Transcript IV - CCCure.org

WIRELESS LAN SECURITY
Clément Dupuis,CD
CISSP, GCFW, GCIA, CCSA (NG), CCSE (NG),ACE
Groupe CGI, Montreal, Canada / CCCure.Org
1
Overview of Presentation

Introduction

The Jargon

The 802.11 family of standards

Security

Defend yourself

Deployment

Counter Measures

Conclusion
25
2
Introduction

Roller Coaster Ride

What or Who to believe?

Most talk about technology

Most hyped technology (Reminds me of bluetooth)

Most controversial LAN technology right now

A challenge to secure

Different standards and access control methods

Does not respect the typical security defences

It is being deployed in large numbers right now

Now, lets take a look at some number…
25
3
Introduction - WLAN Penetration
40%
42%
37%
31%
19%
33%
16%
46%
34%
10%
9%
18%
1%
Total (n=180)
23%
19%
500-999 PC's
(n=31)
2%
1,000-4,999
PC's (n=105)
9%
11%
5,000+ PC's
(n=44)
Wireless access today
Will add w/in 18 mos.
Will add in 19+ mos.
No plans to add
25
Don't know
Statistics provided by WECA
4
Introduction - WLAN Depth of Penetration
1%
2%
5%
Access to mo
employees
40%
70%
Access to som
workgroups/
Access to few
57%
23%
1%
Adopters
Access to all
employees
Don't know
Intenders
Access to all employees
Access to most employees
Access to some workgroups/
divisions
Access to few
25
Don't know
Statistics provided by WECA
5
Introduction - WLAN Top Drivers
38%
Allows mobility
No cabling/ wires/ No
cabling cost
28%
To allow our people
access to e-mail/servers
when they are not in office
14%
To test/see how it works
10%
Ease of use/access
10%
Portability
Other
6%
17%
25
Statistics provided by WECA
6
Introduction - WLAN Top Barriers
50%
Authentication/Security Concerns
72%
3%
Budget
19%
16%
Resources for
Deployment and Support
34%
Allows mobility
38%
9%
32%
No cabling/ wires/ No
cabling cost
vide employees access
mail/servers when out
of office
13%
Speed
Adopters
Intenders
28%
9%
11%
25
14%
Statistics provided by WECA
7
Overview of Presentation

Introduction

The Jargon

The 802.11 family of standards

Security

The Threats

Defend yourself

Deployment

Counter Measures

Conclusion
25
8
The Jargon - WarXing
A new series of words have come into play as the world Wireless
LAN and methods of attacks have evolved.
They are derived from the term WarDialing that was used to
described someone attempting all phone number in series to find
modems or other devices.

WarDriving

WarFlying

WarBoating
Plug (noun)
a piece of favorable publicity or a
favorable mention usually incorporated
in general matter

WarCycling
- Merriam-Webster

WarWalking

WarChalking

25
WarPlugging (i:e Tell Joes Pizza and get 10% Off)
9
The Jargon - WarChalking
A marking method is only as good as the number of people that
knows it. There is a common standard being developed amongst
warchalkers to offer a common marking scheme.
Bumper Sticker
25
www.warchalking.org
10
The Jargon - Acronyms

IEEE
Institute of Electrical and Electronics Engineers

802.11
Specifications for Wireless Standards

Wi-Fi
Wireless Fidelity, often used in lieu of 802.11b

WECA
Wireless Ethernet Compatibility Alliance

WLAN
Wireless Local Area Network

AP
Access Point

FHSS
Frequency Hoping Spread Spectrum

DSS
Direct Sequence Spread Spectrum

OFDM
Orthogonal Frequency Division Multiplexing

WEP
Wired Equivalent Privacy

EAP
Extensible Authentication Protocol

CRC
Cyclic Redundancy Check

HotSpot
Area where wireless access is offered
25
11
The Jargon - Hotspots

Some airport are not offering HotSpots but there is also
businesses that have taken opportunities of this by
offering Internet Access while people grab lunch.
) ))
) ))
In Austin, Texax, 11 stores with HotSpots
25
12
Overview of Presentation

Introduction

The Jargon

The 802.11 family of standards

Security

Defend yourself

Deployment

Counter Measures

Conclusion
25
13
802.11 Standard and it’s annexes

802.11 represents Wireless LAN standards and annexes

The original standard was 802.11, which was a standard
which defined wireless LAN using Infrared

First annex was 802.11b

Second annex was 802.11a

Then a series of 802.11x followed

It is a “shared” medium

It makes use of CSMA-CA

802.11a and 802.11b are radio systems
25
14
802.11Whatever – What does it mean
802.11
MEDIUM
SPEED
(Mbps)
MODULATION
ACCEPTANCE
REMARK
Infrared
1 and 2
FHSS
DSSS
Low
Low speed
Line of sight
802.11b
Radio Wave
2.4 Ghz
1, 2, 5.5, 11
DSSS
Most widely used
802.11a
Radio Wave
5 Ghz
1, 2, 5,5, 11
OFDM
New, low number of
units shipped
Up to 54 Mbps
Incompatible with
802.11b
Shorter Range
8 Channels
802.11d
Internationalization
802.11e
Quality of service
802.11g
Radio Wave
2.4 Ghz
1, 2, 5,5, 11
Up to 54 Mbps
OFDM
Slow acceptance in
Europe, it interferes
with radar systems
in the 5 Ghz range
Compatible with
802.11b and 802.11a
networks
Less interference in the
5 Ghz range but shorter
range
Only 3 channels
802.11i
Security
25
802.1x
Authentication
Framework for 802 LAN
15
What is a WLAN
25
Picture from: www.smarthomeforum.com
16
Hardware – WLAN Hardware



WLAN Network Adaptor Chipsets

Cisco Aironet Based Series (Hermes Chipset)

Lucent Orinoco (Agere) Series

Prism II Chipset (Linksys, Compaq, Dlink)
Format

USB External Card

PCI Card

PCI Adaptor with PCMCIA Card

PCMCIA Card
Antennas


After all we are talking Radio Frequency and Signal here
25
Some have connector for external antenna and some don’t
17
What does it looks like in real life!
25
18
What does it looks like in real life!
25
Pictures from: www.hdcom.com
19
Overview of Presentation

Introduction

The Jargon

The 802.11 family of standards

Security

Defend yourself

Deployment

Counter Measures

Conclusion
25
20
Security – A few more terms
A few more terms:

Station
Describe any device on a wireless network,
either a client or an access point

Ad Hoc
Refers to a network between two clients

Access
Point
Used by client to communicate with other
clients, either wireless or wired clients. This
is also referred to as Infrastructure Networks

BSS
Basic Service Set – An access point with all
it’s clients that form a network

SSID
Service Set Identifier – The name given to a
BSS network, also called Network Name
25
21
Security - WEP

From ANSI/IEEE Std. 802.11:
“3.49 wired equivalent privacy (WEP):
The
optional
cryptographic
confidentiality
algorithm specified by IEEE 802.11 used to
provide data confidentiality that is subjectively
equivalent to the confidentiality of a wired local
area network (LAN) medium that does not
employ cryptographic techniques to enhance
privacy.”
25
22
Security – WEP Basic Security functions
Network name (SSID), used as a network password, or
key, or in some cases keys are derived from the SSID on
AP (Authentication)


Must have same SSID to communicate

Use the same SSID on all devices

Protect from devices without the SSID
Authentication (Access Control)


Encryption (Confidentiality)


Based on MAC Filtering
Through the use of WEP

40 Bits

128 bits
25
CRC checksum (Integrity)
23
Security – WEP Weaknesses



Key Management

Not define or included

Tend to provide long term or poor quality keys

Keys are manually keyed

Due to the manual labour involved, keys do not change often
Key Size

40 bits defined in standard

Most have deployed 128 bits, which in fact is 104 bits + 24 Bits IV
WEP IV Size is too small

Provides for 16,777,216 different cipher stream

IV are being reused
25

WEP does not specify how IV are chosen or how often they rotate
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
24
Security – WEP ICV Weaknesses

The Integrity Check Value (ICV) Algorithm

Based on CRC-32

Good for detecting errors in data transmission but not for hashes

MD5 or SHA1 would be a better choice

Message can be tampered and still produce same ICV

Allow M-I-M type of attacks, Simply capture an encrypted packet
stream, modify the destination address of each packet to be the
attacker's wired IP address, fix up the CRC-32, and retransmit the
packets over the air to the access point

Key size does not matter with ICV and IV based attack, the attacks
all take the same amount of effort regardless if it is 40 bits or 128 bits
25
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
25
Security – WEP usage of RC4

RC4 in it’s implementation in WEP has weak keys

Too much correlation between the key and the output

First three bytes of the key are taken from the IV

They are sent unencrypted in each packet

It is easy to exploit as it is a passive attack

All that is needed is to collect enough data to derive the key

About 100 megs of data is necessary

Once 100 megs is collected, encryption can be broken in seconds
25
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
26
Security – WEP Authentication



Two forms of authentication

Open System – No authentication

Shared Key Authentication
Shared key is in fact weaker

Knowledge of a shared key is demonstrated by encrypting a challenge

Challenge and Response can be monitored by attacker

From this, the attacker can derive the RC4 steam that was used

The attacker can then use this RC4 stream to reply to any challenge
that he receives in the future
Advantage of Shared Key


Reduce the ability of an attacker to launch a Dos Attack by sending
bogus packet encrypted with the wrong key on the network
25
Shared key should be turned off and 802.1x used instead
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
27
Security – 802.1x

Based on EAP – As per RFC 2284

Allow the use of Radius, Active Directory, SecurID, Certificates
25
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
28
Security – WEP – XOR Operations


XOR () operation

Given two bits, if exactly one of them is a one, the result is one.

Otherwise, it is zero.
Sample XOR () Operation


Value A:
Value B:
A  B:
1 1 0 0
0 1 1 0
1 0 1 0
XOR () has the properties such that:
If
A  B = C,
then
C  B = A,
and
CA=B
A special mention to Ted Ipsen for sharing
with the community his WEP research on
which the info on XOR operations is based
29
25
Security – WEP – XOR Operation

XOR as a symmetric cipher
Message:
10011011101

01101010110
Ciphertext:
11110001011

01101010110
Key:
Key:
Message:
10011011101
25
30
Security – WEP – Operation
The CRC-32 ICV
A 4 byte CRC-32 Integrity Check Value (ICV) is computed for the data
payload of the packet and appended to it.
Plaintext Message (M)
ICV [s(M)]
The UNIQUE seed
The shared secret “key” (k) is static, a 24-bit Initialization
Vector (IV) is concatenated with the key (k), to form a
“unique” seed.
IV
Shared Key (k)
25
31
Security – WEP – Operation

THE KEYSTREAM
This seed is input into the stream cipher RC4, which outputs a
“keystream” of arbitrary length.
IV
Keystream
Shared Key (k)
RC4
000100101011100010110100101011110101010111011…
25
32
Security – WEP – Operation
The plaintext data, and the appended CRC-32 value are
XORed against an equal number of bits from the
keystream to create ciphertext.
Plaintext Message (M)

ICV [s(M)]
00010010101110001011010010101111010101
Ciphertext (C)
25
33
Security – WEP – Operation
The IV is put into the WEP Header in PLAINTEXT, and the
encrypted packet sent to the receiver.
802.11 Hdr
IV
Ciphertext (C)
The receiver uses the IV in the Header along with the
shared key, k to reproduce the RC4 keystream.
802.11 Hdr IV
IV
Ciphertext (C)
Shared Key (k)
RC4
25
000100101011100010110100101011110101010111011…
34
Security – WEP – Operation
The ciphertext is XORed against the RC4 keystream, and
the plaintext recovered.
Ciphertext (C)

00010010101110001011010010101111010101
Plaintext Message (M)
ICV [s(M)]
25
35
Security – WEP – Operation
The CRC-32 Integrity Check Value (ICV) is computed to
verify the integrity of the data.
Plaintext Message (M)
ICV [ s(M)]
Match?
CRC-32
ICV [s’(M)]
25
36
Security – WEP CONFIDENTIALITY

Confidentiality is provided by the XOR operation

To be secure, the keystream must NEVER be reused.

In WEP you are guaranteed to reuse these inputs, and
thus, the keystream!

The shared secret key k, whether 40 or 104 bits long, is
essentially fixed.

Therefore, the only input into the RC4 stream that
changes is the 24 bit IV (2^24 = 16,777,216)

So, about every 16 million packets, you get an IV
“collision”.
This
doesn’t take very long on a moderately busy network.
25
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
37
Security – WEP CONFIDENTIALITY


SCENARIO 1

Send some known plaintext (like spam e-mail), and capture the
encrypted packet with the cleartext IV.

XOR the plaintext against the ciphertext and recover the keystream.
SCENARIO 2
Consider the authentication scheme from the standpoint of an attacker.

You sniff the WLAN and capture the Challenge Message from the
Access Point as it is sent in cleartext to the requesting station.
Challenge (M)

You then capture the encrypted reply that is sent back to the AP
IV
25
Ciphertext (C)
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
38
Security – WEP CONFIDENTIALITY

SCENARIO 2 (Continued)

Compute the CRC-32 ICV for the Challenge, and append it.

XOR the Challenge and ICV against the Ciphertext
CM=K

And get the keystream back !!!
Challenge (M)

ICV
Ciphertext (C)
25
00010010101110001010
Primer from: http://www.nwfusion.com/research/2002/0909wepprimer.html
39
Overview of Presentation

Introduction

The Jargon

The 802.11 family of standards

Security

Defend yourself

Deployment

Counter Measures

Conclusion
25
40
Defend Yourself – WLAN Assessment

Hacking yourself before someone else does

How to assess your WLAN


Home brew

Commercial products
How to hide amongst others in the crowd

If everyone is screaming loudly then who is screaming
what you wish to hear.

How to fool the bad guys

More ways to fool the bad guys
25
41
Defend Yourself – Home Brew

What is required

A card with a connector for an external antenna



Software

Lots of software available for assessment

No software does all of the functions

Not all software works with all cards

Not all cards works with all OS

Will need more than one piece of software, card, and OS
Laptops


Cisco Aironet 352, Agere Orinoco Gold, and the Compaq WL100
With proper OS and Card drivers
External Antenna for better gain
25
42
Defend Yourself – Home Brew toolkit

As easy as 1-2-3

Free User Friendly sniffing and cracking software

Detect rogue networks that you may not know about
+
165$ US
NetStumbler
Kismet
APSniff
Sniffer Pro Wireless
AiroPeek
WepCrack
AirSnort
+
25
43
Defend Yourself – WLAN Assessment
Some of the functionality found in WLAN sniffer, cracker,
protocol analyzer, and assessment software:
SSID
Identification
MAC of AP
WEP
Detection
IP address,
Protocols
decodes
Data Rates,
channels,
signals
Cards
Supported
Netstumbler
(GPS Support)
Y
Y
Y
N
Y
ORINOCO
PRISM II
dstumbler
Y
Y
Y
N
Y
ORINOCO
PRISM II
WEPcrack
(Crack
encryption)
Y
Y
Y
N
N
PRISMII
AirSnort
(Crack
encryption)
Y
Y
Y
N
N
CISCO
PRISM II
ORINOCO
Airopeek NX
(Supports
802.11a)
Y
Y
Y
Y
All 7 layers
Y
CISCO
ORINOCO
Sniffer Pro
Wireless
Y
Y
Y
Y
All 7 layers
Y
CISCO
25
ORINOCO
SPECTRUM
44
Defend Yourself – WLAN assessment
25
45
Defend Yourself – Commercial ToolKit
25
46
Defend Yourself – Commercial ToolKit
Verify Signal Strength and clients on AP
25
47
Defend Yourself - Warfare
In 1978 while deploying HF, VHF, and UHF radio stations
for DOD, I would have never guessed that my antenna
theory would come to use for WLAN one day.

Position of the AP

As far away as possible from the unfriendly zone

Move it toward the centre of coverage zone if possible

Diffusion, Diffraction, Reflexion

Shield between you and remote

Type of antenna

Use a shield if necessary to direct waves

Use a cone shape to direct waves upward
25
48
Defend Yourself – Fake AP Tool

Hide in the crowd

Generates thousand of fake AP

RedHat only

Prism2/2.5/3 based 802.11b cards

Currently in development

Very promising

Available at:
http://www.blackalchemy.to/Projects/fakeap/fake-ap.html
25
49
Defend Yourself – Locate the enemy

Electronic Warfare Techniques

Ekahau Positioning Engine (www.ekahau.com)

Find a device within 1 meter

Need three points at least for accuracy

Marketing potential as well

Show ads to people close to a store for example

Disallow access to people outside your area

Available now
25
50
Defend Yourself – HOWTO

Control who gains access to your network

Use defence in depth

Implement strong user based authentication vs device based

Implement data encryption and do not rely on WEP

Attempt to create a centralize management point


Dynamic session-based encryption keys


it is very costly to maintain manually separate user database or to distribute
keys to each devices.
Keys should be changed automatically at fixed intervals and on
reauthentications, making them more difficult for intruders to crack than
static WEP keys
Mutual authentication

So that a client isn't deceived by a "rogue" (unauthorized) access point
25
51
Defend Yourself – HOWTO
A.
Wireless LAN behind a firewall (treat as untrusted)
B.
Do not use the default SSID



Change it regularly

Disable SSID broadcast if your device supports it
C. Make use of WEP, it is better than nothing

Change the WEP key from the default

Attempt to use product that dynamically generates key
D. Ban rogue networks

E. Ensure a policy exists that restricts WLANs from
being established without formal approval.
25
52
Defend Yourself – HOWTO


F. Add personalized authentication

Using MAC address

(802.1x)-based control lists
G. Leverage existing RADIUS servers

Integrate wireless LANs into the existing RADIUS infrastructure to
more simply manage users. It not only enables wireless
authentication, but also ensures wireless users go through the same
authorization and accounting approvals as remote users.

H. Not all WLANs are created equal, many manufacturer
equipment does not include enhanced security features.

I. Consider using a VPN

Virtual Private Networks have been deployed over the Internet to
allow secure communications for years. The same can be deployed
in a wireless environment to add Layer 3 encryption to the wireless
(Layer 2) communication.
25
53
FUN STUFF – Expedient Antennas

WLAN Can also be fun to experiment with

Keep you Pringles cans for your expedient antennas
25
54
FUN STUFF – WarPumpkin

WLAN Hackers Can Adapt to seasonal changes

Open WLAN, SSID=GoAway, Speed=1.5Mbps
25
55
WAR DRIVING

Are network really as badly protected as it is claimed
25
56
Questions ?
For further info
Clément Dupuis
[email protected]
Downloadable version available at:
http://www.cccure.org/Documents/Wireless/OTS2002.zip
57
25
WLAN Online References

The ultimate guide to WarXing
http://www.kraix.com/downloads/TDGTW-WarXing.txt

Great article on Security News Portal on how to defend yourself:
http://www.securitynewsportal.com/cgi-bin/cgiscript/csNews/csNews.cgi?database=JanR%2edb&command=viewone&id=3
4&op=t

The Ethernet Wireless Compatibility alliance
http://www.wi-fi.org

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58
WLAN Assessment Software

Netstumbler
http://www.netstumbler.com

WEPcrack
http://wepcrack.sourceforge.net

AirSnort
http://airsnort.shmoo.com/

Kismet
http://www.kismetwireless.net/index.shtml

Aerosol
http://www.sec33.com/sniph/aerosol.php

APSniff
http://www.zdnet.com.au/downloads/pc/swinfo/0,2000036
746,7997854,00.htm

Wellenreiter
http://www.remote-exploit.org

Triangulation
http://www.ekahau.com/
25
59
Commercial WLAN Assessment Software

Distributed Wireless Security Auditor, IBM
http://www.research.ibm.com/resources/news/20020617_
dwsa.shtml

AirDefense Security Appliance
http://www.airdefense.net/

AirMagnet PDA
http://www.airmagnet.com/

Airopeek NX
http://www.wildpackets.com/products/airopeek_nx

NAI Sniffer Pro Wireless
http://www.nai.com/
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60
Other Fun tools and Projects

Fake AP
http://www.blackalchemy.to/Projects/fakeap/fake-ap.html
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Pringle Can Antenna Recipe
http://verma.sfsu.edu/users/wireless/pringles.php
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Milk Can Antenna Recipe
http://reseaucitoyen.be/?BoiteDeConserve1
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Map and Statistics of Toronto War Driving
http://www.nakedwireless.ca/winudcol.htm
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