57. WIRELESS SECURITY

INTRO TO WIRELESS NETWORK SECURITY

• Although SECURITY is important in ALL NETWORKS, it is even more essential in WIRELESS NETWORKS

• Because WIRELESS SIGNALS are not contained within a WIRE, any DEVICE within range of the signal can receive traffic

• In WIRED NETWORKS, traffic is often only ENCRYPTED when sent over an UNTRUSTED NETWORK such as the INTERNET

• In WIRELESS NETWORKS, it is VERY important to ENCRYPT traffic sent between the WIRELESS CLIENTS and the AP

• We will cover THREE MAIN CONCEPTS:

  • AUTHENTICATION
  • ENCRYPTION
  • INTEGRITY

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AUTHENTICATION

• All CLIENTS must be AUTHENTICATED before they can associate with an AP
• In a corporate setting, only TRUSTED USERS / DEVICES should be given ACCESS to the NETWORK
  • In corporate settings, a separate SSID which doesn’t have ACCESS to the corporate NETWORK can be provided for GUEST USERS
• Ideally, CLIENTS should also AUTHENTICATE the AP to avoid associating with a malicious AP
• There are MULTIPLE WAYS to AUTHENTICATE:
  • PASSWORD
  • USERNAME / PASSWORD
  • CERTIFICATES

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ENCRYPTION

• Traffic sent between CLIENTS and APs should be ENCRYPTED so that it can’t be read by anyone except the AP and the CLIENT
• There are many possible PROTOCOLS that can be used to ENCRYPT traffic
• All DEVICES on the WLAN will use the same PROTOCOL, however each CLIENT will use a unique ENCRYPTION / DECRYPTION KEY so that other DEVICES can’t read its traffic
• A “GROUP KEY” is used by the AP to ENCRYPT traffic that it wants to send to all of its clients
  • All of the CLIENTS associated with the AP keep that key so they can DECRYPT the traffic

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INTEGRITY

• As explained in the “SECURITY FUNDAMENTALS” video of the course, INTEGRITY ensures that the message is not modified by a third-party
• The message that is sent by the SOURCE HOST should be the same as the message that is received by the DESTINATION HOST
• A MIC (Message Integrity Check) is added to the message to help protect their INTEGRITY.

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AUTHENTICATION METHODS

The original 802.11 STANDARD included TWO OPTIONS for AUTHENTICATION:

• OPEN AUTHENTICATION
  • The CLIENT sends an AUTHENTICATION REQUEST and the AP just accepts it
  • The is clearly NOT a SECURE AUTHENTICATION method
  • After the CLIENT is AUTHENTICATED and associated with the AP, it’s possible to require the USER to AUTHENTICATE via other methods before ACCESS to the NETWORK is granted (ie: Starbucks WI-FI)
• WEP (Wired Equivalent Privacy)
  • WEP is used to provide both AUTHENTICATION and ENCRYPTION of WIRELESS traffic
  • For ENCRYPTION, WEP uses the RC4 ALGORITHM
  • WEP is a “SHARED-KEY” PROTOCOL, requiring the SENDER and RECEIVER to have the same KEY
  • WEP KEYS can be 40 bits or 104 bits in length
  • The above KEYS are combined with a 24-bit “IV” (INITIALIZATION VECTOR) to bring the total length to 64 bits or 128 bits
  • WEP ENCRYPTION is NOT SECURE and can easily be cracked
  • WEP can be used for AUTHENTICATION like this:

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EAP (Extensible Authentication Protocol)

• EAP is an AUTHENTICATION FRAMEWORK
• It defines a STANDARD SET of AUTHENTICATION FUNCTIONS that are used by the various EAP METHODS
• We will look at FOUR EAP METHODS:
  • LEAP
  • EAP-FAST
  • PEAP
  • EAP-TLS
• EAP is integrated with 802.1X which provides PORT-BASED NETWORK ACCESS CONTROL

802.1X is used to limit NETWORK ACCESS for CLIENTS connected to a LAN or WLAN until they AUTHENTICATE

There are THREE MAIN ENTITIES in 802.1X:

• SUPPLICANT : The DEVICE that wants to connect to the NETWORK
• AUTHENTICATOR : The DEVICE that provides access to the NETWORK
• AUTHENTICATION SERVER (AS) : The DEVICE that receives CLIENT credentials and PERMITS / DENIES ACCESS

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• LEAP (Lightweight EAP)
  • LEAP was developed by Cisco an an improvement over WEP
  • CLIENTS must provide a USERNAME and PASSWORD to AUTHENTICATE
  • In addition, MUTUAL AUTHENTICATION is provided by both the CLIENT and SERVER sending a CHALLENGE PHRASE to each other.
  • DYNAMIC WEP KEYS are used, meaning that the WEP KEYS are changed frequently
  • Like WEP, LEAP is considered vulnerable and should not be used anymore

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• EAP-FAST (EAP FLEXIBLE AUTHENTICATION via SECURE TUNNELING)
  • EAP-FAST was also developed by Cisco
  • Consists of THREE PHASES:
    • A PAC (PROTECTED ACCESS CREDENTIAL) is generated and passed from SERVER to CLIENT
    • A SECURE TLS TUNNEL is established between the CLIENT and AUTHENTICATION SERVER
    • Inside of the SECURE (ENCRYPTED) TLS TUNNEL, the CLIENT and SERVER communicated further to AUTHENTICATE / AUTHORIZE the CLIENT

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• PEAP (PROTECTED EAP)
  • Like EAP-FAST, PEAP involves establishing a SECURE TLS TUNNEL between the CLIENT and SERVER
  • Instead of a PAC, the SERVER has a DIGITAL CERTIFICATE
  • The CLIENT uses this DIGITAL CERTIFICATE to AUTHENTICATE the SERVER
  • The CERTIFICATE is also used to establish a TLS TUNNEL
  • Because only the SERVER provides a CERTIFICATE for AUTHENTICATION, the CLIENT must still be AUTHENTICATED within the SECURE TUNNEL
    • Example: MS-CHAP (Microsoft Challenge-Handshake Authentication Protocol)

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• EAP-TLS (EAP TRANSPORT LAYER SECURITY)
  • Whereas PEAP only requires the AS to have a CERTIFICATE, EAP-TLS requires a CERTIFICATE on the AS and on every single CLIENT
  • EAP-TLS is the MOST SECURE WIRELESS AUTHENTICATION method, but it is more difficult to implement than PEAP because every CLIENT DEVICE needs a CERTIFICATE
  • Because the CLIENT and SERVER AUTHENTICATE each other with DIGITAL CERTIFICATES, there is no need to AUTHENTICATE the CLIENT within the TLS TUNNEL
  • The TLS TUNNEL is still used to exchange ENCRYPTION KEY information (ENCRYPTION methods will be discussed next)

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ENCRYPTION / INTEGRITY METHODS

• TKIP (Temporal Key Integrity Protocol)
  • WEP was found to be vulnerable, but WIRELESS hardware at the time was built to use WEP
  • A temporary solution was needed until a new STANDARD was created and a new HARDWARE was built
  • TKIP adds various SECURITY FEATURES:
    • A MIC (Message Integrity Check) is added to protect the integrity of messages
    • A KEY MIXING ALGORITHM is used to create a unique WEP key for every frame
    • The INITIALIZATION VECTOR is doubled in length from 24 bits to 48 bits, making BRUTE-FORCE attacks much more difficult
    • The MIC includes the SENDER MAC ADDRESS to identify the FRAME’s SENDER
    • A TIMESTAMP is added to the MIC to prevent replay attacks. Replay attacks involved re-resending a FRAME that has already been transmitted
    • A TKIP SEQUENCE NUMBER is used to keep track of FRAMES sent from each SOURCE MAC ADDRESS. This also protects against REPLAY ATTACKS

** You probably don’t need to memorize ALL of the above features

** TKIP is used in WPA version 1, which will be discussed in the next section

• CCMP (Counter / CBC-MAC Protocol)

  • CCMP was developed after TKIP and is more SECURE
  • It is used in WPA2
  • To use CCMP, it must be supported by the DEVICE’S hardware.
  • Old hardware built only to use WEP / TKIP cannot use CCMP
  • CCMP consists of TWO DIFFERENT ALGORITHMS to provide ENCRYPTION and MIC :
    • AES (Advanced Encryption Standard) COUNTER MODE ENCRYPTION
      • AES is the MOST SECURE ENCRYPTION PROTOCOL currently available.
      • Widely used all over the world
      • There are multiple MODES of operation for AES.
      • CCMP uses “COUNTER MODE”
    • CBC-MAC (CIPHER BLOCK CHAINING MESSAGE AUTHENTICATION CODE)
      • Used as a MIC to ENSURE the INTEGRITY of MESSAGES

• GCMP (GALOIS / COUNTER MODE PROTOCOL)

  • GCMP is MORE SECURE and EFFICIENT than CCMP
  • Its increased efficiency allows higher data throughput than CCMP
  • It is used in WPA3
  • GCMP consists of TWO ALGORITHMS:
    • AES COUNTER MODE ENCRYPTION
    • GMAC (GALOIS MESSAGE AUTHENTICATION CODE)
      • Used as a MIC to ENSURE the INTEGRITY of MESSAGE

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WI-FI PROTECTED ACCESS (WPA)

• The WI-FI Alliance has developed THREE WPA CERTIFICATIONS for WIRELESS DEVICES:

  • WPA
  • WPA2
  • WPA3

• To be WPA-CERTIFIED, EQUIPMENT must be TESTED in authorized testing labs

• All of the above support TWO AUTHENTICATION MODES:

  • PERSONAL MODE :
    • A PRE-SHARED KEY (PSK) is used for AUTHENTICATOIN
    • When you connect to a home WI-FI NETWORK, enter the PASSWORD and are AUTHENTICATED, that is PERSONAL MODE
    • This is common in small NETWORKS
    • The PSK itself is NOT sent over the air
    • A FOUR-WAY HANDSHAKE is used for AUTHENTICATION and the PSK is used to GENERATE ENCRYPTION KEYS
  • ENTERPRISE MODE :
    • 802.1X is used with an AUTHENTICATION SERVER (RADIUS SERVER)
    • No specific EAP METHOD is specified, so all are supported (PEAP, EAP-TLS, etc)

  WPA

  • The WPA CERTIFICATION was developed after WEP was proven to be vulnerable and includes the following PROTOCOLS:
    • TKIP (based on WEP) provides ENCRYPTION / MIC
    • 802.1X AUTHENTICATION (ENTERPRISE MODE) or PSK (PERSONAL MODE)

  WPA2

  • Was released in 2004 and includes the following PROTOCOLS:
    • CCMP provides ENCRYPTION / MIC
    • 802.1X AUTHENTICATION (ENTERPRISE MODE) or PSK (PERSONAL MODE)

  WPA3

  • Was released in 2018 and includes the following PROTOCOLS:

    • GCMP provides ENCRYPTION / MIC

    • 802.1X AUTHENTICATION (ENTERPRISE MODE) or PSK (PERSONAL MODE)

    • WPA3 also provides several additional security features:

      • PMF (PROTECTED MANAGEMENT FRAMES)
        • Protecting 802.11 MANAGEMENT FRAMES from eavesdropping / forging
      • SAE (SIMULTANEOUS AUTHENTICATION OF EQUALS)
        • Protects the four-way handshake when using PERSONAL MODE AUTHENTICATION
      • FORWARD SECRECY
        • Prevents DATA from being DECRYPTED after it has been transmitted over the air so an ATTACKER can’t capture WIRELESS FRAMES and then try to DECRYPT them later