Title: Wireless Security Research with focus on PEAP/TTLS Design and Implementation
1Wireless Security Researchwith focus on
PEAP/TTLS Design and Implementation
- Based on Nirmala Bulusus Master Thesis
2Outline of the Talk
- Introduction
- WLAN, RADIUS, EAP, TLS,TTLS, PEAP
- Design and Implementation of PEAP Module for Free
RADIUS - Performance Comparison of PEAP and TTLS
- Conclusion and Future Work
3Introduction
- WLAN, RADIUS, EAP, TLS,
- TTLS and PEAP
4Why Wireless Networking
- Advantages
- No "plug ins"
- Increased Productivity
- Easier network expansion
- Flexibility and
- Lowers the cost of ownership
- Use unlicensed band
- Vulnerabilities
- Unauthorized user access
- Eavesdropping (network can be tapped using
sniffing tools)
5War Driving
A directional antenna fashioned from a Pringles
can is used to search for unsecured access points.
6Doonesbury
Parking Lot Attack
7Secure Tunnels
The Extensible Authentication Protocol (EAP) uses
encryption to create a tunnel for data
confidentiality.
8IEEE 802.1x - Architecture
- IEEE 802.1x is a port-based network access
control solution to authenticate every network
user accessing the LAN services. - It defines an encapsulation technique that allows
for the transmission of EAP packets between the
Supplicant and Authenticator in the LAN
environment.
9EAP- Tunneled Transport Layer Security (EAP- TTLS)
- TTLS is a two-stage protocol - establish security
in stage one, exchange authentication in stage
two. - The users identity and password-based
credentials are tunneled during authentication - Provides mutual authentication, key generation
, client identity privacy and data cipher suite
negotiation
10How PEAP WorksPEAP Phase 1 Establish TLS
Tunnel
- Client/Supplicant associates with AP - EAPOL
- Authentication Server is authenticated to the
Supplicant using PKI certificate. - Supplicant sends machine credentials to
authenticator over the established TLS channel - Authenticator checks Clients validity and if
valid, generates the WEP key - Authenticator delivers key to supplicant and
transitions controlled port status to permit
supplicant access to LAN
11How PEAP Works PEAP Phase 2 Authenticate
Client
- Client is requested user identity
- Supplicant responds by sending user credentials
to authenticator - Authenticator checks validity by looking up the
user database - If user id valid, authenticator extends
controlled port status to permit supplicant full
access to LAN - User is logged on to the domain and the network
is open
12The New Proposed ProtocolsEAP-TTLS and PEAP
- TTLS - developed by Funk and Certicom,
- Linux, Mac OS X, Windows 95/98/ME, and Windows
NT/2000/XP. - Can use any Authentication Method - CHAP, PAP,
MS-CHAP, MS-CHAPv2 and EAP
- PEAP developed by Microsoft, Cisco.
- Windows XP is currently the only operating system
that supports PEAP. - Only EAP - generic token card
Research Goal Design, Implement and perform a
comparative analysis of the two
protocols.
13What is PEAP ?
- IETF Draft-standard proposed by RSA, Microsoft,
Cisco - draft-josefsson-pppext-eap-tls-eap-02.txt.
- PEAP is an 802.1x Authentication protocol
typically designed for enhancing access control
in wireless LANs (WLANs) - It is built on top of two well known protocols
- Extensible Authentication Protocol (EAP)
- Transport Layer Security (TLS)
14IEEE 802.1x How it Works
- 802.1x is a port-based network access control
method to authenticate and authorize users
accessing Local Area Network (LAN) services.
The three elements in IEEE 802.1x
Supplicant
Authenticator
System
System
Host NIC
Services offered by
Authenticator
Ethernet 802.1,
the Authenticator
PAE
(Port Access Entity)
Wireless PC card,
system
EAP Messages
EAPOL
etc.
Encapsulated
Controlled
Port Unauthorized
Port
Authorize/Unauthorize
The th
ree d
ifferent
Uncontrolled
Port
e
lements in
IEEE
802.1x
MAC Enable
15802.1x Communication protocols
- Protocols to transmit data between Supplicant and
the Access Point - EAP-over-LAN (EAPoL) encapsulated EAP messages in
Ethernet frames - EAP over RADIUS (Remote Access Dial-in User
Service) encapsulates EAP messages in RADIUS
packets
16Remote Access Dial-in User Service (RADIUS)
- RADIUS is a Client/server protocol and software
that supports authentication, authorization, and
accounting (AAA) for dial-up, virtual private
network, and wireless network access. - Three major components of RADIUS
- End User (Supplicant)
- RADIUS Client (Access Point, Authenticator or
Terminal Server) - RADIUS server (Authentication server).
- All RADIUS messages are sent as User Datagram
Protocol (UDP) messages on port 1812.
17Message Exchanges Between RADIUS Client and
Server
For PEAP, Password is not sent in this frame
18802.1X Authentication Types
- EAP-TLS (EAP-Transport Layer Security)
- Mutual authentication via PKI based client
server certificates - Supported in XP and soon other Windows versions
- Imposes substantial administrative burden to
generate, distribute and manage user
certificates. - EAP-TTLS (EAP-Tunneled Transport Layer Security)
- User authentication via user ID and password
- Supported by Funk Softwares Odyssey
- Supports both EAP and non-EAP kind of
Authentication methods. - PEAP (Protected EAP)
- User authentication via user ID and password
- Supported by Cisco Aironet client adapters and
Microsoft XP SP1 - Supports only EAP authentication methods.
19EAPTransport Layer Security
- EAP-TLS (RFC2716) defines a mechanism for
exchange of messages with both client and server
validating each other via certificates providing
mutual authentication - Certificate management required for secure
operation
No user-password kind of exchanges
20Need for PEAP/TTLS
- Wireless AP broadcasts all traffic hence can
easily collect data if within the broadcast range
- PEAP/TTLS answers this by transmitting
user-sensitive data in an encrypted channel - the
established TLS tunnel - Weak Wireless Encryption
- Using PEAP/TTLS the data within the tunnel cannot
be decrypted without the TLS master secret and
the key is not shared with the Access point.
Rogue/compromised access points cannot decrypt
messages. - MAC address based access control does not work
NetStumbler - Use TLS-based authentication mechanisms to tunnel
user credentials. - EAP-TLS administrative overhead
- With PEAP/TTLS only server side PKI
infrastructure based digital certificates are
used to authenticate EAP servers. No need to
install and maintain Client side certificates.
21EAP-Tunneled Transport Layer Security (EAP-TTLS)
- Is a two-phase protocol - establish security in
stage one, exchange authentication in phase two. - The users identity and password-based
credentials are tunneled during authentication - The AAA server can proxy the user authentication
to AAA/H (e.g., LDAP, Active Directory) server.
TTLS Architectural Model
22Protected EAP (PEAP)
- Two Phase Protocol Establish TLS connection,
start a second EAP authentication process inside
encrypted tunnel. - Client is authenticated in the second phase using
any EAP authentication mechanism (Generic Token
Card, One-Time-Password, MS-CHAPv2) - MS-CHAPv2 Microsoft Challenge-Handshake
Authentication Protocol - PEAP addresses the weaknesses of EAP by
protecting user-credentials, standardizes key
exchanges, supports fragmentation, fast
reconnects and seamless transition. - Fast reconnection Do quick re-authentication by
passing only session keys. The session can be
resumed without having to perform PEAP Phase 1 or
2. - Seamless transition uses the connection
re-establishment mechanism provided by the TLS
handshake protocol.
23Phase 1- Establish TLS Tunnel
AP only pass-through device from this point
(User-name)
/Start
Exchange Series of TLS messages
User Validates server certificate
RADIUS server sends Certificate chain to Client
24Phase 2- Authenticate Client
Challenge String
Response to challenge string user password
EAP- Success message
Session key, encrypted WEP key
25PEAP Protocol Implementation Details
26FreeRADIUS Server Code Organization
- Handles requests through a module interface
Radius Load Module RLM - Module has four components that act on RADIUS
requests at different stages of processing the
request - Authorization Process of obtaining information
about the user from external source determining
the type of authentication protocol to be used. - Authentication Process of validating a Users
Identity. - Pre-AccountingDecides whether to proxy the
request - Accounting This records the request in the
RADIUS log - A module declares which components it supports by
putting function pointers in its "module_t rlm_
structure.
27Free RADIUS Code Directory Structure
The new developed Software
28Module Behavior
- Add module inside the modules block of the
radiusd.conf file. module_name defined in the
block is used to load the module. - Each configured module calls its own init()
method. - The instantiate() method is called next. It is
given a handle to the configuration block holding
the parameters. - Finally a detach() method is called when server
is shut- down to release the allocated resources.
29Example - radiusd.conf
modules eap default_eap_type
peap tls peap
default_eap_type mschapv2
eap sets the authorize type as
EAP authorize eap eap authentication
takes place. authenticate eap
30The rlm_eap_peap module
- Deals with the standard attach, detach, and
authenticate interfaces. - The rlm_eap_peap module does not have an
initiate() interface. - PEAP is a protocol on top of TLS, so before
initiating PEAP we have to initialize the TLS
session.
/ rlm_eap_peap.c - Contains interfaces called
from the main module EAP / EAP_TYPE
rlm_eap_peap "eap_peap", / module_name
/ eappeap_attach, / attach / NULL, / No
peap initialization interface/ NULL, / No
need for authorization interface/ eappeap_authen
ticate, / authentication / eappeap_detach /
detach /
31PEAP Phase 1- Implementation
- Handler is sent to the eaptls_process function
which processes the EAP request returns the
status code. - If the status code returned is a Success then the
PEAP module proceeds to decode the tunneled
attributes - If the status code returned is a Fail then the
PEAP module interprets it as a failure in
establishing the TLS session and returns back to
the eaptls_process method for ending the session.
32The EAP-TLV Method
- EAP-TLV is a payload with standard
Type-Length-Value (TLV) objects. - Used to carry arbitrary parameters between the
EAP peer and the EAP server. - The PEAP tunnel success/failure packet contains a
Result TLV. - The Result TLV packet is used to indicate success
or failure of the PEAP tunnel. - They are sent in the TLS channel - Phase 2.
- Packets are protected from being spoofed by an
attacker.
33EAP TLV Packet Formats
34Implementation EAP-TLV
- User credentials, the state of the message
exchange and the Status i.e the Result TLV has to
be passed through the encrypted channel. - A data structure to store these parameters is
defined - Two functions for explicitly framing the result
TLV packets have been implemented
/ eap_peap.h - PEAP header file/ define
TLV_SUCCESS 1 define TLV_FAILURE 2 define
PW_EAP_TLV 33 typedef struct peap_tunnel_t
VALUE_PAIR username VALUE_PAIR state int
status / Checks for Result TLV status /
peap_tunnel_t static int eappeap_success(EAP_HAND
LER handler, tls_session_t tls_session) static
int eappeap_failure(EAP_HANDLER handler,
tls_session_t tls_session)
35PEAP Phase 2- Implementation
- Starts with the eappeap_authenticate () interface
receiving the EAP_TLSOK status code from the
eaptls_process function - The function proceeds to read and decrypt the
tunneled data from the SSL session using the in
built SSL functions . - Next it allocates a new request data structure
and adds the tunneled attributes to the request.
- It then calls the rad_authenticate () function
with the new request packet as the parameter to
handle the tunneled EAP-Type MS-CHAPv2.
36PEAP Phase 2- Implementation
- Next it reads the Response Packet received from
the rad_authenticate function. - IF the status field TLV_SUCCESS, then Phase two
of the protocol has been successful and the
server can proceed to generate the MPPE
(Microsoft Pointto-Point Encryption) keys
according to the RFC 2716 EAP-TLS. - Any response messages in the VALUEPAIR format
need to be converted to the tunneled data format.
37Performance Analysis of PEAP and TTLS
38TEST BED at UCCS ENG LAB
RADIUS
Client
39Client/Server Machine Configurations
40Performance Impact of Clients Processor Speed
on PEAP TTLS
- Purpose
- Investigate the impact of Clients processor
speed on the time taken to process the Client
requests and to see the capacity of the server to
handle multiple requests coming from the Clients. - Number of Tests Performed
- Three Tests performed - Toshiba machine
366Mhz, Hobbit machine 996 Mhz and with two
clients having simultaneous access to the server.
41PEAP vs TTLS on Toshiba machine
PEAP TTLS Average 1046 949 Variance 8142 12060
42PEAP vs TTLS on Hobbit machine
PEAP TTLS Average 983 911 Variance 10 356
43PEAP vs TTLS Simultaneous Access of Clients
PEAP TTLS Average 1006 947 Variance 23707 12387
44Result Analysis
- TTLS out performing PEAP on an average by 8
- At lower processor speeds - TTLS was
outperforming PEAP by 10 - At higher processor speeds the performance
difference is around 7 - When running simultaneously with two clients it
shows a performance difference of only 6 - TTLS and PEAP both show low data variance.
- PEAP had almost negligible variance with a higher
processor speed Client. - Processor speeds influencing PEAP relatively more
as compared to TTLS
45Sensitivity study of PEAP TTLS with Client
stationed at varying distances
- Purpose
- To study the impact on the performance of the
two protocols by introducing packet loss or
signal degradation with increasing distances
between wireless Client and AP. - Number of Tests Performed
- Five Tests performed at distance ranges of
approximately 25, 30, 45, 55 and 65 feet. Some
tests were done behind walls and closed doors to
see the impact of line of sight.
46PEAP vs TTLS Distance Range 30ft
47PEAP vs TTLS Distance Range 25ft
48PEAP vs TTLS Distance Range 45ft
49PEAP vs TTLS Distance Range 55ft
50PEAP vs TTLS Distance Range 65ft
51PEAP vs TTLS Average Performance
52PEAP vs TTLS Variance Data
53Result Analysis
- As Client goes farther away from the access point
the performance of both the protocols degrades. - At a lower distance range there is negligible
performance difference between PEAP and TTLS
TTLS performing 1 better. - With increasing distance range average
performance difference increases - TTLS performs
20 better at 65 feet range. - Data collected highly variant for PEAP as
compared to TTLS at closer distances but at the
farthest point of 65 feet TTLS data showed
higher variance than PEAP.
54PEAP TTLS Resilience Tests
- Purpose
- To study the tolerance capacity of the protocols
towards network transient behavior. - Number of Tests Performed
- Five Tests performed. The network interface at
the RADIUS server end is brought up and down over
different time periods by running a Perl script. - Note A constant downtime of 3 sec has been used
in all tests. - At first this was chosen randomly. But later by
changing downtime it seemed to be making less
difference to the performance as compared to
changing network uptime.
55PEAP vs TTLS Network Uptime 5.0 sec
PEAP TTLS Average 12 6 Variance 266 84
56PEAP vs TTLS Network Uptime 4.5 sec
PEAP TTLS Average 9 8 Variance 105 95
57PEAP vs TTLS Network Uptime 4.2 sec
PEAP TTLS Average 12 12 Variance 106 118
58PEAP vs TTLS Network Uptime 4.0 sec
PEAP TTLS Average 18 16 Variance 50 91
59PEAP vs TTLS Network Uptime 3.9 sec
PEAP TTLS Average 25 26 Variance 437 390
60Result Analysis
- Client performance degrades as the network
interface uptime gets shorter. - At 3.8 sec uptime both PEAP and TTLS protocols
failed to recover. - The average performance of TTLS as compared to
PEAP is negligible - Where difference was large the variance
difference between the two also has been
relatively big.
61PEAP TTLS Stress Tests
- Purpose
- To study the performance of the two protocols
when run for a longer period of time. - Number of Tests Performed
- Two Tests performed One for Each Protocol.
Each test was run for over 15 hours
62Stress Test - PEAP
Average 1011
63Stress Test - TTLS
Average 1099
64Result Analysis
- Both protocols passed the stress tests. Both
authenticated the Client all times. -
- The peaks can be attributed to the fact that in
some of the cases the Client got authenticated in
the second or third trial of authentication - The peaks reached by TTLS are much more frequent
and higher as compared to PEAP - Over a longer
time period TTLS shows more variance than PEAP
65MAC Address Spoofing Test
- Purpose
- Investigate if by spoofing the MAC address an
attacker can gain access to a wireless network
that relies on tunneled encryption like PEAP/TTLS
for authenticating wireless Clients. - Number of Tests Performed
- One test was performed with a Linux Client
authenticating using PEAP. Attacker had Windows
XP running AiroPeek software for sniffing MAC
addresses. - I would like to thank Donovan Thorpe of Computer
Services UCCS for his help in performing this
test.
66Result Analysis
- The attacker could associate with the Access
Point as it had a valid MAC address while
eavesdropping the network. Thus passed the first
line of defense MAC address filtering. - The attacker was prompted for the user
credentials. This stage could not be by-passed
and the attacker could not access the network as
the user credentials were in encrypted format and
thus could not be sniffed.
67Conclusion Future Work
68Conclusion
- Developed a Radius Server on Linux that supports
both PEAP and TTLS. - PEAP is relatively more influenced by Clients
processor speeds, distance range and network
transient nature as compared to TTLS. - Although the higher performance shown by TTLS
over PEAP is negligible, it is worth noting that
TTLS was outperforming PEAP on an average by 10
in all the tests. - The enhanced Radius Server can serve both Windows
and Linux clients.
69Future Work
- Study how to apply the PEAP/TTLS protocols in
Mobile Ad-Hoc Networks. - Study the implications of providing Virtual
Private Network (VPN) features in addition to
encryption of PEAP/TTLS within the wireless
Access Point devices. - Develop ways to protect user's identity that is
passed in clear between the access point, the
RADIUS server, and any other database-backend
server by implementing firewalls or other such
viable security techniques.