Network Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track D. Balfanz
Expires: September 29, 2011 Google
J. Bradley
independent
Y. Goland
Microsoft
J. Panzer
Google
N. Sakimura
Nomura Research Institute
P. Tarjan
Facebook
March 28, 2011
JSON Web Token (JWT)
draft-jones-json-web-token-02
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 a JSON Web Signature
(JWS) and optionally 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 September 29, 2011.
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 . . . . . . . . . . . . . . . . . . . . . . . 5
4. JWT Claims . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Reserved Claim Names . . . . . . . . . . . . . . . . . . . 7
4.2. Public Claim Names . . . . . . . . . . . . . . . . . . . . 8
4.3. Private Claim Names . . . . . . . . . . . . . . . . . . . 9
5. JWT Header . . . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Rules for Creating and Validating a JWT . . . . . . . . . . . 9
7. Base64url encoding as used by JWTs . . . . . . . . . . . . . . 12
8. Signing JWTs with Cryptographic Algorithms . . . . . . . . . . 12
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
10. Security Considerations . . . . . . . . . . . . . . . . . . . 12
10.1. Unicode Comparison Security Issues . . . . . . . . . . . . 13
11. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . 13
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . . 15
Appendix A. JWT Examples . . . . . . . . . . . . . . . . . . . . 16
A.1. JWT using HMAC SHA-256 . . . . . . . . . . . . . . . . . . 16
A.2. JWT using RSA SHA-256 . . . . . . . . . . . . . . . . . . 17
A.3. JWT using ECDSA P-256 SHA-256 . . . . . . . . . . . . . . 19
Appendix B. Notes on implementing base64url encoding without
padding . . . . . . . . . . . . . . . . . . . . . . . 21
Appendix C. Relationship of JWTs to SAML Tokens . . . . . . . . . 22
Appendix D. Relationship of JWTs to Simple Web Tokens (SWTs) . . 22
Appendix E. Acknowledgements . . . . . . . . . . . . . . . . . . 22
Appendix F. Document History . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
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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. Signing is accomplished using a JSON Web
Signature (JWS) [JWS]. JWTs may also be optionally encrypted 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 JWT Token
Segments: the JWT Header Segment, the JWT Claim Segment, and the
JWT Crypto Segment, in that order, with the segments being
separated by period ('.') characters.
JWT Token Segment One of the three parts that make up a JSON Web
Token (JWT). JWT Token Segments are always base64url encoded
values.
JWT Header Segment A JWT Token Segment containing a base64url
encoded JSON object that describes the cryptographic operations
applied to the JWT Header Segment and the JWT Claim Segment. The
JWT Header Segment is the JWS Header Input for creating a JSON Web
Signature (JWS) [JWS] for the JWT.
JWT Claim Segment A JWT Token Segment containing a base64url encoded
JSON object that encodes the claims contained in the JWT. The JWT
Claim Segment is the JWS Payload Input for creating a JSON Web
Signature (JWS) [JWS] for the JWT.
JWT Crypto Segment A JWT Token Segment containing base64url encoded
cryptographic material that secures the contents of the JWT Header
Segment and the JWT Claim Segment. The JWT Crypto Segment is the
JWS Crypto Output for a JSON Web Signature (JWS) [JWS] created for
the JWT.
Decoded JWT Header Segment A JWT Header Segment that has been
base64url decoded back into a JSON object.
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Decoded JWT Claim Segment A JWT Claim Segment that has been
base64url decoded back into a JSON object.
Decoded JWT Crypto Segment A JWT Crypto Segment that has been
base64url decoded back into cryptographic material.
Claim Names The names of the members of the JSON object represented
in a JWT Claim Segment.
Claim Values The values of the members of the JSON object
represented in a JWT Claim Segment.
Base64url Encoding For the purposes of this specification, this term
always refers to the he URL- and filename-safe Base64 encoding
described in RFC 4648 [RFC4648], Section 5, with the '=' padding
characters omitted, as permitted by Section 3.2.
3. JSON Web Token (JWT) Overview
JWTs represent a set of claims as a JSON object that is base64url
encoded and digitally signed and optionally encrypted. 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 JSON object is base64url encoded to
produce the JWT Claim Segment.
The names within the JSON object MUST be unique. These names are
referred to as Claim Names. The corresponding values are referred to
as Claim Values.
The JWT Claim Object is signed in the manner described in JSON Web
Signature (JWS) [JWS] and optionally encrypted in the manner
described in JSON Web Encryption (JWE) [JWE]. The JWT Claim Object
is the JWS Payload Input. The JWT Header Object is the JWS Header
Input. The JWT Crypto Segment is the corresponding JWS Crypto
Output.
A JWT is represented as the concatenation of the JWT Header Segment,
the JWT Claim Segment, and the JWT Crypto Segment, in that order,
with the segments being separated by period ('.') characters.
3.1. Example JWT
The following is an example of a JSON object that can be encoded to
produce a JWT Claim Segment:
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{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Base64url encoding the UTF-8 representation of the JSON object yields
this JWT Claim Segment:
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The following example JSON header object declares that the encoded
object is a JSON Web Token (JWT) and the JWT Header Segment and the
JWT Claim Segment are signed using the HMAC SHA-256 algorithm:
{"typ":"JWT",
"alg":"HS256"}
Base64url encoding the UTF-8 representation of the JSON header object
yields this JWT Header Segment value:
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
Signing the UTF-8 representation of the JWT Header Segment and JWT
Claim Segment with the HMAC SHA-256 algorithm and base64url encoding
the result, as per Appendix A.1, in the manner specified in [JWS],
yields this JWT Crypto Segment value:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Concatenating these segments in the order Header.Claims.Signature
with period characters between the segments yields this complete JWT
(with line breaks for display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
This computation is illustrated in more detail in Appendix A.1.
4. JWT Claims
A JWT contains a set of claims represented as a base64url encoded
JSON object. Note however, that the set of claims 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.
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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 Syntax | Claim Semantics |
| Name | Value | | |
| | Type | | |
+-------+---------+--------------+----------------------------------+
| exp | integer | 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. |
| iss | string | StringAndURI | The "iss" (issuer) claim |
| | | | identifies the principal that |
| | | | issued the JWT. The processing |
| | | | of this claim is generally |
| | | | application specific. This |
| | | | claim is OPTIONAL. |
| aud | string | StringAndURI | The "aud" (audience) claim |
| | | | identifies the audience that the |
| | | | JWT is intended for. The |
| | | | principal intended to process |
| | | | the JWT MUST be identified by |
| | | | 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 contents of the audience |
| | | | value is generally application |
| | | | specific. 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. 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. |
| StringAndURI | 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 MUST 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 Decoded JWT Header
Segment describe the cryptographic operations applied to the JWT
Header Segment and the JWT Claim Segment and optionally, additional
properties of the JWT. The JWT Header Segment is used as the JWS
Header Input for signing. The format of the header and the
cryptographic operations applied MUST be as specified in JSON Web
Signature (JWS) [JWS] and JSON Web Encryption (JWE) [JWE].
Implementations MUST understand the entire contents of the header;
otherwise, the JWT MUST be rejected for processing.
JWS Header Parameters are defined by [JWS]. This specification
further specifies the use of the following header parameters when the
JWS Header Input is a JWT Header Segment.
+-----------+--------+-----------+----------------------------------+
| Header | JSON | Header | Header Parameter Semantics |
| Parameter | Value | Parameter | |
| Name | Type | Syntax | |
+-----------+--------+-----------+----------------------------------+
| typ | string | String | The "typ" (type) header |
| | | | parameter MAY be used to declare |
| | | | that this data structure is a |
| | | | JWT. If a "typ" parameter is |
| | | | present, it is RECOMMENDED that |
| | | | its value be "JWT". Use of this |
| | | | header parameter is OPTIONAL. |
+-----------+--------+-----------+----------------------------------+
Table 3: Reserved Header Parameter Usage
6. Rules for Creating and Validating a JWT
To create a JWT, one MUST follow these steps:
1. Create a JSON object containing the desired claims. Note that
white space is explicitly allowed in the representation and no
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canonicalization is performed before encoding.
2. Translate this JSON object's Unicode code points into UTF-8, as
defined in RFC 3629 [RFC3629]. This is the Decoded JWT Claim
Segment.
3. Base64url encode the Decoded JWT Claim Segment. This encoding
becomes the JWT Claim Segment.
4. Create a JSON object containing a set of desired header
parameters that conform to the [JWS] and [JWE] specifications.
Note that white space is explicitly allowed in the representation
and no canonicalization is performed before encoding.
5. Translate this JSON object's Unicode code points into UTF-8, as
defined in RFC 3629 [RFC3629]. This is the Decoded JWT Header
Segment.
6. Base64url encode the UTF-8 representation of this JSON object as
defined in this specification (without padding). This encoding
becomes a JWT Header Segment.
7. Sign and optionally encrypt the JWT Header Segment and JWT Claim
Segment values in the manner described in the [JWS] and [JWE]
specifications; the JWT Header Segment is used as the JWS Header
Input and the JWT Claim Segment is used as the JWS Payload Input;
the resulting JWS Crypto Output is used as the JWT Claim Segment.
8. Concatenate the JWT Header Segment, the JWT Claim Segment, and
the JWT Crypto Segment in that order, separating each by period
characters, to create the JWT.
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 two period characters.
2. The JWT MUST be split on the two period characters resulting in
three non-empty segments. The first segment is the JWT Header
Segment; the second is the JWT Claim Segment; the third is the
JWT Crypto Segment.
3. The JWT Claim Segment MUST be successfully base64url decoded
following the restriction given in this specification that no
padding characters have been used.
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4. The Decoded JWT Claim Segment MUST be completely valid JSON
syntax conforming to RFC 4627 [RFC4627].
5. When used in a security-related context, the Decoded JWT Claim
Segment MUST be validated to only include claims whose syntax
and semantics are both understood and supported.
6. The JWT Header Segment MUST be successfully base64url decoded
following the restriction given in this specification that no
padding characters have been used.
7. The Decoded JWT Header Segment MUST be completely valid JSON
syntax conforming to RFC 4627 [RFC4627].
8. The JWT Crypto Segment MUST be successfully base64url decoded
following the restriction given in this specification that no
padding characters have been used.
9. The JWT Header Segment MUST be validated to only include
parameters and values whose syntax and semantics are both
understood and supported.
10. The JWT Crypto Segment MUST be successfully validated against
the JWT Header Segment and JWT Claim Segment in the manner
defined by the [JWS] and [JWE] specifications.
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 Decoded JWT Header Segment 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. Comparing Unicode strings, however, has significant
security implications, as per Section 10.
Comparisons between JSON strings and other Unicode strings MUST be
performed as specified below:
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.
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7. Base64url encoding as used by JWTs
JWTs make use of the base64url encoding as defined in RFC 4648
[RFC4648]. As allowed by Section 3.2 of the RFC, this specification
mandates that base64url encoding when used with JWTs MUST NOT use
padding. The reason for this restriction is that the padding
character ('=') is not URL safe.
For notes on implementing base64url encoding without padding, see
Appendix B.
8. Signing JWTs with Cryptographic Algorithms
JWTs use JSON Web Signatures (JWSs) [JWS] and JSON Web Encryption
(JWE) [JWE] to sign and optionally encrypt the contents of the JWT
Header Segment and the JWT Claim Segment to produce the JWT Crypto
Segment Value.
Of the JWS signing algorithms, only HMAC SHA-256 and RSA SHA-256 MUST
be implemented by conforming JWT implementations. It is RECOMMENDED
that implementations also support the ECDSA P-256 SHA-256 algorithm.
Support for other algorithms 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?
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
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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. 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.
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 (and related
drafts):
o Consider whether we really want to allow private claim names and
that are not registered with IANA and are not in collision-
resistant namespaces. Eventually this could result in interop
nightmares where you need to have different code to talk to
different endpoints that "knows" about each endpoints' private
parameters.
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o Clarify the optional ability to provide type information for JWTs
and/or their segments. Specifically, clarify the intended use of
the "typ" Header Parameter and the "typ" claim, whether they
convey syntax or semantics, and indeed, whether this is the right
approach. Also clarify the relationship between these type values
and MIME [RFC2045] types.
o 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. I believe therefore, that we should consider
changing the MUST for RSA SHA-256 to RECOMMENDED.
o Finish the Security Considerations section.
o Sort out what to do with the IANA registries if this is first
standardized as an OpenID specification.
o 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)", March 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.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
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[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., Bradley, J., and N. Sakimura, "JSON Web
Encryption (JWE)", March 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.
[W3C.CR-xml11-20021015]
Cowan, J., "Extensible Markup Language (XML) 1.1", W3C
CR CR-xml11-20021015, October 2002.
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Appendix A. JWT Examples
This section provides several examples of JWTs. The cryptographic
operations for these examples are detailed in the JSON Web Signature
(JWS) [JWS] specification.
A.1. JWT using HMAC SHA-256
The Decoded JWT Claim Segment used in this example is:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Note that white space is explicitly allowed in Decoded JWT Claim
Segments and no canonicalization is performed before encoding. The
following byte array contains the UTF-8 characters for the Decoded
JWT Claim Segment:
[123, 34, 105, 115, 115, 34, 58, 34, 106, 111, 101, 34, 44, 13, 10,
32, 34, 101, 120, 112, 34, 58, 49, 51, 48, 48, 56, 49, 57, 51, 56,
48, 44, 13, 10, 32, 34, 104, 116, 116, 112, 58, 47, 47, 101, 120, 97,
109, 112, 108, 101, 46, 99, 111, 109, 47, 105, 115, 95, 114, 111,
111, 116, 34, 58, 116, 114, 117, 101, 125]
Base64url encoding the above yields the JWT Claim Segment value:
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The following example JSON header object declares that the data
structure is a JSON Web Token (JWT) and the JWT Header Segment and
JWT Crypto Segment are signed using the HMAC SHA-256 algorithm:
{"typ":"JWT",
"alg":"HS256"}
The following byte array contains the UTF-8 characters for the
Decoded JWT Header Segment:
[123, 34, 116, 121, 112, 34, 58, 34, 74, 87, 84, 34, 44, 13, 10, 32,
34, 97, 108, 103, 34, 58, 34, 72, 83, 50, 53, 54, 34, 125]
Base64url encoding this UTF-8 representation yields this JWT Header
Segment value:
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
This example uses the key represented by the following byte array:
[3, 35, 53, 75, 43, 15, 165, 188, 131, 126, 6, 101, 119, 123, 166,
143, 90, 179, 40, 230, 240, 84, 201, 40, 169, 15, 132, 178, 210, 80,
46, 191, 211, 251, 90, 146, 210, 6, 71, 239, 150, 138, 180, 195, 119,
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98, 61, 34, 61, 46, 33, 114, 5, 46, 79, 8, 192, 205, 154, 245, 103,
208, 128, 163]
Signing the JWT Header Segment and JWT Claim Segment with this key in
the manner specified by [JWS] yields this JWT Crypto Segment value:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Combining these segments in the order Header.Claims.Signature with
period characters between the segments yields this complete JWT (with
line breaks for display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
A.2. JWT using RSA SHA-256
The Decoded JWT Claim Segment used in this example is the same as in
the previous example:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Since the JWT Claim Segment will therefore be the same, its
computation is not repeated here. However, the Decoded JWT Header
Segment is different in two ways: First, because a different
algorithm is being used, the "alg" value is different. Second, for
illustration purposes only, the optional "typ" parameter is not used.
(This difference is not related to the signature algorithm employed.)
The Decoded JWT Header Segment used is:
{"alg":"RS256"}
The following byte array contains the UTF-8 characters for the
Decoded JWT Header Segment:
[123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125]
Base64url encoding this UTF-8 representation yields this JWT Header
Segment value:
eyJhbGciOiJSUzI1NiJ9
The RSA key consists of a public part (n, e), and a private exponent
d. The values of the RSA key used in this example, presented as the
byte arrays representing big endian integers are:
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+-----------+-------------------------------------------------------+
| Parameter | Value |
| Name | |
+-----------+-------------------------------------------------------+
| n | [161, 248, 22, 10, 226, 227, 201, 180, 101, 206, 141, |
| | 45, 101, 98, 99, 54, 43, 146, 125, 190, 41, 225, 240, |
| | 36, 119, 252, 22, 37, 204, 144, 161, 54, 227, 139, |
| | 217, 52, 151, 197, 182, 234, 99, 221, 119, 17, 230, |
| | 124, 116, 41, 249, 86, 176, 251, 138, 143, 8, 154, |
| | 220, 75, 105, 137, 60, 193, 51, 63, 83, 237, 208, 25, |
| | 184, 119, 132, 37, 47, 236, 145, 79, 228, 133, 119, |
| | 105, 89, 75, 234, 66, 128, 211, 44, 15, 85, 191, 98, |
| | 148, 79, 19, 3, 150, 188, 110, 155, 223, 110, 189, |
| | 210, 189, 163, 103, 142, 236, 160, 198, 104, 247, 1, |
| | 179, 141, 191, 251, 56, 200, 52, 44, 226, 254, 109, |
| | 39, 250, 222, 74, 90, 72, 116, 151, 157, 212, 185, |
| | 207, 154, 222, 196, 199, 91, 5, 133, 44, 44, 15, 94, |
| | 248, 165, 193, 117, 3, 146, 249, 68, 232, 237, 100, |
| | 193, 16, 198, 182, 71, 96, 154, 164, 120, 58, 235, |
| | 156, 108, 154, 215, 85, 49, 48, 80, 99, 139, 131, |
| | 102, 92, 111, 111, 122, 130, 163, 150, 112, 42, 31, |
| | 100, 27, 130, 211, 235, 242, 57, 34, 25, 73, 31, 182, |
| | 134, 135, 44, 87, 22, 245, 10, 248, 53, 141, 154, |
| | 139, 157, 23, 195, 64, 114, 143, 127, 135, 216, 154, |
| | 24, 216, 252, 171, 103, 173, 132, 89, 12, 46, 207, |
| | 117, 147, 57, 54, 60, 7, 3, 77, 111, 96, 111, 158, |
| | 33, 224, 84, 86, 202, 229, 233, 161] |
| e | [1, 0, 1] |
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| d | [18, 174, 113, 164, 105, 205, 10, 43, 195, 126, 82, |
| | 108, 69, 0, 87, 31, 29, 97, 117, 29, 100, 233, 73, |
| | 112, 123, 98, 89, 15, 157, 11, 165, 124, 150, 60, 64, |
| | 30, 63, 207, 47, 44, 211, 189, 236, 136, 229, 3, 191, |
| | 198, 67, 155, 11, 40, 200, 47, 125, 55, 151, 103, 31, |
| | 82, 19, 238, 216, 193, 90, 37, 216, 213, 206, 160, 2, |
| | 94, 227, 171, 46, 139, 127, 121, 33, 111, 198, 59, |
| | 234, 86, 39, 83, 180, 6, 68, 198, 161, 81, 39, 217, |
| | 178, 149, 69, 64, 160, 187, 225, 163, 5, 86, 152, 45, |
| | 78, 159, 222, 95, 100, 37, 241, 77, 75, 113, 52, 65, |
| | 181, 93, 199, 59, 155, 74, 237, 204, 146, 172, 227, |
| | 146, 126, 55, 245, 125, 12, 253, 94, 117, 129, 250, |
| | 81, 44, 143, 73, 97, 169, 235, 11, 128, 248, 168, 7, |
| | 70, 114, 138, 85, 255, 70, 71, 31, 52, 37, 6, 59, |
| | 157, 83, 100, 47, 94, 222, 30, 132, 214, 19, 8, 26, |
| | 250, 92, 34, 208, 81, 40, 91, 214, 59, 148, 59, 86, |
| | 93, 137, 138, 5, 104, 84, 19, 229, 60, 60, 108, 101, |
| | 37, 255, 31, 227, 78, 61, 220, 112, 240, 213, 100, |
| | 80, 253, 164, 139, 161, 46, 16, 78, 157, 235, 159, |
| | 184, 24, 129, 225, 196, 189, 242, 93, 146, 71, 244, |
| | 80, 200, 101, 146, 121, 104, 231, 115, 52, 244, 65, |
| | 79, 117, 167, 80, 225, 57, 84, 110, 58, 138, 115, |
| | 157] |
+-----------+-------------------------------------------------------+
Signing the JWT Header Segment and JWT Claim Segment with this key in
the manner specified by [JWS] yields this JWT Crypto Segment value:
cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw
Combining these segments in the order Header.Claims.Signature with
period characters between the segments yields this complete JWT (with
line breaks for display purposes only):
eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw
A.3. JWT using ECDSA P-256 SHA-256
The Decoded JWT Claim Segment used in this example is the same as in
the previous examples:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Since the JWT Claim Segment will therefore be the same, its
computation is not repeated here. However, the Decoded JWT Header
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Segment is differs from the previous example because a different
algorithm is being used. The Decoded JWT Header Segment used is:
{"alg":"ES256"}
The following byte array contains the UTF-8 characters for the
Decoded JWT Header Segment:
[123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125]
Base64url encoding this UTF-8 representation yields this JWT Header
Segment value:
eyJhbGciOiJFUzI1NiJ9
The ECDSA key consists of a public part, the EC point (x, y), and a
private part d. The values of the ECDSA key used in this example,
presented as the byte arrays representing big endian integers are:
+-----------+-------------------------------------------------------+
| Parameter | Value |
| Name | |
+-----------+-------------------------------------------------------+
| x | [127, 205, 206, 39, 112, 246, 196, 93, 65, 131, 203, |
| | 238, 111, 219, 75, 123, 88, 7, 51, 53, 123, 233, 239, |
| | 19, 186, 207, 110, 60, 123, 209, 84, 69] |
| y | [199, 241, 68, 205, 27, 189, 155, 126, 135, 44, 223, |
| | 237, 185, 238, 185, 244, 179, 105, 93, 110, 169, 11, |
| | 36, 173, 138, 70, 35, 40, 133, 136, 229, 173] |
| d | [142, 155, 16, 158, 113, 144, 152, 191, 152, 4, 135, |
| | 223, 31, 93, 119, 233, 203, 41, 96, 110, 190, 210, |
| | 38, 59, 95, 87, 194, 19, 223, 132, 244, 178] |
+-----------+-------------------------------------------------------+
Signing the JWT Header Segment and JWT Claim Segment with this key in
the manner specified by [JWS] yields this JWT Crypto Segment value:
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q
Combining these segments in the order Header.Claims.Signature with
period characters between the segments yields this complete JWT (with
line breaks for display purposes only):
eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q
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Appendix B. Notes on implementing base64url encoding without padding
This appendix describes how to implement base64url encoding and
decoding functions without padding based upon standard base64
encoding and decoding functions that do use padding.
To be concrete, example C# code implementing these functions is shown
below. Similar code could be used in other languages.
static string base64urlencode(byte [] arg)
{
string s = Convert.ToBase64String(arg); // Standard base64 encoder
s = s.Split('=')[0]; // Remove any trailing '='s
s = s.Replace('+', '-'); // 62nd char of encoding
s = s.Replace('/', '_'); // 63rd char of encoding
return s;
}
static byte [] base64urldecode(string arg)
{
string s = arg;
s = s.Replace('-', '+'); // 62nd char of encoding
s = s.Replace('_', '/'); // 63rd char of encoding
switch (s.Length % 4) // Pad with trailing '='s
{
case 0: break; // No pad chars in this case
case 2: s += "=="; break; // Two pad chars
case 3: s += "="; break; // One pad char
default: throw new System.Exception(
"Illegal base64url string!");
}
return Convert.FromBase64String(s); // Standard base64 decoder
}
As per the example code above, the number of '=' padding characters
that needs to be added to the end of a base64url encoded string
without padding to turn it into one with padding is a deterministic
function of the length of the encoded string. Specifically, if the
length mod 4 is 0, no padding is added; if the length mod 4 is 2, two
'=' padding characters are added; if the length mod 4 is 3, one '='
padding character is added; if the length mod 4 is 1, the input is
malformed.
An example correspondence between unencoded and encoded values
follows. The byte sequence below encodes into the string below,
which when decoded, reproduces the byte sequence.
3 236 255 224 193
A-z_4ME
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Appendix C. 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 D. 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 E. 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.
Appendix F. Document History
-02
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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/
Dirk Balfanz
Google
Email: balfanz@google.com
John Bradley
independent
Email: ve7jtb@ve7jtb.com
Yaron Y. Goland
Microsoft
Email: yarong@microsoft.com
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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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