draft-ietf-dnsop-extended-error-04.txt   draft-ietf-dnsop-extended-error-05.txt 
Network Working Group W. Kumari Network Working Group W. Kumari
Internet-Draft Google Internet-Draft Google
Intended status: Standards Track E. Hunt Intended status: Standards Track E. Hunt
Expires: July 11, 2019 ISC Expires: September 12, 2019 ISC
R. Arends R. Arends
ICANN ICANN
W. Hardaker W. Hardaker
USC/ISI USC/ISI
D. Lawrence D. Lawrence
Oracle + Dyn Oracle + Dyn
January 07, 2019 March 11, 2019
Extended DNS Errors Extended DNS Errors
draft-ietf-dnsop-extended-error-04 draft-ietf-dnsop-extended-error-05
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. information.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 11, 2019. This Internet-Draft will expire on September 12, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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 . . . . . . . . . . . . . . . . . 3
1.1. Requirements notation . . . . . . . . . . . . . . . . . . 3 1.1. Requirements notation . . . . . . . . . . . . . . . . . . 4
2. Extended Error EDNS0 option format . . . . . . . . . . . . . 3 2. Extended Error EDNS0 option format . . . . . . . . . . . . . 4
3. Use of the Extended DNS Error option . . . . . . . . . . . . 4 3. Use of the Extended DNS Error option . . . . . . . . . . . . 5
3.1. The R (Retry) flag . . . . . . . . . . . . . . . . . . . 5 3.1. The R (Retry) flag . . . . . . . . . . . . . . . . . . . 5
3.2. The RESPONSE-CODE field . . . . . . . . . . . . . . . . . 5 3.2. The RESPONSE-CODE field . . . . . . . . . . . . . . . . . 5
3.3. The INFO-CODE field . . . . . . . . . . . . . . . . . . . 5 3.3. The INFO-CODE field . . . . . . . . . . . . . . . . . . . 6
3.4. The EXTRA-TEXT field . . . . . . . . . . . . . . . . . . 5 3.4. The EXTRA-TEXT field . . . . . . . . . . . . . . . . . . 6
4. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 5 4. Defined Extended DNS Errors . . . . . . . . . . . . . . . . . 6
4.1. INFO-CODEs for use with RESPONSE-CODE: NOERROR(0) . . . . 6 4.1. INFO-CODEs for use with RESPONSE-CODE: NOERROR(0) . . . . 6
4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported 4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported
DNSKEY Algorithm . . . . . . . . . . . . . . . . . . 6 DNSKEY Algorithm . . . . . . . . . . . . . . . . . . 6
4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported 4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported
DS Algorithm . . . . . . . . . . . . . . . . . . . . 6 DS Algorithm . . . . . . . . . . . . . . . . . . . . 6
4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2) . . . 6 4.1.3. INFO-CODEs for use with RESPONSE-CODE: NOERROR(3) . . 6
4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus . . 6 4.1.4. NOERROR Extended DNS Error Code 4 - Forged answer . . 7
4.2.2. SERVFAIL Extended DNS Error Code 2 - DNSSEC 4.1.5. SERVFAIL Extended DNS Error Code 5 - DNSSEC
Indeterminate . . . . . . . . . . . . . . . . . . . . 6 Indeterminate . . . . . . . . . . . . . . . . . . . . 7
4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature 4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2) . . . 7
Expired . . . . . . . . . . . . . . . . . . . . . . . 6 4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus . . 7
4.2.4. SERVFAIL Extended DNS Error Code 4 - Signature Not 4.2.2. SERVFAIL Extended DNS Error Code 2 - Signature
Yet Valid . . . . . . . . . . . . . . . . . . . . . . 6 Expired . . . . . . . . . . . . . . . . . . . . . . . 7
4.2.5. SERVFAIL Extended DNS Error Code 5 - DNSKEY missing . 6 4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature Not
4.2.6. SERVFAIL Extended DNS Error Code 6 - RRSIGs missing . 7 Yet Valid . . . . . . . . . . . . . . . . . . . . . . 7
4.2.7. SERVFAIL Extended DNS Error Code 7 - No Zone Key Bit 4.2.4. SERVFAIL Extended DNS Error Code 4 - DNSKEY missing . 7
Set . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2.5. SERVFAIL Extended DNS Error Code 5 - RRSIGs missing . 7
4.3. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5) . . . . 7 4.2.6. SERVFAIL Extended DNS Error Code 6 - No Zone Key Bit
4.3.1. REFUSED Extended DNS Error Code 1 - Lame . . . . . . 7 Set . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.3.2. REFUSED Extended DNS Error Code 2 - Prohibited . . . 7 4.2.7. SERVFAIL Extended DNS Error Code 7 - No
4.4. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 7 Reachable Authority . . . . . . . . . . . . . . . . . 8
4.4.1. NXDOMAIN Extended DNS Error Code 1 - Blocked . . . . 7 4.2.8. SERVFAIL Extended DNS Error Code 8 - NSEC Missing . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 4.2.9. SERVFAIL Extended DNS Error Code 9 - Cached Error . . 8
5.1. new Extended Error Code EDNS Option . . . . . . . . . . . 7 4.2.10. SERVFAIL Extended DNS Error Code 10 - Not Ready . . . 8
5.2. New Extended Error Code EDNS Option . . . . . . . . . . . 8 4.3. INFO-CODEs for use with RESPONSE-CODE: NOTIMP(4) . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 4.3.1. NOTIMP Extended DNS Error Code 1 - Deprecated . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 4.4. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5) . . . . 8
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.4.1. REFUSED Extended DNS Error Code 1 - Lame . . . . . . 8
8.1. Normative References . . . . . . . . . . . . . . . . . . 10 4.4.2. REFUSED Extended DNS Error Code 2 - Prohibited . . . 9
8.2. Informative References . . . . . . . . . . . . . . . . . 10 4.5. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 9
Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 11 4.5.1. NXDOMAIN Extended DNS Error Code 1 - Blocked . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 4.6. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 9
4.6.1. NXDOMAIN Extended DNS Error Code 2 - Censored . . . . 9
4.7. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) . . . 9
4.7.1. NXDOMAIN Extended DNS Error Code 3 - Stale Answer . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5.1. A New Extended Error Code EDNS Option . . . . . . . . . . 9
5.2. New Double-Index Registry Table for Extended Error Codes 10
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . 13
Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 14
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 is
- e.g. was the answer marked REFUSED because of a lame delegation, or - e.g. was the answer marked REFUSED because of a lame delegation, or
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returned again, and the user gets an (largely) incomprehensible error returned again, and the user gets an (largely) incomprehensible error
message; or the next resolver is not a validating resolver, and the message; or the next resolver is not a validating resolver, and the
user is returned a potentially harmful result. user is returned a potentially harmful result.
This document specifies a mechanism to extend (or annotate) DNS This document specifies a mechanism to extend (or annotate) DNS
errors to provide additional information about the cause of the errors to provide additional information about the cause of the
error. When properly authenticated, this information can be used by error. When properly authenticated, this information can be used by
the resolver to make a decision regarding whether or not to retry or the resolver to make a decision regarding whether or not to retry or
it can be used or by technical users attempting to debug issues. it can be used or by technical users attempting to debug issues.
These extended error codes are specially useful when received by
resolvers, to return to stub resolvers or to downstream resolvers.
Authoritative servers MAY parse and use them, but most error codes
would make no sense for them. Authoritative servers may need to
generate extended error codes though.
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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Extended Error EDNS0 option format 2. Extended Error EDNS0 option format
This draft uses an EDNS0 ([RFC2671]) option to include Extended DNS This draft uses an EDNS0 ([RFC2671]) option to include Extended DNS
Error (EDE) information in DNS messages. The option is structured as Error (EDE) information in DNS messages. The option is structured as
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o OPTION-CODE, 2 octets (defined in [RFC6891]), for EDE is TBD. o OPTION-CODE, 2 octets (defined in [RFC6891]), for EDE is TBD.
[RFC Editor: change TBD to the proper code once assigned by IANA.] [RFC Editor: change TBD to the proper code once assigned by IANA.]
o OPTION-LENGTH, 2 octets ((defined in [RFC6891]) contains the o OPTION-LENGTH, 2 octets ((defined in [RFC6891]) contains the
length of the payload (everything after OPTION-LENGTH) in octets length of the payload (everything after OPTION-LENGTH) in octets
and should be 4 plus the length of the EXTRA-TEXT section (which and should be 4 plus the length of the EXTRA-TEXT section (which
may be a zero-length string). may be a zero-length string).
o The RETRY flag, 1 bit; the RETRY bit (R) indicates a flag defined o The RETRY flag, 1 bit; the RETRY bit (R) indicates a flag defined
for use in this specification. for use in this specification.
o The RESERVED bits, 15 bits: these bits are reserved for future o The RESERVED bits, 15 bits: these bits are reserved for future
use, potentially as additional flags. The RESERVED bits MUST be use, potentially as additional flags. The RESERVED bits MUST be
set to 0 by the sender and SHOULD be ignored by the receiver. set to 0 by the sender and MUST be ignored by the receiver.
o RESPONSE-CODE, 4 bits. o RESPONSE-CODE, 4 bits.
o INFO-CODE, 12-bits. o INFO-CODE, 12-bits.
o EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may o EXTRA-TEXT, a variable length, UTF-8 encoded, text field that may
hold additional textual information. hold additional textual information.
3. Use of the Extended DNS Error option 3. Use of the Extended DNS Error option
The Extended DNS Error (EDE) is an EDNS option. It can be included The Extended DNS Error (EDE) is an EDNS option. It can be included
in any response (SERVFAIL, NXDOMAIN, REFUSED, etc) to a query that in any response (SERVFAIL, NXDOMAIN, REFUSED, etc) to a query that
includes an EDNS option. This document includes a set of initial includes OPT Pseudo-RR [RFC6891]. This document includes a set of
codepoints (and requests to the IANA to add them to the registry), initial codepoints (and requests to the IANA to add them to the
but is extensible via the IANA registry to allow additional error and registry), but is extensible via the IANA registry to allow
information codes to be defined in the future. additional error and information codes to be defined in the future.
The fields of the Extended DNS Error option are defined further in The fields of the Extended DNS Error option are defined further in
the following sub-sections. the following sub-sections.
3.1. The R (Retry) flag 3.1. The R (Retry) flag
The R (Retry) flag provides a hint as to what the receiver may want The R (Retry) flag provides a hint as to what the receiver may want
to do with this annotated error. Specifically, the R (or Retry) flag to do with this annotated error. Specifically, the R (or Retry) flag
provides a hint to the receiver that it should retry the query to provides a hint to the receiver that it should retry the query to
another server. If the R bit is set (1), the sender believes that another server. If the R bit is set (1), the sender believes that
retrying the query may provide a successful answer next time; if the retrying the query may provide a successful answer next time; if the
R bit is clear (0), the sender believes that the resolver should not R bit is clear (0), the sender believes that the resolver should not
ask another server. ask another server.
The mechanism is specifically designed to be extensible, and so The mechanism is specifically designed to be extensible, and so
implementations may receive EDE codes that it does not understand. implementations may receive EDE codes that it does not understand.
The R flag allows implementations to make a decision as to what to do The R flag allows implementations to make a decision as to what to do
if it receives a response with an unknown code - retry or drop the if it receives a response with an unknown code - retry or drop the
query. Note that this flag is only a suggestion. Unless a query. Note that this flag is only a suggestion. Unless a
protective transport mechanism (like TSIG [RFC2845] or TLS [RFC8094]) protective transport mechanism (like TSIG [RFC2845] or (D)TLS xref
is used, the bit's value could have have been altered by a person-in- target="RFC7858"/>, [RFC8094]) is used, the bit's value could have
the-middle. Receivers can choose to ignore this hint. See the have been altered by a person-in-the-middle. Receivers can choose to
security considerations for additional considerations. ignore this hint. See the security considerations for additional
considerations.
3.2. The RESPONSE-CODE field 3.2. The RESPONSE-CODE field
This 4-bit value SHOULD be a copy of the RCODE from the primary DNS This 4-bit value SHOULD be a copy of the RCODE from the primary DNS
packet. Multiple EDNS0/EDE records may be included in the response. packet. RESPONSE-CODEs MAY use a different RCODE to provide
When including multiple EDNS0/EDE records in a response in order to additional or better information. For example, multiple EDNS0/EDE
provide additional error information, other RESPONSE-CODEs MAY use a records may be included in the response and the supplemental EDNS0/
different RCODE. EDE records may wish to include other RESPONSE-CODE values based on
communication results with other DNS servers.
3.3. The INFO-CODE field 3.3. The INFO-CODE field
This 12-bit value provides the additional context for the RESPONSE- This 12-bit value provides the additional context for the RESPONSE-
CODE value. This combination of the RESPONSE-CODE and the INFO-CODE CODE value. This combination of the RESPONSE-CODE and the INFO-CODE
serve as a joint-index into the IANA "Extended DNS Errors" registry. serve as a joint-index into the IANA "Extended DNS Errors" registry.
Note to implementers: the combination of the RESPONSE-CODE and INFO-
CODE fits within a 16-bit field, allowing implementers the choice of
treating the combination as either two separate values, as defined in
this document, or as a single 16-bit integer as long as the results
are deterministic.
3.4. The EXTRA-TEXT field 3.4. The EXTRA-TEXT field
The UTF-8-encoded, EXTRA-TEXT field may be zero-length, or may hold The UTF-8-encoded, EXTRA-TEXT field may be zero-length, or may hold
additional information useful to network operators. additional information useful to network operators.
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 code-points can be
registered in the "Extended DNS Errors" registry. This document registered in the "Extended DNS Errors" registry. This document
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4.1.1. NOERROR Extended DNS Error Code 1 - Unsupported DNSKEY Algorithm 4.1.1. NOERROR 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 unknown algorithms. The R flag should be set. RRSET contained only unknown algorithms. The R flag should be set.
4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported DS Algorithm 4.1.2. NOERROR Extended DNS Error Code 2 - Unsupported DS Algorithm
The resolver attempted to perform DNSSEC validation, but a DS RRSET The resolver attempted to perform DNSSEC validation, but a DS RRSET
contained only unknown algorithms. The R flag should be set. contained only unknown algorithms. The R flag should be set.
4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2) 4.1.3. INFO-CODEs for use with RESPONSE-CODE: NOERROR(3)
4.1.3.1. NOERROR Extended DNS Error Code 3 - Stale Answer
4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus The resolver was unable to resolve answer within its time limits and
decided to answer with a previously cached data instead of answering
with an error. This is typically caused by problems on authoritative
side, possibly as result of a DoS attack. The R flag should not be
set, since retrying is likely to create additional load without
yielding a more fresh answer.
The resolver attempted to perform DNSSEC validation, but validation 4.1.4. NOERROR Extended DNS Error Code 4 - Forged answer
ended in the Bogus state. The R flag should not be set.
4.2.2. SERVFAIL Extended DNS Error Code 2 - DNSSEC Indeterminate For policy reasons (legal obligation, or malware filtering, for
instance), an answer was forged. The R flag should not be set.
4.1.5. SERVFAIL 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. The R flag should not be set. ended in the Indeterminate state. The R flag should not be set.
4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature Expired 4.2. INFO-CODEs for use with RESPONSE-CODE: SERVFAIL(2)
The resolver attempted to perform DNSSEC validation, but the 4.2.1. SERVFAIL Extended DNS Error Code 1 - DNSSEC Bogus
signature was expired. The R flag should not be set.
4.2.4. SERVFAIL Extended DNS Error Code 4 - Signature Not Yet Valid The resolver attempted to perform DNSSEC validation, but validation
ended in the Bogus state. The R flag should not be set.
4.2.2. SERVFAIL Extended DNS Error Code 2 - Signature Expired
The resolver attempted to perform DNSSEC validation, a signature in
the validation chain was expired. The R flag should not be set.
4.2.3. SERVFAIL Extended DNS Error Code 3 - Signature Not Yet Valid
The resolver attempted to perform DNSSEC validation, but the The resolver attempted to perform DNSSEC validation, but the
signatures received were not yet valid. The R flag should not be signatures received were not yet valid. The R flag should not be
set. set.
4.2.5. SERVFAIL Extended DNS Error Code 5 - DNSKEY missing 4.2.4. SERVFAIL Extended DNS Error Code 4 - DNSKEY missing
A DS record existed at a parent, but no DNSKEY record could be found A DS record existed at a parent, but no supported matching DNSKEY
for the child. The R flag should not be set. record could be found for the child. The R flag should not be set.
4.2.6. SERVFAIL Extended DNS Error Code 6 - RRSIGs missing 4.2.5. SERVFAIL Extended DNS Error Code 5 - RRSIGs missing
The resolver attempted to perform DNSSEC validation, but no RRSIGs The resolver attempted to perform DNSSEC validation, but no RRSIGs
could be found for at least one RRset where RRSIGs were expected. could be found for at least one RRset where RRSIGs were expected.
4.2.7. SERVFAIL Extended DNS Error Code 7 - No Zone Key Bit Set 4.2.6. SERVFAIL Extended DNS Error Code 6 - No Zone Key Bit Set
The resolver attempted to perform DNSSEC validation, but no Zone Key The resolver attempted to perform DNSSEC validation, but no Zone Key
Bit was set in a DNSKEY. Bit was set in a DNSKEY.
4.3. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5) 4.2.7. SERVFAIL Extended DNS Error Code 7 - No Reachable Authority
4.3.1. REFUSED Extended DNS Error Code 1 - Lame The resolver could not reach any of the authoritative name servers
(or they refused to reply). The R flag should be set.
An authoritative resolver that receives a query (with the RD bit 4.2.8. SERVFAIL Extended DNS Error Code 8 - NSEC Missing
clear) for a domain for which it is not authoritative SHOULD include
this EDE code in the REFUSED response. Implementations should set
the R flag in this case (another nameserver might not be lame).
4.3.2. REFUSED Extended DNS Error Code 2 - Prohibited The resolver attempted to perform DNSSEC validation, but the
requested data was missing and a covering NSEC or NSEC3 was not
provided. The R flag should be set.
4.2.9. SERVFAIL Extended DNS Error Code 9 - Cached Error
The resolver has cached SERVFAIL for this query without additional
information. Th R flag should be set.
4.2.10. SERVFAIL Extended DNS Error Code 10 - Not Ready
The server is unable to answer the query as it is not fully up and
functional yet.
4.3. INFO-CODEs for use with RESPONSE-CODE: NOTIMP(4)
4.3.1. NOTIMP Extended DNS Error Code 1 - Deprecated
The requested operation or query is not supported as its use has been
deprecated. Implementations should not set the R flag. (Retrying
request elsewhere is unlikely to yield any other results.)
4.4. INFO-CODEs for use with RESPONSE-CODE: REFUSED(5)
4.4.1. REFUSED Extended DNS Error Code 1 - 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. Implementations should set the R flag in this case
(another nameserver or resolver might not be lame).
4.4.2. REFUSED Extended DNS Error Code 2 - Prohibited
An authoritative or recursive resolver that receives a query from an An authoritative or recursive resolver that receives a query from an
"unauthorized" client can annotate its REFUSED message with this "unauthorized" client can annotate its REFUSED message with this
code. Examples of "unauthorized" clients are recursive queries from code. Examples of "unauthorized" clients are recursive queries from
IP addresses outside the network, blacklisted IP addresses, local IP addresses outside the network, blacklisted IP addresses, local
policy, etc. policy, etc.
Implementations SHOULD allow operators to define what to set the R Implementations SHOULD allow operators to define what to set the R
flag to in this case. flag to in this case.
4.4. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3) 4.5. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)
4.4.1. NXDOMAIN Extended DNS Error Code 1 - Blocked 4.5.1. NXDOMAIN Extended DNS Error Code 1 - Blocked
The resolver attempted to perfom a DNS query but the domain is The resolver attempted to perfom a DNS query but the domain is
blacklisted due to a security policy. The R flag should not be set. blacklisted due to a security policy implemented on the server being
directly talked to. The R flag should be set.
4.6. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)
4.6.1. NXDOMAIN Extended DNS Error Code 2 - 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 somehow, court order, etc). The R flag should be set.
4.7. INFO-CODEs for use with RESPONSE-CODE: NXDOMAIN(3)
4.7.1. NXDOMAIN Extended DNS Error Code 3 - Stale Answer
The resolver was unable to resolve answer within its time limits and
decided to answer with a previously cached NXDOMAIN answer instead of
answering with an error. This is typically caused by problems on
authoritative side, possibly as result of a DoS attack. The R flag
should not be set, since retrying is likely to create additional load
without yielding a more fresh answer.
5. IANA Considerations 5. IANA Considerations
5.1. new Extended Error Code EDNS Option 5.1. A New Extended 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 TBD1 from the "DNS EDNS0 Option Codes Error", assigned a value of TBD1 from the "DNS EDNS0 Option Codes
(OPT)" registry [to be removed upon publication: (OPT)" registry [to be removed upon publication:
[http://www.iana.org/assignments/dns-parameters/dns- [http://www.iana.org/assignments/dns-parameters/dns-
parameters.xhtml#dns-parameters-11] parameters.xhtml#dns-parameters-11]
Value Name Status Reference Value Name Status Reference
----- ---------------- ------ ------------------ ----- ---------------- ------ ------------------
TBD Extended DNS Error TBD [ This document ] TBD Extended DNS Error TBD [ This document ]
5.2. New Extended Error Code EDNS Option 5.2. New Double-Index Registry Table for Extended Error Codes
This document defines a new double-index IANA registry table, where This document defines a new double-index IANA registry table, where
the first index value is the RCODE value and the second index value the first index value is the RCODE value and the second index value
is the INFO-CODE from the Extended DNS Error EDNS option defined in is the INFO-CODE from the Extended DNS Error EDNS option defined in
this document. The IANA is requested to create and maintain this this document. The IANA is requested to create and maintain this
"Extended DNS Error codes" registry. The codepoint space for each "Extended DNS Error codes" registry. The codepoint space for each
INFO-CODE index is to be broken into 3 ranges: INFO-CODE index is to be broken into 3 ranges:
o 0 - 3583: Specification required. o 0 - 3583: Specification required.
o 3584 - 3839: First Come First Served. o 3584 - 3839: First Come First Served.
skipping to change at page 8, line 34 skipping to change at page 10, line 34
RESPONSE-CODE: 0 (NOERROR) RESPONSE-CODE: 0 (NOERROR)
INFO-CODE: 1 INFO-CODE: 1
Purpose: Unsupported DNSKEY Purpose: Unsupported DNSKEY
Reference: Section 4.1.1 Reference: Section 4.1.1
RESPONSE-CODE: 0 (NOERROR) RESPONSE-CODE: 0 (NOERROR)
INFO-CODE: 2 INFO-CODE: 2
Purpose: Unsupported DS Algorithm Purpose: Unsupported DS Algorithm
Reference: Section 4.1.2 Reference: Section 4.1.2
RESPONSE-CODE: 3 (NOERROR)
INFO-CODE: 3
Purpose: Answering with stale/cached data
Reference: Section 4.1.3.1
RESPONSE-CODE: 0 (NOERROR)
INFO-CODE: 4
Purpose: Forged answer
Reference: Section 4.1.4
RESPONSE-CODE: 0 (NOERROR)
INFO-CODE: 5
Purpose: DNSSEC Indeterminate
Reference: Section 4.1.5
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 1 INFO-CODE: 1
Purpose: DNSSEC Bogus Purpose: DNSSEC Bogus
Reference: Section 4.2.1 Reference: Section 4.2.1
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 2 INFO-CODE: 2
Purpose: DNSSEC Indeterminate Purpose: Signature Expired
Reference: Section 4.2.2 Reference: Section 4.2.2
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 3 INFO-CODE: 3
Purpose: Signature Expired Purpose: Signature Not Yet Valid
Reference: Section 4.2.3 Reference: Section 4.2.3
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 4 INFO-CODE: 4
Purpose: Signature Not Yet Valid Purpose: DNSKEY missing
Reference: Section 4.2.4 Reference: Section 4.2.4
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 5 INFO-CODE: 5
Purpose: DNSKEY missing Purpose: RRSIGs missing
Reference: Section 4.2.5 Reference: Section 4.2.5
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 6 INFO-CODE: 6
Purpose: RRSIGs missing Purpose: No Zone Key Bit Set
Reference: Section 4.2.6 Reference: Section 4.2.6
RESPONSE-CODE: 2 (SERVFAIL) RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 7 INFO-CODE: 7
Purpose: No Zone Key Bit Set Purpose: No NSEC records could be obtained
Reference: Section 4.2.7 Reference: Section 4.2.8
RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 9
Purpose: The SERVFAIL error comes from the cache
Reference: Section 4.2.9
RESPONSE-CODE: 2 (SERVFAIL)
INFO-CODE: 10
Purpose: Not Ready.
Reference: Section 4.2.10
RESPONSE-CODE: 3 (NXDOMAIN) RESPONSE-CODE: 3 (NXDOMAIN)
INFO-CODE: 1 INFO-CODE: 1
Purpose: Blocked Purpose: Blocked
Reference: Section 4.4.1 Reference: Section 4.5.1
RESPONSE-CODE: 3 (NXDOMAIN)
INFO-CODE: 2
Purpose: Censored
Reference: Section 4.6.1
RESPONSE-CODE: 3 (NXDOMAIN)
INFO-CODE: 3
Purpose: Answering with stale/cached NXDOMAIN data
Reference: Section 4.7.1
RESPONSE-CODE: 4 (NOTIMP)
INFO-CODE: 1
Purpose:
Reference: Section 4.4.2
RESPONSE-CODE: 5 (REFUSED) RESPONSE-CODE: 5 (REFUSED)
INFO-CODE: 1 INFO-CODE: 1
Purpose: Lame Purpose: Lame
Reference: Section 4.3.1 Reference: Section 4.4.1
RESPONSE-CODE: 5 (REFUSED) RESPONSE-CODE: 5 (REFUSED)
INFO-CODE: 2 INFO-CODE: 2
Purpose: Prohibited Purpose: Prohibited
Reference: Section 4.3.2 Reference: Section 4.4.2
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 validaion a SERVFAIL from a validating resolver because of a DNSSEC validaion
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 any of the protections which DNSSEC in their list, and thus don't get any of the protections which DNSSEC
should provide. This is very similar to a kid asking his mother if should provide. This is very similar to a kid asking his mother if
he can have another cookie. When the mother says "No, it will ruin he can have another cookie. When the mother says "No, it will ruin
skipping to change at page 10, line 15 skipping to change at page 13, line 7
mechanisms, there are some tradeoffs. As an example, an attacker who mechanisms, there are some tradeoffs. As an example, an attacker who
is able to insert the DNSSEC Bogus Extended Error into a packet could is able to insert the DNSSEC Bogus Extended Error into a packet could
instead simply reply with a fictitious address (A or AAAA) record. instead simply reply with a fictitious address (A or AAAA) record.
The R bit hint and extended error information are informational - The R bit hint and extended error information are informational -
implementations can choose how much to trust this information and implementations can choose how much to trust this information and
validating resolvers / stubs may choose to put a different weight on validating resolvers / stubs may choose to put a different weight on
it. it.
7. Acknowledgements 7. Acknowledgements
The authors wish to thank Joe Abley, Mark Andrews, Vladimir Cunat, The authors wish to thank Joe Abley, Mark Andrews, Stephane
Peter DeVries, Peter van Dijk, Donald Eastlake, Bob Harold, Evan Bortzmeyer, Vladimir Cunat, Peter DeVries, Peter van Dijk, Donald
Hunt, Geoff Huston, Shane Kerr, Edward Lewis, Carlos M. Martinez, Eastlake, Bob Harold, Evan Hunt, Geoff Huston, Shane Kerr, Edward
George Michelson, Petr Spacek, Ondrej Sury, Loganaden Velvindron, and Lewis, Carlos M. Martinez, George Michelson, Michael Sheldon, Petr
Paul Vixie. They also vaguely remember discussing this with a number Spacek, Ondrej Sury, Loganaden Velvindron, and Paul Vixie. They also
of people over the years, but have forgotten who all they were -- if vaguely remember discussing this with a number of people over the
you were one of them, and are not listed, please let us know and years, but have forgotten who all they were -- if you were one of
we'll acknowledge you. them, and are not listed, please let us know and we'll acknowledge
you.
I also want to thank the band "Infected Mushroom" for providing a I also want to thank the band "Infected Mushroom" for providing a
good background soundtrack (and to see if I can get away with this!) good background soundtrack (and to see if I can get away with this!)
Another author would like to thank the band "Mushroom Infectors". Another author would like to thank the band "Mushroom Infectors".
This was funny at the time we wrote it, but I cannot remember why... This was funny at the time we wrote it, but I cannot remember why...
8. References 8. References
8.1. Normative References 8.1. 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, <https://www.rfc- DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>. editor.org/info/rfc2119>.
[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>.
8.2. Informative References 8.2. Informative References
[GeoffValidation] [GeoffValidation]
IANA, "A quick review of DNSSEC Validation in today's IANA, "A quick review of DNSSEC Validation in today's
Internet", June 2016, <http://www.potaroo.net/ 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,
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