Black ops 2012

1. Black OpsDan KaminskyChief [email protected] (2012)

2. Another Year, Another Talk Good News and Bad News Good News: Were going to fix this thing. We have no choice. The global economy is based on Information Technology being trustworthy. An economy where you have to be big enough to field a cyber army in order to participate, is a broken economy indeed Its not like the big guys are doing a great job defensively Bad News: Were not going to fix it according to dogma. Hows the status quo working out for us? There are many alternatives to dogma that are even worse How do we find those that are better?

3. A Riddle What is the fundamental difference between attack and defense?

4. Answer When an attack doesnt work, you can tell. Offense has an inherent quality filter Put up or shut up Doesnt mean there arent bugs in offensive disclosure The Oracle Critical is just an unencrypted transport if itsa bug, then Wireshark is dropping hundreds of 0day Press Will Report Anything But its not the same

5. The Reality Of Defense Too much dogma Not enough science You have to defend against every bug -> Thatsimpossible -> You dont have to show youve defendedagainst anything Critiques of defenses arent much better nobody ismeasuring or critiquing effectiveness So this is a talk about skepticism and the processes offinding effective defenses to the real and legitimatethreats we cannot ignore You shouldnt agree with everything Im going to present My goal is to show you some new ideas, and give you aframework to consider them as worthwhile or not This is the only way were going to get defense to work Lest you think theres nothing concrete here

6. The Fundamental Test Take 2000 systems with a defense. Take 2000 systems without. Come back in six months, and manually audit all 4000 systems. Is there or is there not a statistically significant difference in theinfection rate? Even if we dont do the above, let us at least respect a goldstandard when we see one! The time may come when we spend as much money onsecurity research as we do on medical research. Medicine took hundreds of years to become scientific, and theyhad dead bodies to motivate them We dont have dead bodies, or hundreds of years. We still need to fix these problems. Some vendors out there care along these lines. Reward them!

7. The Three Heads Of The SecurityHydra 1) The inability to authenticate 2) The inability to write secure code 3) The inability to bust the bad guys What were not talking about today Authentication DNSSEC no time, ask me in private (or waita few months) Busting the bad guys Remarkable lack of consensus regarding which bad guys are mostimportant I tend to worry about the Aurora attack, which involved espionageagainst (lets face it) the entire Fortune 500, and against those raidingSMB payrolls, because that calls into question the very viability ofSMB Others have different priorities What we are talking about The inability to write secure code

8. An immediate clarification Its not that its impossible to write secure code Its not impossible to deploy X.509 PKI Its not impossible to bust the bad guys Its just plainly and utterly improbable At least in most organizations Possible is not enough. Probable or bust.

9. What are we looking at today? How do we address timing attacks? How do we generate random numbers? How do we suppress SQL Injection? How do we detect network manipulation? How do we scan the Internet? These are all things that are possible today. How do we make them more deployable, less expensivemore probable?

10. Timing Attacks Many systems are modeled in terms of just what datathey send Not in terms of when they send it Sometimes data leaks security sensitive data Possible to distinguish 15-100 microseconds oflatency over Internet, and 100 nanoseconds oflatency over LAN (1000 samples) Opportunities and limits of remote timing attacks (Scott ACrosby , Rudolf H. Riedi , Dan S. Wallach) Possible to exploit string comparison functions inwidespread scripting languages, thus breaking HMACcompare (OpenID/OAuth) Exploiting timing attacks in widespread systemsNate Lawson and Taylor Nelson @ Black Hat 2010

11. The Proposed Fix Any time values need to compared in a security critical context, compare them in constant time (so that theres no correlation between whats compared, and how long it takes) public static boolean isEqual(byte[] a, byte[] b) {if (a.length != b.length) { return false; }int result = 0;for (int i = 0; i < a.length; i++) {result |= a[i] ^ b[i] } return result == 0;} Looks good, right?

12. The Problem You have to remember to do this everywheretheres a security critical comparison You dont get to do it all the time, because theperformance impact is too high You thus must actually identify all the securitycritical comparisons Its possible. But its not probable.

13. A Solution? I seem to note that distinguishing against Internetnoise yields less accuracy (15,000-100,000ns) thanLAN noise (100ns) Thats three to four orders of magnitude! And Internet noise is not actually random What if we actually did have a random delay? tc qdisc change dev eth0 root netem delay3ms 1ms For all packets emitted from the first Ethernet interface, add arandom amount of lag between 1,000,000ns and 3,000,000ns Boltzmann Filter At minimum, the LAN should be as secure as theInternet. Maybe Internet attackers also are impacted. This is a lot easier to deploy. That really matters. But does it work?

14. What Could Go Wrong? All timing noise can be averaged out eventually, so a global randomdelay cant work Pretty much all password comparisons are done with non-constant time compares, so I guess all passwords are vulnerable? Heres some SSH 0day sys_auth_passwd(Authctxt *authctxt, const char *password){/* Encrypt the candidate password using the proper salt. */ encrypted_password = xcrypt(password, (pw_password[0] && pw_password[1]) ? pw_password : "xx"); return (strcmp(encrypted_password, pw_password) == 0); Strcmp is not constant time. So, you just offline brute force for passwords that have certain characters and see how far you get. It is highly unlikely that the above attack actually works Nanosecond differentials are too small to recover Maybe not locallyhmmm

15. What We Really Need To Know How much timing noise, of what nature, willpermanently obscure how much timing signal beyondthe point of infeasible return? Somewhere between 1 nanosecond and 1 day thereis an amount of noise that will indefinitely obscure an nnanosecond differential Theres likely to be an equation here CSI Enhance has its limits There is a limit to how much lag we can ask for, from theperformance guys It is higher for some requests than for others We might require more lag than perf is willing to give (at leastin general) Need to discover these numbers

16. What could actually go wrong The distribution of lag from the interface may be easyto filter Quantized into 1ms chunks? Gaussian when it should be uniform, or uniform when itshould be Gaussian Could be filterable thanks to TCP timestamps (whichhave ~10ms accuracy, but also have sharp edges) All of the above can be fixed, the question is if theyneed to be The perfect (constant time comparisons) is the enemy ofthe good (interface-wide jitter) Jitter does not need to apply to all packets; could be a TCP setsockopt or whatnot Could also be applied at the end of a php script

17. Another Day, Another Time RSA is broken! No, not the thing with the smartcards that would(maybe, depending on vendor) leak their private key No, not the thing with the SecureID seeds that were stolen The thing with certificates with easily breakable RSA keys Something like 1 in 200 RSA keys on the Internet failed! Hughes and Lenstra had first announce, Nadia Heninger had parallelresearch At the time, the break was blamed on RSA itself Two primes in RSA (p and q) If either is repeated (p and q1, p and q2), then all are easy toderive Euclids Greatest Common Denominator RSA is bad!

18. Reality Bad random number generators create trapdoor functions in all cryptosystems Rather than breaking the crypto, you guess the key Basic concept of 2011s Phidelius (expanded a password into a pseudorandom stream, which was then used to feed a key generator for RSA/DSA/ECC). Bad RNG isnt a bug, its a feature! They thought theyd shown RSA was bad They actually showed that RNGs are still broken Debians bug wasnt just Debians Werent operating systems supposed to fix this?

19. Theory Collecting and providing entropy is hard; let theoperating system do it for you /dev/random for good bits, /dev/urandom for best effortbits If /dev/random runs out of bits, block until more arefound Sources for entropy Hardware RNG Keyboard Mouse Disk Rotation (as impacted by air) Problem: Lots of environments dont have any of that

20. Actual Environments Desktops Humans w/ keyboards and mice Often disks Servers Sometimes have disks VMs Embedded devices

21. The Reality of Hardware RNG Its just not there. Yes, I know Ivy Bridge is coming out with aHardware RNG. In 2012. Thats top of the line gear now. Yes, I know some TPMs are reported to haveHardware RNGs. For some reason, people treat TPM hardware asunstable radioactive gunk Its also rarely in embedded kit

22. Whats Happening: An Analogy Proteins causes cancer http://ukpmc.ac.uk/abstract/MED/3007842/reload=0;jsessionid=3X3Cs6G7VbyRT1xEPcUX.4 Carbohydrates cause cancer http://www.smh.com.au/lifestyle/diet-and-fitness/high-carbohydrate-diet-tied-to-cancer-20110616-1g4o9.html Fats cause cancer http://www.telegraph.co.uk/health/healthnews/5650141/High-fat-diet-can-increase-risk-of-deadly-cancer.html Alcohol causes cancer http://pubs.niaaa.nih.gov/publications/arh25-4/263-270.htm So you dont consume proteins, carbohydrates, fats, orbooze. You starve to death.

23. What Actually Happens How do I know? I actually asked some devs. 1) They have some code that depends on/dev/random 2) On initialization of their embedded device, the codetries to generate a key. 3) Theres no human at the keyboard, no hand at themouse, no disk to spin, and no hardware RNG./dev/random blocks. The device is a brick. Quite literally, starving for entropy 4) At best, they switch to /dev/urandom. At worst theyswitch to rand() and then they ship. /dev/urandom is underseeded, though, and is still broken

24. A comparison What perfectionists think will happen: Its broken! Sure theyll demand hardware RNG! What developers actually do: Security failed us again. Lets ship something thatworks. Perfectionism caused (at least) 1 out of 200 RSA keys on the Net to be easily broken Its almost certainly worse than that Those are just the keys we can easily detect We can do better.

25. TrueRand: An Old Hack [0] Why do we like measuring keyboard and mice? Humans and computers are not synchronized Humans do not operate on nanosecond clocks like computers do Human is slow clock, CPU is fast clock Any system with two clocks, has a Hardware Random Number Generator Even if the error is one part per million, thats a bit per second per megahertz The error is generally much larger than a part per million, just from thermal noise (Not just thermal noise)

26. TrueRand: An Old Hack [1] What TrueRand (from Matt Blaze and D.P. Mitchell, in1996) does Run the CPU in a tight loop (count++); Every 16ms, fire an interrupt On interrupt, shuffle the count variable, and integrate it into abuffer The entropy comes in here timer is slow clock, CPU isfast clock After 11 shuffles, return the buffer as an integer Hash two buffers together using sha1, return only thefirst byte It aint bad. But its disowned. Thats too bad, because it would have prevented (atleast) 1/200 keys from being broken.

27. Why is it disowned? (Literally Matt Blaze was vaguely horrified thatIm revisiting this code) Perfectionism We cant model its behavior. We dont know howgood or bad it is, so we shouldnt do it at all. This attitude has actually led to a reduction inavailable entropy in the Linux kernel Used to look at interrupt counts from variousdevices Now they arent used, because they might bepolluted

28. DakaRand 1.0 [0] An update to the old model Multiple generators Sleepers: Measure usleep with CLOCK_MONOTONIC CLOCK_REALTIME RDTSC (on X86 platforms) CPU counter there are equivalents for ARM, MIPS Incrementer: See how many times we can increment an integer within a certain time period (100% CPU)

29. DakaRand 1.0 [1] RTC: Measure interrupts from the realtime clockusing CLOCK_MONOTONIC (dedicated IRQ!) 128hz 8192hz Threads: Measure the status of an integermodulated by a runaway thread (100% CPU) Anyone who thinks computers are completely deterministiccreations has never written threaded code ;) Two Threads, One Int (one adds, one subtracts, main polls) Two Threads, Two ints (both add, main compares) One Thread, One Int (one adds, main polls) Possible addition: Noisier functions than add

30. DakaRand Flow Short version Push all bits into a SHA-256 Hash Dont undercount entropy Only count them as entropy when they pass Von Neumanns debiasing check Count 1s to decide whether 0 or 1 Throw away 00 and 11, count only 01 and 10 Actually insert a 0 or a 1 when you count a bit Dont overcount entropy Scrypt (time/memory hard function) the resulting SHA- 256 value Make it miserable to guess entropy Use the output of Scrypt as the input to AES-256-CTR, emit the resulting stream

31. Attacking DakaRand The game: Find a platform (Desktop/Server/VM/Embed) oran OS under which DakaRand provides poor entropy in oneof its modes Userspace/Hypervisor Scheduling Were only called some number of times per second These times per second may be at predictable intervals If sufficiently predictable, theyll bias the output Will they simultaneously and identically bias both clocked entities? Autoclocking If you time something against itself, youre going to have a bad time Clocks are highly correlated to themselves RTC and CLOCK_MONOTONIC could be the same underlying timer in a VM VMs, more than anything else, should be exposing a random device (even if the random device itself uses clock differentials) Still, this code seems to still work on VMs

32. The VM Cloning Issue /dev/random keeps bits around for a long time When you clone an image, you end up with those bitsbeing static for a long time Meaning you keep generating the same entropy for a longtime DakaRand attempted guarantee: Each read is atomic The results of the read may be used across multiple images But two separate calls at two separate times MUST yield twouncorrelated streams Cant do anything after the read is fully completed During the read (which does last a second, due to scrypt)is already after I actually dont think you can do better than this, though Iwas considering XORing the keystream with /dev/urandomanyway

33. Is The Underlying Use Of CryptoSafe? Modified Von Neumann We absorb a tremendous amount of data into our hash structure that has obvious patterns If you have 100GB of 0s and 128 bits of actual randomness, output of hash has 128 bits of randomness We do explicitly include the 0 and 1 Stream Function vs. Raw Output Lots of raw output from a function tends to leak external state So lets not leak external state. Cryptographic Stream Function RNGs tend to have their own family of functions that are distinctly not cryptographically validated Mersenne Twister, not AES-256 in Counter Mode Is it in fact the case that strong (not RC4) cryptographic functions encompass all properties of RNGs? Well, what does dieharder say?

34. DieHarder CipherSuite Test About 16,000 CPU hours of DieHarder Entropy Testswas run across 21 ciphers, with inputs of either 16MBof zero or (the same) 16MB of /dev/urandom output About 24,000 different tests per cipher/content class Thanks, Jamie Schwettman, who did all the work tomake this sweep happen No obvious statistical leanings to the data Machine learning people are taking a look Thanks, Prior Knowledge, Aleks Jakulin! No conclusive findings yet Releasing this data too

35. Neat tool want it?csql: run SQL against CSV files $ cat pass2.csv | head -n 20000 | ./csql - "SELECT cipher,content, test, subtest, count(pv), avg(pv) from c group by cipher,content, test, subtest;" | head -n 10 aes-128-cbc,urandom,dab_bytedistrib,0,10,0.0 aes-128-cbc,urandom,dab_dct,256,10,0.47393035 aes-128-cbc,urandom,diehard_2dsphere,2,10,0.627572674 aes-128-cbc,urandom,diehard_3dsphere,3,10,0.664239991 aes-128-cbc,urandom,diehard_birthdays,0,10,0.50850473 aes-128-cbc,urandom,diehard_bitstream,0,10,0.017056331 aes-128-cbc,urandom,diehard_count_1s_byt,0,10,0.441374983 aes-128-cbc,urandom,diehard_count_1s_str,0,10,0.538731369 aes-128-cbc,urandom,diehard_craps,0,20,0.0394997795 aes-128-cbc,urandom,diehard_dna,0,10,0.396250338

36. Kernel Recommendations /dev/random MUST not block. Make an IOCTL if you must Return data slowly if you like CryptGenRandom on Windows does not appear to block 1 out of 200 RDP keys are not likely to be corrupt Dont be so shy about interrupt sources Care less about interrupt counts than interrupt timings ftrace exposes microsecond timings, which might not be finegrained enough Use nanosecond arrival times, as much as possible, from deviceson foreign busses. The slower the foreign device is, the better. You want to be measuring slow clocks against fast clocks By definition, the kernel is interrupted at finer grain than userspace. Obviously you dont have to include every last interrupt it takestime to check the time. Maybe consider this Modified Von Neumann construction

37. From The Bottom To The Top Our biggest problems in security do not revolvearound Random Number Generation They revolve around languages Language Theoretic Security: The hypothesis thatsecurity vulnerabilities are the consequence of thelanguages code is written in Coined by Len Sassaman and Meredith Patterson Sapir-Whorf is true for code Corollary: If language got us into this mess, languagecan get us out More important corollary: Languages are spoken orwritten by humans. Ignore their needs at your peril.

38. The Shift One way to look at language theoretic security is through the lens of computability theory Different classes of code have different amounts ofpower, and communication should be limited tothe least amount of power necessary Attacks expands power from Declarative to throughRegular Expression through Turing Complete This is indeed a valid lens Another lens

39. Diagramming Sentences:IT WAS ACTUALLY USEFUL

40. Injection Vulnerabilities:When Trees Disagree Parsers, almost by definition, turn streams of bytes intotrees Injection Vulnerabilities exist when a sending language and areceiving language (which may or may not be the same)disagree on the nature of the tree sent An extreme case of this is when bytes flow out intosurrounding memory But SQL Injection, LDAP Injection, XSS, etc are all justsituations where (generally) the sender thought it sent theusers data, but the receiver thought it received a peers code A purely declarative language can still (easily) be injected into, andcomplexity can remain declarative and still yield damage. The attackis not in the increase of complexity, but in the transition of content fromone identity/context to another through parse tree differentials. So what?

41. We have to stop injectionvulnerabilities Theyre killing us Theyre not l33t Theyre totally effective Theyre the vast majority of vulnerabilities everwritten and discovered We havent actually fixed them If we did fix them, they wouldnt still be costingbillions of dollars [Yes, were going to revisit Interpoliqueits OK,were going to bash it too]

42. What is the importance of anothertheoretical model? It declares the rules of the game. 1) We want to synchronize parse trees. 2) We want developers to actually use our method. A language unspoken has a term: A dead language It explains what is surprisingly not understood Why did XML become popular? Instead of spending months figuring out just how to sayhello, they have their code, you have your code, and its selfdescribing strings in each direction. No fiddly the eighth biton the fourth byte changes everything Why did JSON become popular? XML invented its own modes of being fiddly

43. The Hard Truth Developers are in charge. Not architects (they love ASN.1 and XML and WS-ZOMG) Not academics (they love Haskell) Not management (they love money) Money is made byperformance, reliability, maintainability, features, rapiddevelopment Money is later lost by security, maybe So, not us. What is the #1 thing developers like? Code working

44. Thus, the biggest explanation Why is PHP so popular? If you dont think it is, see here: What is PHP incredibly good at? Copy and paste codeand it works We understand that CPAN makes PERL We dont understand that PHP sample codemakes PHP Java Alternative: Look how much code my IDE can write for me! Copy and paste with a suit on

45. The Language Success Metric What are the odds, if I try this, that it will work? Not, when it fails, it fails fast! Surprisingly, nobody tracks this metric (Except maybe Processing, which is incredible) Thats why all the successful languages tend to bethe brainstorms of one guy Art is science before we know what were doing PHP beats your favorite language If we want to fix security, here is a good place towork

46. Whats Wrong With ORMs? Object Relational Models Problems with SQL Injection? Dont use SQL!Instead, the database just looks like your favoritelanguages native objects. Great, right up until the moment you need to makea query.

47. Look at this. It matters. +[,+[-[>+>+>++++++++[-]>>+[-] ++[-]+[[-]++++++++[-]>++++[-]>+[-][-]< +[-]+ +[-]+[[-]+[-]++[-]< [>+[[-]< select($name); 32 characters of punctuation, deeply interspersed $result = query(SELECT $name FROM $names WHERElength($name)prepare(SELECT * FROM foo where x=? andy=?);$stmt->bind_param(ss, $x, $y);$stmt->execute(); Finally, evaluate the generated code eval(b(SELECT * FROM foo where x=^^x and y=^^y); Eval is, surprisingly, the only way to retrieve the values of $xand $y from inside the function b().

53. Whats Wrong With Interpolique? What if the dev writes: eval(b(SELECT * FROM foo where x=$x andy=$y); If $x and $y are attacker controlled, hes not farfrom an eval that will run code in PHPs context! The b() function is in a position to defend the codethat ultimately enters eval, but now youre entirelydependent on b() knowing what PHP will do givenarbitrary bytes. GOOD LUCK WITH THAT Highly greppable error case, but its pretty scary

54. Building A Safe Interpolique Eval only exists so that variables from the callingscope can be dereferenced One approach is to implementcreate_selfscoped_function() Returns a function that always runs in the scope of itsparent Could implement proxies so it can only read variables,and cant rewrite $rows=$mysql_safequery(select * from foo wherex=^^x and y=^^y); Requires a patch to PHP -- Daniel Zulla is working onthis!

55. Code Rewriting? If we know what we would have liked developers to have written, why dont we just transform code once? Never really been a fan of this Have you ever audited autogenerated code? What do you do when the code looks like:$z = SELECT * from foo where x=$x and y=$y;;$rows = mysql_query($z); Static analysis can of course find such situations (thusknowing $x came in from a HTTP variable) but mostdevs dont have access to such static analysis tools Should they?

56. Tainting What if we actually marked every character that came in from anHTTP query as tainted? Metadata, on a character by character basis Would survive passing from function to function Might even survive reasonable mangling by built in filters Then, you could write something like:mysql_query_safe(select * from foo where x=$x and y=$y;); Even though $x and $y would expand, the wrapper functionwould see that those particular characters were once tainted withthe mark of the web, and could rewrite the unsafe query aroundit This still works with mysql_query_safe($x) when $x wasassembled elsewhere, even concatenated; Could have problems with silent failure with filtering functions Requires a patch to PHP Daniel Zulla also working on this

57. SuperEncoding as Explicit Tainting Based on discussions with Zane Lackey and Nick Galbreath atEtsy, based on an approach theyre already running inproduction What if all variables from the web, were encoded in a whitelistedformat? Simple hex encoding -- &%41 which, coincidentally, renders asan A in any HTML parser All non-DB access would have to go through accessors r($x) to read, w($x) to write Surprisingly easy to grep for access that isnt wrapped Could do two things mysql_query_safe($x) could simply treat all superencodedcharacters as data and parameterize accordingly mysql itself could have its lexer modified to handle HTMLencoding, exposing such characters to less of the SQL parser(this is just a string) very LangSec

58. A Last Minute Alternative Perhaps weve got this backwards Rather than tainting data as data, we mark code as code. SQL tends not to be passed around from function to function, letalone parsed in the frontend $sql = c(select * from foo where x=);$sql += $x;$sql += c(and y =);$sql += $y; Then either mysql_query_safe or mysql itself (cowardly) refusesto execute anything with unmarked code Or, if this is baked into MySQL, it just doesnt see bytes as code if theyre not deeply marked as code Moderately greppable youre basically finding all SQL in yourcode and wrapping it with some sort of taint Either implicit as per Zulla, or explicit as per Etsy Most likely failure mode is an attacker controlled variable somehow getting inside of c();

59. This is what LangSec means What are people trying to say? How can we make it easier to say that? How hard will it be for people to migrate? What errors will they make when trying to usethis? Can we limit how much code might contain abug? CARE ABOUT YOUR DEVS OR THEY WILLNOT CARE ABOUT YOU

60. Whats Going On With The Web? It doesnt matter what code you write, if there areparties in the middle changing or blocking whatyou send Content alteration and blocking is becoming areal thing Verizon is claiming the first amendment right torewrite Internet connections Entire countries are silently blocking web pages Indonesias blocking a million porn sites in the run up toRamadan

61. What Went Wrong With N00ter N00ter was a really fun (and really powerful) mechanismfor detecting network manipulation Allowed a remote server and a cooperating client to pretendto have a conversation with anyone on the Internet, using anyprotocol To any MITM, it would look like a real, unmodifiedconversation So any alterations that might normally hit the real server, would hit this too Unfortunately, N00ter does a lot of very low levelpacketcrafting, meaning (realistically) it requires customhardware in front of user machines This is not fun to deploy Especially if you need to get between NAT and actual networkconnection Not impossible. Definitely improbable.

62. What Else Can We Use? Executable code on the client OONI-Probe Web Pages with Iframes Herdict (Herd Verdict) Needs either user cooperation, or a Chrome extension, to know if content is up or down Is it possible to determine whether content is up or not, from just a web page? Can we crowdsource censorship data? Maximize data per user Minimize installation load per user

63. Imaging Browsers Same Origin Policy usually prevents webpages from doing much with one another You wouldnt want Yahoo able to read from your Gmailaccount But there is one exception Any domain is allowed to load any other domainsimages Beyond that, its allowed to know that the load wassuccessful Not merely that there was a file at that location, but that it wasactually an image You even get image dimensions (which youd have to, becauseit resizes the page) If a domain is being censored, the image will not load What one image is on most domains?

64. Favicon.ico (Its the picture to the left of Google in the tab)

65. So this is CensorSweeper(Also by Joseph Van Geffen and Michael Tiffany)Written for Wall Street Journal Data Transparency Hackathon

66. Whats going on img = new Image();img.onload = function(event) { }// render faviconimg.onerror = function(event) { validate(); }img.src = http://somesite.com/favicon.ico The above is done in parallel, reading from a listof sites that have confirmed presence offavicon.ico Six failures are required before a bomb isdropped on the map

67. Error Handling Six failures isnt actually enough! Web browsers provide remarkably little feedback to adeveloper to know whats failing, and why Put simply, flow control hasnt really been implementedfor the web Everythings been designed around infinite bandwidth For reliability, going to need to shut down all othertraffic, and then do two simultaneous lookups One for a known-up site, the other for the supposedly-down site That being said, CensorSweeper works pretty well Can we do better?

68. Sockets Once upon a time, web browsers could act like proxies, giving you connections anywhere There were bugs in Flash and Java; we fixed them They can now only create connections to IP addresses that invite them But ~20% of the time there are transparent proxies between web servers and their users See Staring into the Abyss by me, or Socket Capable Browser Plugins Result In Transparent Proxy Abuse by Bob Augur This has been knownbut not explored for mapping censorship!

69. HTTP Censorship Detection 1) Using Flash (or HaXe) Create a HTTP connection back to your own IP on port 80 Host a socket policy file, so Flash allows this 2) Request anything, from any domain If the request comes to you, there is no transparentproxy Otherwise, the request will be hijacked by the proxy,serviced, and sent back to your Flash app You now see what that user would see, if theybrowsed to that site! You can then submit it back toyourself.

70. HTTPS Certificate Extraction Just as HTTP traffic on 80/tcp is hijacked, so may HTTPStraffic on 443/tcp MITM may have an alternate certificate for you But (if youre careful) it cant tell the difference between thebrowser starting SSL, and Flash/HaXe starting SSL It has to know which domain to pretend to have a certificate for The proxy can parse the Server Hello, with its certificate (Its your server saying hello) The proxy can parse the Client Hello, with its Server Name Indication (Its your Flash app saying hello) You can actually host the real Facebook certificate, or even proxy thereal Facebook SSL endpoint Hard to keep track of all of Facebooks IPs It has to forge the certificate, before you have to prove you actually have Facebooks private key (assuming you arent proxying)

71. Slight Annoyance No normal way, via Browser DOM, to determine thecertificate that provided content This at least allows a page to query for its exposedcertificates kinda cool! Limitations You can test anyones certificate, as long as the attackerisnt interposing themselves via DNS hijacking The Flash app sees whats at the named IP; if hijacking is atthe DNS layer, then Flash wont get hijacked You are able to test your own certificate, but then theattacker has already MITMd you and can alter yoursecurity validation layer

72. Full Proxying One of the goals of N00ter was seeing if everyday content wasbeing altered or slowed down One of the headaches with these custom probes is writing thesecustom probes How do you look just like a real web browser trying to accessYouTube? Answer: Be a real web browser trying to access YouTube The last time we played with Flash and Sockets, we created afull VPN But now sockets are limited to a single destination It turns out that it may still be possible/useful to proxy an entirebrowser (at the server) down to the Flash app (in the client),which will then make open connections back to the server whowill proxy them to the rest of the Internet This will allow, at minimum, a protocol correct sequence ofmessages for HTTP and HTTPS that are only incorrect bydestination IP So basically, if the intercepting server doesnt care about IP correctness, you get to interrogate its ruleset with no installed code on the client

73. Last but not least:Scanning Networks Quickly Actionable Intelligence: What can an attacker dotoday, that he couldnt do yesterday, for what classattacker, to what class victim? Rather related to this: How many potential victims areout there? Ive run two major scans this year (that Ive talkedabout) Telnet Determining presence of Telnet Encryption support Answer: Very rare RDP Determining presence of open RDP access Answer: VERY common

74. My Process Once upon a time, simply flooding TCP SYNswas enough to find out what was out there Nowadays, many, many IP addresses will threeway handshake, but there wont actually beanything there Solution: Split process 1) Identify candidate IP addresses, that are listeningon a given port 2) Given a candidate, actually connect to the IP

75. More Detail Candidate collection For each IP, incrementing the first bytefirst, (1.1.1.1, 2.1.1.1, 3.1.1.1), send a TCP SYNon the required port (23 for telnet, 3389 for RDP) In a separate window, log TCP SYN|ACKs withtcpdump tcpdump w log tcp[tcpflags] = (tcp-syn|tcp-ack) Scanrand was being buggy, this maximized logging Candidate Inspection Telnet Encryption nmap team whipped up a quickcheck, so I just fed the IP list to it Very few found

76. RDP Sweep: Black Mamba Probably the most pleasant environment for reasonable scale TCPprobing ever devised http://rootfoo.org/blackmamba from blackmamba import *def get(host, port=80):msg = "GET / HTTP/1.1rnHost: %srnrn" % hostyield connect(host, port)yield write(msg)response = yield read()yield close()print responsedef generate(host, count=100):for i in range(count):yield get(example.com)run(generate(example.com)) You end up getting ~3000 IPs a second May need to increase ulimit n May need to alter hardcoded limits in blackmamba.py

77. Can We Get Faster? Always wanted to write a userspace TCP stack HD Moore kinda kicked me into working on one for critical.io,his mysterious new scanning project I am not at all beyond being motivated by other peoples awesomeand mysterious projects Especially when they give me CPU and Network Bandwidth So. Scanrand3! A new scanner that doesnt just flood SYNs,but actually connects to every node and extracts data Original plan: TCP stack with SQLite as the backend SELECT * FROM sockets WHERE data_sent!=data_ackedand data_sent_time-now()>3 (to find sockets where aretransmit is needed) is just funny! SQLite, in memory-only mode, is really really fast 160K inserts/sec fast Unfortunately, that speed disappears when you add indexes 20K inserts/sec with two indexes

78. New Plan: Let The Servers KeepTCP State

79. Details! Details! Scanrand didnt get its speed by keeping track of who it didor didnt send traffic to Why should Scanrand3? 1) Send SYN Maximum Segment Size==1460 Window Size==1460 (for all packets) 2) Upon receiving a SYN|ACK, reply with an ACK Include GET / HTTP/1.0 payload Yes, you can put a payload in the initial ACK! 3) Upon receiving an ACK, if there is a payload, ACK it Save the payload 4) Upon receiving a FIN|ACK, RST Save the payload, if any

80. No Local State If the first SYN is dropped OK, nobodys around toretransmit it May want to log RST|ACK to avoid future retransmits If the SYN|ACK is dropped to the client, serverretransmits SYN|ACK If the ACK w/ initial payload is dropped to the server,server retransmits SYN|ACK, causing new ACK w/payload If any ACK w/ response payload is dropped to theclient, server will retransmit ACK w/ response payload Same with FIN|ACK Window size of 1460 means we always know whichparticular packet to acknowledge only one in flight(usually)

81. Performance Relatively unoptimized code on a well hosted butunderpowered server (cheap Dual Opteron) 50-80K servers/sec w/ full payloads 3.25M IPs takes 60-80 seconds, retrieves about800MB of content Task is embarrassingly parallelizable acrossthreads, databases, etc. Should be able to use multiple bpf filters to route packetsto their appropriate thread with kernel filtering Writing to a SQLite DB, and then backing up to disk, isreally fast (substantially faster than fwrite, thoughhavent tested a large mmap yet) You basically reassemble payloads in SQLite as apostprocess

82. Security Scanrand pioneered inverse SYN cookies you protectagainst spoofed responses by validating fields in theresponse against hashes of data plus a secret only youknow 16 bits in source port + 32 bits in sequence number arepossible May be able to get another 32 bits out of TCPTimestamps, which are usually supported Havent implemented yet, so very easy to poison me Sequence space becomes less secure, the more data youactually send You do know the exact size of each payload, so you can say I onlyaccept responses with no payload seq, payload 1 seq, payload 2seq, etc Technically the other said can ACK at any byte offset, but that doesntmean they actually will

83. Some Notes Kernels have actually gotten kind of fast Non-blocking connect() plus epoll should be able to get pretty fast Certainly easier to code for that model! Didnt work for me (not sure why) This approach ultimately becomes fastest Probably need a writev call to spew many packets w/o a write for each

84. More Notes Can also try more efficient stores than sqlite Giant allocation of RAM with fixed offsets per IP MemSQL Neat project by ex-facebookers compiles SQL to C++ They think even with the indexes they can do +100K Can have merged approaches too Only start keeping state if I like the response from the server Note that stateless client + stateless server = no retransmits

85. What should the coding model be? Flat file / command line? C? JavaScript? Lua? Could implement support for nmap scripts

86. Most Important Feature Blacklist support Most networks dont mind getting swept They certainly are, already Some do Part of being a whitehat is you let people know who you are,and listen to their requests So you end up with a pile of IP ranges not to sweep It can actually take a substantial amount of CPU if youcheck the list naively Need to compile it into a quickly queriable structure I dont think firewall rules apply to spoofed traffic

87. Simple Architectural Note Dont try to interact with the Linux firewall Just pick another IP on the LAN and send from their Respond to ARP traffic for it (Yes, it is an advantage of the socket model thatyou dont need to requisition another IP)

88. Whew! Lots of stuff! Hope you enjoyed! This may not be how you try to fix stuffbut itswhat I try to do Thanks to everyone cited in the slides Thanks also toNick, Johnny, Blackstock, Alex, Allessandra, Allessandra, and Andrew of The Sub for putting up with mein DEFCON mode ;)

Black ops 2012

Technology

bad news good news

big guys

secure code

talk good news

hundreds of years

reality of defense

attack doesnt work

fundamental difference