[CORE SDI ADVISORY] MS Windows NT4 and Windows 2000 PhoneBook Service overflow

[Iván Arce <core.lists.bugtraq () CORE-SDI COM>]

                                              CORE SDI
                                 http://www.core-sdi.com

          Vulnerability Report For Microsoft PhoneBook Server overflow

Date Published: December 4th, 2000

Advisory ID: CORE-20001204

Bugtraq ID: 2048

CVE CAN: None currently assigned.

Title: Microsoft PhoneBook Server buffer overflow

Class: Boundary condition error

Remotely Exploitable: Yes

Locally Exploitable: Yes

Release Mode: COORDINATED RELEASE

Vulnerability Description:

 The Phone Book Service is an optional component that ships
 with the NT 4 Option Pack and Windows 2000.
 It is not installed by default.

 A buffer overflow vulnerability was discovered in the URL processing
 routines of the Phone Book Service requests on IIS 4 and IIS 5.
 If exploited, this vulnerability allows an attacker to execute arbitrary
 code and obtain a remote command shell with those privileges of the
 IUSR_machinename account (IIS 4) or the IWAM_machinename
 account (IIS 5).

Vulnerable Packages/Systems:
  Microsoft Windows NT 4.0
  Microsoft Windows NT 4.0 Enterprise Server Edition
  Microsoft Windows 2000 Server
  Microsoft Windows 2000 Advanced Server

Solution/Vendor Information/Workaround:

  Microsoft has released a fix that eliminates the vulnerability.
  It can be obtained from:

   Microsoft Windows NT 4.0:
    http://www.microsoft.com/Downloads/Release.asp?ReleaseID=26193

  Microsoft Windows 2000:
   http://www.microsoft.com/Downloads/Release.asp?ReleaseID=25531

  NOTE: The NT 4.0 fix can be applied to systems running NT 4.0 Service
  Pack 6a. This fix will be included in NT 4.0 Service Pack 7. The
  Windows 2000 fix can be applied to Windows 2000 Gold or Service Pack 1.
  This fix will be included in Windows 2000 Service Pack 2.

   Note Additional security patches are available at the Microsoft
  Download Center.

  More Information
   Frequently Asked Questions: Microsoft Security Bulletin MS00-094,
   http://www.microsoft.com/technet/security/bulletin/fq00-094.asp

   Microsoft Knowledge Base article Q276575 discusses this issue
   and will be available soon.

  Microsoft TechNet Security web site,
  http://www.microsoft.com/technet/security/default.asp

 Vendor notified on: September 27th, 2000

Credits:

  This vulnerability was discovered by Alberto Solino of CORE SDI,
  Buenos Aires, Argentina.

  Other CORE SDI advisories can be obtained from:
  http://www.core-sdi.com/publications.html

  It was also discovered and reported independently at the same time
  by David Litchfield from @Stake Inc.

  We would like to thank the Microsoft Security Response Team for their
  quick acknowledge to the report and the prompt response and efforts
  generating a fix.

  This advisory was drafted with the help of the SecurityFocus.com
  Vulnerability Help Team. For more information or assistance drafting
  advisories please mail vulnhelp () securityfocus com.

Technical Description - Exploit/Concept Code:

 The Phone Book server services requests using the Internet Information
  Services 5.0 with URIs such as http://hostname/pbserver/

 According to Microsoft's documentation a DLL (PBSERVER.DLL) is exported
 and  the services can be used making requests with the following format:


http://hostname/pbserver/pbserver.dll?osarch=&ostype=&osver=&cmver=&lcid=&pb
ver=&pb=<STRING=db name>

NOTE: The above URL might be wrapped

 In the DLL checks the total length to ensure that request does not exceed
1024 bytes, however it is possible to overflow a local variable of fixed
length
 in the DLL by sending a request with the following form:

 GET /pbserver/pbserver.dll?&&&&&&pb=AAAAAA... (less than 980 chars)
 HTTP/1.0\n\n

The result is an exception reported in the Event log with source WAM like
 the following:

 The HTTP server encountered an unhandled exception while processing the
 ISAPI Application '
 + 0x41414143
 + 0x41414139
 pbserver!HttpExtensionProc + 0x1C
 wam!DllGetClassObject + 0x808
 RPCRT4!NdrServerInitialize + 0x4DB
 RPCRT4!NdrStubCall2 + 0x586
 RPCRT4!CStdStubBuffer_Invoke + 0xC1
 ole32!StgGetIFillLockBytesOnFile + 0x116EC
 ole32!StgGetIFillLockBytesOnFile + 0x12415
 ole32!DcomChannelSetHResult + 0xDF0
 ole32!DcomChannelSetHResult + 0xD35
 ole32!StgGetIFillLockBytesOnFile + 0x122AD
 ole32!StgGetIFillLockBytesOnFile + 0x1210A
 ole32!StgGetIFillLockBytesOnFile + 0x11E22
 RPCRT4!NdrServerInitialize + 0x745
 RPCRT4!NdrServerInitialize + 0x652
 RPCRT4!NdrServerInitialize + 0x578
 RPCRT4!RpcSmDestroyClientContext + 0x9E
 RPCRT4!NdrConformantArrayFree + 0x8A5
 RPCRT4!NdrConformantArrayFree + 0x3FC
 RPCRT4!RpcBindingSetOption + 0x395
 RPCRT4!RpcBindingSetOption + 0x18E
 RPCRT4!RpcBindingSetOption + 0x4F8
 KERNEL32!CreateFileA + 0x11B
 '.
  For additional information specific to this message please visit the
  Microsoft Online Support site located at:
  http://www.microsoft.com/contentredirect.asp.

 By sending a carefully crafted HTTP request an attacker can bypass the
 total length check and overflow a local variable in PBSERVER.DLL allowing
 the execution of arbitrary code with the privileges of the IUSR_machinename
 account (IIS 4) or the IWAM_machinename account (IIS 5)  on the vulnerable
 systems.

Copyright notice

 The contents of this advisory are copyright (c) 2000 CORE SDI Inc. and may
 be distributed freely provided that no fee is charged for this distribution
 and proper credit is given.

$Id: PhonebookServer-advisory.txt,v 1.6 2000/12/05 00:56:47 iarce Exp $
---

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 a house from a horse by the roof on the house,
 Its nature and laws have been exhaustively expounded by Locke,
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Iván Arce
Presidente
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email   : iarce () core-sdi com
http://www.core-sdi.com
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C1005AAG Buenos Aires, Argentina.
Tel/Fax : +(54-11) 4331-5402
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