Structured Error Data for Filtered DNS
draft-ietf-dnsop-structured-dns-error-03

DNS Operations Working Group                                     D. Wing
Internet-Draft                                                    Citrix
Updates: 8914 (if approved)                                     T. Reddy
Intended status: Standards Track                                   Nokia
Expires: 28 November 2023                                        N. Cook
                                                            Open-Xchange
                                                            M. Boucadair
                                                                  Orange
                                                             27 May 2023

                 Structured Error Data for Filtered DNS
                draft-ietf-dnsop-structured-dns-error-03

Abstract

   DNS filtering is widely deployed for various reasons, including
   network security.  However, filtered DNS responses lack information
   for end users to understand the reason for the filtering.  Existing
   mechanisms to provide explanatory details to end users cause harm
   especially if the blocked DNS response is to an HTTPS server.

   This document updates RFC 8914 by signaling client support for
   structuring the EXTRA-TEXT field of the Extended DNS Error to provide
   details on the DNS filtering.  Such details can be parsed by the
   client and displayed, logged, or used for other purposes.

About This Document

   This note is to be removed before publishing as an RFC.

   The latest revision of this draft can be found at https://ietf-wg-
   dnsop.github.io/draft-ietf-dnsop-structured-dns-error/draft-ietf-
   dnsop-structured-dns-error.html.  Status information for this
   document may be found at https://datatracker.ietf.org/doc/draft-ietf-
   dnsop-structured-dns-error/.

   Discussion of this document takes place on the dnsop Working Group
   mailing list (mailto:dnsop@ietf.org), which is archived at
   https://mailarchive.ietf.org/arch/browse/dnsop/.  Subscribe at
   https://www.ietf.org/mailman/listinfo/dnsop/.

   Source for this draft and an issue tracker can be found at
   https://github.com/ietf-wg-dnsop/draft-ietf-dnsop-structured-dns-
   error.

Wing, et al.            Expires 28 November 2023                [Page 1]
Internet-Draft            Structured DNS Error                  May 2023

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 28 November 2023.

Copyright Notice

   Copyright (c) 2023 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 carefully, as they describe your rights
   and restrictions with respect to this document.  Code Components
   extracted from this document must include Revised BSD License text as
   described in Section 4.e of the Trust Legal Provisions and are
   provided without warranty as described in the Revised BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Conventions and Definitions . . . . . . . . . . . . . . . . .   4
   3.  DNS Filtering Techniques and Their Limitations  . . . . . . .   4
   4.  I-JSON in EXTRA-TEXT Field  . . . . . . . . . . . . . . . . .   6
   5.  Protocol Operation  . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  Client Generating Request . . . . . . . . . . . . . . . .   7
     5.2.  Server Generating Response  . . . . . . . . . . . . . . .   8
     5.3.  Client Processing Response  . . . . . . . . . . . . . . .   8
   6.  Interoperation with RPZ Servers . . . . . . . . . . . . . . .   9
   7.  New Sub-Error Codes Definition  . . . . . . . . . . . . . . .  10
     7.1.  Reserved  . . . . . . . . . . . . . . . . . . . . . . . .  10
     7.2.  Network Operator Policy . . . . . . . . . . . . . . . . .  10
     7.3.  DNS Operator Policy . . . . . . . . . . . . . . . . . . .  10
   8.  Extended DNS Error Code TBA1 - Blocked by Upstream DNS
           Server  . . . . . . . . . . . . . . . . . . . . . . . . .  11

Wing, et al.            Expires 28 November 2023                [Page 2]
Internet-Draft            Structured DNS Error                  May 2023

   9.  Examples  . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  12
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
     11.1.  Media Type Registration  . . . . . . . . . . . . . . . .  13
     11.2.  New Registry for JSON Names  . . . . . . . . . . . . . .  13
     11.3.  New Registry for DNS SubError Codes  . . . . . . . . . .  15
     11.4.  New Extended DNS Error Code  . . . . . . . . . . . . . .  17
   12. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     12.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     12.2.  Informative References . . . . . . . . . . . . . . . . .  19
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

1.  Introduction

   DNS filters are deployed for a variety of reasons, e.g., endpoint
   security, parental filtering, and filtering required by law
   enforcement.  Network-based security solutions such as firewalls and
   Intrusion Prevention Systems (IPS) rely upon network traffic
   inspection to implement perimeter-based security policies and operate
   by filtering DNS responses.  In a home network, DNS filtering is used
   for the same reasons as above and additionally for parental control.
   Internet Service Providers (ISPs) typically block access to some DNS
   domains due to a requirement imposed by an external entity (e.g., law
   enforcement agency) also performed using DNS-based content filtering.

   Users of DNS services that perform filtering may wish to receive more
   explanatory information about such a filtering to resolve problems
   with the filter -- for example to contact the administrator to
   allowlist a DNS domain that was erroneously filtered or to understand
   the reason a particular domain was filtered.  With that information,
   a user can choose another network, open a trouble ticket with the DNS
   administrator to resolve erroneous filtering, log the information, or
   other uses.

   For the DNS filtering mechanisms described in Section 3 the DNS
   server can return extended error codes Blocked, Filtered, or Forged
   Answer defined in Section 4 of [RFC8914].  However, these codes only
   explain that filtering occurred but lack detail for the user to
   diagnose erroneous filterings.

   No matter which type of response is generated (forged IP address(es),
   NXDOMAIN or empty answer, even with an extended error code), the user
   who triggered the DNS query has little chance to understand which
   entity filtered the query, how to report a mistake in the filter, or
   why the entity filtered it at all.  This document describes a
   mechanism to provide such detail.

Wing, et al.            Expires 28 November 2023                [Page 3]
Internet-Draft            Structured DNS Error                  May 2023

   One of the other benefits of the approach described in this document
   is to eliminate the need to "spoof" block pages for HTTPS resources.
   This is achieved since clients implementing this approach would be
   able to display a meaningful error message, and would not need to
   connect to such a block page.  This approach thus avoids the need to
   install a local root certificate authority on those IT-managed
   devices.

   This document describes a format for computer-parsable data in the
   EXTRA-TEXT field of [RFC8914].  It updates Section 2 of [RFC8914]
   which says the information in EXTRA-TEXT field is intended for human
   consumption (not automated parsing).

   This document does not recommend DNS filtering but provides a
   mechanism for better transparency to explain to the users why some
   DNS queries are filtered.

2.  Conventions and Definitions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   This document uses terms defined in DNS Terminology [RFC8499].

   "Requestor" refers to the side that sends a request.  "Responder"
   refers to an authoritative, recursive resolver or other DNS component
   that responds to questions.

   "Encrypted DNS" refers to any encrypted scheme to convey DNS
   messages, for example, DNS-over-HTTPS [RFC8484], DNS-over-TLS
   [RFC7858], or DNS-over-QUIC [RFC9250].

   The document refers to an Extended DNS Error (EDE) using its purpose,
   not its INFO-CODE as per Table 3 of [RFC8914].  "Forged Answer",
   "Blocked", and "Filtered" are thus used to refer to "Forged Answer
   (4)", "Blocked (15)", and "Filtered (17)".

3.  DNS Filtering Techniques and Their Limitations

   DNS responses can be filtered by sending a bogus (also called
   "forged") A or AAAA response, NXDOMAIN error or empty answer, or an
   Extended DNS Error code defined in [RFC8914].  Each of these methods
   have advantages and disadvantages that are discussed below:

Wing, et al.            Expires 28 November 2023                [Page 4]
Internet-Draft            Structured DNS Error                  May 2023

   1.  The DNS response is forged to provide a list of IP addresses that
       points to an HTTP(S) server alerting the end user about the
       reason for blocking access to the requested domain (e.g.,
       malware).  When an HTTP(S) enabled domain name is blocked, the
       network security device (e.g., Customer Premises Equipment (CPE)
       or firewall) presents a block page instead of the HTTP response
       from the content provider hosting that domain.  If an HTTP
       enabled domain name is blocked, the network security device
       intercepts the HTTP request and returns a block page over HTTP.
       If an HTTPS enabled domain is blocked, the block page is also
       served over HTTPS.  In order to return a block page over HTTPS,
       man in the middle (MITM) is enabled on endpoints by generating a
       local root certificate and an accompanying (local) public/private
       key pair.  The local root certificate is installed on the
       endpoint while the network security device stores a copy of the
       private key.  During the TLS handshake, the on-path network
       security device modifies the certificate provided by the server
       and (re)signs it using the private key from the local root
       certificate.

       *  However, configuring the local root certificate on endpoints
          is not a viable option in several deployments like home
          networks, schools, Small Office/Home Office (SOHO), or Small/
          Medium Enterprise (SME).  In these cases, the typical behavior
          is that the filtered DNS response points to a server that will
          display the block page.  If the client is using HTTPS (via a
          web browser or another application) this results in a
          certificate validation error which gives no information to the
          end-user about the reason for the DNS filtering.

       *  Enterprise networks do not assume that all the connected
          devices are managed by the IT team or Mobile Device Management
          (MDM) devices, especially in the quite common Bring Your Own
          Device (BYOD) scenario.  In addition, the local root
          certificate cannot be installed on IoT devices without a
          device management tool.

       *  An end user does not know why the connection was prevented
          and, consequently, may repeatedly try to reach the domain but
          with no success.  Frustrated, the end user may switch to an
          alternate network that offers no DNS filtering against malware
          and phishing, potentially compromising both security and
          privacy.  Furthermore, certificate errors train users to click
          through certificate errors, which is a bad security practice.
          To eliminate the need for an end user to click through
          certificate errors, an end user may manually install a local
          root certificate on a host device.  Doing so, however, is also
          a bad security practice as it creates a security vulnerability

Wing, et al.            Expires 28 November 2023                [Page 5]
Internet-Draft            Structured DNS Error                  May 2023

          that may be exploited by a MITM attack.  When a manually
          installed local root certificate expires, the user has to
          (again) manually install the new local root certificate.

   2.  The DNS response is forged to provide a NXDOMAIN response to
       cause the DNS lookup to terminate in failure.  In this case, an
       end user does not know why the domain cannot be reached and may
       repeatedly try to reach the domain but with no success.
       Frustrated, the end user may use insecure connections to reach
       the domain, potentially compromising both security and privacy.

   3.  The extended error codes Blocked and Filtered defined in
       Section 4 of [RFC8914] can be returned by a DNS server to provide
       additional information about the cause of a DNS error.

   4.  These extended error codes do not suffer from the limitations
       discussed in bullets (1) and (2), but the user still does not
       know the exact reason nor he/she is aware of the exact entity
       blocking the access to the domain.  For example, a DNS server may
       block access to a domain based on the content category such as
       "Malware" to protect the endpoint from malicious software,
       "Phishing" to prevent the user from revealing sensitive
       information to the attacker, etc.  A user needs to know the
       contact details of the IT/InfoSec team to raise a complaint.

   5.  When a DNS resolver or forwarder forwards the received EDE
       option, the EXTRA-TEXT field only conveys the source of the error
       (Section 3 of [RFC8914]) and does not provide additional textual
       information about the cause of the error.

4.  I-JSON in EXTRA-TEXT Field

   DNS servers that are compliant with this specification send I-JSON
   data in the EXTRA-TEXT field [RFC8914] using the Internet JSON
   (I-JSON) message format [RFC7493].

      Note that [RFC7493] was based on [RFC7159], but [RFC7159] was
      replaced by [RFC8259].

   This document defines the following JSON names:

   c: (contact)  The contact details of the IT/InfoSec team to report
      mis-classified DNS filtering.  This field is structured as an
      array of contact URIs (e.g., tel, sips, https).  At least one
      contact URI MUST be included.  This field is mandatory.

   j: (justification)  'UTF-8'-encoded [RFC5198] textual justification

Wing, et al.            Expires 28 November 2023                [Page 6]
Internet-Draft            Structured DNS Error                  May 2023

      for this particular DNS filtering.  The field should be treated
      only as diagnostic information for IT staff.  This field is
      mandatory.

   s: (suberror)  the suberror code for this particular DNS filtering.
      This field is optional.

   o: (organization)  'UTF-8'-encoded human-friendly name of the
      organization that filtered this particular DNS query.  This field
      is optional.

   New JSON names can be defined in the IANA registry introduced in
   Section 11.2.  Such names MUST consist only of lower-case ASCII
   characters, digits, and hyphens (that is, Unicode characters U+0061
   through 007A, U+0030 through U+0039, and U+002D).  Also, these names
   MUST be 63 characters or shorter and it is RECOMMENDED they be as
   short as possible.

   The text in the "j" and "o" names can include international
   characters.  If the text is displayed in a language not known to the
   end user, browser extensions to translate to user's native language
   can be used.

   To reduce packet overhead the generated JSON SHOULD be as short as
   possible: short domain names, concise text in the values for the "j"
   and "o" names, and minified JSON (that is, without spaces or line
   breaks between JSON elements).

   The JSON data can be parsed to display to the user, logged, or
   otherwise used to assist the end-user or IT staff with
   troubleshooting and diagnosing the cause of the DNS filtering.

5.  Protocol Operation

5.1.  Client Generating Request

   When generating a DNS query the client includes the EDE option
   (Section 2 of [RFC8914]) in the OPT pseudo-RR [RFC6891] to elicit the
   EDE option in the DNS response.  It SHOULD use an OPTION-LENGTH of 2,
   the INFO-CODE field set to "0" (Other Error), and an empty EXTRA-TEXT
   field.  This signal indicates that the client desires that the server
   responds in accordance with the present specification.

Wing, et al.            Expires 28 November 2023                [Page 7]
Internet-Draft            Structured DNS Error                  May 2023

5.2.  Server Generating Response

   When the DNS server filters its DNS response to an A or AAAA record
   query, the DNS response MAY contain an empty answer, NXDOMAIN, or
   (less ideally) forged A or AAAA response, as desired by the DNS
   server.  In addition, if the query contained the OPT pseudo-RR the
   DNS server MAY return more detail in the EXTRA-TEXT field as
   described in Section 5.3.

   Servers may decide to return small TTL values in filtered DNS
   responses (e.g., 2 seconds) to handle domain category and reputation
   updates.

   Because the DNS client signals its EDE support (Section 5.1) and
   because EDE support is signaled via a non-cached OPT resource record
   (Section 6.2.1 of [RFC6891]) the EDE-aware DNS server can tailor its
   filtered response to be most appropriate to that client's EDE
   support.  If EDE support is signaled in the query the server MUST NOT
   return the "Forged Answer" extended error code because the client can
   take advantage of EDE's more sophisticated error reporting (e.g.,
   "Filtered", "Blocked").  Continuing to send "Forged Answer" even to
   an EDE-supporting client will cause the persistence of the drawbacks
   described in Section 3.

5.3.  Client Processing Response

   On receipt of a DNS response with an EDE option from a DNS responder,
   the following actions are performed on the EXTRA-TEXT field:

   *  Verify the field contains valid JSON.  If not, the requestor MUST
      discard data in the EXTRA-TEXT field.

   *  The response MUST be received over an encrypted DNS channel.  If
      not, the requestor MUST discard data in the EXTRA-TEXT field.

   *  Servers which don't support this specification might use plain
      text in the EXTRA-TEXT field so that requestors SHOULD properly
      handle both plaintext and JSON text in the EXTRA-TEXT field.

   *  The DNS response MUST also contain an extended error code of
      "Blocked by Upstream Server", "Blocked" or "Filtered" [RFC8914],
      otherwise the EXTRA-TEXT field is discarded.

   *  If either of the mandatory JSON names "c" and "j" are missing or
      have empty values in the EXTRA-TEXT field, the entire JSON is
      discarded.

Wing, et al.            Expires 28 November 2023                [Page 8]
Internet-Draft            Structured DNS Error                  May 2023

   *  If a DNS client has enabled opportunistic privacy profile
      (Section 5 of [RFC8310]) for DoT, the DNS client will either fall
      back to an

      encrypted connection without authenticating the DNS server
      provided by the local network or fall back to clear text DNS, and
      cannot exchange encrypted DNS messages.  Both of these fallback
      mechanisms adversely impact security and privacy.  If the DNS
      client has enabled opportunistic privacy profile for DoT and the
      identity of the DNS server cannot be verified, the DNS client MUST
      ignore the "c", "j", and "o" fields but MAY process the "s" field
      and other parts of the response.

   *  Opportunistic discovery [I-D.ietf-add-ddr], where only the IP
      address is validated, the DNS client MUST ignore the "c", "j", and
      "o" fields but MAY process the "s" field and other parts of the
      response.

   *  If a DNS client has enabled strict privacy profile (Section 5 of
      [RFC8310]) for DoT, the DNS client requires an encrypted
      connection and successful authentication of the DNS server.  In
      doing so, this mitigates both passive eavesdropping and client
      redirection (at the expense of providing no DNS service if an
      encrypted, authenticated connection is not available).  If the DNS
      client has enabled strict privacy profile for DoT, the DNS client
      MAY process the EXTRA-TEXT field of the DNS response.

   *  When a forwarder receives an EDE option, whether or not (and how)
      to pass along JSON information in the EXTRA-TEXT on to their
      client is implementation dependent [RFC5625].  Implementations MAY
      choose to not forward the JSON information, or they MAY choose to
      create a new EDE option that conveys the information in the "c",
      "s", and "j" fields encoded in the JSON object.

   *  The application that triggered the DNS request may have a local
      policy to override the contact information (e.g., redirect all
      complaint calls to a single contact point).  In such a case, the
      content of the "c" attribute can be ignored.

      Note that the strict and opportunistic privacy profiles as defined
      in [RFC8310] only apply to DoT; there has been no such distinction
      made for DoH.

6.  Interoperation with RPZ Servers

   This section discusses operation with an RPZ server [RPZ] that
   indicates filtering with a NXDOMAIN response with the Recursion
   Available bit cleared (RA=0).

Wing, et al.            Expires 28 November 2023                [Page 9]
Internet-Draft            Structured DNS Error                  May 2023

   When a DNS client supports this specification it includes the EDE
   option in its DNS query.

   If the server does not support this specification and is performing
   RPZ filtering, the server ignores the EDE option in the DNS query and
   replies with NXDOMAIN and RA=0.  The DNS client can continue to
   accept such responses.

   If the server does support this specification and is performing RPZ
   filtering, the server can use the EDE option in the query to identify
   an EDE-aware client and respond appropriately (that is, by generating
   a response described in {#server-response}) as NXDOMAIN and RA=0 are
   not necessary when generating a response to such a client.

7.  New Sub-Error Codes Definition

   The document defines the following new IANA-registered Sub-Error
   codes.

7.1.  Reserved

   *  Number: 0

   *  Meaning: Reserved.  This sub-error code value MUST NOT be sent.
      If received, it has no meaning.

   *  Applicability: This code should never be used.

   *  Reference: This-Document

   *  Change Controller: IETF

7.2.  Network Operator Policy

   *  Number: 5

   *  Meaning: Network Operator Policy.  The code indicates that the
      request was filtered according to policy determined by the
      operator of the local network.

   *  Applicability: Blocked

   *  Reference: This-Document

   *  Change Controller: IETF

7.3.  DNS Operator Policy

Wing, et al.            Expires 28 November 2023               [Page 10]
Internet-Draft            Structured DNS Error                  May 2023

   *  Number: 6

   *  Meaning: DNS Operator Policy.  The code indicates that the request
      was filtered according to policy determined by the operator of the
      DNS server.

   *  Applicability: Blocked

   *  Reference: This-Document

   *  Change Controller: IETF

8.  Extended DNS Error Code TBA1 - Blocked by Upstream DNS Server

   The DNS server (e.g., a DNS forwarder) is unable to respond to the
   request because the domain is on a blocklist due to an internal
   security policy imposed by an upstream DNS server.  This error code
   is useful in deployments where a network-provided DNS forwarder is
   configured to use an external resolver that filters malicious
   domains.  Typically, when the DNS forwarder receives a Blocked (15)
   error code from the upstream DNS server, it will replace it with
   "Blocked by Upstream DNS Server" (TBA1) before forwarding the reply
   to the DNS client.

9.  Examples

   An example showing the nameserver at 'ns.example.net' that filtered a
   DNS "A" record query for 'example.org' is provided in Figure 1.

   {
     "c": [
       "tel:+358-555-1234567",
       "sips:bob@bobphone.example.com",
       "https://ticket.example.com?d=example.org&t=1650560748"
     ],
     "j": "malware present for 23 days",
     "s": 1,
     "o": "example.net Filtering Service"
   }

     Figure 1: JSON Returned in EXTRA-TEXT Field of Extended DNS Error
                                  Response

   In Figure 2 the same content is shown with minified JSON (no
   whitespace, no blank lines) with '\' line wrapping per [RFC8792].

Wing, et al.            Expires 28 November 2023               [Page 11]
Internet-Draft            Structured DNS Error                  May 2023

   =============== NOTE: '\' line wrapping per RFC 8792 ===============

   {"c":["tel:+358-555-1234567","sips:bob@bobphone.example.com","https\
   ://ticket.example.com?d=example.org&t=1650560748"],"j":"malware \
   present for 23 days","s":1,"o":"example.net Filtering Service"}

                        Figure 2: Minified Response

10.  Security Considerations

   Security considerations in Section 6 of [RFC8914] apply to this
   document.

   To minimize impact of active on-path attacks on the DNS channel, the
   client validates the response as described in Section 5.3.

   A client might choose to display the information in the "c", "j", and
   "o" fields if and only if the encrypted resolver has sufficient
   reputation, according to some local policy (e.g. user configuration,
   administrative configuration, or a built-in list of respectable
   resolvers).  This limits the ability of a malicious encrypted
   resolver to cause harm.  If the client decides not to display the all
   of the information in the EXTRA-TEXT field, it can be logged for
   diagnostics purpose and the client can only display the resolver
   hostname that blocked the domain, error description for the EDE code
   and the suberror description for the "s" field to the end-user.

   When displaying the free-form text of "j" and "o", the browser SHOULD
   NOT make any of those elements into actionable (clickable) links.

   An attacker might inject (or modify) the EDE EXTRA-TEXT field with a
   DNS proxy or DNS forwarder that is unaware of EDE.  Such a DNS proxy
   or DNS forwarder will forward that attacker-controlled EDE option.
   To prevent such an attack, clients can be configured to process EDE
   from explicitly configured DNS servers or utilize RESINFO
   [I-D.ietf-add-resolver-info].

11.  IANA Considerations

   This document requests four IANA actions as described in the
   following subsections.

      Note to the RFC Editor: Please replace RFCXXXX with the RFC number
      assigned to this document and "TBA1" with the value assigned by
      IANA.

Wing, et al.            Expires 28 November 2023               [Page 12]
Internet-Draft            Structured DNS Error                  May 2023

11.1.  Media Type Registration

   This document requests IANA to register the "application/
   json+structured-dns-error" media type in the "Media Types" registry
   [IANA-MediaTypes].  This registration follows the procedures
   specified in [RFC6838]:

      Type name: application

      Subtype name: json+structured-dns-error

      Required parameters: N/A

      Optional parameters: N/A

      Encoding considerations: as defined in Section 4 of RFCXXXX.

      Security considerations: See Section 10 of RFCXXXX.

      Interoperability considerations: N/A

      Published specification: RFCXXXX

      Applications that use this media type: Section 4 of RFCXXXX.

      Fragment identifier considerations: N/A

      Additional information: N/A

      Person & email address to contact for further information: IETF,
         iesg@ietf.org

      Intended usage: COMMON

      Restrictions on usage: none

      Author: See Authors' Addresses section.

      Change controller: IESG

      Provisional registration?  No

11.2.  New Registry for JSON Names

   This document requests IANA to create a new registry, entitled
   "EXTRA-TEXT JSON Names" under "Domain Name System (DNS) Parameters,
   Extended DNS Error Codes" registry [IANA-DNS].  The registration
   request for a new JSON name must include the following fields:

Wing, et al.            Expires 28 November 2023               [Page 13]
Internet-Draft            Structured DNS Error                  May 2023

   JSON Name:  Specifies the name of an attribute that is present in the
      JSON data enclosed in EXTRA-TEXT field.  The name must follow the
      guidelines in Section 4.

   Short description:  Includes a short description of the requested
      JSON name.

   Mandatory (Y/N?):  Indicates whether this attribute is mandatory or
      optional.

   Specification:  Provides a pointer to the reference document that
      specifies the attribute.

   The registry is initially populated with the following values:

Wing, et al.            Expires 28 November 2023               [Page 14]
Internet-Draft            Structured DNS Error                  May 2023

   +====+===============+==================+===========+===============+
   |JSON| Full JSON     | Description      | Mandatory | Specification |
   |Name| Name          |                  |           |               |
   +====+===============+==================+===========+===============+
   | c  | contact       | The contact      | Y         |  Section 4 of |
   |    |               | details of the   |           |    RFCXXXX    |
   |    |               | IT/InfoSec team  |           |               |
   |    |               | to report mis-   |           |               |
   |    |               | classified DNS   |           |               |
   |    |               | filtering        |           |               |
   +----+---------------+------------------+-----------+---------------+
   | j  | justification | UTF-8-encoded    | Y         |  Section 4 of |
   |    |               | [RFC5198]        |           |    RFCXXXX    |
   |    |               | textual          |           |               |
   |    |               | justification    |           |               |
   |    |               | for a            |           |               |
   |    |               | particular DNS   |           |               |
   |    |               | filtering        |           |               |
   +----+---------------+------------------+-----------+---------------+
   | s  | suberror      | the suberror     | N         |  Section 4 of |
   |    |               | code for this    |           |    RFCXXXX    |
   |    |               | particular DNS   |           |               |
   |    |               | filtering        |           |               |
   +----+---------------+------------------+-----------+---------------+
   | o  | organization  | UTF-8-encoded    | N         |  Section 4 of |
   |    |               | human-friendly   |           |    RFCXXXX    |
   |    |               | name of the      |           |               |
   |    |               | organization     |           |               |
   |    |               | that filtered    |           |               |
   |    |               | this particular  |           |               |
   |    |               | DNS query        |           |               |
   +----+---------------+------------------+-----------+---------------+

                    Table 1: Initial JSON Names Registry

   New JSON names are registered via IETF Review (Section 4.8 of
   [RFC8126]).

11.3.  New Registry for DNS SubError Codes

   This document requests IANA to create a new registry, entitled
   "SubError Codes" under "Domain Name System (DNS) Parameters, Extended
   DNS Error Codes" registry [IANA-DNS].  The registration request for a
   new suberror codes MUST include the following fields:

   *  Number: Is the wire format suberror code (range 0-255).

   *  Meaning: Provides a short description of the sub-error.

Wing, et al.            Expires 28 November 2023               [Page 15]
Internet-Draft            Structured DNS Error                  May 2023

   *  Applicability: Indicates which RFC8914 error codes apply to this
      sub-error code.

   *  Reference: Provides a pointer to an IETF-approved specification
      that registered the code and/or an authoritative specification
      that describes the meaning of this code.

   *  Change Controller: Indicates the person or entity, with contact
      information if appropriate.

   The SubError Code registry is initially be populated with the
   following suberror codes:

Wing, et al.            Expires 28 November 2023               [Page 16]
Internet-Draft            Structured DNS Error                  May 2023

   +========+==========+===================+=============+============+
   | Number | Meaning  | RFC8914 error     | Reference   |   Change   |
   |        |          | code              |             | Controller |
   |        |          | applicability     |             |            |
   +========+==========+===================+=============+============+
   |   0    | Reserved | Not used          | Section 7.1 |    IETF    |
   |        |          |                   | of this     |            |
   |        |          |                   | document    |            |
   +--------+----------+-------------------+-------------+------------+
   |   1    | Malware  | "Blocked",        | Section 5.5 |    IETF    |
   |        |          | "Blocked by       | of          |            |
   |        |          | Upstream Server", | [RFC5901]   |            |
   |        |          | "Filtered"        |             |            |
   +--------+----------+-------------------+-------------+------------+
   |   2    | Phishing | "Blocked",        | Section 5.5 |    IETF    |
   |        |          | "Blocked by       | of          |            |
   |        |          | Upstream Server", | [RFC5901]   |            |
   |        |          | "Filtered"        |             |            |
   +--------+----------+-------------------+-------------+------------+
   |   3    | Spam     | "Blocked",        | Page 289 of |    IETF    |
   |        |          | "Blocked by       | [RFC4949]   |            |
   |        |          | Upstream Server", |             |            |
   |        |          | "Filtered"        |             |            |
   +--------+----------+-------------------+-------------+------------+
   |   4    | Spyware  | "Blocked",        | Page 291 of |    IETF    |
   |        |          | "Blocked by       | [RFC4949]   |            |
   |        |          | Upstream Server", |             |            |
   |        |          | "Filtered"        |             |            |
   +--------+----------+-------------------+-------------+------------+
   |   5    | Network  | "Blocked"         | Section 7.2 |    IETF    |
   |        | operator |                   | of this     |            |
   |        | policy   |                   | document    |            |
   +--------+----------+-------------------+-------------+------------+
   |   6    | DNS      | "Blocked"         | Section 7.3 |    IETF    |
   |        | operator |                   | of this     |            |
   |        | policy   |                   | document    |            |
   +--------+----------+-------------------+-------------+------------+

                 Table 2: Initial SubError Code Registry

   New SubError Codes are registered via IETF Review (Section 4.8 of
   [RFC8126]).

11.4.  New Extended DNS Error Code

   IANA is requested to assign the following Extended DNS Error code
   from the "Domain Name System (DNS) Parameters, Extended DNS Error
   Codes" registry [IANA-DNS]:

Wing, et al.            Expires 28 November 2023               [Page 17]
Internet-Draft            Structured DNS Error                  May 2023

          +===========+============================+===========+
          | INFO-CODE | Purose                     | Reference |
          +===========+============================+===========+
          |    TBA1   | Blocked by Upstream Server |  RFCXXXX  |
          +-----------+----------------------------+-----------+

                       Table 3: New DNS Error Code

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/rfc/rfc2119>.

   [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
              FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
              <https://www.rfc-editor.org/rfc/rfc4949>.

   [RFC5198]  Klensin, J. and M. Padlipsky, "Unicode Format for Network
              Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
              <https://www.rfc-editor.org/rfc/rfc5198>.

   [RFC5901]  Cain, P. and D. Jevans, "Extensions to the IODEF-Document
              Class for Reporting Phishing", RFC 5901,
              DOI 10.17487/RFC5901, July 2010,
              <https://www.rfc-editor.org/rfc/rfc5901>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <https://www.rfc-editor.org/rfc/rfc6838>.

   [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/rfc/rfc6891>.

   [RFC7159]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
              2014, <https://www.rfc-editor.org/rfc/rfc7159>.

   [RFC7493]  Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
              DOI 10.17487/RFC7493, March 2015,
              <https://www.rfc-editor.org/rfc/rfc7493>.

Wing, et al.            Expires 28 November 2023               [Page 18]
Internet-Draft            Structured DNS Error                  May 2023

   [RFC8126]  Cotton, M., Leiba, B., and T. Narten, "Guidelines for
              Writing an IANA Considerations Section in RFCs", BCP 26,
              RFC 8126, DOI 10.17487/RFC8126, June 2017,
              <https://www.rfc-editor.org/rfc/rfc8126>.

   [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/rfc/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/rfc/rfc8310>.

   [RFC8914]  Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
              Lawrence, "Extended DNS Errors", RFC 8914,
              DOI 10.17487/RFC8914, October 2020,
              <https://www.rfc-editor.org/rfc/rfc8914>.

12.2.  Informative References

   [I-D.ietf-add-ddr]
              Pauly, T., Kinnear, E., Wood, C. A., McManus, P., and T.
              Jensen, "Discovery of Designated Resolvers", Work in
              Progress, Internet-Draft, draft-ietf-add-ddr-10, 5 August
              2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
              add-ddr-10>.

   [I-D.ietf-add-resolver-info]
              Reddy.K, T. and M. Boucadair, "DNS Resolver Information",
              Work in Progress, Internet-Draft, draft-ietf-add-resolver-
              info-02, 26 May 2023,
              <https://datatracker.ietf.org/doc/html/draft-ietf-add-
              resolver-info-02>.

   [IANA-DNS] IANA, "Domain Name System (DNS) Parameters, Extended DNS
              Error Codes", <https://www.iana.org/assignments/dns-
              parameters/dns-parameters.xhtml#extended-dns-error-codes>.

   [IANA-MediaTypes]
              IANA, "Media Types",
              <https://www.iana.org/assignments/media-types>.

   [RFC5625]  Bellis, R., "DNS Proxy Implementation Guidelines",
              BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
              <https://www.rfc-editor.org/rfc/rfc5625>.

Wing, et al.            Expires 28 November 2023               [Page 19]
Internet-Draft            Structured DNS Error                  May 2023

   [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/rfc/rfc7858>.

   [RFC8259]  Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
              Interchange Format", STD 90, RFC 8259,
              DOI 10.17487/RFC8259, December 2017,
              <https://www.rfc-editor.org/rfc/rfc8259>.

   [RFC8484]  Hoffman, P. and P. McManus, "DNS Queries over HTTPS
              (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
              <https://www.rfc-editor.org/rfc/rfc8484>.

   [RFC8499]  Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
              Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
              January 2019, <https://www.rfc-editor.org/rfc/rfc8499>.

   [RFC8792]  Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
              "Handling Long Lines in Content of Internet-Drafts and
              RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
              <https://www.rfc-editor.org/rfc/rfc8792>.

   [RFC9250]  Huitema, C., Dickinson, S., and A. Mankin, "DNS over
              Dedicated QUIC Connections", RFC 9250,
              DOI 10.17487/RFC9250, May 2022,
              <https://www.rfc-editor.org/rfc/rfc9250>.

   [RPZ]      "Response Policy Zone", <https://dnsrpz.info>.

Acknowledgements

   Thanks to Vittorio Bertola, Wes Hardaker, Ben Schwartz, Erid Orth,
   Viktor Dukhovni, Warren Kumari, Paul Wouters, John Levine, and Bob
   Harold for the comments.

   Thanks to Ralf Weber and Gianpaolo Scalone for sharing details about
   their implementation.

Authors' Addresses

   Dan Wing
   Citrix Systems, Inc.
   United States of America
   Email: danwing@gmail.com

Wing, et al.            Expires 28 November 2023               [Page 20]
Internet-Draft            Structured DNS Error                  May 2023

   Tirumaleswar Reddy
   Nokia
   Bangalore
   Karnataka
   India
   Email: kondtir@gmail.com

   Neil Cook
   Open-Xchange
   United Kingdom
   Email: neil.cook@noware.co.uk

   Mohamed Boucadair
   Orange
   Rennes
   35000
   France
   Email: mohamed.boucadair@orange.com

Wing, et al.            Expires 28 November 2023               [Page 21]