EDU Tutorial: DNS Privacy Sara Dickinson Sinodun - - PowerPoint PPT Presentation

▶
edu tutorial dns privacy
SMART_READER_LITE
LIVE PREVIEW

EDU Tutorial: DNS Privacy Sara Dickinson Sinodun - - PowerPoint PPT Presentation

Aug 28, 2022 247 likes •822 views

EDU Tutorial: DNS Privacy Sara Dickinson Sinodun sara@sinodun.com EDU Tutorial @ IETF_97 Seoul (Nov 2017) Overview Goal: Give audience historical background on why DNS Privacy is an important topic

slide-1
SLIDE 1

EDU Tutorial: 
 DNS Privacy

Sara Dickinson Sinodun sara@sinodun.com EDU Tutorial @ IETF_97 Seoul (Nov 2017)

slide-2
SLIDE 2

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Overview

  • Goal:
  • Give audience historical background on why DNS

Privacy is an important topic

  • Chart progress during last 3 years
  • Present current status and tools

2

slide-3
SLIDE 3

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Agenda

  • Internet Privacy - presented by dkg
  • DNS Privacy - A brief history
  • DPRIVE WG et al.
  • Implementation & deployment today
  • Meet Stubby - a privacy stub resolver
  • Ongoing & future work

3

slide-4
SLIDE 4

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Internet Privacy

Daniel Kahn Gillmor ACLU

4

slide-5
SLIDE 5

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Privacy

  • A brief history

5

slide-6
SLIDE 6

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

IETF Privacy activity

6

March 2011 I-D: Privacy Considerations for Internet Protocols (IAB) June 2013

Snowdon revelations

July 2013

RFC6973: Privacy Considerations for Internet Protocols

May 2014

RFC7258: Pervasive Monitoring is an Attack

August 2015 RFC7624: Confidentiality in the Face of Pervasive

Surveillance: A Threat model and Problem Statement Much other ongoing work…..

What timing!

slide-7
SLIDE 7

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

RFC 7258

“The IETF community's technical assessment is that PM is an attack on the privacy of Internet users and

  • rganisations.”

“The IETF community has expressed strong agreement that PM is an attack that needs to be mitigated where possible, via the design of protocols that make PM significantly more expensive or infeasible. “

7

slide-8
SLIDE 8

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Privacy in 2013?

  • DNS [RFC1034/5 - 1987] - original design availability,

redundancy and speed!

  • DNS standards:
  • UDP (99% of traffic to root)
  • TCP only for ‘fallback’ when UDP MTU exceeded and XFR

(support only mandatory from 2010)

  • Perception: The DNS is public, right? It is not sensitive/personal

information….it doesn’t need to be encrypted

8

DNS sent in clear text => NSA: ‘MORECOWBELL’ DNS monitoring

slide-9
SLIDE 9

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Disclosure Example 1

9

Rec

Auth for .org

Root

datatracker.ietf.org

Auth for ietf.org

datatracker.ietf.org datatracker.ietf.org datatracker.ietf.org Leak information datatracker.ietf.org datatracker.ietf.org

slide-10
SLIDE 10

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Privacy in 2013?

  • RFC6891: Extension Mechanisms for DNS (EDNS0)
  • But…. mechanism enabled addition of end-user data

into DNS queries (non-standard options)

  • Client subnet (RFC7871*)
  • User MAC addresses or


user name/id

10

CDN justification: Faster content (geo location) ISP justification: Parental Filtering (per device)

Intended to enhance DNS protocol capabilities

* Informational

slide-11
SLIDE 11

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Disclosure Example 2

11

[User src address] MAC address in DNS query Client Subnet option contains source subnet in DNS query

Rec

Auth

Stub

CPE

ietf.org ? [00:00:53:00:53:00] ? ietf.org ? [192.168.1]

slide-12
SLIDE 12

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Disclosure Example 2

12

Even behind a NAT, do not have anonymity!

Rec

Auth

Stub

CPE

ietf.org ? conradhotels.hilton.com ? ba.com ? ietfmemes.tumblr.com ?

Even behind a recursive do not have anonymity!

slide-13
SLIDE 13

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Disclosure Example 3

13

Rec

Auth for .org Root

Who monitors or has access here?

  • When at home…
  • When in a coffee shop…

Who monitors or has access here? Who monitors or has access here?

slide-14
SLIDE 14

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS - complications

  • Basic problem is leakage of meta data
  • Allows re-identification of individuals
  • But.. legal requirements on providers regarding

access to user data (country specific)

  • Traffic analysis is possible based just on timings

and cache snooping

  • DNS Filtering is becoming more prevalent


14

slide-15
SLIDE 15

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Risk Matrix

15

In-Flight At Rest Risk Stub => Rec Rec => Auth At 
 Recursive At 
 Authoritative

Passive Monitoring 
 Active Monitoring 
 Other Disclosure Risks e.g. Data breaches

slide-16
SLIDE 16

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Run a local resolver?

  • Some users chose to run a local resolver on their

client machine (e.g. Unbound) for increased privacy

  • bypass intermediate resolvers
  • have local DNSSEC validation
  • But still sending queries in clear text, still querying

authoritative servers

16

slide-17
SLIDE 17

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Privacy options (2013)

  • DNSCurve
  • Daniel J. Bernstein, initial interest but not adoption
  • DNSCrypt
  • Many implementations, several open DNSCrypt

Resolvers (OpenDNS), [Yandex browser]


  • Authentication with some privacy
  • Documented but not standard

17

Stub-Recursive Recursive-Auth

Anti-spoofing, anti DoS

slide-18
SLIDE 18

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Privacy options (2014)

  • DNSTrigger (NLNet Labs)
  • Client software to enable DNSSEC
  • Used TLS on port 443 as last ditch attempt to

enable DNSSEC

  • So… there was a DNS-over-TLS implementation in

Unbound recursive resolver
 
 


18

Goal was DNSSEC, not Privacy!

slide-19
SLIDE 19

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DPRIVE WG et al.

19

slide-20
SLIDE 20

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DPRIVE WG

  • DPRIVE WG create in 2014





  • Why not tackle whole problem?
  • Don’t boil the ocean
  • Rec to Auth is a particularly hard problem
  • Step-by-step solution

20

Charter: Primary Focus is Stub to recursive

slide-21
SLIDE 21

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Privacy problem

21

Rec

Auth for .org Root

Relationship: 1 to ‘a few’ some of whom are know (ISP) Relationship:1 to many most

  • f whom are not known

=> Authentication is hard

slide-22
SLIDE 22

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

RFC 7626 - DNS Privacy Considerations

  • Problem statement: Expert coverage of risks

throughout DNS ecosystem

  • Rebuts “alleged public nature of DNS data”
  • The data may be public, but a DNS ‘transaction’


is not/should not be.

22

Worth a read - many interesting issues here!

“A typical example from outside the DNS world is: the web site of Alcoholics Anonymous is public; the fact that you visit it should not be.”

slide-23
SLIDE 23

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Choices, choices…

  • So… we know the problem but what

mechanism to use for encrypting DNS?

  • STARTTLS
  • TLS
  • DTLS
  • Confidential DNS draft

23

Drafts submitted on all these solutions to the working group

slide-24
SLIDE 24

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Encryption Options

Pros Cons STARTTLS

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

TLS (new port)

  • New DNS port 


(no interference with port 53)

  • Existing implementations
  • New port assignment
  • Scalability?

DTLS (new port)

  • UDP based
  • Not as widely used/

deployed

  • Truncation of DNS messages

(just like UDP)

➡Fallback to TLS or clear text

❌Can’t be standalone solution

24

slide-25
SLIDE 25

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Encrypted DNS ‘TODO’ list

  • Get a new port
  • DNS-over-TLS: Address issues with DNS-
  • ver-TCP in standards and implementations
  • Tackle authentication of DNS Privacy

servers

  • What about traffic analysis of encrypted

traffic (padding, etc.)

25

slide-26
SLIDE 26

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Get a new port!

  • Oct 2015 - 853 is the magic number

26

Your request has been processed. We have assigned the following system port number as an early allocations per RFC7120, with the DPRIVE Chairs as the point of contact: domain-s 853 tcp DNS query-response protocol run over TLS/DTLS domain-s 853 udp DNS query-response protocol run over TLS/DTLS

slide-27
SLIDE 27

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS + TCP/TLS?

  • TCP/TLS is a new challenge for DNS operators
  • DNS-over-TCP history:
  • typical DNS clients do ‘one-shot’ TCP
  • DNS servers have very basic TCP capabilities
  • No attention paid to TCP tuning, robustness
  • Performance tools based on one-shot TCP


27

slide-28
SLIDE 28

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Fix DNS-over-TCP/TLS

28

Goal How?

Optimise set up & resumption TFO Fast Open TLS session resumption [TLS 1.3] Amortise cost of TCP/TLS setup RFC7766 (bis of RFC5966) - March 2016: Client pipelining (not one-shot!), Server concurrent processing, Out-of-order responses
 RFC7858: Persistent connections (Keepalive) Servers handle many connections robustly Learn from HTTP world!

slide-29
SLIDE 29

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Performance (RFC7766)

Client - pipeline requests, keep connection open and handle out-of-order response Server - concurrent processing of requests sending of out of order responses

29

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

slide-30
SLIDE 30

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Authentication in DNS-over-(D)TLS

2 Usage Profiles:

  • Strict
  • “Do or do not. There is no try.”
  • Opportunistic
  • “Success is stumbling 


from failure to failure 
 with no loss of enthusiasm”

30

Encrypt & Authenticate or Nothing Try (in order):

  • Authentication & Encryption then
  • Encryption then
  • Clear text
slide-31
SLIDE 31

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Authentication in DNS-over-(D)TLS

  • Authentication based on either:
  • Authentication domain name
  • SPKI pinset
  • Shouldn’t DNS use DANE…? Well - even better:
  • draft-shore-tls-dnssec-chain-extension

31

slide-32
SLIDE 32

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Auth using DANE

32

DNS Privacy server DNS Privacy client [DNSSEC] 1: Obtain a Auth Domain name & IP address

(1a)

  • Configure Auth

domain name

  • Do Opportunistic

SRV lookup

2a:

  • Opportunistic lookup of DANE

records for server

  • Validate locally with DNSSEC

TLS

DNS Privacy client [DNSSEC] DNS Privacy client [DNSSEC]

slide-33
SLIDE 33

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

TLS DNSSEC Chain Extension

33

DNS Privacy server DNS Privacy client [DNSSEC] 1: Obtain a Auth Domain name & IP address

(1a)

  • Configure Auth

domain name

  • Do Opportunistic

SRV lookup

0 (or 2): Obtains DANE records for itself!

Server Hello: Server DANE records Client Hello: TLS DNSSEC Chain Ext

DNS Privacy client [DNSSEC] DNS Privacy client [DNSSEC]

  • Reduces Latency
  • Eliminates need for

validating recursive

slide-34
SLIDE 34

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DPRIVE Solution Documents (stub to recursive)

34

Document Date Topic RFC7858 May 2016 DNS-over-TLS RFC7830 May 2016 Padding

draft-ietf-dprive-dnsodtls*

Completed WGLC

DNS-over-DTLS

draft-ietf-dprive-dtls-and- tls-profiles

In WGLC

Authentication for DNS-over-(D)TLS

*Intended status: Experimental

slide-35
SLIDE 35

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

What about Recursive to Authoritative?

  • DPRIVE - Next step is to tackle this issue with encryption
  • draft-bortzmeyer-dprive-step-2
  • Presents 6 authentication options/models
  • Authoritative DNS servers using TLS…
  • Re-charter? WG discussion on this here in Seoul (Fri)!
  • DNSOP - RFC7816: QNAME Minimisation (mitigates)

35

slide-36
SLIDE 36

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS Disclosure Example 1

36

Rec

Auth for .org

Root

datatracker.ietf.org

Auth for ietf.org

datatracker.ietf.org datatracker.ietf.org datatracker.ietf.org Leaks information

slide-37
SLIDE 37

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

QNAME Minimisation

37

Rec

Auth for .org

Root

datatracker.ietf.org

Auth for ietf.org

  • rg

ietf.org datatracker.ietf.org

slide-38
SLIDE 38

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS-over-HTTP(S)

  • DNS-over-HTTP(S) has been around a while…
  • draft-shane-review-dns-over-http
  • Privacy (HTTPS authentication)
  • Bypass port 53 interference (middlebox, captive portals)
  • Higher level API

38

slide-39
SLIDE 39

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS-over-HTTP(S)

  • Google: DNS-over-HTTPS
  • draft-ietf-dnsop-dns-wireformat-http
  • “Servers and clients SHOULD use TLS for

communication.”

  • draft-hoffman-dns-over-http - DNS Queries over HTTPS
  • Non-WG Mailing list and Bar BOF here (Tuesday)

39

slide-40
SLIDE 40

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Data handling policies

  • Do you read the small print of your ISPs contract?
  • More work/research needed in this area
  • Transparency from providers
  • Methods for de-identification of user data (e.g. DITL)
  • Use of ‘PassiveDNS’ data for research/security

analysis

40

slide-41
SLIDE 41

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Risk Mitigation Matrix

41

In-Flight At Rest Risk Stub => Rec Rec => Auth At 
 Recursive At 
 Authoritative

Passive monitoring

Encryption (e.g. TLS, HTTPS) QNAME Minimization

Active monitoring

Authentication & Encryption

Other Disclosure Risks e.g. Data breaches

Data Best Practices (Policies)
 e.g. De-identification

slide-42
SLIDE 42

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Implementation Status

42

slide-43
SLIDE 43

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Recursive implementations

43

Features Recursive resolver Unbound BIND Knot Res TCP/TLS Features TCP fast open Process pipelined queries Provide OOOR EDNS0 Keepalive TLS Features TLS on port 853 Provide server certificate EDNS0 Padding Rec => Auth QNAME Minimisation

Dark Green: Latest stable release supports this Light Green: Patch available Yellow: Patch/work in progress, or requires building a patched dependency Purple: Workaround available Grey: Not applicable or not yet planned

RECURSIVE

slide-44
SLIDE 44

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Alternative server side solutions

  • dnsdist from PowerDNS would be great…
  • But no support yet
  • Pure TLS load balancer
  • NGINX, HAProxy
  • BIND article on using stunnel

44

Disadvantages

  • server must still have decent TCP capabilities
  • DNS specific access control is missing
  • pass through of edns0-tcp-keepalive option

RECURSIVE

slide-45
SLIDE 45

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Stub implementations

45

Features Stub ldns digit getdns BIND (dig) TCP/TLS Features TCP fast open Connection reuse Pipelining of queries Process OOOR EDNS0 Keepalive TLS Features TLS on port 853 Authentication of server EDNS0 Padding

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

* getdns uses libunbound in recursive mode

STUB

slide-46
SLIDE 46

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Implementation Status

  • Increasing uptake of better DNS-over-TCP
  • Several implementations of DNS-over-TLS
  • None yet of DNS-over-DTLS
  • Key is enabling end users and application

developers to easily adopt DNS Privacy

46

slide-47
SLIDE 47

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Deployment Status

47

slide-48
SLIDE 48

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

DNS-over-TLS Servers

48

RECURSIVE

https://portal.sinodun.com/wiki/display/TDNS/DNS-over-TLS+test+servers

Hosted by Software Supports Strict? NLnet Labs Unbound Y OARC Unbound Surfnet (Sinodun) Bind + HAProxy Bind + nginx Y IETF?

slide-49
SLIDE 49

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

RIPE NCC

  • RIPE DNS WG: Discussion support of experimental

DNS Privacy Services

  • RIPE NCC have expressed interest in a community

effort:

  • Research various solutions and issues
  • ‘DNS-over-TLS operational guidance’

49

RECURSIVE

slide-50
SLIDE 50

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

getdns

  • Modern async DNSSEC enabled API
  • https://getdnsapi.net
  • Written in C, several bindings
  • DNS-over-TLS, validating DNSSEC stub
  • ‘Stubby’ now available for testing

50

STUB

slide-51
SLIDE 51

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Meet Stubby - A Privacy Enabling Stub Resolver

51

slide-52
SLIDE 52

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Stubby -
 getdns_query by another name

  • 1.1.0a3 - getdns_query tool extended to
  • Run as daemon handling requests
  • Configure OS DNS resolution to point at 127.0.0.1
  • Reads default from /etc/stubby.conf (TLS)
  • Supports domain name and SPKI pinset

authentication, Strict and Opportunistic

52

slide-53
SLIDE 53

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Stubby Demo

  • How to build and use Stubby

53

slide-54
SLIDE 54

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Ongoing and Future work

  • Hacking this weekend at the IETF 97 Hackathon
  • Lots of work on Stubby!
  • More complete recursive implementations
  • Increased deployment
  • More DPRIVE work: Recursive to Auth….

54

slide-55
SLIDE 55

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Summary

  • DNS Privacy is important issue
  • Active work on the large solution space
  • Can test DNS Privacy today using Stubby & current

test recursive servers

  • More DNS Privacy services on the way…

55

slide-56
SLIDE 56

DNS Privacy Tutorial @ IETF 97 Nov 2016, Seoul

Thank you!

Any Questions? sara@sinodun.com


56