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In: Auth48done
STIR                                                            C. Wendt
Internet-Draft                                                   Comcast
Intended status: Standards Track                             J. Peterson
Expires: August 13, 2017                                    Neustar Inc.
                                                       February 09, 2017


                  Personal Assertion Token (PASSporT)
                      draft-ietf-stir-passport-11

Abstract

   This document defines a method for creating and validating a token
   that cryptographically verifies an originating identity, or more
   generally a URI or telephone number representing the originator of
   personal communications.  The PASSporT token is cryptographically
   signed to protect the integrity of the identity the originator and to
   verify the assertion of the identity information at the destination.
   The cryptographic signature is defined with the intention that it can
   confidently verify the originating persona even when the signature is
   sent to the destination party over an insecure channel.  PASSporT is
   particularly useful for many personal communications applications
   over IP networks and other multi-hop interconnection scenarios where
   the originating and destination parties may not have a direct trusted
   relationship.

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 http://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 August 13, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://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 extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  PASSporT Token Overview . . . . . . . . . . . . . . . . . . .   4
   4.  PASSporT Header . . . . . . . . . . . . . . . . . . . . . . .   5
     4.1.  "typ" (Type) Header Parameter . . . . . . . . . . . . . .   5
     4.2.  "alg" (Algorithm) Header Parameter  . . . . . . . . . . .   5
     4.3.  "x5u" (X.509 URL) Header Parameter  . . . . . . . . . . .   5
     4.4.  Example PASSporT header . . . . . . . . . . . . . . . . .   6
   5.  PASSporT Payload  . . . . . . . . . . . . . . . . . . . . . .   6
     5.1.  JWT defined claims  . . . . . . . . . . . . . . . . . . .   6
       5.1.1.  "iat" - Issued At claim . . . . . . . . . . . . . . .   6
     5.2.  PASSporT specific claims  . . . . . . . . . . . . . . . .   6
       5.2.1.  Originating and Destination Identity Claims . . . . .   7
       5.2.2.  "mky" - Media Key claim . . . . . . . . . . . . . . .   8
   6.  PASSporT Signature  . . . . . . . . . . . . . . . . . . . . .  10
   7.  Compact form of PASSporT  . . . . . . . . . . . . . . . . . .  10
     7.1.  Example Compact form PASSporT Token . . . . . . . . . . .  11
   8.  Extending PASSporT  . . . . . . . . . . . . . . . . . . . . .  11
     8.1.  "ppt" (PASSporT) header parameter . . . . . . . . . . . .  12
     8.2.  Example extended PASSporT header  . . . . . . . . . . . .  12
     8.3.  Extended PASSporT Claims  . . . . . . . . . . . . . . . .  13
   9.  Deterministic JSON Serialization  . . . . . . . . . . . . . .  13
     9.1.  Example PASSport deterministic JSON form  . . . . . . . .  14
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  15
     10.1.  Avoidance of replay and cut and paste attacks  . . . . .  15
     10.2.  Solution Considerations  . . . . . . . . . . . . . . . .  15
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
     11.1.  Media Type Registration  . . . . . . . . . . . . . . . .  16
       11.1.1.  Media Type Registry Contents Additions Requested . .  16
     11.2.  JSON Web Token Claims Registration . . . . . . . . . . .  17
       11.2.1.  Registry Contents Additions Requested  . . . . . . .  17
     11.3.  JSON Web Signature and Encryption Header Parameter
            Registry . . . . . . . . . . . . . . . . . . . . . . . .  18
       11.3.1.  Registry Contents Additions Requested  . . . . . . .  18
     11.4.  PASSporT Extension Registry Request  . . . . . . . . . .  18
   12. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  18



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   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  18
     13.2.  Informative References . . . . . . . . . . . . . . . . .  20
   Appendix A.  Example ES256 based PASSporT JWS Serialization and
                Signature  . . . . . . . . . . . . . . . . . . . . .  20
     A.1.  X.509 Private Key in PKCS#8 format for ES256 Example**  .  22
     A.2.  X.509 Public Key for ES256 Example**  . . . . . . . . . .  22
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  22

1.  Introduction

   In today's IP-enabled telecommunications world, there is a growing
   concern about the ability to trust incoming invitations for
   communications sessions, including video, voice and messaging
   [RFC7340].  As an example, modern telephone networks provide the
   ability to spoof the calling party telephone number for many
   legitimate purposes including providing network features and services
   on the behalf of a legitimate telephone number.  However, as we have
   seen, bad actors have taken advantage of this ability for
   illegitimate and fraudulent purposes meant to trick telephone users
   to believe they are someone they are not.  This problem can be
   extended to many emerging forms of personal communications.

   This document defines a method for creating and validating a token
   that cryptographically verifies an originating identity, or more
   generally a URI or telephone number representing the originator of
   personal communications.  Through extensions defined in this
   document, in Section 8, other information relevant to the personal
   communications can also be added to the token.  The goal of PASSporT
   is to provide a common framework for signing originating identity
   related information in an extensible way.  Additionally, this
   functionality is independent of any specific personal communications
   signaling call logic, so that the assertion of originating identity
   related information can be implemented in a flexible way and can be
   used in applications including end-to-end applications that require
   different signaling protocols or gateways between different
   communications systems.  It is anticipated that signaling protocol
   specific guidance will be provided in other related documents and
   specifications to specify how to use and transport PASSporT tokens,
   however this is intentionally out of scope for this document.

   [I-D.ietf-stir-rfc4474bis] provides details of the use of PASSporT
   within SIP [RFC3261] signaling protocol for the signing and
   verification of telephone numbers and SIP URIs.







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2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

3.  PASSporT Token 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 conveniently
   accommodate asserted originating identity information and is easily
   extensible for extension mechanisms defined below.  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.  JWT defines a set of claims that are represented
   by specified JSON objects which can be extended with custom keys for
   specific applications.  The next sections define the header and
   claims that MUST be minimally used with JWT and JWS for PASSporT.

   PASSporT specifically uses this token format and defines claims that
   convey the identity of the origination and destination of personal
   communications.  The originating identity, the primary value asserted
   in a PASSporT object represents the identity of the calling party or
   the initiator of a personal communications session.  The signer of a
   PASSporT object may or may not correspond to the origination
   identity.  For a given application's use or using protocol of
   PASSporT the creation of the PASSporT object is performed by an
   entity that is authoritative to assert the callers identity.  This
   authority is represented by the certificate credentials and the
   signature and PASSporT object is created and initiated to the
   destination(s) at the applications choice of authoritative point(s)
   in the network.  For example, the PASSporT object could be created at
   a device that has authenticated with a user, or at a network entity
   with an authenticated trust relationship with that device and it's
   user.  Destination identities represent the intended destination of
   the personal communications, i.e. the identity(s) being called by the
   caller.  The destination point(s) determined by the application need
   to have the capability to verify the PASSporT token and the digital
   signature.  The PASSporT associated certificate is used to validate
   the authority of the originating signer, generally via a certificate
   chain to the trust anchor for that application.




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4.  PASSporT Header

   The JWS token header is a JOSE header, [RFC7515] Section 4, that
   defines the type and encryption algorithm used in the token.

   PASSporT header should include, at a minimum, the header parameters
   defined in the next three subsections.

4.1.  "typ" (Type) Header Parameter

   The "typ" (Type) Header Parameter is defined in JWS [RFC7515]
   Section 4.1.9. to declare the media type of the complete JWS.

   For PASSporT Token the "typ" header MUST be the string "passport".
   This represents that the encoded token is a JWT of type passport.

4.2.  "alg" (Algorithm) Header Parameter

   The "alg" (Algorithm) Header Parameter is defined in JWS [RFC7515]
   Section 4.1.1.  This definition includes the ability to specify the
   use of a cryptographic algorithm for the signature part of the JWS.
   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 PASSporT tokens and their
   digital signatures, implementations MUST support ES256 as defined in
   JWA [RFC7518] Section 3.4.  Implementations MAY support other
   algorithms registered in the JSON Web Signature and Encryption
   Algorithms registry created by [RFC7518].  The contents 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 PASSporT tokens may likewise be
   updated in future updates to this document.

   Implementations of PASSporT digital signatures using ES256 as defined
   above SHOULD use deterministic ECDSA if/when supported for the
   reasons stated in [RFC6979].

4.3.  "x5u" (X.509 URL) Header Parameter

   As defined in JWS [RFC7515] Section 4.1.5., 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 JWS [RFC7515] section 4.1.5, this would correspond to
   an HTTPS or DNSSEC resource using integrity protection.




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4.4.  Example PASSporT header

   An example of the header, would be the following, including the
   specified passport type, ES256 algorithm, and a URI referencing the
   network location of the certificate needed to validate the PASSporT
   signature.

   {
     "typ":"passport",
     "alg":"ES256",
     "x5u":"https://cert.example.org/passport.cer"
   }

5.  PASSporT Payload

   The token claims consist of the information which needs to be
   verified at the destination party.  These claims follow the
   definition of a JWT claim [RFC7519] Section 4 and are encoded as
   defined by the JWS Payload [RFC7515] Section 3.

   PASSporT defines the use of a standard JWT defined claim as well as
   custom claims corresponding to the two parties associated with
   personal communications, the originator and destination as detailed
   below.

   Any claim names MUST use the US-ASCII character set.  Any claim
   values can container characters that are outside the US-ASCII range,
   however MUST follow the default JSON serialization defined in
   [RFC7519] Section 7.

5.1.  JWT defined claims

5.1.1.  "iat" - Issued At claim

   The JSON claim MUST include the "iat" [RFC7519] Section 4.1.6 defined
   claim Issued At.  As defined the "iat" should be set to the date and
   time of issuance of the JWT and MUST the origination of the personal
   communications.  The time value should be of the format defined in
   [RFC7519] Section 2 NumericDate.  This is included for securing the
   token against replay and cut and paste attacks, as explained further
   in the security considerations in Section 10.

5.2.  PASSporT specific claims








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5.2.1.  Originating and Destination Identity Claims

   The origination and destination identities are represented by two
   claims that are required for PASSporT, the "orig" and "dest" claims.
   Both "orig" and "dest" 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.  Currently, these identities can be
   represented as either telephone numbers or Uniform Resource
   Indicators (URIs).

   The "orig" claim is a JSON object with the claim name of "orig" and a
   claim value which is a JSON object representing the asserted identity
   of any type (currently either "tn" or "uri") of the originator of the
   personal communications signaling.  There MUST be exactly one "orig"
   claim with exactly one identity claim object in a PASSporT object.

   Note, as explained in Section 3, the originating identity represents
   the calling party and may or may not correspond to the authoritative
   signer of the token.

   The "dest" is a JSON object with the claim name of "dest" and MUST
   have at least have one identity claim object.  The "dest" claim value
   is an array containing one or more identity claim JSON objects
   representing the destination identities of any type (currently "tn"
   or "uri").  If the "dest" claim value array contains both "tn" and
   "uri" claim names, the JSON object should list the "tn" array first
   and the "uri" array second.  Within the "tn" and "uri" arrays, the
   identity strings should be put in lexicographical order including the
   scheme-specific portion of the URI characters.

   Note, as explained in Section 3, the destination identity represents
   the called party and may or may not correspond to the authoritative
   party verifying the token signature.

5.2.1.1.  "tn" - Telephone Number identity

   If the originating or destination identity is a telephone number, the
   claim name representing the identity MUST be "tn".

   The claim value for the "tn" claim is the telephone number and MUST
   be canonicalized according to the procedures specified in
   [I-D.ietf-stir-rfc4474bis] Section 8.3.








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5.2.1.2.  "uri" - URI identity

   If any of the originating or destination identities 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
   identity.

5.2.1.3.  Future identity forms

   We recognize that in the future there may be other standard
   mechanisms for representing identities.  The "orig" and "dest" claims
   currently support "tn" and "uri" but could be extended in the future
   to allow for other identity types with new IANA registered unique
   types to represent these forms.

5.2.1.4.  Examples

   Single originator, with telephone number identity +12155551212, to
   single destination, with URI identity 'sip:alice@example.com',
   example:

   {
     "dest":{"uri":["sip:alice@example.com"]},
     "iat":1443208345,
     "orig":{"tn":"12155551212"}
   }

   Single originator, with telephone number identity +12155551212, to
   multiple destination identities, with telephone number identity
   +12125551212 and two URI identities, sip:alice@example.com and
   sip:bob@example.com, example:

   {
     "dest":{
       "tn":["12125551212"],
       "uri":["sip:alice@example.com",
         "sip:bob@example.net"]
     },
     "iat":1443208345,
     "orig":{"tn":"12155551212"}
   }

5.2.2.  "mky" - Media Key claim

   Some protocols that use PASSporT may also want to protect media
   security keys delivered within their signaling in order to bind those
   keys to the identities established in the signaling layers.  The
   "mky" is an optional PASSporT claim defining the assertion of media



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   key fingerprints carried in SDP [RFC4566] via the "a=fingerprint"
   attribute [RFC4572] Section 5.  This claim can support either a
   single or multiple fingerprints appearing in a single SDP body
   corresponding to one or more media streams offered as defined in
   [I-D.ietf-mmusic-4572-update].

   The "mky" claim MUST be formatted as a JSON object with an array
   including the "alg" and "dig" claims with the corresponding algorithm
   and hexadecimal values.  If there is more than one fingerprint value
   associated with different media streams in SDP, the fingerprint
   values MUST be constructed as a JSON array denoted by bracket
   characters.  For the "dig" claim, the claim value MUST be the hash
   hexadecimal value without any colons.

   The "mky" claim is a JSON object with a claim name of "mky" and a
   claim value of a JSON array denoted by brackets.  The "mky" claim
   value JSON array MUST be constructed as follows:

   1.  Take each "a=fingerprint" lines carried in the SDP.

   2.  Sort the lines based on the UTF8 encoding of the concatenation of
       the "alg" and "dig" claim value strings.

   3.  Encode the array in the order of the sorted lines, where each
       "mky" array element is a JSON object with two elements
       corresponding to the "alg" and "dig" objects, with "alg" first
       and "dig" second.

   An example claim with "mky" claim is as follows:

   For an SDP offer that includes the following fingerprint values,

   a=fingerprint:sha-256 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:
   5D:49:6B:19:E5:7C:AB:3E:4B:65:2E:7D:46:3F:54:42:CD:54:F1
   a=fingerprint:sha-256 02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65
   :2E:7D:46:3F:54:42:CD:54:F1:7A:03:A2:7D:F9:B0:7F:46:19:B2

   the PASSporT Payload object would be:













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   {
     "dest":{"uri":["sip:alice@example.com"]},
     "iat":1443208345,
     "mky":[
       {
         "alg":"sha-256",
         "dig":"021ACC5427ABEB9C533F3E4B652E7D463F5442CD54
           F17A03A27DF9B07F4619B2"
       },
       {
         "alg":"sha-256",
         "dig":"4AADB9B13F82183B540212DF3E5D496B19E57C
           AB3E4B652E7D463F5442CD54F1"
       }
     ],
     "orig":{"tn":"12155551212"}
   }

6.  PASSporT Signature

   The signature of the PASSporT is created as specified by JWS
   [RFC7515] Section 5.1 Steps 1 through 6.  PASSporT 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 9 of
   this document MUST be followed.

   Appendix A of this document has a detailed example of how to follow
   the steps to create the JWS Signature.

   JWS [RFC7515] Section 5.1 Step 7 JWS JSON serialization is not
   supported for PASSporT.

   JWS [RFC7515] Section 5.1 Step 8 describes the method to create the
   final JWS Compact Serialization form of the PASSporT Token.

7.  Compact form of PASSporT

   For a using protocol of PASSporT, the PASSporT Claims as well as the
   PASSporT Header may include redundant or default information that
   could be reconstructed at the destination based on information
   provided in the signaling protocol transporting the PASSporT object.
   In this case, it may be advantageous to have a more compact form of
   PASSporT to save the transmission of the bytes needed to represent
   the header and claims.

   This specification defines the compact form of the PASSporT token, in
   the spirit of form defined in [RFC7515] Appendix F, with the use of



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   '..', two periods to represent the header and claim objects being
   removed, followed by PASSporT signature as defined in Section 6, and
   the need for the destination to reconstruct the header and claim
   objects in order to verify the signature.

   In order to construct the Compact form of the PASSporT string, the
   procedure described in Section 6 with the exception of Step 8
   described in JWS [RFC7515] Section 5.1.  This step would be replaced
   by the following construction of the compact form of PASSporT,
   '..' || BASE64URL(JWS Signature).

   The using protocol of the compact form of PASSporT MUST be
   accompanied by a specification for how the header and claims objects
   can be reconstructed from information in the signaling protocol being
   used.

   Note that the full form of the PASSporT token, containing the entire
   header, payload, and signature, should also use the lexicographic
   ordering and white space serialization rules, particularly in the
   case where some using protocols or interworking between protocols may
   require switching between full and compact forms and maintaining the
   integrity of the signature.

7.1.  Example Compact form PASSporT Token

   The compact form of the following example token (with line breaks
   between period used for readability purposes only)

   eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1IjoiaHR0cHM6Ly9j
   ZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9
   .
   eyJkZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhdCI
   6IjE0NDMyMDgzNDUiLCJvcmlnIjp7InRuIjoiMTIxNTU1NTEyMTIifX0
   .
   rq3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYsojN
   CpTzO3QfPOlckGaS6hEck7w

   would be as follows (with line breaks between period used for
   readability purposes only)

   ..rq3pjT1hoRwakEGjHCnWSwUnshd0-zJ6F1VOgFWSjHBr8Qjpjlk-cpFYpFYsojN
   CpTzO3QfPOlckGaS6hEck7w

8.  Extending PASSporT

   PASSporT includes the bare minimum set of claims needed to securely
   assert the originating identity and support the secure properties
   discussed in various parts of this document.  JWT supports a straight



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   forward way to add additional asserted or signed information by
   simply adding new claims.  PASSporT can be extended beyond the
   defined base set of claims to represent other information requiring
   assertion or validation beyond the originating identity itself as
   needed.

8.1.  "ppt" (PASSporT) header parameter

   Any using protocol can extend the payload of PASSporT with additional
   JWT claims.  JWT claims are managed by an existing IANA registry as
   defined in [RFC7519] Section 10.1.  Implementations of PASSporT MUST
   support the baseline claims defined in Section 5.2, and MAY support
   extended claims.  If it is necessary for an extension to PASSporT to
   require that a relying party support a particular extended claim or
   set of claims in the PASSporT object, it can do so by specifying a
   "ppt" element for the PASSporT JOSE header.  All values of "ppt" need
   to be defined in a specification which associates the new value of
   the "ppt" element with the required claims and behaviors.  Relying
   parties MUST fail to validate PASSporT objects containing an
   unsupported "ppt".

   Using protocols MUST explicitly define the how each claim is carried
   in the using protocol and the rules for how the header and payload
   objects are constructed beyond the lexicographical and serialization
   rules defined in this document.

   Using protocols that carry the compact form of PASSporT, defined in
   Section 7, instead of the full form MUST use only mandatory
   extensions signaled with "ppt" - if a using protocol were to add
   additional optional claims to a PASSporT object it carried in compact
   form, relying parties would have no way to reconstruct the token.
   Moreover, using protocols that support the compact form of PASSporT
   MUST have some field to signal "ppt" to relying parties, as the
   compact form of PASSporT omits the JOSE header.

8.2.  Example extended PASSporT header

   An example header with a PASSporT extension type of "foo" is as
   follows:

   {
     "alg":"ES256",
     "ppt":"foo",
     "typ":"passport",
     "x5u":"https://tel.example.org/passport.cer"
   }





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8.3.  Extended PASSporT Claims

   Specifications that define extensions to the PASSporT mechanism MUST
   explicitly specify what claims they include beyond the base set of
   claims from this document, the order in which they will appear, and
   any further information necessary to implement the extension.  All
   extensions MUST include the baseline PASSporT claim elements
   specified in Section 5; claims may only be appended to the claims
   object specified; they can never be removed or re-ordered.
   Specifying new claims follows the baseline JWT procedures ([RFC7519]
   Section 10.1).  Understanding an extension or new claims defined by
   the extension on the destination verification of the PASSporT token
   is optional.  The creator of a PASSporT object cannot assume that
   destination systems will understand any given extension.
   Verification of PASSporT tokens by destination systems that do
   support an extension may then trigger appropriate application-level
   behavior in the presence of an extension; authors of extensions
   should provide appropriate extension-specific guidance to application
   developers on this point.

   An example set of extended claims, extending the first example in
   Section 5.2.1.4 using "bar" as the newly defined claim would be as
   follows:

   {
     "bar":"beyond all recognition"
     "dest":{"uri":["sip:alice@example.com"]},
     "iat":1443208345,
     "orig":{"tn":"12155551212"}
   }

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 Step 1 of [RFC7638].

   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.



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   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.

   Note: For any PASSporT extension claims, member names within the
   scope of a JSON object MUST NOT be equal to other member names,
   otherwise serialization will not be deterministic.

9.1.  Example PASSport deterministic JSON form

   This section demonstrate the deterministic JSON serialization for the
   example PASSporT Payload shown in Section 5.2.1.4.

   The initial JSON object is shown here:

   {
     "dest":{"uri":["sip:alice@example.com"]},
     "orig":{"tn":"12155551212"}
     "iat":1443208345,
     "mky":[
       {
         "alg":"sha-256",
         "dig":"021ACC5427ABEB9C533F3E4B652E7D463F5442CD54
           F17A03A27DF9B07F4619B2"
       },
       {
         "alg":"sha-256",
         "dig":"4AADB9B13F82183B540212DF3E5D496B19E57C
           AB3E4B652E7D463F5442CD54F1"
       }
     ],
   }

   The parent members of the JSON object are as follows:

   o  "dest"

   o  "orig"

   o  "iat"

   o  "mky"

   Their lexicographic order is:



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   o  "dest"

   o  "iat"

   o  "mky"

   o  "orig"

   The final constructed deterministic JSON serialization
   representation, with whitespace and line breaks removed, (with line
   breaks used for display purposes only) is:

   {"dest":{"uri":["sip:alice@example.com"],"iat":1443208345,"mky":
   [{"alg":"sha-256","dig":"021ACC5427ABEB9C533F3E4B652E7D463F5442CD5
   4F17A03A27DF9B07F4619B2"},{"alg":"sha-256","dig":"4AADB9B13F82183B5
   40212DF3E5D496B19E57CAB3E4B652E7D463F5442CD54F1"}],
   "orig":{"tn":"12155551212"}}

10.  Security Considerations

10.1.  Avoidance of replay and cut and paste attacks

   There are a number of security considerations for use of the token
   for avoidance of replay and cut and paste attacks.  PASSporT tokens
   SHOULD only be sent with application level protocol information (e.g.
   for SIP an INVITE as defined in [RFC3261]) corresponding to the
   required fields in the token.  A uniqueness of the set of token
   claims and token signature is constructed using the originating
   identity being asserted with the 'orig' claim along with the
   following two claims:

   o  'iat' claim should correspond to a date/time the message was
      originated.  It should also be within a relative time that is
      reasonable for clock drift and transmission time characteristics
      associated with the application using the PASSporT token.
      Therefore, validation of the token should consider date and time
      correlation, which could be influenced by signaling protocol
      specific use and network time differences.

   o  'dest' claim is included to prevent the valid re-use of a
      previously originated message to send to another destination
      party.

10.2.  Solution Considerations

   The use of PASSporT tokens 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



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   attest to the identity being asserted.  The following considerations
   should be recognized when using PASSporT:

   o  The use of this token should not, in it's own right, be considered
      a full solution for absolute non-repudiation of the identity being
      asserted.

   o  In many applications, the end user represented by the asserted
      identity represents and signer may not be one in the same.  For
      example, when a service provider signs and validates the token on
      the behalf of the user consuming the service, the provider MUST
      have an authenticated and secure relationship with the end user or
      the device initiating and terminating the communications
      signaling.

   o  Applications that use PASSporT should ensure the verification of
      the signature includes the means of verifying the signer is
      authoritative through the use of an application or service
      specific set of common trust anchors for the application.

11.  IANA Considerations

11.1.  Media Type Registration

11.1.1.  Media Type Registry Contents Additions Requested

   This section registers the "application/passport" 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
   PASSporT defined JWT.

   o  Type name: application

   o  Subtype name: passport

   o  Required parameters: n/a

   o  Optional parameters: n/a

   o  Encoding considerations: 8bit; application/passport 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




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   o  Published specification: [RFCThis]

   o  Applications that use this media type: STIR and other applications
      that require identity related assertion

   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: Chris
      Wendt, chris-ietf@chriswendt.net

   o  Intended usage: COMMON

   o  Restrictions on usage: none

   o  Author: Chris Wendt, chris-ietf@chriswendt.net

   o  Change Controller: IESG

   o  Provisional registration?  No

11.2.  JSON Web Token Claims Registration

11.2.1.  Registry Contents Additions Requested

   o  Claim Name: "orig"

   o  Claim Description: Originating Identity String

   o  Change Controller: IESG

   o  Specification Document(s): Section 5.2.1 of [RFCThis]

   o  Claim Name: "dest"

   o  Claim Description: Destination Identity String

   o  Change Controller: IESG

   o  Specification Document(s): Section 5.2.1 of [RFCThis]

   o  Claim Name: "mky"

   o  Claim Description: Media Key Fingerprint String



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   o  Change Controller: IESG

   o  Specification Document(s): Section 5.2.2 of [RFCThis]

11.3.  JSON Web Signature and Encryption Header Parameter Registry

11.3.1.  Registry Contents Additions Requested

   Header Parameter Name: "ppt"

   o  Header Parameter Description: PASSporT extension identifier

   o  Header Parameter Usage Location(s): JWS

   o  Change Controller: IESG

   o  Specification Document(s): Section 8.1 of [RFCThis]

11.4.  PASSporT Extension Registry Request

   The IANA is requested to create a new PASSporT Type registry for
   'ppt' parameter values.  That parameter and its values are defined in
   Section 8.1.  New registry entries must contain the name of the 'ppt'
   parameter value and the specification in which the value is
   described.  The policy for this registry is Specification Required.

12.  Acknowledgements

   Particular thanks to members of the ATIS and SIP Forum NNI Task Group
   including Jim McEchern, Martin Dolly, Richard Shockey, John Barnhill,
   Christer Holmberg, Victor Pascual Avila, Mary Barnes, Eric Burger for
   their review, ideas, and contributions also thanks to Henning
   Schulzrinne, Russ Housley, Alan Johnston, Richard Barnes, Mark
   Miller, Ted Hardie, Dave Crocker, Robert Sparks, Jim Schaad for
   valuable feedback on the technical and security aspects of the
   document.  Additional thanks to Harsha Bellur for assistance in
   coding the example tokens.

13.  References

13.1.  Normative References

   [I-D.ietf-mmusic-4572-update]
              Lennox, J. and C. Holmberg, "Connection-Oriented Media
              Transport over TLS in SDP", draft-ietf-mmusic-
              4572-update-13 (work in progress), February 2017.





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   [I-D.ietf-stir-rfc4474bis]
              Peterson, J., Jennings, C., Rescorla, E., and C. Wendt,
              "Authenticated Identity Management in the Session
              Initiation Protocol (SIP)", draft-ietf-stir-rfc4474bis-15
              (work in progress), October 2016.

   [RFC2046]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part Two: Media Types", RFC 2046,
              DOI 10.17487/RFC2046, November 1996,
              <http://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,
              <http://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,
              <http://www.rfc-editor.org/info/rfc3986>.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, DOI 10.17487/RFC4566,
              July 2006, <http://www.rfc-editor.org/info/rfc4566>.

   [RFC4572]  Lennox, J., "Connection-Oriented Media Transport over the
              Transport Layer Security (TLS) Protocol in the Session
              Description Protocol (SDP)", RFC 4572,
              DOI 10.17487/RFC4572, July 2006,
              <http://www.rfc-editor.org/info/rfc4572>.

   [RFC6838]  Freed, N., Klensin, J., and T. Hansen, "Media Type
              Specifications and Registration Procedures", BCP 13,
              RFC 6838, DOI 10.17487/RFC6838, January 2013,
              <http://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, <http://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, <http://www.rfc-editor.org/info/rfc7515>.

   [RFC7518]  Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
              DOI 10.17487/RFC7518, May 2015,
              <http://www.rfc-editor.org/info/rfc7518>.



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   [RFC7519]  Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
              (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
              <http://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, <http://www.rfc-editor.org/info/rfc7638>.

   [UNICODE]  The Unicode Consortium, "The Unicode Standard", June 2016,
              <http://www.unicode.org/versions/latest/>.

13.2.  Informative References

   [RFC3261]  Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
              A., Peterson, J., Sparks, R., Handley, M., and E.
              Schooler, "SIP: Session Initiation Protocol", RFC 3261,
              DOI 10.17487/RFC3261, June 2002,
              <http://www.rfc-editor.org/info/rfc3261>.

   [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,
              <http://www.rfc-editor.org/info/rfc5280>.

   [RFC7340]  Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure
              Telephone Identity Problem Statement and Requirements",
              RFC 7340, DOI 10.17487/RFC7340, September 2014,
              <http://www.rfc-editor.org/info/rfc7340>.

Appendix A.  Example ES256 based PASSporT JWS Serialization and
             Signature

   For PASSporT, 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 PASSporT.

   Step 1 for JWS references the JWS Payload, an example PASSporT
   Payload is as follows:




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   {
     "dest":{"uri":["sip:alice@example.com"]}
     "iat":1471375418,
     "orig":{"tn":"12155551212"}
   }

   This would be serialized to the form (with line break used for
   display purposes only):

   {"dest":{"uri":["sip:alice@example.com"]},"iat":1471375418,
   "orig":{"tn":"12155551212"}}

   Step 2 Computes the BASE64URL(JWS Payload) producing this value (with
   line break used for display purposes only):

   eyJkZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhdCI
   6MTQ3MTM3NTQxOCwib3JpZyI6eyJ0biI6IjEyMTU1NTUxMjEyIn19

   For Step 3, an example PASSporT Protected Header comprising the JOSE
   Header is as follows:

   {
     "alg":"ES256",
     "typ":"passport",
     "x5u":"https://cert.example.org/passport.cer"
   }

   This would be serialized to the form (with line break used for
   display purposes only):

   {"alg":"ES256","typ":"passport","x5u":"https://cert.example.org
     /passport.cer"}

   Step 4 Performs the BASE64URL(UTF8(JWS Protected Header)) operation
   and encoding produces this value (with line break used for display
   purposes only):

   eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1IjoiaHR0cHM6Ly9j
   ZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9

   Step 5 and Step 6 performs the computation of the digital signature
   of the PASSporT Signing Input ASCII(BASE64URL(UTF8(JWS Protected
   Header)) || '.' || BASE64URL(JWS Payload)) using ES256 as the
   algorithm and the BASE64URL(JWS Signature).

   VLBCIVDCaeK6M4hLJb6SHQvacAQVvoiiEOWQ_iUkqk79UD81fHQ0E1b3_GluIkb
   a7UWYRM47ZbNFdOJquE35cw




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   Step 8 describes how to create the final PASSporT 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):

   eyJhbGciOiJFUzI1NiIsInR5cCI6InBhc3Nwb3J0IiwieDV1IjoiaHR0cHM6Ly9j
   ZXJ0LmV4YW1wbGUub3JnL3Bhc3Nwb3J0LmNlciJ9
   .
   eyJkZXN0Ijp7InVyaSI6WyJzaXA6YWxpY2VAZXhhbXBsZS5jb20iXX0sImlhdCI
   6MTQ3MTM3NTQxOCwib3JpZyI6eyJ0biI6IjEyMTU1NTUxMjEyIn19
   .
   VLBCIVDCaeK6M4hLJb6SHQvacAQVvoiiEOWQ_iUkqk79UD81fHQ0E1b3_GluIkb
   a7UWYRM47ZbNFdOJquE35cw

A.1.  X.509 Private Key in PKCS#8 format for ES256 Example**

   -----BEGIN PRIVATE KEY-----
   MIGHAgEAMBMGByqGSM49AgEGCCqGSM49AwEHBG0wawIBAQQgi7q2TZvN9VDFg8Vy
   qCP06bETrR2v8MRvr89rn4i+UAahRANCAAQWfaj1HUETpoNCrOtp9KA8o0V79IuW
   ARKt9C1cFPkyd3FBP4SeiNZxQhDrD0tdBHls3/wFe8++K2FrPyQF9vuh
   -----END PRIVATE KEY----

A.2.  X.509 Public Key for ES256 Example**

   -----BEGIN PUBLIC KEY-----
   MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAE8HNbQd/TmvCKwPKHkMF9fScavGeH
   78YTU8qLS8I5HLHSSmlATLcslQMhNC/OhlWBYC626nIlo7XeebYS7Sb37g==
   -----END PUBLIC KEY-----

Authors' Addresses

   Chris Wendt
   Comcast
   One Comcast Center
   Philadelphia, PA  19103
   USA

   Email: chris-ietf@chriswendt.net


   Jon Peterson
   Neustar Inc.
   1800 Sutter St Suite 570
   Concord, CA  94520
   US

   Email: jon.peterson@neustar.biz



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