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Versions: (draft-wkumari-dnsop-extended-error) 00 01 02 03 04 05 06 07 08 09 10 11 12

Network Working Group                                          W. Kumari
Internet-Draft                                                    Google
Intended status: Standards Track                                 E. Hunt
Expires: March 13, 2020                                              ISC
                                                               R. Arends
                                                                   ICANN
                                                             W. Hardaker
                                                                 USC/ISI
                                                             D. Lawrence
                                                            Oracle + Dyn
                                                      September 10, 2019


                          Extended DNS Errors
                   draft-ietf-dnsop-extended-error-09

Abstract

   This document defines an extensible method to return additional
   information about the cause of DNS errors.  Though created primarily
   to extend SERVFAIL to provide additional information about the cause
   of DNS and DNSSEC failures, the Extended DNS Errors option defined in
   this document allows all response types to contain extended error
   information.

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."

   This Internet-Draft will expire on March 13, 2020.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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.

Table of Contents

   1.  Introduction and background . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   4
   2.  Extended Error EDNS0 option format  . . . . . . . . . . . . .   4
   3.  Defined Extended DNS Errors . . . . . . . . . . . . . . . . .   5
     3.1.  Extended DNS Error Code 0 - Other . . . . . . . . . . . .   5
     3.2.  Extended DNS Error Code 1 -
           Unsupported DNSKEY Algorithm  . . . . . . . . . . . . . .   5
     3.3.  Extended DNS Error Code 2 - Unsupported
           DS Algorithm  . . . . . . . . . . . . . . . . . . . . . .   5
     3.4.  Extended DNS Error Code 3 - Stale Answer  . . . . . . . .   5
     3.5.  Extended DNS Error Code 4 - Forged Answer . . . . . . . .   5
     3.6.  Extended DNS Error Code 5 - DNSSEC Indeterminate  . . . .   5
     3.7.  Extended DNS Error Code 6 - DNSSEC Bogus  . . . . . . . .   6
     3.8.  Extended DNS Error Code 7 - Signature Expired . . . . . .   6
     3.9.  Extended DNS Error Code 8 - Signature Not Yet Valid . . .   6
     3.10. Extended DNS Error Code 9 - DNSKEY Missing  . . . . . . .   6
     3.11. Extended DNS Error Code 10 - RRSIGs Missing . . . . . . .   6
     3.12. Extended DNS Error Code 11 - No Zone Key Bit Set  . . . .   6
     3.13. Extended DNS Error Code 12 - NSEC Missing . . . . . . . .   6
     3.14. Extended DNS Error Code 13 - Cached Error . . . . . . . .   6
     3.15. Extended DNS Error Code 14 - Not Ready  . . . . . . . . .   6
     3.16. Extended DNS Error Code 15 - Blocked  . . . . . . . . . .   7
     3.17. Extended DNS Error Code 16 - Censored . . . . . . . . . .   7
     3.18. Extended DNS Error Code 17 - Prohibited . . . . . . . . .   7
     3.19. Extended DNS Error Code 18 - Filtered . . . . . . . . . .   7
     3.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer  . . .   7
     3.21. Extended DNS Error Code 20 - Lame . . . . . . . . . . . .   7
     3.22. Extended DNS Error Code 21 - Deprecated . . . . . . . . .   8
     3.23. Extended DNS Error Code 22 - No Reachable Authority . . .   8
     3.24. Extended DNS Error Code 23 - Network Error  . . . . . . .   8
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
     4.1.  A New Extended DNS Error Code EDNS Option . . . . . . . .   8
     4.2.  New Registry Table for Extended DNS Error Codes . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  11
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11



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     7.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     7.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

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.
   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. was the answer marked REFUSED 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
   some other failure?

   A good example of issues that would benefit by additional error
   information are errors caused by DNSSEC validation issues.  When a
   stub resolver queries a name which is DNSSEC bogus (using a
   validating resolver), the stub resolver receives only a SERVFAIL in
   response.  Unfortunately, the SERVFAIL Response Code (RCODE) is used
   to signal many sorts of DNS errors, and so the stub resolvers only
   option is to ask the next configured DNS resolver.  The result of
   trying the next resolver is one of two outcomes: either the next
   resolver also validates, and a SERVFAIL is returned again or the next
   resolver is not a validating resolver, and the user is returned a
   potentially harmful result.  With an Extended DNS Error (EDE) option
   enclosed in the response message, the resolver is able to return a
   more descriptive reason as to why any failures happened, or add
   additional context to a message containing a NOERROR RCODE.

   This document specifies a mechanism to extend DNS errors to provide
   additional information about the cause of an error.  These extended
   DNS error codes described in this document and can be used by any
   system that sends DNS queries and receives a response containing an
   EDE option.. Different codes are useful in different circumstances,
   and thus different systems (stub resolvers, recursive resolvers, and
   authoritative resolvers) might receive and use them.

   This document does not allow or prohibit any particular extended
   error codes and information be matched with any particular RCODEs.
   Some combinations of extended error codes and RCODEs may seem
   nonsensical (such as resolver-specific extended error codes in
   responses from authoritative servers), so systems interpreting the
   extended error codes MUST NOT assume that a combination will make
   sense.  Receivers MUST be able to accept EDE codes and EXTRA-TEXT in
   all messages, including even those with a NOERROR RCODE.



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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 DNS
   Error (EDE) information in DNS messages.  The option is structured as
   follows:

                                                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: | INFO-CODE                                                     |
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
   6: / EXTRA-TEXT ...                                                /
      +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+

   Field definition details:

   o  OPTION-CODE, 2 octets (defined in [RFC6891]]), for EDE is TBD.
      [RFC Editor: change TBD to the proper code once assigned by IANA.]
   o  OPTION-LENGTH, 2 octets ((defined in [RFC6891]]) contains the
      length of the payload (everything after OPTION-LENGTH) in octets
      and should be 4 plus the length of the EXTRA-TEXT section (which
      may be a zero-length string).
   o  INFO-CODE, 16-bits, which is the principal contribution of this
      document.  This 16-bit value, encoded in network (MSB) byte order,
      provides the additional context for the RESPONSE-CODE of the DNS
      message.  The INFO-CODE serves as an index to the "Extended DNS
      Errors" registry Section 4.1.
   o  EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may
      hold additional textual information.  Note: EXTRA-TEXT may be zero
      octets in length, indicating there is no EXTRA-TEXT included.
      Care should be take not to leak private information that an
      observer would not otherwise have access to, such as account
      numbers.

   The Extended DNS Error (EDE) option can be included in any response
   (SERVFAIL, NXDOMAIN, REFUSED, and even NOERROR, etc) to a query that
   includes OPT Pseudo-RR [RFC6891].  This document includes a set of
   initial codepoints (and requests to the IANA to add them to the



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   registry), but is extensible via the IANA registry to allow
   additional error and information codes to be defined in the future.

3.  Defined Extended DNS Errors

   This document defines some initial EDE codes.  The mechanism is
   intended to be extensible, and additional code-points can be
   registered in the "Extended DNS Errors" registry Section 4.1.  The
   INFO-CODE from the EDE EDNS option is used to serve as an index into
   the "Extended DNS Error" IANA registry, the initial values for which
   are defined in the following sub-sections.

3.1.  Extended DNS Error Code 0 - Other

   The error in question falls into a category that does not match known
   extended error codes.  Implementations SHOULD include a EXTRA-TEXT
   value to augment this error code with additional information.

3.2.  Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm

   The resolver attempted to perform DNSSEC validation, but a DNSKEY
   RRSET contained only unknown algorithms.

3.3.  Extended DNS Error Code 2 - Unsupported DS Algorithm

   The resolver attempted to perform DNSSEC validation, but a DS RRSET
   contained only unknown algorithms.

3.4.  Extended DNS Error Code 3 - Stale Answer

   The resolver was unable to resolve answer within its time limits and
   decided to answer with previously cached data instead of answering
   with an error.  This is typically caused by problems communicating
   with an authoritative serever, possibly as result of a DoS attack
   against another network.

3.5.  Extended DNS Error Code 4 - Forged Answer

   For policy reasons (legal obligation, or malware filtering, for
   instance), an answer was forged.

3.6.  Extended DNS Error Code 5 - DNSSEC Indeterminate

   The resolver attempted to perform DNSSEC validation, but validation
   ended in the Indeterminate state.






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3.7.  Extended DNS Error Code 6 - DNSSEC Bogus

   The resolver attempted to perform DNSSEC validation, but validation
   ended in the Bogus state.

3.8.  Extended DNS Error Code 7 - Signature Expired

   The resolver attempted to perform DNSSEC validation, but a signature
   in the validation chain was expired.

3.9.  Extended DNS Error Code 8 - Signature Not Yet Valid

   The resolver attempted to perform DNSSEC validation, but the
   signatures received were not yet valid.

3.10.  Extended DNS Error Code 9 - DNSKEY Missing

   A DS record existed at a parent, but no supported matching DNSKEY
   record could be found for the child.

3.11.  Extended DNS Error Code 10 - RRSIGs Missing

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

3.12.  Extended DNS Error Code 11 - No Zone Key Bit Set

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

3.13.  Extended DNS Error Code 12 - NSEC Missing

   The resolver attempted to perform DNSSEC validation, but the
   requested data was missing and a covering NSEC or NSEC3 was not
   provided.

3.14.  Extended DNS Error Code 13 - Cached Error

   The resolver has cached SERVFAIL for this query.

3.15.  Extended DNS Error Code 14 - Not Ready

   The server is unable to answer the query as it is not fully
   functional (yet).







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3.16.  Extended DNS Error Code 15 - Blocked

   The resolver attempted to perfom a DNS query but the domain is
   blacklisted due to a security policy implemented on the server being
   directly talked to.

3.17.  Extended DNS Error Code 16 - Censored

   The resolver attempted to perfom a DNS query but the domain was
   blacklisted by a security policy imposed upon the server being talked
   to.  Note that how the imposed policy is applied is irrelevant (in-
   band DNS filtering, court order, etc).

3.18.  Extended DNS Error Code 17 - 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.

3.19.  Extended DNS Error Code 18 - Filtered

   An authoritative or recursive resolver that receives a query from a
   client that had requested certain domains be filtered can annotate
   its REFUSED message with this code.  Functionally, this amounts to
   "you requested that we filter domains like this one."

3.20.  Extended DNS Error Code 19 - Stale NXDOMAIN Answer

   The resolver was unable to resolve an answer within its configured
   time limits and decided to answer with a previously cached NXDOMAIN
   answer instead of answering with an error.  This is typically caused
   by problems communicating with an authoritative serever, possibly as
   result of a DoS attack against another network.

3.21.  Extended DNS Error Code 20 - Lame

   An authoritative server 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 SERVFAIL response.  A resolver that receives a query
   (with the RD bit clear) SHOULD include this EDE code in the REFUSED
   response.








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3.22.  Extended DNS Error Code 21 - Deprecated

   The requested operation or query is not supported as its use has been
   deprecated.

3.23.  Extended DNS Error Code 22 - No Reachable Authority

   The resolver could not reach any of the authoritative name servers
   (or they refused to reply).

3.24.  Extended DNS Error Code 23 - Network Error

   An unrecoverable error occurred while communicating with another
   server.

4.  IANA Considerations

4.1.  A New Extended DNS 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 ]

4.2.  New Registry Table for Extended DNS Error Codes

   This document defines a new IANA registry table, where the index
   value is the INFO-CODE from the "Extended DNS Error" EDNS option
   defined in this document.  The IANA is requested to create and
   maintain this "Extended DNS Error" codes registry.  The code-point
   space for the INFO-CODE index is to be broken into 3 ranges:

   o  0 - 32767: Expert Review [RFC2434].
   o  32768 - 49151: First come, first served.
   o  49152 - 65535: Experimental / Private use.

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

   INFO-CODE:  0
   Purpose:  Other Error
   Reference:  Section 3.1




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   INFO-CODE:  1
   Purpose:  Unsupported DNSKEY Algorithm
   Reference:  Section 3.2

   INFO-CODE:  2
   Purpose:  Unsupported DS Algorithm
   Reference:  Section 3.3

   INFO-CODE:  3
   Purpose:  Stale Answer
   Reference:  Section 3.4

   INFO-CODE:  4
   Purpose:  Forged Answer
   Reference:  Section 3.5

   INFO-CODE:  5
   Purpose:  DNSSEC Indeterminate
   Reference:  Section 3.6

   INFO-CODE:  6
   Purpose:  DNSSEC Bogus
   Reference:  Section 3.7

   INFO-CODE:  7
   Purpose:  Signature Expired
   Reference:  Section 3.8

   INFO-CODE:  8
   Purpose:  Signature Not Yet Valid
   Reference:  Section 3.9

   INFO-CODE:  9
   Purpose:  DNSKEY Missing
   Reference:  Section 3.10

   INFO-CODE:  10
   Purpose:  RRSIGs Missing
   Reference:  Section 3.11

   INFO-CODE:  11
   Purpose:  No Zone Key Bit Set
   Reference:  Section 3.12

   INFO-CODE:  12
   Purpose:  NSEC Missing
   Reference:  Section 3.13




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   INFO-CODE:  13
   Purpose:  Cached Error
   Reference:  Section 3.14

   INFO-CODE:  14
   Purpose:  Not Ready.
   Reference:  Section 3.15

   INFO-CODE:  15
   Purpose:  Blocked
   Reference:  Section 3.16

   INFO-CODE:  16
   Purpose:  Censored
   Reference:  Section 3.17

   INFO-CODE:  17
   Purpose:  Prohibited
   Reference:  Section 3.18

   INFO-CODE:  18
   Purpose:  Filtered
   Reference:  Section 3.19

   INFO-CODE:  19
   Purpose:  Stale NXDomain Answer
   Reference:  Section 3.20

   INFO-CODE:  20
   Purpose:  Lame
   Reference:  Section 3.21

   INFO-CODE:  21
   Purpose:  Deprecated
   Reference:  Section 3.22

   INFO-CODE:  22
   Purpose:  No Reachable Authority
   Reference:  Section 3.23

   INFO-CODE:  23
   Purpose:  Network Error
   Reference:  Section 3.24








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5.  Security Considerations

   Though DNSSEC continues to be deployed, unfortunately a significant
   number of clients (~11% according to [GeoffValidation]) that receive
   a SERVFAIL from a validating resolver because of a DNSSEC validaion
   issue will simply ask the next (potentially non-validating) resolver
   in their list, and thus don't get any of the protections which DNSSEC
   should provide.

   This information is unauthenticated information, and an attacker (e.g
   a MITM or malicious recursive server) could insert an extended error
   response into already untrusted data -- ideally clients and resolvers
   would not trust any unauthenticated information, but until we live in
   an era where all DNS answers are authenticated via DNSSEC or other
   mechanisms [RFC2845] [RFC8094], there are some tradeoffs.  As an
   example, an attacker who is able to insert the DNSSEC Bogus Extended
   Error into a packet could instead simply reply with a fictitious
   address (A or AAAA) record.

6.  Acknowledgements

   The authors wish to thank Joe Abley, Mark Andrews, Vittorio Bertola,
   Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans, Peter DeVries,
   Peter van Dijk, Donald Eastlake, Bob Harold, Paul Hoffman, Geoff
   Huston, Shane Kerr, Edward Lewis, Carlos M.  Martinez, George
   Michelson, Michael Sheldon, Puneet Sood, Petr Spacek, Ondrej Sury,
   Loganaden Velvindron, and Paul Vixie.  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.

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

7.  References

7.1.  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/info/rfc2119>.






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   [RFC2434]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", RFC 2434,
              DOI 10.17487/RFC2434, October 1998, <https://www.rfc-
              editor.org/info/rfc2434>.

   [RFC2671]  Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
              RFC 2671, DOI 10.17487/RFC2671, August 1999,
              <https://www.rfc-editor.org/info/rfc2671>.

   [RFC6891]  Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
              for DNS (EDNS(0))", STD 75, RFC 6891,
              DOI 10.17487/RFC6891, April 2013, <https://www.rfc-
              editor.org/info/rfc6891>.

7.2.  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>.

   [RFC2845]  Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
              Wellington, "Secret Key Transaction Authentication for DNS
              (TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
              <https://www.rfc-editor.org/info/rfc2845>.

   [RFC8094]  Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
              Transport Layer Security (DTLS)", RFC 8094,
              DOI 10.17487/RFC8094, February 2017, <https://www.rfc-
              editor.org/info/rfc8094>.

Authors' Addresses

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

   Email: warren@kumari.net











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

   Email: each@isc.org


   Roy Arends
   ICANN

   Email: roy.arends@icann.org


   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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