Wifi Security, or Descending into Depression and Drink
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This document discusses various techniques for exploiting weaknesses in WiFi security to intercept and manipulate web traffic. It describes how unencrypted management frames and shared wireless media allow spoofing access points and intercepting sessions. With tools like LORCON, attackers can inject packets to hijack TCP streams and manipulate browsers by rewriting HTML, JavaScript and redirecting HTTPS to HTTP. Persistent attacks are also possible by caching manipulated content for long periods.
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Wifi Security, or Descending into Depression and Drink
- 1. Wifi Security -or- Descending Into Depression and Drink Mike Kershaw / Dragorn [email_address]
- 3. 802.11 2.4 and 5.8 GHz
- 4. Multiple data encodings depending on spec (11b/a/g/n)
- 6. This means we can interact with it easily
- 7. Packing your bags Unlike frequency-hopping protocols, trivial to capture 802.11
- 8. Generic Wifi card (Alfa 11g is cheap to start with)
- 9. Support in the OS (more on this later)
- 10. Total cost of ownage: $50 or so
- 11. I come not to bury 802.11... We've got a pretty good idea about 802.11 security by now
- 12. By “we” I mean “security professionals”
- 13. But even “the great unwashed” are clueing in, kind of. Encryption on home nets is up
- 14. Secure configurations WiFi is secure in proper deployments
- 15. WPA-Enterprise
- 17. Per-user keying
- 18. Mutual auth via certificates
- 19. Strong encryption We've got a pretty solid crypto system
- 20. AES used in WPA-CCMP as yet unbroken
- 21. TKIP showing flaws, but is already past sell-by date, move to CCMP
- 22. “Done Properly” WPA-Enterprise secure “done correctly”
- 23. Opportunities for failure exist if users don't validate certs (or are allowed to say 'ok')
- 24. TKIP will eventually fall
- 25. 802.11 AP Defense We've been doing this for a long time now
- 26. Best defense: Strong network architecture (again, WPA)
- 27. Monitoring for conflicting or spoofed access points
- 28. Client protection attempts to defend known good users
- 29. Client Protection Inter-client traffic can be blocked at the AP
- 30. Defending clients on a strong network is easy since the AP controls crypto
- 31. Defending clients on open AP is very hard
- 32. Denial of Service Attacks Management frames unprotected
- 33. Spoof AP, tell all clients to disconnect
- 34. Pure channel denial (flood channel with noise)
- 35. “ Crowbar” defense – find the person doing it and hit them with a crowbar.
- 36. Punching 802.11 in the gut Absurdly easy
- 37. Management frames are totally unprotected
- 38. Open networks are un-authenticateable
- 40. Strangers with candy Avoiding hostile networks requires smart users
- 41. Users are – typically – bad decision makers
- 42. The OS doesn't help: It likes to join networks it's seen before
- 43. It's hard to tell what's real, assuming the user even looks
- 45. Going viral Users like free wi-fi
- 46. Who wouldn't want to join “ Free Public Wi-Fi ”?
- 47. Once, long ago, this network probably existed
- 48. When windows can't find a network, it likes to make an ad-hoc version...
- 49. Then someone else tries to join
- 50. Sore throats Of course, this junk ad-hoc network doesn't go anywhere
- 51. Unless, say, someone brought up a network with the same name...
- 52. … And handed out IP addresses...
- 53. Which would get us LAN access to the system
- 54. But that would never happen, right?
- 55. Being too trusting Clients are really trusting
- 56. If you say you're network Foo , you must be, right?
- 57. It's very hard to avoid really bad behavior as a user
- 58. Roaming sure looks a lot like spoofing
- 59. 802.11 Roaming Multiple AP with same SSID
- 60. Client assumes the SSID is a common network
- 61. Roams to the strongest signal
- 62. Data handoff responsibility of backend (controller or common L2 network)
- 63. Only differentiator is MAC addr
- 65. The packets must flow So if an attacker has a stronger radio than the AP...
- 66. You may not be talking to who you think you're talking to
- 67. So long as the packets go through, the user never knows
- 68. Man in the middle = Win
- 69. Stuck in the middle with... Dual-interface attacker
- 70. Interface 1 connects to legitimate network (any network, or cell data, or...)
- 71. Interface 2 provides spoofed “Free Public Wifi” network.. or rhymes with “FarDucks”.. or...
- 72. More Man-in-the-middle Many sites encrypt login, but not session
- 73. Session cookies, data, etc vuln
- 74. “ The Middler”, SSLSniff, Cookie Monster
- 75. Hijack sessions via MITM
- 76. This bores me All of these attacks are really pretty boring
- 77. Why? They're really obvious.
- 78. Might still get some users, but it'll be pretty blatant
- 79. Points ARE awarded for style. Or at least, for stealth.
- 80. So wait... Didn't we say 802.11 is shared media !?
- 81. We just found the best time machine ever !
- 83. And not some hippy do-gooder time machine, either
- 85. But one where we get to bring back weapons from the future
- 87. The bad old days Hair metal, grunge, ripped jeans
- 88. Unswitched shared media Ethernet...
- 89. Sniffing the entire segment …
- 91. That's too easy It'd never be that easy, right?
- 92. Right ?
- 93. People have to have gotten smarter by now...
- 94. You'd never take a system from a secure network to an insecure network, right ?
- 96. Mmm, latte … and airports
- 97. The gym
- 98. A hotel
- 99. Bookstores
- 100. McDonalds
- 101. … shmoocon?
- 102. Making a mess Management frames have no protection
- 103. Open networks have no client protection
- 104. Nothing stops us from spoofing the AP and talking directly to a client!
- 105. No protection AP may try to filter inter-client communication by blocking packets when they hit the AP
- 106. By generating an 802.11 header FROM the AP and TO the client
- 107. The client thinks the packet is legit
- 108. The AP has no opportunity to act on it
- 109. We can communicate directly with “protected” clients on open networks
- 110. Making it easy: LORCON Writing the same injection code for every app sucks
- 111. Writing custom code for each driver sucks
- 112. Writing apps for each OS sucks
- 113. Hopefully LORCON doesn't suck
- 114. LORCON2 Unfortunately... the LORCON1 API... kind of sucked
- 115. New API modeled off of PCAP
- 116. Designed to be really easy to use
- 117. C, Ruby API
- 118. Will soon support all the cards LORCON1 did, for now, Linux
- 120. Super simple Automatically determines the driver
- 121. Automatically configures virtual network interfaces and sets up modes for injection
- 122. Send arbitrary bytes -or- use packet assembly API
- 123. The inspiration Wifi session hijacking
- 124. About 5 years ago, Toast debuted Airpwn at defcon
- 125. TCP stream hijacking on 802.11
- 126. Why hasn't everyone been using this !?
- 127. Not just for shock-porn anymore!
- 129. Rerouting streams Typical layer2 attack
- 130. TCP is only “secure” because the seq/ack is unknown
- 131. Attacker sees your L2, so seqno is known
- 132. Any TCP stream subject to abuse
- 133. Anatomy of a session Handshake
- 134. Client -> Server “GET /foo.html HTTP/1.0” Seq 123 ack 10
- 135. Server ← Client “HTTP headers, content” Seq 10 ack 189
- 136. So lets add this to MSF Lorcon Ruby wrapper
- 137. Racket packet assembly (high speed Ruby packet assembly)
- 138. Ruby PCAP
- 139. And a little TLC
- 140. Anatomy of an Evil session Handshake
- 141. Client -> Server “GET /foo.html HTTP/1.0” [seq/ack]
- 142. MSF ← Client “Malicious data...” [seq/ack]
- 143. MSF ← Client FIN!
- 144. MSF -> Server FIN! [using client seq/ack]
- 145. Server ← Client “Real data!” [old seq/ack]
- 146. MSF msf > use auxiliary/spoof/wifi/airpwn msf auxiliary(airpwn) > set INTERFACE alfa0 INTERFACE => alfa0 msf auxiliary(airpwn) > set RESPONSE "Airpwn - MSF!" RESPONSE => Airpwn – MSF! msf auxiliary(airpwn) > run
- 147. MSF msf auxiliary(airpwn) > run [*] AIRPWN: Response packet has no HTTP headers, creating some. [*] Auxiliary module execution completed msf auxiliary(airpwn) > [*] AIRPWN: 10.10.100.42 -> 208.127.144.14 HTTP GET [/files/racket/src/doc/] TCP SEQ 542050816
- 148. Fine-tuning Match & replace in regex
- 149. Response can be full JS, image replacement, HTML, a file
- 150. Sitelist YAML file for matching specific requests (poison lists of known files, like jquery)
- 151. Autogen Airpwn-MSF automatically generates HTTP headers as needed
- 152. Complete attacker control of page content including headers , too
- 153. Ill-gotten profit What does that get us?
- 155. Or in other words... Control over the page DOM
- 156. Control over forms
- 157. Control over the browser in general
- 158. Access to anything in the security context of the compromised page
- 159. Obviously scripted So we can replace content...
- 160. What do we do now?
- 161. Nearly all complex sites include a pile of javascript helper files
- 162. What happens if we replace one of those ?
- 163. It's not news, it's Javascript
- 164. JS Fragments Especially attractive
- 165. Totally invisible to the user
- 166. Multiple requests = Multiple opportunities to land attack
- 167. Run in same privilege domain as web page
- 168. I'm in your browser Rewriting your DOM
- 169. DOM = Document Object Model
- 170. Programmatic manipulation of page content
- 171. Once in the DOM we can do ANYTHING
- 173. It's not stupid, it's advanced var embeds = document.getElementsByTagName('div'); for(var i=0; i < embeds.length; i++){ if (embeds[i].getAttribute("class") == "cnnT1Img") { embeds[i].innerHTML = "..."; } else if (embeds[i].getAttribute("class") == "cnnT1Txt") { embeds[i].innerHTML = "..."; }}
- 174. DOM is tasty What else can we do?
- 175. Rewrite all FORMs to proxy through us? Sure.
- 176. Rewrite all HTTPS to HTTP so we can capture logins and “secure” data? Yup!
- 177. Poison content topical to a conference? Tin foil hat, but yes!
- 178. HTTP not so S var refs = document.getElementsByTagName('a'); for (var i = 0; i < refs.length; i++){ var rval = refs[i].getAttribute("href"); if (rval == null) { continue; } refs[i].setAttribute("href", rval.replace(/^https:/, "http:"); }
- 179. This really matters This matters
- 180. A lot .
- 181. No, seriously.
- 182. Persistence pays off Who has read rsnake's VPN paper?
- 183. Attack HTTP clients via cache control
- 184. Layer 2 attacks against web content can be made persistent
- 185. That means once you leave... you're still owned
- 186. Fast cache Short version of the VPN paper:
- 187. Browsers have cache
- 188. Cache, by nature, remains around
- 189. Users don't notice
- 190. If I own your TCP session, I own your cache control
- 191. Fast cache Client is fed a spiked JS file with cache set to 10 years
- 192. That file remains in their cache
- 193. And is re-used when they revisit that site
- 194. From inside the secure office network (or wherever)
- 195. Don't think it's a problem?
- 196. Making it happen Cache-control: max-age=99999999, public -or- Expires: Fri, 13 May 2011 13:13:13 GMT
- 197. So we hijack a common JS file
- 198. Spike it with malicious code
- 199. Set it to cache
- 200. Now when the user goes back to work and goes to twitter again...
- 201. Watch the spikes User now has a spiked, cached javascript
- 202. Browser will keep this and re-use it every time until it expires
- 203. Iframes? Kaminsky socket/sucket? Load new browser exploits?
- 204. But a user would never go to Twitter at work, right?
- 205. Poisoning the well How many sites use Urchin.js...
- 206. Hosted off the same URL at google?
- 207. What happens when we poison the url?
- 208. We get script execution on every site using it
- 209. Call home to Mom Cache modified JS that calls home every time the page is visited
- 210. Maybe no good attacks in the browser this week?
- 211. Wait for a browser 0day then flip the switch to include malware
- 212. Every system that has the cached call-home is attacked as soon as the users visit the poisoned site
- 213. There are no innocents No website is “innocent”
- 214. Websites that don't ask for logins are just as capable of feeding browser exploits
- 215. Any website can be poisoned with browser-owning code
- 216. Never underestimate fools But won't SSL solve it?
- 217. Not really, users still have to be smart enough to not accept a bad cert
- 218. And users would never do something insecure, right?
- 219. OBVIOUSLY that pop star wants me to see her naked!
- 225. Self-made cert Self-signed certificates are “obvious”
- 226. But we're technical people
- 227. “ Signed by VeriSign” vs “Signed by Verisign” “Verisign” vs “Verisign”?
- 228. Assuming a user even looks and doesn't just click “OK”
- 229. Users just want the web
- 230. “ Click OK until porn”
- 231. Well aren't you clever... I'm smart!
- 232. I use a VPN! -or-
- 233. I force my users to use a VPN via user management!
- 234. This won't work against me!
- 235. Yuh huh but... You're right, it wouldn't... …
- 236. Except your browser has no concept of security domains
- 237. What was cached in an insecure domain will remain for a secure domain
- 238. “Click OK to agree...” Many hotspots have a landing page to agree to EULA or sign in
- 239. Many first-stage landers are not encrypted
- 240. Unencrypted page on open network? Perfect target
- 241. Magic (h)8 ball If attacker controls your pre-vpn landing page...
- 242. Then the attacker can control your browser...
- 243. Iframes? Pop-under windows? Ajax queries dumped to nowhere?
- 244. Top 10 countdown All the attacker needs to do is inject code to go to the top N pages the victim may be likely to visit
- 245. Request page in the background
- 246. Cache spiked page (which the victim never saw)
- 247. Smart JS Attacker landing page can request content multiple times
- 248. Compare content with signature for attack
- 249. Request again if attack didn't land
- 250. Now we own arbitry sites in cache PRE-VPN
- 251. Frequent Landings Take it one step further: VPN allows access to internal pages, right?
- 252. So if the attacker controls L2...
- 253. D umb N etwork S tuff If we own L2, can we attack other protocols?
- 254. Sure can!
- 255. Race the DNS server!
- 256. Wait for a DNS query, then...
- 257. Set a QR flag on the request and supply our own response
- 258. DNS-pwn in MSF Same model as Airpwn
- 259. YAML config to match multiple queries with different responses
- 260. Races DNS server to give user a “custom” IP
- 261. Your intranet is showing So if we control the browser
- 262. We control DNS resolution
- 263. We can re-try as quickly as we want thanks to a JS script that watches for success...
- 264. What stops us from caching http://intranet/
- 266. How about a shim that ships your internal pages off to a remote server once you're on VPN?
- 267. Or just rewrites all your form DOMs to proxy out?
- 268. Browsers cache other stuff too! Browsers are great!
- 269. Speed of user experience is the biggest concern...
- 270. So lets cache DNS in the browser, too!
- 271. So this means...?
- 272. Trust me, it's over here Pre-VPN browser DNS poisoning
- 273. Post-VPN site control thanks to guessed internal DNS names being cached as external servers
- 274. “Mobile Convergence”
- 275. “Smart” phones are dumb? So-called “smart” phones are really general-purpose computers now
- 276. Complex browsers
- 278. Yup, very happy to cache data
- 279. Not talking to you Of course, all the smartphones are on cell networks, right?
- 280. I'll just use 3G!
- 281. You can't see me there!
- 282. True...
- 287. Used to fail Smartphone users are used to going to wifi
- 288. Some prefer it – power / speed / data limits
- 289. Besides, we could “help” them along...
- 291. No, you shouldn't You absolutely should NOT go to import sites
- 292. You should NOT buy illegal cell phone jammers to force victims to use wifi
- 293. And of course someone trying to own your company wouldn't do something illegal , right?
- 294. Where we go from here Future plans:
- 295. Better MSF integration with other L2 attacks
- 296. Dynamic content generation based on target
- 297. Integration with browser autopwn
- 298. In summary... We've more or less figured out how to defend access points
- 299. It's much harder to defend clients
- 300. Especially when they go off into the world onto insecure APs
- 301. In summary... Using an open network?
- 302. Sites you think you trust, you can't
- 303. Spiked attacks can stay resident in the browser
- 304. Your users might be bringing something back with them
- 305. In summary... This is bad even for smart users
- 306. Normal users don't stand a chance
- 307. You may already be screwed
- 308. I warned you this would be depressing...
- 309. Trying to fix it Use a VPN – at least it's a start despite the problems
- 310. Easy for US
- 311. Hard for most users
- 312. Hard to enforce: Users don't like barriers between them and internet
- 313. Other options SSH SOCKS tunneling (basically just a VPN)
- 314. Mandate updates (easier said than enforced)
- 315. Forbid users from taking laptops onto open networks (policy, UAC, don't give out laptops?)
- 316. Tragedy of trust Would be nice to say “move open networks to WPA”
- 317. WPA-PSK? Better but not a solution.
- 318. WPA-EAP? Better still, even with the same user/password you get per-user keying
- 319. Tragedy of trust But WPA-EAP requires SSL
- 320. If cert is signed by a common CA, easy to get another from the same CA
- 321. If cert is signed by self-sign CA user has to accept
- 322. Up to user to determine valididy
- 323. Not what users are good at
- 324. Stuck in the rut Hard to deploy secure public networks
- 325. Some vendors try to solve it with custom clients
- 326. Ties into specific OS then
- 328. No really good solution yet
- 329. Protecting yourself Manually enforce security domains
- 330. Use different browsers for login and normal use
- 331. Manually clear cache
- 332. Never keep windows open between security domains
- 333. Still scary, forget once and you're screwed
- 334. Thanks to.. Rsnake
- 335. HDM
- 336. Toast
- 337. Renderman
- 338. Jesse Burns
- 339. Everyone else who has listened to me rant about this
- 340. Q & A Lorcon @ 802.11ninja.net
- 342. MSF @ metasploit.com