory protected by password an attacker can bypass the
authorization simply adding a dot or an HTTP encoded dot (%2e) at the
end of the URL.

The developers have reported that also the chars space (' ', %20) and
':' (%3a) cause the same problem (but on my system they cause only a
right 404 error).


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===========
3) The Code
===========


http://linux_server/protected_FAT32_dir.
http://linux_server/protected_FAT32_dir./
http://linux_server/protected_FAT32_dir%2e


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======
4) Fix
======


Version 1.2 released the 3th Dec 2003


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