< draft-ietf-dprive-bcp-op-01.txt   draft-ietf-dprive-bcp-op-02.txt >
dprive S. Dickinson dprive S. Dickinson
Internet-Draft Sinodun IT Internet-Draft Sinodun IT
Intended status: Best Current Practice B. Overeinder Intended status: Best Current Practice B. Overeinder
Expires: June 21, 2019 R. van Rijswijk-Deij Expires: September 12, 2019 R. van Rijswijk-Deij
NLnet Labs NLnet Labs
A. Mankin A. Mankin
Salesforce Salesforce
December 18, 2018 March 11, 2019
Recommendations for DNS Privacy Service Operators Recommendations for DNS Privacy Service Operators
draft-ietf-dprive-bcp-op-01 draft-ietf-dprive-bcp-op-02
Abstract Abstract
This document presents operational, policy and security This document presents operational, policy and security
considerations for DNS operators who choose to offer DNS Privacy considerations for DNS operators who choose to offer DNS Privacy
services. With these recommendations, the operator can make services. With these recommendations, the operator can make
deliberate decisions regarding which services to provide, and how the deliberate decisions regarding which services to provide, and how the
decisions and alternatives impact the privacy of users. decisions and alternatives impact the privacy of users.
This document also presents a framework to assist writers of DNS This document also presents a framework to assist writers of DNS
skipping to change at page 1, line 36 skipping to change at page 1, line 36
in [RFC6841]). in [RFC6841]).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 21, 2019. This Internet-Draft will expire on September 12, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Privacy related documents . . . . . . . . . . . . . . . . . . 5 3. Privacy related documents . . . . . . . . . . . . . . . . . . 5
4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
5. Recommendations for DNS privacy services . . . . . . . . . . 6 5. Recommendations for DNS privacy services . . . . . . . . . . 6
5.1. On the wire between client and server . . . . . . . . . . 7 5.1. On the wire between client and server . . . . . . . . . . 7
5.1.1. Transport recommendations . . . . . . . . . . . . . . 7 5.1.1. Transport recommendations . . . . . . . . . . . . . . 7
5.1.2. Authentication of DNS privacy services . . . . . . . 7 5.1.2. Authentication of DNS privacy services . . . . . . . 7
5.1.3. Protocol recommendations . . . . . . . . . . . . . . 9 5.1.3. Protocol recommendations . . . . . . . . . . . . . . 9
5.1.4. Availability . . . . . . . . . . . . . . . . . . . . 11 5.1.4. Availability . . . . . . . . . . . . . . . . . . . . 10
5.1.5. Service options . . . . . . . . . . . . . . . . . . . 11 5.1.5. Service options . . . . . . . . . . . . . . . . . . . 11
5.1.6. Impact on Operators . . . . . . . . . . . . . . . . . 11 5.1.6. Impact on Operators . . . . . . . . . . . . . . . . . 11
5.1.7. Limitations of using a pure TLS proxy . . . . . . . . 11 5.1.7. Limitations of using a pure TLS proxy . . . . . . . . 12
5.2. Data at rest on the server . . . . . . . . . . . . . . . 12 5.2. Data at rest on the server . . . . . . . . . . . . . . . 12
5.2.1. Data handling . . . . . . . . . . . . . . . . . . . . 12 5.2.1. Data handling . . . . . . . . . . . . . . . . . . . . 12
5.2.2. Data minimization of network traffic . . . . . . . . 13 5.2.2. Data minimization of network traffic . . . . . . . . 13
5.2.3. IP address pseudonymization and anonymization methods 14 5.2.3. IP address pseudonymization and anonymization methods 14
5.2.4. Pseudonymization, anonymization or discarding of 5.2.4. Pseudonymization, anonymization or discarding of
other correlation data . . . . . . . . . . . . . . . 15 other correlation data . . . . . . . . . . . . . . . 15
5.2.5. Cache snooping . . . . . . . . . . . . . . . . . . . 15 5.2.5. Cache snooping . . . . . . . . . . . . . . . . . . . 16
5.3. Data sent onwards from the server . . . . . . . . . . . . 16 5.3. Data sent onwards from the server . . . . . . . . . . . . 16
5.3.1. Protocol recommendations . . . . . . . . . . . . . . 16 5.3.1. Protocol recommendations . . . . . . . . . . . . . . 16
5.3.2. Client query obfuscation . . . . . . . . . . . . . . 17 5.3.2. Client query obfuscation . . . . . . . . . . . . . . 17
5.3.3. Data sharing . . . . . . . . . . . . . . . . . . . . 17 5.3.3. Data sharing . . . . . . . . . . . . . . . . . . . . 18
6. DNS privacy policy and practice statement . . . . . . . . . . 18 6. DNS privacy policy and practice statement . . . . . . . . . . 19
6.1. Recommended contents of a DPPPS . . . . . . . . . . . . . 18 6.1. Recommended contents of a DPPPS . . . . . . . . . . . . . 19
6.1.1. Policy . . . . . . . . . . . . . . . . . . . . . . . 18 6.1.1. Policy . . . . . . . . . . . . . . . . . . . . . . . 19
6.1.2. Practice. . . . . . . . . . . . . . . . . . . . . . . 19 6.1.2. Practice . . . . . . . . . . . . . . . . . . . . . . 20
6.2. Current policy and privacy statements . . . . . . . . . . 20 6.2. Current policy and privacy statements . . . . . . . . . . 21
6.3. Enforcement/accountability . . . . . . . . . . . . . . . 21 6.3. Enforcement/accountability . . . . . . . . . . . . . . . 21
7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 21 7. IANA considerations . . . . . . . . . . . . . . . . . . . . . 22
8. Security considerations . . . . . . . . . . . . . . . . . . . 21 8. Security considerations . . . . . . . . . . . . . . . . . . . 22
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 22
11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 22 11. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 22
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
12.1. Normative References . . . . . . . . . . . . . . . . . . 23 12.1. Normative References . . . . . . . . . . . . . . . . . . 24
12.2. Informative References . . . . . . . . . . . . . . . . . 25 12.2. Informative References . . . . . . . . . . . . . . . . . 26
12.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 26 12.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Appendix A. Documents . . . . . . . . . . . . . . . . . . . . . 27 Appendix A. Documents . . . . . . . . . . . . . . . . . . . . . 29
A.1. Potential increases in DNS privacy . . . . . . . . . . . 27 A.1. Potential increases in DNS privacy . . . . . . . . . . . 29
A.2. Potential decreases in DNS privacy . . . . . . . . . . . 28 A.2. Potential decreases in DNS privacy . . . . . . . . . . . 29
A.3. Related operational documents . . . . . . . . . . . . . . 28 A.3. Related operational documents . . . . . . . . . . . . . . 30
Appendix B. Encryption and DNSSEC . . . . . . . . . . . . . . . 29 Appendix B. Encryption and DNSSEC . . . . . . . . . . . . . . . 30
Appendix C. IP address techniques . . . . . . . . . . . . . . . 29 Appendix C. IP address techniques . . . . . . . . . . . . . . . 30
C.1. Google Analytics non-prefix filtering . . . . . . . . . . 30 C.1. Google Analytics non-prefix filtering . . . . . . . . . . 31
C.2. dnswasher . . . . . . . . . . . . . . . . . . . . . . . . 30 C.2. dnswasher . . . . . . . . . . . . . . . . . . . . . . . . 32
C.3. Prefix-preserving map . . . . . . . . . . . . . . . . . . 31 C.3. Prefix-preserving map . . . . . . . . . . . . . . . . . . 32
C.4. Cryptographic Prefix-Preserving Pseudonymisation . . . . 31 C.4. Cryptographic Prefix-Preserving Pseudonymisation . . . . 32
C.5. Top-hash Subtree-replicated Anonymisation . . . . . . . . 31 C.5. Top-hash Subtree-replicated Anonymisation . . . . . . . . 33
C.6. ipcipher . . . . . . . . . . . . . . . . . . . . . . . . 32 C.6. ipcipher . . . . . . . . . . . . . . . . . . . . . . . . 33
C.7. Bloom filters . . . . . . . . . . . . . . . . . . . . . . 32 C.7. Bloom filters . . . . . . . . . . . . . . . . . . . . . . 33
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34
1. Introduction 1. Introduction
The Domain Name System (DNS) is at the core of the Internet; almost The Domain Name System (DNS) is at the core of the Internet; almost
every activity on the Internet starts with a DNS query (and often every activity on the Internet starts with a DNS query (and often
several). However the DNS was not originally designed with strong several). However the DNS was not originally designed with strong
security or privacy mechanisms. A number of developments have taken security or privacy mechanisms. A number of developments have taken
place in recent years which aim to increase the privacy of the DNS place in recent years which aim to increase the privacy of the DNS
system and these are now seeing some deployment. This latest system and these are now seeing some deployment. This latest
evolution of the DNS presents new challenges to operators and this evolution of the DNS presents new challenges to operators and this
document attempts to provide an overview of considerations for document attempts to provide an overview of considerations for
privacy focused DNS services. privacy focused DNS services.
In recent years there has also been an increase in the availability In recent years there has also been an increase in the availability
of "open resolvers" [I-D.ietf-dnsop-terminology-bis] which users may of "public resolvers" [I-D.ietf-dnsop-terminology-bis] which users
prefer to use instead of the default network resolver because they may prefer to use instead of the default network resolver because
offer a specific feature (e.g. good reachability, encrypted they offer a specific feature (e.g. good reachability, encrypted
transport, strong privacy policy, filtering (or lack of), etc.). transport, strong privacy policy, filtering (or lack of), etc.).
These open resolvers have tended to be at the forefront of adoption These open resolvers have tended to be at the forefront of adoption
of privacy related enhancements but it is anticipated that operators of privacy related enhancements but it is anticipated that operators
of other resolver services will follow. of other resolver services will follow.
Whilst protocols that encrypt DNS messages on the wire provide Whilst protocols that encrypt DNS messages on the wire provide
protection against certain attacks, the resolver operator still has protection against certain attacks, the resolver operator still has
(in principle) full visibility of the query data and transport (in principle) full visibility of the query data and transport
identifiers for each user. Therefore, a trust relationship exists. identifiers for each user. Therefore, a trust relationship exists.
The ability of the operator to provide a transparent, well The ability of the operator to provide a transparent, well
skipping to change at page 4, line 12 skipping to change at page 4, line 12
differentiating factor for privacy conscious users if they make an differentiating factor for privacy conscious users if they make an
active selection of which resolver to use. active selection of which resolver to use.
It should also be noted that the choice of a user to configure a It should also be noted that the choice of a user to configure a
single resolver (or a fixed set of resolvers) and an encrypted single resolver (or a fixed set of resolvers) and an encrypted
transport to use in all network environments has both advantages and transport to use in all network environments has both advantages and
disadvantages. For example the user has a clear expectation of which disadvantages. For example the user has a clear expectation of which
resolvers have visibility of their query data however this resolver/ resolvers have visibility of their query data however this resolver/
transport selection may provide an added mechanism to track them as transport selection may provide an added mechanism to track them as
they move across network environments. Commitments from operators to they move across network environments. Commitments from operators to
minimize such tracking are also likely to play a role in users minimize such tracking are also likely to play a role in user
selection of resolver. selection of resolvers.
More recently the global legislative landscape with regard to More recently the global legislative landscape with regard to
personal data collection, retention, and pseudonymization has seen personal data collection, retention, and pseudonymization has seen
significant activity. It is an untested area that simply using a DNS significant activity. It is an untested area that simply using a DNS
resolution service constitutes consent from the user for the operator resolution service constitutes consent from the user for the operator
to process their query data. The impact of recent legislative to process their query data. The impact of recent legislative
changes on data pertaining to the users of both Internet Service changes on data pertaining to the users of both Internet Service
Providers and DNS open resolvers is not fully understood at the time Providers and public DNS resolvers is not fully understood at the
of writing. time of writing.
This document has two main goals: This document has two main goals:
o To provide operational and policy guidance related to DNS over o To provide operational and policy guidance related to DNS over
encrypted transports and to outline recommendations for data encrypted transports and to outline recommendations for data
handling for operators of DNS privacy services. handling for operators of DNS privacy services.
o To introduce the DNS Privacy Policy and Practice Statement (DPPPS) o To introduce the DNS Privacy Policy and Practice Statement (DPPPS)
and present a framework to assist writers of this document. A and present a framework to assist writers of this document. A
DPPPS is a document that an operator can publish outlining their DPPPS is a document that an operator can publish outlining their
skipping to change at page 6, line 20 skipping to change at page 6, line 20
enabling DNS server and is documented either in an informal enabling DNS server and is documented either in an informal
statement of policy and practice with regard to users privacy or a statement of policy and practice with regard to users privacy or a
formal DPPPS. formal DPPPS.
5. Recommendations for DNS privacy services 5. Recommendations for DNS privacy services
We describe two classes of threats: We describe two classes of threats:
o 'Privacy Considerations for Internet Protocols' [RFC6973] Threats o 'Privacy Considerations for Internet Protocols' [RFC6973] Threats
* Privacy terminology, threats to privacy and mitigations are * Privacy terminology, threats to privacy and mitigations as
described in Sections 3, 5 and 6 of [RFC6973]. described in Sections 3, 5 and 6 of [RFC6973].
o DNS Privacy Threats o DNS Privacy Threats
* These are threats to the users and operators of DNS privacy * These are threats to the users and operators of DNS privacy
services that are not directly covered by [RFC6973]. These may services that are not directly covered by [RFC6973]. These may
be more operational in nature such as certificate management or be more operational in nature such as certificate management or
service availability issues. service availability issues.
We describe three classes of actions that operators of DNS privacy We describe three classes of actions that operators of DNS privacy
skipping to change at page 7, line 39 skipping to change at page 7, line 39
o DoH [RFC8484] o DoH [RFC8484]
It is noted that a DNS privacy service can also be provided over DNS- It is noted that a DNS privacy service can also be provided over DNS-
over-DTLS [RFC8094], however this is an Experimental specification over-DTLS [RFC8094], however this is an Experimental specification
and there are no known implementations at the time of writing. and there are no known implementations at the time of writing.
It is also noted that DNS privacy service might be provided over It is also noted that DNS privacy service might be provided over
IPSec, DNSCrypt or VPNs. However, use of these transports for DNS IPSec, DNSCrypt or VPNs. However, use of these transports for DNS
are not standardized and any discussion of best practice for are not standardized and any discussion of best practice for
providing such service is out of scope for this document. providing such a service is out of scope for this document.
Whilst encryption of DNS traffic can protect against active injection Whilst encryption of DNS traffic can protect against active injection
this does not diminish the need for DNSSEC, see Appendix B. this does not diminish the need for DNSSEC, see Appendix B.
5.1.2. Authentication of DNS privacy services 5.1.2. Authentication of DNS privacy services
[RFC6973] Threats: [RFC6973] Threats:
o Surveillance: o Surveillance:
skipping to change at page 8, line 15 skipping to change at page 8, line 15
Mitigations: Mitigations:
DNS privacy services should ensure clients can authenticate the DNS privacy services should ensure clients can authenticate the
server. Note that this, in effect, commits the DNS privacy service server. Note that this, in effect, commits the DNS privacy service
to a public identity users will trust. to a public identity users will trust.
When using DNS-over-TLS clients that select a 'Strict Privacy' usage When using DNS-over-TLS clients that select a 'Strict Privacy' usage
profile [RFC8310] (to mitigate the threat of active attack on the profile [RFC8310] (to mitigate the threat of active attack on the
client) require the ability to authenticate the DNS server. To client) require the ability to authenticate the DNS server. To
enable this, DNS privacy services that offer DNS-over-TLS should enable this, DNS privacy services that offer DNS-over-TLS should
provide credentials in the form of either X.509 certificates, SPKI provide credentials in the form of either X.509 certificates or SPKI
pinsets or TLSA records. pinsets.
When offering DoH [RFC8484], HTTPS requires authentication of the When offering DoH [RFC8484], HTTPS requires authentication of the
server as part of the protocol. server as part of the protocol.
NOTE: At this time the reference to the TLS DNSSEC chain extension NOTE: At this time the reference to the TLS DNSSEC chain extension
draft has been removed as it is no longer considered an active TLS WG draft has been removed as it is no longer considered an active TLS WG
document. document.
Optimizations: Optimizations:
skipping to change at page 10, line 23 skipping to change at page 10, line 23
[RFC7766]. This is often called 'OOOR' - out-of-order responses. [RFC7766]. This is often called 'OOOR' - out-of-order responses.
(Providing processing performance similar to HTTP multiplexing) (Providing processing performance similar to HTTP multiplexing)
o Management of TLS connections to optimize performance for clients o Management of TLS connections to optimize performance for clients
using either using either
* [RFC7766] and EDNS(0) Keepalive [RFC7828] and/or * [RFC7766] and EDNS(0) Keepalive [RFC7828] and/or
* DNS Stateful Operations [I-D.ietf-dnsop-session-signal] * DNS Stateful Operations [I-D.ietf-dnsop-session-signal]
o Offer a separate service that uses only TLS 1.3 [RFC8446]
Additional options that providers may consider: Additional options that providers may consider:
o Offer a .onion [RFC7686] service endpoint o Offer a .onion [RFC7686] service endpoint
5.1.3.2. DoH 5.1.3.2. DoH
DNS Privacy Threats: DNS Privacy Threats:
o Known attacks on TLS such as those described in [RFC7457] o Known attacks on TLS such as those described in [RFC7457]
o Traffic analysis, for example: DNS Privacy not so private: the o Traffic analysis, for example: DNS Privacy not so private: the
traffic analysis perspective [2] traffic analysis perspective [2]
o Potential for client tracking via transport identifiers o Potential for client tracking via transport identifiers
Mitigations: Mitigations:
o Clients should not be required to use HTTP Cookies [RFC6265]. o Clients must be able to forego the use of HTTP Cookies [RFC6265]
and still use the service
o Clients should not be required to include any headers beyond the o Clients should not be required to include any headers beyond the
absolute minimum to obtain service from a DoH server. (Some absolute minimum to obtain service from a DoH server. (See
initial work in this area has been proposed Section 6.1 of [I-D.ietf-httpbis-bcp56bis].)
[I-D.dickinson-doh-dohpe] but there are no clear guidelines for
HTTP header privacy, more work on this topic is required.)
Optimizations:
o Offer a separate service that uses only TLS 1.3 [RFC8446]
5.1.4. Availability 5.1.4. Availability
DNS Privacy Threats: DNS Privacy Threats:
o A failed DNS privacy service could force the user to switch o A failed DNS privacy service could force the user to switch
providers, fallback to cleartext or accept no DNS service for the providers, fallback to cleartext or accept no DNS service for the
outage. outage.
Mitigations: Mitigations:
A DNS privacy service must be engineered for high availability. A DNS privacy service must be engineered for high availability.
Particular care should to be taken to protect DNS privacy services Particular care should to be taken to protect DNS privacy services
against denial-of-service attacks, as experience has shown that against denial-of-service attacks, as experience has shown that
unavailability of DNS resolving because of attacks is a significant unavailability of DNS resolving because of attacks is a significant
motivation for users to switch services. motivation for users to switch services. See, for example
Section IV-C of Passive Observations of a Large DNS Service: 2.5
TODO: Add reference to ongoing research on this topic. Years in the Life of Google [3].
5.1.5. Service options 5.1.5. Service options
DNS Privacy Threats: DNS Privacy Threats:
o Unfairly disadvantaging users of the privacy service with respect o Unfairly disadvantaging users of the privacy service with respect
to the services available. This could force the user to switch to to the services available. This could force the user to switch
the services available. providers, fallback to cleartext or accept providers, fallback to cleartext or accept no DNS service for the
no DNS service for the outage. outage.
Mitigations: Mitigations:
A DNS privacy service should deliver the same level of service as A DNS privacy service should deliver the same level of service as
offered on un-encrypted channels in terms of such options as offered on un-encrypted channels in terms of such options as
filtering (or lack of), DNSSEC validation, etc. filtering (or lack thereof), DNSSEC validation, etc.
5.1.6. Impact on Operators 5.1.6. Impact on Operators
DNS Privacy Threats: DNS Privacy Threats:
o Increased use of encryption impacts operator ability to manage o Increased use of encryption impacts operator ability to manage
their network [RFC8404] their network [RFC8404]
Many monitoring solutions for DNS traffic rely on the plain text
nature of this traffic and work by intercepting traffic on the wire,
either using a separate view on the connection between clients and
the resolver, or as a separate process on the resolver system that
inspects network traffic. Such solutions will no longer function
when traffic between clients and resolvers is encrypted. There are,
however, legitimate reasons for operators to inspect DNS traffic,
e.g. to monitor for network security threats. Operators may
therefore need to invest in alternative means of monitoring that
relies on either the resolver software directly, or exporting DNS
traffic from the resolver using e.g. dnstap [4].
Optimization:
When implementing alternative means for traffic monitoring, operators
of a DNS privacy service should consider using privacy conscious
means to do so (see, for example, the discussion on the use of Bloom
Filters in the #documents appendix in this document).
5.1.7. Limitations of using a pure TLS proxy 5.1.7. Limitations of using a pure TLS proxy
DNS Privacy Threats: DNS Privacy Threats:
o Limited ability to manage or monitor incoming connections using o Limited ability to manage or monitor incoming connections using
DNS specific techniques DNS specific techniques
o Misconfiguration of the target server could lead to data leakage
if the proxy to target server path is not encrypted.
Optimization: Optimization:
Some operators may choose to implement DNS-over-TLS using a TLS proxy Some operators may choose to implement DNS-over-TLS using a TLS proxy
(e.g. nginx [3], haproxy [4] or stunnel [5]) in front of a DNS (e.g. nginx [5], haproxy [6] or stunnel [7]) in front of a DNS
nameserver because of proven robustness and capacity when handling nameserver because of proven robustness and capacity when handling
large numbers of client connections, load balancing capabilities and large numbers of client connections, load balancing capabilities and
good tooling. Currently, however, because such proxies typically good tooling. Currently, however, because such proxies typically
have no specific handling of DNS as a protocol over TLS or DTLS using have no specific handling of DNS as a protocol over TLS or DTLS using
them can restrict traffic management at the proxy layer and at the them can restrict traffic management at the proxy layer and at the
DNS server. For example, all traffic received by a nameserver behind DNS server. For example, all traffic received by a nameserver behind
such a proxy will appear to originate from the proxy and DNS such a proxy will appear to originate from the proxy and DNS
techniques such as ACLs, RRL or DNS64 will be hard or impossible to techniques such as ACLs, RRL or DNS64 will be hard or impossible to
implement in the nameserver. implement in the nameserver.
Operators may choose to use a DNS aware proxy such as dnsdist. Operators may choose to use a DNS aware proxy such as dnsdist [8]
which offer custom options (similar to that proposed in
[I-D.bellis-dnsop-xpf]) to add source information to packets to
address this shortcoming. It should be noted that such options
potentially significantly increase the leaked information in the
event of a misconfiguration.
5.2. Data at rest on the server 5.2. Data at rest on the server
5.2.1. Data handling 5.2.1. Data handling
[RFC6973] Threats: [RFC6973] Threats:
o Surveillance o Surveillance
o Stored data compromise o Stored data compromise
skipping to change at page 12, line 28 skipping to change at page 13, line 4
5.2. Data at rest on the server 5.2. Data at rest on the server
5.2.1. Data handling 5.2.1. Data handling
[RFC6973] Threats: [RFC6973] Threats:
o Surveillance o Surveillance
o Stored data compromise o Stored data compromise
o Correlation o Correlation
o Identification o Identification
o Secondary use o Secondary use
o Disclosure o Disclosure
Other Treats Other Threats
o Contravention of legal requirements not to process user data? o Contravention of legal requirements not to process user data?
Mitigations: Mitigations:
The following are common activities for DNS service operators and in The following are common activities for DNS service operators and in
all cases should be minimized or completely avoided if possible for all cases should be minimized or completely avoided if possible for
DNS privacy services. If data is retained it should be encrypted and DNS privacy services. If data is retained it should be encrypted and
either aggregated, pseudonymized or anonymized whenever possible. In either aggregated, pseudonymized or anonymized whenever possible. In
general the principle of data minimization described in [RFC6973] general the principle of data minimization described in [RFC6973]
skipping to change at page 14, line 8 skipping to change at page 14, line 30
the decade. Developments over the last decade have been both a the decade. Developments over the last decade have been both a
blessing and a curse; the large increase in size between an IPv4 and blessing and a curse; the large increase in size between an IPv4 and
an IPv6 address, for example, renders some techniques impractical, an IPv6 address, for example, renders some techniques impractical,
but also makes available a much larger amount of input entropy, the but also makes available a much larger amount of input entropy, the
better to resist brute force re-identification attacks that have better to resist brute force re-identification attacks that have
grown in practicality over the period. grown in practicality over the period.
Techniques employed may be broadly categorized as either Techniques employed may be broadly categorized as either
anonymization or pseudonymization. The following discussion uses the anonymization or pseudonymization. The following discussion uses the
definitions from [RFC6973] Section 3, with additional observations definitions from [RFC6973] Section 3, with additional observations
from van Dijkhuizen et al. [6] from van Dijkhuizen et al. [9]
o Anonymization. To enable anonymity of an individual, there must o Anonymization. To enable anonymity of an individual, there must
exist a set of individuals that appear to have the same exist a set of individuals that appear to have the same
attribute(s) as the individual. To the attacker or the observer, attribute(s) as the individual. To the attacker or the observer,
these individuals must appear indistinguishable from each other. these individuals must appear indistinguishable from each other.
o Pseudonymization. The true identity is deterministically replaced o Pseudonymization. The true identity is deterministically replaced
with an alternate identity (a pseudonym). When the with an alternate identity (a pseudonym). When the
pseudonymization schema is known, the process can be reversed, so pseudonymization schema is known, the process can be reversed, so
the original identity becomes known again. the original identity becomes known again.
skipping to change at page 14, line 35 skipping to change at page 15, line 9
5.2.3. IP address pseudonymization and anonymization methods 5.2.3. IP address pseudonymization and anonymization methods
As [I-D.bortzmeyer-dprive-rfc7626-bis] makes clear, the big privacy As [I-D.bortzmeyer-dprive-rfc7626-bis] makes clear, the big privacy
risk in DNS is connecting DNS queries to an individual and the major risk in DNS is connecting DNS queries to an individual and the major
vector for this in DNS traffic is the client IP address. vector for this in DNS traffic is the client IP address.
There is active discussion in the space of effective pseudonymization There is active discussion in the space of effective pseudonymization
of IP addresses in DNS traffic logs, however there seems to be no of IP addresses in DNS traffic logs, however there seems to be no
single solution that is widely recognized as suitable for all or most single solution that is widely recognized as suitable for all or most
use cases. There are also as yet no standards for this that are use cases. There are also as yet no standards for this that are
unencumbered by patents. This following table presents a high level unencumbered by patents. The following table presents a high level
comparison of various techniques employed or under development today comparison of various techniques employed or under development today
and classifies them according to categorization of technique and and classifies them according to categorization of technique and
other properties. The list of techniques includes the main other properties. The list of techniques includes the main
techniques in current use, but does not claim to be comprehensive. techniques in current use, but does not claim to be comprehensive.
Appendix C provides a more detailed survey of these techniques and Appendix C provides a more detailed survey of these techniques and
definitions for the categories and properties listed below. definitions for the categories and properties listed below.
Figure showing comparison of IP address techniques (SVG) [7] Figure showing comparison of IP address techniques (SVG) [10]
The choice of which method to use for a particular application will The choice of which method to use for a particular application will
depend on the requirements of that application and consideration of depend on the requirements of that application and consideration of
the threat analysis of the particular situation. the threat analysis of the particular situation.
For example, a common goal is that distributed packet captures must For example, a common goal is that distributed packet captures must
be in an existing data format such as PCAP [pcap] or C-DNS be in an existing data format such as PCAP [pcap] or C-DNS
[I-D.ietf-dnsop-dns-capture-format] that can be used as input to [I-D.ietf-dnsop-dns-capture-format] that can be used as input to
existing analysis tools. In that case, use of a Format-preserving existing analysis tools. In that case, use of a format-preserving
technique is essential. This, though, is not cost-free - several technique is essential. This, though, is not cost-free - several
authors (e.g. Brenker & Arnes [8]) have observed that, as the authors (e.g. Brenker & Arnes [11]) have observed that, as the
entropy in a IPv4 address is limited, given a de-identified log from entropy in an IPv4 address is limited, given a de-identified log from
a target, if an attacker is capable of ensuring packets are captured a target, if an attacker is capable of ensuring packets are captured
by the target and the attacker can send forged traffic with arbitrary by the target and the attacker can send forged traffic with arbitrary
source and destination addresses to that target, any format- source and destination addresses to that target, any format-
preserving pseudonymization is vulnerable to an attack along the preserving pseudonymization is vulnerable to an attack along the
lines of a cryptographic chosen plaintext attack. lines of a cryptographic chosen plaintext attack.
5.2.4. Pseudonymization, anonymization or discarding of other 5.2.4. Pseudonymization, anonymization or discarding of other
correlation data correlation data
DNS Privacy Threats: DNS Privacy Threats:
skipping to change at page 15, line 45 skipping to change at page 16, line 19
5.2.5. Cache snooping 5.2.5. Cache snooping
[RFC6973] Threats: [RFC6973] Threats:
o Surveillance: o Surveillance:
* Profiling of client queries by malicious third parties * Profiling of client queries by malicious third parties
Mitigations: Mitigations:
o See ISC Knowledge database on cache snooping [9] for an example o See ISC Knowledge database on cache snooping [12] for an example
discussion on defending against cache snooping discussion on defending against cache snooping
TODO: Describe other techniques to defend against cache snooping TODO: Describe other techniques to defend against cache snooping
5.3. Data sent onwards from the server 5.3. Data sent onwards from the server
In this section we consider both data sent on the wire in upstream In this section we consider both data sent on the wire in upstream
queries and data shared with third parties. queries and data shared with third parties.
5.3.1. Protocol recommendations 5.3.1. Protocol recommendations
skipping to change at page 18, line 23 skipping to change at page 18, line 41
without explicit consent from clients (we take the stance here that without explicit consent from clients (we take the stance here that
simply using the resolution service itself does not constitute simply using the resolution service itself does not constitute
consent). consent).
Even when consent is granted operators should employ data Even when consent is granted operators should employ data
minimization techniques such as those described in Section 5.2.1 if minimization techniques such as those described in Section 5.2.1 if
data is shared with third-parties. data is shared with third-parties.
Operators should consider including specific guidelines for the Operators should consider including specific guidelines for the
collection of aggregated and/or anonymized data for research collection of aggregated and/or anonymized data for research
purposes, within or outside of their own organization. purposes, within or outside of their own organization. See SURFnet's
policy [13] on data sharing for research as an example.
TODO: More on data for research vs operations... how to still TODO: More on data for research vs operations... how to still
motivate operators to share anonymized data? motivate operators to share anonymized data?
TODO: Guidelines for when consent is granted? TODO: Guidelines for when consent is granted?
TODO: Applies to server data handling too.. could operators offer TODO: Applies to server data handling too.. could operators offer
alternatives services one that implies consent for data processing, alternatives services one that implies consent for data processing,
one that doesn't? one that doesn't?
skipping to change at page 18, line 45 skipping to change at page 19, line 16
6.1. Recommended contents of a DPPPS 6.1. Recommended contents of a DPPPS
6.1.1. Policy 6.1.1. Policy
1. Make an explicit statement that IP addressses are treated as PII 1. Make an explicit statement that IP addressses are treated as PII
2. State if IP addresses are being logged 2. State if IP addresses are being logged
3. Specify clearly what data (including whether it is aggregated, 3. Specify clearly what data (including whether it is aggregated,
pseudonymized or anonymized) is: pseudonymized or anonymized and the conditions of data transfer)
is:
* Collected and retained by the operator (and for how long) * Collected and retained by the operator, and for what period it
is retained
* Shared with partners * Shared with partners
* Shared, sold or rented to third-parties * Shared, sold or rented to third-parties
4. Specify any exceptions to the above, for example technically 4. Specify any exceptions to the above, for example technically
malicious or anomalous behavior malicious or anomalous behavior
5. Declare any partners, third-party affiliations or sources of 5. Declare any partners, third-party affiliations or sources of
funding funding
skipping to change at page 19, line 38 skipping to change at page 20, line 12
mandatory legal reasons, due to applicable legislation or mandatory legal reasons, due to applicable legislation or
binding orders by courts and other public authorities binding orders by courts and other public authorities
* Specify if any replies are being filtered out or altered for * Specify if any replies are being filtered out or altered for
voluntary legal reasons, due to an internal policy by the voluntary legal reasons, due to an internal policy by the
operator aiming at reducing potential legal risks operator aiming at reducing potential legal risks
* Specify if any replies are being filtered out or altered for * Specify if any replies are being filtered out or altered for
any other reason, including commercial ones any other reason, including commercial ones
6.1.2. Practice. 6.1.2. Practice
This section should explain the current operational practices of the This section should explain the current operational practices of the
service. service.
1. Specify any temporary or permanent deviations from the policy for 1. Specify any temporary or permanent deviations from the policy for
operational reasons operational reasons
2. With reference to section Section 5 provide specific details of 2. With reference to section Section 5 provide specific details of
which capabilities are provided on which client facing address which capabilities are provided on which client facing addresses
and ports and ports
3. Specify the authentication name to be used (if any) and if TLSA 3. Specify the authentication name to be used (if any) and if TLSA
records are published (including options used in the TLSA records are published (including options used in the TLSA
records) records)
4. Specify the SPKI pinsets to be used (if any) and policy for 4. Specify the SPKI pinsets to be used (if any) and policy for
rolling keys rolling keys
5. Provide contact/support information for the service 5. Provide contact/support information for the service
skipping to change at page 20, line 42 skipping to change at page 21, line 17
dealing with security and intelligence, to give them access to dealing with security and intelligence, to give them access to
the servers and/or to the data the servers and/or to the data
7. Describe how consent is obtained from the user of the DNS privacy 7. Describe how consent is obtained from the user of the DNS privacy
service differentiating service differentiating
* Uninformed users for whom this trust relationship is implicit * Uninformed users for whom this trust relationship is implicit
* Privacy-conscious users, that make an explicit trust choice * Privacy-conscious users, that make an explicit trust choice
this may prove relevant in the context of e.g. the GDPR as it relates (this may prove relevant in the context of e.g. the GDPR as it
to consent. relates to consent)
6.2. Current policy and privacy statements 6.2. Current policy and privacy statements
A tabular comparison of existing policy and privacy statements from A tabular comparison of existing policy and privacy statements from
various DNS Privacy service operators based on the proposed DPPPS various DNS Privacy service operators based on the proposed DPPPS
structure can be found on dnsprivacy.org [10]. structure can be found on dnsprivacy.org [14].
We note that the existing set of policies vary widely in style, We note that the existing set of policies vary widely in style,
content and detail and it is not uncommon for the full text for a content and detail and it is not uncommon for the full text for a
given operator to equate to more than 10 pages of moderate font sized given operator to equate to more than 10 pages of moderate font sized
A4 text. It is a non-trivial task today for a user to extract a A4 text. It is a non-trivial task today for a user to extract a
meaningful overview of the different services on offer. meaningful overview of the different services on offer.
6.3. Enforcement/accountability 6.3. Enforcement/accountability
Transparency reports may help with building user trust that operators Transparency reports may help with building user trust that operators
skipping to change at page 21, line 23 skipping to change at page 21, line 47
Independent monitoring or analysis could be performed where possible Independent monitoring or analysis could be performed where possible
of: of:
o ECS, QNAME minimization, EDNS(0) padding, etc. o ECS, QNAME minimization, EDNS(0) padding, etc.
o Filtering o Filtering
o Uptime o Uptime
This is by analogy with e.g. several TLS or website analysis tools This is by analogy with e.g. several TLS or website analysis tools
that are currently available e.g. SSL Labs [11] or Internet.nl [12]. that are currently available e.g. SSL Labs [15] or Internet.nl [16].
Additionally operators could choose to engage the services of a third Additionally operators could choose to engage the services of a third
party auditor to verify their compliance with their published DPPPS. party auditor to verify their compliance with their published DPPPS.
7. IANA considerations 7. IANA considerations
None None
8. Security considerations 8. Security considerations
skipping to change at page 22, line 25 skipping to change at page 22, line 48
Jim Hague Jim Hague
Sinodun Internet Technologies Sinodun Internet Technologies
Magdalen Centre Magdalen Centre
Oxford Science Park Oxford Science Park
Oxford OX4 4GA Oxford OX4 4GA
United Kingdom United Kingdom
11. Changelog 11. Changelog
draft-ietf-dprive-bcp-op-02
o Change 'open resolver' for 'public resolver'
o Minor editorial changes
o Remove recommendation to run a separate TLS 1.3 service
o Move TLSA to purely a optimisation in Section 5.2.1
o Update reference on minimal DoH headers.
o Add reference on user switching provider after service issues in
Section 5.1.4
o Add text in Section 5.1.6 on impact on operators.
o Add text on additional threat to TLS proxy use (Section 5.1.7)
o Add reference in Section 5.3.1 on example policies.
draft-ietf-dprive-bcp-op-01 draft-ietf-dprive-bcp-op-01
o Many minor editorial fixes o Many minor editorial fixes
o Update DoH reference to RFC8484 and add more text on DoH o Update DoH reference to RFC8484 and add more text on DoH
o Split threat descriptions into ones directly referencing RFC6973 o Split threat descriptions into ones directly referencing RFC6973
and other DNS Privacy threats and other DNS Privacy threats
o Improve threat descriptions throughout o Improve threat descriptions throughout
skipping to change at page 23, line 19 skipping to change at page 24, line 17
12.1. Normative References 12.1. Normative References
[I-D.ietf-dnsop-session-signal] [I-D.ietf-dnsop-session-signal]
Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S., Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S.,
Lemon, T., and T. Pusateri, "DNS Stateful Operations", Lemon, T., and T. Pusateri, "DNS Stateful Operations",
draft-ietf-dnsop-session-signal-20 (work in progress), draft-ietf-dnsop-session-signal-20 (work in progress),
December 2018. December 2018.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc2119>. editor.org/info/rfc2119>.
[RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig,
"Transport Layer Security (TLS) Session Resumption without "Transport Layer Security (TLS) Session Resumption without
Server-Side State", RFC 5077, DOI 10.17487/RFC5077, Server-Side State", RFC 5077, DOI 10.17487/RFC5077,
January 2008, <https://www.rfc-editor.org/info/rfc5077>. January 2008, <https://www.rfc-editor.org/info/rfc5077>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc6265>. editor.org/info/rfc6265>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J., [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973, Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013, DOI 10.17487/RFC6973, July 2013, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc6973>. editor.org/info/rfc6973>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer "Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>. 2015, <https://www.rfc-editor.org/info/rfc7525>.
[RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and [RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and
D. Wessels, "DNS Transport over TCP - Implementation D. Wessels, "DNS Transport over TCP - Implementation
Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016, Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,
<https://www.rfc-editor.org/info/rfc7766>. <https://www.rfc-editor.org/info/rfc7766>.
[RFC7816] Bortzmeyer, S., "DNS Query Name Minimisation to Improve [RFC7816] Bortzmeyer, S., "DNS Query Name Minimisation to Improve
Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016, Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016,
<https://www.rfc-editor.org/info/rfc7816>. <https://www.rfc-editor.org/info/rfc7816>.
[RFC7828] Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The [RFC7828] Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The
edns-tcp-keepalive EDNS0 Option", RFC 7828, edns-tcp-keepalive EDNS0 Option", RFC 7828,
DOI 10.17487/RFC7828, April 2016, DOI 10.17487/RFC7828, April 2016, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc7828>. editor.org/info/rfc7828>.
[RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830, [RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830,
DOI 10.17487/RFC7830, May 2016, DOI 10.17487/RFC7830, May 2016, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc7830>. editor.org/info/rfc7830>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D., [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>. 2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W. [RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.
Kumari, "Client Subnet in DNS Queries", RFC 7871, Kumari, "Client Subnet in DNS Queries", RFC 7871,
DOI 10.17487/RFC7871, May 2016, DOI 10.17487/RFC7871, May 2016, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc7871>. editor.org/info/rfc7871>.
[RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS) [RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)
Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016, Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,
<https://www.rfc-editor.org/info/rfc7873>. <https://www.rfc-editor.org/info/rfc7873>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles [RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
for DNS over TLS and DNS over DTLS", RFC 8310, for DNS over TLS and DNS over DTLS", RFC 8310,
DOI 10.17487/RFC8310, March 2018, DOI 10.17487/RFC8310, March 2018, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc8310>. editor.org/info/rfc8310>.
[RFC8404] Moriarty, K., Ed. and A. Morton, Ed., "Effects of [RFC8404] Moriarty, K., Ed. and A. Morton, Ed., "Effects of
Pervasive Encryption on Operators", RFC 8404, Pervasive Encryption on Operators", RFC 8404,
DOI 10.17487/RFC8404, July 2018, DOI 10.17487/RFC8404, July 2018, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc8404>. editor.org/info/rfc8404>.
[RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
<https://www.rfc-editor.org/info/rfc8446>.
[RFC8467] Mayrhofer, A., "Padding Policies for Extension Mechanisms [RFC8467] Mayrhofer, A., "Padding Policies for Extension Mechanisms
for DNS (EDNS(0))", RFC 8467, DOI 10.17487/RFC8467, for DNS (EDNS(0))", RFC 8467, DOI 10.17487/RFC8467,
October 2018, <https://www.rfc-editor.org/info/rfc8467>. October 2018, <https://www.rfc-editor.org/info/rfc8467>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS [RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018, (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>. <https://www.rfc-editor.org/info/rfc8484>.
12.2. Informative References 12.2. Informative References
[I-D.bellis-dnsop-xpf]
Bellis, R., Dijk, P., and R. Gacogne, "DNS X-Proxied-For",
draft-bellis-dnsop-xpf-04 (work in progress), March 2018.
[I-D.bortzmeyer-dprive-rfc7626-bis] [I-D.bortzmeyer-dprive-rfc7626-bis]
Bortzmeyer, S. and S. Dickinson, "DNS Privacy Bortzmeyer, S. and S. Dickinson, "DNS Privacy
Considerations", draft-bortzmeyer-dprive-rfc7626-bis-01 Considerations", draft-bortzmeyer-dprive-rfc7626-bis-02
(work in progress), July 2018. (work in progress), January 2019.
[I-D.dickinson-doh-dohpe]
Dickinson, S. and W. Toorop, "DoHPE: DoH with Privacy
Enhancements", draft-dickinson-doh-dohpe-00 (work in
progress), July 2018.
[I-D.ietf-dnsop-dns-capture-format] [I-D.ietf-dnsop-dns-capture-format]
Dickinson, J., Hague, J., Dickinson, S., Manderson, T., Dickinson, J., Hague, J., Dickinson, S., Manderson, T.,
and J. Bond, "C-DNS: A DNS Packet Capture Format", draft- and J. Bond, "C-DNS: A DNS Packet Capture Format", draft-
ietf-dnsop-dns-capture-format-10 (work in progress), ietf-dnsop-dns-capture-format-10 (work in progress),
December 2018. December 2018.
[I-D.ietf-dnsop-dns-tcp-requirements] [I-D.ietf-dnsop-dns-tcp-requirements]
Kristoff, J. and D. Wessels, "DNS Transport over TCP - Kristoff, J. and D. Wessels, "DNS Transport over TCP -
Operational Requirements", draft-ietf-dnsop-dns-tcp- Operational Requirements", draft-ietf-dnsop-dns-tcp-
requirements-02 (work in progress), May 2018. requirements-03 (work in progress), January 2019.
[I-D.ietf-dnsop-terminology-bis] [I-D.ietf-dnsop-terminology-bis]
Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", draft-ietf-dnsop-terminology-bis-14 (work in Terminology", draft-ietf-dnsop-terminology-bis-14 (work in
progress), September 2018. progress), September 2018.
[I-D.ietf-httpbis-bcp56bis]
Nottingham, M., "Building Protocols with HTTP", draft-
ietf-httpbis-bcp56bis-08 (work in progress), November
2018.
[pcap] tcpdump.org, "PCAP", 2016, <http://www.tcpdump.org/>. [pcap] tcpdump.org, "PCAP", 2016, <http://www.tcpdump.org/>.
[Pitfalls-of-DNS-Encryption] [Pitfalls-of-DNS-Encryption]
Shulman, H., "Pretty Bad Privacy: Pitfalls of DNS Shulman, H., "Pretty Bad Privacy: Pitfalls of DNS
Encryption", 2014, <https://www.ietf.org/mail-archive/web/ Encryption", 2014, <https://www.ietf.org/mail-archive/web/
dns-privacy/current/pdfWqAIUmEl47.pdf>. dns-privacy/current/pdfWqAIUmEl47.pdf>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", Rose, "DNS Security Introduction and Requirements",
RFC 4033, DOI 10.17487/RFC4033, March 2005, RFC 4033, DOI 10.17487/RFC4033, March 2005,
skipping to change at page 26, line 16 skipping to change at page 27, line 21
Known Attacks on Transport Layer Security (TLS) and Known Attacks on Transport Layer Security (TLS) and
Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457, Datagram TLS (DTLS)", RFC 7457, DOI 10.17487/RFC7457,
February 2015, <https://www.rfc-editor.org/info/rfc7457>. February 2015, <https://www.rfc-editor.org/info/rfc7457>.
[RFC7686] Appelbaum, J. and A. Muffett, "The ".onion" Special-Use [RFC7686] Appelbaum, J. and A. Muffett, "The ".onion" Special-Use
Domain Name", RFC 7686, DOI 10.17487/RFC7686, October Domain Name", RFC 7686, DOI 10.17487/RFC7686, October
2015, <https://www.rfc-editor.org/info/rfc7686>. 2015, <https://www.rfc-editor.org/info/rfc7686>.
[RFC7706] Kumari, W. and P. Hoffman, "Decreasing Access Time to Root [RFC7706] Kumari, W. and P. Hoffman, "Decreasing Access Time to Root
Servers by Running One on Loopback", RFC 7706, Servers by Running One on Loopback", RFC 7706,
DOI 10.17487/RFC7706, November 2015, DOI 10.17487/RFC7706, November 2015, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc7706>. editor.org/info/rfc7706>.
[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram [RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094, Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017, DOI 10.17487/RFC8094, February 2017, <https://www.rfc-
<https://www.rfc-editor.org/info/rfc8094>. editor.org/info/rfc8094>.
[RFC8198] Fujiwara, K., Kato, A., and W. Kumari, "Aggressive Use of [RFC8198] Fujiwara, K., Kato, A., and W. Kumari, "Aggressive Use of
DNSSEC-Validated Cache", RFC 8198, DOI 10.17487/RFC8198, DNSSEC-Validated Cache", RFC 8198, DOI 10.17487/RFC8198,
July 2017, <https://www.rfc-editor.org/info/rfc8198>. July 2017, <https://www.rfc-editor.org/info/rfc8198>.
12.3. URIs 12.3. URIs
[1] https://www.ietf.org/mail-archive/web/dns-privacy/current/ [1] https://www.ietf.org/mail-archive/web/dns-privacy/current/
pdfWqAIUmEl47.pdf pdfWqAIUmEl47.pdf
[2] https://petsymposium.org/2018/files/hotpets/4-siby.pdf [2] https://petsymposium.org/2018/files/hotpets/4-siby.pdf
[3] https://nginx.org/ [3] http://tma.ifip.org/2018/wp-content/uploads/sites/3/2018/06/
tma2018_paper30.pdf
[4] https://www.haproxy.org/ [4] http://dnstap.info
[5] https://kb.isc.org/article/AA-01386/0/DNS-over-TLS.html [5] https://nginx.org/
[6] https://doi.org/10.1145/3182660 [6] https://www.haproxy.org/
[7] https://github.com/Sinodun/draft-dprive-bcp-op/blob/master/draft- [7] https://kb.isc.org/article/AA-01386/0/DNS-over-TLS.html
00/ip_techniques_table.svg
[8] https://pdfs.semanticscholar.org/7b34/12c951cebe71cd2cddac5fda164 [8] https://dnsdist.org
fb2138a44.pdf
[9] https://kb.isc.org/docs/aa-00482 [9] https://doi.org/10.1145/3182660
[10] https://dnsprivacy.org/wiki/display/DP/ [10] https://github.com/Sinodun/draft-dprive-bcp-op/blob/master/
draft-00/ip_techniques_table.svg
[11] https://pdfs.semanticscholar.org/7b34/12c951cebe71cd2cddac5fda16
4fb2138a44.pdf
[12] https://kb.isc.org/docs/aa-00482
[13] https://surf.nl/datasharing
[14] https://dnsprivacy.org/wiki/display/DP/
Comparison+of+policy+and+privacy+statements Comparison+of+policy+and+privacy+statements
[11] https://www.ssllabs.com/ssltest/ [15] https://www.ssllabs.com/ssltest/
[12] https://internet.nl [16] https://internet.nl
[13] https://support.google.com/analytics/answer/2763052?hl=en [17] https://support.google.com/analytics/answer/2763052?hl=en
[14] https://www.conversionworks.co.uk/blog/2017/05/19/anonymize-ip- [18] https://www.conversionworks.co.uk/blog/2017/05/19/anonymize-ip-
geo-impact-test/ geo-impact-test/
[15] https://github.com/edmonds/pdns/blob/master/pdns/dnswasher.cc [19] https://github.com/edmonds/pdns/blob/master/pdns/dnswasher.cc
[16] http://ita.ee.lbl.gov/html/contrib/tcpdpriv.html [20] http://ita.ee.lbl.gov/html/contrib/tcpdpriv.html
[17] http://an.kaist.ac.kr/~sbmoon/paper/intl-journal/2004-cn- [21] http://an.kaist.ac.kr/~sbmoon/paper/intl-journal/2004-cn-
anon.pdf anon.pdf
[18] https://www.cc.gatech.edu/computing/Telecomm/projects/cryptopan/ [22] https://www.cc.gatech.edu/computing/Telecomm/projects/cryptopan/
[19] http://mharvan.net/talks/noms-ip_anon.pdf [23] http://mharvan.net/talks/noms-ip_anon.pdf
[20] http://www.ecs.umass.edu/ece/wolf/pubs/ton2007.pdf [24] http://www.ecs.umass.edu/ece/wolf/pubs/ton2007.pdf
[21] https://medium.com/@bert.hubert/on-ip-address-encryption- [25] https://medium.com/@bert.hubert/on-ip-address-encryption-
security-analysis-with-respect-for-privacy-dabe1201b476 security-analysis-with-respect-for-privacy-dabe1201b476
[22] https://github.com/PowerDNS/ipcipher [26] https://github.com/PowerDNS/ipcipher
[23] https://github.com/veorq/ipcrypt [27] https://github.com/veorq/ipcrypt
[24] https://www.ietf.org/mail-archive/web/cfrg/current/msg09494.html [28] https://www.ietf.org/mail-archive/web/cfrg/current/msg09494.html
[25] https://tnc18.geant.org/core/presentation/127 [29] https://tnc18.geant.org/core/presentation/127
Appendix A. Documents Appendix A. Documents
This section provides an overview of some DNS privacy related This section provides an overview of some DNS privacy related
documents, however, this is neither an exhaustive list nor a documents, however, this is neither an exhaustive list nor a
definitive statement on the characteristic of the document. definitive statement on the characteristic of the document.
A.1. Potential increases in DNS privacy A.1. Potential increases in DNS privacy
These documents are limited in scope to communications between stub These documents are limited in scope to communications between stub
skipping to change at page 30, line 30 skipping to change at page 31, line 43
o Random substitution. As replacement, but using randomly generated o Random substitution. As replacement, but using randomly generated
replacement values. replacement values.
o Cryptographic permutation. Using a permutation function, such as o Cryptographic permutation. Using a permutation function, such as
a hash function or cryptographic block cipher, to generate a a hash function or cryptographic block cipher, to generate a
replacement de-identified value. replacement de-identified value.
C.1. Google Analytics non-prefix filtering C.1. Google Analytics non-prefix filtering
Since May 2010, Google Analytics has provided a facility [13] that Since May 2010, Google Analytics has provided a facility [17] that
allows website owners to request that all their users IP addresses allows website owners to request that all their users IP addresses
are anonymized within Google Analytics processing. This very basic are anonymized within Google Analytics processing. This very basic
anonymization simply sets to zero the least significant 8 bits of anonymization simply sets to zero the least significant 8 bits of
IPv4 addresses, and the least significant 80 bits of IPv6 addresses. IPv4 addresses, and the least significant 80 bits of IPv6 addresses.
The level of anonymization this produces is perhaps questionable. The level of anonymization this produces is perhaps questionable.
There are some analysis results [14] which suggest that the impact of There are some analysis results [18] which suggest that the impact of
this on reducing the accuracy of determining the user's location from this on reducing the accuracy of determining the user's location from
their IP address is less than might be hoped; the average discrepancy their IP address is less than might be hoped; the average discrepancy
in identification of the user city for UK users is no more than 17%. in identification of the user city for UK users is no more than 17%.
Anonymization: Format-preserving, Filtering (grey marking). Anonymization: Format-preserving, Filtering (grey marking).
C.2. dnswasher C.2. dnswasher
Since 2006, PowerDNS have included a de-identification tool dnswasher Since 2006, PowerDNS have included a de-identification tool dnswasher
[15] with their PowerDNS product. This is a PCAP filter that [19] with their PowerDNS product. This is a PCAP filter that
performs a one-to-one mapping of end user IP addresses with an performs a one-to-one mapping of end user IP addresses with an
anonymized address. A table of user IP addresses and their de- anonymized address. A table of user IP addresses and their de-
identified counterparts is kept; the first IPv4 user addresses is identified counterparts is kept; the first IPv4 user addresses is
translated to 0.0.0.1, the second to 0.0.0.2 and so on. The de- translated to 0.0.0.1, the second to 0.0.0.2 and so on. The de-
identified address therefore depends on the order that addresses identified address therefore depends on the order that addresses
arrive in the input, and running over a large amount of data the arrive in the input, and running over a large amount of data the
address translation tables can grow to a significant size. address translation tables can grow to a significant size.
Anonymization: Format-preserving, Enumeration. Anonymization: Format-preserving, Enumeration.
C.3. Prefix-preserving map C.3. Prefix-preserving map
Used in TCPdpriv [16], this algorithm stores a set of original and Used in TCPdpriv [20], this algorithm stores a set of original and
anonymised IP address pairs. When a new IP address arrives, it is anonymised IP address pairs. When a new IP address arrives, it is
compared with previous addresses to determine the longest prefix compared with previous addresses to determine the longest prefix
match. The new address is anonymized by using the same prefix, with match. The new address is anonymized by using the same prefix, with
the remainder of the address anonymized with a random value. The use the remainder of the address anonymized with a random value. The use
of a random value means that TCPdrpiv is not deterministic; different of a random value means that TCPdrpiv is not deterministic; different
anonymized values will be generated on each run. The need to store anonymized values will be generated on each run. The need to store
previous addresses means that TCPdpriv has significant and unbounded previous addresses means that TCPdpriv has significant and unbounded
memory requirements, and because of the need to allocated anonymized memory requirements, and because of the need to allocated anonymized
addresses sequentially cannot be used in parallel processing. addresses sequentially cannot be used in parallel processing.
Anonymization: Format-preserving, prefix preservation (general). Anonymization: Format-preserving, prefix preservation (general).
C.4. Cryptographic Prefix-Preserving Pseudonymisation C.4. Cryptographic Prefix-Preserving Pseudonymisation
Cryptographic prefix-preserving pseudonymisation was originally Cryptographic prefix-preserving pseudonymisation was originally
proposed as an improvement to the prefix-preserving map implemented proposed as an improvement to the prefix-preserving map implemented
in TCPdpriv, described in Xu et al. [17] and implemented in the in TCPdpriv, described in Xu et al. [21] and implemented in the
Crypto-PAn tool [18]. Crypto-PAn is now frequently used as an Crypto-PAn tool [22]. Crypto-PAn is now frequently used as an
acronym for the algorithm. Initially it was described for IPv4 acronym for the algorithm. Initially it was described for IPv4
addresses only; extension for IPv6 addresses was proposed in Harvan & addresses only; extension for IPv6 addresses was proposed in Harvan &
Schoenwaelder [19] and implemented in snmpdump. This uses a Schoenwaelder [23] and implemented in snmpdump. This uses a
cryptographic algorithm rather than a random value, and thus cryptographic algorithm rather than a random value, and thus
pseudonymity is determined uniquely by the encryption key, and is pseudonymity is determined uniquely by the encryption key, and is
deterministic. It requires a separate AES encryption for each output deterministic. It requires a separate AES encryption for each output
bit, so has a non-trivial calculation overhead. This can be bit, so has a non-trivial calculation overhead. This can be
mitigated to some extent (for IPv4, at least) by pre-calculating mitigated to some extent (for IPv4, at least) by pre-calculating
results for some number of prefix bits. results for some number of prefix bits.
Pseudonymization: Format-preserving, prefix preservation (general). Pseudonymization: Format-preserving, prefix preservation (general).
C.5. Top-hash Subtree-replicated Anonymisation C.5. Top-hash Subtree-replicated Anonymisation
Proposed in Ramaswamy & Wolf [20], Top-hash Subtree-replicated Proposed in Ramaswamy & Wolf [24], Top-hash Subtree-replicated
Anonymisation (TSA) originated in response to the requirement for Anonymisation (TSA) originated in response to the requirement for
faster processing than Crypto-PAn. It used hashing for the most faster processing than Crypto-PAn. It used hashing for the most
significant byte of an IPv4 address, and a pre-calculated binary tree significant byte of an IPv4 address, and a pre-calculated binary tree
structure for the remainder of the address. To save memory space, structure for the remainder of the address. To save memory space,
replication is used within the tree structure, reducing the size of replication is used within the tree structure, reducing the size of
the pre-calculated structures to a few Mb for IPv4 addresses. the pre-calculated structures to a few Mb for IPv4 addresses.
Address pseudonymization is done via hash and table lookup, and so Address pseudonymization is done via hash and table lookup, and so
requires minimal computation. However, due to the much increased requires minimal computation. However, due to the much increased
address space for IPv6, TSA is not memory efficient for IPv6. address space for IPv6, TSA is not memory efficient for IPv6.
Pseudonymization: Format-preserving, prefix preservation (general). Pseudonymization: Format-preserving, prefix preservation (general).
C.6. ipcipher C.6. ipcipher
A recently-released proposal from PowerDNS [21], ipcipher [22] is a A recently-released proposal from PowerDNS [25], ipcipher [26] is a
simple pseudonymization technique for IPv4 and IPv6 addresses. IPv6 simple pseudonymization technique for IPv4 and IPv6 addresses. IPv6
addresses are encrypted directly with AES-128 using a key (which may addresses are encrypted directly with AES-128 using a key (which may
be derived from a passphrase). IPv4 addresses are similarly be derived from a passphrase). IPv4 addresses are similarly
encrypted, but using a recently proposed encryption ipcrypt [23] encrypted, but using a recently proposed encryption ipcrypt [27]
suitable for 32bit block lengths. However, the author of ipcrypt has suitable for 32bit block lengths. However, the author of ipcrypt has
since indicated [24] that it has low security, and further analysis since indicated [28] that it has low security, and further analysis
has revealed it is vulnerable to attack. has revealed it is vulnerable to attack.
Pseudonymization: Format-preserving, cryptographic permutation. Pseudonymization: Format-preserving, cryptographic permutation.
C.7. Bloom filters C.7. Bloom filters
van Rijswijk-Deij et al. [25] have recently described work using van Rijswijk-Deij et al. [29] have recently described work using
Bloom filters to categorize query traffic and record the traffic as Bloom filters to categorize query traffic and record the traffic as
the state of multiple filters. The goal of this work is to allow the state of multiple filters. The goal of this work is to allow
operators to identify so-called Indicators of Compromise (IOCs) operators to identify so-called Indicators of Compromise (IOCs)
originating from specific subnets without storing information about, originating from specific subnets without storing information about,
or be able to monitor the DNS queries of an individual user. By or be able to monitor the DNS queries of an individual user. By
using a Bloom filter, it is possible to determine with a high using a Bloom filter, it is possible to determine with a high
probability if, for example, a particular query was made, but the set probability if, for example, a particular query was made, but the set
of queries made cannot be recovered from the filter. Similarly, by of queries made cannot be recovered from the filter. Similarly, by
mixing queries from a sufficient number of users in a single filter, mixing queries from a sufficient number of users in a single filter,
it becomes practically impossible to determine if a particular user it becomes practically impossible to determine if a particular user
 End of changes. 94 change blocks. 
155 lines changed or deleted 206 lines changed or added

This html diff was produced by rfcdiff 1.47. The latest version is available from http://tools.ietf.org/tools/rfcdiff/