Application: Novell Client <= 4.91 SP4

Web Site: http://www.novell.com/products/clients/

Platform: Windows

Bug: Local Stack overflow / B.S.O.D (unauthentificated user)

Impact: Critical
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1) Introduction

2) Bug

3) Proof of concept

4) Credits

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1) Introduction

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"Novell Client™ 4.91 for Windows XP is workstation software that brings an easy-to-use, secure,
and manageable networking environment to Windows XP and Windows 2003 users.
It enables you to access NetWare® services from Windows XP workstations or 2003 Windows servers,
and tightly integrates either product into your NetWare network. For example,
with Novell Client for Windows XP, you can browse through authorized NetWare directories,
transfer files, print documents and use advanced NetWare services directly from a Windows XP workstation or Windows Server 2003."


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2) Bug

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There's a funny bug in novell client, a while ago a stack based overflow was present in the username field.
this as been patched, but i guess not properlly.

You have a username field limited to 255 chars, but when you fill up this field , and press login button
it tells you "not loggued in".
If you click on the "forgot passwd" link, it will popup a little windows with your username supplied printed,
stack based overflow occurs here, Allowing code execution .


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3)Proof of concept

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When you boot the machine,you'll be firstly prompted for your Novell login.
If you fill up username with 254's B ==> click login ==> forgotten password ==> B.S.O.D

If the workstation is allready loggued in:
novell ==> login Novell ==> 254's A ==> click login ==> forgotten password ==> Result:

Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=41414141 ebx=00000111 ecx=00000001 edx=00000000 esi=00997980 edi=00997980
eip=73d22054 esp=00dff278 ebp=00dff200 iopl=0         nv up ei pl nz na pe nc
cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010206

MFC42!Ordinal5163+0x492:
73d22054 8908            mov     dword ptr [eax],ecx  ds:0023:41414141=????????




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5)Credits

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laurent gaffié
laurent.gaffie[at]gmail[dot]com