Wireless Security

1. Wireless Security Chapter 24 Wireless Network Security

2. Objectives The student shall be able to: • Define the main function of the IEEE standards: 802.11a, 802.11b, 802.11g, 802.11i, 802.11n • Define Access Point, BSS, ESS, WEP, WPA2 • Describe how a man-in-the-middle attack could occur within a wireless network, and how sniffing could be used by an attacker. • Define 3 main protections for WLAN protocol configurations. • Define 3 additional protections that will help safeguard an access point or station. • Define the purposes of the phases of WLAN connections: discovery, authentication, key exchange, protected data transfer.

3. IEEE 802.11 - WIFI 802.11a - Wireless network bearer operating in the 5 GHz ISM band with data rate up to 54 Mbps 802.11b - Wireless network bearer operating in the 2.4 GHz ISM band with data rates up to 11 Mbps 802.11e - Quality of service and prioritisation 802.11f - Handover 802.11g - Wireless network bearer operating in 2.4 GHz ISM band with data rates up to 54 Mbps 802.11h - Power control 802.11i - Authentication and encryption 802.11j - Interworking 802.11k - Measurement reporting 802.11n - Wireless network bearer operating in the 2.4 and 5 GHz ISM bands with data rates up to 600 Mbps 802.11s - Mesh networking 802.11ac - Wireless network bearer operating below 6GHz to provide data rates of at least 1Gbps per second for multi-station operation and 500 Mbps on a single link 802.11ad - Wireless network bearer providing very high throughput at frequencies up to 60GHz 802.11af - Wi-Fi in TV spectrum white spaces (often called White-Fi)

4. Typical Configuration Security Issues: Shared Medium Offsite access: War Driving

5. WIFI Protocol Stack Physical Layer: Transmits bits MAC Layer: Discards packets received with errors LLC Layer: An optional layer retransmits if necessary

6. IEEE 802.11 Extended Service Set Access Point (AP): Provides access to the distribution system Can serve as the coordination function, which controls when stations are permitted to transmit. Basic Service Set (BSS): Set of stations controlled by a single coordination function (AP) Extended Service Set (ESS): A set of 1 or more interconnected BSSs/LANs that appear to the LLC as a single BSS. Distribution System: A system which internconnects a set of BSSs/LANs into an ESS

7. Man-in-the-Middle Attack 10.1.1.1 10.1.1.3 (2) Login (1) Login (4) Password (3) Password 10.1.1.2

8. Wireless Attacks Eavesdrop Attacks Active Attacks Nontraditional Networks: Other protocols (Bluetooth, PDAs) may be insecure Identity Theft: Impersonation of MAC address Denial of Service: Bombarding a WLAN with messages Network Injection: Attacker inject packets to affect connection or network configuration • Accidental Association: Connecting through the wrong Access Point • Malicious Association: Connecting through a Spoofed Access Point • Ad hoc Network: Connecting through another Station

9. Securing Wireless Transmissions • Hide Service Set Identifier (SSID) • Do not broadcast SSID • Assign cryptic name • Reduce External Signal Strength • Reduce power level • Position AP in innermost building • Use directional antennas • Use signal-shielding techniques • Encrypt all transmissions (WPA2 best)

10. MAC: Broadcast SSID

11. Secure Wireless AP • Use Firewall • Use Anti-virus/Anti-spyware software • Change Router Standard Configuration • Change default password • Change default router identifier • Configure for Specific MAC Addresses • Harder but not impossible to break in

12. Secure Station • Stolen Device • Encrypt disk • Backup data • Malware – Malicious App • Antivirus – Antispyware software • Firewall • Secure other interfaces (e.g., Bluetooth) • Secure authentication

13. Insecure WEP Protocol Problems: All devices in a network share a secret key No mutual authentication Key is static Key is limited in size and scope

14. Robust Security NetworkFive 802.11i Phases Discovery: AP & STA negotiate cipher suite and authentication method Authentication: AP & STA mutually authenticate Authentication: Can you prove you are who you say you are? Key Management: Keys are generated and distributed to AP/STA. Protected Data Transfer: Encrypted transmissions Connection Termination: Secure connection torn down

15. Discovery Phase Discovery Phase: Negotiation of: Encryption & Integrity Cipher Suite WEP TKIP CCMP Vendor Specific Authentication & Key Mgmt IEEE 802.1X Pre-shared Key Vendor-Specific Key management approach

16. Discovery Phase: 3 Stages Network & Security Capability Discovery: What device and security capabilities exist? AP broadcasts Beacons to advertise network & security policies (Optional) STA sends Probe <-> and gets Probe Response back Open System Authentication STA & AP exchange identifiers Simple for backward compatibility Association Agree on set of security capabilities Association Request (STA) Association Response (AP)

17. MAC: Beacon w. Security MAC: Probe Request (w. Security)

18. MAC: Probe Request MAC: Probe Request

19. MAC: Probe Response cont’d Probe Response, Cont’d

20. MAC: Probe Response w. Security Probe Response, cont’d w. security

21. MAC: Authentication

22. MAC: Association Response

23. MAC: Ack (Negotiation)

24. Authentication Phase Mutual authentication between an STA and Authentication Server Before Authentication: Uncontrolled All packets go to the Authentication Server After Authentication: Controlled STA packets can go to other BSS or DS.

25. Authentication Phase Stages Connect to AS (Authentication Server) STA -> AS: Connection Request AP acknowledges & forwards request EAP Exchange Extensive Authentication Protocol (EAP) IEEE 802.1X Port-Based Network Access Control The STA and AS authentication each other Secure Key Delivery AS -> STA: Master Session Key Relies on EAP for secure exchange

26. MAC: QoS Data

27. Key Management Phase:Two Types of Keys Pairwise Keys: Unicast(AP<->STA) Unique per STA Pre-Shared Key: Pre-shared before transmission PTK = HMAC-SHA-1(PMK+MAC Addresses[STA,AP]+nonce) Confirmation Key: Integrity & Authenticity of control frames Encryption: Confidentiality of key exchange Temporal key: Used for data exchange Group Keys: Multicast (AP<->STAs) GTK changed when STA leaves network Nonce: Time-related number prevents replay

28. Key Management Phase Unicast 4-Way Handshake: STA AP EAPOL-key(Anonce, Unicast)) EAPOL-key(Snonce, Unicast, MIC) (Both sides generate PTK from Anonce, Snonce, MAC addresses, PMK) EAPOL-key(Install PTK, Unicast, MIC)) EAPOL-Key(Unicast, MIC) Group Key Distribution EAPOL-key(GTK,MIC) EAPOL-Key(MIC) Notes Anonce, Snonce: Timed values & Local MAC Addresses MIC=Message Integrity Code (HMAC-MD5 or HMAC-SHA-1-128)

29. Data Transfer PhaseIEEE 802.11i Temporal Key Integrity Protocol (TKIP) WEP-Compatible Message Integrity Code (MIC) = 64 bits Calculated from MAC addresses + data + key material Data Confidentiality: Uses RC4 to encrypt MPDU+MIC Sequence number prevents replay Counter Mode CBC MAC Protocol (CCMP) Integrity: Cipher-block-chaining Message Auth. Code (CBC-MAC) Confidentiality: AES CTR block cipher mode.

30. MAC: DeAuthentication

31. Pseudo-Random Function Generator Used for Nonces Expand Pairwise keys Generate IEEE 802.11i PRF(K,A,B,Len) K=Secret key A=connection-specific text string (nonce or key expansion) B=data specific to each case Len=desired # pseudorandom bits for output Counter I, incrementing

32. Summary Protocol Design Good Practices Hidden identity Low Signal Strength Firewall Avoid default configuration (password, id) Encrypt transmissions Encrypt mobile devices Antivirus/Antispyware S/W • A set of authentication mechanisms from bad to good • Negotiated security • Mutual authentication before service • Session keys • Integrity (MAC), Nonce (Replay), Encryption • Multicast keys possible