Transcript Slide 1

Authentication
Prof. Bill Buchanan
[email protected]
C.63
X2759
[email protected]
http://www.dcs.napier.ac.uk/~bill
http://buchananweb.co.uk
Author: Bill Buchanan
Contact:
 Room:
Telephone:
 MSN Messenger:
 WWW:
Week
Date
Academic
Cisco
Lab/Tutorial
1
2 Oct
1: Radio Wave Fundamentals
2
9 Oct
2: Wireless Fundamentals
Intro to Wireless LANs
Lab 1/2: Access Point Tutorial 1
(T)
3
16 Oct
3: Wireless Infrastructure
IEEE 802.11 and NICs
Lab 3: Ad-hoc Networks
4
23 Oct
4: Encryption
Wireless Radio Technology
Lab 4: Infrastructure Networks
(L)
5
30 Oct
5: Authentication
Wireless Topologies
Lab 5: Remote Connections (L)
6
6 Nov
6: Antennas
Access Points
Lab 6: Encryption/Authen (L)
7
13 Nov
7: Filtering
Bridges
Lab 7: Filter (L)
8
20 Nov
8: GSM/3G
Antennas
Lab 8: Filter (L)
9
27 Nov
Security
Lab 9: VLAN (L)
10
4 Dec
9: Future Technologies
Applications
Lab 10: RADIUS/Tacacs+ (L)
11
11 Dec
10: Site Surveys/ Troubleshooting
Site Survey
Lab 11: Integrative Lab (L)
12
18 Dec
11: Location-finding
Troubleshooting
Lab 12: Integrative Lab (L)
Holidays
13
9 Jan
Revision/Cram (Cisco Exam)
Emerging Technologies
14
16 Jan
Revision (Napier Exam)
Revision/Cram
15
23 Jan
Napier Exam (40%)
Cisco Exam (10%)
Coursework/Practical (50%)
Author: Bill Buchanan
Draft Schedule
Wireless connections … which technology?
Areas covered:
Author: Bill Buchanan
Authentication methods
Ways?
LEAP, PEAP, EAP, and so on
Methods and weaknesses.
Configurating authentication on an Aironet
A simple example with local Radius
Author: Bill Buchanan
Ways to Authenticate
Authentication methods
Users
Systems
Author: Bill Buchanan
Devices
Authentication methods
Users
Devices
Systems
Author: Bill Buchanan
Network/physical addresses. These are simple method of
verifying a device. The network address, such as the IP
address can be easily spoofed, but the physical address is
less easy and is a more secure implementation. Unfortunately
the physical address can also be spoofed, either through
software modifications of the wireless data frame, or by
reprogramming the network interface card. Methods include
DHCP.
Username and password. The use is usernames and
passwords are well known but are open to security breaches,
especially from dictionary attacks on passwords, and from
social engineering attacks. Methods include PEAP, EAP-FAST
and EAP-SRP.
Authentication methods
Pre-shared keys. This uses a pre-defined secret key.
Methods include EAP-Archie.
Users
Devices
Systems
Author: Bill Buchanan
Biometrics. This is a better method than a smart card
where a physical feature of the user is scanned. The
scanned parameter requires to be unchanging, such as
fingerprints or retina images.
Authentication methods
Authentication certificate. This certificate verifies a user or
a device by providing a digital certificate which can be
verified by a reputable source. Methods include EAP-TLS.
Users
Devices
Systems
Author: Bill Buchanan
Tokens/Smart cards. With this method a user can only gain
access to the system after they have inserted their personal
smart card into the computer and then entered their PIN
code. Methods include RSA SecurID Token Card and
Smartcard EAP.
Author: Bill Buchanan
IEEE 802.11 Frame Format
Transmitted frame
Preamble
PLCP
MAC Data Frame
Author: Bill Buchanan
10101010 ... 10101 1010 0000 1100 1011 1101
IEEE 802.11 data frame
2
Frame
control
Duration/
ID
6
Add 1
(Dest.)
6
Add 2
(Src)
6
Add 3
(SSID)
2
Sequence
control
xx xx xxxx
Subtype
Management:
0000 – Association Request
0001 – Association Response
0100 – Probe request (0x4)
1011 – Authentication (0xB)
Control:
1011 – RTS
1100 – CTS
1101 - ACK
Frame type
00 Management Frame (0x0)
01 Control
10 Data
Protocol version
00 (0x0)
6
0-2312
Frame
body
Add 4
4
FCS
xx x x xx xx
Order
0 Not ordered
WEP
0 – No WEP
1 - WEP
MoreData
0 No more data
ToDS
PowerManagement
FromDS
Retry
MoreFrag
Author: Bill Buchanan
2 Bytes
IEEE 802.11 data frame
2
Frame
control
Duration/
ID
6
Add 1
(Dest.)
6
Add 2
(Src)
6
Add 3
(SSID)
2
Sequence
control
xx xx xxxx
Subtype
Management:
0000 – Association Request
0001 – Association Response
0100 – Probe request (0x4)
1011 – Authentication (0xB)
Control:
1011 – RTS
1100 – CTS
1101 - ACK
Frame type
00 Management Frame (0x0)
01 Control
10 Data
Protocol version
00 (0x0)
6
0-2312
Frame
body
Add 4
4
FCS
xx x x xx xx
Order
0 Not ordered
WEP
0 – No WEP
1 - WEP
MoreData
0 No more data
ToDS
PowerManagement
FromDS
Retry
MoreFrag
Author: Bill Buchanan
2 Bytes
Frame Duration/ Address Address Address Sequence Address
control
ID
1
2
3
control
4
Frame
body
FCS
2 Bytes
0-2312
4
2
6
6
6
2
6
Frame control. This contains control information.
Duration/ID. This contains information on how long the data frame will
last.
Address fields. This contains different types of address, such as an
individual address of group addresses. The two main types of group
addresses are broadcast and multicast.
Sequence control. This identifies the sequence number of the data
frames, and allows the recipient to check for missing or duplicate data
frames.
Frame body. This part contains the actual data. The maximum
amount is 2312 bytes, but most implementations use up to 1500
bytes.
FCS (Frame Check Sequence). This is a strong error detection code.
Author: Bill Buchanan
IEEE 802.11 data frame
Frame
body
FCS
2 Bytes
0-2312
4
2
6
6
6
2
6
Author: Bill Buchanan
Frame Duration/ Address Address Address Sequence Address
control
ID
1
2
3
control
4
Author: Bill Buchanan
Wireless Authentication
Author: Bill Buchanan
WEP
also allows for
authentication
using a secret key
(shared key) or an
open system.
Author: Bill Buchanan
WEP
also allows for
authentication
using a secret key
(shared key) or an
open system.
Probe request
Probe response
Authentication
request
Association
request
Association
response
Wireless
Access
Point
Author: Bill Buchanan
Authentication
response
Open authentication
Probe request
Probe response
Authentication
request
Device is
always allowed
access to the
network
Association
request
Association
response
Wireless
Access
Point
Author: Bill Buchanan
Authentication
response
Open authentication (based on WEP)
Probe request
Probe response
Authentication
response
WEP data
frame
Wireless
Access
Point
Shared WEP
key is used
to authenticate the
client
Key: ABCDEF
Author: Bill Buchanan
Key: ABCDEF
Authentication
request
Shared-key authentication
Probe request
Probe response
Authentication
response (Challenge)
Authentication
request (Encrypted
challenge)
Authentication
response (success)
Wireless
Access
Point
Key: ABCDEF
Author: Bill Buchanan
Key: ABCDEF
Authentication
request
Weakness of shared-key authentication
Plain-text challenge (ABCDE)
“ABCDE”
WEP
Encrypted challenge
(“#@D.F”)
“#@D.F”
RC4
Random key
+
“ABCDE”
“#@D.F”
Author: Bill Buchanan
The man-in-the-middle
EX-OR’s the two sniffed
strings, and determines
the random key
MAC address-based authentication
Probe request
MAC address
is sent to RADIUS
server
RADIUSaccept
RADIUS
server
Author: Bill Buchanan
Authentication
response (success)
Wireless
Access
Point
MAC address-based authentication (weakness)
Probe request
MAC address
is sent to RADIUS
server
Authentication
response (success)
Wireless
Access
Point
RADIUSaccept
RADIUS
server
Author: Bill Buchanan
Spoofed MAC
address
Author: Bill Buchanan
Enhanced Security
802.1x Framework
HTTP
SMTP
TCP
SNMP
TELNET
FTP
SPX
UDP
NetBIOS
IP
EAP-TLS
PEAP
other methods
802.1X
layer
802.1x
802.3
(Ethernet)
802.5
(T.Ring)
802.11
(Wireless)
Method
layer
PPP
(Serial)
Link
layer
Author: Bill Buchanan
LEAP
IPX
802.1X framework
Start
Request ID
ID
ID
RADIUS server authenticates the client
Client authenticates the RADIUS server
Key length
RADIUS
server
Author: Bill Buchanan
Broadcast key
Author: Bill Buchanan
EAP
EAP - Efficient Application Protocols
EAP provides centralized authentication and dynamic key distribution.
It has been developed by the IEEE 802.11i Task Group as an end-toend framework and uses 802.1X and EAP.
This is:
Authentication. This is of both the client and the authentication
server (such as a RADIUS server).
Encryption keys. These are dynamically created after authentication.
They are not common to the whole network.
Centralized policy control. A session time-out generates a
reauthentication and the generation of new encryption keys.
Author: Bill Buchanan
A wireless client cannot gain access to the network, unless it has been
authenticated by the access point or a RADIUS server, and has
encryption keys.
There are many versions of EAP, including:
LEAP - Lightweight EAP
EAP-TLS - EAP-Transport Layer Security
PEAP - Protected EAP
EAP-TTLS - EAP-Tunnelled TLS
EAP-SIM - EAP-Subscriber Identity Module
Author: Bill Buchanan
•
•
•
•
•
EAPs
Device cannot
access network
until it has been
authenticated and
has encryption keys
Corporate
network
EAPs can either be in the
access point or
from a RADIUS server
RADIUS
server
Author: Bill Buchanan
Local RADIUS
server
EAPs
1. Client associates with the access point.
2. Client provides authentication details.
3. RADIUS server authenticates the user.
4. User authenticates the RADIUS server.
5. Client and RADIUS server derive unicast WEP key.
6. RADIUS server gives broadcast WEP key to access point.
7. Access point sends broadcast WEP key to client using unicast WEP key.
Corporate
network
EAPs can either be in the
access point or
from a RADIUS server
RADIUS
server
Author: Bill Buchanan
Local RADIUS
server
EAPs
Client details:
User ID and password.
Or
User ID and digital certificate
Or
Corporate
network
Local RADIUS
server
EAPs can either be in the
access point or
from a RADIUS server
RADIUS
server
Author: Bill Buchanan
On-time passwords
EAP-TLS
User Authentication:
Key size:
Encryption:
Device Authentication:
Open Standard:
User differentiation:
Certificate:
User ID and digital certificate
128 bits
RC4
Certificate
Yes
Group
RADIUS server/WLAN client
Corporate
network
EAPs can either be in the
access point or
from a RADIUS server
RADIUS
server
Author: Bill Buchanan
Local RADIUS
server
LEAPs
User Authentication:
Key size:
Encryption:
Device Authentication:
Open Standard:
User differentiation:
Certificate:
User ID and password
128 bits
RC4
Not Supported
No (Cisco-derived)
Group
None
LEAPs is open to
attack from a dictionary attack.
Use strong passwords!!!
Corporate
network
EAPs can either be in the
access point or
from a RADIUS server
RADIUS
server
Author: Bill Buchanan
Local RADIUS
server
LEAP
LEAPs uses MS-CHAP (Microsoft Handshake Authentication Protocol) to
continually challenge the device for its ID. It uses a challenge-response,
mutual authentication protocol using Message Digest 4 (MD4) and Data
Encryption Standard (DES) algorithms to encrypt responses. The
authenticating device challenges the client and vice-versa. If either
challenge is incorrect, the connection is rejected. The password is
converted into password hash using MD4. It is thus not possible for an
intruder to listen to the password.
The hashed password is then converted into a Windows NT key, which has
the advantage of being compatible with Microsoft Windows systems.
Normally authentication is achieved using the Microsoft login screen,
where the user name and the Windows NT key are passed from the client
to the access point.
Author: Bill Buchanan
LEAPs is open to attack from a dictionary attack, thus strong passwords
should be used. There are also many programs which can search for
passwords and determine their hash function.
EAP - PEAPs
User Authentication:
Key size:
Encryption:
Device Authentication:
Open Standard:
User differentiation:
Certificate:
User ID and password or OTP (one-time password)
128 bits
RC4
Not supported
Yes
Group
Yes
Corporate
network
EAPs can either be in the
access point or
from a RADIUS server
RADIUS
server
Author: Bill Buchanan
Local RADIUS
server
Author: Bill Buchanan
PEAPs
Public key
Some
data
Encrypted
authentication
“fred”
Encrypted
data
Sender
Receiver
Author: Bill Buchanan
Private
key
Private key
Digital
certificate
Encrypted
authentication
“fred”
Public key
is used to
decrypt
authentication
Author: Bill Buchanan
Encrypted
data
Some
data
Along with EAPs, the new enhancements for WLAN are:
TKIP (Temporal Key Integrity Protocol) which are enhancements to
RC4-based WEP. The IV has been increased to 48 bits (rather that 24
bits), and the Integrety Checker has been improved.
AES, which is a stronger alternative to RC4.
IEEE 802.11x
(Authentication of
both client and
access point)
WPA
(Wi-fi
Protected
Access)
Author: Bill Buchanan
IEEE 802.11i
Cisco Aironet 1200
192.168.1.240/24
192.168.1.112/24
192.168.1.111/24
Author: Bill Buchanan
Wireless
node
192.168.1.115/24
Author: Bill Buchanan
Configuration –
Local RADIUS server
Cisco Aironet 1200
192.168.1.240/24
(config) # dot11 ssid NapierSSID
(config-ssid) # authentication network-eap eap_methods
(config-ssid) # exit
Author: Bill Buchanan
Wireless
192.168.1.112/24
192.168.1.111/24
(config) # interface Dot11Radio0
node
(config-if) # encryption key 1 size 40bit AAAAAAAAAA transmit-key
192.168.1.115/24
(config-if)
# encryption mode ciphers wep40
(config-if) # no ssid tsunami
(config-if) # ssid NapierSSID
(config-if) # channel 1
(config-if) # guest-mode
(config-if) # station-role root
(config-if) # exit
(config) # interface BVI1
(config-if) # ip address 192.168.1.240 255.255.255.0
(config-if) # exit
(config) # ip http server
Cisco Aironet 1200
192.168.1.240/24
Author: Bill Buchanan
hostname ap
aaa new-model
aaa group server radius rad_eap
server 192.168.1.240 auth-port 1812 acct-port 1813
exit
aaa group server radius rad_mac
aaa group server
radius rad_acct192.168.1.111/24
192.168.1.112/24
Wireless
node aaa group server radius rad_admin
192.168.1.115/24
aaa group server radius dummy
server 192.168.1.240 auth-port 1812 acct-port 1813
exit
aaa group server radius rad_pmip
aaa authentication login eap_methods group rad_eap
aaa authentication login mac_methods local
aaa authorization exec default local
aaa authorization ipmobile default group rad_pmip
aaa accounting network acct_methods start-stop group rad_acct
aaa session-id common
Cisco Aironet 1200
192.168.1.240/24
192.168.1.112/24
192.168.1.111/24
(config)# radius-server local
(config-radsrv)# nas 192.168.1.240 key sharedkey
(config-radsrv)# user aaauser password aaapass
(config-radsrv)# user bbbuser password bbbpass
(config-radsrv)# exit
(config)# radius-server host 192.168.1.240 auth-port 1812
acct-port 1813 key sharedkey
(config)# exit
Author: Bill Buchanan
Wireless
node
192.168.1.115/24
Cisco Aironet 1200
192.168.1.240/24
192.168.1.112/24
192.168.1.111/24
Author: Bill Buchanan
Wireless
node
192.168.1.115/24
Cisco Aironet 1200
192.168.1.240/24
Author: Bill Buchanan
C:\>ping 192.168.1.240
Pinging 192.168.1.240 with 32 bytes of data:
Wireless
Reply from
192.168.1.240: 192.168.1.111/24
bytes=32 time=2ms TTL=255
192.168.1.112/24
node
Ping statistics for 192.168.1.240:
192.168.1.115/24 Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 1ms, Maximum = 2ms, Average = 1ms
C:\>ping 192.168.1.115
Pinging 192.168.1.115 with 32 bytes of data:
Reply from 192.168.1.115: bytes=32 time<1ms TTL=128
Ping statistics for 192.168.1.115:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms
Cisco Aironet 1200
192.168.1.240/24
192.168.1.112/24
192.168.1.111/24
ap#show dot11 assoc
802.11 Client Stations on Dot11Radio0:
SSID [NapierSSID] :
MAC Address
IP address
Device
0090.4b54.d83a 192.168.1.115
4500-radio
Others: (not related to any ssid)
Name
-
Parent State
self
EAP-Assoc
Author: Bill Buchanan
Wireless
node
192.168.1.115/24
Cisco Aironet 1200
192.168.1.240/24
192.168.1.112/24
192.168.1.111/24
ap#show dot11 assoc
802.11 Client Stations on Dot11Radio0:
SSID [NapierSSID] :
MAC Address
IP address
Device
0090.4b54.d83a 192.168.1.115
4500-radio
Others: (not related to any ssid)
Name
-
Parent State
self
EAP-Assoc
Author: Bill Buchanan
Wireless
node
192.168.1.115/24
Author: Bill Buchanan
Configure for Remote
TACACS+ Server
Cisco Aironet 1200
192.168.1.240/24
Author: Bill Buchanan
> en
# config t
(config)# hostname test
Wireless
192.168.1.112/24
192.168.1.111/24
(config)#
aaa new-model
node
(config)#
tacacs-server host 39.100.234.1
192.168.1.115/24
(config)# tacacs-server key krinkle
(config)# aaa authentication login default group tacacs
(config)# aaa authentication ppp default group tacacs
(config)# aaa authorization network default group tacacs
(config)# aaa authorization exec default group tacacs
Author: Bill Buchanan
Good Design Principles
Some Design Tips
10. Layer
2/3 switch
9. Management traffic
isolated
5. RADIUS or TACACS+
Server for centralized
authentication
F
4. DCHP for
all IP addresses
6. PKI server
which provides
digital certificates
for users and
servers.
2. Client supports
EAPs.
1. No ad-hoc
3. Encryption
networks
enabled
SNMP
7. SNMP community strong
have strong names
8. Secure protocols, such as SSH using instead
of Telnet (as plaintext passwords can be viewed
withTelnet)
Author: Bill Buchanan
8. No physical
access to access point