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Versions: (draft-wkumari-dnsop-extended-error) 00 01 02

Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Standards Track                                 E. Hunt
Expires: March 25, 2019                                              ISC
                                                               R. Arends
                                                                   ICANN
                                                             W. Hardaker
                                                                 USC/ISI
                                                             D. Lawrence
                                                            Oracle + Dyn
                                                      September 21, 2018


                          Extended DNS Errors
                   draft-ietf-dnsop-extended-error-02

Abstract

   This document defines an extensible method to return additional
   information about the cause of DNS errors.  The primary use case is
   to extend SERVFAIL to provide additional information about the cause
   of DNS and DNSSEC failures.

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 March 25, 2019.

Copyright Notice

   Copyright (c) 2018 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



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   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.

Table of Contents

   1.  Introduction and background . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  Extended Error EDNS0 option format  . . . . . . . . . . . . .   3
   3.  Use of the Extended DNS Error option  . . . . . . . . . . . .   5
   4.  Defined Extended DNS Errors . . . . . . . . . . . . . . . . .   5
     4.1.  SERVFAIL(2) extended information codes  . . . . . . . . .   5
       4.1.1.  Extended DNS Error Code 1 - DNSSEC Bogus  . . . . . .   6
       4.1.2.  Extended DNS Error Code 2 - DNSSEC Indeterminate  . .   6
       4.1.3.  Extended DNS Error Code 3 - Signature Expired . . . .   6
       4.1.4.  Extended DNS Error Code 4 - Signature Not Yet Valid .   6
       4.1.5.  Extended DNS Error Code 5 - Unsupported
               DNSKEY Algorithm  . . . . . . . . . . . . . . . . . .   6
       4.1.6.  Extended DNS Error Code 6 - Unsupported
               DS Algorithm  . . . . . . . . . . . . . . . . . . . .   6
       4.1.7.  Extended DNS Error Code 7 - DNSKEY missing  . . . . .   6
       4.1.8.  Extended DNS Error Code 8 - RRSIGs missing  . . . . .   6
       4.1.9.  Extended DNS Error Code 9 - No Zone Key Bit Set . . .   6
     4.2.  REFUSED(5) extended information codes . . . . . . . . . .   7
       4.2.1.  Extended DNS Error Code 1 - Lame  . . . . . . . . . .   7
       4.2.2.  Extended DNS Error Code 2 - Prohibited  . . . . . . .   7
     4.3.  NXDOMAIN(3) extended information codes  . . . . . . . . .   7
       4.3.1.  Extended DNS Error Code 1 - Blocked . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
     5.1.  new Extended Error Code EDNS Option . . . . . . . . . . .   7
     5.2.  new Extended Error Code EDNS Option . . . . . . . . . . .   7
   6.  Open questions  . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   9
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Appendix A.  Changes / Author Notes.  . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction and background

   There are many reasons that a DNS query may fail, some of them
   transient, some permanent; some can be resolved by querying another
   server, some are likely best handled by stopping resolution.



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   Unfortunately, the error signals that a DNS server can return are
   very limited, and are not very expressive.  This means that
   applications and resolvers often have to "guess" at what the issue is
   - e.g the answer was marked REFUSED because of a lame delegation, or
   because of a lame delegation or because the nameserver is still
   starting up and loading zones?  Is a SERVFAIL a DNSSEC validation
   issue, or is the nameserver experiencing a bad hair day?

   A good example of issues that would benefit by additional error
   information is an error caused by a DNSSEC validation issue.  When a
   stub resolver queries a DNSSEC bogus name (using a validating
   resolver), the stub resolver receives only a SERVFAIL in response.
   Unfortunately, SERVFAIL is used to signal many sorts of DNS errors,
   and so the stub resolver simply asks the next configured DNS
   resolver.  The result of trying the next resolver is one of two
   outcomes: either the next resolver also validates, a SERVFAIL is
   returned again, and the user gets an (largely) incomprehensible error
   message; or the next resolver is not a validating resolver, and the
   user is returned a potentially harmful result.

   This document specifies a mechanism to extend (or annotate) DNS
   errors to provide additional information about the cause of the
   error.  This information can be used by the resolver to make a
   decision regarding whether or not to retry, or by technical users
   attempting to debug issues.

   Here is a reference to an "external" (non-RFC / draft) thing:
   ([IANA.AS_Numbers]).  And this is a link to an
   ID:[I-D.ietf-sidr-iana-objects].

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

2.  Extended Error EDNS0 option format

   This draft uses an EDNS0 ([RFC2671]) option to include extended error
   (ExtError) information in DNS messages.  The option is structured as
   follows:










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                                                1   1   1   1   1   1
        0   1   2   3   4   5   6   7   8   9   0   1   2   3   4   5
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   0: |                            OPTION-CODE                        |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   2: |                           OPTION-LENGTH                       |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   4: | R |                          RESERVED                         |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   6: |                           RESPONSE-CODE                       |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   8: |                             INFO-CODE                         |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   A: |                             EXTRA-TEXT                        |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   o  OPTION-CODE, 2 octets (defined in [RFC6891]), for ExtError is TBD.

   o  OPTION-LENGTH, 2 octets ((defined in [RFC6891]) contains the
      length of the payload (everything after OPTION-LENGTH) in octets
      and should be 4.

   o  RESERVED, 2 octets; the first bit (R) indicates a flag defined in
      this specification.  The remaining bits are reserved for future
      use, potentially as additional flags.

   o  RESPONSE-CODE, 2 octets: this SHOULD be a copy of the RCODE from
      the primary DNS packet.  When including multiple extended error
      EDNS0 records in a response in order to provide additional error
      information, the RESPONSE-CODE MAY be a different RCODE.

   o  INFO-CODE, 2 octets.

   o  A variable length EXTRA-TEXT field holding additional textual
      information.  It may be zero length when no additional textual
      information is included.

   Currently the only defined flag is the R flag.

   R - Retry  The R (or Retry) flag provides a hint to the receiver that
      it should retry the query, probably by querying another server.
      If the R bit is set (1), the sender believes that retrying the
      query may provide a successful answer next time; if the R bit is
      clear (0), the sender believes that it should not ask another
      server.






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   The remaining bits in the RESERVED field are reserved for future use
   and MUST be set to 0 by the sender and SHOULD be ignored by the
   receiver.

   INFO-CODE: A code point that, when combined with the RCODE from the
   DNS packet, serve as a joint-index into the IANA "Extended DNS
   Errors" registry.

3.  Use of the Extended DNS Error option

   The Extended DNS Error (EDE) is an EDNS option.  It can be included
   in any error response (SERVFAIL, NXDOMAIN, REFUSED, etc) to a query
   that includes an EDNS option.  This document includes a set of
   initial codepoints (and requests to the IANA to add them to the
   registry), but is extensible via the IANA registry to allow
   additional error and information codes to be defined in the future.

   The R (Retry) flag provides a hint (or suggestion) as to what the
   receiver may want to do with this annotated error.  The mechanism is
   specifically designed to be extensible, and so implementations may
   receive EDE codes that it does not understand.  The R flag allows
   implementations to make a decision as to what to do if it receives a
   response with an unknown code - retry or drop the query.  Note that
   this flag is only a suggestion or hint.  Receivers can choose to
   ignore this hint.

   The EXTRA-INFO textual field may be zero-length, or may hold
   additional information useful to network operators.

4.  Defined Extended DNS Errors

   This document defines some initial EDE codes.  The mechanism is
   intended to be extensible, and additional codepoints will be
   registered in the "Extended DNS Errors" registry.  This document
   provides suggestions for the R flag, but the originating server may
   ignore these recommendations if it knows better.

   The RESPONSE-CODE and the INFO-CODE from the EDE EDNS option is used
   to serve as a double index into the "Extended DNS Error codes" IANA
   registry, the initial values for which are defined in the following
   sub-sections.

4.1.  SERVFAIL(2) extended information codes








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4.1.1.  Extended DNS Error Code 1 - DNSSEC Bogus

   The resolver attempted to perform DNSSEC validation, but validation
   ended in the Bogus state.  The R flag should not be set.

4.1.2.  Extended DNS Error Code 2 - DNSSEC Indeterminate

   The resolver attempted to perform DNSSEC validation, but validation
   ended in the Indeterminate state.  The R flag should not be set.

4.1.3.  Extended DNS Error Code 3 - Signature Expired

   The resolver attempted to perform DNSSEC validation, but the
   signature was expired.  The R flag should not be set.

4.1.4.  Extended DNS Error Code 4 - Signature Not Yet Valid

   The resolver attempted to perform DNSSEC validation, but the
   signatures received were not yet valid.  The R flag should not be
   set.

4.1.5.  Extended DNS Error Code 5 - Unsupported DNSKEY Algorithm

   The resolver attempted to perform DNSSEC validation, but a DNSKEY
   RRSET contained only unknown algorithms.  The R flag should not be
   set.

4.1.6.  Extended DNS Error Code 6 - Unsupported DS Algorithm

   The resolver attempted to perform DNSSEC validation, but a DS RRSET
   contained only unknown algorithms.  The R flag should not be set.

4.1.7.  Extended DNS Error Code 7 - DNSKEY missing

   A DS record existed at a parent, but no DNSKEY record could be found
   for the child.  The R flag should not be set.

4.1.8.  Extended DNS Error Code 8 - RRSIGs missing

   The resolver attempted to perform DNSSEC validation, but no RRSIGs
   could be found for at least one RRset where RRSIGs were expected.

4.1.9.  Extended DNS Error Code 9 - No Zone Key Bit Set

   The resolver attempted to perform DNSSEC validation, but no Zone Key
   Bit was set in a DNSKEY.





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4.2.  REFUSED(5) extended information codes

4.2.1.  Extended DNS Error Code 1 - Lame

   An authoritative resolver that receives a query (with the RD bit
   clear) for a domain for which it is not authoritative SHOULD include
   this EDE code in the REFUSED response.  Implementations should set
   the R flag in this case (another nameserver might not be lame).

4.2.2.  Extended DNS Error Code 2 - Prohibited

   An authoritative or recursive resolver that receives a query from an
   "unauthorized" client can annotate its REFUSED message with this
   code.  Examples of "unauthorized" clients are recursive queries from
   IP addresses outside the network, blacklisted IP addresses, local
   policy, etc.

   Implementations SHOULD allow operators to define what to set the R
   flag to in this case.

4.3.  NXDOMAIN(3) extended information codes

4.3.1.  Extended DNS Error Code 1 - Blocked

   The resolver attempted to perfom a DNS query but the domain is
   blacklisted due to a security policy.  The R flag should not be set.

5.  IANA Considerations

   [This section under construction, beware. ]

5.1.  new Extended Error Code EDNS Option

   This document defines a new EDNS(0) option, entitled "Extended DNS
   Error", assigned a value of TBD1 from the "DNS EDNS0 Option Codes
   (OPT)" registry [to be removed upon publication:
   [http://www.iana.org/assignments/dns-parameters/dns-
   parameters.xhtml#dns-parameters-11]

   Value  Name                 Status    Reference
   -----  ----------------     ------    ------------------
    TBD   Extended DNS Error    TBD       [ This document ]

5.2.  new Extended Error Code EDNS Option

   This document defines a new double-index IANA registry table, where
   the first index value is the RCODE value and the second index value
   is the INFO-CODE from the Extended DNS Error EDNS option defined in



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   this document.  The IANA is requested to create and maintain this
   "Extended DNS Error codes" registry.  The codepoint space for each
   RCODE index is to be broken into 3 ranges:

   o  1 - 16384: Specification required.

   o  16385 - 65000: First Come First Served

   o  65000 - 65534: Experimental / Private use

   The codepoints 0, 65535 are reserved.

   A starting table, based on the contents of this document, is as
   follows:



| RCODE       | EDE-INFO-CODE           | Meaning                                     | Ref                                      |
|-------------+-------------------------+---------------------------------------------+------------------------------------------|
| SERVFAIL(2) | DNSSEC_BOGUS(1)         | DNSSEC Validation resulted in Bogus         | section <xref target="errbogus" />         |
| SERVFAIL(2) | DNSSEC_INDETERMINATE(2) | DNSSEC Validation resulted in Indeterminate | section <xref target="errindeterminate" /> |

[incomplete]


6.  Open questions

   1  Can this be included in *any* response or only responses to
      requests that included an EDNS option?  Resolvers are supposed to
      ignore additional.  EDNS capable ones are supposed to simply
      ignore unknown options.  I know the spec says you can only include
      EDNS0 in a response if in a request -- it is time to reevaluate
      this?

7.  Security Considerations

   DNSSEC is being deployed - unfortunately a significant number of
   clients (~11% according to [GeoffValidation]), when receiving a
   SERVFAIL from a validating resolver because of a DNSSEC validaion
   issue simply ask the next (non-validating) resolver in their list,
   and don't get any of the protections which DNSSEC should provide.
   This is very similar to a kid asking his mother if he can have
   another cookie.  When the mother says "No, it will ruin your
   dinner!", going off and asking his (more permissive) father and
   getting a "Yes, sure, cookie!".






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8.  Acknowledgements

   The authors wish to thank Geoff Huston and Bob Harold, Carlos M.
   Martinez, Peter DeVries, George Michelson, Mark Andrews, Ondrej Sury,
   Edward Lewis, Paul Vixie, Shane Kerr, Loganaden Velvindron.  They
   also vaguely remember discussing this with a number of people over
   the years, but have forgotten who all they were -- if you were one of
   them, and are not listed, please let us know and we'll acknowledge
   you.

   I also want to thank the band "Infected Mushroom" for providing a
   good background soundtrack (and to see if I can get away with this!)
   Another author would like to thank the band "Mushroom Infectors".
   This was funny at the time we wrote it, but I cannot remember why...

   We would like to especially thank Peter van Dijk, who sent GitHub
   pull requests.

9.  References

9.1.  Normative References

   [IANA.AS_Numbers]
              IANA, "Autonomous System (AS) Numbers",
              <http://www.iana.org/assignments/as-numbers>.

   [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/info/rfc2119>.

9.2.  Informative References

   [GeoffValidation]
              IANA, "A quick review of DNSSEC Validation in today's
              Internet", June 2016, <http://www.potaroo.net/
              presentations/2016-06-27-dnssec.pdf>.

   [I-D.ietf-sidr-iana-objects]
              Manderson, T., Vegoda, L., and S. Kent, "RPKI Objects
              issued by IANA", draft-ietf-sidr-iana-objects-03 (work in
              progress), May 2011.

Appendix A.  Changes / Author Notes.

   [RFC Editor: Please remove this section before publication ]

   From -00 to -01:



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   o  Address comments from IETF meeting.

   o  document copying the response code

   o  mention zero length fields are ok

   o  clarify lookup procedure

   o  mention that table isn't done

   From -03 to -IETF 00:

   o  Renamed to draft-ietf-dnsop-extended-error

   From -02 to -03:

   o  Added David Lawrence -- I somehow missed that in last version.

   From -00 to -01;

   o  Fixed up some of the text, minor clarifications.

Authors' Addresses

   Warren Kumari
   Google
   1600 Amphitheatre Parkway
   Mountain View, CA  94043
   US

   Email: warren@kumari.net


   Evan Hunt
   ISC
   950 Charter St
   Redwood City, CA  94063
   US

   Email: each@isc.org


   Roy Arends
   ICANN

   Email: roy.arends@icann.org





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   Wes Hardaker
   USC/ISI
   P.O. Box 382
   Davis, CA  95617
   US

   Email: ietf@hardakers.net


   David C Lawrence
   Oracle + Dyn
   150 Dow St
   Manchester, NH  03101
   US

   Email: tale@dd.org



































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