draft-ietf-dnsop-extended-error-16.txt   rfc8914.txt 
Network Working Group W. Kumari Internet Engineering Task Force (IETF) W. Kumari
Internet-Draft Google Request for Comments: 8914 Google
Intended status: Standards Track E. Hunt Category: Standards Track E. Hunt
Expires: November 6, 2020 ISC ISSN: 2070-1721 ISC
R. Arends R. Arends
ICANN ICANN
W. Hardaker W. Hardaker
USC/ISI USC/ISI
D. Lawrence D. Lawrence
Oracle + Dyn Salesforce
May 05, 2020 October 2020
Extended DNS Errors Extended DNS Errors
draft-ietf-dnsop-extended-error-16
Abstract Abstract
This document defines an extensible method to return additional This document defines an extensible method to return additional
information about the cause of DNS errors. Though created primarily information about the cause of DNS errors. Though created primarily
to extend SERVFAIL to provide additional information about the cause to extend SERVFAIL to provide additional information about the cause
of DNS and DNSSEC failures, the Extended DNS Errors option defined in of DNS and DNSSEC failures, the Extended DNS Errors option defined in
this document allows all response types to contain extended error this document allows all response types to contain extended error
information. Extended DNS Error information does not change the information. Extended DNS Error information does not change the
processing of RCODEs. processing of RCODEs.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
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 This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on November 6, 2020. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8914.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction and background . . . . . . . . . . . . . . . . . 3 1. Introduction and Background
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Notation
2. Extended DNS Error EDNS0 option format . . . . . . . . . . . 4 2. Extended DNS Error EDNS0 Option Format
3. Extended DNS Error Processing . . . . . . . . . . . . . . . . 5 3. Extended DNS Error Processing
4. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 5 4. Defined Extended DNS Errors
4.1. Extended DNS Error Code 0 - Other . . . . . . . . . . . . 6 4.1. Extended DNS Error Code 0 - Other
4.2. Extended DNS Error Code 1 - 4.2. Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm
Unsupported DNSKEY Algorithm . . . . . . . . . . . . . . 6 4.3. Extended DNS Error Code 2 - Unsupported DS Digest Type
4.3. Extended DNS Error Code 2 - Unsupported DS 4.4. Extended DNS Error Code 3 - Stale Answer
Digest Type . . . . . . . . . . . . . . . . . . . . . . . 6 4.5. Extended DNS Error Code 4 - Forged Answer
4.4. Extended DNS Error Code 3 - Stale Answer . . . . . . . . 6 4.6. Extended DNS Error Code 5 - DNSSEC Indeterminate
4.5. Extended DNS Error Code 4 - Forged Answer . . . . . . . . 6 4.7. Extended DNS Error Code 6 - DNSSEC Bogus
4.6. Extended DNS Error Code 5 - DNSSEC Indeterminate . . . . 6 4.8. Extended DNS Error Code 7 - Signature Expired
4.7. Extended DNS Error Code 6 - DNSSEC Bogus . . . . . . . . 6 4.9. Extended DNS Error Code 8 - Signature Not Yet Valid
4.8. Extended DNS Error Code 7 - Signature Expired . . . . . . 6 4.10. Extended DNS Error Code 9 - DNSKEY Missing
4.9. Extended DNS Error Code 8 - Signature Not Yet Valid . . . 7 4.11. Extended DNS Error Code 10 - RRSIGs Missing
4.10. Extended DNS Error Code 9 - DNSKEY Missing . . . . . . . 7 4.12. Extended DNS Error Code 11 - No Zone Key Bit Set
4.11. Extended DNS Error Code 10 - RRSIGs Missing . . . . . . . 7 4.13. Extended DNS Error Code 12 - NSEC Missing
4.12. Extended DNS Error Code 11 - No Zone Key Bit Set . . . . 7 4.14. Extended DNS Error Code 13 - Cached Error
4.13. Extended DNS Error Code 12 - NSEC Missing . . . . . . . . 7 4.15. Extended DNS Error Code 14 - Not Ready
4.14. Extended DNS Error Code 13 - Cached Error . . . . . . . . 7 4.16. Extended DNS Error Code 15 - Blocked
4.15. Extended DNS Error Code 14 - Not Ready . . . . . . . . . 7 4.17. Extended DNS Error Code 16 - Censored
4.16. Extended DNS Error Code 15 - Blocked . . . . . . . . . . 7 4.18. Extended DNS Error Code 17 - Filtered
4.17. Extended DNS Error Code 16 - Censored . . . . . . . . . . 7 4.19. Extended DNS Error Code 18 - Prohibited
4.18. Extended DNS Error Code 17 - Filtered . . . . . . . . . . 8 4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer
4.19. Extended DNS Error Code 18 - Prohibited . . . . . . . . . 8 4.21. Extended DNS Error Code 20 - Not Authoritative
4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer . . . 8 4.22. Extended DNS Error Code 21 - Not Supported
4.21. Extended DNS Error Code 20 - Not Authoritative . . . . . 8 4.23. Extended DNS Error Code 22 - No Reachable Authority
4.22. Extended DNS Error Code 21 - Not Supported . . . . . . . 8 4.24. Extended DNS Error Code 23 - Network Error
4.23. Extended DNS Error Code 22 - No Reachable Authority . . . 8 4.25. Extended DNS Error Code 24 - Invalid Data
4.24. Extended DNS Error Code 23 - Network Error . . . . . . . 8 5. IANA Considerations
4.25. Extended DNS Error Code 24 - Invalid Data . . . . . . . . 9 5.1. A New Extended DNS Error Code EDNS Option
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5.2. New Registry for Extended DNS Error Codes
5.1. A New Extended DNS Error Code EDNS Option . . . . . . . . 9 6. Security Considerations
5.2. New Registry for Extended DNS Error Codes . . . . . . . . 9 7. References
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7.1. Normative References
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 7.2. Informative References
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 Acknowledgements
8.1. Normative References . . . . . . . . . . . . . . . . . . 13 Authors' Addresses
8.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction and background 1. Introduction and Background
There are many reasons that a DNS query may fail, some of them There are many reasons that a DNS query may fail -- some of them
transient, some permanent; some can be resolved by querying another transient, some permanent; some can be resolved by querying another
server, some are likely best handled by stopping resolution. server, some are likely best handled by stopping resolution.
Unfortunately, the error signals that a DNS server can return are Unfortunately, the error signals that a DNS server can return are
very limited, and are not very expressive. This means that very limited and are not very expressive. This means that
applications and resolvers often have to "guess" at what the issue is applications and resolvers often have to "guess" at what the issue
- e.g. was the answer marked REFUSED because of a lame delegation, or is, e.g., was the answer marked REFUSED because of a lame delegation
because the nameserver is still starting up and loading zones? Is a or because the nameserver is still starting up and loading zones? Is
SERVFAIL a DNSSEC validation issue, or is the nameserver experiencing a SERVFAIL a DNSSEC validation issue, or is the nameserver
some other failure? What error messages should be presented to the experiencing some other failure? What error messages should be
user or logged under these conditions? presented to the user or logged under these conditions?
A good example of issues that would benefit from additional error A good example of issues that would benefit from additional error
information are errors caused by DNSSEC validation issues. When a information are errors caused by DNSSEC validation issues. When a
stub resolver queries a name which is DNSSEC bogus [RFC8499] (using a stub resolver queries a name that is DNSSEC bogus [RFC8499] (using a
validating resolver), the stub resolver receives only a SERVFAIL in validating resolver), the stub resolver receives only a SERVFAIL in
response. Unfortunately, the SERVFAIL Response Code (RCODE) is used response. Unfortunately, the SERVFAIL Response Code (RCODE) is used
to signal many sorts of DNS errors, and so the stub resolver's only to signal many sorts of DNS errors, and so the stub resolver's only
option is to ask the next configured DNS resolver. The result of option is to ask the next configured DNS resolver. The result of
trying the next resolver is one of two outcomes: either the next trying the next resolver is one of two outcomes: either the next
resolver also validates, and a SERVFAIL is returned again, or the resolver also validates and a SERVFAIL is returned again or the next
next resolver is not a validating resolver, and the user is returned resolver is not a validating resolver and the user is returned a
a potentially harmful result. With an Extended DNS Error (EDE) potentially harmful result. With an Extended DNS Error (EDE) option
option enclosed in the response message, the resolver is able to enclosed in the response message, the resolver is able to return a
return a more descriptive reason as to why any failures happened, or more descriptive reason as to why any failures happened or add
add additional context to a message containing a NOERROR RCODE. additional context to a message containing a NOERROR RCODE.
This document specifies a mechanism to extend DNS errors to provide This document specifies a mechanism to extend DNS errors to provide
additional information about the cause of an error. These extended additional information about the cause of an error. The Extended DNS
DNS error codes are described in this document can be used by any Error codes described in this document can be used by any system that
system that sends DNS queries and receives a response containing an sends DNS queries and receives a response containing an EDE option.
EDE option. Different codes are useful in different circumstances, Different codes are useful in different circumstances, and thus
and thus different systems (stub resolvers, recursive resolvers, and different systems (stub resolvers, recursive resolvers, and
authoritative resolvers) might receive and use them. authoritative resolvers) might receive and use them.
1.1. Requirements notation 1.1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. Extended DNS Error EDNS0 option format 2. Extended DNS Error EDNS0 Option Format
This draft uses an EDNS0 ([RFC6891]) option to include Extended DNS This document uses an Extended Mechanism for DNS (EDNS0) [RFC6891]
Error (EDE) information in DNS messages. The option is structured as option to include Extended DNS Error (EDE) information in DNS
follows: messages. The option is structured as follows:
1 1 1 1 1 1 1 1 1 1 1 1
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
0: | OPTION-CODE | 0: | OPTION-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
2: | OPTION-LENGTH | 2: | OPTION-LENGTH |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
4: | INFO-CODE | 4: | INFO-CODE |
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
6: / EXTRA-TEXT ... / 6: / EXTRA-TEXT ... /
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
Field definition details: Field definition details:
o OPTION-CODE, 2-octets/16-bits (defined in [RFC6891]]), for EDE is OPTION-CODE:
TBD. [RFC Editor: change TBD to the proper code once assigned by 2 octets / 16 bits (defined in [RFC6891]) contains the value 15
IANA.] for EDE.
o OPTION-LENGTH, 2-octets/16-bits ((defined in [RFC6891]]) contains
the length of the payload (everything after OPTION-LENGTH) in OPTION-LENGTH:
octets and should be 2 plus the length of the EXTRA-TEXT field 2 octets / 16 bits (defined in [RFC6891]) contains the length of
(which may be a zero-length string). the payload (everything after OPTION-LENGTH) in octets and should
o INFO-CODE, 16-bits, which is the principal contribution of this be 2 plus the length of the EXTRA-TEXT field (which may be a zero-
document. This 16-bit value, encoded in network (MSB) byte order, length string).
provides the additional context for the RESPONSE-CODE of the DNS
message. The INFO-CODE serves as an index into the "Extended DNS INFO-CODE:
Errors" registry defined and created in Section 5.2. 16 bits, which is the principal contribution of this document.
o EXTRA-TEXT, a variable length, UTF-8 encoded [RFC5198], text field This 16-bit value, encoded in network most significant bit (MSB)
that may hold additional textual information. This information is byte order, provides the additional context for the RESPONSE-CODE
intended for human consumption (not automated parsing). EDE text of the DNS message. The INFO-CODE serves as an index into the
may be null terminated but MUST NOT be assumed to be; the length "Extended DNS Errors" registry, defined and created in
MUST be derived from the OPTION-LENGTH field. The EXTRA-TEXT Section 5.2.
field may be zero octets in length, indicating that there is no
EXTRA-TEXT included. Care should be taken not to include private EXTRA-TEXT:
information in the EXTRA-TEXT field that an observer would not a variable-length, UTF-8-encoded [RFC5198] text field that may
otherwise have access to, such as account numbers. hold additional textual information. This information is intended
for human consumption (not automated parsing). EDE text may be
null terminated but MUST NOT be assumed to be; the length MUST be
derived from the OPTION-LENGTH field. The EXTRA-TEXT field may be
zero octets in length, indicating that there is no EXTRA-TEXT
included. Care should be taken not to include private information
in the EXTRA-TEXT field 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 The Extended DNS Error (EDE) option can be included in any response
(SERVFAIL, NXDOMAIN, REFUSED, and even NOERROR, etc) to a query that (SERVFAIL, NXDOMAIN, REFUSED, even NOERROR, etc.) to a query that
includes OPT Pseudo-RR [RFC6891]. This document includes a set of includes an OPT pseudo-RR [RFC6891]. This document includes a set of
initial codepoints, but is extensible via the IANA registry defined initial codepoints but is extensible via the IANA registry defined
and created in Section 5.2. and created in Section 5.2.
3. Extended DNS Error Processing 3. Extended DNS Error Processing
When the response grows beyond the requestor's UDP payload size When the response grows beyond the requestor's UDP payload size
[RFC6891], servers SHOULD truncate messages by dropping EDE options [RFC6891], servers SHOULD truncate messages by dropping EDE options
before dropping other data from packets. Implementations SHOULD set before dropping other data from packets. Implementations SHOULD set
the truncation bit when dropping EDE options. Because long EXTRA- the truncation bit when dropping EDE options. Because long EXTRA-
TEXT fields may trigger truncation (which is undesirable given the TEXT fields may trigger truncation (which is undesirable given the
supplemental nature of EDE) implementers and operators creating EDE supplemental nature of EDE), implementers and operators creating EDE
options SHOULD avoid lengthy EXTRA-TEXT contents. options SHOULD avoid lengthy EXTRA-TEXT contents.
When a resolver or forwarder receives an EDE option, whether or not When a resolver or forwarder receives an EDE option, whether or not
(and how) to pass along EDE information on to their original client (and how) to pass along EDE information on to their original client
is implementation dependent. Implementations MAY choose to not is implementation dependent. Implementations MAY choose to not
forward information, or they MAY choose to create a new EDE option(s) forward information, or they MAY choose to create a new EDE option(s)
that conveys the information encoded in the received EDE. When doing that conveys the information encoded in the received EDE. When doing
so, the source of the error SHOULD be attributed in the EXTRA-TEXT so, the source of the error SHOULD be attributed in the EXTRA-TEXT
field, since an EDNS0 option received by the original client will field, since an EDNS0 option received by the original client will
appear to have come from the resolver or forwarder sending it. appear to have come from the resolver or forwarder sending it.
This document does not allow or prohibit any particular extended This document does not allow or prohibit any particular extended
error codes and information to 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 Some combinations of extended error codes and RCODEs may seem
nonsensical (such as resolver-specific extended error codes in nonsensical (such as resolver-specific extended error codes received
responses from authoritative servers), so systems interpreting the in responses from authoritative servers), so systems interpreting the
extended error codes MUST NOT assume that a combination will make extended error codes MUST NOT assume that a combination will make
sense. Receivers MUST be able to accept EDE codes and EXTRA-TEXT in sense. Receivers MUST be able to accept EDE codes and EXTRA-TEXT in
all messages, including those with a NOERROR RCODE, but need not act all messages, including those with a NOERROR RCODE but need not act
on them. Applications MUST continue to follow requirements from on them. Applications MUST continue to follow requirements from
applicable specifications on how to process RCODEs no matter what EDE applicable specifications on how to process RCODEs no matter what EDE
values are also received. Senders MAY include more than one EDE values are also received. Senders MAY include more than one EDE
option and receivers MUST be able to accept (but not necessarily option and receivers MUST be able to accept (but not necessarily
process or act on) multiple EDE options in a DNS message. process or act on) multiple EDE options in a DNS message.
4. Defined Extended DNS Errors 4. Defined Extended DNS Errors
This document defines some initial EDE codes. The mechanism is This document defines some initial EDE codes. The mechanism is
intended to be extensible, and additional code-points can be intended to be extensible, and additional codepoints can be
registered in the "Extended DNS Errors" registry Section 5.2. The registered in the "Extended DNS Errors" registry (Section 5.2). The
INFO-CODE from the EDE EDNS option is used to serve as an index into 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 the "Extended DNS Error" IANA registry, the initial values for which
are defined in the following sub-sections. are defined in the following subsections.
4.1. Extended DNS Error Code 0 - Other 4.1. Extended DNS Error Code 0 - Other
The error in question falls into a category that does not match known The error in question falls into a category that does not match known
extended error codes. Implementations SHOULD include an EXTRA-TEXT extended error codes. Implementations SHOULD include an EXTRA-TEXT
value to augment this error code with additional information. value to augment this error code with additional information.
4.2. Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm 4.2. Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm
The resolver attempted to perform DNSSEC validation, but a DNSKEY The resolver attempted to perform DNSSEC validation, but a DNSKEY
RRSET contained only unsupported DNSSEC algorithms. RRset contained only unsupported DNSSEC algorithms.
4.3. Extended DNS Error Code 2 - Unsupported DS Digest Type 4.3. Extended DNS Error Code 2 - Unsupported DS Digest Type
The resolver attempted to perform DNSSEC validation, but a DS RRSET The resolver attempted to perform DNSSEC validation, but a DS RRset
contained only unsupported Digest Types. contained only unsupported Digest Types.
4.4. Extended DNS Error Code 3 - Stale Answer 4.4. Extended DNS Error Code 3 - Stale Answer
The resolver was unable to resolve the answer within its time limits The resolver was unable to resolve the answer within its time limits
and decided to answer with previously cached data instead of and decided to answer with previously cached data instead of
answering with an error. This is typically caused by problems answering with an error. This is typically caused by problems
communicating with an authoritative server, possibly as result of a communicating with an authoritative server, possibly as result of a
denial of service (DoS) attack against another network. (See also denial of service (DoS) attack against another network. (See also
Code 19.) Code 19.)
4.5. Extended DNS Error Code 4 - Forged Answer 4.5. Extended DNS Error Code 4 - Forged Answer
For policy reasons (legal obligation, or malware filtering, for For policy reasons (legal obligation or malware filtering, for
instance), an answer was forged. Note that this should be used when instance), an answer was forged. Note that this should be used when
an answer is still provided, not when failure codes are returned an answer is still provided, not when failure codes are returned
instead. See Blocked(15), Censored (16), and Filtered (17) for use instead. See Blocked (15), Censored (16), and Filtered (17) for use
when returning other response codes. when returning other response codes.
4.6. Extended DNS Error Code 5 - DNSSEC Indeterminate 4.6. Extended DNS Error Code 5 - DNSSEC Indeterminate
The resolver attempted to perform DNSSEC validation, but validation The resolver attempted to perform DNSSEC validation, but validation
ended in the Indeterminate state [RFC4035]. ended in the Indeterminate state [RFC4035].
4.7. Extended DNS Error Code 6 - DNSSEC Bogus 4.7. Extended DNS Error Code 6 - DNSSEC Bogus
The resolver attempted to perform DNSSEC validation, but validation The resolver attempted to perform DNSSEC validation, but validation
ended in the Bogus state. ended in the Bogus state.
4.8. Extended DNS Error Code 7 - Signature Expired 4.8. Extended DNS Error Code 7 - Signature Expired
The resolver attempted to perform DNSSEC validation, but no The resolver attempted to perform DNSSEC validation, but no
signatures are presently valid and some (often all) are expired. signatures are presently valid and some (often all) are expired.
4.9. Extended DNS Error Code 8 - Signature Not Yet Valid 4.9. Extended DNS Error Code 8 - Signature Not Yet Valid
The resolver attempted to perform DNSSEC validation, but but no The resolver attempted to perform DNSSEC validation, but no
signatures are presently valid and at least some are not yet valid. signatures are presently valid and at least some are not yet valid.
4.10. Extended DNS Error Code 9 - DNSKEY Missing 4.10. Extended DNS Error Code 9 - DNSKEY Missing
A DS record existed at a parent, but no supported matching DNSKEY A DS record existed at a parent, but no supported matching DNSKEY
record could be found for the child. record could be found for the child.
4.11. Extended DNS Error Code 10 - RRSIGs Missing 4.11. Extended DNS Error Code 10 - RRSIGs Missing
The resolver attempted to perform DNSSEC validation, but no RRSIGs The resolver attempted to perform DNSSEC validation, but no RRSIGs
skipping to change at page 7, line 37 skipping to change at line 319
The resolver attempted to perform DNSSEC validation, but the The resolver attempted to perform DNSSEC validation, but the
requested data was missing and a covering NSEC or NSEC3 was not requested data was missing and a covering NSEC or NSEC3 was not
provided. provided.
4.14. Extended DNS Error Code 13 - Cached Error 4.14. Extended DNS Error Code 13 - Cached Error
The resolver is returning the SERVFAIL RCODE from its cache. The resolver is returning the SERVFAIL RCODE from its cache.
4.15. Extended DNS Error Code 14 - Not Ready 4.15. Extended DNS Error Code 14 - Not Ready
The server is unable to answer the query as it was not fully The server is unable to answer the query, as it was not fully
functional when the query was received. functional when the query was received.
4.16. Extended DNS Error Code 15 - Blocked 4.16. Extended DNS Error Code 15 - Blocked
The server is unable to respond to the request because the domain is The server is unable to respond to the request because the domain is
blacklisted due to an internal security policy imposed by the on a blocklist due to an internal security policy imposed by the
operator of the server resolving or forwarding the query. operator of the server resolving or forwarding the query.
4.17. Extended DNS Error Code 16 - Censored 4.17. Extended DNS Error Code 16 - Censored
The server is unable to respond to the request because the domain is The server is unable to respond to the request because the domain is
blacklisted due to an external requirement imposed by an entity other on a blocklist due to an external requirement imposed by an entity
than the operator of the server resolving or forwarding the query. other than the operator of the server resolving or forwarding the
Note that how the imposed policy is applied is irrelevant (in-band query. Note that how the imposed policy is applied is irrelevant
DNS filtering, court order, etc). (in-band DNS filtering, court order, etc.).
4.18. Extended DNS Error Code 17 - Filtered 4.18. Extended DNS Error Code 17 - Filtered
The server is unable to respond to the request because the domain is The server is unable to respond to the request because the domain is
blacklisted as requested by the client. Functionally, this amounts on a blocklist as requested by the client. Functionally, this
to "you requested that we filter domains like this one." amounts to "you requested that we filter domains like this one."
4.19. Extended DNS Error Code 18 - Prohibited 4.19. Extended DNS Error Code 18 - Prohibited
An authoritative server or recursive resolver that receives a query An authoritative server or recursive resolver that receives a query
from an "unauthorized" client can annotate its REFUSED message with from an "unauthorized" client can annotate its REFUSED message with
this code. Examples of "unauthorized" clients are recursive queries this code. Examples of "unauthorized" clients are recursive queries
from IP addresses outside the network, blacklisted IP addresses, from IP addresses outside the network, blocklisted IP addresses,
local policy, etc. local policy, etc.
4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer 4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer
The resolver was unable to resolve an answer within its configured The resolver was unable to resolve an answer within its configured
time limits and decided to answer with a previously cached NXDOMAIN time limits and decided to answer with a previously cached NXDOMAIN
answer instead of answering with an error. This may be caused, for answer instead of answering with an error. This may be caused, for
example, by problems communicating with an authoritative server, example, by problems communicating with an authoritative server,
possibly as result of a denial of service (DoS) attack against possibly as result of a denial of service (DoS) attack against
another network. (See also Code 3.) another network. (See also Code 3.)
4.21. Extended DNS Error Code 20 - Not Authoritative 4.21. Extended DNS Error Code 20 - Not Authoritative
An authoritative server that receives a query with the RD bit clear, An authoritative server that receives a query with the Recursion
or when it is not configured for recursion for a domain for which it Desired (RD) bit clear, or when it is not configured for recursion
is not authoritative SHOULD include this EDE code in the REFUSED for a domain for which it is not authoritative, SHOULD include this
response. A resolver that receives a query with the RD bit clear EDE code in the REFUSED response. A resolver that receives a query
SHOULD include this EDE code in the REFUSED response. with the RD bit clear SHOULD include this EDE code in the REFUSED
response.
4.22. Extended DNS Error Code 21 - Not Supported 4.22. Extended DNS Error Code 21 - Not Supported
The requested operation or query is not supported. The requested operation or query is not supported.
4.23. Extended DNS Error Code 22 - No Reachable Authority 4.23. Extended DNS Error Code 22 - No Reachable Authority
The resolver could not reach any of the authoritative name servers The resolver could not reach any of the authoritative name servers
(or they potentially refused to reply). (or they potentially refused to reply).
4.24. Extended DNS Error Code 23 - Network Error 4.24. Extended DNS Error Code 23 - Network Error
An unrecoverable error occurred while communicating with another An unrecoverable error occurred while communicating with another
server. server.
4.25. Extended DNS Error Code 24 - Invalid Data 4.25. Extended DNS Error Code 24 - Invalid Data
The authoritative server cannot answer with data for a zone it is The authoritative server cannot answer with data for a zone it is
otherwise configured to support. Examples of this include its most otherwise configured to support. Examples of this include its most
recent zone being too old, or having expired. recent zone being too old or having expired.
5. IANA Considerations 5. IANA Considerations
5.1. A New Extended DNS Error Code EDNS Option 5.1. A New Extended DNS Error Code EDNS Option
This document defines a new EDNS(0) option, entitled "Extended DNS This document defines a new EDNS(0) option, entitled "Extended DNS
Error", assigned a value of TBD from the "DNS EDNS0 Option Codes Error", with the assigned value of 15 from the "DNS EDNS0 Option
(OPT)" registry [to be removed upon publication: Codes (OPT)" registry:
[http://www.iana.org/assignments/dns-parameters/dns-
parameters.xhtml#dns-parameters-11]
Value Name Status Reference
----- ---------------- ------ ------------------
TBD Extended DNS Error Standard [ This document ]
5.2. New Registry for Extended DNS Error Codes
IANA is requested to create and maintain a new registry table called
"Extended DNS Error Codes" on the "Domain Name System (DNS)
Parameters" web page as follows:
Registry Name: Extended DNS Error Codes
Registration Procedures:
o 0 - 49151: First come, first served.
o 49152 - 65535: Private use.
Reference: [this document]
The Extended DNS Error Codes registry is a table with three columns:
INFO-CODE, Purpose, and Reference. The initial contents is as below
with [this document] added to each reference given.
INFO-CODE: 0
Purpose: Other Error
Reference: Section 4.1
INFO-CODE: 1
Purpose: Unsupported DNSKEY Algorithm
Reference: Section 4.2
INFO-CODE: 2
Purpose: Unsupported DS Digest Type
Reference: Section 4.3
INFO-CODE: 3
Purpose: Stale Answer
Reference: Section 4.4, [RFC8767]
INFO-CODE: 4
Purpose: Forged Answer
Reference: Section 4.5
INFO-CODE: 5
Purpose: DNSSEC Indeterminate
Reference: Section 4.6
INFO-CODE: 6
Purpose: DNSSEC Bogus
Reference: Section 4.7
INFO-CODE: 7
Purpose: Signature Expired
Reference: Section 4.8
INFO-CODE: 8
Purpose: Signature Not Yet Valid
Reference: Section 4.9
INFO-CODE: 9
Purpose: DNSKEY Missing
Reference: Section 4.10
INFO-CODE: 10
Purpose: RRSIGs Missing
Reference: Section 4.11
INFO-CODE: 11
Purpose: No Zone Key Bit Set
Reference: Section 4.12
INFO-CODE: 12
Purpose: NSEC Missing
Reference: Section 4.13
INFO-CODE: 13
Purpose: Cached Error
Reference: Section 4.14
INFO-CODE: 14
Purpose: Not Ready.
Reference: Section 4.15
INFO-CODE: 15
Purpose: Blocked
Reference: Section 4.16
INFO-CODE: 16
Purpose: Censored
Reference: Section 4.17
INFO-CODE: 17 +=======+====================+==========+===========+
Purpose: Filtered | Value | Name | Status | Reference |
Reference: Section 4.18 +=======+====================+==========+===========+
| 15 | Extended DNS Error | Standard | RFC 8914 |
+-------+--------------------+----------+-----------+
INFO-CODE: 18 Table 1
Purpose: Prohibited
Reference: Section 4.19
INFO-CODE: 19 5.2. New Registry for Extended DNS Error Codes
Purpose: Stale NXDomain Answer
Reference: Section 4.20
INFO-CODE: 20 IANA has created and will maintain a new registry called "Extended
Purpose: Not Authoritative DNS Error Codes" on the "Domain Name System (DNS) Parameters" web
Reference: Section 4.21 page as follows:
INFO-CODE: 21 +===============+=========================+
Purpose: Not Supported | Range | Registration Procedures |
Reference: Section 4.22 +===============+=========================+
| 0 - 49151 | First Come First Served |
+---------------+-------------------------+
| 49152 - 65535 | Private Use |
+---------------+-------------------------+
INFO-CODE: 22 Table 2
Purpose: No Reachable Authority
Reference: Section 4.23
INFO-CODE: 23 The "Extended DNS Error Codes" registry is a table with three
Purpose: Network Error columns: INFO-CODE, Purpose, and Reference. The initial content is
Reference: Section 4.24 as below.
INFO-CODE: 24 +=============+==============================+===============+
Purpose: Invalid Data | INFO-CODE | Purpose | Reference |
Reference: Section 4.25 +=============+==============================+===============+
| 0 | Other Error | Section 4.1 |
+-------------+------------------------------+---------------+
| 1 | Unsupported DNSKEY Algorithm | Section 4.2 |
+-------------+------------------------------+---------------+
| 2 | Unsupported DS Digest Type | Section 4.3 |
+-------------+------------------------------+---------------+
| 3 | Stale Answer | Section 4.4 |
| | | and [RFC8767] |
+-------------+------------------------------+---------------+
| 4 | Forged Answer | Section 4.5 |
+-------------+------------------------------+---------------+
| 5 | DNSSEC Indeterminate | Section 4.6 |
+-------------+------------------------------+---------------+
| 6 | DNSSEC Bogus | Section 4.7 |
+-------------+------------------------------+---------------+
| 7 | Signature Expired | Section 4.8 |
+-------------+------------------------------+---------------+
| 8 | Signature Not Yet Valid | Section 4.9 |
+-------------+------------------------------+---------------+
| 9 | DNSKEY Missing | Section 4.10 |
+-------------+------------------------------+---------------+
| 10 | RRSIGs Missing | Section 4.11 |
+-------------+------------------------------+---------------+
| 11 | No Zone Key Bit Set | Section 4.12 |
+-------------+------------------------------+---------------+
| 12 | NSEC Missing | Section 4.13 |
+-------------+------------------------------+---------------+
| 13 | Cached Error | Section 4.14 |
+-------------+------------------------------+---------------+
| 14 | Not Ready | Section 4.15 |
+-------------+------------------------------+---------------+
| 15 | Blocked | Section 4.16 |
+-------------+------------------------------+---------------+
| 16 | Censored | Section 4.17 |
+-------------+------------------------------+---------------+
| 17 | Filtered | Section 4.18 |
+-------------+------------------------------+---------------+
| 18 | Prohibited | Section 4.19 |
+-------------+------------------------------+---------------+
| 19 | Stale NXDomain Answer | Section 4.20 |
+-------------+------------------------------+---------------+
| 20 | Not Authoritative | Section 4.21 |
+-------------+------------------------------+---------------+
| 21 | Not Supported | Section 4.22 |
+-------------+------------------------------+---------------+
| 22 | No Reachable Authority | Section 4.23 |
+-------------+------------------------------+---------------+
| 23 | Network Error | Section 4.24 |
+-------------+------------------------------+---------------+
| 24 | Invalid Data | Section 4.25 |
+-------------+------------------------------+---------------+
| 25-49151 | Unassigned | |
+-------------+------------------------------+---------------+
| 49152-65535 | Reserved for Private Use | Section 5.2 |
+-------------+------------------------------+---------------+
INFO-CODE: 25-65535 Table 3
Purpose: Unassigned
Reference: Section 5.2
6. Security Considerations 6. Security Considerations
Though DNSSEC continues to be deployed, unfortunately a significant Though DNSSEC continues to be deployed, unfortunately a significant
number of clients (~11% according to [GeoffValidation]) that receive number of clients (~11% according to [GeoffValidation]) that receive
a SERVFAIL from a validating resolver because of a DNSSEC validation a SERVFAIL from a validating resolver because of a DNSSEC validation
issue will simply ask the next (potentially non-validating) resolver issue will simply ask the next (potentially non-validating) resolver
in their list, and thus don't get the protections which DNSSEC should in their list and thus don't get the protections that DNSSEC should
provide. provide.
EDE information is unauthenticated information, unless secured by a EDE information is unauthenticated information, unless secured by a
form of secured DNS transaction such as [RFC2845], [RFC2931], form of secured DNS transaction, such as [RFC2845], [RFC2931],
[RFC8094] or [RFC8484]. An attacker (e.g a MITM or malicious [RFC8094], or [RFC8484]. An attacker (e.g., a man in the middle
recursive server) could insert an extended error response into (MITM) or malicious recursive server) could insert an extended error
untrusted data -- although ideally clients and resolvers would not response into untrusted data -- although, ideally, clients and
trust any unauthenticated information. As such, EDE content should resolvers would not trust any unauthenticated information. As such,
be treated only as diagnostic information and MUST NOT alter DNS EDE content should be treated only as diagnostic information and MUST
protocol processing. Until all DNS answers are authenticated via NOT alter DNS protocol processing. Until all DNS answers are
DNSSEC or the other mechanisms mentioned above, there are some authenticated via DNSSEC or the other mechanisms mentioned above,
tradeoffs. As an example, an attacker who is able to insert the there are some trade-offs. As an example, an attacker who is able to
DNSSEC Bogus Extended Error into a DNS message could instead simply insert the DNSSEC Bogus Extended Error into a DNS message could
reply with a fictitious address (A or AAAA) record. Note that DNS instead simply reply with a fictitious address (A or AAAA) record.
Response Codes (RCODEs) also contain no authentication and can be Note that DNS RCODEs also contain no authentication and can be just
just as easily manipulated. as easily manipulated.
By design, EDE potentially exposes additional information DNS By design, EDE potentially exposes additional information via DNS
resolution processes that may leak information. An example of this resolution processes that may leak information. An example of this
is the Prohibited EDE code (18), which may leak the fact that the is the Prohibited EDE code (18), which may leak the fact that the
name is on a blacklist. name is on a blocklist.
7. Acknowledgements
The authors wish to thank Joe Abley, Mark Andrews, Tim April,
Vittorio Bertola, Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans,
Peter DeVries, 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...
8. References 7. References
8.1. Normative References 7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4035] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "Protocol Modifications for the DNS Security Rose, "Protocol Modifications for the DNS Security
Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005, Extensions", RFC 4035, DOI 10.17487/RFC4035, March 2005,
<https://www.rfc-editor.org/info/rfc4035>. <https://www.rfc-editor.org/info/rfc4035>.
skipping to change at page 13, line 41 skipping to change at line 550
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS [RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499, Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>. January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[RFC8767] Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data [RFC8767] Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data
to Improve DNS Resiliency", RFC 8767, to Improve DNS Resiliency", RFC 8767,
DOI 10.17487/RFC8767, March 2020, DOI 10.17487/RFC8767, March 2020,
<https://www.rfc-editor.org/info/rfc8767>. <https://www.rfc-editor.org/info/rfc8767>.
8.2. Informative References 7.2. Informative References
[GeoffValidation] [GeoffValidation]
APNIC, G. H., "A quick review of DNSSEC Validation in Huston, G., "A quick review of DNSSEC Validation in
today's Internet", June 2016, <http://www.potaroo.net/ today's Internet", June 2016, <http://www.potaroo.net/
presentations/2016-06-27-dnssec.pdf>. presentations/2016-06-27-dnssec.pdf>.
[RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B. [RFC2845] Vixie, P., Gudmundsson, O., Eastlake 3rd, D., and B.
Wellington, "Secret Key Transaction Authentication for DNS Wellington, "Secret Key Transaction Authentication for DNS
(TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000, (TSIG)", RFC 2845, DOI 10.17487/RFC2845, May 2000,
<https://www.rfc-editor.org/info/rfc2845>. <https://www.rfc-editor.org/info/rfc2845>.
[RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures [RFC2931] Eastlake 3rd, D., "DNS Request and Transaction Signatures
( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September ( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
skipping to change at page 14, line 18 skipping to change at line 575
[RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram [RFC8094] Reddy, T., Wing, D., and P. Patil, "DNS over Datagram
Transport Layer Security (DTLS)", RFC 8094, Transport Layer Security (DTLS)", RFC 8094,
DOI 10.17487/RFC8094, February 2017, DOI 10.17487/RFC8094, February 2017,
<https://www.rfc-editor.org/info/rfc8094>. <https://www.rfc-editor.org/info/rfc8094>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS [RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018, (DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/rfc8484>. <https://www.rfc-editor.org/info/rfc8484>.
Acknowledgements
The authors wish to thank Joe Abley, Mark Andrews, Tim April,
Vittorio Bertola, Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans,
Peter DeVries, 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 of them were.
Apologies if we forgot to acknowledge your contributions.
One author also wants to thank the band Infected Mushroom for
providing a good background soundtrack. Another author would like to
thank the band Mushroom Infectors. This was funny at the time we
wrote it, but we cannot remember why...
Authors' Addresses Authors' Addresses
Warren Kumari Warren Kumari
Google Google
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
US United States of America
Email: warren@kumari.net Email: warren@kumari.net
Evan Hunt Evan Hunt
ISC ISC
950 Charter St 950 Charter St
Redwood City, CA 94063 Redwood City, CA 94063
US United States of America
Email: each@isc.org Email: each@isc.org
Roy Arends Roy Arends
ICANN ICANN
Email: roy.arends@icann.org Email: roy.arends@icann.org
Wes Hardaker Wes Hardaker
USC/ISI USC/ISI
P.O. Box 382 P.O. Box 382
Davis, CA 95617 Davis, CA 95617
US United States of America
Email: ietf@hardakers.net Email: ietf@hardakers.net
David C Lawrence David C Lawrence
Oracle + Dyn Salesforce
150 Dow St 415 Mission St
Manchester, NH 03101 San Francisco, CA 94105
US United States of America
Email: tale@dd.org Email: tale@dd.org
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