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Versions: 00 01                                                         
Internet Engineering Task Force (IETF)              Phillip Hallam-Baker
Internet-Draft                                         Comodo Group Inc.
Intended Status: Standards Track                        November 7, 2014
Expires: May 11, 2015


                              Private-DNS
                    draft-hallambaker-privatedns-01

Abstract

   This document describes Private DNS, a transport security mechanism
   for the DNS protocol. The mechanism may be employed to secure
   communication between a client and its resolver or between a resolver
   and an authoritative server.

   Service binding including key exchange is effected using the JSON
   Service Connect (JCX) Protocol. DNS protocol messages are wrapped in
   a new framing protocol.

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 http://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."

Copyright Notice

   Copyright (c) 2014 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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   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.







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Table of Contents

   1.  Introduction.  . . . . . . . . . . . . . . . . . . . . . . . .  3
      1.1.  Related Work  . . . . . . . . . . . . . . . . . . . . . .  3
      1.2.  Terminology . . . . . . . . . . . . . . . . . . . . . . .  3
      1.3.  Defined Terms . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Architecture . . . . . . . . . . . . . . . . . . . . . . . . .  4
      2.1.  Service Connection  . . . . . . . . . . . . . . . . . . .  4
         2.1.1.  Example: Public Resolver . . . . . . . . . . . . . .  5
         2.1.2.  Example: Hybrid Resolver . . . . . . . . . . . . . .  6
      2.2.  Query Protocol Binding  . . . . . . . . . . . . . . . . .  9
         2.2.1.  Message Binding. . . . . . . . . . . . . . . . . . . 10
         2.2.2.  Query Protocol Example . . . . . . . . . . . . . . . 10
         2.2.3.  Authentication Conformance . . . . . . . . . . . . . 13
         2.2.4.  Handling Multiple Requests . . . . . . . . . . . . . 14
   3.  Service Connection and Key Exchangee . . . . . . . . . . . . . 14
      3.1.  UDP Binding . . . . . . . . . . . . . . . . . . . . . . . 14
      3.2.  HTTP Binding  . . . . . . . . . . . . . . . . . . . . . . 15
   4.  Security Considerationsns  . . . . . . . . . . . . . . . . . . 15
      4.1.  Confidentiality . . . . . . . . . . . . . . . . . . . . . 15
      4.2.  Integrity . . . . . . . . . . . . . . . . . . . . . . . . 15
      4.3.  Access  . . . . . . . . . . . . . . . . . . . . . . . . . 15
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   6.  Acnowledgements  . . . . . . . . . . . . . . . . . . . . . . . 15
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
      7.1.  Normative References  . . . . . . . . . . . . . . . . . . 16
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 16



























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1. Introduction.

   Recent events have required urgent consideration of privacy concerns
   in Internet protocols. In particular the lack of confidentiality
   controls in the DNS [RFC1035] protocol is of considerable concern.

   This document describes Private-DNS, a security enhancement for the
   DNS protocol that meets the principal use cases and requirements set
   out in [I-D.hallambaker-dnse]. This enhancement provides for
   encryption and authentication of the DNS protocol messages.

   Private-DNS makes use of the JSON Service Connect (JCX) Protocol [I-
   D.hallambaker-wsconnect] and the UYFM framing protocol described in
   that specification.

1.1. Related Work

   The proposal approach compliments the integrity controls provided by
   DNSSEC [RFC4033]. While both provide integrity controls, the controls
   provided by DNSSEC are based on digital signatures while this
   proposal provides controls based on a Message Authentica Code
   technique.

   Like the Omnibroker protocol [I-D.hallambaker-omnibroker], this
   proposal is built on JCX [I-D.hallambaker-wsconnect] but offers a low
   level interface to the DNS protocol alone as opposed to a high level
   interface to generalized discovery services. A client would use the
   DNSE-JX interface in cases where retrieval of specific DNS resource
   records is required. The OmniBroker protocol would be used in cases
   where the client delegates the choice of discovery strategy to the
   OmniBroker service.

1.2. Terminology

   The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD,
   SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this
   document, are to be interpreted as described in [RFC2119]

1.3. Defined Terms

   [[These terms are deliberately left blank here or else we will spend
   time wordsmithing the defined term definitions rather than looking at
   the protocol.]











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      Authoritative DNS Server

      Caching Recursive Resolver

      DNS

      DNS Client

      Recursive Resolver

      Stub Resolver

2. Architecture

   PRIVATE-DNS has two parts

      *  Service Connection

      *  DNS message encapsulation

   In PRIVATE-DNS, the service connection is provided by the existing
   [I-D.hallambaker-wsconnect] proposal. The DNS message encapsulation
   is new and supports encryption and authentication of the DNS protocol
   messages.

   To make use of PRIVATE-DNS a client first establishes a connection to
   a DNS server (resolver or authoritative) using the connection
   protocol. Once a client has established a connection it MAY use it to
   make as many queries as desired until either the connection context
   expires or is cancelled by the service.

   The Service Connection and Query Service MAY be operated on the same
   host or on separate hosts.

2.1. Service Connection

   The service connection mechanism is responsible for establishing a
   connection context between a client and a service. The connection
   context comprises:

      *  A security context (opaque identifier, key, algorithm choice)
         between the client and the connection service

      *  One or more query host connection contexts, each
         comprisingNetwork connection description (IP address, Port,
         Protocol, transport)Security Context  (opaque identifier, key,
         algorithm choice) between the client and the query host

   The PRIVATE-DNS proposal is designed on the assumption that Service
   Connection transactions are relatively infrequent and thus the
   efficiency of the Service Connection protocol is not a major concern.



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   Accordingly the Service Connection protocol is implemented as a
   JSON/REST Web Service over HTTP. While of an efficient encoding (e.g.
   [I-D.hallambaker-jsonbcd] would permit a more efficient
   implementation of the protocol using UDP, such an approach would be
   vulnerable to Denial of Service attacks against the service unless
   appropriate countermeasures were taken. For example use of a 'cookie'
   approach to prove the validity of the purported request source
   address.

   A service connection MAY return a host connection set that includes
   multiple protocol and/or transport options. This has the important
   consequence that it allows new message formats or a transition to an
   entirely new protocol to be effected by simply defining a new
   identifier.

   A distinction is drawn between a connection to a service and a
   connection to a host. A connection to a host is a relationship to a
   specific instance of a service with a distinct IP address. A
   connection to a service is a relationship to a set of hosts. This
   distinction is an important one for Denial of Service mitigation. A
   DNS service need not publish the same network connection description
   to every client. This permits a service to mitigate DoS attacks by
   filtering query requests by IP address, a strategy that is greatly
   enhanced by the large address space of IPv6.

   Different configurations of the Service Connection service allow a
   DNS service to meet different combinations of security requirements.
   For example the Public Resolver described in [U-PUBLIC] would not
   require authentication of the client to the service but this would be
   required for the Subscriber, Private and Hybrid Resolvers described
   in [U-SUBSCRIBER], [U-PRIVATE] and [U-HYBRID].].

2.1.1. Example: Public Resolver

   Following the use case [[U-PUBLIC] described in [I-D.hallambaker-
   dnse], Alice buys a laptop for her personal use at home. To ensure
   the privacy of her DNS connection she selects example.com, a public
   resolver that provides DNS service without requiring any form of
   subscription or registration.

   During the initial configuration process, the machine uses the local
   DNS advertised in the DCHP configuration for the first and last time
   for discovery of the Service Connection Service of example.com.

   Having discovered a Service Connection Service, the client requests a
   service provider for the PRIVATE-DNS service by establishing a TLS
   connection to indicated server. The server returns a TLS Certificate
   that meets the authentication criteria of the client. Once the TLS
   connection is established, an anonymous client connection is
   established.




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   POST /.well-known/sxs-connect/ HTTP/1.1
   Content-Type: application/json;charset=UTF-8
   Cache-Control: no-store
   Host: localhost:8080
   Content-Length: 226
   Expect: 100-continue

   {
     "BindRequest": {
       "Service": ["private-dns-resolver"],
       "Encryption": ["A128CBC",
         "A256CBC",
         "A128GCM",
         "A256GCM"],
       "Authentication": ["HS256",
         "HS384",
         "HS512",
         "HS256T128"]}}

   Since the example.com service does not require authentication, the
   request is granted immediately and the necessary host connection
   parameters returned immediately:

   HTTP/1.1 OK Success
   Content-Length: 578
   Date: Tue, 14 Oct 2014 19:34:07 GMT
   Server: Microsoft-HTTPAPI/2.0

   {
     "TicketResponse": {
       "Status": 200,
       "StatusDescription": "Success",
       "Cryptographic": [],
       "Service": [{
           "Service": "private-dns-resolver",
           "Name": "localhost",
           "Port": 9090,
           "Priority": 100,
           "Weight": 100,
           "Transport": "UDP",
           "Cryptographic": {
             "Secret": "
   qJq11EcqrvWe2WfyDC2FLg",
             "Encryption": "A128CBC",
             "Authentication": "HS256T128",
             "Ticket": "
   Tpau1M6HuDjwuzwLhw9SWPi9Qx1zfkcQmaj0YRnKV-JCRv2kld06zyobptvuA2F6
   JGXkM0JGnSVWOPtn235wnIljsg7pZg25vPiofgPuZNY"}}]}}






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2.1.2. Example: Hybrid Resolver

   Following the use case [U-HYBRID], Alice decides to use her personal
   computer for work under her employer's 'Bring Your Own Device'
   program. Alice needs access to multiple services within her
   employer's intranet.

   Her system administrator issues her an account name [TBS], a one time
   use PIN [TBS] and the DNS address of the service connection service
   byod.example.net. Having established a TLS connection as before, the
   client makes an initial request:

   POST /.well-known/sxs-connect/ HTTP/1.1
   Content-Type: application/json;charset=UTF-8
   Cache-Control: no-store
   Host: localhost:8080
   Content-Length: 352
   Expect: 100-continue

   {
     "OpenPINRequest": {
       "Service": ["private-dns-resolver"],
       "Encryption": ["A128CBC",
         "A256CBC",
         "A128GCM",
         "A256GCM"],
       "Authentication": ["HS256",
         "HS384",
         "HS512",
         "HS256T128"],
       "Account": "alice",
       "Domain": "example.com",
       "HaveDisplay": false,
       "Challenge": "
   c1CfkTu5XVVLuT2gxaVFjA"}}

   The server provides a challenge for verifying the one time use PIN.

   HTTP/1.1 281 Pin code required
   Content-Length: 511
   Date: Tue, 14 Oct 2014 19:34:07 GMT
   Server: Microsoft-HTTPAPI/2.0

   {
     "OpenPINResponse": {
       "Status": 281,
       "StatusDescription": "Pin code required",
       "Challenge": "
   9W8IxZw-bEQBbnWBWSM9Vw",
       "ChallengeResponse": "
   2FPG-xEBcYIo2137in1wxnhqUxmhygB6SsfvzhtYTXE",



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       "Cryptographic": {
         "Secret": "
   KATjv8Nkix4ITrexxyGBsQ",
         "Encryption": "A128CBC",
         "Authentication": "HS256",
         "Ticket": "
   vnBXaykCug2eeRVsH-CEqhR3qJvvRQEmm4a1Ldh-G-Zqj7acqA9NtLYVCnJflaWs
   Sd2cMi8-mqdX-5VRVAMFfrxjdaQx4uq7mcr59OUFMRGSb11ZXcMkan9h142NUjmI
   t1MnYRsXWNdFndPE19zMDA"}}}

   Having obtained the challenge value from the service, the client
   resends the initial request, having authenticated it this time under
   the challenge and one time PIN:

   POST /.well-known/sxs-connect/ HTTP/1.1
   Content-Type: application/json;charset=UTF-8
   Cache-Control: no-store
   Session: Value=uuPiOYOP7kpM3xrYXMWa9JttlhR-VSf604UR6iFbPpY;
     Id=vnBXaykCug2eeRVsH-CEqhR3qJvvRQEmm4a1Ldh-G-Zqj7acqA9NtLYVCnJf
     laWsSd2cMi8-mqdX-5VRVAMFfrxjdaQx4uq7mcr59OUFMRGSb11ZXcMkan9h142
     NUjmIt1MnYRsXWNdFndPE19zMDA
   Host: localhost:8080
   Content-Length: 137
   Expect: 100-continue

   {
     "TicketRequest": {
       "Service": ["private-dns-resolver"],
       "ChallengeResponse": "
   S_t81MumUqouGaxWQIT1nOJfkUaE1YcXNwQJXkXuqbM"}}

   The server returns a set of host connections for the requested
   services. The scope of the PRIVATE-DNS service is limited to the
   domain tree *.example.net:

   HTTP/1.1 OK Success
   Content-Length: 858
   Date: Tue, 14 Oct 2014 19:34:07 GMT
   Server: Microsoft-HTTPAPI/2.0

   {
     "TicketResponse": {
       "Status": 200,
       "StatusDescription": "Success",
       "Cryptographic": [{
           "Protocol": "sxs-connect",
           "Secret": "
   UDvvBM8fE42zCs4g2mVnjw",
           "Encryption": "A128CBC",
           "Authentication": "HS256",
           "Ticket": "



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   WZDn4kOYJCrx6LnhuWwH3U00_aCJBcNRcUZyIV8L_hWVGjtvF8UEWTL1SgRXYcSE
   zVBR9v_ER4HpSEwkYgKLX2crAo2fZMZlqyRW9kh5s88"}],
       "Service": [{
           "Service": "private-dns-resolver",
           "Name": "localhost",
           "Port": 9090,
           "Priority": 100,
           "Weight": 100,
           "Transport": "UDP",
           "Cryptographic": {
             "Secret": "
   IdvuBOccKHwnPFIByHaU6w",
             "Encryption": "A128CBC",
             "Authentication": "HS256T128",
             "Ticket": "
   xMVgwd-i2nHjbmZDUowVx3yAUHl_gHuh7aNzxVArYepIBMHcpaaNGw4goUsZTMby
   EOUinBXDXkmVE66ExnA4H4Mgd9GSu48ReM9lKtrff98"}}]}}

2.2. Query Protocol Binding

   The Query Protocol Binding is designed to efficiently support the
   following features:

      *  Encryption

      *  Prevent use in an Denial of Service attack.

      *  Authentication

      *  Multiple DNS queries and responses per PRIVATE-DNS Query [[*]

      *  Multiple packet responses [[*]

   The features marked [[*] are not essential for the purpose of meeting
   the privacy requirements but considerably improve the efficiency and
   flexibility of the DNS protocol. In particular the ability to make
   multiple DNS queries in a single transaction over UDP transport
   enables the use of novel discovery techniques without impact on
   performance.

   While the privacy requirements may be met through use of encryption
   alone, any encoding that does not provide authentication of requests
   allows a service to be used as an attack vector in a denial of
   service attack on third parties.

   The Query Protocol Binding wraps the [RFC1035] message structure
   rather than eliminating parts that are redundant. For example, the
   Query Protocol Binding Transaction ID which has a minimum length of
   128 bits supplements rather than replaces the DNS message transaction
   ID of 16 bytes.




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2.2.1. Message Binding.

   To ensure access to the DNS service in any network circumstance where
   the protocol is intentionally blocked, two message transports are
   specified:

      UDP transport
         The prefered transport providing low latency service.

      HTTP Web Service

   In a typical network environment where a MTU of at least 1280 bytes
   is supported, the UDP transport supports DNS request messages of at
   least 1100 bytes and responses of at least 18000 bytes.

   Both transport bindings are specified in [I-D.hallambaker-wsconnect].

2.2.2. Query Protocol Example

   Having established a connection to a Private-DNS service, the client
   from the first example performs a DNS query:


   www.example.com ? A

2.2.2.1. Key Derrivation

   [TBS at the moment there is no key derrivation function specified and
   the same key is used for encryption and authentication. This is a
   weak approach architecturally as a compromise of one algorithm puts
   the other at risk and should be fixed. Rather than use k as the key
   we should use MAC ("encrypt", k) and MAC ("decrypt", k) or something
   similar. However doing that right requires consulting past RFCs to
   find the right derrivation function.]

   Ticket value is:

   4e 96 ae d4 ce 87 b8 38  f0 bb 3c 0b 87 0f 52 58
   f8 bd 43 1d 73 7e 47 10  99 a8 f4 61 19 ca 57 e2
   42 46 fd a4 95 dd 3a cf  2a 1b a6 db ee 03 61 7a
   24 65 e4 33 42 46 9d 25  56 38 fb 67 db 7e 70 9c
   89 63 b2 0e e9 66 0d b9  bc f8 a8 7e 03 ee 64 d6












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   Master key is:

   a8 9a b5 d4 47 2a ae f5  9e d9 67 f2 0c 2d 85 2e

   Authentication key is TBS (Master)

   a8 9a b5 d4 47 2a ae f5  9e d9 67 f2 0c 2d 85 2e

   Encryption key is TBS (Master)

   a8 9a b5 d4 47 2a ae f5  9e d9 67 f2 0c 2d 85 2e

2.2.2.2. Request

   The DNS Request is: [TBS this is a placeholder]

   ;; QUESTION SECTION:
   example.com.                   IN      A

   In hex:

   24 1a 01 00 00 01 00 00  00 00 00 00 03 77 77 77
   07 65 78 61 6d 70 6c 65  03 63 6f 6d 00 00 01 00
   01

   The plaintext payload is


   Segment(0)
   Type code:               12
   Segment length:          00 21
   Data:
   24 1a 01 00 00 01 00 00  00 00 00 00 03 77 77 77
   07 65 78 61 6d 70 6c 65  03 63 6f 6d 00 00 01 00
   01

   Note that in a real world example, the request SHOULD be padded to a
   fixed value (e.g. 1100 bytes) to prevent traffic analysis disclosing
   the message contents. for illustrative purposes, a mimimal padding is
   applied:

   The request has the transaction ID which doubles as the
   initialization vector of the encryption algorithm and ticket
   identifier prepended and the MAC value appended:










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   Transaction ID:          10 (= 16 bytes)
   34 bf 46 58 50 6b 20 7a  bb 57 71 04 94 c5 80 06
   Ticket:                  50 (= 80 bytes)
   4e 96 ae d4 ce 87 b8 38  f0 bb 3c 0b 87 0f 52 58
   f8 bd 43 1d 73 7e 47 10  99 a8 f4 61 19 ca 57 e2
   42 46 fd a4 95 dd 3a cf  2a 1b a6 db ee 03 61 7a
   24 65 e4 33 42 46 9d 25  56 38 fb 67 db 7e 70 9c
   89 63 b2 0e e9 66 0d b9  bc f8 a8 7e 03 ee 64 d6
   Encrypted Data:          00 30 (= 48 bytes)
   fd e5 f6 48 69 ce 6a bb  b3 d4 ef 86 06 e9 79 f7
   82 3e 86 d2 ac c5 e9 f4  b6 f3 eb a5 02 5c bf 5d
   07 eb 31 cb 2b 29 90 a9  c7 96 cd bd a9 71 a1 7a
   MAC:                     10 (= 16 bytes)
   b9 1d e6 e4 63 93 04 d8  ff 26 8e 17 fa a9 84 aa

2.2.2.3. Response

   The recursive resolver locates the records and returns the response.

   The DNS Response is [TBS this is a placeholder]

   ;; ANSWER SECTION:
   example.com.            38400   IN      A       192.168.1.20

   ;; AUTHORITY SECTION:
   example.com.            38400   IN      NS      ns1.example.com.

   ;; ADDITIONAL SECTION:
   ns1.example.com.        38400   IN      A       192.168.1.28

   In hex:

   24 1a 81 80 00 01 00 03  00 00 00 00 03 77 77 77
   06 67 6f 6f 67 6c 65 03  63 6f 6d 00 00 01 00 01
   c0 0c 00 05 00 01 00 05  28 39 00 12 03 77 77 77
   01 6c 06 67 6f 6f 67 6c  65 03 63 6f 6d 00 c0 2c
   00 01 00 01 00 00 00 e3  00 04 42 f9 59 63 c0 2c
   00 01 00 01 00 00 00 e3  00 04 42 f9 59 68

   The plaintext payload is the DNS response plus the MAC value of the
   request. This response is small enough to fit into a single packet.












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   Segment(0)
   Type code:               04
   Segment length:          00 20
   Data:
   b9 1d e6 e4 63 93 04 d8  ff 26 8e 17 fa a9 84 aa
   7d ff 40 00 16 91 70 d1  0a 1a 19 a5 1f 3a dc cf
   Segment(1)
   Type code:               12
   Segment length:          00 5e
   Data:
   24 1a 81 80 00 01 00 03  00 00 00 00 03 77 77 77
   06 67 6f 6f 67 6c 65 03  63 6f 6d 00 00 01 00 01
   c0 0c 00 05 00 01 00 05  28 39 00 12 03 77 77 77
   01 6c 06 67 6f 6f 67 6c  65 03 63 6f 6d 00 c0 2c
   00 01 00 01 00 00 00 e3  00 04 42 f9 59 63 c0 2c
   00 01 00 01 00 00 00 e3  00 04 42 f9 59 68

   The plaintext is encrypted and the transaction identifier and MAC
   values added. Note that in a multiple packet response, each response
   has its own MAC value:


   Transaction ID:          10 (= 16 bytes)
   8e dc 41 ba 32 9f ca 6c  b4 83 43 34 88 10 7f ed
   Index:                   01
   Max Index:               01
   Clear Response:          00 c8 (= 200)
   Encrypted Data:          00 90 (= 144 bytes)
   ce e6 31 cd 2d 48 01 07  23 77 db 99 ac e1 57 2a
   7c f1 9b 7c cd 9e 68 8d  76 97 de 99 eb d5 bb fc
   4d 17 c6 3f 9b 69 a1 e5  3a 4e 61 36 59 c6 8c 89
   5c 17 2e 8c 56 6c 49 71  0a 3a 07 3d d8 1a 18 f1
   25 ad 92 fa ef 85 b2 31  78 25 35 b8 e7 c2 c0 92
   d3 ad a9 75 1e 10 a2 4d  3d 81 99 19 43 86 3b 29
   b5 49 45 49 00 59 6b 7b  80 47 e7 fb 36 99 4b 76
   45 8d aa ba e4 04 65 0b  8f 41 2e 58 df 6a ca 41
   dc 16 c7 f9 ac 2a 74 ed  a4 84 80 1e e1 72 2d c9
   MAC:                     10 (= 16 bytes)
   49 c2 0c 8b 93 df 7f 33  4e 97 52 9a 66 2b 4f 88

2.2.3. Authentication Conformance

   A Private-DNS server MUST authenticate queries. In the case that the
   UDP binding is used, a server MUST NOT make any response should the
   verification step fail. This requirement ensures that a Private-DNS
   service cannot be used to attack other systems in a Denial of Service
   attack through use of packets with forged source addresses.






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   A service MAY provide an error response in the case that a request
   using the Web Service binding fails as the TCP/IP connection startup
   provides an adequate protection against source address forgery.

2.2.4. Handling Multiple Requests

   A Private-DNS service MUST accept requests that contain multiple
   requests. Where multiple requests are presented, each request in the
   transaction MUST have a unique DNS Transaction ID.

   A Private-DNS service MAY limit the number of responses provided.
   Responses to requests MAY be returned in any order.

3. Service Connection and Key Exchangee

   The Service Connection is established using [I-D.hallambaker-
   wsconnect]. The service identifiers for PRIVATE-DNS are as follows:

      Service Identifier
         PRIVATE-DNS

   Two host connection bindings are defined:

      UDP Binding
         The UDP binding described in [!I-D.hallambaker-wsconnect] is
         the preferred host binding. The UDP binding allows most queries
         to be completed in a single round trip with no mandatory
         delays.

      HTTP Binding
         A HTTP binding is specified for use as a last resort in
         situations where the UDP transport is not available.

3.1. UDP Binding

   The prefered host connection type is to use the message encapsulation
   format

      Protocol
         DNS

      Presentation
         PRIVATE-DNS-P

      Transport
         UDP

   Note that the omission of version numbers in the on-the-wire data
   structures is intentional. Use of the message encapsulation requires
   that the parties have previously established a host connection
   comprising the network and security parameters required to



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   communicate. The choice of message encapsulation including the
   protocol version is defined in the host connection.

   In the DNS protocol requests and responses use the same message
   structure. The encapsulation uses different structures for requests
   and responses but the payload of each structure is a sequence of
   [RFC1035] messages.

3.2. HTTP Binding

   Under certain network conditions attempts to reach the PRIVATE-DNS
   service may fail due to constraints imposed by firewalls or through
   attempted censorship. Under these conditions, HTTP [RFC2616] MAY be
   used as an alternative transport as follows:

      Protocol
         DNS

      Presentation
         POST

      Content-Type
         application/private-dns-p

      Transport
         HTTP

   A PRIVATE-DNS service offered in this fashion MUST support HTTP/1.1
   or higher. The transaction is performed as a POST request with the
   MIME content type application/private-dns-p.p.

4. Security Considerationsns

   The broad security requirements for Private-DNS are set out in [I-
   D.hallambaker-dnse].

   In due course this section will explain which of the security
   requirements is met and under which circumstances.

4.1. Confidentiality

4.2. Integrity

4.3. Access

5. IANA Considerations


6. Acnowledgements





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7. References

7.1. Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [I-D.hallambaker-omnibroker]  Hallam-Baker, P, "OmniBroker Protocol",
              Internet-Draft draft-hallambaker-omnibroker-07, 21 January
              2014.

   [RFC2616]  Fielding, R.,Gettys, J.,Mogul, J.,Frystyk, H.,Masinter,
              L.,Leach, P.,Berners-Lee, T., "Hypertext Transfer Protocol
              -- HTTP/1.1", RFC 2616, June 1999.

   [I-D.hallambaker-jsonbcd]  Hallam-Baker, P, "Binary Encodings for
              JavaScript Object Notation: JSON-B, JSON-C, JSON-D",
              Internet-Draft draft-hallambaker-jsonbcd-01, 21 January
              2014.

   [I-D.hallambaker-dnse]  Hallam-Baker, P, "Private-DNS", Internet-
              Draft draft-hallambaker-dnse-00, 21 March 2014.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, 1 November 1987.

   [RFC4033]  Arends, R.,Austein, R.,Larson, M.,Massey, D.,Rose, S.,
              "DNS Security Introduction and Requirements", RFC 4033,
              March 2005.

   [I-D.hallambaker-wsconnect]  Hallam-Baker, P, "JSON Service Connect
              (JCX) Protocol", Internet-Draft draft-hallambaker-
              wsconnect-05, 21 January 2014.

Author's Address

   Phillip Hallam-Baker
   Comodo Group Inc.

   philliph@comodo.com














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