< draft-ietf-dnsop-extended-error-14.txt   draft-ietf-dnsop-extended-error-15.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 18, 2020 ISC Expires: October 26, 2020 ISC
R. Arends R. Arends
ICANN ICANN
W. Hardaker W. Hardaker
USC/ISI USC/ISI
D. Lawrence D. Lawrence
Oracle + Dyn Oracle + Dyn
January 15, 2020 April 24, 2020
Extended DNS Errors Extended DNS Errors
draft-ietf-dnsop-extended-error-14 draft-ietf-dnsop-extended-error-15
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.
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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 https://datatracker.ietf.org/drafts/current/. Drafts is at https://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 18, 2020. This Internet-Draft will expire on October 26, 2020.
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.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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4.18. Extended DNS Error Code 17 - Filtered . . . . . . . . . . 8 4.18. Extended DNS Error Code 17 - Filtered . . . . . . . . . . 8
4.19. Extended DNS Error Code 18 - Prohibited . . . . . . . . . 8 4.19. Extended DNS Error Code 18 - Prohibited . . . . . . . . . 8
4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer . . . 8 4.20. Extended DNS Error Code 19 - Stale NXDOMAIN Answer . . . 8
4.21. Extended DNS Error Code 20 - Not Authoritative . . . . . 8 4.21. Extended DNS Error Code 20 - Not Authoritative . . . . . 8
4.22. Extended DNS Error Code 21 - Not Supported . . . . . . . 8 4.22. Extended DNS Error Code 21 - Not Supported . . . . . . . 8
4.23. Extended DNS Error Code 22 - No Reachable Authority . . . 8 4.23. Extended DNS Error Code 22 - No Reachable Authority . . . 8
4.24. Extended DNS Error Code 23 - Network Error . . . . . . . 8 4.24. Extended DNS Error Code 23 - Network Error . . . . . . . 8
4.25. Extended DNS Error Code 24 - Invalid Data . . . . . . . . 9 4.25. Extended DNS Error Code 24 - Invalid Data . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
5.1. A New Extended DNS Error Code EDNS Option . . . . . . . . 9 5.1. A New Extended DNS Error Code EDNS Option . . . . . . . . 9
5.2. New Registry Table for Extended DNS Error Codes . . . . . 9 5.2. New Registry for Extended DNS Error Codes . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 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 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
because the nameserver is still starting up and loading zones? Is a because the nameserver is still starting up and loading zones? Is a
SERVFAIL a DNSSEC validation issue, or is the nameserver experiencing SERVFAIL a DNSSEC validation issue, or is the nameserver experiencing
some other failure? What error messages should be presented to the some other failure? What error messages should be presented to the
user or logged under these conditions? user or logged under these conditions?
A good example of issues that would benefit by 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 (using a stub resolver queries a name which 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 resolvers only to signal many sorts of DNS errors, and so the stub resolvers only
option is to ask the next configured DNS resolver. The result of 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 next resolver also validates, and a SERVFAIL is returned again; or the
resolver is not a validating resolver, and the user is returned a next resolver is not a validating resolver, and the user is returned
potentially harmful result. With an Extended DNS Error (EDE) option a potentially harmful result. With an Extended DNS Error (EDE)
enclosed in the response message, the resolver is able to return a option enclosed in the response message, the resolver is able to
more descriptive reason as to why any failures happened, or add return a more descriptive reason as to why any failures happened, or
additional context to a message containing a NOERROR RCODE. add 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. These extended
DNS error codes described in this document and can be used by any DNS error codes are described in this document and can be used by any
system that sends DNS queries and receives a response containing an 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 and thus different systems (stub resolvers, recursive resolvers, and
authoritative resolvers) might receive and use them. authoritative resolvers) might receive and use them.
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 in
responses from authoritative servers), so systems interpreting the 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. Applications all messages, including those with a NOERROR RCODE, but need not act
MUST continue to follow requirements from applicable specs on how to on them. Applications MUST continue to follow requirements from
process RCODEs no matter what EDE values is also received. Senders applicable specifications on how to process RCODEs no matter what EDE
MAY include more than one EDE option and receivers MUST be able to values are also received. Senders MAY include more than one EDE
accept (but not necessarily process or act on) multiple EDE options option and receivers MUST be able to accept (but not necessarily
in a DNS message. process or act on) multiple EDE options in a DNS message.
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", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
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 draft uses an EDNS0 ([RFC6891]) 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
follows: 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
+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+
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TBD. [RFC Editor: change TBD to the proper code once assigned by TBD. [RFC Editor: change TBD to the proper code once assigned by
IANA.] IANA.]
o OPTION-LENGTH, 2-octets/16-bits ((defined in [RFC6891]]) contains o OPTION-LENGTH, 2-octets/16-bits ((defined in [RFC6891]]) contains
the length of the payload (everything after OPTION-LENGTH) in the length of the payload (everything after OPTION-LENGTH) in
octets and should be 2 plus the length of the EXTRA-TEXT field octets and should be 2 plus the length of the EXTRA-TEXT field
(which may be a zero-length string). (which may be a zero-length string).
o INFO-CODE, 16-bits, which is the principal contribution of this o INFO-CODE, 16-bits, which is the principal contribution of this
document. This 16-bit value, encoded in network (MSB) byte order, document. This 16-bit value, encoded in network (MSB) byte order,
provides the additional context for the RESPONSE-CODE of the DNS provides the additional context for the RESPONSE-CODE of the DNS
message. The INFO-CODE serves as an index into the "Extended DNS message. The INFO-CODE serves as an index into the "Extended DNS
Errors" registry Section 5.1. Errors" registry defined and created in Section 5.2.
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. Note: EXTRA-TEXT may be zero hold additional textual information. This information is intended
octets in length, indicating there is no EXTRA-TEXT included. for human consumption (not automated parsing). The EXTRA-TEXT
Care should be taken not to leak private information that an field may be zero octets in length, indicating that there is no
observer would not otherwise have access to, such as account EXTRA-TEXT included. Care should be taken not to include private
numbers. 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, and even NOERROR, etc) to a query that
includes OPT Pseudo-RR [RFC6891]. This document includes a set of includes OPT Pseudo-RR [RFC6891]. This document includes a set of
initial codepoints (and requests to the IANA to add them to the initial codepoints, but is extensible via the IANA registry defined
registry), but is extensible via the IANA registry to allow and created in Section 5.2.
additional error and information codes to be defined in the future.
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. Long EXTRA-TEXT fields the truncation bit when dropping EDE options. Because long EXTRA-
may trigger truncation, which is usually undesirable for 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 setting unnecessarily long EXTRA-TEXT contents options SHOULD avoid lengthy EXTRA-TEXT contents.
to avoid truncation.
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 be field, since an EDNS0 option received by the original client will
perceived only to have come from the resolver or forwarder sending appear to have come from the resolver or forwarder sending it.
it.
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 Section 5.1. 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 sub-sections.
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 a 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 answer within its time limits and The resolver was unable to resolve the answer within its time limits
decided to answer with previously cached data instead of answering and decided to answer with previously cached data instead of
with an error. This is typically caused by problems communicating answering with an error. This is typically caused by problems
with an authoritative serever, possibly as result of a DoS attack communicating with an authoritative server, possibly as result of a
against another network. denial of service (DoS) attack against another network. (See also
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
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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 is not fully The server is unable to answer the query as it was not fully
functional (yet). 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 blacklisted due to an internal security policy imposed by the
operator of the server being directly talked to. 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 by a security policy imposed upon the server being talked blacklisted due to an external requirement imposed by an entity other
to by an external requirement. Note that how the imposed policy is than the operator of the server resolving or forwarding the query.
applied is irrelevant (in-band DNS filtering, court order, etc). Note that how the imposed policy is applied is irrelevant (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 blacklisted as requested by the client. Functionally, this amounts
to "you requested that we filter domains like this one." 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 or recursive resolver that receives a query from an An authoritative server or recursive resolver that receives a query
"unauthorized" client can annotate its REFUSED message with this from an "unauthorized" client can annotate its REFUSED message with
code. Examples of "unauthorized" clients are recursive queries from this code. Examples of "unauthorized" clients are recursive queries
IP addresses outside the network, blacklisted IP addresses, local from IP addresses outside the network, blacklisted IP addresses,
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 is may be caused, answer instead of answering with an error. This may be caused, for
for example, by problems communicating with an authoritative server, example, by problems communicating with an authoritative server,
possibly as result of a DoS attack against another network. possibly as result of a denial of service (DoS) attack against
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 RD bit clear,
or when not configured for recursion) for a domain for which it is or when it is not configured for recursion for a domain for which it
not authoritative SHOULD include this EDE code in the REFUSED is not authoritative SHOULD include this EDE code in the REFUSED
response. A resolver that receives a query (with the RD bit clear) response. A resolver that receives a query with the RD bit clear
SHOULD include this EDE code in the REFUSED response. 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 as its use has been The requested operation or query is not supported.
deprecated.
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 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
An authoritative server that 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. This may occur because its most otherwise configured to support. Examples of this include its most
recent zone is too old, or has expired, for example. 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", assigned a value of TBD 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 Standard [ This document ]
5.2. New Registry Table for Extended DNS Error Codes 5.2. New Registry for Extended DNS Error Codes
This document defines a new IANA registry table, where the index IANA is requested to create and maintain a new registry table called
value is the INFO-CODE from the "Extended DNS Error" EDNS option "Extended DNS Error Codes" on the "Domain Name System (DNS)
defined in this document. The IANA is requested to create and Parameters" web page as follows:
maintain this "Extended DNS Error" codes registry. The code-point
space for the INFO-CODE index is to be broken into 2 ranges: Registry Name: Extended DNS Error Codes
Registration Procedures:
o 0 - 49151: First come, first served. o 0 - 49151: First come, first served.
o 49152 - 65280: Private use. o 49152 - 65280: Private use.
A starting set of entries, based on the contents of this document, is Reference: [this document]
as follows:
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 INFO-CODE: 0
Purpose: Other Error Purpose: Other Error
Reference: Section 4.1 Reference: Section 4.1
INFO-CODE: 1 INFO-CODE: 1
Purpose: Unsupported DNSKEY Algorithm Purpose: Unsupported DNSKEY Algorithm
Reference: Section 4.2 Reference: Section 4.2
INFO-CODE: 2 INFO-CODE: 2
Purpose: Unsupported DS Digest Type Purpose: Unsupported DS Digest Type
Reference: Section 4.3 Reference: Section 4.3
INFO-CODE: 3 INFO-CODE: 3
Purpose: Stale Answer Purpose: Stale Answer
Reference: Section 4.4, [I-D.ietf-dnsop-serve-stale] Reference: Section 4.4, [RFC8767]
INFO-CODE: 4 INFO-CODE: 4
Purpose: Forged Answer Purpose: Forged Answer
Reference: Section 4.5 Reference: Section 4.5
INFO-CODE: 5 INFO-CODE: 5
Purpose: DNSSEC Indeterminate Purpose: DNSSEC Indeterminate
Reference: Section 4.6 Reference: Section 4.6
INFO-CODE: 6 INFO-CODE: 6
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Reference: Section 4.23 Reference: Section 4.23
INFO-CODE: 23 INFO-CODE: 23
Purpose: Network Error Purpose: Network Error
Reference: Section 4.24 Reference: Section 4.24
INFO-CODE: 24 INFO-CODE: 24
Purpose: Invalid Data Purpose: Invalid Data
Reference: Section 4.25 Reference: Section 4.25
INFO-CODE: 25-65535
Purpose: Unasigned
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 validaion 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 any of the protections which DNSSEC in their list, and thus don't get the protections which DNSSEC should
should provide. provide.
This information is unauthenticated information, and an attacker (e.g EDE information is unauthenticated information, unless secured by a
a MITM or malicious recursive server) could insert an extended error form of secured DNS transaction such as [RFC2845], [RFC2931] or
response into already untrusted data -- ideally clients and resolvers [RFC8094]. An attacker (e.g a MITM or malicious recursive server)
would not trust any unauthenticated information, but until we live in could insert an extended error response into untrusted data --
an era where all DNS answers are authenticated via DNSSEC or other although ideally clients and resolvers would not trust any
mechanisms [RFC2845] [RFC8094], there are some tradeoffs. As an unauthenticated information. As such, EDE content should be treated
example, an attacker who is able to insert the DNSSEC Bogus Extended only as diagnostic information and MUST NOT alter DNS protocol
Error into a packet could instead simply reply with a fictitious processing. Until all DNS answers are authenticated via DNSSEC or
address (A or AAAA) record. Note that DNS Response Codes also the other mechanisms mentioned above, there are some tradeoffs. As
contain no authentication and can be just as easily manipulated. an example, an attacker who is able to insert the DNSSEC Bogus
Extended Error into a DNS message could instead simply reply with a
fictitious address (A or AAAA) record. Note that DNS Response Codes
(RCODEs) also contain no authentication and can be just as easily
manipulated.
By design, EDE potentially exposes additional information DNS
resolution processes that may leak information. An example of this
is the Prohibited EDE code (18), which may leak the fact that the
name is on a blacklist.
7. Acknowledgements 7. Acknowledgements
The authors wish to thank Joe Abley, Mark Andrews, Tim April, The authors wish to thank Joe Abley, Mark Andrews, Tim April,
Vittorio Bertola, Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans, Vittorio Bertola, Stephane Bortzmeyer, Vladimir Cunat, Ralph Dolmans,
Peter DeVries, Peter van Dijk, Mats Dufberg, Donald Eastlake, Bob Peter DeVries, Peter van Dijk, Mats Dufberg, Donald Eastlake, Bob
Harold, Paul Hoffman, Geoff Huston, Shane Kerr, Edward Lewis, Carlos Harold, Paul Hoffman, Geoff Huston, Shane Kerr, Edward Lewis, Carlos
M. Martinez, George Michelson, Eric Orth, Michael Sheldon, Puneet M. Martinez, George Michelson, Eric Orth, Michael Sheldon, Puneet
Sood, Petr Spacek, Ondrej Sury, John Todd, Loganaden Velvindron, and Sood, Petr Spacek, Ondrej Sury, John Todd, Loganaden Velvindron, and
Paul Vixie. They also vaguely remember discussing this with a number Paul Vixie. They also vaguely remember discussing this with a number
of people over the years, but have forgotten who all they were -- if 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 you were one of them, and are not listed, please let us know and
we'll acknowledge you. we'll acknowledge you.
One author also wants to thank the band "Infected Mushroom" for One author also wants to thank the band "Infected Mushroom" for
providing a good background soundtrack (and to see if he can get away 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 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 "Mushroom Infectors". This was funny at the time we wrote it, but we
cannot remember why... cannot remember why...
8. References 8. References
8.1. Normative References 8.1. 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-10 (work in progress), December 2019.
[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>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, for DNS (EDNS(0))", STD 75, RFC 6891,
DOI 10.17487/RFC6891, April 2013, DOI 10.17487/RFC6891, April 2013,
<https://www.rfc-editor.org/info/rfc6891>. <https://www.rfc-editor.org/info/rfc6891>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8499] Hoffman, P., Sullivan, A., and K. Fujiwara, "DNS
Terminology", BCP 219, RFC 8499, DOI 10.17487/RFC8499,
January 2019, <https://www.rfc-editor.org/info/rfc8499>.
[RFC8767] Lawrence, D., Kumari, W., and P. Sood, "Serving Stale Data
to Improve DNS Resiliency", RFC 8767,
DOI 10.17487/RFC8767, March 2020,
<https://www.rfc-editor.org/info/rfc8767>.
8.2. Informative References 8.2. Informative References
[GeoffValidation] [GeoffValidation]
APNIC, G. H., "A quick review of DNSSEC Validation in APNIC, G. H., "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
( SIG(0)s )", RFC 2931, DOI 10.17487/RFC2931, September
2000, <https://www.rfc-editor.org/info/rfc2931>.
[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>.
Authors' Addresses Authors' Addresses
Warren Kumari Warren Kumari
Google Google
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
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