BugTraq
Vulnerabilities in GenStat 14.1.0.5943 Oct 03 2011 03:15PM
Luigi Auriemma (aluigi autistici org)
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Luigi Auriemma

Application: GenStat
http://www.vsni.co.uk/software/genstat/
Versions: <= 14.1.0.5943
Platforms: Windows
Bugs: A] array overflow with write2
B] heap overflow
Exploitation: file
Date: 01 Oct 2011
Author: Luigi Auriemma
e-mail: aluigi (at) autistici (dot) org [email concealed]
web: aluigi.org

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1) Introduction
2) Bugs
3) The Code
4) Fix

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1) Introduction
===============

From vendor's homepage:
"all embracing data analysis tool, offering ease of use via our
comprehensive menu system reinforced with the flexibility of a
sophisticated programming language."
"For over 30 years we have employed, and continue to work with, leading
statisticians and scientists who help to create a package that succeeds
for both novice and expert users in academia, research and industry."

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2) Bugs
=======

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A] array overflow with write2
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Array overflow during the handling of the GWB (GenStat book) files with
possibility of placing a NULL word in an arbitrary memory location:

00630399 |> 8B46 24 MOV EAX,DWORD PTR DS:[ESI+24] ; EAX controlled
0063039C |. 8B4E 08 MOV ECX,DWORD PTR DS:[ESI+8]
0063039F |. 8D0481 LEA EAX,DWORD PTR DS:[ECX+EAX*4]
006303A2 |. 3938 CMP DWORD PTR DS:[EAX],EDI
006303A4 |. 74 12 JE SHORT GenStat.006303B8
006303A6 |. 8B00 MOV EAX,DWORD PTR DS:[EAX]
006303A8 |. 05 A4040000 ADD EAX,4A4
006303AD |. 0FB708 MOVZX ECX,WORD PTR DS:[EAX]
006303B0 |. 894D FC MOV DWORD PTR SS:[EBP-4],ECX
006303B3 |. 33C9 XOR ECX,ECX
006303B5 |. 66:8908 MOV WORD PTR DS:[EAX],CX ; write2

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B] heap overflow
----------------

Through the text strings in the final part of the GSH (GenStat
SpreadSheet) files it's possible to cause a heap overflow with
consequent freeing of arbitrary memory (write4):

0064D1C7 |> 3BBE 78040000 /CMP EDI,DWORD PTR DS:[ESI+478]
0064D1CD |. 7F 74 |JG SHORT GenStat.0064D243
0064D1CF |. FF75 08 |PUSH DWORD PTR SS:[EBP+8]
0064D1D2 |. 8D45 F4 |LEA EAX,DWORD PTR SS:[EBP-C]
0064D1D5 |. 6A 01 |PUSH 1
0064D1D7 |. 6A 04 |PUSH 4
0064D1D9 |. 50 |PUSH EAX
0064D1DA |. E8 2F3B2600 |CALL GenStat.008B0D0E ; read 32bit
0064D1DF |. 83C4 10 |ADD ESP,10
0064D1E2 |. 85C0 |TEST EAX,EAX
0064D1E4 |.^0F84 06FFFFFF |JE GenStat.0064D0F0
0064D1EA |. 66:837D 0C 00 |CMP WORD PTR SS:[EBP+C],0
0064D1EF |. 74 0A |JE SHORT GenStat.0064D1FB
0064D1F1 |. 8D45 F4 |LEA EAX,DWORD PTR SS:[EBP-C]
0064D1F4 |. 50 |PUSH EAX
0064D1F5 |. E8 DD6AFFFF |CALL GenStat.00643CD7
0064D1FA |. 59 |POP ECX
0064D1FB |> 837D F4 00 |CMP DWORD PTR SS:[EBP-C],0
0064D1FF |. 7E 1E |JLE SHORT GenStat.0064D21F ; I use the first one equal to -1
0064D201 |. FF75 08 |PUSH DWORD PTR SS:[EBP+8]
0064D204 |. 8B46 58 |MOV EAX,DWORD PTR DS:[ESI+58]
0064D207 |. 6A 01 |PUSH 1
0064D209 |. FF75 F4 |PUSH DWORD PTR SS:[EBP-C] ; 0x61616161
0064D20C |. 03C7 |ADD EAX,EDI
0064D20E |. 50 |PUSH EAX
0064D20F |. E8 FA3A2600 |CALL GenStat.008B0D0E ; overflow/corruption
0064D214 |. 83C4 10 |ADD ESP,10
0064D217 |. 85C0 |TEST EAX,EAX
0064D219 |.^0F84 D1FEFFFF |JE GenStat.0064D0F0
0064D21F |> FF86 74040000 |INC DWORD PTR DS:[ESI+474]
0064D225 |. 8B45 F4 |MOV EAX,DWORD PTR SS:[EBP-C]
0064D228 |. 43 |INC EBX
0064D229 |. 3B5D F8 |CMP EBX,DWORD PTR SS:[EBP-8]
0064D22C |. 8D7C07 01 |LEA EDI,DWORD PTR DS:[EDI+EAX+1] ; 0 + -1 + 1 = 0
0064D230 |.^7C 95 \JL SHORT GenStat.0064D1C7

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3) The Code
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http://aluigi.org/poc/genstat_1.zip

A] modified 32bit field at offset 0x46
B] modified 32bit field at offset 0x302 and added 'a's

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4) Fix
======

No fix.

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---
Luigi Auriemma
http://aluigi.org

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