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Network Working Group                                           M. Jones
Internet-Draft                                                 Microsoft
Intended status: Standards Track                              D. Balfanz
Expires: June 15, 2012                                            Google
                                                              J. Bradley
                                                             independent
                                                               Y. Goland
                                                               Microsoft
                                                               J. Panzer
                                                                  Google
                                                             N. Sakimura
                                               Nomura Research Institute
                                                               P. Tarjan
                                                                Facebook
                                                       December 13, 2011


                          JSON Web Token (JWT)
                     draft-jones-json-web-token-07

Abstract

   JSON Web Token (JWT) is a means of representing claims to be
   transferred between two parties.  The claims in a JWT are encoded as
   a JSON object that is digitally signed using JSON Web Signature (JWS)
   and/or encrypted using JSON Web Encryption (JWE).

   The suggested pronunciation of JWT is the same as the English word
   "jot".

Requirements Language

   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].

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



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   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 June 15, 2012.

Copyright Notice

   Copyright (c) 2011 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
   (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.
































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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  JSON Web Token (JWT) Overview  . . . . . . . . . . . . . . . .  5
     3.1.  Example JWT  . . . . . . . . . . . . . . . . . . . . . . .  6
   4.  JWT Claims . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     4.1.  Reserved Claim Names . . . . . . . . . . . . . . . . . . .  7
     4.2.  Public Claim Names . . . . . . . . . . . . . . . . . . . .  9
     4.3.  Private Claim Names  . . . . . . . . . . . . . . . . . . . 10
   5.  JWT Header . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   6.  Plaintext JWTs . . . . . . . . . . . . . . . . . . . . . . . . 11
     6.1.  Example Plaintext JWT  . . . . . . . . . . . . . . . . . . 11
   7.  Rules for Creating and Validating a JWT  . . . . . . . . . . . 12
   8.  Cryptographic Algorithms . . . . . . . . . . . . . . . . . . . 15
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 15
   10. Security Considerations  . . . . . . . . . . . . . . . . . . . 15
     10.1. Unicode Comparison Security Issues . . . . . . . . . . . . 16
   11. Open Issues and Things To Be Done (TBD)  . . . . . . . . . . . 16
   12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
     12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
     12.2. Informative References . . . . . . . . . . . . . . . . . . 18
   Appendix A.  Relationship of JWTs to SAML Tokens . . . . . . . . . 19
   Appendix B.  Relationship of JWTs to Simple Web Tokens (SWTs)  . . 19
   Appendix C.  Acknowledgements  . . . . . . . . . . . . . . . . . . 19
   Appendix D.  Document History  . . . . . . . . . . . . . . . . . . 20
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
























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1.  Introduction

   JSON Web Token (JWT) is a compact token format intended for space
   constrained environments such as HTTP Authorization headers and URI
   query parameters.  JWTs encode claims to be transmitted as a JSON
   object (as defined in RFC 4627 [RFC4627]) that is base64url encoded
   and digitally signed and/or encrypted.  Signing is accomplished using
   JSON Web Signature (JWS) [JWS].  Encryption is accomplished using
   JSON Web Encryption (JWE) [JWE].

   The suggested pronunciation of JWT is the same as the English word
   "jot".


2.  Terminology

   JSON Web Token (JWT)  A string consisting of three parts: the Encoded
      JWT Header, the JWT Second Part, and the JWT Third Part, in that
      order, with the parts being separated by period ('.') characters,
      and each part containing base64url encoded content.

   JWT Header  A string representing a JSON object that describes the
      cryptographic operations applied to the JWT.  When the JWT is
      signed, the JWT Header is the JWS Header.  When the JWT is
      encrypted, the JWT Header is the JWE Header.

   Header Parameter Names  The names of the members within the JWT
      Header.

   Header Parameter Values  The values of the members within the JWT
      Header.

   JWT Second Part  When the JWT is signed, the JWT Second Part is the
      Encoded JWS Payload.  When the JWT is encrypted, the JWT Second
      Part is the Encoded JWE Encrypted Key.

   JWT Third Part  When the JWT is signed, the JWT Third Part is the
      Encoded JWS Signature.  When the JWT is encrypted, the JWT Third
      Part is the Encoded JWE Ciphertext.

   JWT Claims Set  A string representing a JSON object that contains the
      claims conveyed by the JWT.  When the JWT is signed, the bytes of
      the UTF-8 representation of the JWT Claims Set are base64url
      encoded to create the Encoded JWS Payload.  When the JWT is
      encrypted, the bytes of the UTF-8 representation of the JWT Claims
      Set are used as the JWE Plaintext.





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   Claim Names  The names of the members of the JSON object represented
      by the JWT Claims Set.

   Claim Values  The values of the members of the JSON object
      represented by the JWT Claims Set.

   Encoded JWT Header  Base64url encoding of the bytes of the UTF-8 RFC
      3629 [RFC3629] representation of the JWT Header.

   Base64url Encoding  For the purposes of this specification, this term
      always refers to the URL- and filename-safe Base64 encoding
      described in RFC 4648 [RFC4648], Section 5, with the (non URL-
      safe) '=' padding characters omitted, as permitted by Section 3.2.
      (See Appendix C of [JWS] for notes on implementing base64url
      encoding without padding.)


3.  JSON Web Token (JWT) Overview

   JWTs represent a set of claims as a JSON object that is base64url
   encoded and digitally signed and/or encrypted.  The JWT Claims Set
   represents this JSON object.  As per RFC 4627 [RFC4627] Section 2.2,
   the JSON object consists of zero or more name/value pairs (or
   members), where the names are strings and the values are arbitrary
   JSON values.  These members are the claims represented by the JWT.

   The member names within the JWT Claims Set are referred to as Claim
   Names.  The corresponding values are referred to as Claim Values.

   The bytes of the UTF-8 representation of the JWT Claims Set are
   signed in the manner described in JSON Web Signature (JWS) [JWS]
   and/or encrypted in the manner described in JSON Web Encryption (JWE)
   [JWE].

   The contents of the JWT Header describe the cryptographic operations
   applied to the JWT Claims Set. If the JWT Header is a JWS Header, the
   claims are signed.  If the JWT Header is a JWE Header, the claims are
   encrypted.

   A JWT is represented as the concatenation of the Encoded JWT Header,
   the JWT Second Part, and the JWT Third Part, in that order, with the
   parts being separated by period ('.') characters.  When signed, the
   three parts of the JWT are the three parts of a JWS used to represent
   the JWT.  When encrypted, the three parts of the JWT are the three
   parts of a JWE used to represent the JWT.






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3.1.  Example JWT

   The following example JWT Header declares that the encoded object is
   a JSON Web Token (JWT) and the JWT is signed using the HMAC SHA-256
   algorithm:
   {"typ":"JWT",
    "alg":"HS256"}

   Base64url encoding the bytes of the UTF-8 representation of the JWT
   Header yields this Encoded JWS Header value, which is used as the
   Encoded JWT Header:
   eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9

   The following is an example of a JWT Claims Set:
   {"iss":"joe",
    "exp":1300819380,
    "http://example.com/is_root":true}

   Base64url encoding the bytes of the UTF-8 representation of the JSON
   Claims Set yields this Encoded JWS Payload, which is used as the JWT
   Second Part (with line breaks for display purposes only):
   eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly
   9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   Signing the Encoded JWS Header and Encoded JWS Payload with the HMAC
   SHA-256 algorithm and base64url encoding the signature in the manner
   specified in [JWS], yields this Encoded JWS Signature, which is used
   as the JWT Third Part:
   dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

   Concatenating these parts in the order Header.Second.Third with
   period characters between the parts yields this complete JWT (with
   line breaks for display purposes only):
   eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
   .
   eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
   cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
   .
   dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk

   This computation is illustrated in more detail in [JWS], Appendix
   A.1.


4.  JWT Claims

   The JWT Claims Set represents a JSON object whose members are the
   claims conveyed by the JWT.  The Claim Names within this object MUST



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   be unique.  Note however, that the set of claims that a JWT must
   contain to be considered valid is context-dependent and is outside
   the scope of this specification.  When used in a security-related
   context, implementations MUST understand and support all of the
   claims present; otherwise, the JWT MUST be rejected for processing.

   There are three classes of JWT Claim Names: Reserved Claim Names,
   Public Claim Names, and Private Claim Names.

4.1.  Reserved Claim Names

   The following claim names are reserved.  None of the claims defined
   in the table below are intended to be mandatory, but rather, provide
   a starting point for a set of useful, interoperable claims.  All the
   names are short because a core goal of JWTs is for the tokens to be
   compact.

   +-------+--------+-------------+------------------------------------+
   | Claim | JSON   | Claim       | Claim Semantics                    |
   | Name  | Value  | Syntax      |                                    |
   |       | Type   |             |                                    |
   +-------+--------+-------------+------------------------------------+
   | exp   | number | IntDate     | The "exp" (expiration time) claim  |
   |       |        |             | identifies the expiration time on  |
   |       |        |             | or after which the token MUST NOT  |
   |       |        |             | be accepted for processing.  The   |
   |       |        |             | processing of the "exp" claim      |
   |       |        |             | requires that the current          |
   |       |        |             | date/time MUST be before the       |
   |       |        |             | expiration date/time listed in the |
   |       |        |             | "exp" claim.  Implementers MAY     |
   |       |        |             | provide for some small leeway,     |
   |       |        |             | usually no more than a few         |
   |       |        |             | minutes, to account for clock      |
   |       |        |             | skew.  This claim is OPTIONAL.     |
   | nbf   | number | IntDate     | The "nbf" (not before) claim       |
   |       |        |             | identifies the time before which   |
   |       |        |             | the token MUST NOT be accepted for |
   |       |        |             | processing.  The processing of the |
   |       |        |             | "nbf" claim requires that the      |
   |       |        |             | current date/time MUST be after or |
   |       |        |             | equal to the not-before date/time  |
   |       |        |             | listed in the "nbf" claim.         |
   |       |        |             | Implementers MAY provide for some  |
   |       |        |             | small leeway, usually no more than |
   |       |        |             | a few minutes, to account for      |
   |       |        |             | clock skew.  This claim is         |
   |       |        |             | OPTIONAL.                          |



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   | iat   | number | IntDate     | The "iat" (issued at) claim        |
   |       |        |             | identifies the time at which the   |
   |       |        |             | JWT was issued.  This claim can be |
   |       |        |             | used to determine the age of the   |
   |       |        |             | token.  This claim is OPTIONAL.    |
   | iss   | string | StringOrURI | The "iss" (issuer) claim           |
   |       |        |             | identifies the principal that      |
   |       |        |             | issued the JWT.  The processing of |
   |       |        |             | this claim is generally            |
   |       |        |             | application specific.  The "iss"   |
   |       |        |             | value is case sensitive.  This     |
   |       |        |             | claim is OPTIONAL.                 |
   | aud   | string | StringOrURI | The "aud" (audience) claim         |
   |       |        |             | identifies the audience that the   |
   |       |        |             | JWT is intended for.  The          |
   |       |        |             | principal intended to process the  |
   |       |        |             | JWT MUST be identified with the    |
   |       |        |             | value of the audience claim.  If   |
   |       |        |             | the principal processing the claim |
   |       |        |             | does not identify itself with the  |
   |       |        |             | identifier in the "aud" claim      |
   |       |        |             | value then the JWT MUST be         |
   |       |        |             | rejected.  The interpretation of   |
   |       |        |             | the audience value is generally    |
   |       |        |             | application specific.  The "aud"   |
   |       |        |             | value is case sensitive.  This     |
   |       |        |             | claim is OPTIONAL.                 |
   | prn   | string | StringOrURI | The "prn" (principal) claim        |
   |       |        |             | identifies the subject of the JWT. |
   |       |        |             | The processing of this claim is    |
   |       |        |             | generally application specific.    |
   |       |        |             | The "prn" value is case sensitive. |
   |       |        |             | This claim is OPTIONAL.            |
   | jti   | string | String      | The "jti" (JWT ID) claim provides  |
   |       |        |             | a unique identifier for the JWT.   |
   |       |        |             | The identifier value MUST be       |
   |       |        |             | assigned in a manner that ensures  |
   |       |        |             | that there is a negligible         |
   |       |        |             | probability that the same value    |
   |       |        |             | will be accidentally assigned to a |
   |       |        |             | different data object.  The "jti"  |
   |       |        |             | claim can be used to prevent the   |
   |       |        |             | JWT from being replayed.  The      |
   |       |        |             | "jti" value is case sensitive.     |
   |       |        |             | This claim is OPTIONAL.            |






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   | typ   | string | String      | The "typ" (type) claim is used to  |
   |       |        |             | declare a type for the contents of |
   |       |        |             | this JWT Claims Set. The "typ"     |
   |       |        |             | value is case sensitive.  This     |
   |       |        |             | claim is OPTIONAL.                 |
   +-------+--------+-------------+------------------------------------+

                    Table 1: Reserved Claim Definitions

   Additional reserved claim names MAY be defined via the IANA JSON Web
   Token Claims registry, as per Section 9.  The syntax values used
   above are defined as follows:

   +-------------+-----------------------------------------------------+
   | Syntax Name | Syntax Definition                                   |
   +-------------+-----------------------------------------------------+
   | IntDate     | The number of seconds from 1970-01-01T0:0:0Z as     |
   |             | measured in UTC until the desired date/time.  See   |
   |             | RFC 3339 [RFC3339] for details regarding date/times |
   |             | in general and UTC in particular.                   |
   | String      | Any string value MAY be used.                       |
   | StringOrURI | Any string value MAY be used but a value containing |
   |             | a ":" character MUST be a URI as defined in RFC     |
   |             | 3986 [RFC3986].                                     |
   +-------------+-----------------------------------------------------+

                     Table 2: Claim Syntax Definitions

4.2.  Public Claim Names

   Claim names can be defined at will by those using JWTs.  However, in
   order to prevent collisions, any new claim name SHOULD either be
   defined in the IANA JSON Web Token Claims registry or be defined as a
   URI that contains a collision resistant namespace.  Examples of
   collision resistant namespaces include:

   o  Domain Names,

   o  Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670
      Recommendation series, or

   o  Universally Unique IDentifier (UUID) as defined in RFC 4122
      [RFC4122].

   In each case, the definer of the name or value needs to take
   reasonable precautions to make sure they are in control of the part
   of the namespace they use to define the claim name.




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4.3.  Private Claim Names

   A producer and consumer of a JWT may agree to any claim name that is
   not a Reserved Name Section 4.1 or a Public Name Section 4.2.  Unlike
   Public Names, these private names are subject to collision and should
   be used with caution.


5.  JWT Header

   The members of the JSON object represented by the JWT Header describe
   the cryptographic operations applied to the JWT and optionally,
   additional properties of the JWT.  The member names within the JWT
   Header are referred to as Header Parameter Names.  These names MUST
   be unique.  The corresponding values are referred to as Header
   Parameter Values.

   Implementations MUST understand the entire contents of the header;
   otherwise, the JWT MUST be rejected for processing.

   There are two ways of distinguishing whether the JWT is a JWS or JWE.
   The first is by examining the "alg" (algorithm) header value.  If the
   value represents a signature algorithm, the JWT is a JWS; if it
   represents an encryption algorithm, the JWT is a JWE.  A second
   method is determining whether an "enc" (encryption method) member
   exists.  If the "enc" member exists, the JWT is a JWE; otherwise, the
   JWT is a JWS.  Both methods will yield the same result.

   JWS Header Parameters are defined by [JWS].  JWE Header Parameters
   are defined by [JWE].  This specification further specifies the use
   of the following header parameters in both the cases where the JWT is
   a JWS and where it is a JWE.



















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   +----------+--------+-----------+-----------------------------------+
   | Header   | JSON   | Header    | Header Parameter Semantics        |
   | Paramete | Value  | Parameter |                                   |
   | rName    | Type   | Syntax    |                                   |
   +----------+--------+-----------+-----------------------------------+
   | typ      | string | String    | The "typ" (type) header parameter |
   |          |        |           | is used to declare structural     |
   |          |        |           | information about the JWT.  In    |
   |          |        |           | the normal case where nested      |
   |          |        |           | signing or encryption operations  |
   |          |        |           | are not employed, the use of this |
   |          |        |           | header parameter is OPTIONAL, and |
   |          |        |           | if present, it is RECOMMENDED     |
   |          |        |           | that its value be either "JWT" or |
   |          |        |           | "http://openid.net/specs/jwt/1.0" |
   |          |        |           | .In the case that nested signing  |
   |          |        |           |  or encryption steps are employed |
   |          |        |           | ,the use of this header parameter |
   |          |        |           |  is REQUIRED; in this case, the   |
   |          |        |           |  value MUST either be "JWS", to   |
   |          |        |           |  indicate that a nested signed JW |
   |          |        |           | Tis carried in this JWT or "JWE", |
   |          |        |           |  to indicate that a nested        |
   |          |        |           |  encrypted JWT is carried in this |
   |          |        |           |  JWT.                             |
   +----------+--------+-----------+-----------------------------------+

                 Table 3: Reserved Header Parameter Usage


6.  Plaintext JWTs

   To support use cases where the JWT content is secured by a means
   other than a signature and/or encryption contained within the token
   (such as a signature on a data structure containing the token), JWTs
   MAY also be created without a signature or encryption.  Plaintext
   JWTs MUST use the "alg" value "none", and are formatted identically
   to a signed JWT with an empty signature.  This means that the
   base64url encoding of the bytes representing the UTF-8 encoding of
   the JWT Claims Set is the JWT Second Part, and the empty string is
   the JWT Third Part.

6.1.  Example Plaintext JWT

   The following example JWT Header declares that the encoded object is
   a Plaintext JWT:
   {"alg":"none"}




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   Base64url encoding the bytes of the UTF-8 representation of the JWT
   Header yields this Encoded JWT Header:
   eyJhbGciOiJub25lIn0

   The following is an example of a JWT Claims Set:
   {"iss":"joe",
    "exp":1300819380,
    "http://example.com/is_root":true}

   Base64url encoding the bytes of the UTF-8 representation of the JSON
   Claims Set yields this Encoded JWS Payload, which is used as the JWT
   Second Part (with line breaks for display purposes only):
   eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
   cGxlLmNvbS9pc19yb290Ijp0cnVlfQ

   The JWT Third Part is the empty string.

   Concatenating these parts in the order Header.Second.Third with
   period characters between the parts yields this complete JWT (with
   line breaks for display purposes only):
   eyJhbGciOiJub25lIn0
   .
   eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
   cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
   .


7.  Rules for Creating and Validating a JWT

   To create a JWT, one MUST perform these steps:

   1.  Create a JWT Claims Set containing the desired claims.  Note that
       white space is explicitly allowed in the representation and no
       canonicalization is performed before encoding.

   2.  Let the Message be the bytes of the UTF-8 representation of the
       JWT Claims Set.

   3.  Create a JWT Header containing the desired set of header
       parameters.  If the JWT is to be signed or encrypted, they MUST
       conform to either the [JWS] or [JWE] specifications,
       respectively.  Else, if the JWT is to be plaintext, the "alg"
       value "none" MUST be used.  Note that white space is explicitly
       allowed in the representation and no canonicalization is
       performed before encoding.

   4.  Base64url encode the bytes of the UTF-8 representation of the JWT
       Header.  Let this be the Encoded JWT Header.



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   5.  Depending upon whether the JWT is to be signed, encrypted, or
       plaintext, there are three cases:

       *  If the JWT is to be signed, create a JWS using the JWT Header
          as the JWS Header and the Message as the JWS Payload; all
          steps specified in [JWS] for creating a JWS MUST be followed.
          Let the JWT Second Part be the Encoded JWS Payload and let the
          JWT Third Part be the Encoded JWS Signature.

       *  If the JWT is to be encrypted, create a JWE using the JWT
          Header as the JWE Header and the Message as the JWE Plaintext;
          all steps specified in [JWE] for creating a JWE MUST be
          followed.  Let the JWT Second Part be the Encoded JWE
          Encrypted Key and let the JWT Third Part be the Encoded JWS
          Ciphertext.

       *  Else, if the JWT is to be plaintext, let the JWT Second Part
          be the base64url encoding of the Message and let the JWT Third
          Part be the empty string.

   6.  Concatenate the Encoded JWT Header, the JWT Second Part, and the
       JWT Third Part in that order, separating each by period ('.')
       characters.

   7.  If a nested signing or encryption operation will be performed,
       let the Message be this concatenation, and return to Step 3,
       using a "typ" value of either "JWS" or "JWE" respectively in the
       new JWT Header created in that step.

   8.  Otherwise, let the resulting JWT be this concatenation.

   When validating a JWT the following steps MUST be taken.  If any of
   the listed steps fails then the token MUST be rejected for
   processing.

   1.   The JWT MUST contain exactly two period characters.

   2.   The JWT MUST be split on the two period characters resulting in
        three strings.  The first string is the Encoded JWT Header; the
        second is the JWT Second Part; the third is the JWT Third Part.

   3.   The Encoded JWT Header MUST be successfully base64url decoded
        following the restriction given in this specification that no
        padding characters have been used.

   4.   The JWT Header MUST be completely valid JSON syntax conforming
        to RFC 4627 [RFC4627].




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   5.   The JWT Header MUST be validated to only include parameters and
        values whose syntax and semantics are both understood and
        supported.

   6.   Determine whether the JWT is signed, encrypted, or plaintext by
        examining the "alg" (algorithm) header value and optionally, the
        "enc" (encryption method) header value, if present.

   7.   Depending upon whether the JWT signed, encrypted, or plaintext,
        there are three cases:

        *  If the JWT is signed, all steps specified in [JWS] for
           validating a JWS MUST be followed.  Let the Message be the
           result of base64url decoding the JWS Payload.

        *  If the JWT is encrypted, all steps specified in [JWE] for
           validating a JWE MUST be followed.  Let the Message be the
           JWE Plaintext.

        *  Else, if the JWT is plaintext, let the Message be the result
           of base64url decoding the JWE Second Part.  The Third Part
           MUST be verified to be the empty string.

   8.   If the JWT Header contains a "typ" value of either "JWS" or
        "JWE", then the Message contains a JWT that was the subject of
        nested signing or encryption operations, respectively.  In this
        case, return to Step 1, using the Message as the JWT.

   9.   Otherwise, let the JWT Claims Set be the Message.

   10.  The JWT Claims Set MUST be completely valid JSON syntax
        conforming to RFC 4627 [RFC4627].

   11.  When used in a security-related context, the JWT Claims Set MUST
        be validated to only include claims whose syntax and semantics
        are both understood and supported.

   Processing a JWT inevitably requires comparing known strings to
   values in the token.  For example, in checking what the algorithm is,
   the Unicode string encoding "alg" will be checked against the member
   names in the JWT Header to see if there is a matching header
   parameter name.  A similar process occurs when determining if the
   value of the "alg" header parameter represents a supported algorithm.

   Comparisons between JSON strings and other Unicode strings MUST be
   performed as specified below:





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   1.  Remove any JSON applied escaping to produce an array of Unicode
       code points.

   2.  Unicode Normalization [USA15] MUST NOT be applied at any point to
       either the JSON string or to the string it is to be compared
       against.

   3.  Comparisons between the two strings MUST be performed as a
       Unicode code point to code point equality comparison.


8.  Cryptographic Algorithms

   JWTs use JSON Web Signature (JWS) [JWS] and JSON Web Encryption (JWE)
   [JWE] to sign and/or encrypt the contents of the JWT.

   Of the JWS signing algorithms, only HMAC SHA-256 MUST be implemented
   by conforming JWT implementations.  It is RECOMMENDED that
   implementations also support the RSA SHA-256 and ECDSA P-256 SHA-256
   algorithms.  Support for other algorithms and key sizes is OPTIONAL.

   If an implementation provides encryption capabilities, of the JWE
   encryption algorithms, only RSA-PKCS1-1.5 with 2048 bit keys, AES-
   128-CBC, and AES-256-CBC MUST be implemented by conforming
   implementations.  It is RECOMMENDED that implementations also support
   ECDH-ES with 256 bit keys, AES-128-GCM, and AES-256-GCM.  Support for
   other algorithms and key sizes is OPTIONAL.


9.  IANA Considerations

   This specification calls for:

   o  A new IANA registry entitled "JSON Web Token Claims" for reserved
      claim names is defined in Section 4.1.  Inclusion in the registry
      is RFC Required in the RFC 5226 [RFC5226] sense for reserved JWT
      claim names that are intended to be interoperable between
      implementations.  The registry will just record the reserved claim
      name and a pointer to the RFC that defines it.  This specification
      defines inclusion of the claim names defined in Table 1.


10.  Security Considerations

   TBD: Lots of work to do here.  We need to remember to look into any
   issues relating to security and JSON parsing.  One wonders just how
   secure most JSON parsing libraries are.  Were they ever hardened for
   security scenarios?  If not, what kind of holes does that open up?



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   Also, we need to walk through the JSON standard and see what kind of
   issues we have especially around comparison of names.  For instance,
   comparisons of claim names and other parameters must occur after they
   are unescaped.  Need to also put in text about: Importance of keeping
   secrets secret.  Rotating keys.  Strengths and weaknesses of the
   different algorithms.

   TBD: Need to put in text about why strict JSON validation is
   necessary.  Basically, that if malformed JSON is received then the
   intent of the sender is impossible to reliably discern.  One example
   of malformed JSON that MUST be rejected is an object in which the
   same member name occurs multiple times.  While in non-security
   contexts it's o.k. to be generous in what one accepts, in security
   contexts this can lead to serious security holes.  For example,
   malformed JSON might indicate that someone has managed to find a
   security hole in the issuer's code and is leveraging it to get the
   issuer to issue "bad" tokens whose content the attacker can control.

   TBD: Write about the need to secure the token content if a signature
   is not contained in the JWT itself.

10.1.  Unicode Comparison Security Issues

   Claim names in JWTs are Unicode strings.  For security reasons, the
   representations of these names must be compared verbatim after
   performing any escape processing (as per RFC 4627 [RFC4627], Section
   2.5).

   This means, for instance, that these JSON strings must compare as
   being equal ("JWT", "\u004aWT"), whereas these must all compare as
   being not equal to the first set or to each other ("jwt", "Jwt",
   "JW\u0074").

   JSON strings MAY contain characters outside the Unicode Basic
   Multilingual Plane.  For instance, the G clef character (U+1D11E) may
   be represented in a JSON string as "\uD834\uDD1E".  Ideally, JWT
   implementations SHOULD ensure that characters outside the Basic
   Multilingual Plane are preserved and compared correctly;
   alternatively, if this is not possible due to these characters
   exercising limitations present in the underlying JSON implementation,
   then input containing them MUST be rejected.


11.  Open Issues and Things To Be Done (TBD)

   The following items remain to be done in this draft:





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   o  Provide an example of an encrypted JWT.

   o  Clarify the optional ability to provide type information for JWTs
      and/or their parts.  Specifically, clarify whether we need to
      specify the "typ" Claim Name in addition to the Header Parameter,
      whether it conveys syntax or semantics, and indeed, whether this
      is the right approach.  Also clarify the relationship between
      these type values and MIME [RFC2045] types (if any).

   o  Think about how to best describe the concept currently described
      as "the bytes of the UTF-8 representation of".  Possible terms to
      use instead of "bytes of" include "byte sequence", "octet series",
      and "octet sequence".  Also consider whether we want to add an
      overall clarifying statement somewhere in each spec something like
      "every place we say 'the UTF-8 representation of X', we mean 'the
      bytes of the UTF-8 representation of X'".  That would potentially
      allow us to omit the "the bytes of" part everywhere else.

   o  Consider whether a media type should be proposed, such as
      "application/jwt".

   o  Finish the Security Considerations section.

   o  Possibly write a companion specification that contains the former
      JWT JSON Serialization.


12.  References

12.1.  Normative References

   [JWS]      Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer,
              J., Sakimura, N., and P. Tarjan, "JSON Web Signature
              (JWS)", December 2011.

   [RFC2045]  Freed, N. and N. Borenstein, "Multipurpose Internet Mail
              Extensions (MIME) Part One: Format of Internet Message
              Bodies", RFC 2045, November 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3339]  Klyne, G., Ed. and C. Newman, "Date and Time on the
              Internet: Timestamps", RFC 3339, July 2002.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, November 2003.




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   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66,
              RFC 3986, January 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, October 2006.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [USA15]    Davis, M., Whistler, K., and M. Duerst, "Unicode
              Normalization Forms", Unicode Standard Annex 15, 09 2009.

12.2.  Informative References

   [CanvasApp]
              Facebook, "Canvas Applications", 2010.

   [JSS]      Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
              September 2010.

   [JWE]      Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
              Encryption (JWE)", December 2011.

   [MagicSignatures]
              Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
              Signatures", August 2010.

   [OASIS.saml-core-2.0-os]
              Cantor, S., Kemp, J., Philpott, R., and E. Maler,
              "Assertions and Protocol for the OASIS Security Assertion
              Markup Language (SAML) V2.0", OASIS Standard saml-core-
              2.0-os, March 2005.

   [RFC3275]  Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup
              Language) XML-Signature Syntax and Processing", RFC 3275,
              March 2002.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.

   [SWT]      Hardt, D. and Y. Goland, "Simple Web Token (SWT)",
              Version 0.9.5.1, November 2009.



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   [W3C.CR-xml11-20021015]
              Cowan, J., "Extensible Markup Language (XML) 1.1", W3C
              CR CR-xml11-20021015, October 2002.


Appendix A.  Relationship of JWTs to SAML Tokens

   SAML 2.0 [OASIS.saml-core-2.0-os] provides a standard for creating
   tokens with much greater expressivity and more security options than
   supported by JWTs.  However, the cost of this flexibility and
   expressiveness is both size and complexity.  In addition, SAML's use
   of XML [W3C.CR-xml11-20021015] and XML DSIG [RFC3275] only
   contributes to the size of SAML tokens.

   JWTs are intended to provide a simple token format that is small
   enough to fit into HTTP headers and query arguments in URIs.  It does
   this by supporting a much simpler token model than SAML and using the
   JSON [RFC4627] object encoding syntax.  It also supports securing
   tokens using Hash-based Message Authentication Codes (HMACs) and
   digital signatures using a smaller (and less flexible) format than
   XML DSIG.

   Therefore, while JWTs can do some of the things SAML tokens do, JWTs
   are not intended as a full replacement for SAML tokens, but rather as
   a compromise token format to be used when space is at a premium.


Appendix B.  Relationship of JWTs to Simple Web Tokens (SWTs)

   Both JWTs and Simple Web Tokens SWT [SWT], at their core, enable sets
   of claims to be communicated between applications.  For SWTs, both
   the claim names and claim values are strings.  For JWTs, while claim
   names are strings, claim values can be any JSON type.  Both token
   types offer cryptographic protection of their content: SWTs with HMAC
   SHA-256 and JWTs with a choice of algorithms, including HMAC SHA-256,
   RSA SHA-256, and ECDSA P-256 SHA-256.


Appendix C.  Acknowledgements

   The authors acknowledge that the design of JWTs was intentionally
   influenced by the design and simplicity of Simple Web Tokens [SWT]
   and ideas for JSON tokens that Dick Hardt discussed within the OpenID
   community.

   Solutions for signing JSON content were previously explored by Magic
   Signatures [MagicSignatures], JSON Simple Sign [JSS], and Canvas
   Applications [CanvasApp], all of which influenced this draft.



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Appendix D.  Document History

   -07

   o  Defined the "prn" (principal) claim to identify the subject of the
      JWT.

   o  Defined the "jti" (JWT ID) claim to enable replay protection.

   o  Use the term "JWT Claims Set" rather than "JWT Claims Object"
      since this is actually a string representing a JSON object and not
      the JSON object itself.

   o  Moved "MUST" requirements from the Overview to later in the spec.

   o  Respect line length restrictions in examples.

   o  Applied other editorial improvements.

   -06

   o  Reference and use content from [JWS] and [JWE], rather than
      repeating it here.

   o  Simplified terminology to better match JWE, where the terms "JWT
      Header" and "Encoded JWT Header" are now used, for instance,
      rather than the previous terms "Decoded JWT Header Segment" and
      "JWT Header Segment".  Also changed to "Plaintext JWT" from
      "Unsigned JWT".

   o  Describe how to perform nested encryption and signing operations.

   o  Changed "integer" to "number", since that is the correct JSON
      type.

   o  Changed StringAndURI to StringOrURI.

   -05

   o  Added the "nbf" (not before) claim and clarified the meaning of
      the "iat" (issued at) claim.

   -04

   o  Correct typo found by John Bradley: "the JWT Claim Segment is the
      empty string" -> "the JWT Crypto Segment is the empty string".

   -03



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   o  Added "http://openid.net/specs/jwt/1.0" as a token type identifier
      URI for JWTs.

   o  Added "iat" (issued at) claim.

   o  Changed RSA SHA-256 from MUST be supported to RECOMMENDED that it
      be supported.  Rationale: Several people have objected to the
      requirement for implementing RSA SHA-256, some because they will
      only be using HMACs and symmetric keys, and others because they
      only want to use ECDSA when using asymmetric keys, either for
      security or key length reasons, or both.

   o  Defined "alg" value "none" to represent unsigned JWTs.

   -02

   o  Split signature specification out into separate
      draft-jones-json-web-signature-00.  This split introduced no
      semantic changes.

   o  The JWT Compact Serialization is now the only token serialization
      format specified in this draft.  The JWT JSON Serialization can
      continue to be defined in a companion specification.

   -01

   o  Draft incorporating consensus decisions reached at IIW.

   -00

   o  Public draft published before November 2010 IIW based upon the
      JSON token convergence proposal incorporating input from several
      implementers of related specifications.


Authors' Addresses

   Michael B. Jones
   Microsoft

   Email: mbj@microsoft.com
   URI:   http://self-issued.info/









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   Dirk Balfanz
   Google

   Email: balfanz@google.com


   John Bradley
   independent

   Email: ve7jtb@ve7jtb.com


   Yaron Y. Goland
   Microsoft

   Email: yarong@microsoft.com


   John Panzer
   Google

   Email: jpanzer@google.com


   Nat Sakimura
   Nomura Research Institute

   Email: n-sakimura@nri.co.jp


   Paul Tarjan
   Facebook

   Email: pt@fb.com

















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