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7/31/2002Black Hat 2002, Las Vegas NV Advanced 802.11 Attack Mike Lynn & Robert Baird.

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Presentation on theme: "7/31/2002Black Hat 2002, Las Vegas NV Advanced 802.11 Attack Mike Lynn & Robert Baird."— Presentation transcript:

1 7/31/2002Black Hat 2002, Las Vegas NV Advanced Attack Mike Lynn & Robert Baird

2 7/31/2002Black Hat 2002, Las Vegas NV What Is NOT Covered Wired Equiv. Privacy (WEP) vulnerabilities WEP Key cracking techniques Radio signal amplification Suggested changes to the IEEE b specification Wireless network discovery tools

3 7/31/2002Black Hat 2002, Las Vegas NV What Will Be Covered Wireless network best practices Practical attacks The focus of the attack(s) The network layers The bottom 2 layers Custom (forged) b management frames The Tool Box Drivers Utilities Proof of concept code

4 7/31/2002Black Hat 2002, Las Vegas NV What Will Be Covered Attack Scenarios Denial of service Masked ESSID detection b layer MITM attack Inadequate VPN implementations Mitigation Strategies

5 7/31/2002Black Hat 2002, Las Vegas NV Wireless Best Practices Enable WEP - Wired equivalent privacy Key rotation when equipment supports it Disable broadcast of ESSID Block null ESSID connection Restrict access by MAC address Use VPN technology Use strong mutual authentication

6 7/31/2002Black Hat 2002, Las Vegas NV Practical Attacks WEP – Can be cracked passively Masked ESSID – Can be passively observed in management frames during association Block null ESSID connects – Same problem Install VPN – Weakly authenticated VPN is susceptible to active attack (MITM) Strong mutual authentication - ?

7 7/31/2002Black Hat 2002, Las Vegas NV The Network Layers

8 7/31/2002Black Hat 2002, Las Vegas NV The Bottom Layers Manipulating the bottom 2 layers of the OSI Data Link (Layer 2)  Media Access Control (MAC) – Access to medium  Logical Link Control (LLC) – Frame sync, flow control Physical (Layer 1)  Radio bit stream  Divided into channels

9 7/31/2002Black Hat 2002, Las Vegas NV The Bottom Layers

10 7/31/2002Black Hat 2002, Las Vegas NV Management Frames Management frames can control link characteristics and physical medium properties b management frames are NOT authenticated Why is this bad?

11 7/31/2002Black Hat 2002, Las Vegas NV The Tool Box Custom Drivers Air-Jack  Custom driver for PrismII (HFA384x) cards  MAC address setting/spoofing  Send custom (forged) management frames  AP forgery/fake AP Lucent/Orinoco  Linux driver modified to allow MAC address setting/spoofing from the command line Utilities User space programs – wlan-jack, essid-jack, monkey-jack, kracker-jack

12 7/31/2002Black Hat 2002, Las Vegas NV Air-Jack Driver Allows control of wireless card modes Modes 0 and 1 standard documented modes  BSS (infrastructure) (1) or IBSS (0) (Ad-hoc) Pseudo-IBSS (3) mode  Control channel selection  Firmware handles timing sensitive functions Mode 5 - undocumented  Channel selection  Firmware handles time sensitive functions  No beacons sent  Very little firmware intervention

13 7/31/2002Black Hat 2002, Las Vegas NV Air-Jack Driver Mode 6 – Host Access Point mode  Sends Beacons (firmware control)  Responds to Probe request  Handles time sensitive functions Can enable PrismII monitor mode Uses Linux PF_PACKET interface for RX and TX of raw frames

14 7/31/2002Black Hat 2002, Las Vegas NV Air-Jack Driver void send_deauth (__u8 *dst, __u8 *bssid) { struct { struct a3_80211hdr; __u16reason; }frame; memset(&frame, 0, sizeof(frame)); frame.hdr.mh_type = FC_TYPE_MGT; frame.hdr.mh_subtype = MGT_DEAUTH; memcpy(&(frame.hdr.mh_mac1), dst, 6); memcpy(&(frame.hdr.mh_mac2), bssid, 6); memcpy(&(frame.hdr.mh_mac3), bssid, 6); frame.reason = 1; send(socket, &frame, sizeof(frame), 0); }

15 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack Denial of Service – De-authentication Use MAC address of Access Point Send deauthenticate frames  Send continuously  Send to broadcast address or specific MAC Users are unable to reassociate with AP Air-Jack + WLAN-Jack

16 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack

17 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack Airopeek Trace

18 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack Airopeek Trace

19 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack Decode of Deauthentication Frame

20 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack This is your connection

21 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – WLAN-Jack This is your connection on WLAN-Jack.

22 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – ESSID-Jack Is the ESSID a shared secret? If I mask the ESSID from the AP beacons then unauthorized users will not be able to associate with my AP? Discover Masked ESSID Send a deauthenticate frame to the broadcast address. Obtain ESSID contained in client probe request or AP probe response.

23 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – ESSID-Jack

24 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios - ESSID-Jack Airopeek Trace

25 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – ESSID-Jack Airopeek Trace

26 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Monkey-Jack MITM Attack Taking over connections at layer 1 and 2 Insert attack machine between victim and access point Management frames Deauthenticate victim from real AP  Send deauthenticate frames to the victim using the access point’s MAC address as the source

27 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Monkey-Jack Victim’s card scans channels to search for new AP Victim’s card associates with fake AP on the attack machine  Fake AP is on a different channel than the real one  Attack machine’s fake AP is duplicating MAC address and ESSID of real AP

28 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Monkey-Jack Attack machine associates with real AP  Attack machine duplicates MAC address of the victim’s machine. Attack machine is now inserted and can pass frames through in a manner that is transparent to the upper level protocols

29 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Monkey-Jack Before Monkey-Jack

30 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios Monkey-Jack After Monkey-Jack

31 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios - Monkey-Jack

32 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack Dangers of wireless MITM Wireless networks are more vulnerable to MITM attacks than wired networks. Many security solutions are implemented with an assumption of a secure layer 1 and 2 Many VPN solutions are implemented with inadequate authentication for protection against wireless MITM attacks.

33 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack WAVEsec An open source software solution for securing wireless networks Uses FreeS/WAN IPSEC implementation Will thwart passive eavesdropping of wireless network communications. Implementation options  X.509 Certificates  Secure DNS

34 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack Authenticating with WAVEsec gateway Client sends modified DHCP request with client’s public key WAVEsec gateway inserts client’s public key into DNS record Client obtains WAVEsec gateway’s public key by requesting it from the DNS server IPSEC tunnel setup

35 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack Using Kracker-Jack KJ inserts to layer (like monkey-jack) KJ, using a DNS request, gets victims public key from DNS server KJ, using the victims MAC address sends DHCP request with its own key to replace the victim’s key in the DNS server

36 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack KJ initiates ISAKMP main mode SA with the WAVEsec server KJ initiates ISAKMP main mode SA with victim Victim gets new server key by DNS request serviced by KJ Two separate IPSEC tunnels are now setup All traffic passes through KJ unencrypted

37 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack

38 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack IKE – ISAKMP/Oakley Phase 1  Messages 1 and 2 – negotiate characteristics of security association; no authentication  Messages 3 and 4 – exchange random values (nonce) and execute Diffie-Hellman exchange to establish a master key (SKEYID); no authentication  Messages 5 and 6 – exchange information for mutually authenticating the parties; identity payload, signature payload, and OPTIONAL certificate payload

39 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios – Kracker-Jack IKE – ISAKMP/Oakley Phase 2 – Oakley Quick Mode  Define Security Associations  Define keys used to protect IP datagrams

40 7/31/2002Black Hat 2002, Las Vegas NV Attack Scenarios Shared key authentication attack Observe plain text challenge Observe cipher text response XOR plain text with cipher text to get key stream XOR IP packet with key stream re-using IV Broadcast ping

41 7/31/2002Black Hat 2002, Las Vegas NV Mitigation Strategies Big guy with a stick Wireless IDS and Monitoring AirDefense VPN + Strong mutual authentication RF Signal shaping – Avoiding signal leaks Antennas with directional radiation pattern Lower Access Point power

42 7/31/2002Black Hat 2002, Las Vegas NV Summary Wireless networks are more susceptible to active attacks than wired networks Enable all built-in security capabilities Use VPN with strong mutual authentication Monitor wireless network medium (air space) for suspicious activity Updates – Black Hat web site or

43 7/31/2002Black Hat 2002, Las Vegas NV Advanced Attack Robert Baird & Mike Lynn


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