Wireless Networking. WLAN Security Continued Module-9

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1 Wireless Networking WLAN Security Continued Module-9 Jerry Bernardini Community College of Rhode Island 3/28/2012 Wireless Networking J. Bernardini 1 Presentation Reference Material CWTS Certified Wireless Technology Specialist Official Study Guide, Chapter-10 CWNA Certified Wireless Network Administration Official Study Guide, Fourth Edition, Tom Carpenter, Joel Barrett, Chapter-09 3/28/2012 Wireless Networking J. Bernardini 2 1

2 Wireless Security Continued Expand the understanding of security technology Expand the understanding of security attacks How WEP works How WPA works How do you prevent WLAN attacks 3 Encryption: WEP/TKIP/CCMP Wired Equivalent Privacy (WEP) Temporal Key Integrity Protocol (TKIP) Counter Mode with Cipher Block Chaining Message Authentication Code Protocol (CCMP) 4 2

3 Role-Based Access Control (RBAC) Way of restricting access to only authorized users Designed to ease the task of security administration on large networks RBAC is a method of regulating access to computer or network resources based on the roles of individual users within an enterprise. Access based on roles, defined according to job competency, authority, and responsibility within the enterprise. RBAC enables users to carry out a wide range of authorized tasks Contrast to conventional methods of access control which grant or revoke user access on a rigid, object-by-object basis. In RBAC, roles can be easily created, changed, or discontinued as the needs of the enterprise evolve, without having to individually update the privileges for every user. 5 Common Attack Methods Eavesdropping Hijacking Man-in-the-middle Denial of Services (DoS) Management interface exploits Encryption cracking Authentication cracking MAC spoofing Peer-to-peer Social engineering 3/28/2012 Wireless Networking J. Bernardini 6 3

4 SSID Filtering Disable SSID broadcast. By default, most wireless networking devices are set to broadcast the SSID, so anyone can easily join the wireless network. Change the default SSID. Wireless AP s have a default SSID set by the factory. Linksys wireless products use Linksys. Change the network's SSID to something unique, and make sure it doesn't refer to the networking products, your company, department function, or location. Wired Equivalent Privacy (WEP) Guard the Confidentiality of CIA Ensure only authorized parties can view it Used in IEEE to encrypt wireless transmissions Scrambling Cryptography: Science of transforming information so that it is secure while being transmitted or stored scrambles data Encryption: Transforming plaintext to ciphertext Decryption: Transforming ciphertext to plaintext Cipher: An encryption algorithm Given a key that is used to encrypt and decrypt messages Weak keys: Keys that are easily discovered 8 4

5 WEP Cryptography 9 WEP Implementation IEEE cryptography objectives: Efficient Exportable Optional Reasonably strong Self-synchronizing WEP relies on secret key shared between a wireless device and the AP Same key installed on device and AP A form of Private key cryptography or symmetric encryption 10 5

6 WEP Characteristics WEP shared secret keys must be at least 40 bits Most vendors use 104 bits Options for creating WEP keys: 40-bit WEP shared secret key (5 ASCII characters or 10 hexadecimal characters) 104-bit WEP shared secret key (13 ASCII characters or 16 hexadecimal characters) Passphrase (16 ASCII characters) APs and wireless devices can store up to four shared secret keys Default key one of the four stored keys Default key used for all encryption Default key can be different for AP and client 11 WEP Keys - Key order must be the same for all devices - Default Keys can be different for each device 12 6

Open System Authentication Vulnerabilities Inherently weak Based only on match of SSIDs SSID beaconed from AP during passive scanning Easy to discover Vulnerabilities: Beaconing SSID is default mode

7 Open System Authentication Vulnerabilities Inherently weak Based only on match of SSIDs SSID beaconed from AP during passive scanning Easy to discover Vulnerabilities: Beaconing SSID is default mode in all APs Not all APs allow beaconing to be turned off Or manufacturer recommends against it SSID initially transmitted in plaintext (unencrypted) Vulnerabilities -If an attacker cannot capture an initial negotiation process, can force one to occur SSID can be retrieved from an authenticated device Many users do not change default SSID Several wireless tools freely available that allow users with no advanced knowledge of wireless networks to capture SSIDs 13 MAC Address Filtering AP-600b MAC Address 00022D9DE44E 1 MAC Address C5AF3B Wireless Client Access Points AP-1 Database Server Filtering = Blocking Mask: F = Look 0 = Ignore (Logical Anding) Wired MAC Adr. Wired Mask = C5AF3B = FFFFFFFFFFFF Wireless MAC Adr. = 00022D9DE44E Wireless Mask = FFFFFFFFFFFF 7

8 Access Control Filtering MAC address filtering considered to be a basic means of controlling access Requires pre-approved authentication Difficult to provide temporary access for guest devices 15 Circumventing MAC Filters MAC addresses are sent in the clear in the frame header! User/attacker can change their MAC address via software and then spoof or more accurately impersonate or masquerade under the address. Evade/Hide Network Presence Bypass Access Control Lists Authenticated User Impersonation 8

9 WEP Implementation IEEE cryptography objectives: Efficient Exportable Optional Reasonably strong Self-synchronizing WEP relies on secret key shared between a wireless device and the AP Same key installed on device and AP A form of Private key cryptography or symmetric encryption 17 WEP Characteristics WEP shared secret keys must be at least 40 bits Most vendors use 104 bits Options for creating WEP keys: 40-bit WEP shared secret key (5 ASCII characters or 10 hexadecimal characters) 104-bit WEP shared secret key (13 ASCII characters or 16 hexadecimal characters) Passphrase (16 ASCII characters) APs and wireless devices can store up to four shared secret keys Default key one of the four stored keys Default key used for all encryption Default key can be different for AP and client 18 9

10 WEP Encryption Process Initialization Vector (IV) Secret Key Plain text recommends IV change per-frame same packet is transmitted twice resulting cipher-text will be different C1 Seed Pseudorandom Number Generator PRNG C2 Integrity Algorithm Integrity Check Value (ICV) Key Stream Exclusive-OR IV Cipher text What is Transmitted WEP Keys - Key order must be the same for all devices - Default Keys can be different for each device 20 10

11 Initialization Vector The IV is a 24-bits that augments a 40-bit WEP key to 64 bits and a 104-bit WEP key to 128 bits. The IV is sent in the clear in the frame header so the receiving station knows the IV value and is able to decrypt the frame Although 40-bit and 104-bit WEP keys are often referred to as 64-bit and 128-bit WEP keys, the effective key strength is only 40 bits and 104 bits, respectively, because the IV is sent unencrypted. CCRI J. Bernardini 21 WEP Encryption Process Data Key Stream Cipher Stream (Transmitted and Received) Key Stream Data

12 WEP Encryption Process The WEP Encrypted Frame Body Encrypted IV 4 Data PDU >=1 ICV 4 Init. Vector 3 Pad 6-bits 1 Octet Key ID 2-bits WEP Keys b 64-bit shared RC4 Key. 24-bit IV plus a 40-bit Secret Key IV Secret Key 24 - bits 40 - bits 128-bit shared RC4 Key 24-bit IV plus a 104-bit Secret Key. 152-bit shared RC4 Key 24-bit IV plus a 128-bit Secret Key. PRNG Seed 12

13 WEP Weaknesses Key management and key size. 40-bit The IV is too small. 24-bit = 16,777,216 different cipher streams. The ICV algorithm is not appropriate Uses CRC-32 when MD5 or SHA-1 would be better. Authentication messages can be easily forged. Temporal Key Integrity Protocol - TKIP Part of the IEEE i encryption standard for wireless LANs (Pronounced tee-kip ) TKIP is the next generation of WEP (initially call WEP2). Provides per-packet key mixing, a message integrity check and a re-keying mechanism, thus fixing the flaws of WEP. TKIP Process begins with a 128-bit "temporal key" shared among clients and access points Combines the temporal key with the client's MAC address and then adds a relatively large 16-octet initialization vector to produce the key that will encrypt the data. This procedure ensures that each station uses different key streams to encrypt the data. Older WEP based devices can be upgraded to TKIP and not processor intensive 13

CCMP and AES Counter Mode with Cipher Block Chaining-Message Authentication Code (CCMP) CCMP uses Advanced Encryption Standard (AES) instead of RC4 algorithm CCMP/AES uses 128-bit encryption,

14 CCMP and AES Counter Mode with Cipher Block Chaining-Message Authentication Code (CCMP) CCMP uses Advanced Encryption Standard (AES) instead of RC4 algorithm CCMP/AES uses 128-bit encryption, encrypts 128-bit blocks, uses 8-bytes integrity check AES is very processor intensive Not upgradable for older devices 3/28/2012 Wireless Networking J. Bernardini 27 Advanced Encryption Standard - AES Relatively new U.S. National Institute of Standards and technology (NIST) for single-key encryption; approved in byte Block Cipher based on Rijndael (pronounced Rain Doll ) Key Lengths of 128, 192, and 256-bit Time to brute-force break an AES 256-bit key several years. AES Encryption is a four step process 14

http://en.wikipedia.org/wiki/advanced_encryption_standard AES Four Steps 1 3 2 4 3/28/2012 Wireless Networking J.

15 AES Four Steps /28/2012 Wireless Networking J. Bernardini 29 WPA There are 2 modes of WPA and WPA2 certification Enterprise and Personal Enterprise Mode (Business & Government) Personal Mode (Personal & SOHO) WPA Authentication: IEEE 802.1X/EAP Encryption: TKIP/MIC Authentication: PSK Encryption: TKIP/MIC WPA2 Authentication: IEEE 802.1X/EAP Encryption: AES-CCMP Authentication: PSK Encryption: AES-CCMP 15

Security+ Guide to Network Security Fundamentals, Third Edition. Chapter 6. Wireless Network Security

Security+ Guide to Network Security Fundamentals, Third Edition Chapter 6 Wireless Network Security Objectives Overview of IEEE 802.11 wireless security Define vulnerabilities of Open System Authentication,