IETF DPRIVE WG: Encrypting DNS Sara Dickinson Sinodun ICANN 54 - - - PowerPoint PPT Presentation

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IETF DPRIVE WG: Encrypting DNS Sara Dickinson Sinodun ICANN 54 - - - PowerPoint PPT Presentation

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IETF DPRIVE WG: Encrypting DNS Sara Dickinson Sinodun ICANN 54 - Tech Day October 2015 DPRIVE WG Focus is stub to recursive Group IETF92 IETF91 IETF93 created A ID: problem-statement RFC7626 ID: dns-tls-newport A ID:

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SLIDE 1

IETF DPRIVE WG: Encrypting DNS

Sara Dickinson Sinodun ICANN 54 - Tech Day October 2015

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SLIDE 2

IETF93 IETF92 IETF91

DPRIVE WG

2014 2015 Group created

Q4 Q1 Q2 Q3 Q4

ID: start-tls-for-dns ID:dns-over-tls

Early port allocation

ID: dns-tls-newport ID: start-tls-for-dns

A

ID: problem-statement RFC7626

A

ID: dnsodtls

ID: dnsodtls

A

TIME

STARTTLS & port

Focus is stub to recursive

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SLIDE 3

Pros and Cons

Pros Cons STARTTLS

  • Port 53
  • Known technique
  • Incrementation deployment
  • Port 53 - middleboxes?
  • Existing TCP implementations
  • Downgrade attack on negotiation
  • Latency from negotiation

TLS (new port)

  • New DNS port (no

interference with port 53)

  • Existing implementations
  • New port assignment

DTLS

  • UDP based
  • Certain performance

aspects

  • Truncation of DNS messages

(just like UDP)

➡ Fallback to clear text or TLS

❌ Can’t be standalone solution

  • No running code
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SLIDE 4

Early port allocation

  • 8th October 2015 - IANA assigned port 853:

domain-s 853 tcp DNS query-response protocol run over TLS/DTLS domain-s 853 udp DNS query-response protocol run over TLS/DTLS

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SLIDE 5

DNS-over-TLS needs TCP !

  • DNS-over-TCP… historically used only as a fallback transport

(TC=1 ➡ ‘one-shot’ TCP, Zone transfer)

  • 2010: RFC5966 - TCP a requirement for DNS implementations
  • 2014: Connection-oriented DNS - USC/ISI paper
  • draft-ietf-dnsop-5966bis
  • performance on par with UDP, security/robustness
  • draft-ietf-dnsop-edns-tcp-keepalive - persistent TCP connections
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SLIDE 6

TCP/TLS Performance

Goals:

  • 1. Handle many TCP connections robustly
  • 2. Optimise TCP/TLS set up & resumption
  • TCP FastOpen, TLS resumption, [TLS 1.3]
  • 3. Amortise cost of TCP/TLS setup
  • Send many messages efficiently
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SLIDE 7

Performance (5966bis)

Client - Query pipelining

q1, q2 q1 a1 q2 a2

connection re-use

q2 delayed waiting for q1 (+1 RTT) q1, q2 q1 a1 q2 a2

pipelining

0 extra RTT (stub) (recursive)

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SLIDE 8

Performance (5966bis)

Server - concurrent processing of requests sending of out of order responses

q1, q2 q1 a1 q2 a2

in-order

q2 delayed waiting for q1 (+1 RTT) q1, q2 q1 a1 q2 a2

concurrent, OOOR

0 extra RTT stub

R

A

R A

reply as soon as possible

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SLIDE 9

DNS-over-TLS implementations

  • Unbound 1.4.14 (2011) - DNSTrigger
  • TLS patches for LDNS and NSD
  • [BIND TCP improvements]
  • getdns - ongoing development of DNS-over-TLS
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SLIDE 10
  • Modern async DNSSEC enabled API
  • https://getdnsapi.net
  • Stub mode has TLS with flexible privacy policy and fallback:

Strict (Authenticated) TLS only Opportunistic TLS Fallback to TCP, UDP

  • Pipelining, OOOP, Configurable idle time
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SLIDE 11

Current status

Software digit LDNS getdns Unbound NSD BIND mode client client (drill) stub

recursive*

server client server server/ client

TLS TFO Conn reuse Pipelining OOOP

Dark Green: Latest stable release supports this Light Green: Patch available Yellow: Patch in progress, or requires building a patched dependancy Grey: Not applicable or not planned


* getdns uses libunbound in recursive mode

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SLIDE 12
  • UTA (Using TLS in Applications) WG produced

RFC7525 this year - “BCP for TLS and DTLS”

  • Key recommendations - Protocol versions:
  • TLS v1.2 MUST be supported and preferred
  • Recommended Cipher Suites (4 of ~100):
  • AEAD mode - Forward secrecy for key exchange





  • TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256

TLS BCP

DNS-over-TLS is relatively ‘green-field’

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SLIDE 13

TLS BCP - Authentication

  • Secure discovery of certificate/hostname/etc.
  • For DNS-over-TLS?
  • Pre-deployed configuration profile
  • DANE… (clear-text or un-authenticated TLS)
  • boot strap problem
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SLIDE 14

Summary

  • Active work on encrypting DNS in DPRIVE
  • For DNS-over-TLS performance is key
  • Client should consider privacy policy
  • see Appendix for stub/recursive examples
  • Know your (D)TLS Best Current Practices
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SLIDE 15

Thank you!

Any Questions? sara@sinodun.com

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SLIDE 16

Appendix

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SLIDE 17

Examples

STUB MODE TLS ENABLED

Next release: Hostname verification 1.5.5

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SLIDE 18
  • Configuration:
  • Hostname verification required (Default)
  • Correct hostname for Unbound resolver
  • TLS as only transport
  • RESULT:
  • TLS used (cert & hostname verified)

Scenario 1:

Strict TLS

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SLIDE 19
  • Configuration:
  • Hostname verification required (Default)
  • No or incorrect hostname
  • TLS as only transport
  • RESULT:
  • Query fails

Scenario 2:

Strict TLS

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SLIDE 20
  • Configuration:
  • Hostname verification optional
  • Valid, none or incorrect hostname
  • TLS as only transport
  • RESULT:
  • TLS used (hostname verification tried but fails)

Scenario 3:

Opportunistic TLS

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SLIDE 21

Scenario 4:

  • Configuration:
  • Hostname verification required (default)
  • Valid, none or incorrect hostname
  • TLS with fallback to TCP
  • RESULT:
  • TLS used (hostname verification tried but fails)

Opportunistic TLS

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SLIDE 22

Example

STUB MODE NO TLS

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SLIDE 23
  • Configuration:
  • Hostname verification required (default)
  • Valid, none or incorrect hostname
  • TLS with fallback to TCP
  • RESULT:
  • TCP used (TLS tried, but fails)

Scenario 3:

Opportunistic TLS