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Workstation Service NetpManageIPCConnect Buffer Overflow

Release Date:
November 14, 2006

Date Reported:
July 25, 2006

Severity:
High (Remote Code Execution)

Vendor:
Microsoft

Systems Affected:
Windows 2000 (Remote Code Execution)
Windows XP SP1 (Local Privilege Escalation)

Overview:
A flaw exists in a default Windows component called the "Workstation
Service" that when exploited allows for remote code execution in SYSTEM
context, allowing an attacker to take complete control of affected
systems.

Technical Details:
In the Workstation Service module called wkssvc.dll, the
NetpManageIPCConnect function has a call to "swprintf" with an unchecked
buffer. The input buffer is controllable by the remote attacker.

    .text:76781D67         mov     edi, [ebp+arg_0]
    ...
    .text:76781D90         lea     eax, [ebp+var_2CC]
    ...
    .text:76781DA0         push    edi
    .text:76781DA1         push    offset "%ws\\IPC$"
    .text:76781DA6         push    eax
    .text:76781DA7         call    ds:swprintf

This function is called by NetpJoinDomain, which is eventually called by
the NetrJoinDomain2 function, which is exposed through RPC.

The IDL for NetrJoinDomain2 looks like this:
long  _NetrJoinDomain2@28 (
        [in][unique][string] wchar_t * arg_1,
        [in][string] wchar_t * arg_2, 
        [in][unique][string] wchar_t * arg_3,
        [in][unique][string] wchar_t * arg_4,
        [in][unique] struct_C * arg_5,
        [in] long arg_6
);

arg_2 will contain string with format like <Domain name>+"\"+<Hostname>.

<Hostname> will be passed as NetpManageIPCConnect's first argument. The
variable is under the attacker's control and is passed to swprintf,
which causes a stack-based buffer overflow.

For this vulnerable code to be reached, we must provide a valid and live
<Domain name> as a part of the string. We can set up a fake domain
server anywhere reachable from the vulnerable machine on the Internet.

P.S. If you despise Birkenstocks, are not afraid of your Tequila, and
are well versed in reverse engineering, bug finding, or are looking to
learn, we are hiring both junior and senior security researchers. Send
your resume (blathering of college course work, degrees, and past
experience we don't care about) or more importantly a description of why
you would be a good researcher to skunkworks@eeye.com.

Credit:
Discovery: JeongWook Matt Oh
Additional Research: Derek Soeder

Related Links:
Retina Network Security Scanner - Free Trial
Blink Endpoint Vulnerability Prevention - Free Trial

Greetings:
Dugsong, Ohhara, Ryan Lee, Pilot, Sakai, Gonan and all the Korean
Bugtruck Mailing List Subscribers

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