--- 1/draft-ietf-dnsop-extended-error-09.txt 2019-09-27 17:13:08.110866821 -0700 +++ 2/draft-ietf-dnsop-extended-error-10.txt 2019-09-27 17:13:08.138867633 -0700 @@ -1,51 +1,52 @@ Network Working Group W. Kumari Internet-Draft Google Intended status: Standards Track E. Hunt -Expires: March 13, 2020 ISC +Expires: March 30, 2020 ISC R. Arends ICANN W. Hardaker USC/ISI D. Lawrence Oracle + Dyn - September 10, 2019 + September 27, 2019 Extended DNS Errors - draft-ietf-dnsop-extended-error-09 + draft-ietf-dnsop-extended-error-10 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. + information. Extended DNS Error information does not change the + processing of RCODEs. 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. + This Internet-Draft will expire on March 30, 2020. Copyright Notice Copyright (c) 2019 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 @@ -57,52 +58,53 @@ 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 + 3.3. Extended DNS Error Code 2 - Unsupported DS + Digest Type . . . . . . . . . . . . . . . . . . . . . . . 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 + 3.6. Extended DNS Error Code 5 - DNSSEC Indeterminate . . . . 6 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 + 3.15. Extended DNS Error Code 14 - Not Ready . . . . . . . . . 7 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 + 3.18. Extended DNS Error Code 17 - Filtered . . . . . . . . . . 7 + 3.19. Extended DNS Error Code 17 - Prohibited . . . . . . . . . 7 3.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer . . . 7 - 3.21. Extended DNS Error Code 20 - Lame . . . . . . . . . . . . 7 + 3.21. Extended DNS Error Code 20 - Not Authoritative . . . . . 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 + 3.25. Extended DNS Error Code 24 - Invalid Data . . . . . . . . 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 - 7.1. Normative References . . . . . . . . . . . . . . . . . . 11 + 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 + 7.1. Normative References . . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . 12 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 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 @@ -122,32 +124,34 @@ 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, + 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. + error codes and information to 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. + all messages, including those with a NOERROR RCODE. Receivers MUST + NOT change the processing of RCODEs in messages based on extended + error codes. 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 @@ -170,26 +174,26 @@ 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 + message. The INFO-CODE serves as an index into 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 + Care should be taken 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 registry), but is extensible via the IANA registry to allow additional error and information codes to be defined in the future. @@ -204,58 +208,61 @@ 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. + RRSET contained only unsupported DNSSEC algorithms. -3.3. Extended DNS Error Code 2 - Unsupported DS Algorithm +3.3. Extended DNS Error Code 2 - Unsupported DS Digest Type The resolver attempted to perform DNSSEC validation, but a DS RRSET - contained only unknown algorithms. + contained only unsupported Digest Types. 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. + instance), an answer was forged. Note that this should be used when + an answer is still provided, not when failure codes are returned + instead. See Blocked(15), Censored (16), and Filtered (17) for use + when returning other response codes. 3.6. Extended DNS Error Code 5 - DNSSEC Indeterminate The resolver attempted to perform DNSSEC validation, but validation - ended in the Indeterminate state. + ended in the Indeterminate state [RFC4035]. 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. + The resolver attempted to perform DNSSEC validation, but all + signatures in an RRset in the validation chain were expired. 3.9. Extended DNS Error Code 8 - Signature Not Yet Valid - The resolver attempted to perform DNSSEC validation, but the + The resolver attempted to perform DNSSEC validation, but all 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 @@ -267,86 +274,91 @@ 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. + 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). 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. + The server is unable to respond to the request because the domain is + blacklisted due to an internal security policy imposed by the + operator of 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 + The server is unable to respond to the request because the domain is 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). + to by an external requirement. 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 +3.18. Extended DNS Error Code 17 - Filtered + + The server is unable to respond to the request because the domain is + blacklisted as requested by the client. Functionally, this amounts + to "you requested that we filter domains like this one." + +3.19. 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 + by problems communicating with an authoritative server, possibly as result of a DoS attack against another network. -3.21. Extended DNS Error Code 20 - Lame +3.21. Extended DNS Error Code 20 - Not Authoritative - 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. + An authoritative server that receives a query (with the RD bit clear, + or when not configured for recursion) for a domain for which it is + not authoritative SHOULD include this EDE code in the REFUSED + response. A resolver that receives a query (with the RD bit clear) + SHOULD include this EDE code in the REFUSED response. 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. +3.25. Extended DNS Error Code 24 - Invalid Data + + An authoritative server that cannot answer with data for a zone it is + otherwise configured to support. This may occur because its most + recent zone is too old, or has expired, for example. + 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] @@ -365,31 +377,32 @@ 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 + INFO-CODE: 1 Purpose: Unsupported DNSKEY Algorithm Reference: Section 3.2 INFO-CODE: 2 - Purpose: Unsupported DS Algorithm + Purpose: Unsupported DS Digest Type Reference: Section 3.3 INFO-CODE: 3 Purpose: Stale Answer - Reference: Section 3.4 + Reference: Section 3.4, [I-D.ietf-dnsop-serve-stale] INFO-CODE: 4 Purpose: Forged Answer Reference: Section 3.5 INFO-CODE: 5 Purpose: DNSSEC Indeterminate Reference: Section 3.6 INFO-CODE: 6 @@ -429,102 +443,118 @@ INFO-CODE: 15 Purpose: Blocked Reference: Section 3.16 INFO-CODE: 16 Purpose: Censored Reference: Section 3.17 INFO-CODE: 17 - Purpose: Prohibited + Purpose: Filtered Reference: Section 3.18 INFO-CODE: 18 - Purpose: Filtered + Purpose: Prohibited Reference: Section 3.19 INFO-CODE: 19 Purpose: Stale NXDomain Answer Reference: Section 3.20 INFO-CODE: 20 - Purpose: Lame + Purpose: Not Authoritative 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 + INFO-CODE: 24 + Purpose: Invalid Data + Reference: Section 3.25 + 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. + address (A or AAAA) record. Note that DNS Response Codes also + contain no authentication and can be just as easily manipulated. 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. + Peter van Dijk, Mats Dufberg, Donald Eastlake, Bob Harold, Paul + Hoffman, Geoff Huston, Shane Kerr, Edward Lewis, Carlos M. Martinez, + George Michelson, Eric Orth, Michael Sheldon, Puneet Sood, Petr + Spacek, Ondrej Sury, John Todd, 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 + [I-D.ietf-dnsop-serve-stale] + Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data + to Improve DNS Resiliency", draft-ietf-dnsop-serve- + stale-08 (work in progress), September 2019. + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2434] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 2434, DOI 10.17487/RFC2434, October 1998, . [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, DOI 10.17487/RFC2671, August 1999, . + [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. + Rose, "Protocol Modifications for the DNS Security + Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, + . + [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/RFC6891, April 2013, . 7.2. Informative References [GeoffValidation] IANA, "A quick review of DNSSEC Validation in today's Internet", June 2016,