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2 DNSOP Working Group R. Bellis
3 Internet-Draft ISC
4 Updates: RFC 2845, RFC 2931 (if P. van Dijk
5 approved) (if approved) R. Gacogne
6 Intended status: Standards Track PowerDNS
7 Expires: January 4, 2018 July 03, 2017
9 DNS X-Proxied-For
10 draft-bellis-dnsop-xpf-02
12 Abstract
14 It is becoming more commonplace to install front end proxy devices in
15 front of DNS servers to provide (for example) load balancing or to
16 perform transport layer conversions.
18 This document defines a meta resource record that allows a DNS server
19 to receive information about the client's original transport protocol
20 parameters when supplied by trusted proxies.
22 Status of This Memo
24 This Internet-Draft is submitted in full conformance with the
25 provisions of BCP 78 and BCP 79.
27 Internet-Drafts are working documents of the Internet Engineering
28 Task Force (IETF). Note that other groups may also distribute
29 working documents as Internet-Drafts. The list of current Internet-
30 Drafts is at http://datatracker.ietf.org/drafts/current/.
32 Internet-Drafts are draft documents valid for a maximum of six months
33 and may be updated, replaced, or obsoleted by other documents at any
34 time. It is inappropriate to use Internet-Drafts as reference
35 material or to cite them other than as "work in progress."
37 This Internet-Draft will expire on January 4, 2018.
39 Copyright Notice
41 Copyright (c) 2017 IETF Trust and the persons identified as the
42 document authors. All rights reserved.
44 This document is subject to BCP 78 and the IETF Trust's Legal
45 Provisions Relating to IETF Documents
46 (http://trustee.ietf.org/license-info) in effect on the date of
47 publication of this document. Please review these documents
48 carefully, as they describe your rights and restrictions with respect
49 to this document. Code Components extracted from this document must
50 include Simplified BSD License text as described in Section 4.e of
51 the Trust Legal Provisions and are provided without warranty as
52 described in the Simplified BSD License.
54 Table of Contents
56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
57 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
58 3. Description . . . . . . . . . . . . . . . . . . . . . . . . . 3
59 3.1. Proxy Processing . . . . . . . . . . . . . . . . . . . . 3
60 3.2. Server Processing . . . . . . . . . . . . . . . . . . . . 4
61 3.3. Wire Format . . . . . . . . . . . . . . . . . . . . . . . 4
62 3.4. Presentation Format . . . . . . . . . . . . . . . . . . . 5
63 3.5. Signed DNS Requests . . . . . . . . . . . . . . . . . . . 6
64 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
65 5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 6
66 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
67 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
68 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
69 8.1. Normative References . . . . . . . . . . . . . . . . . . 7
70 8.2. Informative References . . . . . . . . . . . . . . . . . 7
71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
73 1. Introduction
75 It is becoming more commonplace to install front end proxy devices in
76 front of DNS servers [RFC1035] to provide load balancing or to
77 perform transport layer conversions (e.g. to add DNS over TLS
78 [RFC7858] to a DNS server that lacks native support).
80 This has the unfortunate side effect of hiding the clients' source IP
81 addresses from the server, making it harder to employ server-side
82 technologies that rely on knowing those addresses (e.g. ACLs, DNS
83 Response Rate Limiting, etc).
85 This document defines a DNS meta resource record (RR) that allows a
86 DNS server to receive information about the client's original
87 transport protocol parameters when supplied by trusted proxies.
89 Whilst in some circumstances it would be possible to re-use the
90 Client Subnet EDNS Option [RFC7871] to carry a subset of this
91 information, a new RR is defined to allow both this feature and the
92 Client Subnet Option to co-exist in the same packet.
94 2. Terminology
96 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
97 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
98 "OPTIONAL" in this document are to be interpreted as described in BCP
99 14 [RFC2119] [RFC8174] when, and only when, they appear in all
100 capitals, as shown here.
102 The word "proxy" in this document means a network component that sits
103 on the inbound query path in front of a recursive or authoritative
104 DNS server, receiving DNS queries from clients and dispatching them
105 to local servers. This is to distinguish these from a "forwarder"
106 since that term is usually understood to describe a network component
107 that sits on the outbound query path of a client.
109 3. Description
111 The XPF RR contains the entire 5-tuple of (protocol, source address,
112 destination address, source port and destination port) of the packet
113 received from the client by the proxy.
115 The presence of the source address supports use of ACLs based on the
116 client's IP address.
118 The source port allows for ACLs to support Carrier Grade NAT whereby
119 different end-users might share a single IP address.
121 The destination address supports scenarios where the server behaviour
122 depends upon the packet destination (e.g. BIND view's "match-
123 destinations" option)
125 The protocol and destination port fields allow server behaviour to
126 vary depending on whether DNS over TLS [RFC7858] or DNS over DTLS
127 [RFC8094] are in use.
129 3.1. Proxy Processing
131 Proxies MUST append this RR to the Additional Section of each request
132 packet received (and update the ARCOUNT field accordingly) before
133 sending it to the intended DNS server.
135 If this RR is already present in an incoming request it MUST be
136 stripped from the request unless the request was received from an
137 upstream proxy that is itself white-listed by the receiving proxy
138 (i.e. if the proxies are configured in a multi-tier architecture), in
139 which case the original value the RRs MUST be preserved.
141 Where multiple XPF RRs to appear in a request their ordering MUST
142 also be preserved.
144 << TODO: what about truncation on the client -> server path? >>
146 3.2. Server Processing
148 When this RR is received from a white-listed client the DNS server
149 SHOULD use the transport information contained therein in preference
150 to the packet's own transport information for any data processing
151 logic (e.g. ACLs) that would otherwise depend on the latter.
153 If this RR is received from a non-white-listed client the server MUST
154 return a REFUSED response.
156 If a server finds this RR anywhere other than in the Additional
157 Section of a request it MUST return a REFUSED response.
159 If the value of the RR's IP version field is not understood by the
160 server it MUST return a REFUSED response.
162 If the length of the IP addresses contained in the RR are not
163 consistent with that expected for the given IP version then the
164 server MUST return a FORMERR response.
166 Servers MUST NOT send this RR in DNS responses.
168 3.3. Wire Format
170 The XPF RR is formatted like any standard RR, but none of the fields
171 except RDLENGTH and RDATA have any meaning in this specification.
172 All multi-octet fields are transmitted in network order (i.e. big-
173 endian).
175 The required values of the RR header fields are as follows:
177 NAME: MUST contain a single 0 octet (i.e. the root domain).
179 TYPE: MUST contain TBD1 (XPF).
181 CLASS: MUST contain 1 (IN).
183 TTL: MUST contain 0 (zero).
185 RDLENGTH: specifies the length in octets of the RDATA field.
187 The RDATA of the XPF RR is as follows:
189 +0 (MSB) +1 (LSB)
190 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
191 0: | Unused | IP Version | Protocol |
192 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
193 2: | Source Address Octet 0 | ... |
194 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
195 | ... /// |
196 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
197 | Destination Address Octet 0 | ... |
198 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
199 | ... /// |
200 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
201 | Source Port |
202 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
203 | Destination Port |
204 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
206 Unused: Currently reserved. These bits MUST be zero unless redefined
207 in a subsequent specification.
209 IP Version: The IP protocol version number used by the client, as
210 defined in the IANA IP Version Number Registry [IANA-IP].
211 Implementations MUST support IPv4 (4) and IPv6 (6).
213 Protocol: The Layer 4 protocol number (e.g. UDP or TCP) as defined
214 in the IANA Protocol Number Registry [IANA-PROTO].
216 Source Address: The source IP address of the client.
218 Destination Address: The destination IP address of the request, i.e.
219 the IP address of the proxy on which the request was received.
221 Source Port: The source port used by the client.
223 Destination Port: The destination port of the request.
225 The length of the Source Address and Destination Address fields will
226 be variable depending on the IP Version in use.
228 3.4. Presentation Format
230 Since this is a "meta" RR that cannot appear in master format zone
231 files no presentation format is defined.
233 3.5. Signed DNS Requests
235 Any XPF RRs found in a packet MUST be ignored for the purposes of
236 verifying any signatures used for Secret Key Transaction
237 Authentication for DNS [RFC2845] or DNS Request and Transaction
238 Signatures (SIG(0)) [RFC2931].
240 Similarly, if either TSIG or SIG(0) are configured between the proxy
241 and server then any XPF RRs MUST be ignored when the proxy calculates
242 the packet signature.
244 4. Security Considerations
246 If the white-list of trusted proxies is implemented as a list of IP
247 addresses, the server administrator MUST have the ability to
248 selectively disable this feature for any transport where there is a
249 possibility of the proxy's source address being spoofed.
251 This does not mean to imply that use over UDP is impossible - if for
252 example the network architecture keeps all proxy-to-server traffic on
253 a dedicated network and clients have no direct access to the servers
254 then the proxies' source addresses can be considered unspoofable.
256 5. Privacy Considerations
258 Used incorrectly, this RR could expose internal network information,
259 however it is not intended for use on proxy / forwarder devices that
260 sit on the client-side of a DNS request.
262 This specification is only intended for use on server-side proxy
263 devices that are under the same administrative control as the DNS
264 servers themselves. As such there is no change in the scope within
265 which any private information might be shared.
267 Use other than as described above would be contrary to the principles
268 of [RFC6973].
270 6. IANA Considerations
272 << a copy of the RFC 6895 IANA RR TYPE application template will
273 appear here >>
275 7. Acknowledgements
277 Mark Andrews, Robert Edmonds, Duane Wessels
279 8. References
281 8.1. Normative References
283 [IANA-IP] IANA, "IANA IP Version Registry", n.d.,
284 .
286 [IANA-PROTO]
287 IANA, "IANA Protocol Number Registry", n.d.,
288 .
290 [RFC1035] Mockapetris, P., "Domain names - implementation and
291 specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
292 November 1987, .
294 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
295 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
296 RFC2119, March 1997,
297 .
299 [RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
300 Wellington, "Secret Key Transaction Authentication for DNS
301 (TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
302 .
304 [RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
305 ( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
306 2000, .
308 [RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
309 Morris, J., Hansen, M., and R. Smith, "Privacy
310 Considerations for Internet Protocols", RFC 6973, DOI
311 10.17487/RFC6973, July 2013,
312 .
314 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
315 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
316 May 2017, .
318 8.2. Informative References
320 [RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
321 and P. Hoffman, "Specification for DNS over Transport
322 Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
323 2016, .
325 [RFC7871] Contavalli, C., van der Gaast, W., Lawrence, D., and W.
326 Kumari, "Client Subnet in DNS Queries", RFC 7871, DOI
327 10.17487/RFC7871, May 2016,
328 .
330 [RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
331 Transport Layer Security (DTLS)", RFC 8094, DOI 10.17487/
332 RFC8094, February 2017,
333 .
335 Authors' Addresses
337 Ray Bellis
338 Internet Systems Consortium, Inc.
339 950 Charter Street
340 Redwood City CA 94063
341 USA
343 Phone: +1 650 423 1200
344 Email: ray@isc.org
346 Peter van Dijk
347 PowerDNS.COM B.V.
348 Den Haag
349 The Netherlands
351 Email: peter.van.dijk@powerdns.com
353 Remi Gacogne
354 PowerDNS.COM B.V.
355 Den Haag
356 The Netherlands
358 Email: remi.gacogne@powerdns.com