DNSSEC Brought to you by ISC-BIND, SUNYCT, and: Nick Merante – SUNYIT Comp Sci SysAdmin Nick Gasparovich – SUNYIT Campus SysAdmin Paul Brennan – SUNYIT Student Assistant SysAdmin

Wait… I thought you were from SUNYIT?

DNSSEC TIMELINE

Selective Timeline of DNSSEC 1987 – DNS Ratified to replace hosts.txt 1990 – DNS Security Flaws Found 1997 – First try at DNSSEC - RFC – Second try at DNSSEC - RFC2535 BIND9 is first DNSSEC capable implementation 2005 – Finalized RFCs Published July 2008 – Kaminsky exploit announced July 2010 – Root signed August 2010 –.edu TLD is signed March 2011 –.com TLD is signed ARIN signed for Reverse DNS

DNS BASICS A refresher to get us all on the same page…

DNS Records DNS comprised of various resource record (RR) types Primary types: A – map hostnames to IP addresses MX – map a host or domain to a list of mail servers CNAME – specifies an alias for a host PTR – map a IP address to a host name NS – Specifies authoritative name servers for a zone SOA – Specifies authoritative information about a zone Primary name server Domain administrator Serial number Timers related to refreshing the zone DNSSEC will introduce several new record types

DNS Security Issues Original DNS specifications did not account for security DNS Spoofing No data integrity checks Anyone can answer a request intended for another name server Attacks against query ID numbers Cache Poisoning A result of DNS spoofing Trick a DNS server into caching false information Nodes querying this name server will obtain false cached data Consequences: Clients misdirected to alternate locations Compromise host-based authentication systems

DNSSEC CONCEPTS

4 Security Objectives of DNSSEC 1. Key Distribution 2. Origin Authentication 3. Data Integrity 4. Authenticated Denial of Existence

New Record Types DNSKEY Public side of Private/Public Keyset Key Signing Key Zone Signing Key RRSIG Signed Validation of Resource Record Set DS Delegation Signer Builds Chain of Trust NSEC/NSEC3 Certified Non-existence record

Traditional DNS Lookup (un-cached) Recursive DNS Server Client looking for: fang.cs.sunyct.edu Iterative calls edu sunyct cs fang cs sunyct edu root 1 8

DNS Lookup Under Attack Recursive DNS Server Client looking for: fang.cs.sunyct.edu Targeted by cache poisoning Iterative calls edu sunyct cs fang cs sunyct edu root 1 8

Keys Public/Private Keyset Private Key used to sign records Should be kept in a secure location (not on live DNS servers) Public Key used to check signatures Must be 512 to 4096 bits for DNSSEC Several Algorithms available Zone Signing Key used to sign zones Key Signing Key used to sign ZSK record Generally larger & more secure Cryptographic Digest of KSK is sent upstream DS Record Verifies Authority of KSK

Key Flow DS KSK ZSK ampere nagios logit (sunyct.edu) DS KSK ZSK fang yoshi spuds (cs.sunyct.edu) DS KSK ZSK maryann gilligan professor (island.sunyct.edu) (edu)

Chain of Trust / Tower of Authority Recursive DNS Server Client looking for: fang.cs.sunyct.edu Targeted by cache poisoning Iterative calls edu sunyct cs fang cs sunyct edu root Crushes you when your data is bad 1 8

Key Rollover Changing ZSK: Recommended monthly to quarterly Changing KSK Recommended annually Why Rollover Reduced window of key exposure ZSKs sign many records Keys become more vulnerable with use

NSEC/NSEC3 Comparison Presented as evidence of non-existence

ldns-walk of berkeley.edu

What’s all this RRSIG stuff? Key tag of signing key Date of signing Signature expiration Algorithm Starting TTL The signature itself

Gotchas DoS Danger Load Increase Signed zone can be 4x LARGER than unsigned Bigger record size = more network traffic Key Security Dynamic DNS = fail (Have to keep private keys loaded to resign, no support for that) Network Gear must support EDNS0 for UDP packets Performance!

IMPLEMENTATION

Our Test Environment 3 VM’s running OEL (sunyct.edu) 3 Hosts running FreeBSD (cs.sunyct.edu) BIND P2

BIND Versions/Restrictions We recommend using the most up-to-date version of your preferred DNS software Updates often pertain to security issues Preliminary DNSSEC support introduced in BIND 8.2 Recommended version of BIND 9.7 for all capabilities Windows Server 2003 has preliminary support Slave support only Must be activated in Registry Windows Server 2008 R2 has full support

Key Generation Specifies Key Type Algorithm Key Size Name Type Zone Name ZSK is default Smaller Key Size Key tag added

Signing the Zone NSEC3 Hex Salt ZoneZone File Generated Zone File

named.conf Edits – Authoritative Servers Add “dnssec-enable yes” to the options section For your first time signing, make sure you increment your serial number! After signing your zones, point to the new signed zones Same names as your old zone files, but with “.signed” appended

named.conf Edits – Recursive Servers To start validating results add: “dnssec-validation yes” You also need to get the KSK for root into your config. As of this presentation, it would look like this for BIND >= 9.7: managed-keys { "." initial-key "AwEAAagAIKlVZrpC6Ia7gEzahOR+9W29euxhJhVVLOyQbSEW0O8gcCjF FVQUTf6v58fLjwBd0YI0EzrAcQqBGCzh/RStIoO8g0NfnfL2MTJRkxoX bfDaUeVPQuYEhg37NZWAJQ9VnMVDxP/VHL496M/QZxkjf5/Efucp2gaD X6RS6CXpoY68LsvPVjR0ZSwzz1apAzvN9dlzEheX7ICJBBtuA6G3LQpz W5hOA2hzCTMjJPJ8LbqF6dsV6DoBQzgul0sGIcGOYl7OyQdXfZ57relS Qageu+ipAdTTJ25AsRTAoub8ONGcLmqrAmRLKBP1dfwhYB4N7knNnulq QxA+Uk1ihz0="; };

Determine Your DS Info Domain Digest Key Tag Algorithm and Digest Type Fields Key File Specify SHA1 Hash

Send Your Digest to EDUCAUSE

Key rotation - ZSK 1. Generate and publish new ZSK one TTL before planned rotation, but don’t sign the zone with it! 2. After TTL expiration, sign with new ZSK 1. Leave old DNSKEY record in zone for 1 TTL cycle 2. Allows cached signed records to be verified (Signatures created with old key need time to expire) Here’s one option: Have 3 ZSK’s in your zone. The previous, current and next. Your zones will always contain the necessary keys.

Key rotation - KSK 1. Generate and publish new KSK at least one TTL before planned rotation and sign ZSK records with both the old and the new keys. 2. Make sure you send your new DS record upstream! 3. After TTL expiration, remove the old DS record from your upstream provider and remove the old KSK from your zone files

VERIFICATION

Verification – dnsviz.net All ClearTrust Issue

DNSSEC Debugger – Verisign Labs Everything looks good This shows a problem with the keys

dig – Points of Interest DNS Server Name DNSSEC Enabled Search Host to query for Record Type ad flag = authenticated data (this means it’s been confirmed valid)

dig – Points of Interest aa flag = authoritative answer (if you’re querying the authoritative server, you won’t see the ad flag, just the aa flag)

QUESTIONS? Get a copy of the

References 7 Things You Should Know About DNSSEC Microsoft DNSSEC Deployment Guide DNSSEC Debugger – Verisign Labs DNSViz – DNS Visualization Tool Firefox DNSSEC Validator Plugin DNSSEC for Beginners DNSSEC Zone Key Tool DNSSEC in 6 Minutes DNSSEC Reference Card ISC Steps for setting up a validating server