Network Working Group C. HuitemaInternet-Draft Private Octopus Inc.Intended status: Standards Track S. DickinsonExpires: January 13, 2022 Sinodun IT A. Mankin Salesforce July 12, 2021Specification of DNS over Dedicated QUIC Connectionsdraft-ietf-dprive-dnsoquic-03Abstract 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 inRFC7858, and latency characteristics similar to classic DNS over UDP.Status of This Memo This Internet-Draft is submitted in full conformance with the provisions ofBCP 78 andBCP 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 athttps://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 January 13, 2022.Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject toBCP 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 documentsHuitema, et al. Expires January 13, 2022 [Page 1]
Internet-Draft DNS over Dedicated QUIC July 2021 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 Contents1. Introduction . . . . . . . . . . . . . . . . . . . . . . . .32. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . .43. Document work via GitHub . . . . . . . . . . . . . . . . . .44. Design Considerations . . . . . . . . . . . . . . . . . . . .44.1. Provide DNS Privacy . . . . . . . . . . . . . . . . . . .44.2. Design for Minimum Latency . . . . . . . . . . . . . . .54.3. No Specific Middlebox Bypass Mechanism . . . . . . . . .64.4. No Server Initiated Transactions . . . . . . . . . . . .65. Specifications . . . . . . . . . . . . . . . . . . . . . . .65.1. Connection Establishment . . . . . . . . . . . . . . . .65.1.1. Draft Version Identification . . . . . . . . . . . .65.1.2. Port Selection . . . . . . . . . . . . . . . . . . .65.2. Stream Mapping and Usage . . . . . . . . . . . . . . . .75.2.1. DNS Message IDs . . . . . . . . . . . . . . . . . . .85.3. DoQ Error Codes . . . . . . . . . . . . . . . . . . . . .85.3.1. Transaction Errors . . . . . . . . . . . . . . . . .85.3.2. Protocol Errors . . . . . . . . . . . . . . . . . . .85.4. Connection Management . . . . . . . . . . . . . . . . . .95.5. Connection Resume and 0-RTT . . . . . . . . . . . . . . .105.6. Message Sizes . . . . . . . . . . . . . . . . . . . . . .106. Implementation Requirements . . . . . . . . . . . . . . . . .116.1. Authentication . . . . . . . . . . . . . . . . . . . . .116.2. Fall Back to Other Protocols on Connection Failure . . .116.3. Address Validation . . . . . . . . . . . . . . . . . . .116.4. Padding . . . . . . . . . . . . . . . . . . . . . . . . .126.5. Connection Handling . . . . . . . . . . . . . . . . . . .126.5.1. Connection Reuse . . . . . . . . . . . . . . . . . .126.5.2. Resource Management and Idle Timeout Values . . . . .136.6. Processing Queries in Parallel . . . . . . . . . . . . .136.7. Zone transfer . . . . . . . . . . . . . . . . . . . . . .146.8. Flow Control Mechanisms . . . . . . . . . . . . . . . . .147. Implementation Status . . . . . . . . . . . . . . . . . . . .147.1. Performance Measurements . . . . . . . . . . . . . . . .158. Security Considerations . . . . . . . . . . . . . . . . . . .159. Privacy Considerations . . . . . . . . . . . . . . . . . . .169.1. Privacy Issues With 0-RTT data . . . . . . . . . . . . .169.2. Privacy Issues With Session Resume . . . . . . . . . . .169.3. Traffic Analysis . . . . . . . . . . . . . . . . . . . .1710. IANA Considerations . . . . . . . . . . . . . . . . . . . . .1710.1. Registration of DoQ Identification String . . . . . . .17Huitema, et al. Expires January 13, 2022 [Page 2]
Internet-Draft DNS over Dedicated QUIC July 202110.2. Reservation of Dedicated Port . . . . . . . . . . . . .1710.2.1. Port number 784 for experimentations . . . . . . . .1811. Acknowledgements . . . . . . . . . . . . . . . . . . . . . .1812. References . . . . . . . . . . . . . . . . . . . . . . . . .1912.1. Normative References . . . . . . . . . . . . . . . . . .1912.2. Informative References . . . . . . . . . . . . . . . . .2012.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . .21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .221. Introduction Domain Name System (DNS) concepts are specified in "Domain names - concepts and facilities" [RFC1034]. The transmission of DNS queries and responses over UDP and TCP is specified in "Domain names - implementation and specification" [RFC1035]. This document presents a mapping of the DNS protocol over the QUIC transport [RFC9000] [RFC9001]. DNS over QUIC is referred here as DoQ, in line with "DNS Terminology" [I-D.ietf-dnsop-rfc8499bis]. 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 as specified in "Usage Profiles for DNS over TLS and DNS over DTLS" [RFC8310]. 2. Provide an improved level of source address validation for DNS servers compared to classic DNS over UDP. 3. Provide a transport that is not constrained by path MTU limitations on the size of DNS responses it can send. 4. Explore the characteristics of using QUIC as a DNS transport, versus other solutions like DNS over UDP [RFC1035], DNS over TLS (DoT) [RFC7858], or DNS over HTTPS (DoH) [RFC8484]. In order to achieve these goals, and to support ongoing work on encryption of DNS, the scope of this document includes o the "stub to recursive resolver" scenario o the "recursive resolver to authoritative nameserver" scenario and o the "nameserver to nameserver" scenario (mainly used for zone transfers (XFR) [RFC1995], [RFC5936]). In other words, this document is intended to specify QUIC as a general purpose transport for DNS.Huitema, et al. Expires January 13, 2022 [Page 3]
Internet-Draft DNS over Dedicated QUIC July 2021 The specific non-goals of this document are: 1. No attempt is made to evade potential blocking of DNS over QUIC traffic by middleboxes. 2. No attempt to support server initiated transactions, which are used only in DNS Stateful Operations (DSO) [RFC8490]. 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 HTTP in "Hypertext Transfer Protocol Version 3 (HTTP/3)"[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 4 presents the reasoning that guided the proposed design.Section 5 specifies the actual mapping of DoQ.Section 6 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 inBCP 14 [RFC8174].3. Document work via GitHub (RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION)The Github repository for this document is athttps://github.com/huitema/dnsoquic. Proposed text and editorial changes are very much welcomed there, but any functional changes should always first be discussed on the IETF DPRIVE WG (dns-privacy) mailing list.4. Design Considerations This section and its subsections present the design guidelines that were used for DoQ. This section is informative in nature.4.1. Provide DNS Privacy DoT [RFC7858] defines how to mitigate some of the issues described in "DNS Privacy Considerations" [RFC7626] by specifying how to transmit DNS messages over TLS. The "Usage Profiles for DNS over TLS and DNS over DTLS" [RFC8310] specify Strict and Opportunistic Usage Profiles for DoT including how stub resolvers can authenticate recursive resolvers.Huitema, et al. Expires January 13, 2022 [Page 4]
Internet-Draft DNS over Dedicated QUIC July 2021 QUIC connection setup includes the negotiation of security parameters using TLS, as specified in "Using TLS to Secure QUIC" [RFC9001], enabling encryption of the QUIC transport. Transmitting DNS messages over QUIC will provide essentially the same privacy protections as DoT [RFC7858] including Strict and Opportunistic Usage Profiles [RFC8310]. Further discussion on this is provided inSection 9.4.2. 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 "QUIC Loss Detection and Congestion Control" [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. This enables servers to respond to queries "out of order". It also enables clients to process responses as soon as they arrive, without having to wait for in order delivery of responses previously posted by the server. These considerations will be reflected in the mapping of DNS traffic to QUIC streams inSection 5.2.Huitema, et al. Expires January 13, 2022 [Page 5]
Internet-Draft DNS over Dedicated QUIC July 20214.3. No Specific Middlebox Bypass Mechanism The mapping of DoQ is defined for minimal overhead and maximum performance. This means a different traffic profile than HTTP3 over QUIC. This difference can be noted by firewalls and middleboxes. There may be environments in which HTTP3 over QUIC will be able to pass through, but DoQ will be blocked by these middle boxes.4.4. No Server Initiated Transactions As stated inSection 1, this document does not specify support for server initiated transactions. DSO is only applicable for DNS over TCP and DNS over TLS. DSO is not applicable to DNS over HTTP since HTTP has its own mechanism for managing sessions, and this is incompatible with the DSO; the same is true for DoQ.5. Specifications5.1. Connection Establishment DoQ connections are established as described in the QUIC transport specification [RFC9000]. During connection establishment, DoQ support is indicated by selecting the ALPN token "doq" in the crypto handshake.5.1.1. Draft Version Identification (RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION) 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. Implementations of draft versions of the protocol MUST add the string "-" and the corresponding draft number to the identifier. For example,draft-ietf-dprive-dnsoquic-00 is identified using the string "doq-i00".5.1.2. 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 inSection 10), 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,Huitema, et al. Expires January 13, 2022 [Page 6]
Internet-Draft DNS over Dedicated QUIC July 2021 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. This recommendation against use of port 53 for DoQ is to avoid confusion between DoQ and the use of DNS over UDP [RFC1035].5.2. Stream Mapping and Usage The mapping of DNS traffic over QUIC streams takes advantage of the QUIC stream features detailed inSection 2 of the QUIC transport specification [RFC9000]. DNS traffic follows a simple pattern in which the client sends a query, and the server provides one or more responses (multiple can responses occur in zone transfers). The mapping specified here requires that the client selects a separate QUIC stream for each query. The server then uses the same stream to provide all the response messages for that query. In order that multiple responses can be parsed, a 2-octet length field is used in exactly the same way as the 2-octet length field defined for DNS over TCP [RFC1035]. The practical result of this is that the content of each QUIC stream is exactly the same as the content of a TCP connection that would manage exactly one query. All DNS messages (queries and responses) sent over DoQ connections MUST be encoded as a 2-octet length field followed by the message content as specified in [RFC1035]. The client MUST select the next available client-initiated bidirectional stream for each subsequent query on a QUIC connection, in conformance with the QUIC transport specification [RFC9000]. 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(s) on the same stream and MUST indicate, after the last response, 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. For completeness it is noted that versions prior to -02 of this specification proposed a simpler mapping scheme which omitted the 2 byte length field and supported only a single response on a given stream. The more complex mapping above was adopted to specificallyHuitema, et al. Expires January 13, 2022 [Page 7]
Internet-Draft DNS over Dedicated QUIC July 2021 cater for XFR support, however it breaks compatibility with earlier versions.5.2.1. DNS Message IDs When sending queries over a QUIC connection, the DNS Message ID MUST be set to zero. It is noted that this has implications for proxying DoQ message to other transports in that a mapping of some form must be performed (e.g., from DoQ connection/stream to unique Message ID).5.3. DoQ Error Codes The following error codes are defined for use when abruptly terminating streams, aborting reading of streams, or immediately closing connections: DOQ_NO_ERROR (0x00): No error. This is used when the connection or stream needs to be closed, but there is no error to signal. DOQ_INTERNAL_ERROR (0x01): The DoQ implementation encountered an internal error and is incapable of pursuing the transaction or the connection. DOQ_PROTOCOL_ERROR (0x01): The DoQ implementation encountered an protocol error and is forcibly aborting the connection.5.3.1. Transaction Errors Servers normally complete transactions by sending a DNS response (or responses) on the transaction's stream, including cases where the DNS response indicates a DNS error. For example, a Server Failure (SERVFAIL, [RFC1035]) SHOULD be notified to the client by sending back a response with the Response Code set to SERVFAIL. If a server is incapable of sending a DNS response due to an internal error, it may issue a QUIC Stream Reset with error code DOQ_INTERNAL_ERROR. The corresponding transaction MUST be abandoned.5.3.2. Protocol Errors Other error scenarios can occur due to malformed, incomplete or unexpected messages during a transaction. These include (but are not limited to) o a client or server receives a message with a non-zero Message IDHuitema, et al. Expires January 13, 2022 [Page 8]
Internet-Draft DNS over Dedicated QUIC July 2021 o a client or server receives a STREAM FIN before receiving all the bytes for a message indicated in the 2-octet length field o a client receives a STREAM FIN before receiving all the expected responses o a server receives more than one query on a stream o a client receives a different number of responses on a stream than expected (e.g. multiple responses to a query for an A record) o an implementation receives a message containing the edns-tcp- keepalive EDNS(0) Option [RFC7828] (seeSection 6.5.2) o an implementation receives a message containing the EDNS(0) Padding Option [RFC7830] (seeSection 6.4) If a peer encounters such an error condition it is considered a fatal error. It SHOULD forcibly abort the connection using QUIC's CONNECTION_CLOSE mechanism, and use the DoQ error code DOQ_PROTCOL_ERROR. It is noted that the restrictions on use of the above EDNS(0) options has implications for proxying message from TCP/DoT/DoH over DoQ.5.4. Connection ManagementSection 10 of the QUIC transport specification [RFC9000] specifies that connections can be closed in three ways: o idle timeout o immediate close o stateless reset Clients and servers implementing DoQ SHOULD negotiate use of the idle timeout. Closing on idle timeout is done without any packet exchange, which minimizes protocol overhead. Persection 10.1 of the QUIC transport specification, the effective value of the idle timeout is computed as the minimum of the values advertised by the two endpoints. Practical considerations on setting the idle timeout are discussed inSection 6.5.2. Clients SHOULD monitor the idle time incurred on their connection to the server, defined by the time spent 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 isHuitema, et al. Expires January 13, 2022 [Page 9]
Internet-Draft DNS over Dedicated QUIC July 2021 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 mechanism, and use the DoQ error code DOQ_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 a Server Failure (SERVFAIL, [RFC1035]) SHOULD be notified to the initiator of the transaction.5.5. Connection Resume and 0-RTT A client MAY take advantage of the connection resume mechanisms supported by QUIC transport [RFC9000] and QUIC TLS [RFC9001]. Clients SHOULD consider potential privacy issues associated with session resume before deciding to use this mechanism. These privacy issues are detailed inSection 9.2. When resuming a session, a client 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 client MAY transmit a Query as 0-RTT, but MUST NOT transmit an Update.5.6. Message Sizes DoQ Queries and Responses are sent on QUIC streams, which in theory can carry up to 2^62 bytes. However, DNS messages are restricted in practice to a maximum size of 65535 bytes. This maximum size is enforced by the use of a two-octet message length field in DNS over TCP [RFC1035] and DNS over TLS [RFC7858], and by the definition of the "application/dns-message" for DNS over HTTP [RFC8484]. DoQ enforces the same restriction. The flow control mechanisms of QUIC control how much data can be sent by QUIC nodes at a given time. The initial values of per stream flow control parameters is defined by two 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.Huitema, et al. Expires January 13, 2022 [Page 10]
Internet-Draft DNS over Dedicated QUIC July 2021 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. For better performance, it is RECOMMENDED that clients and servers set each of these two parameters to a value of 65535 or greater. The Extension Mechanisms for DNS (EDNS) [RFC6891] allow peers to specify the UDP message size. This parameter is ignored by DoQ. DoQ implementations always assume that the maximum message size is 65535 bytes.6. Implementation Requirements6.1. Authentication For the stub to recursive resolver scenario, the authentication requirements are the same as described in DoT [RFC7858] and "Usage Profiles for DNS over TLS and DNS over DTLS" [RFC8310]. There is no need to authenticate the client's identity in either scenario. For zone transfer, the requirements are the same as described in [I-D.ietf-dprive-xfr-over-tls]. For the recursive resolver to authoritative nameserver scenario, authentication requirements are unspecified at the time of writing and are the subject on ongoing work in the DPRIVE WG.6.2. Fall Back to Other Protocols on Connection Failure If the establishment of the DoQ connection fails, clients MAY attempt to fall back to DoT and then potentially clear text, as specified in DoT [RFC7858] and "Usage Profiles for DNS over TLS and DNS over DTLS" [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.6.3. Address ValidationSection 8 of the QUIC transport specification [RFC9000] defines Address Validation procedures to avoid servers being used in address amplification attacks. DoQ implementations MUST conform to thisHuitema, et al. Expires January 13, 2022 [Page 11]
Internet-Draft DNS over Dedicated QUIC July 2021 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 insection8.1.2 of the QUIC transport specification [RFC9000]). 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 [RFC7873]. DoQ implementations that configure Address Validation using Retry Packets SHOULD implement the Address Validation for Future Connections procedure defined insection 8.1.3 of the QUIC transport specification [RFC9000]). This defines 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.6.4. Padding There are mechanisms specified for padding individual DNS messages in "The EDNS(0) Padding Option" [RFC7830] and for padding within QUIC packets (seeSection 8.6 of the QUIC transport specification [RFC9000]). Implementations MUST 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 the "Padding Policies for Extension Mechanisms for DNS (EDNS(0))" [RFC8467].6.5. Connection Handling "DNS Transport over TCP - Implementation Requirements" [RFC7766] provides updated guidance on DNS over TCP, some of which is applicable to DoQ. This section attempts to specify which and how those considerations apply to DoQ.6.5.1. Connection Reuse Historic implementations of DNS clients 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.Huitema, et al. Expires January 13, 2022 [Page 12]
Internet-Draft DNS over Dedicated QUIC July 2021 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.6.5.2. Resource Management and Idle Timeout Values 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 similar to those specified for DNS over TCP [RFC7766], in particular with regard to: o Concurrent Connections (Section 6.2.2) o Security Considerations (Section 10) Failure to do so may lead to resource exhaustion and denial of service. Clients that want to maintain long duration DoQ connections SHOULD use the idle timeout mechanisms defined inSection 10.1 of the QUIC transport specification [RFC9000]. Clients and servers MUST NOT send the edns-tcp-keepalive EDNS(0) Option [RFC7828] in any messages sent on a DoQ connection (because it is specific to the use of TCP/TLS as a transport). 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. 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.6.6. Processing Queries in Parallel As specified inSection 7 of "DNS Transport over TCP - Implementation Requirements" [RFC7766], resolvers are RECOMMENDED to support the preparing of responses in parallel and sending them out of order. In DoQ, they do that by sending responses on their specific stream as soon as possible, without waiting for availability of responses for previously opened streams.Huitema, et al. Expires January 13, 2022 [Page 13]
Internet-Draft DNS over Dedicated QUIC July 20216.7. Zone transfer [I-D.ietf-dprive-xfr-over-tls] specifies zone transfer over TLS (XoT) and includes updates to [RFC1995] (IXFR), [RFC5936] (AXFR) and [RFC7766]. Considerations relating to the re-use of XoT connections described there apply analogously to zone transfers performed using DoQ connections. For example: o DoQ servers MUST be able to handle multiple concurrent IXFR requests on a single QUIC connection o DoQ servers MUST be able to handle multiple concurrent AXFR requests on a single QUIC connection o DoQ implementations SHOULD * use the same QUIC connection for both AXFR and IXFR requests to the same primary * pipeline such requests (if they pipeline XFR requests in general) and MAY intermingle them * send the response(s) for each request as soon as they are available i.e. responses MAY be sent intermingled6.8. 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 on a single DoQ connection.7. Implementation Status (RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION) This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. 1. AdGuard launched a DoQ recursive resolver service in December 2020. They have released a suite of open source tools that support DoQ: 1. AdGuard C++ DNS libraries [1] A DNS proxy library that supports all existing DNS protocols including DNS-over-TLS, DNS-over-HTTPS, DNSCrypt and DNS-over-QUIC (experimental).Huitema, et al. Expires January 13, 2022 [Page 14]
Internet-Draft DNS over Dedicated QUIC July 2021 2. DNS Proxy [2] A simple DNS proxy server that supports all existing DNS protocols including DNS-over-TLS, DNS-over- HTTPS, DNSCrypt, and DNS-over-QUIC. Moreover, it can work as a DNS-over-HTTPS, DNS-over-TLS or DNS-over-QUIC server. 3. CoreDNS fork for AdGuard DNS [3] Includes DNS-over-QUIC server-side support. 4. dnslookup [4] Simple command line utility to make DNS lookups. Supports all known DNS protocols: plain DNS, DoH, DoT, DoQ, DNSCrypt. 2. Quicdoq [5] Quicdoq is a simple open source implementation of DoQ. It is written in C, based on Picoquic [6]. 3. Flamethrower [7] is an open source DNS performance and functional testing utility written in C++ that has an experimental implementation of DoQ. 4. aioquic [8] is an implementation of QUIC in Python. It includes example client and server for DoQ.7.1. Performance Measurements To our knowledge, no benchmarking studies comparing DoT, DoH and DoQ are published yet. However anecdotal evidence from the AdGuard DoQ recursive resolver deployment [9] indicates that it performs well compared to the other encrypted protocols, particularly in mobile environments. Reasons given for this include that DoQ o Uses less bandwidth due to a more efficient handshake (and due to less per message overhead when compared to DoH). o Performs better in mobile environments due to the increased resilience to packet loss o Can maintain connections as users move between mobile networks via its connection management8. Security Considerations The security considerations of DoQ should be comparable to those of DoT [RFC7858].Huitema, et al. Expires January 13, 2022 [Page 15]
Internet-Draft DNS over Dedicated QUIC July 20219. Privacy Considerations The general considerations of encrypted transports provided in "DNS Privacy Considerations" [I-D.ietf-dprive-rfc7626-bis] apply to DoQ. The specific considerations provided there 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 "0-RTT" data. This can provide interesting latency gains, but it raises two concerns: 1. Adversaries could replay the 0-RTT data and infer its content from the behavior of the receiving server. 2. The 0-RTT mechanism relies on TLS resume, which can provide linkability between successive client sessions. These issues are developed inSection 9.1 andSection 9.2.9.1. Privacy Issues With 0-RTT data The 0-RTT data can be replayed by adversaries. That data may trigger queries by a recursive resolver to 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 "DNS Privacy Considerations" [RFC7626]. The attack is partially mitigated by reducing the observability of this traffic. However, the risk is amplified for 0-RTT data, because the attacker might replay it at chosen times, several times. The recommendation for TLS 1.3 [RFC8446] is that the capability to use 0-RTT data should be turned off by default, and 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)?9.2. Privacy Issues With Session Resume The QUIC session resume mechanism reduces the cost of re-establishing sessions and enables 0-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, clientsHuitema, et al. Expires January 13, 2022 [Page 16]
Internet-Draft DNS over Dedicated QUIC July 2021 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 performance benefits. This evaluation will obviously depend on the level of trust between client and server.9.3. 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 inSection 6.4 to mitigate this attack.10. IANA Considerations10.1. 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 [RFC7301]. The "doq" string identifies DoQ: Protocol: DoQ Identification Sequence: 0x64 0x6F 0x71 ("doq") Specification: This document10.2. Reservation of Dedicated Port Port 853 is currently reserved for 'DNS query-response protocol run over TLS/DTLS' [RFC7858]. However, the specification for DNS over DTLS (DoD) [RFC8094] is experimental, limited to stub to resolver,Huitema, et al. Expires January 13, 2022 [Page 17]
Internet-Draft DNS over Dedicated QUIC July 2021 and no implementations or deployments currently exist to our knowledge (even though several years have passed since the specification was published). This specification proposes to additionally reserve the use of port 853 for DoQ. Whilst [RFC8094] did not specify the use of an ALPN for DoD, DoQ requires the use of the "doq" ALPN and is therefore de- muxable from DoD. IANA is requested 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]. Service Name dns-over-quic Port Number 853 Transport Protocol(s) UDP Assignee IESG Contact IETF Chair Description DNS query-response protocol run over QUIC Reference This document10.2.1. Port number 784 for experimentations (RFC EDITOR NOTE: THIS SECTION TO BE REMOVED BEFORE PUBLICATION) Early experiments MAY use port 784. This port is marked in the IANA registry as unassigned. (Note that version in -02 of this draft experiments were directed to use port 8853.)11. Acknowledgements This document liberally borrows text from the HTTP-3 specification [I-D.ietf-quic-http] edited by Mike Bishop, and from the DoT specification [RFC7858] authored by Zi Hu, Liang Zhu, John Heidemann, Allison Mankin, Duane Wessels, and Paul Hoffman. The privacy issue with 0-RTT data and session resume were analyzed by Daniel Kahn Gillmor (DKG) in a message to the IETF "DPRIVE" working group [DNS0RTT]. Thanks to Tony Finch for an extensive review of the initial version of this draft. Reviews by Paul Hoffman and interoperability tests conducted by Stephane Bortzmeyer helped improve the definition of the protocol.Huitema, et al. Expires January 13, 2022 [Page 18]
Internet-Draft DNS over Dedicated QUIC July 202112. References12.1. Normative References [I-D.ietf-dnsop-rfc8499bis] Hoffman, P. and K. Fujiwara, "DNS Terminology",draft-ietf-dnsop-rfc8499bis-02 (work in progress), June 2021. [I-D.ietf-dprive-xfr-over-tls] Toorop, W., Dickinson, S., Sahib, S., Aras, P., and A. Mankin, "DNS Zone Transfer-over-TLS",draft-ietf-dprive-xfr-over-tls-12 (work in progress), May 2021. [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>. [RFC1995] Ohta, M., "Incremental Zone Transfer in DNS",RFC 1995, DOI 10.17487/RFC1995, August 1996, <https://www.rfc-editor.org/info/rfc1995>. [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>. [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms for DNS (EDNS(0))", STD 75,RFC 6891, DOI 10.17487/RFC6891, April 2013, <https://www.rfc-editor.org/info/rfc6891>. [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>. [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>.Huitema, et al. Expires January 13, 2022 [Page 19]
Internet-Draft DNS over Dedicated QUIC July 2021 [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>. [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>. [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>. [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase inRFC2119 Key Words",BCP 14,RFC 8174, DOI 10.17487/RFC8174, May 2017, <https://www.rfc-editor.org/info/rfc8174>. [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>. [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>. [RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based Multiplexed and Secure Transport",RFC 9000, DOI 10.17487/RFC9000, May 2021, <https://www.rfc-editor.org/info/rfc9000>. [RFC9001] Thomson, M., Ed. and S. Turner, Ed., "Using TLS to Secure QUIC",RFC 9001, DOI 10.17487/RFC9001, May 2021, <https://www.rfc-editor.org/info/rfc9001>.12.2. 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>.Huitema, et al. Expires January 13, 2022 [Page 20]
Internet-Draft DNS over Dedicated QUIC July 2021 [I-D.ietf-dprive-rfc7626-bis] Wicinski, T., "DNS Privacy Considerations",draft-ietf-dprive-rfc7626-bis-09 (work in progress), March 2021. [I-D.ietf-quic-http] Bishop, M., "Hypertext Transfer Protocol Version 3 (HTTP/3)",draft-ietf-quic-http-34 (work in progress), February 2021. [I-D.ietf-quic-recovery] Iyengar, J. and I. Swett, "QUIC Loss Detection and Congestion Control",draft-ietf-quic-recovery-34 (work in progress), January 2021. [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. Cheshire, "Internet Assigned Numbers Authority (IANA) Procedures for the Management of the Service Name and Transport Protocol Port Number Registry",BCP 165,RFC 6335, DOI 10.17487/RFC6335, August 2011, <https://www.rfc-editor.org/info/rfc6335>. [RFC7626] Bortzmeyer, S., "DNS Privacy Considerations",RFC 7626, DOI 10.17487/RFC7626, August 2015, <https://www.rfc-editor.org/info/rfc7626>. [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section",BCP 205,RFC 7942, DOI 10.17487/RFC7942, July 2016, <https://www.rfc-editor.org/info/rfc7942>. [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>. [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>.12.3. URIs [1]https://github.com/AdguardTeam/DnsLibs [2]https://github.com/AdguardTeam/dnsproxyHuitema, et al. Expires January 13, 2022 [Page 21]
Internet-Draft DNS over Dedicated QUIC July 2021 [3]https://github.com/AdguardTeam/coredns [4]https://github.com/ameshkov/dnslookup [5]https://github.com/private-octopus/quicdoq [6]https://github.com/private-octopus/picoquic [7]https://github.com/DNS-OARC/flamethrower/tree/dns-over-quic [8]https://github.com/aiortc/aioquic [9]https://adguard.com/en/blog/dns-over-quic.htmlAuthors' Addresses Christian Huitema Private Octopus Inc. 427 Golfcourse Rd Friday Harbor WA 98250 U.S.A Email: huitema@huitema.net Sara Dickinson Sinodun IT Oxford Science Park Oxford OX4 4GA U.K. Email: sara@sinodun.com Allison Mankin Salesforce Email: allison.mankin@gmail.comHuitema, et al. Expires January 13, 2022 [Page 22]
Datatracker
draft-ietf-dprive-dnsoquic-03
This is an older version of an Internet-Draft that was ultimately published asRFC 9250.
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| Authors | Christian Huitema,Sara Dickinson,Allison Mankin | ||
| Replaces | draft-huitema-dprive-dnsoquic | ||
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| Additional resources | Mailing list discussion |