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Champika WijayatungaRegional Security Engagement Manager – Asia Pacific

22-24 January 2018

DNS/DNSSEC WorkshopIn Collaboration with APNIC and HKIRC – Hong Kong

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DNSSEC

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DNS: Data Flow

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Primary Caching Servers

Resolvers

Zone administrator

Zone file

Dynamicupdates

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Secondaries

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DNS Vulnerabilities

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Primary Caching Servers

Resolver

Zone administrator

Zone file

Dynamicupdates

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Secondaries

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Server protection

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Corrupting data Impersonating master

Unauthorized updates

Cache impersonation

Cache pollution byData spoofing

Data protection

Altered zone data

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The Bad

• Cache Poisoning Attacks– Vulnerable resolvers add malicious data to local caches

• DNS Hijacking– A man in the middle (MITM) or spoofing attack intercept and forwards

DNS queries to a name server that returns forge responses– e.g. DNSChanger (One of the biggest cybercriminal takedown in

history)• Many other DNS hijacks in recent times• 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 certificate.

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How DNSSEC Works

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Why DNSSEC?

Without DNSSEC

DNS

DNSmyexamplebank.com

IP address X

myexamplebank..com webserver

Attacker’s

webserver

myexamplebank.com= IP address A

myexamplebank.com= Attacker IP address X

Attacker’s page

Passwords

DNS

DNSmyexamplebank.com

IP address A

myexamplebank.comwebserver

myexamplebank.com= IP address A

myexamplebank.com= Attacker IP address X

Passwords

Desired page

With DNSSEC

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DNSSEC ccTLD Map

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DNSSEC Deployment – Current Status

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DNSSEC Validation – Current Status

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DNSSEC Validation – Current Status

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DNSSEC: So what’s the problem?

• Not enough IT departments know about it or are too busy putting out other security fires?

• When they do look into it they hear old stories of FUD and lack of turnkey solutions?

• Registrars*/DNS providers see no demand leading to “chicken-and-egg” problems.

*but required by new ICANN registrar agreement

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The Business Case for DNSSEC

• Cyber security is becoming a greater concern to enterprises, government, and end users. DNSSEC is a key tool and differentiator.

• DNSSEC is the biggest security upgrade to Internet infrastructure in over 20 years. It is a platform for new security applications (for those that see the opportunity).

• DNSSEC infrastructure deployment has been brisk but requires expertise. Getting ahead of the curve is a competitive advantage.

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What you can do

• For Companies:– Sign your corporate domain names– Just turn on validation on corporate DNS resolvers

• For Users:– Ask ISPs/DNS Operators to turn on validation on their DNS resolvers

• For All:– Take advantage of DNS and DNSSEC education and training– Encourage to join TLD policy discussions through ICANN constituencies

such as gNSO and ccNSO.

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New concepts

• Secure Entry Point and Chain of Trust– Delegating Signing Authority

• New packet options (flags)– CD, AD, DO

• New RRs– DNSKEY, RRSIG, NSEC/NSEC3 and DS

• Signature expiration

• Key Rollovers

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Chain of Trust and Secure Entry Point

• Using the existing delegation based model of distribution

• Don’t sign the entire zone, sign a RRset

• Parent DOES NOT sign the child zone. The parent signs a pointer (hash) to the key used to sign the data of the child zone (DS record)

• Example with www.myzone.net.

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“.”

net

myzone

www

Secure Entry Point

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Delegation of Trust

• Data authenticity and integrity by signing the Resource Records Sets with a private key

• Public DNSKEYs published, used to verify the RRSIGs

• Children sign their zones with their private key– Authenticity of that key established by parent signing hash (DS) of the child zone's key

• Repeat for parent…

• Not that difficult on paper– Operationally, it is a bit more complicated– DSKEY → KEY –signs→ zone data

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New RR: DNSKEY

• FLAGS determines the usage of the key• PROTOCOL is always 3 (DNSSEC)• ALGORITHM can be (3: DSA/SHA-1, 5: RSA/SHA1, 8: RSA/SHA-256, 12: ECC-

GOST)– http://www.iana.org/assignments/dns-sec-alg-numbers/dns-sec-alg-numbers.xml

example.net. 43200 DNSKEY 256 3 7 (

AwEAAbinasY+k/9xD4MBBa3QvhjuOHIpe319SFbWYIRj/nbmVZfJnSw7By1cV3Tm7ZlLqNbcB86nVFMSQ3JjOFMr

....) ; ZSK; key id = 23807

OWNER TYPE FLAGSPROTOCOL

ALGORITHM

PUBLIC KEY(BASE64)

KEY ID

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DNSKEY: Two Keys, not one…

• There are in practice at least two DNSKEY pairs for every zone

• Originally, one key-pair (public, private) defined for the zone– private: key used to sign the zone data (RRsets)– public: key published (DNSKEY) in the zone

• DNSSEC works fine with a single key pair• Problem with using a single key:

– Every time the key is updated, the DS record must be updated on the parent zone as well

– Introduction of Key Signing Key (flags=257)

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KSK and ZSK

• Key Signing Key (KSK)– Pointed to by parent zone in the form of DS (Delegation Signer). Also called Secure

Entry Point.– Used to sign the Zone Signing Key– Flags: 257

• Zone Signing Key (ZSK)– Signed by the KSK– Used to sign the zone data RRsets– Flags: 256

• This decoupling allows for independent updating of the ZSK without having to update the KSK, and involve the parents (i.e. less administrative interaction)

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New RR: RRSIG (Resource Record Signature)

example.net. 600 A 192.168.10.10example.net. 600 A 192.168.23.45

example.net. 600 RRSIG A 7 2 600 (

20150115154303 20141017154303 23807 example.net.

CoYkYPqE8Jv6UaVJgRrh7u16m/cEFGtFM8TArbJdaiPuW77wZhrvonoBEyqYbhQ1yDaS74u9whECEe08gfoe1FGg. . .)

OWNER TYPETYPE COVERED

ALG#LABELS

TTL

SIG. EXPIRATION SIG. INCEPTION KEY IDSIGNER NAME

SIGNATURE

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RRSIG

• Typical default values– Signature inception time is 1 hour before.– Signature expiration is 30 from now– Proper timekeeping (NTP) is required

• What happens when signatures run out?– SERVFAIL– Domain effectively disappears from the Internet for validating resolvers

• Note that keys do not expire

• No all RRSets need to be resigned at the same time

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New RR: NSEC

• NXDomains also must be verified

• NSEC provides a pointer to the Next SECure record in the chain of records.

myzone. NS …alpha.myzone. A …beta.myzone. CNAME …charlie.myzone. A …delta.myzone. MX …

zulu.myzone. A …

RESOLVER

AUTH for myzone.omega.myzone ?

NSEC] delta.myzone. , zulu.myzone.[

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New RR: NSEC3

• To avoid concerns about “zone enumeration”

• To avoid large zone-files: opt-out concept

H(zulu.myzone.)H(myzone.)H(delta.myzone.) H(charlie.myzone.) H(beta.myzone.)H(alpha.myzone.)

1-Way HashAUTH for myzone digests.

RESOLVER

omega.myzone ?

NSEC3[ H(charlie.myzone.) , H(alpha.myzone.) ]

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New RR: DS (Delegation Signer)

• Hash of the KSK of the child zone

• Stored in the parent zone, together with the NS RRs indicating a delegation of the child zone.

• The DS record for the child zone is signed together with the rest of the parent zone data

• NS records are NOT signed (they are a hint/pointer)

myzone. DS 61138 5 1 F6CD025B3F5D0304089505354A0115584B56D683

myzone. DS 61138 5 2 CCBC0B557510E4256E88C01B0B1336AC4ED6FE08C8268CC1AA5FBF00 5DCE3210

Digest type 1 = SHA-1, 2 = SHA-256

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Signatures Expiration and Key Rollovers

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Signature Expiration

• Signatures are per default 30 days (BIND)

• Need for regular resigning:– To maintain a constant window of validity for the signatures of the existing RRset– To sign new and updated Rrsets– Use of jitter to avoid having to resign all expiring RRsets at the same time

• The keys themselves do NOT expire…

• But they may need to be rolled over...

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Key Rollovers

• Try to minimise impact– Short validity of signatures– Regular key rollover

• Remember: DNSKEYs do not have timestamps– the RRSIG over the DNSKEY has the timestamp

• Key rollover involves second party or parties:– State to be maintained during rollover– Operationally expensive

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Key Rollovers

• Two methods for doing key rollover– Pre-Publish– Double Signature

• KSK and ZSK rollover use different methods.– Remember that KSK needs to interact with parent zone to update

DS record.

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DNSSEC Deployment @Root

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DNSSEC Deployment @Root

• Multi-stakeholder, bottom-up trust model* /w 21 crypto officers from around the world

• Broadcast Key Ceremonies and public docs• SysTrust audited• FIPS 140-2 level 4 HSMs

Root DPSDNSSEC Practice Statement

*Managed by technical community+ICANN

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DNSSEC – Signing vs. Validation

¤ DNS Security Extensions¤ Digital signature is the basic element of work

¤ Signing¤ Zone Administrators add digital signatures

¤ Validation¤ DNS Caches, DNS Stubs check the signatures in a few ways, cryptographic

and other (time, etc.)

¤ Impact of DNSSEC root KSK rollover¤ DNSSEC validators (e.g., some ISPs) need to prepare, new "root" of trust

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The Root Zone DNSSEC KSK

DATA

¤The Root Zone DNSSEC Key Signing Key “KSK” is the top most cryptographic key in the DNSSEC hierarchy

¤Public portion of the KSK is configuration parameter in DNS validating revolvers

KSK

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Recognizing KSK-2017

. IN DS 20326 8 2E06D44B80B8F1D39A95C0B0D7C65D08458E880409BBC683457104237C7F8EC8D"Root"

¤The KSK-2017’s Key Tag is

20326

¤The Delegation Signer (DS) Resource Record for KSK-2017 is

Note: liberties taken with formatting for presentation purposes

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KSK-2017 in a DNSKEY Resource Record

. IN DNSKEY 257 3 8AwEAAaz/tAm8yTn4Mfeh5eyI96WSVexTBAvkMgJzkKTOiW1vkIbzxeF3+/4RgWOq7HrxRixHlFlExOLAJr5emLvN7SWXgnLh4+B5xQlNVz8Og8kvArMtNROxVQuCaSnIDdD5LKyWbRd2n9WGe2R8PzgCmr3EgVLrjyBxWezF0jLHwVN8efS3rCj/EWgvIWgb9tarpVUDK/b58Da+sqqls3eNbuv7pr+eoZG+SrDK6nWeL3c6H5Apxz7LjVc1uTIdsIXxuOLYA4/ilBmSVIzuDWfdRUfhHdY6+cn8HFRm+2hM8AnXGXws9555KrUB5qihylGa8subX2Nn6UwNR1AkUTV74bU=

"Root"

¤The DNSKEY resource record will be:

Note: liberties taken with formatting for presentation purposes

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Why are there DS and DNSKEY forms of KSK-2017?

¤Tools that you will use to manage DNSSEC trust anchor configurations work on either the DS form, the DNSKEY form or both¤For each tool there are historical reasons¤The DS record contains a hash of KSK-2017¤The DNSKEY record contains the public key of KSK-2017

¤Consult your tool’s documentation to know which is appropriate

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Preferred Approach

¤Mindful that the choice is a matter of local policy

¤DNSSEC validation is for the benefit of the receiver¤Not all operational environments are the same, not all validating

tools implement Automated Updates¤ ICANN is doing its best to accommodate different approaches

¤Automated Updates is likely the preferred approach

¤Relies only on what has been trusted before¤ It's the most reliable/stable approach, simplest basis for trust

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Be aware whether DNSSEC is enabled in your servers

Be aware of how trust is evaluated in your operations

Test/verify your set ups

Inspect configuration files, are they (also) up to date?

If DNSSEC validation is enabled or planned in your system

o Have a plan for participating in the KSK rollovero Know the dates, know the symptoms, solutions

What Do Operators Need to Do?

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Latest update on the Root KSK Rollover Project

• https://www.icann.org/news/blog/update-on-the-root-ksk-rollover-project

Visit us at icann.org

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Thank You and Questions

Email: champika.wijayatunga@icann.org