Internet DRAFT - draft-reddy-dprive-dprive-privacy-policy
draft-reddy-dprive-dprive-privacy-policy
DPRIVE WG T. Reddy
Internet-Draft McAfee
Intended status: Standards Track D. Wing
Expires: September 4, 2020 Citrix
M. Richardson
Sandelman Software Works
M. Boucadair
Orange
March 3, 2020
DNS Server Privacy Statement and Filtering Policy with Assertion Token
draft-reddy-dprive-dprive-privacy-policy-03
Abstract
Users may want to control how their DNS queries are handled by DNS
servers so they can configure their system to use DNS servers that
comply with their privacy and DNS filtering expectations.
This document defines a mechanism for a DNS server to communicate its
privacy statement URL and filtering policy to a DNS client. This
communication is cryptographically signed to attest its authenticity.
By evaluating the DNS privacy statement, filtering policy and the
signatory, the user can choose a DNS server that best supports his/
her desired privacy and filtering policy. This token is particularly
useful for DNS-over-TLS and DNS-over-HTTPS servers that are either
public resolvers or are discovered on 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 September 4, 2020.
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Copyright Notice
Copyright (c) 2020 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Use Cases Overview . . . . . . . . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Policy Assertion Token (PAT): Overview . . . . . . . . . . . 5
5. PAT Header . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. 'typ' (Type) Header Parameter . . . . . . . . . . . . . . 6
5.2. 'alg' (Algorithm) Header Parameter . . . . . . . . . . . 6
5.3. 'x5u' (X.509 URL) Header Parameter . . . . . . . . . . . 6
5.4. An Example of PAT Header . . . . . . . . . . . . . . . . 7
6. PAT Payload . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. JWT Defined Claims . . . . . . . . . . . . . . . . . . . 7
6.1.1. 'iat' - Issued At Claim . . . . . . . . . . . . . . . 7
6.1.2. 'exp' - Expiration Time Claim . . . . . . . . . . . . 7
6.2. PAT Specific Claims . . . . . . . . . . . . . . . . . . . 8
6.2.1. DNS Server Identity Claims . . . . . . . . . . . . . 8
6.2.2. 'policyinfo' (Policy Information) Claim . . . . . . . 8
6.2.3. Example . . . . . . . . . . . . . . . . . . . . . . . 9
7. PAT Signature . . . . . . . . . . . . . . . . . . . . . . . . 9
8. Extending PAT . . . . . . . . . . . . . . . . . . . . . . . . 10
9. Deterministic JSON Serialization . . . . . . . . . . . . . . 11
9.1. Example PAT Deterministic JSON Form . . . . . . . . . . . 11
10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 12
11. Security Considerations . . . . . . . . . . . . . . . . . . . 12
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
12.1. Media Type Registration . . . . . . . . . . . . . . . . 13
12.1.1. Media Type Registry Contents Additions Requested . . 13
12.2. JSON Web Token Claims Registration . . . . . . . . . . . 14
12.2.1. Registry Contents Additions Requested . . . . . . . 14
12.3. DNS Resolver Information Registration . . . . . . . . . 14
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
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14.1. Normative References . . . . . . . . . . . . . . . . . . 14
14.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Example ES256 based PAT JWS Serialization and
Signature . . . . . . . . . . . . . . . . . . . . . 17
A.1. X.509 Private Key in PKCS#8 Format for ES256 Example** . 19
A.2. X.509 Public Key for ES256 Example** . . . . . . . . . . 19
Appendix B. Complete JWS JSON Serialization Representation with
multiple Signatures . . . . . . . . . . . . . . . . 19
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. In recent years there has also been an increase
in the availability of "public resolvers" [RFC8499] which DNS clients
may be pre-configured to use instead of the default network resolver
because they offer a specific feature (e.g., good reachability,
encrypted transport, strong privacy policy, (lack of) filtering,
etc.). The DNS Recursive Operator Privacy (DROP) statement explained
in [I-D.ietf-dprive-bcp-op] outlines the recommended contents an DNS
operator should publish, thereby providing a means for users to
evaluate the privacy properties of a given DNS service. While a
human can review the privacy statement of a DNS server operator, but
the challenge is the user has to search to find the URL that points
to the human readable privacy policy information of the DNS server.
Also, a user does not know if a locally-discovered server performs
DNS-based filtering.
For DNS servers operated on the local network, the DNS client can be
securely bootstrapped to discover and authenticate DNS-over-HTTPS
(DoH) [RFC8484] and DNS-over-TLS (DoT) [RFC7858] servers provided by
a local network, for example using the technique proposed in
[I-D.reddy-dprive-bootstrap-dns-server]. This document defines a
retrievable DNS server policy permitting the user to consent to using
a certain DNS server that meets their needs.
The cryptographically signed policy allows a DNS client to connect to
multiple DNS servers and prompt the user to review the DNS privacy
statements to select the DNS server that adheres to the privacy
preserving data policy and DNS filtering expectations of the user.
For example, a browser with pre-configured DNS-over-HTTPS server can
discover the DNS-over-HTTPS server provided the local network,
connects to both the DNS servers, gets the policy information from
each of the DNS servers, validates the signatures and prompts the
user to review the privacy policy statements of both the local and
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public DNS server. If both servers meet the privacy preserving data
policy and DNS filtering requirements of the user, the user can
select to use the local DNS server. A quality implementation can
avoid presenting this information to the user if the DNS server's
policies have not changed.
2. Use Cases Overview
The mechanism for a DNS server to communicate its cryptographically
signed policies to a DNS client contribute to solve the following
problems in various deployments:
o Typically Enterprise networks do not assume that all devices in
their network are managed by the IT team or Mobile Device
Management (MDM) devices, especially in the quite common BYOD
(Bring Your Own Device) scenario. The mechanism specified in this
document can be used by users of the BYOD devices to determine if
the DNS server on the local network complies with the user's
privacy policy and DNS filtering expectations.
o The user selects specific well-known networks (e.g., organization
for which a user works or a user works temporarily within another
corporation) to learn the privacy policy statement and filtering
policy of the local DNS server. Then, the user can choose to use
the discovered DoT or DoH server. If that discovered DoT/DoH
server does not meet the privacy preserving data policy and
filtering requirements of the user, the user can instruct the DNS
client to take appropriate actions. For example, the action can
be to use the local DNS server only to access internal-only DNS
names and use another DNS server (adhering with his/her
expectations) for public domains.
o The policy information signals the presence of DNS-based content
filtering in the attached network. If the network is well-known
to the user and the local DNS server meets the privacy
requirements of the user, the DNS client can continue to use
encrypted connection with the local DoT/DoH server. If the error
code returned by the DNS server indicates access to the domain is
blocked because of internal security policy
[I-D.ietf-dnsop-extended-error], the DNS client can securely
identify access to the domain is censored by the network.
o The signed policy contains an URL that points to a human-readable
privacy policy information of the DNS server for the user to
review and can make an informed decision whether the DNS server is
trustworthy to honor the privacy of the user. The DNS Push
Notifications mechanism defined in [I-D.ietf-dnsop-extended-error]
can be used by the DNS client to be asynchronously notified when
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the policy change occurs. The client automatically learns updates
to the policy of the DNS server, and whenever the privacy
statement of the DNS server changes, the client can notify the
user to re-evaluate the updated privacy statement.
3. 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 uses the terms defined in [RFC8499].
4. Policy Assertion Token (PAT): Overview
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
policy information of the DoT/DoH 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 privacy assertion
token.
The Policy Assertion Token (PAT) specifically uses this token format
and defines claims that convey the policy information of DoT/ DoH
server. The client can retrieve the PAT object using the method
discussed in [I-D.ietf-dnsop-resolver-information]. The signature of
PAT object can be validated by the DNS client. If the signer and the
contents of the PAT object comply with the user's requirements, the
user's client software can use that DNS server.
The PAT object is signed by the DNS server's domain that is
authoritative to assert the DNS server policy information. This
authority is represented by the certificate credentials and the
signature.
For example, the PAT object could be created by the domain hosting
the DoT/DoH server and optionally by a third party who performed
privacy and security audit of the DoT/DoH server. The DNS client
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needs to have the capability to verify the digital signature and to
parse the PAT object.
5. PAT Header
The JWS token header is a JOSE header (Section 4 of [RFC7515]) that
defines the type and encryption algorithm used in the token.
PAT header MUST include, at a minimum, the header parameters defined
in Sections 5.1, 5.2, and 5.3.
5.1. 'typ' (Type) Header Parameter
The 'typ' (Type) Header Parameter is defined Section 4.1.9 of
[RFC7515] to declare the media type of the complete JWS.
For PAT Token the 'typ' header MUST be the string 'pat'. This
represents that the encoded token is a JWT of type pat.
5.2. '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 PAT 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 PAT tokens may likewise be updated
in the future.
Implementations of PAT digital signatures using ES256 as defined
above SHOULD use deterministic ECDSA when supported for the reasons
stated in [RFC6979].
5.3. '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
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Section 4.1.5 of [RFC7515] this corresponds to an HTTPS or DNSSEC
resource using integrity protection.
5.4. An Example of PAT Header
An example of the PAT header is shown in Figure 1. It includes the
specified PAT type, ES256 algorithm, and an URI referencing the
network location of the certificate needed to validate the PAT
signature.
{
"typ":"pat",
"alg":"ES256",
"x5u":"https://cert.example.com/pat.cer"
}
Figure 1: A PAT Header Example
6. PAT Payload
The token claims consists of the policy information of the DNS server
which needs to be verified at the DNS client. These claims follow
the definition of a JWT claim (Secion 4 of [RFC7519]) and are encoded
as defined by the JWS Payload (Section 3 of [RFC7515]).
PAT 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].
6.1. JWT Defined Claims
6.1.1. '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].
6.1.2. '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 PAT object should expire after a reasonable
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duration. A short expiration time for the PAT object periodically
reaffirms the policy information of the DNS server to the DNS client
and ensures the DNS client does not use outdated policy information.
If the DNS client knows the PAT object has expired, it should make
another request to get the new PAT object from the DNS server.
6.2. PAT Specific Claims
6.2.1. DNS Server Identity Claims
The DNS server identity is represented by a claim that is required
for PAT: 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).
6.2.1.1. '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.
6.2.1.2. 'uri' - URI Identity
If the DNS server identity is of the form URI, as defined in
[RFC3986], the claim name representing the identity MUST be 'uri' and
the claim value is the URI form of the DNS server identity.
As a reminder, if DoH is supported by the DNS server, the DNS client
uses the https URI scheme (Section 3 of [RFC8484]).
6.2.2. 'policyinfo' (Policy Information) Claim
The 'policyinfo' claim MUST be formatted as a JSON object. The
'policyinfo' claim contains the policy information of the DNS server,
it includes the following attributes:
filtering: If the DNS server changes some of the answers that it
returns based on policy criteria, such as to prevent access to
malware sites or objectionable content. This optional attribute
has the following structure:
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malwareblocking: The DNS server offers malware blocking service.
If access to domains is blocked on threat data, the parameter
value is set to 'true'.
policyblocking: If access to domains is blocked on a blacklist or
objectionable content, the parameter value is set to 'true'.
qnameminimization: If the DNS server implements QNAME minimisation
[RFC7816] to improve DNS privacy. If the parameter value is set
to 'true', QNAME minimisation is supported by the DNS server.
This is a mandatory attribute.
privacyurl: A URL that points to the privacy policy information of
the DNS server. This is a mandatory attribute.
auditurl: A URL that points to the security assessment report of the
DNS server by a third party auditor. This is an optional
attribute.
6.2.3. Example
Figure 2 shows an example of policy information.
{
"server":{
"adn":["example.com"]
},
"iat":1443208345,
"exp":1443640345,
"policyinfo": {
"filtering": {
"malwareblocking": true,
"policyblocking": false
},
"qnameminimization":false,
"privacyurl": "https://example.com/commitment-to-privacy/"
}
}
Figure 2: An Example of Policy Information
7. PAT Signature
The signature of the PAT is created as specified in Section 5.1 of
[RFC7515] (Steps 1 through 6). PAT MUST use the JWS Protected
Header.
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For the JWS Payload and the JWS Protected Header, the lexicographic
ordering and white space rules described in Section 5 and Section 6,
and JSON serialization rules in Section 9 MUST be followed.
The PAT 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 policy information is attested using "Organization Validation"
(OV) or "Extended Validation" (EV) certificates to avoid bad actors
taking advantage of this mechanism to advertise DoH/DoT servers for
illegitimate and fraudulent purposes meant to trick DNS clients into
believing that they are using a legitimate DoT/DoH 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 PAT 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 policy.
Appendix A provides an example of how to follow the steps to create
the JWS Signature.
JWS JSON serialization (Step 7 in Section 5.1 of [RFC7515]) is
supported for PAT to enable multiple signatures to be applied to the
PAT object. For example, the PAT 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 PAT Token.
8. Extending PAT
PAT includes the minimum set of claims needed to securely assert the
policy information of the DNS server. JWT supports a mechanism to
add additional asserted or signed information by simply adding new
claims. PAT 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 PAT object cannot
assume that the DNS client will understand the new claims.
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9. 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.
5. Encoding rules MUST be applied recursively to member values and
array values.
9.1. Example PAT Deterministic JSON Form
This section demonstrates the deterministic JSON serialization for
the example PAT Payload shown in Section 6.2.3.
The initial JSON object is shown in Figure 3.
{
"server":{
"adn":["example.com"]
},
"iat":1443208345,
"exp":1443640345,
"policyinfo": {
"qnameminimization":false,
"privacyurl": "https://example.com/commitment-to-privacy/"
}
}
Figure 3: Initial JSON Object
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The parent members of the JSON object are as follows, in
lexicographic order: "exp", "iat", "policyinfo", "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,
"policyinfo":{"privacyurl":"https://example.com/commitment-to-privacy/",
"qnameminimization":false},"server":{"adn":["example.com"]}}
Figure 4: Deterministic JSON Form
10. Privacy Considerations
Users are expected to indicate to their system in some way that they
trust certain PAT signers (e.g., if working for Example, Inc., the
user's system is configured to trust "example.com" signing the PAT).
By doing so, the DNS client can automatically discover DoT/DoH server
in specific networks, validate the PAT signature and the user can
check if the human readable privacy policy information of the DNS
server complies with user's privacy needs, prior to using that DoT/
DoH server for DNS queries.
The DNS client MUST retrieve the human-readable privacy statement
from the 'privacyurl' attribute to assist with that decision (e.g.,
display the privacy statement when it changes, show differences in
previously-retrieved version, etc.). With the steps above, user
consent is obtained prior to using a DoT/DoH server.
11. Security Considerations
The use of PAT 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 policy information of the DNS server being asserted. Bad
actors can host DNS-over-TLS and DNS-over-HTTPS servers, and claim
the servers offer privacy but exactly do the opposite to invade the
privacy of the user. Bad actor can get a domain name, host DNS-over-
TLS and DNS-over-HTTPS servers, and get the DNS server certificate
signed by a CA. The policy information will have to be attested
using OV/EV certificates or a PAT object signer trusted by the DNS
client to prevent the attack.
If the PAT 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 policy of the DNS server can cause a
disagreement between the auditor and the DNS server operation, hence
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the PAT object needs to be also asserted by the domain hosting the
DNS server. In addition, the PAT object needs to have a short
expiration time (e.g., 7 days) to ensure the DNS server's domain re-
asserts the policy information and limits the damage from change in
policy and mis-issuance.
12. IANA Considerations
12.1. Media Type Registration
12.1.1. Media Type Registry Contents Additions Requested
This section registers the 'application/pat' 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 PAT defined JWT.
o Type name: application
o Subtype name: pat
o Required parameters: n/a
o Optional parameters: n/a
o Encoding considerations: 8bit; application/pat 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: [TODO 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
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o Restrictions on usage: none
o Author: Tirumaleswar Reddy, kondtir@gmail.com
o Change Controller: IESG
o Provisional registration? No
12.2. JSON Web Token Claims Registration
12.2.1. Registry Contents Additions Requested
o Claim Name: 'server'
o Claim Description: DNS server identity
o Change Controller: IESG
o Specification Document(s): Section 6.2.1 of [TODO this document]
o Claim Name: 'policyinfo'
o Claim Description: Policy information of DNS server.
o Change Controller: IESG
o Specification Document(s): Section 6.2.2 of [TODO this document]
12.3. DNS Resolver Information Registration
IANA will add the names filtering, qnameminimization, privacyurl and
auditurl to the DNS Resolver Information registry defined in
Section 5.2 of [I-D.ietf-dnsop-resolver-information].
13. Acknowledgments
This specification leverages some of the work that has been done in
[RFC8225]. Thanks to Ted Lemon, Paul Wouters and Shashank Jain for
the discussion and comments.
14. References
14.1. Normative References
[I-D.ietf-dnsop-resolver-information]
Sood, P., Arends, R., and P. Hoffman, "DNS Resolver
Information Self-publication", draft-ietf-dnsop-resolver-
information-01 (work in progress), February 2020.
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[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>.
[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>.
[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>.
[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>.
[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>.
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[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>.
14.2. Informative References
[I-D.ietf-dnsop-extended-error]
Kumari, W., Hunt, E., Arends, R., Hardaker, W., and D.
Lawrence, "Extended DNS Errors", draft-ietf-dnsop-
extended-error-14 (work in progress), January 2020.
[I-D.ietf-dprive-bcp-op]
Dickinson, S., Overeinder, B., Rijswijk-Deij, R., and A.
Mankin, "Recommendations for DNS Privacy Service
Operators", draft-ietf-dprive-bcp-op-08 (work in
progress), January 2020.
[I-D.reddy-dprive-bootstrap-dns-server]
Reddy.K, T., Wing, D., Richardson, M., and M. Boucadair,
"A Bootstrapping Procedure to Discover and Authenticate
DNS-over-(D)TLS and DNS-over-HTTPS Servers", draft-reddy-
dprive-bootstrap-dns-server-07 (work in progress),
February 2020.
[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>.
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[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>.
[UNICODE] The Unicode Consortium, "The Unicode Standard", June 2016,
<http://www.unicode.org/versions/latest/>.
Appendix A. Example ES256 based PAT JWS Serialization and Signature
For PAT, 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 PAT.
Step 1 for JWS references the JWS Payload, an example PAT Payload is
as follows:
{
"server":{
"adn":["example.com"]
},
"iat":1443208345,
"exp":1443640345,
"policyinfo": {
"filtering": {
"malwareblocking": true,
"policyblocking": false
},
"qnameminimization":false,
"privacyurl": "https://example.com/commitment-to-privacy/"
}
}
This would be serialized to the form (with line break used for
display purposes only):
{"exp":1443640345,"iat":1443208345,"policyinfo":{
"filtering":{"malwareblocking": true,"policyblocking": false},
"privacyurl":"https://example.com/commitment-to-privacy/",
"qnameminimization":false},"server":{"adn":["example.com"]}}
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Step 2 Computes the BASE64URL(JWS Payload) producing this value (with
line break used for display purposes only):
eyJleHAiOjE0NDM2NDAzNDUsImlhdCI6MTQ0MzIwODM0NSwicG9saWN5aW5mbyI6e
yJmaWx0ZXJpbmciOnsibWFsd2FyZWJsb2NraW5nIjp0cnVlLCJwb2xpY3libG9ja2
luZyI6ZmFsc2V9LCJwcml2YWN5dXJsIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9jb21
taXRtZW50LXRvLXByaXZhY3kvIiwicW5hbWVtaW5pbWl6YXRpb24iOmZhbHNlfSwi
c2VydmVyIjp7ImFkbiI6WyJleGFtcGxlLmNvbSJdfX0
For Step 3, an example PAT Protected Header comprising the JOSE
Header is as follows:
{
"alg":"ES256",
"typ":"pat",
"x5u":"https://cert.example.com/pat.cer"
}
This would be serialized to the form (with line break used for
display purposes only):
{"alg":"ES256","typ":"pat","x5u":"https://cert.example.com
/pat.cer"}
Step 4 Performs the BASE64URL(UTF8(JWS Protected Header)) operation
and encoding produces this value (with line break used for display
purposes only):
eyJhbGciOiJFUzI1NiIsInR5cCI6InBhdCIsIng1dSI6Imh0dHBzOi8vY2VydC5l
eGFtcGxlLmNvbS9wYXQuY2VyIn0
Step 5 and Step 6 performs the computation of the digital signature
of the PAT Signing Input ASCII(BASE64URL(UTF8(JWS Protected
Header)) || '.' || BASE64URL(JWS Payload)) using ES256 as the
algorithm and the BASE64URL(JWS Signature).
4vQEAF_Vlp1Tr6sJmS4pnIKDRmIjH8EZzY5BMT2qJCHD8PmjBktWVnlmbmyHs05G
KauRBdIFnfp3oDPbE0Jq4w
Step 8 describes how to create the final PAT token, concatenating the
values in the order Header.Payload.Signature with period ('.')
characters. For the above example values this would produce the
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following (with line breaks between period used for readability
purposes only):
eyJhbGciOiJFUzI1NiIsInR5cCI6InBhdCIsIng1dSI6Imh0dHBzOi8vY2VydC5l
eGFtcGxlLmNvbS9wYXQuY2VyIn0
.
eyJleHAiOjE0NDM2NDAzNDUsImlhdCI6MTQ0MzIwODM0NSwicG9saWN5aW5mbyI6e
yJmaWx0ZXJpbmciOnsibWFsd2FyZWJsb2NraW5nIjp0cnVlLCJwb2xpY3libG9ja2
luZyI6ZmFsc2V9LCJwcml2YWN5dXJsIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9jb21
taXRtZW50LXRvLXByaXZhY3kvIiwicW5hbWVtaW5pbWl6YXRpb24iOmZhbHNlfSwi
c2VydmVyIjp7ImFkbiI6WyJleGFtcGxlLmNvbSJdfX0
.
4vQEAF_Vlp1Tr6sJmS4pnIKDRmIjH8EZzY5BMT2qJCHD8PmjBktWVnlmbmyHs05G
KauRBdIFnfp3oDPbE0Jq4w
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.
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{
"server":{
"adn":["example.com"]
},
"iat":1443208345,
"exp":1443640345,
"policyinfo": {
"filtering": {
"malwareblocking": true,
"policyblocking": false
},
"qnameminimization":false,
"privacyurl": "https://example.com/commitment-to-privacy/"
}
}
This would be serialized to the form (with line break used for
display purposes only):
{"exp":1443640345,"iat":1443208345,"policyinfo":{
"filtering":{"malwareblocking": true,"policyblocking": false},
"privacyurl":"https://example.com/commitment-to-privacy/",
"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:
{
"alg":"ES384",
"typ":"pat",
"x5u":"https://cert.audit-example.com/pat.cer"
}
The complete JWS JSON Serialization for these values is as follows
(with line breaks within values for display purposes only):
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{
"payload":
"eyJleHAiOjE0NDM2NDAzNDUsImlhdCI6MTQ0MzIwODM0NSwicG9saWN5aW5mbyI6
eyJmaWx0ZXJpbmciOnsibWFsd2FyZWJsb2NraW5nIjp0cnVlLCJwb2xpY3libG9j
a2luZyI6ZmFsc2V9LCJwcml2YWN5dXJsIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9j
b21taXRtZW50LXRvLXByaXZhY3kvIiwicW5hbWVtaW5pbWl6YXRpb24iOmZhbHNl
fSwic2VydmVyIjp7ImFkbiI6WyJleGFtcGxlLmNvbSJdfX0",
"signatures":[
{"protected":"eyJhbGciOiJFUzI1NiIsInR5cCI6InBhdCIsIng1dSI6Imh0dHB
zOi8vY2VydC5leGFtcGxlLmNvbS9wYXQuY2VyIn0",
"signature": "4vQEAF_Vlp1Tr6sJmS4pnIKDRmIjH8EZzY5BMT2qJCHD8PmjBk
tWVnlmbmyHs05GKauRBdIFnfp3oDPbE0Jq4w"},
{"protected":"eyJhbGciOiJFUzM4NCIsInR5cCI6InBhdCIsIng1dSI6Imh0dHB
zOi8vY2VydC5hdWRpdC1leGFtcGxlLmNvbS9wYXQuY2VyIn0",
"signature":666ag_mAqDa3Oyxo1DGXUocr0MmRjpXwq8kWp1S21mvs2-kPCIq3
0xsBJt4apy-sq3VyJgIqzjijoFYURhHvupF0obo-IFUGSZ1YHBCX_MiyBwJQJjtp
S91ujDatRTtZ"}]
}
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
Tirumaleswar Reddy
McAfee, Inc.
Embassy Golf Link Business Park
Bangalore, Karnataka 560071
India
Email: kondtir@gmail.com
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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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