September 18th 2009 DNSSEC Restoring trust in DNS Roland van Rijswijk roland.vanrijswijk [at] surfnet.nl In cooperation with:

About us SURFnet. We make innovation work1 High quality and high bandwith network for higher education and research Shared ICT innovation centre for academia Over 180 connected institutions (universities, polytechnics, vocational education, hospitals, research institutions) with 1 million end-users Independent consultancy company Cryptography expertise Internet security expertise

SURFnet. We make innovation work2 Overview -First half: -Attacks on DNS -Second half: -DNSSEC in detail -Questions: please ask!

SURFnet. We make innovation work3 DNS: Roadsigns for the net

SURFnet. We make innovation work4 DNS: insecurity by design? -DNS was designed in the early Internet era -Everybody more or less knew everybody else -And everybody trusted everybody else -Bottom line: Security was not a design criterion

SURFnet. We make innovation work5 Threats to DNS -Availability -If DNS is not available, the internet is broken (users think) -A typical DNS resolver services end users -Some authoritative servers host over 8 million zones -Exploitation -On an exploited server availability and integrity are broken -Plus the attacker can gain access to all other software on the same server/client -Integrity -DNS gives the wrong answer and sends you the wrong way Slide content courtesy of Bert Hubert (PowerDNS)

SURFnet. We make innovation work6 Why attack DNS? -DNS is everywhere: -In your phone, in your laptop, in your PC… -But also in your car, in an ATM, in your elevator, … -It is very hard to protect DNS against attacks (currently) -It is very easy to attack a lot of users

A: Let’s start simple A? Referral to auth. A: A? Question: name a general attack model that is applicable to this setup Answer: a man in the middle attack

Beyond M-i-t-M: spoofing IPheaders & stuff src IP = (ns1.surfnet.nl) dst IP = ( UDPsrc port = 53dst port = 4321 headers & stuff DNSQID = 1201some flags Question# = 1Answer# = 1 Authority# = 3Add. record# = 3 Q?A record for Ans. = Aut.surfnet.nl = ns1.surfnet.nl Aut.surfnet.nl = ns2.surfnet.nl Aut.surfnet.nl = ns3.surfnet.nl Add.ns1.surfnet.nl = Add.ns2.surfnet.nl = Add.ns3.surfnet.nl =

A: Cache poisoning A? Referral to auth. A: A? Question: how can I target a specific name? Answer: introduce a rogue client

SURFnet. We make innovation work10 So where do we go today? ;-)

SURFnet. We make innovation work11 Is it really a threat? Yes because: -Source port randomisation was not common practice before Kaminsky -Query ID randomisation wasn’t common practice either No because: -You can only attempt to poison a name a few times per day (why?)

SURFnet. We make innovation work12 Cache poisoning++ -Dan Kaminsky published an attack at last year’s Black Hat conference -No need to wait for a resolver to take initiative, no need to wait for TTL expiry…

Preparing for Kaminsky IPheaders & stuff src IP = (ns1.surfnet.nl) dst IP = ( UDPsrc port = 53dst port = 4321 headers & stuff DNSQID = 1201some flags Question# = 1Answer# = 1 Authority# = 3Add. record# = 3 Q?A record for Ans. = Aut.surfnet.nl = ns1.surfnet.nl Aut.surfnet.nl = ns2.surfnet.nl Aut.surfnet.nl = ns3.surfnet.nl Add.ns1.surfnet.nl = Add.ns2.surfnet.nl = Add.ns3.surfnet.nl =

Attack in action piggybank.dom A: piggybank.dom A??? QID= piggybank.dom A??? QID=1235 QID=1233 QID=1234 QID=1235 Success! Additional: NS piggybank.dom go to piggybank auth piggybank.dom A???

SURFnet. We make innovation work15 Spoofed additional section ;; QUESTION SECTION: ;abcde.piggybank.dom. IN A ;; ANSWER SECTION: abcde.piggybank.dom. 582 IN A ;; AUTHORITY SECTION: piggybank.dom IN NS ns1.piggybank.dom. piggybank.dom IN NS ns2.piggybank.dom. ;; ADDITIONAL SECTION: ns1.piggybank.dom IN A ns2.piggybank.dom IN A

Attack in action A? A: A:

SURFnet. We make innovation work17 So it’s even worse!

Impact on threat level (1) -Kaminsky is happening (we think, but is damn hard to detect): -Wide-scale patching has been rolled out -But research shows: Poisoning unpatched BIND: ±3 seconds Poisoning patched BIND: 1-11 hours (source: NIC.cz) SURFnet. We make innovation work18

Impact on threat level (2) -Kaminsky is happening on our network! SURFnet. We make innovation work19

Impact on threat level (3) SURFnet. We make innovation work20 -Kaminsky is happening on our network!

Impact on threat level (4) SURFnet. We make innovation work21 -Kaminsky is happening on our network!

SURFnet. We make innovation work22 The slow attack -Brute force attacks are easy to detect -But the slow attack is very insidious… research by Bert Hubert (PowerDNS) shows: Graph courtesy of Bert Hubert

Summary

Break time

SURFnet. We make innovation work25 What is DNSSEC?(1) -DNSSEC is an extension to DNS specified by the IETF in a number of RFCs -Actively developed since According to RFC 4033: “ The Domain Name System Security Extensions (DNSSEC) add data origin authentication and data integrity to the Domain Name System.”

SURFnet. We make innovation work26 What is DNSSEC?(2) -DNSSEC makes it possible to check the authenticity of DNS records -This is accomplished using public key cryptography -What DNSSEC does not do: -Provide confidentiality -Protect against threats to the name server (DDoS, etc.) -Guarantee correctness of the DNS data (only authenticity) -Protect against phishing, typosquatting, etc.

SURFnet. We make innovation work27 Cryptography in DNSSEC (1) -Public key cryptography -RSA, DSA, (Elliptic Curve) -All based on a common principle: the key- pair -Private Key is used to sign well protected, hidden from outsiders -Public Key is used to verify must be widely published

SURFnet. We make innovation work28 Cryptography in DNSSEC (2) -Signing takes place at zone level -2-tiered key model: -Key Signing Key -Large key size (≥ 2048 bits RSA) -Long validity (≥ 1 year) -Used to sign Zone Signing Key -Zone Signing Key -Smaller key size (≥ 1024 bits RSA) -Short validity (± 1 month) -Used to sign the zone (resource records)

SURFnet. We make innovation work29 Signing DNS zones -Additional resource records (RRs) -For public keys: -DNSKEY, DS -For signatures: -RRSIG -For authenticated denial-of-existence: -NSEC, NSEC3 -Zones become quite a bit larger

SURFnet. We make innovation work30 Validating a response  Query  INAwww.nist.gov  INRRSIG A10 623C49E8D53CF7E6046E F  signature! -Validate this signature against the “nist.gov” zone public zone signing key -It’s the resolver’s job to do this! -How do I find and trust the “nist.gov” key?

SURFnet. We make innovation work31 Current deployment -Deployed on several TLDs: -ccTLD’s:.bg,.br,.cz,.pr,.se -generic TLD’s:.org,.gov,.museum -Announced for more TLDs: -generic TLD’s:.com and.net (2011) (> 65% of all domains!) -Good news: root is likely to be signed before end of 2009 (bad news: politics…) -Many (cc)TLD’s still to announce strategy

Trust chain

SURFnet. We make innovation work33 Islands of trust

SURFnet. We make innovation work34 Finding trust anchors -Managing trust anchors by hand is hard work -IANA has made the “Interim Trust Anchor Repository” (ITAR) available -ISC has introduced “DNSSEC look-a-side validation” (DLV) and made a repository available -No standard way to trust the trust anchors of these repositories -These are interim solutions

DLV

SURFnet. We make innovation work36 Key management(1) -Key Signing Key and Zone Signing Key have a limited validity; this requires regular roll-overs:

SURFnet. We make innovation work37 Key management (2) -Keys need to be stored securely  off-line, smart card, Hardware Security Module (HSM),... -Administrators need to plan for emergency key roll-over -The parent has to be notified of new keys for a domain (this needs to be automated)

SURFnet. We make innovation work38 Future

SURFnet. We make innovation work39 Criticism on DNSSEC The Top-10 Reasons Why DNSSEC Is the String Theory of the Internet 10. Adds many new dimensions to an already complex problem 9. Hogs all the research funds 8. Has many careers riding on it 7. Widely hailed by expert and layman alike as the next big thing 6. Responds to shortcomings by reinventing itself and doubling its complexity 5. On its third iteration to succes 4. Attracts the brightest minds of the industry 3. Cult-like following among believers 2. Always on the verge of solving a real world problem 1. Will be ready in 6 months! Bert Hubert (PowerDNS) -Even the critics agree that DNSSEC is the only available solution at the moment -That doesn’t mean that DNSSEC is perfect… far from it -DNSSEC is hard (especially compared to ‘ordinary’ DNS, which is very forgiving) -The (un)availability of easy-to-use tools is hindering deployment of signed zones

SURFnet. We make innovation work40 DNSSEC software -But there is light on the tool horizon: -OpenDNSSEC ( -Secure64 DNS Signer -Xelerance DNSX Signer -ZKT (Zone Key Tool, -PowerDNS + DNSSEC = PowerDNSSEC -other vendors have announced products -For resolvers it’s a different matter, tools are widely available: -Unbound (by NLnetLabs) -BIND 9.x and up -Windows Server announced (2008 R2, Server 7)

SURFnet. We make innovation work41 Alternatives(1) -Continue patching against attacks (keep using traditional DNS) -This is an arms race -The race is already being lost! (remember the 6 weeks attack that Bert Hubert talked about yesterday) -SSL/TLS -Too heavyweight to use on connections to DNS servers -Does not secure a domain against cache-poisoning; getting an SSL certificate is easy

SURFnet. We make innovation work42 Alternatives(2) -TSIG/SIG(0) -TSIG is based on shared secrets (does not scale) -SIG(0) secures transactions (no authentication of records!) -DNScurve -Based on elliptic curve crypto -Can do much more than DNSSEC -Only proves authenticity online (forwarder based) -No widescale deployment/support

SURFnet. We make innovation work43 Alternatives(3) -DNS 0x20 -Based on using capitalisation to introduce extra entropy into a query -Capitalise parts of the query at random and check that the capitalisation in the answer matches the query -Should be compatible with existing DNS infrastructure (RFC 4343) -But depends on all name server software to implement literal query copying (most do) -Criticism: it’s still an arms race -And it doesn’t protect ‘.’

SURFnet. We make innovation work44 Summary -What does DNSSEC do for you? -You can prove the authenticity of the records in your domain -You can check the authenticity of the records of others -You effectively protect yourself against attacks like Kaminsky’s

SURFnet. We make innovation work45 What have we done? -SURFnet’s resolvers perform DNSSEC validation:

SURFnet. We make innovation work46 What are we going to do? -Extend our managed DNS service with DNSSEC support -Testing DNSSEC appliances as they appear on the market -Keep supporting OpenDNSSEC -Give talks like this one :-)

SURFnet. We make innovation work47 What can you do? -Gather knowledge on DNSSEC -SURFnet DNSSEC white paper ( -Available at the end of this class -Update/reconfigure your resolvers to support DNSSEC validation and experiment with it -Work on an open source tool project! -Go to the OpenDNSSEC website and test the software

SURFnet. We make innovation work48 Questions? Thank you for your attention! Roland van Rijswijk roland.vanrijswijk [at] surfnet.nl Rick van Rein rick [at] openfortress.nl Presentation released under Creative Commons (

Lab work -You are going to perform the Kaminsky attack -Install BIND as a resolver -Download the code IMPORTANT: The code is provided under embargo, please discard it after the lab work is done -We’d like you to finish with a short presentation of your findings

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