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Created: Wednesday, October 12 2005 00:15.27 CDT

Modified: Wednesday, October 12 2005 17:29.12 CDT

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Julius 0.1a vs. KB900725 (winsrv.dll)

Author: rfreeman

# Views: 2473

Over the past two or so months, I've been working in my spare time to write a stand-alone patch analysis tool. Feedback is appreciated...

After taking today's security patch updates for my WinXP (SP2) box, I selected the KB900725 update for analysis as the link to more information (at the time) was broken and may have been trying to "fly under the radar". Four DLL's are included in this update: linkinfo.dll, shell32.dll, shlwapi.dll, and winsrv.dll. While I have produced results for all four libraries, I specifically looked at the results for winsrv.dll. Previously, I have used msgsvc.dll and schannel.dll as my primary QA tests during development.

The first interesting match, was highly suspect with a high deviation and lack of a named address. After quickly eyeballing both addresses in a disassembler, it was clear that the function boundary heuristics were to blame (thus a false positive). So this was quickly dismissed. Next I noticed 0x75b8afef, which supposedly was 0x75b8f2c1 (CheckEudcRangeInString). Since the address of the match seemed out of order, I checked and found that a true match for CheckEudcRangeInString existed later in the log file. Upon eyeballing, it became clear that 0x75b8afef was a new function that had been inappropriately matched. Curiously cross references for this function were found in GetLinkProperties. GetLinkProperties has the strongest list of security warnings, which I probably should have looked at first, but I don't think the order of investigation was inefficient in this example. Upon a look at GetLinkProperties, it became clear that 0x75b8afef was being used as a replacement for lstrcpyW(). Since there is an extra parameter and 0x75b8afef copies memory, I think it

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