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draft-huitema-dprive-dnsoquic-00.txt
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Network Working Group C. Huitema
Internet-Draft Private Octopus Inc.
Intended status: Standards Track A. Mankin
Expires: September 6, 2020 Salesforce
S. Dickinson
Sinodun IT
March 05, 2020
Specification of DNS over Dedicated QUIC Connections
draft-huitema-dprive-dnsoquic-00
Abstract
This document describes the use of QUIC to provide transport privacy
for DNS. The encryption provided by QUIC has similar properties to
that provided by TLS, while QUIC transport eliminates the head-of-
line blocking issues inherent with TCP and provides more efficient
error corrections than UDP. DNS over QUIC (DoQ) has privacy
properties similar to DNS over TLS (DoT) specified in RFC7858, and
performance characteristics similar to classic DNS over UDP.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 6, 2020.
Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
Huitema, et al. Expires September 6, 2020 [Page 1]
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Design Considerations . . . . . . . . . . . . . . . . . . . . 4
3.1. Scope is Limited to the Stub to Resolver Scenario . . . . 4
3.2. Provide DNS Privacy . . . . . . . . . . . . . . . . . . . 5
3.3. Design for Minimum Latency . . . . . . . . . . . . . . . 5
3.4. No Specific Middlebox Bypass Mechanism . . . . . . . . . 6
4. Specifications . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Connection Establishment . . . . . . . . . . . . . . . . 6
4.1.1. Draft Version Identification . . . . . . . . . . . . 6
4.1.2. Port Selection . . . . . . . . . . . . . . . . . . . 7
4.2. Stream Mapping and Usage . . . . . . . . . . . . . . . . 7
4.2.1. Server Initiated Transactions . . . . . . . . . . . . 8
4.2.2. Stream Reset . . . . . . . . . . . . . . . . . . . . 8
4.3. Connection Management . . . . . . . . . . . . . . . . . . 8
4.4. Connection Resume and 0-RTT . . . . . . . . . . . . . . . 9
5. Implementation Requirements . . . . . . . . . . . . . . . . . 9
5.1. Authentication . . . . . . . . . . . . . . . . . . . . . 9
5.2. Fall Back to Other Protocols on Connection Failure . . . 10
5.3. Address Validation . . . . . . . . . . . . . . . . . . . 10
5.4. Response Sizes . . . . . . . . . . . . . . . . . . . . . 10
5.5. DNS Message IDs . . . . . . . . . . . . . . . . . . . . . 11
5.6. Padding . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.7. Connection Handling . . . . . . . . . . . . . . . . . . . 11
5.7.1. Connection Reuse . . . . . . . . . . . . . . . . . . 11
5.7.2. Connection Close . . . . . . . . . . . . . . . . . . 12
5.7.3. Idle Timeouts . . . . . . . . . . . . . . . . . . . . 12
5.8. Flow Control Mechanisms . . . . . . . . . . . . . . . . . 13
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. Privacy Considerations . . . . . . . . . . . . . . . . . . . 13
7.1. Privacy Issues With Zero RTT data . . . . . . . . . . . . 13
7.2. Privacy Issues With Session Resume . . . . . . . . . . . 14
7.3. Traffic Analysis . . . . . . . . . . . . . . . . . . . . 14
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8.1. Registration of DoQ Identification String . . . . . . . . 15
8.2. Reservation of Dedicated Port . . . . . . . . . . . . . . 15
8.2.1. Port number 784 for experimentations . . . . . . . . 15
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . 16
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10.2. Informative References . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
Domain Name System (DNS) concepts are specified in [RFC1034]. This
document presents a mapping of the DNS protocol [RFC1035] over QUIC
transport [I-D.ietf-quic-transport] [I-D.ietf-quic-tls]. DNS over
QUIC is refered here as DoQ, in line with the terminology presented
in [I-D.ietf-dnsop-terminology-ter]. The goals of the DoQ mapping
are:
1. Provide the same DNS privacy protection as DNS over TLS (DoT)
[RFC7858]. This includes an option for the client to
authenticate the server by means of an authentication domain name
[RFC8310].
2. Provide an improved level of source address validation for DNS
servers compared to classic DNS over UDP [RFC1035].
3. Provide a transport that is not constrained by path MTU
limitations on the size of DNS responses it can send.
4. Explore the potential performance gains of using QUIC as a DNS
transport, versus other solutions like DNS over UDP (DNS/UDP)
[RFC1035] or DoT [RFC7858].
In order to achieve these goals, the focus of this document is
limited to the "stub to recursive resolver" scenario also addressed
by [RFC7858]. That is, the protocol described here works for queries
and responses between stub clients and recursive servers. The
specific non-goals of this document are:
1. No attempt is made to support zone transfers [RFC5936], as these
are not relevant to the stub to recursive resolver scenario.
2. No attempt is made to evade potential blocking of DNS/QUIC
traffic by middleboxes.
Users interested in zone transfers should continue using TCP based
solutions and will also want to take note of work in progress to
encrypt zone transfers using DoT [I-D.ietf-dprive-xfr-over-tls].
Users interested in evading middleboxes should consider using
solutions like DNS/HTTPS [RFC8484].
Specifying the transmission of an application over QUIC requires
specifying how the application's messages are mapped to QUIC streams,
and generally how the application will use QUIC. This is done for
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HTTP in [I-D.ietf-quic-http]. The purpose of this document is to
define the way DNS messages can be transmitted over QUIC.
In this document, Section 3 presents the reasoning that guided the
proposed design. Section 4 specifies the actual mapping of DoQ.
Section 5 presents guidelines on the implementation, usage and
deployment of DoQ.
2. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC8174].
3. Design Considerations
This section and its subsection present the design guidelines that
were used for DoQ. This section is informative in nature.
3.1. Scope is Limited to the Stub to Resolver Scenario
Usage scenarios for the DNS protocol can be broadly classified in
three groups: stub to recursive resolver, recursive resolver to
authoritative server, and server to server. This design focuses only
on the "stub to recursive resolver" scenario following the approach
taken in [RFC7858] and [RFC8310].
QUESTION: Should this document specify any aspects of configuration
of discoverability differently to DoT?
No attempt is made to address the recursive to authoritative
scenarios. Authoritative resolvers are discovered dynamically
through NS records. It is noted that at the time of writing work is
ongoing in the DPRIVE working group to attempt to address the
analogous problem for DoT [I-D.ietf-dprive-phase2-requirements]. In
the absence of an agreed way for authoritative to signal support for
QUIC transport, recursive resolvers would have to resort to some
trial and error process. At this stage of QUIC deployment, this
would be mostly errors, and does not seem attractive. This could
change in the future.
The DNS protocol is also used for zone transfers. In the zone
transfer scenario [RFC5936], the client emits a single AXFR query,
and the server responds with a series of AXFR responses. This
creates a unique profile, in which a query results in several
responses. Supporting that profile would complicate the mapping of
DNS queries over QUIC streams. Zone transfers are not used in the
stub to recursive scenario that is the focus here, and seem to be
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currently well served by using DNS over TCP. There is no attempt to
support them in this proposed mapping of DNS to QUIC.
3.2. Provide DNS Privacy
DNS privacy considerations are described in [RFC7626]. [RFC7858]
defines how to mitigate some of these issues by transmitting DNS
messages over TLS and TCP and [RFC8310] specifies Strict and
Opportunistic Usage Profiles for DoT including how stub resolvers can
authenticate recursive resolvers.
QUIC connection setup includes the negotiation of security parameters
using TLS, as specified in [I-D.ietf-quic-tls], enabling encryption
of the QUIC transport. Transmitting DNS messages over QUIC will
provide essentially the same privacy protections as [RFC7858] and
[RFC8310]. Further discussion on this is provided in Section 7.
3.3. Design for Minimum Latency
QUIC is specifically designed to reduce the delay between HTTP
queries and HTTP responses. This is achieved through three main
components:
1. Support for 0-RTT data during session resumption.
2. Support for advanced error recovery procedures as specified in
[I-D.ietf-quic-recovery].
3. Mitigation of head-of-line blocking by allowing parallel delivery
of data on multiple streams.
This mapping of DNS to QUIC will take advantage of these features in
three ways:
1. Optional support for sending 0-RTT data during session resumption
(the security and privacy implications of this are discussed in
later sections).
2. Long-lived QUIC connections over which multiple DNS transactions
are performed, generating the sustained traffic required to
benefit from advanced recovery features.
3. Fast resumption of QUIC connections to manage the disconnect-on-
idle feature of QUIC without incurring retransmission time-outs.
4. Mapping of each DNS Query/Response transaction to a separate
stream, to mitigate head-of-line blocking.
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These considerations will be reflected in the mapping of DNS traffic
to QUIC streams in Section 4.2.
3.4. No Specific Middlebox Bypass Mechanism
The mapping of DNS over QUIC is defined for minimal overhead and
maximum performance. This means a different traffic profile than
HTTP over QUIC. This difference can be noted by firewalls and
middleboxes. There may be environments in which HTTP/QUIC will be
allowed, but DoQ will be disallowed and blocked by these middle
boxes.
It is recognized that this might be a problem, but there is currently
no indication on how widespread that problem might be. The problem
might be acute enough that the only realistic solution would be to
communicate with independent recursive resolvers using DNS/HTTPS, or
maybe DNS/HTTP/QUIC. Or the problem might be rare enough and the
performance gains significant enough that the appropriate solution
would be to use DoQ most of the time, and fall back to DNS/HTTPS some
of the time. Measurements and experimentation will inform that
decision.
It may indeed turn out that the complexity and overhead concerns are
negligible compared to the potential advantages of DNS/HTTPS, such as
integration with web services or firewall traversal, and that DoQ
does not provide sufficient performance gains to justify a new
protocol. We will evaluate that once implementations are available
and can be compared.
4. Specifications
4.1. Connection Establishment
DoQ connections are established as described in
[I-D.ietf-quic-transport]. During connection establishment, DoQ
support is indicated by selecting the ALPN token "dq" in the crypto
handshake.
4.1.1. Draft Version Identification
*RFC Editor's Note:* Please remove this section prior to publication
of a final version of this document.
Only implementations of the final, published RFC can identify
themselves as "doq". Until such an RFC exists, implementations MUST
NOT identify themselves using this string.
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Implementations of draft versions of the protocol MUST add the string
"-" and the corresponding draft number to the identifier. For
example, draft-huitema-dprive-dnsoquic-00 is identified using the
string "doq-h00".
4.1.2. Port Selection
By default, a DNS server that supports DoQ MUST listen for and accept
QUIC connections on the dedicated UDP port TBD (number to be defined
in Section 8, unless it has mutual agreement with its clients to use
a port other than TBD for DoQ. In order to use a port other than
TBD, both clients and servers would need a configuration option in
their software.
By default, a DNS client desiring to use DoQ with a particular server
MUST establish a QUIC connection to UDP port TBD on the server,
unless it has mutual agreement with its server to use a port other
than port TBD for DoQ. Such another port MUST NOT be port 53 or port
853. This recommendation against use of port 53 for DoQ is to avoid
confusion between DoQ and DNS/UDP as specified in [RFC1035].
Similarly, using port 853 would cause confusion between DoQ and DNS/
DTLS as specified in [RFC8094].
4.2. Stream Mapping and Usage
The mapping of DNS traffic over QUIC streams takes advantage of the
QUIC stream features detailed in Section 2 of
[I-D.ietf-quic-transport].
The stub to resolver DNS traffic follows a simple pattern in which
the client sends a query, and the server provides a response. This
design specifies that for each subsequent query on a QUIC connection
the client MUST select the next available client-initiated
bidirectional stream, in conformance with [I-D.ietf-quic-transport].
The client MUST send the DNS query over the selected stream, and MUST
indicate through the STREAM FIN mechanism that no further data will
be sent on that stream.
The server MUST send the response on the same stream, and MUST
indicate through the STREAM FIN mechanism that no further data will
be sent on that stream.
Therefore, a single client initiated DNS transaction consumes a
single stream. This means that the client's first query occurs on
QUIC stream 0, the second on 4, and so on.
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4.2.1. Server Initiated Transactions
There are planned traffic patterns in which a server sends
unsolicited queries to a client, such as for example PUSH messages
defined in [I-D.ietf-dnssd-push]. These occur when a client
subscribes to changes for a particular DNS RRset or resource record
type. When a PUSH server wishes to send such updates it MUST select
the next available server initiated bidirectional stream, in
conformance with [I-D.ietf-quic-transport].
The server MUST send the DNS query over the selected stream, and MUST
indicate through the STREAM FIN mechanism that no further data will
be sent on that stream.
The client MUST send the response on the same stream, and MUST
indicate through the STREAM FIN mechanism that no further data will
be sent on that stream.
Therefore a single server initiated DNS transaction consumes a single
stream. This means that the servers's first query occurs on QUIC
stream 1, the second on 5, and so on.
4.2.2. Stream Reset
Stream transmission may be abandoned by either party, using the
stream "reset" facility. A stream reset indicates that one party is
unwilling to continue processing the transaction associated with the
stream. The corresponding transaction MUST be abandoned. A Server
Failure (SERVFAIL, [RFC1035]) SHOULD be notified to the initiator of
the transaction.
4.3. Connection Management
Section 10 of the QUIC transport specifications
[I-D.ietf-quic-transport] specifies that connections can be closed in
three ways:
o idle timeout
o immediate close
o stateless reset
Clients and servers implementing DNS over QUIC SHOULD negotiate use
of the idle timeout. Closing on idle-timeout is done without any
packet exchange, which minimizes protocol overhead. This document
does not recommend a specific value of the idle timer.
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Clients SHOULD monitor the idle time incurred on their connection to
the server, defined by the time spend since the last packet from the
server has been received. When a client prepares to send a new DNS
query to the server, it will check whether the idle time is
sufficient lower than the idle timer. If it is, the client will send
the DNS query over the existing connection. If not, the client will
establish a new connection and send the query over that connection.
Clients MAY discard their connection to the server before the idle
timeout expires. If they do that, they SHOULD close the connection
explicitly, using QUIC's CONNECTION_CLOSE mechanisms, and indicating
the Application reason "No Error".
Clients and servers may close the connection for a variety of other
reasons, indicated using QUIC's CONNECTION_CLOSE. Client and servers
that send packets over a connection discarded by their peer MAY
receive a stateless reset indication. If a connection fails, all
queries in progress over the connection MUST be considered failed,
and aServer Failure (SERVFAIL, [RFC1035]) SHOULD be notified to the
initiator of the transaction.
4.4. Connection Resume and 0-RTT
A stub resolver MAY take advantage of the connection resume
mechanisms supported by QUIC transport [I-D.ietf-quic-transport] and
QUIC TLS [I-D.ietf-quic-tls]. Stub resolvers SHOULD consider
potential privacy issues associated with session resume before
deciding to use this mechanism. These privacy issues are detailed in
Section 7.2.
When resuming a session, a stub resolver MAY take advantage of the
0-RTT mechanism supported by QUIC. The 0-RTT mechanism MUST NOT be
used to send data that is not "replayable" transactions. For
example, a stub resolver MAY transmit a Query as 0-RTT, but MUST NOT
transmit an Update.
5. Implementation Requirements
5.1. Authentication
For the stub to recursive resolver scenario, the authentication
requirements are the same as described in [RFC7858] and [RFC8310].
There is no need to authenticate the client's identity in either
scenario.
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5.2. Fall Back to Other Protocols on Connection Failure
If the establishment of the DoQ connection fails, clients SHOULD
attempt to fall back to DoT and then potentially clear text, as
specified in [RFC7858] and [RFC8310], depending on their privacy
profile.
DNS clients SHOULD remember server IP addresses that don't support
DoQ, including timeouts, connection refusals, and QUIC handshake
failures, and not request DoQ from them for a reasonable period (such
as one hour per server). DNS clients following an out-of-band key-
pinned privacy profile ([RFC7858]) MAY be more aggressive about
retrying DoQ connection failures.
5.3. Address Validation
The QUIC transport specification defines Address Validation
procedures to avoid servers being used in address amplification
attacks (see section 8 of [I-D.ietf-quic-transport]). DoQ
implementations MUST conform to this specification, which limits the
worst case amplification to a factor 3.
DoQ implementations SHOULD consider configuring servers to use the
Address Validation using Retry Packets procedure defined in section
8.1.2 of [I-D.ietf-quic-transport]). This procedure imposes a 1-RTT
delay for verifying the return routability of the source address of a
client, similar to the DNS Cookies mechanism defined in [RFC7873].
DoQ implementations that configure Address Validation using Retry
Packets SHOULD implement the Address Validation for Future
Connections procedure defined in section 8.1.3 of
[I-D.ietf-quic-transport]). This define how servers can send NEW
TOKEN frames to clients after the client address is validated, in
order to avoid the 1-RTT penalty during subsequent connections by the
client from the same address.
5.4. Response Sizes
DoQ does not suffer from the same limitations on the size of queries
and responses that as DNS/UDP [RFC1035] does. Queries and Responses
are sent on QUIC streams, which in theory can carry up to 2^62 bytes.
However, clients or servers MAY impose a limit on the maximum size of
data that they can accept over a given stream. This is controlled in
QUIC by the transport parameters:
o initial_max_stream_data_bidi_local: when set by the client,
specifies the amount of data that servers can send on a "response"
stream without waiting for a MAX_STREAM_DATA frame.
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o initial_max_stream_data_bidi_remote: when set by the server,
specifies the amount of data that clients can send on a "query"
stream without waiting for a MAX_STREAM_DATA frame.
Clients and servers SHOULD treat these parameters as the practical
maximum of queries and responses. If the EDNS parameters of a Query
indicate a lower message size, servers MUST comply with that
indication.
5.5. DNS Message IDs
When sending queries over a QUIC connection, the DNS Message ID MUST
be set to zero.
5.6. Padding
There are mechanisms specified for both padding individual DNS
messages [RFC7830], [RFC8467] and padding within QUIC packets (see
Section 8.6 of [I-D.ietf-quic-transport]), which may contain multiple
frames.
Implementations SHOULD NOT use DNS options for padding individual DNS
messages, because QUIC transport MAY transmit multiple STREAM frames
containing separate DNS messages in a single QUIC packet. Instead,
implementations SHOULD use QUIC PADDING frames to align the packet
length to a small set of fixed sizes, aligned with the
recommendations of [RFC8467].
5.7. Connection Handling
[RFC7766] provides updated guidance on DNS/TCP much of which is
applicable to DoQ. This section attempts to specify how those
considerations apply to DoQ.
5.7.1. Connection Reuse
Historic implementations of DNS stub resolvers are known to open and
close TCP connections for each DNS query. To avoid excess QUIC
connections, each with a single query, clients SHOULD reuse a single
QUIC connection to the recursive resolver.
In order to achieve performance on par with UDP, DNS clients SHOULD
send their queries concurrently over the QUIC streams on a QUIC
connection. That is, when a DNS client sends multiple queries to a
server over a QUIC connection, it SHOULD NOT wait for an outstanding
reply before sending the next query.
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5.7.2. Connection Close
In order to amortize QUIC and TLS connection setup costs, clients and
servers SHOULD NOT immediately close a QUIC connection after each
response. Instead, clients and servers SHOULD reuse existing QUIC
connections for subsequent queries as long as they have sufficient
resources. In some cases, this means that clients and servers may
need to keep idle connections open for some amount of time.
Under normal operation DNS clients typically initiate connection
closing on idle connections; however, DNS servers can close the
connection if the idle timeout set by local policy is exceeded.
Also, connections can be closed by either end under unusual
conditions such as defending against an attack or system failure/
reboot.
Clients and servers that keep idle connections open MUST be robust to
termination of idle connection by either party. As with current DNS
over TCP, DNS servers MAY close the connection at any time (perhaps
due to resource constraints). As with current DNS/TCP, clients MUST
handle abrupt closes and be prepared to reestablish connections and/
or retry queries.
5.7.3. Idle Timeouts
Proper management of established and idle connections is important to
the healthy operation of a DNS server. An implementation of DoQ
SHOULD follow best practices for DNS/TCP, as described in [RFC7766].
Failure to do so may lead to resource exhaustion and denial of
service.
This document does not make specific recommendations for timeout
values on idle connections. Clients and servers should reuse and/or
close connections depending on the level of available resources.
Timeouts may be longer during periods of low activity and shorter
during periods of high activity. Current work in this area may also
assist DoT clients and servers in selecting useful timeout values
[RFC7828] [RFC8490] [TDNS].
Clients that are willing to use QUIC's 0-RTT mechanism can
reestablish connections and send transactions on the new connection
with minimal delay overhead. These clients MAY chose low values of
the idle timer, but SHOULD NOT pick value lower than 20 seconds.
Per section 10.2 of QUIC transport specification, the effective value
of the idle timeout is computed as the minimum of the values
advertised by the two endpoints.
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5.8. Flow Control Mechanisms
Servers and Clients manage flow control as specified in QUIC.
Servers MAY use the "maximum stream ID" option of the QUIC transport
to limit the number of streams opened by the client. This mechanism
will effectively limit the number of DNS queries that a client can
send.
6. Security Considerations
The security considerations of DoQ should be comparable to those of
DoT [RFC7858].
7. Privacy Considerations
DoQ is specifically designed to protect the DNS traffic between stub
and resolver from observations by third parties, and thus protect the
privacy of queries from the stub. However, the recursive resolver
has full visibility of the stub's traffic, and could be used as an
observation point, as discussed in [I-D.ietf-dprive-rfc7626-bis].
These considerations do not differ between DoT and DoQ and are not
discussed further here.
QUIC incorporates the mechanisms of TLS 1.3 [RFC8446] and this
enables QUIC transmission of "Zero-RTT" data. This can provide
interesting latency gains, but it raises two concerns:
1. Adversaries could replay the zero-RTT data and infer its content
from the behavior of the receiving server.
2. The zero-RTT mechanism relies on TLS resume, which can provide
linkability between successive client sessions.
These issues are developed in Section 7.1 and Section 7.2.
7.1. Privacy Issues With Zero RTT data
The zero-RTT data can be replayed by adversaries. That data may
triggers a query by a recursive resolver to an authoritative
resolvers. Adversaries may be able to pick a time at which the
recursive resolver outgoing traffic is observable, and thus find out
what name was queried for in the 0-RTT data.
This risk is in fact a subset of the general problem of observing the
behavior of the recursive resolver discussed in [RFC7626]. The
attack is partially mitigated by reducing the observability of this
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traffic. However, the risk is amplified for 0-RTT data, because the
attacker might replay it at chosen times, several times.
The recommendation in [RFC8446] is that the capability to use 0-RTT
data should be turned off by default, on only enabled if the user
clearly understands the associated risks.
QUESTION: Should 0-RTT only be used with Opportunistic profiles (i.e.
disabled by default for Strict only)?
7.2. Privacy Issues With Session Resume
The QUIC session resume mechanism reduces the cost of reestablishing
sessions and enables zero-RTT data. There is a linkability issue
associated with session resume, if the same resume token is used
several times, but this risk is mitigated by the mechanisms
incorporated in QUIC and in TLS 1.3. With these mechanisms, clients
and servers can cooperate to avoid linkability by third parties.
However, the server will always be able to link the resumed session
to the initial session. This creates a virtual long duration
session. The series of queries in that session can be used by the
server to identify the client.
Enabling the server to link client sessions through session resume is
probably not a large additional risk if the client's connectivity did
not change between the sessions, since the two sessions can probably
be correlated by comparing the IP addresses. On the other hand, if
the addresses did change, the client SHOULD consider whether the
linkability risk exceeds the privacy benefits. This evaluation will
obviously depend on the level of trust between stub and recursive.
7.3. Traffic Analysis
Even though QUIC packets are encrypted, adversaries can gain
information from observing packet lengths, in both queries and
responses, as well as packet timing. Many DNS requests are emitted
by web browsers. Loading a specific web page may require resolving
dozen of DNS names. If an application adopts a simple mapping of one
query or response per packet, or "one QUIC STREAM frame per packet",
then the succession of packet lengths may provide enough information
to identify the requested site.
Implementations SHOULD use the mechanisms defined in Section 5.6 to
mitigate this attack.
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8. IANA Considerations
8.1. Registration of DoQ Identification String
This document creates a new registration for the identification of
DoQ in the "Application Layer Protocol Negotiation (ALPN) Protocol
IDs" registry established in [RFC7301].
The "doq" string identifies DoQ:
Protocol: DoQ
Identification Sequence: 0x64 0x71 ("dq")
Specification: This document
8.2. Reservation of Dedicated Port
IANA is required to add the following value to the "Service Name and
Transport Protocol Port Number Registry" in the System Range. The
registry for that range requires IETF Review or IESG Approval
{{?RFC6335], and such a review was requested using the early
allocation process {{?RFC7120] for the well-known UDP port in this
document. Since port 853 is reserved for 'DNS query-response
protocol run over TLS' consideration is requested for reserving port
TBD for 'DNS query-response
protocol run over QUIC'.
Service Name domain-s
Transport Protocol(s) TCP/UDP
Assignee IESG
Contact IETF Chair
Description DNS query-response protocol run over QUIC
Reference This document
8.2.1. Port number 784 for experimentations
*RFC Editor's Note:* Please remove this section prior to publication
of a final version of this document.
Early experiments MAY use port 784. This port is marked in the IANA
registry as unassigned.
9. Acknowledgements
This document liberally borrows text from [I-D.ietf-quic-http] edited
by Mike Bishop, and from [RFC7858] authored by Zi Hu, Liang Zhu, John
Heidemann, Allison Mankin, Duane Wessels, and Paul Hoffman.
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The privacy issue with 0-RTT data and session resume were analyzed by
Daniel Kahn Gillmor (DKG) in a message to the IETF "DPRIV" working
group [DNS0RTT].
Thanks to our wide cast of supporters.
10. References
10.1. Normative References
[I-D.ietf-dnsop-terminology-ter]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-ietf-dnsop-terminology-ter-01 (work in
progress), February 2020.
[I-D.ietf-quic-tls]
Thomson, M. and S. Turner, "Using TLS to Secure QUIC",
draft-ietf-quic-tls-27 (work in progress), February 2020.
[I-D.ietf-quic-transport]
Iyengar, J. and M. Thomson, "QUIC: A UDP-Based Multiplexed
and Secure Transport", draft-ietf-quic-transport-27 (work
in progress), February 2020.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<https://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <https://www.rfc-editor.org/info/rfc1035>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC7873] Eastlake 3rd, D. and M. Andrews, "Domain Name System (DNS)
Cookies", RFC 7873, DOI 10.17487/RFC7873, May 2016,
<https://www.rfc-editor.org/info/rfc7873>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
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[RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
for DNS over TLS and DNS over DTLS", RFC 8310,
DOI 10.17487/RFC8310, March 2018,
<https://www.rfc-editor.org/info/rfc8310>.
10.2. Informative References
[DNS0RTT] Kahn Gillmor, D., "DNS + 0-RTT", Message to DNS-Privacy WG
mailing list, April 2016, <https://www.ietf.org/mail-
archive/web/dns-privacy/current/msg01276.html>.
[I-D.ietf-dnssd-push]
Pusateri, T. and S. Cheshire, "DNS Push Notifications",
draft-ietf-dnssd-push-25 (work in progress), October 2019.
[I-D.ietf-dprive-phase2-requirements]
Livingood, J., Mayrhofer, A., and B. Overeinder, "DNS
Privacy Requirements for Exchanges between Recursive
Resolvers and Authoritative Servers", draft-ietf-dprive-
phase2-requirements-00 (work in progress), December 2019.
[I-D.ietf-dprive-rfc7626-bis]
Bortzmeyer, S. and S. Dickinson, "DNS Privacy
Considerations", draft-ietf-dprive-rfc7626-bis-04 (work in
progress), January 2020.
[I-D.ietf-dprive-xfr-over-tls]
Zhang, H., Aras, P., Toorop, W., Dickinson, S., and A.
Mankin, "DNS Zone Transfer-over-TLS", draft-ietf-dprive-
xfr-over-tls-00 (work in progress), November 2019.
[I-D.ietf-quic-http]
Bishop, M., "Hypertext Transfer Protocol Version 3
(HTTP/3)", draft-ietf-quic-http-27 (work in progress),
February 2020.
[I-D.ietf-quic-recovery]
Iyengar, J. and I. Swett, "QUIC Loss Detection and
Congestion Control", draft-ietf-quic-recovery-26 (work in
progress), February 2020.
[RFC5936] Lewis, E. and A. Hoenes, Ed., "DNS Zone Transfer Protocol
(AXFR)", RFC 5936, DOI 10.17487/RFC5936, June 2010,
<https://www.rfc-editor.org/info/rfc5936>.
[RFC7626] Bortzmeyer, S., "DNS Privacy Considerations", RFC 7626,
DOI 10.17487/RFC7626, August 2015,
<https://www.rfc-editor.org/info/rfc7626>.
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[RFC7766] Dickinson, J., Dickinson, S., Bellis, R., Mankin, A., and
D. Wessels, "DNS Transport over TCP - Implementation
Requirements", RFC 7766, DOI 10.17487/RFC7766, March 2016,
<https://www.rfc-editor.org/info/rfc7766>.
[RFC7828] Wouters, P., Abley, J., Dickinson, S., and R. Bellis, "The
edns-tcp-keepalive EDNS0 Option", RFC 7828,
DOI 10.17487/RFC7828, April 2016,
<https://www.rfc-editor.org/info/rfc7828>.
[RFC7830] Mayrhofer, A., "The EDNS(0) Padding Option", RFC 7830,
DOI 10.17487/RFC7830, May 2016,
<https://www.rfc-editor.org/info/rfc7830>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/info/rfc7858>.
[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017,
<https://www.rfc-editor.org/info/rfc8094>.
[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
for DNS (EDNS(0))", RFC 8467, DOI 10.17487/RFC8467,
October 2018, <https://www.rfc-editor.org/info/rfc8467>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>.
[RFC8490] Bellis, R., Cheshire, S., Dickinson, J., Dickinson, S.,
Lemon, T., and T. Pusateri, "DNS Stateful Operations",
RFC 8490, DOI 10.17487/RFC8490, March 2019,
<https://www.rfc-editor.org/info/rfc8490>.
[TDNS] Zhu, L., Hu, Z., Heidemann, J., Wessels, D., Mankin, A.,
and N. Somaiya, "Connection-Oriented DNS to Improve
Privacy and Security", 2015 IEEE Symposium on Security and