Internet DRAFT - draft-reddy-add-server-policy-selection
draft-reddy-add-server-policy-selection
ADD WG T. Reddy
Internet-Draft Akamai
Intended status: Standards Track D. Wing
Expires: April 10, 2022 Citrix
M. Richardson
Sandelman Software Works
M. Boucadair
Orange
October 7, 2021
DNS Server Selection: DNS Server Information with Assertion Token
draft-reddy-add-server-policy-selection-09
Abstract
The document defines a mechanism that is meant to communicate DNS
resolver information to DNS clients for use as a criteria for server
selection decisions. Such an information that is cryptographically
signed to attest its authenticity is used for the selection of DNS
resolvers. Typically, evaluating the resolver information and the
signatory, DNS clients with minimal or no human intervention can
select the DNS servers for resolving domain names.
This assertion is useful for encrypted DNS (e.g., DNS-over-TLS, DNS-
over-HTTPS, or DNS-over-QUIC) servers that are either public
resolvers or discovered in a local network.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 10, 2022.
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Copyright Notice
Copyright (c) 2021 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Resolver Assertion Token (REAT): Overview . . . . . . . . . . 4
4. REAT Header . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. 'typ' (Type) Header Parameter . . . . . . . . . . . . . . 6
4.2. 'alg' (Algorithm) Header Parameter . . . . . . . . . . . 6
4.3. 'x5u' (X.509 URL) Header Parameter . . . . . . . . . . . 6
4.4. An Example of REAT Header . . . . . . . . . . . . . . . . 7
5. REAT Payload . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. JWT Defined Claims . . . . . . . . . . . . . . . . . . . 7
5.1.1. 'iat' - Issued At Claim . . . . . . . . . . . . . . . 7
5.1.2. 'exp' - Expiration Time Claim . . . . . . . . . . . . 7
5.2. REAT Specific Claims . . . . . . . . . . . . . . . . . . 8
5.2.1. DNS Server Identity Claims . . . . . . . . . . . . . 8
5.2.2. 'resinfo' (Resolver Information) Claim . . . . . . . 8
5.2.3. An Example . . . . . . . . . . . . . . . . . . . . . 9
6. REAT Signature . . . . . . . . . . . . . . . . . . . . . . . 9
7. Extending REAT . . . . . . . . . . . . . . . . . . . . . . . 10
8. Deterministic JSON Serialization . . . . . . . . . . . . . . 10
8.1. Example REAT Deterministic JSON Form . . . . . . . . . . 11
9. Using RESINFO Responses . . . . . . . . . . . . . . . . . . . 11
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
11.1. Media Type Registration . . . . . . . . . . . . . . . . 12
11.1.1. Media Type Registry Contents Additions Requested . . 12
11.2. JSON Web Token Claims Registration . . . . . . . . . . . 13
11.2.1. Registry Contents Additions Requested . . . . . . . 13
11.3. DNS Resolver Information Registration . . . . . . . . . 14
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . 14
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13.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Example of ES256-based REAT JWS Serialization and
Signature . . . . . . . . . . . . . . . . . . . . . 18
A.1. X.509 Private Key in PKCS#8 Format for ES256 Example** . 20
A.2. X.509 Public Key for ES256 Example** . . . . . . . . . . 20
Appendix B. Complete JWS JSON Serialization Representation with
multiple Signatures . . . . . . . . . . . . . . . . 20
B.1. X.509 Private Key in PKCS#8 format for E384 Example** . . 21
B.2. X.509 Public Key for ES384 Example** . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
[RFC7626] discusses DNS privacy considerations in both "on the wire"
(Section 2.4 of [RFC7626]) and "in the server" (Section 2.5 of
[RFC7626]) contexts. Examples of protocols that provide encrypted
channels between DNS clients and servers are DNS-over-HTTPS (DoH)
[RFC8484], DNS-over-TLS (DoT) [RFC7858], and DNS-over-QUIC (DoQ)
[I-D.ietf-dprive-dnsoquic].
DNS clients can discover and authenticate encrypted DNS servers
provided by a local network, for example using the techniques
proposed in [I-D.ietf-add-dnr] and [I-D.ietf-add-ddr]. If the
mechanism used to discover the encrypted DNS server is insecure, the
DNS client needs evidence about the encrypted server to assess its
trustworthiness and a way to appraise such evidence. The mechanism
specified in this document can be used by the DNS client to
cryptographically identify if it is connecting to an encrypted DNS
server hosted by a specific organization (e.g., ISP or Enterprise).
This strengthens the protection as clients can detect and reject
connections to encrypted DNS servers hosted by attackers.
2. Terminology
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 makes use of the terms defined in [RFC8499] and
[I-D.ietf-dnsop-terminology-ter].
'Encrypted DNS' refers to a DNS protocol that provides an encrypted
channel between a DNS client and server (e.g., DoT, DoH, or DoQ).
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The terms 'Evidence', 'Verifier', 'Background Check', 'Relying
Party', 'Appraisal Policy', and 'Attestation Results' are defined in
[I-D.ietf-rats-architecture].
3. Resolver Assertion Token (REAT): Overview
The mechanism used in this specification resembles the Background-
Check Model discussed in Sections 5.2 and 5.3 of Remote attestation
procedure (RATS) Architecture [I-D.ietf-rats-architecture]. RATS
enables a relying party to establish a level of confidence in the
trustworthiness of a remote peer through the creation of Evidence to
assess the peer's trustworthiness, and an Appraisal Policy for such
Evidence.
In this document, the Relying Party is the DNS client and the
Attester is the encrypted DNS server. The Encrypted DNS servers MAY
use "Domain Validation" (DV) certificates for certificate-based
server authentication in TLS connections.
The DNS server's resolver information needs to be validated and
signed. This signature is called an Attestation Result
[I-D.ietf-rats-architecture]. This validation can be performed by
the DNS operator itself (signed by the DNS operator's certificate)
acting as a verifier or performed by an external Verifier (signed by
that external Verifier). The signing certificate can to be an
Extended Validation (EV) certificate issued by a public CA in
specific scenarios listed below. An EV certificate is issued by the
public CA after a thorough Background Check to verify the requesting
organization's legal identity. If the signing certificate is a EV
certificate, it leaves the client with a better audit trail of the
organization hosting the DNS server in comparison with the DV
certificate.
The use of EV certificate is needed in the following scenarios:
o It helps the client to avoid sending DNS queries to an Encrypted
DNS server hosted by an attacker discovered insecurely (e.g.,
using DHCP/RA or DNS). For example, an attacker can get a domain
name, domain-validated public certificate from a CA and host a
Encrypted DNS server. Furthermore, an attacker can use a public
IP address, get an 'IP address'-validated public certificate from
a CA and host a Encrypted DNS server.
o It can be used by the client to identify the Encrypted DNS server
is hosted by a legal organization.
The use of EV certificate is not required in the following scenarios:
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o If the Encrypted DNS server can only be discovered securely (e.g.,
using IKEv2 [I-D.btw-add-ipsecme-ike]), the signing certificate
need not be an EV certificate.
o Secure Zero Touch Provisioning [RFC8572] defines a bootstrapping
strategy for enabling a networking device to securely obtain the
required configuration information with no user input. If the
encrypted DNS server is insecurely discovered and not
preconfigured in the networking device, the DNS client on the
networking device can validate the Resolver Assertion Token
signature using the owner certificate as per Section 3.2 of
[RFC8572].
JSON Web Token (JWT) [RFC7519] and JSON Web Signature (JWS) [RFC7515]
and related specifications define a standard token format that can be
used as a way of encapsulating claimed or asserted information with
an associated digital signature using X.509 based certificates. JWT
provides a set of claims in JSON format that can accommodate asserted
resolver information of the Encrypted DNS server. Additionally, JWS
provides a path for updating methods and cryptographic algorithms
used for the associated digital signatures.
JWS defines the use of JSON data structures in a specified canonical
format for signing data corresponding to JOSE header, JWS Payload,
and JWS Signature. The next sections define the header and claims
that MUST be minimally used with JWT and JWS for resolver assertion
token.
The REsolver Assertion Token (REAT) specifically uses this token
format and defines claims that convey the resolver information of
Encrypted DNS server.
The client can retrieve the REAT object using the RESINFO RRtype
defined in [I-D.reddy-add-resolver-info] and QNAME of the domain name
that is used to authenticate the DNS server (referred to as ADN in
[RFC8310]). If the special use domain name "resolver.arpa" defined
in [I-D.ietf-add-ddr] is used to discover the Encrypted DNS server,
the client can retrieve the REAT object using the RESINFO RRtype and
QNAME of the special use domain name.
The signature of REAT object MUST be validated by the DNS client. If
signature is invalid, the REAT object is rejected. If signature is
valid and signer is trusted, the DNS client can use that encrypted
DNS server.
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4. REAT Header
The JWS token header is a JOSE header (Section 4 of [RFC7515]) that
defines the type and encryption algorithm used in the token.
The REAT header MUST include, at a minimum, the header parameters
defined in Sections 4.1, 4.2, and 4.3.
4.1. 'typ' (Type) Header Parameter
The 'typ' (Type) Header Parameter is defined in Section 4.1.9 of
[RFC7515] to declare the media type of the complete JWS.
For REAT Token the 'typ' header MUST be the string 'rat'. This
represents that the encoded token is a JWT of type rat.
4.2. 'alg' (Algorithm) Header Parameter
The 'alg' (Algorithm) Header Parameter is defined in Section 4.1.1 of
[RFC7515]. It specifies the JWS signature cryptographic algorithm.
It also refers to a list of defined 'alg' values as part of a
registry established by JSON Web Algorithms (JWA) [RFC7518]
Section 3.1.
For the creation and verification of REAT tokens and their digital
signatures, implementations MUST support ES256 as defined in
Section 3.4 of [RFC7518]. Implementations MAY support other
algorithms registered in the JSON Web Signature and Encryption
Algorithms registry created by [RFC7518]. The content of that
registry may be updated in the future depending on cryptographic
strength requirements guided by current security best practice. The
mandatory-to-support algorithm for REAT tokens may likewise be
updated in the future.
Implementations of REAT digital signatures using ES256 as defined
above SHOULD use deterministic ECDSA when supported for the reasons
stated in [RFC6979].
4.3. 'x5u' (X.509 URL) Header Parameter
As defined in Section 4.1.5 of [RFC7515], the 'x5u' header parameter
defines a URI [RFC3986] referring to the resource for the X.509
public key certificate or certificate chain [RFC5280] corresponding
to the key used to digitally sign the JWS. Generally, as defined in
Section 4.1.5 of [RFC7515] this corresponds to an HTTPS or DNSSEC
resource using integrity protection.
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4.4. An Example of REAT Header
An example of the REAT header is shown in Figure 1. It includes the
specified REAT type, ES256 algorithm, and an URI referencing the
network location of the certificate needed to validate the REAT
signature.
{
"typ":"rat",
"alg":"ES256",
"x5u":"https://cert.example.com/rat.cer"
}
Figure 1: A REAT Header Example
5. REAT Payload
The token claims consist of the resolver information of the DNS
server that needs to be verified at the DNS client. These claims
follow the definition of a JWT claim (Section 4 of [RFC7519]) and are
encoded as defined by the JWS Payload (Section 3 of [RFC7515]).
REAT defines the use of a standard JWT-defined claim as well as
custom claims corresponding to the DoT or DoH servers.
Claim names MUST use the US-ASCII character set. Claim values MAY
contain characters that are outside the ASCII range, however they
MUST follow the default JSON serialization defined in Section 7 of
[RFC7519].
5.1. JWT Defined Claims
5.1.1. 'iat' - Issued At Claim
The JSON claim MUST include the 'iat' (Section 4.1.6 of [RFC7519])
defined claim "Issued At". The 'iat' should be set to the date and
time of issuance of the JWT. The time value should be of the format
(NumericDate) defined in Section 2 of [RFC7519].
5.1.2. 'exp' - Expiration Time Claim
The JSON claim MUST include the 'exp' (Section 4.1.4 of [RFC7519])
defined "claim Expiration Time". The 'exp' should be set to specify
the expiration time on or after which the JWT is not accepted for
processing. The REAT object should expire after a reasonable
duration. A short expiration time for the REAT object periodically
reaffirms the resolver information of the DNS server to the DNS
client and ensures the DNS client does not use outdated resolver
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information. If the DNS client knows the REAT object has expired, it
should make another request to get the new REAT object from the DNS
server.
5.2. REAT Specific Claims
5.2.1. DNS Server Identity Claims
The DNS server identity is represented by a claim that is required
for REAT: the 'server' claim. The 'server' MUST contain claim values
that are identity claim JSON objects where the child claim name
represents an identity type and the claim value is the identity
string, both defined in subsequent subsections.
These identities can be represented as either authentication domain
name (ADN) (defined in [RFC8310]) or Uniform Resource Indicators
(URI).
The DNS client constructs a reference identifier for the DNS server
based on the ADN or the domain portion in the URI of the DNS server
identity. The domain name in the DNS-ID identifier type within
subjectAltName entry in the DNS server certificate conveyed in the
TLS handshake is matched with the reference identifier. If the match
is not successful, the client MUST not accept the REAT for further
processing.
5.2.1.1. 'adn' - Authentication Domain Name Identity
If the DNS server identity is an ADN, the claim name representing the
identity MUST be 'adn'. The claim value for the 'adn' claim is the
ADN.
5.2.1.2. 'uri' - URI Identity
If the DNS server identity is of the form URI Template, as defined in
[RFC6570], the claim name representing the identity MUST be 'uri' and
the claim value is the URI Template form of the DNS server identity.
As a reminder, if DoH is supported by the DNS server, the DNS client
uses the URI Template (Section 3 of [RFC8484]).
5.2.2. 'resinfo' (Resolver Information) Claim
The 'resinfo' claim contains the resolver information of the DNS
server defined in Section 5 of [I-D.reddy-add-resolver-info].
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5.2.3. An Example
Figure 2 shows an example of resolver information.
{
"server":{
"adn":"example.com"
},
"iat":1443208345,
"exp":1443640345,
"resinfo": {
"qnameminimization":false,
}
}
Figure 2: An Example of Resolver Information
6. REAT Signature
The signature of the REAT is created as specified in Section 5.1 of
[RFC7515] (Steps 1 through 6). REAT MUST use the JWS Protected
Header.
For the JWS Payload and the JWS Protected Header, the lexicographic
ordering and white space rules described in Section 4 and Section 5,
and JSON serialization rules in Section 8 MUST be followed.
The REAT is cryptographically signed by the domain hosting the DNS
server and optionally by a third party who performed privacy and
security audit of the DNS server.
The resolver information is attested using "Extended Validation" (EV)
certificate to avoid bad actors taking advantage of this mechanism to
advertise encrypted DNS servers for illegitimate and fraudulent
purposes meant to trick DNS clients into believing that they are
using a legitimate encrypted DNS server hosted to provide privacy for
DNS transactions.
Alternatively, a DNS client has to be configured to trust the leaf of
the signer of the REAT object. That is, trust of the signer MUST NOT
be determined by validating the signer via the OS or the browser
trust chain because that would allow any arbitrary entity to operate
a DNS server and assert any sort of resolver information.
Appendix A provides an example of how to follow the steps to create
the JWS Signature.
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JWS JSON serialization (Step 7 in Section 5.1 of [RFC7515]) is
supported for REAT to enable multiple signatures to be applied to the
REAT object. For example, the REAT object can be cryptographically
signed by the domain hosting the DNS server and by a third party who
performed privacy and security audit of the DNS server.
Appendix B includes an example of the full JWS JSON serialization
representation with multiple signatures.
Section 5.1 of [RFC7515] (Step 8) describes the method to create the
final JWS Compact Serialization form of the REAT Token.
7. Extending REAT
REAT includes the minimum set of claims needed to securely assert the
resolver information of the DNS server. JWT supports a mechanism to
add additional asserted or signed information by simply adding new
claims. REAT can be extended beyond the defined base set of claims
to represent other DNS server information requiring assertion or
validation. Specifying new claims follows the baseline JWT
procedures (Section 10.1 of [RFC7519]). Understanding new claims on
the DNS client is optional. The creator of a REAT object cannot
assume that the DNS client will understand the new claims.
8. Deterministic JSON Serialization
JSON objects can include spaces and line breaks, and key value pairs
can occur in any order. It is therefore a non-deterministic string
format. In order to make the digital signature verification work
deterministically, the JSON representation of the JWS Protected
Header object and JWS Payload object MUST be computed as follows.
The JSON object MUST follow the following rules. These rules are
based on the thumbprint of a JSON Web Key (JWK) as defined in
Section 3 of [RFC7638] (Step 1).
1. The JSON object MUST contain no whitespace or line breaks before
or after any syntactic elements.
2. JSON objects MUST have the keys ordered lexicographically by the
Unicode [UNICODE] code points of the member names.
3. JSON value literals MUST be lowercase.
4. JSON numbers are to be encoded as integers unless the field is
defined to be encoded otherwise.
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5. Encoding rules MUST be applied recursively to member values and
array values.
8.1. Example REAT Deterministic JSON Form
This section demonstrates the deterministic JSON serialization for
the example REAT Payload shown in Section 5.2.3.
The initial JSON object is shown in Figure 3.
{
"server":{
"adn":"example.com"
},
"iat":1443208345,
"exp":1443640345,
"resinfo": {
"qnameminimization":false,
}
}
Figure 3: Initial JSON Object
The parent members of the JSON object are as follows, in
lexicographic order: "exp", "iat", "resinfo", "server".
The final constructed deterministic JSON serialization
representation, with whitespace and line breaks removed, (with line
breaks used for display purposes only) is:
{"exp":1443640345,"iat":1443208345,
"resinfo":{"qnameminimization":false},
"server":{"adn":"example.com"}}
Figure 4: Deterministic JSON Form
9. Using RESINFO Responses
This document defines the following entry for the IANA DNS Resolver
Information Registry that is defined in [I-D.reddy-add-resolver-
info].
o The "attested-resinfo" name contains the full REAT object. The
REAT header, REAT payload, and REAT signature components comprise
a full REAT object. If the "attested-resinfo" name is conveyed to
the client, the server need not convey the attributes
"resinfourl", "identityurl", "extendeddnserror" and
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"qnameminimization" attributes separately as that resolver
information will be extracted by the client from the REAT payload.
10. Security Considerations
The use of REAT object based on the validation of the digital
signature and the associated certificate requires consideration of
the authentication and authority or reputation of the signer to
attest the resolver information of the DNS server being asserted.
Bad actors can host encrypted DNS servers to invade the privacy of
the user. Bad actor can get a domain name, host encrypted DNS
servers, and get the DNS server certificate signed by a CA. The
resolver information will have to be attested using EV certificates
or a REAT object signer trusted by the DNS client to prevent the
attack.
The CA that issued the EV certificate does not attest the resolver
information. The organization hosting the DNS server attests the
resolver information using the EV certificate and the client uses the
EV certificate to identify the organization (e.g., ISP or Enterprise)
hosting the DNS server.
If the REAT object is asserted by a third party, it can do a "time of
check" but the DNS server is susceptible of "time of use" attack.
For example, changes to the DNS server can cause a disagreement
between the auditor and the DNS server operation, hence the REAT
object needs to be also asserted by the domain hosting the DNS
server. In addition, the REAT object needs to have a short
expiration time (e.g., 7 days) to ensure the DNS server's domain re-
asserts the resolver information and limits the damage from change in
behaviour and mis-issuance.
11. IANA Considerations
11.1. Media Type Registration
11.1.1. Media Type Registry Contents Additions Requested
This section registers the 'application/rat' media type [RFC2046] in
the 'Media Types' registry in the manner described in [RFC6838],
which can be used to indicate that the content is a REAT defined JWT.
o Type name: application
o Subtype name: rat
o Required parameters: n/a
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o Optional parameters: n/a
o Encoding considerations: 8bit; application/rat values are encoded
as a series of base64url-encoded values (some of which may be the
empty string) separated by period ('.') characters..
o Security considerations: See the Security Considerations
Section of [RFC7515].
o Interoperability considerations: n/a
o Published specification: [THIS_DOCUMENT]
o Applications that use this media type: DNS
o Fragment identifier considerations: n/a
o Additional information:
Magic number(s): n/a File extension(s): n/a Macintosh file type
code(s): n/a
o Person & email address to contact for further information:
Tirumaleswar Reddy, kondtir@gmail.com
o Intended usage: COMMON
o Restrictions on usage: none
o Author: Tirumaleswar Reddy, kondtir@gmail.com
o Change Controller: IESG
o Provisional registration? No
11.2. JSON Web Token Claims Registration
11.2.1. Registry Contents Additions Requested
IANA is requested to assign the following claims in the registry
maintained in: https://www.iana.org/assignments/jwt/jwt.xhtml.
o Claim Name: 'server'
o Claim Description: DNS server identity
o Change Controller: IESG
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o Specification Document(s): Section 5.2.1 of [THIS_DOCUMENT]
o Claim Name: 'resinfo'
o Claim Description: Resolver information of DNS server.
o Change Controller: IESG
o Specification Document(s): Section 5.2.2 of [THIS_DOCUMENT]
11.3. DNS Resolver Information Registration
IANA will add the name "attested-resinfo" to the DNS Resolver
Information registry defined in Section 7.2 of [I-D.reddy-add-
resolver-info].
12. Acknowledgments
This specification leverages some of the work that has been done in
[RFC8225]. Thanks to Tommy Jensen, Ted Lemon, Paul Wouters, Neil
Cook, Vittorio Bertola, Vinny Parla, Chris Box, Ben Schwartz and
Shashank Jain for the discussion and comments.
13. References
13.1. Normative References
[I-D.ietf-add-ddr]
Pauly, T., Kinnear, E., Wood, C. A., McManus, P., and T.
Jensen, "Discovery of Designated Resolvers", draft-ietf-
add-ddr-03 (work in progress), October 2021.
[I-D.ietf-add-dnr]
Boucadair, M., Reddy, T., Wing, D., Cook, N., and T.
Jensen, "DHCP and Router Advertisement Options for the
Discovery of Network-designated Resolvers (DNR)", draft-
ietf-add-dnr-02 (work in progress), May 2021.
[I-D.reddy-add-resolver-info]
Reddy, T. and M. Boucadair, "DNS Resolver Information",
draft-reddy-add-resolver-info-03 (work in progress), April
2021.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
DOI 10.17487/RFC2046, November 1996,
<https://www.rfc-editor.org/info/rfc2046>.
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[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/info/rfc2119>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<https://www.rfc-editor.org/info/rfc5280>.
[RFC6570] Gregorio, J., Fielding, R., Hadley, M., Nottingham, M.,
and D. Orchard, "URI Template", RFC 6570,
DOI 10.17487/RFC6570, March 2012,
<https://www.rfc-editor.org/info/rfc6570>.
[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/info/rfc6838>.
[RFC6979] Pornin, T., "Deterministic Usage of the Digital Signature
Algorithm (DSA) and Elliptic Curve Digital Signature
Algorithm (ECDSA)", RFC 6979, DOI 10.17487/RFC6979, August
2013, <https://www.rfc-editor.org/info/rfc6979>.
[RFC7493] Bray, T., Ed., "The I-JSON Message Format", RFC 7493,
DOI 10.17487/RFC7493, March 2015,
<https://www.rfc-editor.org/info/rfc7493>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
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[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <https://www.rfc-editor.org/info/rfc7638>.
[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/info/rfc7858>.
[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>.
[RFC8484] Hoffman, P. and P. McManus, "DNS Queries over HTTPS
(DoH)", RFC 8484, DOI 10.17487/RFC8484, October 2018,
<https://www.rfc-editor.org/info/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/info/rfc8499>.
13.2. Informative References
[I-D.btw-add-home]
Boucadair, M., Reddy, T., Wing, D., Cook, N., and T.
Jensen, "DHCP and Router Advertisement Options for
Encrypted DNS Discovery", draft-btw-add-home-12 (work in
progress), January 2021.
[I-D.btw-add-ipsecme-ike]
Boucadair, M., Reddy, T., Wing, D., and V. Smyslov,
"Internet Key Exchange Protocol Version 2 (IKEv2)
Configuration for Encrypted DNS", draft-btw-add-ipsecme-
ike-03 (work in progress), May 2021.
[I-D.ietf-dnsop-terminology-ter]
Hoffman, P., "Terminology for DNS Transports and
Location", draft-ietf-dnsop-terminology-ter-02 (work in
progress), August 2020.
[I-D.ietf-dprive-dnsoquic]
Huitema, C., Dickinson, S., and A. Mankin, "Specification
of DNS over Dedicated QUIC Connections", draft-ietf-
dprive-dnsoquic-04 (work in progress), September 2021.
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[I-D.ietf-rats-architecture]
Birkholz, H., Thaler, D., Richardson, M., Smith, N., and
W. Pan, "Remote Attestation Procedures Architecture",
draft-ietf-rats-architecture-12 (work in progress), April
2021.
[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/info/rfc7159>.
[RFC7626] Bortzmeyer, S., "DNS Privacy Considerations", RFC 7626,
DOI 10.17487/RFC7626, August 2015,
<https://www.rfc-editor.org/info/rfc7626>.
[RFC7816] Bortzmeyer, S., "DNS Query Name Minimisation to Improve
Privacy", RFC 7816, DOI 10.17487/RFC7816, March 2016,
<https://www.rfc-editor.org/info/rfc7816>.
[RFC8225] Wendt, C. and J. Peterson, "PASSporT: Personal Assertion
Token", RFC 8225, DOI 10.17487/RFC8225, February 2018,
<https://www.rfc-editor.org/info/rfc8225>.
[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/info/rfc8259>.
[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/info/rfc8310>.
[RFC8572] Watsen, K., Farrer, I., and M. Abrahamsson, "Secure Zero
Touch Provisioning (SZTP)", RFC 8572,
DOI 10.17487/RFC8572, April 2019,
<https://www.rfc-editor.org/info/rfc8572>.
[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/info/rfc8914>.
[UNICODE] The Unicode Consortium, "The Unicode Standard", June 2016,
<http://www.unicode.org/versions/latest/>.
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Appendix A. Example of ES256-based REAT JWS Serialization and Signature
For REAT, there will always be a JWS with the following members:
o 'protected', with the value BASE64URL(UTF8(JWS Protected Header))
o 'payload', with the value BASE64URL (JWS Payload)
o 'signature', with the value BASE64URL(JWS Signature)
This example will follow the steps in JWS [RFC7515] Section 5.1,
steps 1-6 and 8 and incorporates the additional serialization steps
required for REAT.
Step 1 for JWS references the JWS Payload, an example REAT Payload is
as follows:
{
"server":{
"adn":"example.com"
},
"iat":1443208345,
"exp":1443640345,
"resinfo": {
"qnameminimization":false
}
}
This would be serialized to the form (with line break used for
display purposes only):
{"exp":1443640345,"iat":1443208345,"resinfo":{
"qnameminimization":false},"server":{"adn":"example.com"}}
Step 2 Computes the BASE64URL(JWS Payload) producing this value (with
line break used for display purposes only):
eyJleHAiOjE0NDM2NDAzNDUsImlhdCI6MTQ0MzIwODM0NSwicmVzaW5mbyI6ey
JxbmFtZW1pbmltaXphdGlvbiI6ZmFsc2V9LCJzZXJ2ZXIiOnsiYWRuIjoiZXhh
bXBsZS5jb20ifX0
For Step 3, an example REAT Protected Header comprising the JOSE
Header is as follows:
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{
"alg":"ES256",
"typ":"rat",
"x5u":"https://cert.example.com/rat.cer"
}
This would be serialized to the form (with line break used for
display purposes only):
{"alg":"ES256","typ":"rat","x5u":"https://cert.example.com
/rat.cer"}
Step 4 Performs the BASE64URL(UTF8(JWS Protected Header)) operation
and encoding produces this value (with line break used for display
purposes only):
eyJhbGciOiJFUzI1NiIsInR5cCI6InJhdCIsIng1dSI6Imh0dHBzOi8vY2VydC5l
eGFtcGxlLmNvbS9yYXQuY2VyIn0
Step 5 and Step 6 performs the computation of the digital signature
of the REAT Signing Input ASCII(BASE64URL(UTF8(JWS Protected
Header)) || '.' || BASE64URL(JWS Payload)) using ES256 as the
algorithm and the BASE64URL(JWS Signature).
d1g7szj0roHsWe8psCzYVl4QdN2b7pQnq8EJhc4j3GOJj2NE6M9Em6aidtycnFJ5
mRj3ojiUfVF6rK5RksD0rg
Step 8 describes how to create the final REAT token, concatenating
the values in the order Header.Payload.Signature with period ('.')
characters. For the above example values this would produce the
following (with line breaks between period used for readability
purposes only):
eyJhbGciOiJFUzI1NiIsInR5cCI6InJhdCIsIng1dSI6Imh0dHBzOi8vY2VydC5l
eGFtcGxlLmNvbS9yYXQuY2VyIn0
.
eyJhbGciOiJFUzI1NiIsInR5cCI6InJhdCIsIng1dSI6Imh0dHBzOi8vY2VydC5l
eGFtcGxlLmNvbS9yYXQuY2VyIn0
.
d1g7szj0roHsWe8psCzYVl4QdN2b7pQnq8EJhc4j3GOJj2NE6M9Em6aidtycnFJ5
mRj3ojiUfVF6rK5RksD0rg
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A.1. X.509 Private Key in PKCS#8 Format for ES256 Example**
-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgevZzL1gdAFr88hb2
OF/2NxApJCzGCEDdfSp6VQO30hyhRANCAAQRWz+jn65BtOMvdyHKcvjBeBSDZH2r
1RTwjmYSi9R/zpBnuQ4EiMnCqfMPWiZqB4QdbAd0E7oH50VpuZ1P087G
-----END PRIVATE KEY-----
A.2. X.509 Public Key for ES256 Example**
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEEVs/o5+uQbTjL3chynL4wXgUg2R9
q9UU8I5mEovUf86QZ7kOBIjJwqnzD1omageEHWwHdBO6B+dFabmdT9POxg==
-----END PUBLIC KEY-----
Appendix B. Complete JWS JSON Serialization Representation with
multiple Signatures
The JWS payload used in this example as follows.
{
"server":{
"adn":"example.com"
},
"iat":1443208345,
"exp":1443640345,
"resinfo": {
"qnameminimization":false
}
}
This would be serialized to the form (with line break used for
display purposes only):
{"exp":1443640345,"iat":1443208345,"resinfo":{
"qnameminimization":false},"server":{"adn":"example.com"}}
The JWS protected Header value used for the first signature is same
as that used in the example in Appendix A. The X.509 private key
used for generating the first signature is same as that used in the
example in Appendix A.1.
The JWS Protected Header value used for the second signature is:
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{
"alg":"ES384",
"typ":"rat",
"x5u":"https://cert.audit-example.com/rat.cer"
}
The complete JWS JSON Serialization for these values is as follows
(with line breaks within values for display purposes only):
{
"payload":
"eyJhbGciOiJFUzI1NiIsInR5cCI6InJhdCIsIng1dSI6Imh0dHBzOi8vY2VydC5l
eGFtcGxlLmNvbS9yYXQuY2VyIn0",
"signatures":[
{"protected":"eyJhbGciOiJFUzI1NiIsInR5cCI6InJhdCIsIng1dSI6Imh0dHBz
Oi8vY2VydC5leGFtcGxlLmNvbS9yYXQuY2VyIn0",
"signature":"d1g7szj0roHsWe8psCzYVl4QdN2b7pQnq8EJhc4j3GOJj2NE6M9E
m6aidtycnFJ5mRj3ojiUfVF6rK5RksD0rg"},
{"protected":"eyJhbGciOiJFUzM4NCIsInR5cCI6InJhdCIsIng1dSI6Imh0dHB
zOi8vY2VydC5hdWRpdC1leGFtcGxlLmNvbS9yYXQuY2VyIn0",
"signature":"GnKuEEFql_Y8HdZl_mqd027DlziGRXFHvjMoY_ukX-M0k5v2jSL
vsQAYOGdKFnt3JY6t938HfBV1onsWerNhgceMJpx5hAsl-xus3fmNY8K1g6QK39
hn2Dhbleeeyp0f"}]
}
B.1. X.509 Private Key in PKCS#8 format for E384 Example**
-----BEGIN PRIVATE KEY-----
MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgevZzL1gdAFr88hb2
OF/2NxApJCzGCEDdfSp6VQO30hyhRANCAAQRWz+jn65BtOMvdyHKcvjBeBSDZH2r
1RTwjmYSi9R/zpBnuQ4EiMnCqfMPWiZqB4QdbAd0E7oH50VpuZ1P087G
-----END PRIVATE KEY-----
B.2. X.509 Public Key for ES384 Example**
-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEEVs/o5+uQbTjL3chynL4wXgUg2R9
q9UU8I5mEovUf86QZ7kOBIjJwqnzD1omageEHWwHdBO6B+dFabmdT9POxg==
-----END PUBLIC KEY-----
Authors' Addresses
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Tirumaleswar Reddy
Akamai
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
Dan Wing
Citrix Systems, Inc.
USA
Email: dwing-ietf@fuggles.com
Michael C. Richardson
Sandelman Software Works
USA
Email: mcr+ietf@sandelman.ca
Mohamed Boucadair
Orange
Rennes 35000
France
Email: mohamed.boucadair@orange.com
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