Structured Error Data for Filtered DNS
draft-ietf-dnsop-structured-dns-error-08
| Document | Type | Active Internet-Draft (dnsop WG) | |
|---|---|---|---|
| Authors | Dan Wing , Tirumaleswar Reddy.K , Neil Cook , Mohamed Boucadair | ||
| Last updated | 2024-01-31 | ||
| Replaces | draft-wing-dnsop-structured-dns-error-page | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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draft-ietf-dnsop-structured-dns-error-08
DNS Operations Working Group D. Wing
Internet-Draft Citrix
Updates: 8914 (if approved) T. Reddy
Intended status: Standards Track Nokia
Expires: 4 August 2024 N. Cook
Open-Xchange
M. Boucadair
Orange
1 February 2024
Structured Error Data for Filtered DNS
draft-ietf-dnsop-structured-dns-error-08
Abstract
DNS filtering is widely deployed for various reasons, including
network security. However, filtered DNS responses lack structured
information for end users to understand the reason for the filtering.
Existing mechanisms to provide explanatory details to end users cause
harm especially if the blocked DNS response is for HTTPS resources.
This document updates RFC 8914 by signaling client support for
structuring the EXTRA-TEXT field of the Extended DNS Error to provide
details on the DNS filtering. Such details can be parsed by the
client and displayed, logged, or used for other purposes.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://ietf-wg-
dnsop.github.io/draft-ietf-dnsop-structured-dns-error/draft-ietf-
dnsop-structured-dns-error.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-ietf-
dnsop-structured-dns-error/.
Discussion of this document takes place on the dnsop Working Group
mailing list (mailto:dnsop@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/dnsop/. Subscribe at
https://www.ietf.org/mailman/listinfo/dnsop/.
Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-dnsop/draft-ietf-dnsop-structured-dns-
error.
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
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This Internet-Draft will expire on 4 August 2024.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
license-info) in effect on the date of publication of this document.
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document. Code Components
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. DNS Filtering Techniques and Their Limitations . . . . . . . 5
4. I-JSON in EXTRA-TEXT Field . . . . . . . . . . . . . . . . . 6
5. Protocol Operation . . . . . . . . . . . . . . . . . . . . . 8
5.1. Client Generating Request . . . . . . . . . . . . . . . . 8
5.2. Server Generating Response . . . . . . . . . . . . . . . 8
5.3. Client Processing Response . . . . . . . . . . . . . . . 9
6. New Sub-Error Codes Definition . . . . . . . . . . . . . . . 11
6.1. Reserved . . . . . . . . . . . . . . . . . . . . . . . . 11
6.2. Network Operator Policy . . . . . . . . . . . . . . . . . 11
6.3. DNS Operator Policy . . . . . . . . . . . . . . . . . . . 11
7. Extended DNS Error Code TBA1 - Blocked by Upstream DNS
Server . . . . . . . . . . . . . . . . . . . . . . . . . 12
8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 12
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9. Security Considerations . . . . . . . . . . . . . . . . . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10.1. Media Type Registration . . . . . . . . . . . . . . . . 14
10.2. New Registry for JSON Names . . . . . . . . . . . . . . 15
10.3. New Registry for Contact URI Scheme . . . . . . . . . . 16
10.4. New Registry for DNS SubError Codes . . . . . . . . . . 17
10.5. New Extended DNS Error Code . . . . . . . . . . . . . . 19
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
11.1. Normative References . . . . . . . . . . . . . . . . . . 19
11.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Interoperation with RPZ Servers . . . . . . . . . . 22
Appendix B. Implementation Status . . . . . . . . . . . . . . . 22
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23
1. Introduction
DNS filters are deployed for a variety of reasons, e.g., endpoint
security, parental filtering, and filtering required by law
enforcement. Network-based security solutions such as firewalls and
Intrusion Prevention Systems (IPS) rely upon network traffic
inspection to implement perimeter-based security policies and operate
by filtering DNS responses. In a home network, DNS filtering is used
for the same reasons as above and additionally for parental control.
Internet Service Providers (ISPs) typically block access to some DNS
domains due to a requirement imposed by an external entity (e.g., law
enforcement agency) also performed using DNS-based content filtering.
Users of DNS services that perform filtering may wish to receive more
explanatory information about such a filtering to resolve problems
with the filter -- for example to contact the administrator to
allowlist a DNS domain that was erroneously filtered or to understand
the reason a particular domain was filtered. With that information,
a user can choose to use another network, open a trouble ticket with
the DNS administrator to resolve erroneous filtering, log the
information, etc.
For the DNS filtering mechanisms described in Section 3, the DNS
server can return extended error codes Blocked, Filtered, or Forged
Answer defined in Section 4 of [RFC8914]. However, these codes only
explain that filtering occurred but lack detail for the user to
diagnose erroneous filterings.
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No matter which type of response is generated (forged IP address(es),
NXDOMAIN or empty answer, even with an extended error code), the user
who triggered the DNS query has little chance to understand which
entity filtered the query, how to report a mistake in the filter, or
why the entity filtered it at all. This document describes a
mechanism to provide such detail.
One of the other benefits of the approach described in this document
is to eliminate the need to "spoof" block pages for HTTPS resources.
This is achieved since clients implementing this approach would be
able to display a meaningful error message, and would not need to
connect to such a block page. This approach thus avoids the need to
install a local root certificate authority on those IT-managed
devices.
This document describes a format for computer-parsable data in the
EXTRA-TEXT field of [RFC8914]. It updates Section 2 of [RFC8914]
which says the information in EXTRA-TEXT field is intended for human
consumption (not automated parsing).
This document does not recommend DNS filtering but provides a
mechanism for better transparency to explain to the users why some
DNS queries are filtered.
2. Conventions and Definitions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"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.
This document uses terms defined in DNS Terminology [RFC8499].
"Requestor" refers to the side that sends a request. "Responder"
refers to an authoritative, recursive resolver or other DNS component
that responds to questions.
"Encrypted DNS" refers to any encrypted scheme to convey DNS
messages, for example, DNS-over-HTTPS [RFC8484], DNS-over-TLS
[RFC7858], or DNS-over-QUIC [RFC9250].
The document refers to an Extended DNS Error (EDE) using its purpose,
not its INFO-CODE as per Table 3 of [RFC8914]. "Forged Answer",
"Blocked", and "Filtered" are thus used to refer to "Forged Answer
(4)", "Blocked (15)", and "Filtered (17)".
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3. DNS Filtering Techniques and Their Limitations
DNS responses can be filtered by sending, e.g., a bogus (also called
"forged") response, NXDOMAIN error, or empty answer. Also, clients
can be informed that filtering has occured by sending an Extended DNS
Error code defined in [RFC8914]. Each of these methods have
advantages and disadvantages that are discussed below:
1. The DNS response is forged to provide a list of IP addresses that
points to an HTTP(S) server alerting the end user about the
reason for blocking access to the requested domain (e.g.,
malware). When an HTTP(S) enabled domain name is blocked, the
network security device (e.g., Customer Premises Equipment (CPE)
or firewall) presents a block page instead of the HTTP response
from the content provider hosting that domain. If an HTTP
enabled domain name is blocked, the network security device
intercepts the HTTP request and returns a block page over HTTP.
If an HTTPS enabled domain is blocked, the block page is also
served over HTTPS. In order to return a block page over HTTPS,
man in the middle (MITM) is enabled on endpoints by generating a
local root certificate and an accompanying (local) public/private
key pair. The local root certificate is installed on the
endpoint while the network security device stores a copy of the
private key. During the TLS handshake, the on-path network
security device modifies the certificate provided by the server
and (re)signs it using the private key from the local root
certificate.
* However, configuring the local root certificate on endpoints
is not a viable option in several deployments like home
networks, schools, Small Office/Home Office (SOHO), or Small/
Medium Enterprise (SME). In these cases, the typical behavior
is that the filtered DNS response points to a server that will
display the block page. If the client is using HTTPS (via a
web browser or another application) this results in a
certificate validation error which gives no information to the
end-user about the reason for the DNS filtering.
* Enterprise networks do not assume that all the connected
devices are managed by the IT team or Mobile Device Management
(MDM) devices, especially in the quite common Bring Your Own
Device (BYOD) scenario. In addition, the local root
certificate cannot be installed on IoT devices without a
device management tool.
* An end user does not know why the connection was prevented
and, consequently, may repeatedly try to reach the domain but
with no success. Frustrated, the end user may switch to an
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alternate network that offers no DNS filtering against malware
and phishing, potentially compromising both security and
privacy. Furthermore, certificate errors train users to click
through certificate errors, which is a bad security practice.
To eliminate the need for an end user to click through
certificate errors, an end user may manually install a local
root certificate on a host device. Doing so, however, is also
a bad security practice as it creates a security vulnerability
that may be exploited by a MITM attack. When a manually
installed local root certificate expires, the user has to
(again) manually install the new local root certificate.
2. The DNS response is forged to provide a NXDOMAIN response to
cause the DNS lookup to terminate in failure. In this case, an
end user does not know why the domain cannot be reached and may
repeatedly try to reach the domain but with no success.
Frustrated, the end user may use insecure connections to reach
the domain, potentially compromising both security and privacy.
3. The extended error codes Blocked and Filtered defined in
Section 4 of [RFC8914] can be returned by a DNS server to provide
additional information about the cause of a DNS error.
4. These extended error codes do not suffer from the limitations
discussed in bullets (1) and (2), but the user still does not
know the exact reason nor is aware of the exact entity blocking
the access to the domain. For example, a DNS server may block
access to a domain based on the content category such as
"Malware" to protect the endpoint from malicious software,
"Phishing" to prevent the user from revealing sensitive
information to the attacker, etc. A user may need to know the
contact details of the IT/InfoSec team to raise a complaint.
4. I-JSON in EXTRA-TEXT Field
DNS servers that are compliant with this specification and have
received an indication that the client also supports this
specification as per Section 5.1 send data in the EXTRA-TEXT field
[RFC8914] encoded using the Internet JSON (I-JSON) message format
[RFC7493].
Note that [RFC7493] was based on [RFC7159], but [RFC7159] was
replaced by [RFC8259].
This document defines the following JSON names:
c: (contact) The contact details of the IT/InfoSec team to report
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mis-classified DNS filtering. This information is important for
transparency and also to ease unblocking a legitimate domain name
that got blocked due to wrong classification.
This field is structured as an array of contact URIs, using 'tel'
[RFC3966] or 'sips' [RFC5630] or 'mailto' [RFC3966] schemes. At
least one contact URI MUST be included.
New contact URI schemes may be added to the IANA registry
following the instructions in Section 10.3.
This field is mandatory.
j: (justification) 'UTF-8'-encoded [RFC5198] textual justification
for this particular DNS filtering. The field should be treated
only as diagnostic information for IT staff.
Whether the information provided in the "j" name is meaningful or
considered as garbage data (including empty values) is local to
each IT teams. Returning garbage data would indicate that a DNS
server is misbehaving. Note also that the provided justification
is useful for cross-validation with another DNS server.
This field is mandatory.
s: (suberror) The suberror code for this particular DNS filtering.
This field is optional.
o: (organization) 'UTF-8'-encoded human-friendly name of the
organization that filtered this particular DNS query.
This field is optional.
New JSON names can be defined in the IANA registry introduced in
Section 10.2. Such names MUST consist only of lower-case ASCII
characters, digits, and hyphen-minus (that is, Unicode characters
U+0061 through 007A, U+0030 through U+0039, and U+002D). Also, these
names MUST be 63 characters or shorter and it is RECOMMENDED they be
as short as possible.
The text in the "j" and "o" names can include international
characters. If the text is displayed in a language not known to the
end user, browser extensions to translate to user's native language
can be used.
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To reduce DNS message size the generated JSON SHOULD be as short as
possible: short domain names, concise text in the values for the "j"
and "o" names, and minified JSON (that is, without spaces or line
breaks between JSON elements).
The JSON data can be parsed to display to the user, logged, or
otherwise used to assist the end-user or IT staff with
troubleshooting and diagnosing the cause of the DNS filtering.
An alternate design for conveying the suberror would be to define
new EDE codes for these errors. However, such design is
suboptimal because it requires replicating an error code for each
EDE code to which the suberror applies (e.g., "Malware" suberror
in Table 3 would consume three EDE codes).
5. Protocol Operation
5.1. Client Generating Request
When generating a DNS query the client includes the EDE option
(Section 2 of [RFC8914]) in the OPT pseudo-RR [RFC6891] to elicit the
EDE option in the DNS response. It MUST use an OPTION-LENGTH of 2,
the INFO-CODE field set to "0" (Other Error), and an empty EXTRA-TEXT
field. This signal indicates that the client desires that the server
responds in accordance with the present specification.
5.2. Server Generating Response
When the DNS server filters its DNS response to a query (e.g., A or
AAAA record query), the DNS response MAY contain an empty answer,
NXDOMAIN, or (less ideally) forged response, as desired by the DNS
server. In addition, if the query contained the OPT pseudo-RR the
DNS server MAY return more detail in the EXTRA-TEXT field as
described in Section 5.3.
Servers may decide to return small TTL values in filtered DNS
responses (e.g., 2 seconds) to handle domain category and reputation
updates.
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Because the DNS client signals its EDE support (Section 5.1) and
because EDE support is signaled via a non-cached OPT resource record
(Section 6.2.1 of [RFC6891]) the EDE-aware DNS server can tailor its
filtered response to be most appropriate to that client's EDE
support. If EDE support is signaled in the query as per Section 5.1,
the server MUST NOT return the "Forged Answer" extended error code
because the client can take advantage of EDE's more sophisticated
error reporting (e.g., "Filtered", "Blocked"). Continuing to send
"Forged Answer" even to an EDE-supporting client will cause the
persistence of the drawbacks described in Section 3.
5.3. Client Processing Response
On receipt of a DNS response with an EDE option from a DNS responder,
the following ordered actions are performed on the EXTRA-TEXT field:
* Servers which don't support this specification might use plain
text in the EXTRA-TEXT field. Requestors SHOULD properly handle
both plaintext and JSON text in the EXTRA-TEXT field. The
requestor verifies that the field contains valid JSON. If not,
the requestor MUST consider the server does not support this
specification and stop processing rest of the actions defined in
this section, but may instead choose to treat EXTRA-TEXT as per
[RFC8914].
* The response MUST be received over an encrypted DNS channel. If
not, the requestor MUST discard data in the EXTRA-TEXT field.
* The DNS response MUST also contain an extended error code of
"Blocked by Upstream Server", "Blocked" or "Filtered" [RFC8914],
otherwise the EXTRA-TEXT field is discarded.
* If either of the mandatory JSON names "c" and "j" are missing or
have empty values in the EXTRA-TEXT field, the entire JSON is
discarded.
* If the "c" field contains any URI scheme not registered in the
Section 10.3 registry, it MUST be discarded.
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* If a DNS client has enabled opportunistic privacy profile
(Section 5 of [RFC8310]) for DoT, the DNS client will either fall
back to an encrypted connection without authenticating the DNS
server provided by the local network or fall back to clear text
DNS, and cannot exchange encrypted DNS messages. Both of these
fallback mechanisms adversely impact security and privacy. If the
DNS client has enabled opportunistic privacy profile for DoT and
the identity of the DNS server cannot be verified but the
connection is encrypted, the DNS client MUST ignore the "c", "j",
and "o" fields but MAY process the "s" field and other parts of
the response.
* Opportunistic discovery [I-D.ietf-add-ddr], where only the IP
address is validated, the DNS client MUST ignore the "c", "j", and
"o" fields but MAY process the "s" field and other parts of the
response.
* If a DNS client has enabled strict privacy profile (Section 5 of
[RFC8310]) for DoT, the DNS client requires an encrypted
connection and successful authentication of the DNS server. In
doing so, this mitigates both passive eavesdropping and client
redirection (at the expense of providing no DNS service if an
encrypted, authenticated connection is not available). If the DNS
client has enabled strict privacy profile for DoT, the DNS client
MAY process the EXTRA-TEXT field of the DNS response.
* The DNS client MUST ignore any other JSON names that it does not
support.
* When a forwarder receives an EDE option, whether or not (and how)
to pass along JSON information in the EXTRA-TEXT on to their
client is implementation dependent [RFC5625]. Implementations MAY
choose to not forward the JSON information, or they MAY choose to
create a new EDE option that conveys the information in the "c",
"s", and "j" fields encoded in the JSON object.
* The application that triggered the DNS request may have a local
policy to override the contact information (e.g., redirect all
complaint calls to a single contact point). In such a case, the
content of the "c" attribute can be ignored.
Note that the strict and opportunistic privacy profiles as defined
in [RFC8310] only apply to DoT; there has been no such distinction
made for DoH.
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6. New Sub-Error Codes Definition
The document defines the following new IANA-registered Sub-Error
codes.
6.1. Reserved
* Number: 0
* Meaning: Reserved. This sub-error code value MUST NOT be sent.
If received, it has no meaning.
* Applicability: This code should never be used.
* Reference: This-Document
* Change Controller: IETF
6.2. Network Operator Policy
* Number: 5
* Meaning: Network Operator Policy. The code indicates that the
request was filtered according to a policy imposed by the operator
of the local network (where local network is a relative term,
e.g., it may refer to a Local Area Network or to the network of
the ISP selected by the user).
* Applicability: Blocked
* Reference: This-Document
* Change Controller: IETF
6.3. DNS Operator Policy
* Number: 6
* Meaning: DNS Operator Policy. The code indicates that the request
was filtered according to policy determined by the operator of the
DNS server. This is different from the "Network Operator Policy"
code when a third-party DNS resolver is used.
* Applicability: Blocked
* Reference: This-Document
* Change Controller: IETF
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7. Extended DNS Error Code TBA1 - Blocked by Upstream DNS Server
The DNS server (e.g., a DNS forwarder) is unable to respond to the
request because the domain is on a blocklist due to an internal
security policy imposed by an upstream DNS server. This error code
is useful in deployments where a network-provided DNS forwarder is
configured to use an external resolver that filters malicious
domains. Typically, when the DNS forwarder receives a Blocked (15)
error code from the upstream DNS server, it will replace it with
"Blocked by Upstream DNS Server" (TBA1) before forwarding the reply
to the DNS client.
8. Examples
An example showing the nameserver at 'ns.example.net' that filtered a
DNS "A" record query for 'example.org' is provided in Figure 1.
{
"c": [
"tel:+358-555-1234567",
"sips:bob@bobphone.example.com"
],
"j": "malware present for 23 days",
"s": 1,
"o": "example.net Filtering Service"
}
Figure 1: JSON Returned in EXTRA-TEXT Field of Extended DNS Error
Response
In Figure 2 the same content is shown with minified JSON (no
whitespace, no blank lines) with '\' line wrapping per [RFC8792].
=============== NOTE: '\' line wrapping per RFC 8792 ===============
{"c":["tel:+358-555-1234567","sips:bob@bobphone.example.com","https\
://ticket.example.com?d=example.org&t=1650560748"],"j":"malware \
present for 23 days","s":1,"o":"example.net Filtering Service"}
Figure 2: Minified Response
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9. Security Considerations
Security considerations in Section 6 of [RFC8914] apply to this
document, except the guard against using EDE content to alter DNS
protocol processing. The guard is relaxed in the current
specification as it mandates encryption and recommends the use of an
authenticated connection to the DNS server, while [RFC8914] assumes
that EDE information is unauthenticated and sent over clear text.
To minimize impact of active on-path attacks on the DNS channel, the
client validates the response as described in Section 5.3.
A client might choose to display the information in the "c", "j", and
"o" fields if and only if the encrypted resolver has sufficient
reputation, according to some local policy (e.g., user configuration,
administrative configuration, or a built-in list of respectable
resolvers). This limits the ability of a malicious encrypted
resolver to cause harm. For example, an end user can use the details
in the "c" field to contact an attacker to solve the problem of being
unable to reach a domain. The attacker can mislead the end user to
install malware or spyware to compromise the device security posture
or mislead the end user to reveal personal data. If the client
decides not to display all of the information in the EXTRA-TEXT
field, it can be logged for diagnostics purpose and the client can
only display the resolver hostname that blocked the domain, error
description for the EDE code and the suberror description for the "s"
field to the end-user.
When displaying the free-form text of "j" and "o", the browser MUST
NOT make any of those elements into actionable (clickable) links and
these fields need to be rendered as text, not as HTML. The contact
details of "c" can be made into clickable links to provide a
convenient way for users to initiate, e.g., voice calls. The client
might choose to display the contact details only when the identity of
the DNS server is verified.
An attacker might inject (or modify) the EDE EXTRA-TEXT field with a
DNS proxy or DNS forwarder that is unaware of EDE. Such a DNS proxy
or DNS forwarder will forward that attacker-controlled EDE option.
To prevent such an attack, clients can be configured to process EDE
from explicitly configured DNS servers or utilize RESINFO
[I-D.ietf-add-resolver-info].
10. IANA Considerations
This document requests four IANA actions as described in the
following subsections.
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Note to the RFC Editor: Please replace RFCXXXX with the RFC number
assigned to this document and "TBA1" with the value assigned by
IANA.
10.1. Media Type Registration
This document requests IANA to register the "application/
json+structured-dns-error" media type in the "Media Types" registry
[IANA-MediaTypes]. This registration follows the procedures
specified in [RFC6838]:
Type name: application
Subtype name: json+structured-dns-error
Required parameters: N/A
Optional parameters: N/A
Encoding considerations: as defined in Section 4 of RFCXXXX.
Security considerations: See Section 10 of RFCXXXX.
Interoperability considerations: N/A
Published specification: RFCXXXX
Applications that use this media type: Section 4 of RFCXXXX.
Fragment identifier considerations: N/A
Additional information: N/A
Person & email address to contact for further information: IETF,
iesg@ietf.org
Intended usage: COMMON
Restrictions on usage: none
Author: See Authors' Addresses section.
Change controller: IESG
Provisional registration? No
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10.2. New Registry for JSON Names
This document requests IANA to create a new registry, entitled
"EXTRA-TEXT JSON Names" under "Domain Name System (DNS) Parameters,
Extended DNS Error Codes" registry [IANA-DNS]. The registration
request for a new JSON name must include the following fields:
JSON Name: Specifies the name of an attribute that is present in the
JSON data enclosed in EXTRA-TEXT field. The name must follow the
guidelines in Section 4.
Short description: Includes a short description of the requested
JSON name.
Mandatory (Y/N?): Indicates whether this attribute is mandatory or
optional.
Specification: Provides a pointer to the reference document that
specifies the attribute.
The registry is initially populated with the following values:
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+====+===============+==================+===========+===============+
|JSON| Full JSON | Description | Mandatory | Specification |
|Name| Name | | | |
+====+===============+==================+===========+===============+
| c | contact | The contact | Y | Section 4 of |
| | | details of the | | RFCXXXX |
| | | IT/InfoSec team | | |
| | | to report mis- | | |
| | | classified DNS | | |
| | | filtering | | |
+----+---------------+------------------+-----------+---------------+
| j | justification | UTF-8-encoded | Y | Section 4 of |
| | | [RFC5198] | | RFCXXXX |
| | | textual | | |
| | | justification | | |
| | | for a | | |
| | | particular DNS | | |
| | | filtering | | |
+----+---------------+------------------+-----------+---------------+
| s | suberror | the suberror | N | Section 4 of |
| | | code for this | | RFCXXXX |
| | | particular DNS | | |
| | | filtering | | |
+----+---------------+------------------+-----------+---------------+
| o | organization | UTF-8-encoded | N | Section 4 of |
| | | human-friendly | | RFCXXXX |
| | | name of the | | |
| | | organization | | |
| | | that filtered | | |
| | | this particular | | |
| | | DNS query | | |
+----+---------------+------------------+-----------+---------------+
Table 1: Initial JSON Names Registry
New JSON names are registered via IETF Review (Section 4.8 of
[RFC8126]).
10.3. New Registry for Contact URI Scheme
This document requests IANA to create a new registry, entitled
"Contact URI Schemes" under "Domain Name System (DNS) Parameters,
Extended DNS Error Codes" registry [IANA-DNS]. The registration
request for a new Contact URI scheme has to include the following
fields:
* Name: URI scheme name.
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* Meaning: Provides a short description of the scheme.
* Reference: Provides a pointer to an IETF-approved specification
that defines the URI scheme.
* Change Controller: Indicates the person or entity, with contact
information if appropriate.
The Contact URI scheme registry is initially be populated with the
following schemes:
+========+==================+===========+===================+
| Name | Meaning | Reference | Change Controller |
+========+==================+===========+===================+
| sips | SIP Call | [RFC5630] | IETF |
+--------+------------------+-----------+-------------------+
| tel | Telephone Number | [RFC3966] | IETF |
+--------+------------------+-----------+-------------------+
| mailto | Internet mail | [RFC6068] | IETF |
+--------+------------------+-----------+-------------------+
Table 2
New Contact URI schemes are registered via IETF Review (Section 4.8
of [RFC8126]).
10.4. New Registry for DNS SubError Codes
This document requests IANA to create a new registry, entitled
"SubError Codes" under "Domain Name System (DNS) Parameters, Extended
DNS Error Codes" registry [IANA-DNS]. The registration request for a
new suberror codes MUST include the following fields:
* Number: Is the wire format suberror code (range 0-255).
* Meaning: Provides a short description of the sub-error.
* Applicability: Indicates which RFC8914 error codes apply to this
sub-error code.
* Reference: Provides a pointer to an IETF-approved specification
that registered the code and/or an authoritative specification
that describes the meaning of this code.
* Change Controller: Indicates the person or entity, with contact
information if appropriate.
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The SubError Code registry is initially be populated with the
following suberror codes:
+========+==========+===================+=============+============+
| Number | Meaning | RFC8914 error | Reference | Change |
| | | code | | Controller |
| | | applicability | | |
+========+==========+===================+=============+============+
| 0 | Reserved | Not used | Section 6.1 | IETF |
| | | | of this | |
| | | | document | |
+--------+----------+-------------------+-------------+------------+
| 1 | Malware | "Blocked", | Section 5.5 | IETF |
| | | "Blocked by | of | |
| | | Upstream Server", | [RFC5901] | |
| | | "Filtered" | | |
+--------+----------+-------------------+-------------+------------+
| 2 | Phishing | "Blocked", | Section 5.5 | IETF |
| | | "Blocked by | of | |
| | | Upstream Server", | [RFC5901] | |
| | | "Filtered" | | |
+--------+----------+-------------------+-------------+------------+
| 3 | Spam | "Blocked", | Page 289 of | IETF |
| | | "Blocked by | [RFC4949] | |
| | | Upstream Server", | | |
| | | "Filtered" | | |
+--------+----------+-------------------+-------------+------------+
| 4 | Spyware | "Blocked", | Page 291 of | IETF |
| | | "Blocked by | [RFC4949] | |
| | | Upstream Server", | | |
| | | "Filtered" | | |
+--------+----------+-------------------+-------------+------------+
| 5 | Network | "Blocked" | Section 6.2 | IETF |
| | operator | | of this | |
| | policy | | document | |
+--------+----------+-------------------+-------------+------------+
| 6 | DNS | "Blocked" | Section 6.3 | IETF |
| | operator | | of this | |
| | policy | | document | |
+--------+----------+-------------------+-------------+------------+
Table 3: Initial SubError Code Registry
New SubError Codes are registered via IETF Review (Section 4.8 of
[RFC8126]).
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10.5. New Extended DNS Error Code
IANA is requested to assign the following Extended DNS Error code
from the "Domain Name System (DNS) Parameters, Extended DNS Error
Codes" registry [IANA-DNS]:
+===========+============================+===========+
| INFO-CODE | Purose | Reference |
+===========+============================+===========+
| TBA1 | Blocked by Upstream Server | RFCXXXX |
+-----------+----------------------------+-----------+
Table 4: New DNS Error Code
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC3966] Schulzrinne, H., "The tel URI for Telephone Numbers",
RFC 3966, DOI 10.17487/RFC3966, December 2004,
<https://www.rfc-editor.org/rfc/rfc3966>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<https://www.rfc-editor.org/rfc/rfc4949>.
[RFC5198] Klensin, J. and M. Padlipsky, "Unicode Format for Network
Interchange", RFC 5198, DOI 10.17487/RFC5198, March 2008,
<https://www.rfc-editor.org/rfc/rfc5198>.
[RFC5630] Audet, F., "The Use of the SIPS URI Scheme in the Session
Initiation Protocol (SIP)", RFC 5630,
DOI 10.17487/RFC5630, October 2009,
<https://www.rfc-editor.org/rfc/rfc5630>.
[RFC5901] Cain, P. and D. Jevans, "Extensions to the IODEF-Document
Class for Reporting Phishing", RFC 5901,
DOI 10.17487/RFC5901, July 2010,
<https://www.rfc-editor.org/rfc/rfc5901>.
[RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
URI Scheme", RFC 6068, DOI 10.17487/RFC6068, October 2010,
<https://www.rfc-editor.org/rfc/rfc6068>.
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[RFC6838] Freed, N., Klensin, J., and T. Hansen, "Media Type
Specifications and Registration Procedures", BCP 13,
RFC 6838, DOI 10.17487/RFC6838, January 2013,
<https://www.rfc-editor.org/rfc/rfc6838>.
[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/rfc/rfc6891>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/rfc/rfc7159>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/rfc/rfc7493>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/rfc/rfc8126>.
[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/rfc/rfc8174>.
[RFC8310] Dickinson, S., Gillmor, D., and T. Reddy, "Usage Profiles
for DNS over TLS and DNS over DTLS", RFC 8310,
DOI 10.17487/RFC8310, March 2018,
<https://www.rfc-editor.org/rfc/rfc8310>.
[RFC8914] Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
Lawrence, "Extended DNS Errors", RFC 8914,
DOI 10.17487/RFC8914, October 2020,
<https://www.rfc-editor.org/rfc/rfc8914>.
11.2. Informative References
[I-D.ietf-add-ddr]
Pauly, T., Kinnear, E., Wood, C. A., McManus, P., and T.
Jensen, "Discovery of Designated Resolvers", Work in
Progress, Internet-Draft, draft-ietf-add-ddr-10, 5 August
2022, <https://datatracker.ietf.org/doc/html/draft-ietf-
add-ddr-10>.
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[I-D.ietf-add-resolver-info]
Reddy.K, T. and M. Boucadair, "DNS Resolver Information",
Work in Progress, Internet-Draft, draft-ietf-add-resolver-
info-08, 24 November 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-add-
resolver-info-08>.
[IANA-DNS] IANA, "Domain Name System (DNS) Parameters, Extended DNS
Error Codes", <https://www.iana.org/assignments/dns-
parameters/dns-parameters.xhtml#extended-dns-error-codes>.
[IANA-MediaTypes]
IANA, "Media Types",
<https://www.iana.org/assignments/media-types>.
[Impl-1] "Use of DNS Errors To improve Browsing User Experience
With network based malware protection", March 2023,
<https://datatracker.ietf.org/meeting/116/materials/
slides-116-dnsop-dns-errors-implementation-proposal-
slides-116-dnsop-update-on-dns-errors-implementation-00>.
[RFC5625] Bellis, R., "DNS Proxy Implementation Guidelines",
BCP 152, RFC 5625, DOI 10.17487/RFC5625, August 2009,
<https://www.rfc-editor.org/rfc/rfc5625>.
[RFC7858] Hu, Z., Zhu, L., Heidemann, J., Mankin, A., Wessels, D.,
and P. Hoffman, "Specification for DNS over Transport
Layer Security (TLS)", RFC 7858, DOI 10.17487/RFC7858, May
2016, <https://www.rfc-editor.org/rfc/rfc7858>.
[RFC8259] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", STD 90, RFC 8259,
DOI 10.17487/RFC8259, December 2017,
<https://www.rfc-editor.org/rfc/rfc8259>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/rfc/rfc8484>.
[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/rfc/rfc8499>.
[RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
"Handling Long Lines in Content of Internet-Drafts and
RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
<https://www.rfc-editor.org/rfc/rfc8792>.
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[RFC9250] Huitema, C., Dickinson, S., and A. Mankin, "DNS over
Dedicated QUIC Connections", RFC 9250,
DOI 10.17487/RFC9250, May 2022,
<https://www.rfc-editor.org/rfc/rfc9250>.
[RPZ] "Response Policy Zone", <https://dnsrpz.info>.
Appendix A. Interoperation with RPZ Servers
This appendix provides a non-normative guidance for operation with an
Response Policy Zones (RPZ) server [RPZ] that indicates filtering
with a NXDOMAIN response with the Recursion Available bit cleared
(RA=0). This guidance is provided to ease interoperation with RPZ.
When a DNS client supports this specification, it includes the EDE
option in its DNS query.
If the server does not support this specification and is performing
RPZ filtering, the server ignores the EDE option in the DNS query and
replies with NXDOMAIN and RA=0. The DNS client can continue to
accept such responses.
If the server does support this specification and is performing RPZ
filtering, the server can use the EDE option in the query to identify
an EDE-aware client and respond appropriately (that is, by generating
a response described in Section 5.2) as NXDOMAIN and RA=0 are not
necessary when generating a response to such a client.
Appendix B. Implementation Status
Note to the RFC Editor: please remove this appendix prior
publication.
At IETF#116, Gianpaolo Scalone (Vodafone) and Ralf Weber (Akamai)
presented an implementation of this specification. More details can
be found at [Impl-1].
Acknowledgements
Thanks to Vittorio Bertola, Wes Hardaker, Ben Schwartz, Erid Orth,
Viktor Dukhovni, Warren Kumari, Paul Wouters, John Levine, Bob
Harold, and Mukund Sivaraman for the comments.
Thanks to Ralf Weber and Gianpaolo Scalone for sharing details about
their implementation.
Thanks Di Ma and Matt Brown for the DNS directorate reviews, and
Joseph Salowey for the Security directorate review.
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Authors' Addresses
Dan Wing
Citrix Systems, Inc.
United States of America
Email: danwing@gmail.com
Tirumaleswar Reddy
Nokia
Bangalore
Karnataka
India
Email: kondtir@gmail.com
Neil Cook
Open-Xchange
United Kingdom
Email: neil.cook@noware.co.uk
Mohamed Boucadair
Orange
Rennes
35000
France
Email: mohamed.boucadair@orange.com
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