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DNSSEC Tutorial, by Champika Wijayatunga [APNIC 38]
This document provides an overview of DNSSEC (Domain Name System Security Extensions). It discusses how DNSSEC introduces digital signatures to cryptographically protect DNS data and prevent man-in-the-middle attacks. It also describes some common DNS record types used in DNSSEC like DNSKEY, RRSIG, and DS. The document notes that while DNSSEC deployment has increased in top-level domains and root servers, adoption remains low at the second-level domain level, and more work is still needed for full deployment.
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DNSSEC Tutorial, by Champika Wijayatunga [APNIC 38]
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- 2. Acknowledgements • Rick Lamb – Senior Program Manager, DNSSEC @ICANN • APNIC Training
- 3. DNS Basics •DNS converts names (www.icann.org) to numbers (192.0.32.7) • ..to idenOfy services such as www and e-‐mail • ..that idenOfy and link customers to business and visa versa
- 4. Reminder: DNS Resolving Question: www.example.net A 1" 2" www.example.net A ? Resolver www.example.net A ? Caching forwarder (recursive) “go ask net server @ X.gtld-servers.net” (+ glue) gtld-server www.example.net A ? “go ask ripe server @ ns.example.net” (+ glue) www.example.net A ? example-server “x.y.z.1” x.y.z.1 3" 4" 5" 6" 7" 9" 8" Add to cache 10" TTL root-server
- 5. DNS: Data Flow master Caching forwarder Zone administrator Zone file Dynamic updates 1" 2" 3" slaves 4" 5" resolver
- 6. DNS VulnerabiliOes Corruptingdata" Impersonating master" Cache impersonation" master Caching forwarder Zone administrator Zone file Dynamic updates 1" 2" 3" slaves 4" 5" resolver Unauthorized updates" Cache pollution by" Data spoofing" Server protection! Data protection!
- 7. +1-‐202-‐709-‐5262 VoIP US-‐NSTIC effort DNS is a part of all IT ecosystems lamb@xtcn.com mydomainname.com Smart Electrical Grid OECS ID effort
- 8. Where DNSSEC fits in • ..but CPU and bandwidth advances make legacy DNS vulnerable to MITM aWacks • DNS Security Extensions (DNSSEC) introduces digital signatures into DNS to cryptographically protect contents • With DNSSEC fully deployed a business can be sure a customer gets un-‐modified data (and visa versa)
- 9. The Bad: DNSChanger -‐ ‘Biggest Cybercriminal Takedown in History’ – 4M machines, 100 countries, $14M Nov 2011 h[p://krebsonsecurity.com/2011/11/malware-‐click-‐fraud-‐kingpins-‐arrested-‐in-‐estonia/ End-‐2-‐end DNSSEC valida_on would have avoided the problems
- 10. The Internet’s Phone Book -‐ Domain Name System (DNS) www.majorbank.se=? Get page webserver www @ 1.2.3.4 Username / Password Account Data DNS Hierarchy DNS Resolver root se com majorbank.se www.majorbank.se www.majorbank.se = 1.2.3.4 DNS 1.2.3.4 Server Login page ISP Majorbank (Registrant)
- 11. Caching Responses for Efficiency www.majorbank.se=? Get page webserver www @ 1.2.3.4 Username / Password Account Data DNS Resolver www.majorbank.se = 1.2.3.4 DNS 1.2.3.4 Server Login page
- 12. The Problem: DNS Cache Poisoning AWack www.majorbank.se=? DNS Resolver www.majorbank.se = 1.2.3.4 DNS 5.6.7.8 Server Get page Attacker webserver www @ 5.6.7.8 Username / Password Error Attacker www.majorbank.se = 5.6.7.8 Login page Password database
- 13. Argghh! Now all ISP customers get sent to aWacker. www.majorbank.se=? DNS Resolver www.majorbank.se = 1.2.3.4 DNS 5.6.7.8 Server Get page Attacker webserver www @ 5.6.7.8 Login page Username / Password Error Password database
- 14. Securing The Phone Book -‐ DNS Security Extensions (DNSSEC) www.majorbank.se=? DNS Resolver with DNSSEC Attacker’s record does not validate – drop it www.majorbank.se = 1.2.3.4 DNS Server with DNSSEC 1.2.3.4 Get page webserver www @ 1.2.3.4 Login page Username / Password Account Data Attacker www.majorbank.se = 5.6.7.8
- 15. Resolver only caches validated records www.majorbank.se=? DNS Resolver with DNSSEC www.majorbank.se = 1.2.3.4 DNS Server with DNSSEC 1.2.3.4 Get page webserver www @ 1.2.3.4 Login page Username / Password Account Data
- 16. The Bad: Other DNS hijacks* • 25 Dec 2010 -‐ Russian e-‐Payment Giant ChronoPay Hacked • 18 Dec 2009 – Twi[er – “Iranian cyber army” • 13 Aug 2010 -‐ Chinese gmail phishing a[ack • 25 Dec 2010 Tunisia DNS Hijack • 2009-‐2012 google.* – April 28 2009 Google Puerto Rico sites redirected in DNS a[ack – May 9 2009 Morocco temporarily seize Google domain name • 9 Sep 2011 -‐ Diginotar cer_ficate compromise for Iranian users • SSL / TLS doesn't tell you if you've been sent to the correct site, it only tells you if the DNS matches the name in the cer_ficate. Unfortunately, majority of Web site cer_ficates rely on DNS to validate iden_ty. • DNS is relied on for unexpected things though insecure. *A Brief History of DNS Hijacking -‐ Google h[p://costarica43.icann.org/mee_ngs/sanjose2012/presenta_on-‐dns-‐hijackings-‐marquis-‐boire-‐12mar12-‐en.pdf
- 17. The Business Case for DNSSEC • Cyber security is becoming a greater concern to enterprises, government, and end users. DNSSEC is a key tool and differenOator. • DNSSEC is the biggest security upgrade to Internet infrastructure in over 20 years. It is a pla`orm for new security applicaOons (for those that see the opportunity). • DNSSEC infrastructure deployment has been brisk but requires experOse. Gecng ahead of the curve is a compeOOve advantage.
- 18. • DNSSEC -‐ Where we are Deployed on 462/654 TLDs (29 July 2014 70% .com .hr .es .in .af .ee .lb .bg .tm .cz .nl .uk .de .jp .cn .ru .р ф .my مليسيا .asia .tw 台灣, .kr 한국 .net, .org, .post, +gtlds) • Root signed** and audited • Required in new gTLDs. Basic support by ICANN registrars • Growing ISP support*. • 3rd party signing soluOons*** • Growing S/W H/W support: NLNetLabs, ISC, Microsop, PowerDNS, Secure64…? openssl, pos`ix, XMPP, mozilla: early DANE support • IETF standard on DNSSEC SSL cerOficates (RFC6698) • Growing support from major players…(Apple iPhone/iPad, Google 8.8.8.8,…) * COMCAST /w 20M and others; most ISPs in SE ,CZ. AND ~12% of resolvers validate using DNSSEC **Int’l bo[om-‐up trust model /w 21 TCRs from: TT, BF, RU, CN, US, SE, NL, UG, BR, Benin, PT, NP, Mauri_us, CZ, CA, JP, UK, NZ… *** Par_al list of registrars: h[ps://www.icann.org/en/news/in-‐focus/dnssec/deployment
- 19. But… • But deployed on ~1-‐2% (3.5M) of 2nd level domains. Many have plans. Few have taken the step (e.g., yandex.com, paypal.com*, comcast.com). • DNSChanger and other aWacks highlight today’s need. (e.g end-‐2-‐end DNSSEC validaOon would have avoided the problems) • InnovaOve security soluOons (e.g., DANE) highlight tomorrow’s value. * h[p://fedv6-‐deployment.antd.nist.gov/cgi-‐bin/generate-‐com h[p://www.thesecurityprac_ce.com/ the_security_prac_ce/2011/12/all-‐paypal-‐domains-‐are-‐now-‐using-‐dnssec.html h[p://www.nacion.com/2012-‐03-‐15/Tecnologia/Si_os-‐web-‐de-‐bancos-‐_cos-‐podran-‐ser-‐mas-‐seguros.aspx
- 20. DNSSEC: So what’s the problem? • Not enough IT departments know about it or are too busy pucng out other security fires. • When they do look into it they hear old stories of lack of turnkey soluOons. • Registrars*/DNS providers see no demand leading to “chicken-‐and-‐egg” problems. *but required by new ICANN registrar agreement
- 21. Too many CAs. Which one can we trust? DNSSEC to the rescue…. CA CerOficate roots ~1482 DNSSEC root -‐ 1 Login security SSHFP RFC4255 Content security Commercial SSL CerOficates for Web and e-‐mail DANE and other yet to be discovered security innovaOons, enhancements, and synergies Content security “Free SSL” cerOficates for Web and e-‐mail and “trust agility” Network security IPSECKEY RFC4025 Cross-‐ organizaOonal and trans-‐naOonal idenOty and authenOcaOon E-‐mail security DKIM RFC4871 Securing VoIP Domain Names hWps://www.eff.org/observatory hWp://royal.pingdom.com/2011/01/12/internet-‐2010-‐in-‐numbers/
- 22. • For What you can do Companies: – Sign your corporate domain names – Just turn on validaOon on corporate DNS resolvers • For Users: – Ask ISP to turn on validaOon on their DNS resolvers • For All: – Take advantage of organizaOons offering DNSSEC educaOon and training
- 23.
- 24. DNSSEC Resource Records • 3 Public key crypto related RRs – RRSIG = Signature over RRset made using private key – DNSKEY = Public key, needed for verifying a RRSIG – DS = DelegaOon Signer; ‘Pointer’ for building chains of authenOcaOon • One RR for internal consistency – NSEC = Next Secure; indicates which name is the next one in the zone and which typecodes are available for the current name • authenOcated non-‐existence of data RFC 4034
- 25. DNSKEY • Contains the zone’s public key • Uses public key cryptography to sign and authenOcate DNS resource record sets (RRsets). • Example: myzone.net. IN DNSKEY 256 3 5 ( AwEAAagrVFd9xyFMQRjO4DlkL0dgUCtogviS+FG9Z6Au3h1ERe4EIi3L X49Ce1OFahdR2wPZyVeDvH6X4qlLnMQJsd7oFi4S9Ng+hLkgpm/n+otE kKiXGZzZn4vW0okuC0hHG2XU5zJhkct73FZzbmBvGxpF4svo5PPWZqVb H48T5Y/9 ) ; key id = 3510 Public key (base64)
- 26. RRSIG • The private part of the key-‐pair is used to sign the resource record set (RRset) per zone • The digital signature per RRset is saved in an RRSIG record myzone.net. 86400 NS ns.myzone.net. 86400 NS ns.yourzone.net. 86400 RRSIG NS 5 2 86400 ( 20121202010528 20121102010528 3510 myzone.net. Y2J2+CVqQRjQvcWY256ffiw5mp0OQTQUF8vUHSHyUbbhmE56eJimqDh Xb8qwlFjl40kmlzmQC5CmgugBqjgLHZbuvSfd9+Ucwkxbwx3HonAPr3 +0HVqP8rSqGRqSq0VbR7LzNeaylBkumLDoriQxceV4z3d2jFv4ArnM= )
- 27. Types of Keys • Zone Signing Key (ZSK) – Sign the RRsets within the zone – Public key of ZSK is defined by a DNSKEY RR • Key Signing Key (KSK) – Signed the keys which includes ZSK and KSK and may also be used outside the zone • Using a single key or both keys is an operaOonal choice (RFC allows both methods)
- 28. NSEC Record example $ORIGIN myzone.net.! @!SOA …! ! !NS !NS.myzone.net.! ! !DNSKEY !…! ! !NSEC mailbox.myzone.net. SOA NS NSEC DNSKEY RRSIG! ! mailbox !A !192.168.10.2 !! ! ! !NSEC www.myzone.net. A NSEC RRSIG! WWW ! !A !192.168.10.3 !! ! ! !TXT !Public webserver! ! ! !NSEC myzone.net. A NSEC RRSIG TXT!
- 29. DelegaOon Signer (DS) • Establishes the chain of trust from parent to child zones • Found in the parent’s zone file • In this example, myzone.net has been delegated from .net. This is how it looks like in .net zone file myzone.net. IN NS ns1.myzone.net. NS ns2.myzone.net. IN DS 19996 5 1 ( CF96B018A496CD1A68EE7 C80A37EDFC6ABBF8175 ) IN DS 19996 5 2 ( 6927A531B0D89A7A4F13E11031 4C722EC156FF926D2052C7D8D70C50 14598CE9 )
- 30. DelegaOon Signer (DS) • DelegaOon Signer (DS) RR indicates that: – delegated zone is digitally signed – indicated key is used for the delegated zone • Parent is authoraOve for the DS of the childs zone – Not for the NS record delegaOng the childs zone! – DS should not be in the childs zone
- 31. DNSSEC ValidaOon •Recursive servers that are dnssec-‐enabled can validate signed zones • The AD bit in the message flag shows if validated • Other opOons if you don’t have a validaOng resolver – Use a validator add-‐on for your web browser • ex: hWps://www.dnssec-‐validator.cz/ – Online web tools • hWp://dnsviz.net/ • hWp://dnssec-‐debugger.verisignlabs.com/ – Use an open DNSSEC-‐validaOng resolver • Some open validaOng resolvers – DNS-‐OARC’s ODVR (link) • 149.20.64.20 (BIND9), 149.20.64.21 (Unbound) – Google Public DNS • 8.8.8.8 or 8.8.4.4
- 32. DNSSEC -‐ Secng up a Secure Zone • Enable DNSSEC in the configuraOon file (named.conf) dnssec-enable yes; dnssec-validation yes; • Create key pairs (KSK and ZSK) dnssec-keygen -a rsasha1 -b 1024 -n zone myzone.net • Publish your public key • Signing the zone • Update the config file – Modify the zone statement, replace with the signed zone file • Test with dig
- 33. Signing the Zone • Sign the zone using the secret keys: dnssec-signzone –o <zonename> -N INCREMENT -f <output-file> -k <KSKfile> <zonefile> <ZSKfile> dnssec-signzone –o myzone.net db.myzone.net Kmyzone.net.+005+33633 • Once you sign the zone a file with a .signed extension will be created – db.myzone.net.signed
- 34. TesOng with dig: an example dig @localhost www.apnic.net +dnssec +multiline
- 35. Pushing the DS record • The DS record must be published by the parent zone. • Contact the parent zone to communicate the KSK to them.
- 36. Ways to Deploy DNSSEC • As part of the DNS sopware used – Manual key management – Can be quite complex – For staOc environment – Some means of automaOon using • opOon commands and scripts • Use DNSSEC tools for BIND, NSD, PowerDNS, etc with a hardware security module (HSM) – Semi-‐automaOc – Good for dynamic environment • Using an external appliance – ‘dnssec-‐in-‐a-‐box’ – Fully HSM, OpenDNSSEC DNS Appliance automates key generaOon, signing and rollover
- 37. DNSSEC: Internet infrastructure upgrade to help address today’s needs and create tomorrow’s opportunity.
- 38.