Flag: Tornado! Hurricane!

Blogs >> pedram's Blog

Created: Tuesday, July 11 2006 17:26.59 CDT  
Printer Friendly ...
Microsoft Ring0 Vulnerability++
Author: pedram # Views: 5737

Just publicly released an advisory affecting the Microsoft Windows kernel: Microsoft SRV.SYS Mailslot Ring0 Memory Corruption Vulnerability. I worked with H D Moore (who you most recently heard of from his Browser Fun blog) in discovering this bug. This is a great example of the benefits of having a custom SMB stack, many thanks to HD for sacrificing his Sunday afternoon with me on this.

The kernel memory corruption is obviously interesting as it allows for ring0 code execution. However, I find the following actual attack vector to be more interesting. According to the Microsoft Developer Network (MSDN) documentation, Mailslot communications are divided into two classes. First-class Mailslots are connection oriented and operate over SMB/TCP. Second-class Mailslots provide connectionless messaging for broadcast messages and operate over SMB/UDP. Second-class Mailslots are limited to 424 bytes per message. First-class Mailslots are officially unsupported in the Windows 2000, XP and 2003 operating systems. This is the key point as it means that any code relying on the implicit message size limitation could be exposing a vulnerability. So add mailslots to your list of interfaces to enumerate and examine when auditing a target. Look for calls to the CreateMailSlot API, example:

    push 0          ; lpSecurityAttributes
    push 0          ; lReadTimeout
    push 0          ; nMaxMessageSize
    push slot_name  ; "\\\\.\\mailslot\\mailslot_name"
    call CreateMailslotA

The nMaxMessageSize argument is key as it specifies the maximum size of a single message that can be written to the Mailslot in bytes, a value of zero allows for any arbitrary size (this is what you want). So the big question is, what else is exposed? I know of at least one 3rd party application, details of which will be released when a patch is available. A combination of Googling and examinaton of a number of targets tells me that Mailslot usage is pretty rare (fortunate or unfortunate depending on your point of view), but I'm curious to see what the masses discover.


Blog Comments
airhello Posted: Wednesday, December 19 2007 20:27.28 CST
can u tell me something about the first-class mailslot attack??
my email is [email protected]

thank u very much!



Add New Comment
Comment:









There are 31,320 total registered users.


Recently Created Topics
[help] Unpacking VMP...
Mar/12
Reverse Engineering ...
Jul/06
hi!
Jul/01
let 'IDAPython' impo...
Sep/24
set 'IDAPython' as t...
Sep/24
GuessType return une...
Sep/20
About retrieving the...
Sep/07
How to find specific...
Aug/15
How to get data depe...
Jul/07
Identify RVA data in...
May/06


Recent Forum Posts
Finding the procedur...
rolEYder
Question about debbu...
rolEYder
Identify RVA data in...
sohlow
let 'IDAPython' impo...
sohlow
How to find specific...
hackgreti
Problem with ollydbg
sh3dow
How can I write olly...
sh3dow
New LoadMAP plugin v...
mefisto...
Intel pin in loaded ...
djnemo
OOP_RE tool available?
Bl4ckm4n


Recent Blog Entries
halsten
Mar/14
Breaking IonCUBE VM

oleavr
Oct/24
Anatomy of a code tracer

hasherezade
Sep/24
IAT Patcher - new tool for ...

oleavr
Aug/27
CryptoShark: code tracer ba...

oleavr
Jun/25
Build a debugger in 5 minutes

More ...


Recent Blog Comments
nieo on:
Mar/22
IAT Patcher - new tool for ...

djnemo on:
Nov/17
Kernel debugger vs user mod...

acel on:
Nov/14
Kernel debugger vs user mod...

pedram on:
Dec/21
frida.github.io: scriptable...

capadleman on:
Jun/19
Using NtCreateThreadEx for ...

More ...


Imagery
SoySauce Blueprint
Jun 6, 2008

[+] expand

View Gallery (11) / Submit