Network Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track D. Balfanz
Expires: July 8, 2011 Google
J. Bradley
independent
Y. Goland
Microsoft
J. Panzer
Google
N. Sakimura
Nomura Research Institute
P. Tarjan
Facebook
January 04, 2011
JSON Web Token (JWT) - Claims and Signing
draft-jones-json-web-token-01
Abstract
JSON Web Token (JWT) is a means of representing signed content using
JSON data structures, including claims to be transferred between two
parties. The claims in a JWT are encoded as a JSON object that is
digitally signed and optionally encrypted. Encryption for JWTs is
described in a separate companion specification.
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
Jones, et al. Expires July 8, 2011 [Page 1]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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 July 8, 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.
Jones, et al. Expires July 8, 2011 [Page 2]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. JSON Web Token (JWT) Overview . . . . . . . . . . . . . . . . 7
3.1. Example JWT . . . . . . . . . . . . . . . . . . . . . . . 7
4. JWT Claims . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Reserved Claim Names . . . . . . . . . . . . . . . . . . . 8
4.2. Public Claim Names . . . . . . . . . . . . . . . . . . . . 10
4.3. Private Claim Names . . . . . . . . . . . . . . . . . . . 11
5. JWT Header . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Reserved Header Parameter Names . . . . . . . . . . . . . 11
5.2. Public Header Parameter Names . . . . . . . . . . . . . . 13
5.3. Private Header Parameter Names . . . . . . . . . . . . . . 13
6. Rules for Creating and Validating a JWT . . . . . . . . . . . 13
7. Base64url encoding as used by JWTs . . . . . . . . . . . . . . 17
8. Signing JWTs with Cryptographic Algorithms . . . . . . . . . . 17
8.1. Signing a JWT with HMAC SHA-256 . . . . . . . . . . . . . 18
8.2. Signing a JWT with RSA SHA-256 . . . . . . . . . . . . . . 19
8.3. Signing a JWT with ECDSA P-256 SHA-256 . . . . . . . . . . 20
8.4. Additional Algorithms . . . . . . . . . . . . . . . . . . 21
9. JWT Serialization Formats . . . . . . . . . . . . . . . . . . 21
9.1. JWT Compact Serialization . . . . . . . . . . . . . . . . 21
9.2. JWT JSON Serialization . . . . . . . . . . . . . . . . . . 22
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
11. Security Considerations . . . . . . . . . . . . . . . . . . . 23
11.1. Unicode Comparison Security Issues . . . . . . . . . . . . 23
12. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . 24
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
13.1. Normative References . . . . . . . . . . . . . . . . . . . 26
13.2. Informative References . . . . . . . . . . . . . . . . . . 27
Appendix A. JWT Examples . . . . . . . . . . . . . . . . . . . . 27
A.1. JWT using HMAC SHA-256 . . . . . . . . . . . . . . . . . . 27
A.1.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 28
A.1.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 29
A.1.3. Validating . . . . . . . . . . . . . . . . . . . . . . 30
A.2. JWT using RSA SHA-256 . . . . . . . . . . . . . . . . . . 30
A.2.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 30
A.2.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 34
A.2.3. Validating . . . . . . . . . . . . . . . . . . . . . . 35
A.3. JWT using ECDSA P-256 SHA-256 . . . . . . . . . . . . . . 35
A.3.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 35
A.3.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 37
A.3.3. Validating . . . . . . . . . . . . . . . . . . . . . . 37
A.4. JWT using JSON Serialization . . . . . . . . . . . . . . . 38
A.4.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 38
A.4.2. Decoding . . . . . . . . . . . . . . . . . . . . . . . 39
A.4.3. Validating . . . . . . . . . . . . . . . . . . . . . . 39
Jones, et al. Expires July 8, 2011 [Page 3]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
Appendix B. Notes on implementing base64url encoding without
padding . . . . . . . . . . . . . . . . . . . . . . . 39
Appendix C. Relationship of JWTs to SAML Tokens . . . . . . . . . 40
Appendix D. Relationship of JWTs to Simple Web Tokens (SWTs) . . 41
Appendix E. Acknowledgements . . . . . . . . . . . . . . . . . . 41
Appendix F. Document History . . . . . . . . . . . . . . . . . . 41
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 42
Jones, et al. Expires July 8, 2011 [Page 4]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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. The JWT signature mechanisms are independent
of the type of content being signed, allowing arbitrary content to be
signed. Encryption for JWTs is described in a separate companion
specification.
The suggested pronunciation of JWT is the same as the English word
"jot".
2. Terminology
JSON Web Token (JWT) A data structure containing three JWT Token
Segments: the JWT Header Segment, the JWT Payload Segment, and the
JWT Crypto Segment. The JWT Payload Segment typically represents
a set of claims convened by the JWT as a JSON object, but in the
general case, may represent arbitrary signed content.
JWT Compact Serialization A data structure representing a JWT as a
string consisting of three JWT Token Segments: the JWT Header
Segment, the JWT Payload Segment, and the JWT Crypto Segment, in
that order, with the segments being separated by period ('.')
characters.
JWT JSON Serialization A data structure representing a JWT as a JSON
object with members for each of three kinds of JWT Token Segments:
a "header" member whose value is a non-empty array of JWT Header
Segments, a "payload" member whose value is the JWT Payload
Segment, and a "signature" member whose value is a non-empty array
of JWT Crypto Segments, where the cardinality of both arrays is
the same.
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 signature applied to the
JWT Header Segment and the JWT Payload Segment.
Jones, et al. Expires July 8, 2011 [Page 5]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
JWT Payload Segment A JWT Token Segment containing base64url encoded
content. This may be a JWT Claims Object.
JWT Crypto Segment A JWT Token Segment containing base64url encoded
cryptographic signature material that secures the JWT Header
Segment's and the JWT Payload Segment's contents.
Decoded JWT Header Segment A JWT Header Segment that has been
base64url decoded back into a JSON object.
Decoded JWT Payload Segment A JWT Payload Segment that has been
base64url decoded. If the corresponding JWT Payload Segment is a
JWT Claims Object, this will be a Decoded JWT Claims Object.
Decoded JWT Crypto Segment A JWT Crypto Segment that has been
base64url decoded back into cryptographic material.
JWT Claims Object A base64url encoded JSON object that represents
the claims contained in the JWT.
Decoded JWT Claims Object A JSON object that represents the claims
contained in the JWT.
JWT Signing Input The concatenation of the JWT Header Segment, a
period ('.') character, and the JWT Payload Segment.
Digital Signature For the purposes of this specification, we use
this term to encompass both Hash-based Message Authentication
Codes (HMACs), which can provide authenticity but not non-
repudiation, and digital signatures using public key algorithms,
which can provide both. Readers should be aware of this
distinction, despite the decision to use a single term for both
concepts to improve readability of the specification.
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; see Section 7 for
more details.
Header Parameter Names The names of the members within the JSON
object represented in a JWT Header Segment.
Header Parameter Values The values of the members within the JSON
object represented in a JWT Header Segment.
Jones, et al. Expires July 8, 2011 [Page 6]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
Claim Names The names of the members of the JSON object represented
in a JWT Claims Object.
Claim Values The values of the members of the JSON object
represented in a JWT Claims Object.
3. JSON Web Token (JWT) Overview
JWTs represent content that is base64url encoded and digitally
signed, and optionally encrypted, using JSON data structures; this
content is typically a set of claims represented as a JSON object.
When the JWT payload is a set of claims, the claims are represented
as name/value pairs that are members of a JSON object. The JSON
object is base64url encoded to produce the JWT Claims Object, which
is used as the JWT Payload Segment. An accompanying base64url
encoded JSON header - the JWT Header Segment - describes the
signature method used.
The names within the header object MUST be unique. The names within
the header object are referred to as Header Parameter Names. The
corresponding values are referred to as Header Parameter Values.
Likewise, if the payload represents a JWT Claims Object, the names
within the claims object MUST be unique. The names within the claims
object are referred to as Claim Names. The corresponding values are
referred to as Claim Values.
JWTs contain a signature that ensures the integrity of the content of
the JWT Header Segment and the JWT Payload Segment. This signature
value is carried in the JWT Crypto Segment. The JSON Header object
MUST contain an "alg" parameter, the value of which is a string that
unambiguously identifies the algorithm used to sign the JWT Header
Segment and the JWT Payload Segment to produce the JWT Crypto
Segment.
3.1. Example JWT
The following is an example of a JSON object that can be encoded to
produce a JWT Claims Object:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Base64url encoding the UTF-8 representation of the JSON object yields
this JWT Claims Object, which is used as the JWT Payload Segment:
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
Jones, et al. Expires July 8, 2011 [Page 7]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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 Payload 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 Signing Input (the
concatenation of the JWT Header Segment, a period ('.') character,
and the JWT Payload Segment) with the HMAC SHA-256 algorithm and
base64url encoding the result, as per Section 8.1, yields this JWT
Crypto Segment value:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Concatenating these segments in the order Header.Payload.Signature
with period characters between the segments yields this complete JWT
using the JWT Compact Serialization (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
If the JWT contains a set of claims represented as a JSON object,
then the members of the JSON object represented by the Decoded JWT
Claims Object decoded from the JWT Payload Segment contain the
claims. 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.
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
Jones, et al. Expires July 8, 2011 [Page 8]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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
themselves to be short.
+-------+---------+--------------+----------------------------------+
| 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. |
Jones, et al. Expires July 8, 2011 [Page 9]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
| 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 10. The syntax values used
above and in Table 3 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]. |
| URI | A URI as defined in RFC 3986 [RFC3986]. |
| URL | A URL as defined in RFC 1738 [RFC1738]. |
+--------------+----------------------------------------------------+
Table 2
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.
Jones, et al. Expires July 8, 2011 [Page 10]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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 signature applied to the JWT Header Segment and
the JWT Payload Segment and optionally additional properties of the
JWT. Implementations MUST understand the entire contents of the
header; otherwise, the JWT MUST be rejected for processing.
5.1. Reserved Header Parameter Names
The following header parameter names are reserved. All the names are
short because a core goal of JWTs is for the tokens themselves to be
short.
+-----------+--------+--------------+-------------------------------+
| Header | JSON | Header | Header Parameter Semantics |
| Parameter | Value | Parameter | |
| Name | Type | Syntax | |
+-----------+--------+--------------+-------------------------------+
| alg | string | StringAndURI | The "alg" (algorithm) header |
| | | | parameter identifies the |
| | | | cryptographic algorithm used |
| | | | to secure the JWT. A list of |
| | | | reserved alg values is in |
| | | | Table 4. The processing of |
| | | | the "alg" (algorithm) header |
| | | | parameter, if present, |
| | | | requires that the value of |
| | | | the "alg" header parameter |
| | | | MUST be one that is both |
| | | | supported and for which there |
| | | | exists a key for use with |
| | | | that algorithm associated |
| | | | with the issuer of the JWT. |
| | | | This header parameter is |
| | | | REQUIRED. |
Jones, et al. Expires July 8, 2011 [Page 11]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
| typ | string | String | The "typ" (type) header |
| | | | parameter is used to declare |
| | | | that this data structure is a |
| | | | JWT. If a "typ" parameter is |
| | | | present, it is RECOMMENDED |
| | | | that its value be "JWT". |
| | | | This header parameter is |
| | | | OPTIONAL. |
| jku | string | URL | The "jku" (JSON Key URL) |
| | | | header parameter is a URL |
| | | | that points to JSON-encoded |
| | | | public key certificates that |
| | | | can be used to validate the |
| | | | signature. The specification |
| | | | for this encoding is TBD. |
| | | | This header parameter is |
| | | | OPTIONAL. |
| kid | string | String | The "kid" (key ID) header |
| | | | parameter is a hint |
| | | | indicating which specific key |
| | | | owned by the signer should be |
| | | | used to validate the |
| | | | signature. This allows |
| | | | signers to explicitly signal |
| | | | a change of key to |
| | | | recipients. Omitting this |
| | | | parameter is equivalent to |
| | | | setting it to an empty |
| | | | string. The interpretation |
| | | | of the contents of the "kid" |
| | | | parameter is unspecified. |
| | | | This header parameter is |
| | | | OPTIONAL. |
| x5u | string | URL | The "x5u" (X.509 URL) header |
| | | | parameter is a URL that |
| | | | points to an X.509 public key |
| | | | certificate that can be used |
| | | | to validate the signature. |
| | | | This certificate MUST conform |
| | | | to RFC 5280 [RFC5280]. This |
| | | | header parameter is OPTIONAL. |
Jones, et al. Expires July 8, 2011 [Page 12]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
| x5t | string | String | The "x5t" (x.509 certificate |
| | | | thumbprint) header parameter |
| | | | provides a base64url encoded |
| | | | SHA-256 thumbprint (a.k.a. |
| | | | digest) of the DER encoding |
| | | | of an X.509 certificate that |
| | | | can be used to match a |
| | | | certificate. This header |
| | | | parameter is OPTIONAL. |
+-----------+--------+--------------+-------------------------------+
Table 3: Reserved Header Parameter Definitions
Additional reserved header parameter names MAY be defined via the
IANA JSON Web Token Header Parameters registry, as per Section 10.
The syntax values used above and in Table 1 are defined in Table 2.
5.2. Public Header Parameter Names
Additional header parameter names can be defined by those using JWTs.
However, in order to prevent collisions, any new header parameter
name or algorithm value SHOULD either be defined in the IANA JSON Web
Token Header Parameters registry or be defined as a URI that contains
a collision resistant namespace. 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 header
parameter name.
New header parameters should be introduced sparingly, as they can
result in non-interoperable JWTs. Nonetheless, some extensions
needed for some use cases may require them, such as an extension to
enable the inclusion of multiple signatures.
5.3. Private Header Parameter Names
A producer and consumer of a JWT may agree to any header parameter
name that is not a Reserved Name Section 5.1 or a Public Name
Section 5.2. Unlike Public Names, these private names are subject to
collision and should be used with caution.
New header parameters should be introduced sparingly, as they can
result in non-interoperable JWTs.
6. Rules for Creating and Validating a JWT
To create a JWT one MUST follow these steps:
Jones, et al. Expires July 8, 2011 [Page 13]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
1. Create the payload content to be encoded as the Decoded JWT
Payload Segment. If the payload represents a JWT Claims Object,
then these steps for creating the Decoded JWT Payload Segment
also apply:
* Create a JSON object containing the desired claims. Note that
white space is explicitly allowed in the representation and no
canonicalization is performed before encoding.
* Translate this JSON object's Unicode code points into UTF-8,
as defined in RFC 3629 [RFC3629]. This is the Decoded JWT
Payload Segment.
2. Base64url encode the Decoded JWT Payload Segment. This encoding
becomes the JWT Payload Segment.
3. Create a JSON object containing a set of desired header
parameters. Note that white space is explicitly allowed in the
representation and no canonicalization is performed before
encoding.
4. Translate this JSON object's Unicode code points into UTF-8, as
defined in RFC 3629 [RFC3629].
5. Base64url encode the UTF-8 representation of this JSON object as
defined in this specification (without padding). This encoding
becomes a JWT Header Segment.
6. Construct a JWT Crypto Segment as defined for the particular
algorithm being used. The JWT Signing Input is always the
concatenation of a JWT Header Segment, a period ('.') character,
and the JWT Payload Segment. The "alg" header parameter MUST be
present in the JSON Header Segment, with the algorithm value
accurately representing the algorithm used to construct the JWT
Crypto Segment.
7. If the JWT Compact Serialization is being used, then:
* Concatenate the JWT Header Segment, the JWT Payload Segment
and then the JWT Crypto Segment in that order, separating each
by period characters, to create the JWT.
Else if the JWT JSON Serialization is being used, then:
* Create a JSON object with these three members: a "header"
member whose value is an array of JWT Header Segments, a
"payload" member whose value is the JWT Payload Segment, and a
"signature" member whose value is an array of JWT Crypto
Jones, et al. Expires July 8, 2011 [Page 14]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
Segments.
* If more than one signature is present, then repeat steps 3
through 6 for each header and crypto segment to produce
additional values for the header and signature arrays.
* The header and signature arrays must have the same number of
values, with each header value and corresponding signature
value being located at the same array index.
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. If the JWT Compact Serialization is being used, then:
* The JWT MUST contain two period characters.
* 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 Payload Segment; the
third is the JWT Crypto Segment.
Else if the JWT JSON Serialization is being used, then:
* The JSON MUST contain the three members "header", "payload",
and "signature" and MAY contain others, which MUST be ignored.
The payload member MUST be a string and the header and
signature members MUST be non-empty arrays of strings with
equal cardinality.
* Use a "header" member array value as the JWT Header Segment;
use the "payload" member value as the JWT Payload Segment; use
a "signature" member array value with the same index as the
"header" member array value used as the JWT Crypto Segment.
2. The JWT Payload Segment MUST be successfully base64url decoded
following the restriction given in this spec that no padding
characters have been used.
3. If the payload represents a JWT Claims Object, then these steps
for validating the Decoded JWT Payload Segment also apply:
* The Decoded JWT Payload Segment, which is the Decoded JWT
Claims Object, MUST be completely valid JSON syntax conforming
to RFC 4627 [RFC4627].
Jones, et al. Expires July 8, 2011 [Page 15]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
* When used in a security-related context, the Decoded JWT
Claims Object MUST be validated to only include claims whose
syntax and semantics are both understood and supported.
4. The JWT Header Segment MUST be successfully base64url decoded
following the restriction given in this spec that no padding
characters have been used.
5. The Decoded JWT Header Segment MUST be completely valid JSON
syntax conforming to RFC 4627 [RFC4627].
6. The JWT Crypto Segment MUST be successfully base64url decoded
following the restriction given in this spec that no padding
characters have been used.
7. The JWT Header Segment MUST be validated to only include
parameters and values whose syntax and semantics are both
understood and supported.
8. The JWT Crypto Segment MUST be successfully validated against the
JWT Header Segment and JWT Payload Segment in the manner defined
for the algorithm being used, which MUST be accurately
represented by the value of the "alg" header parameter, which
MUST be present.
9. If the JWT JSON Serialization is being used, then repeat steps 4
to 8 for each element of the header and signature arrays.
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 11.
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.
Jones, et al. Expires July 8, 2011 [Page 16]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
3. Comparisons between the two strings MUST be performed as a
Unicode code point to code point equality comparison.
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 specific cryptographic algorithms to sign the contents of
the JWT Header Segment and the JWT Payload Segment. The use of the
following algorithms for producing JWTs is defined in this section.
The table below is the list of "alg" header parameter values reserved
by this specification, each of which is explained in more detail in
the following sections:
+--------------------+----------------------------------------------+
| Alg Parameter | Algorithm |
| Value | |
+--------------------+----------------------------------------------+
| HS256 | HMAC using SHA-256 hash algorithm |
| HS384 | HMAC using SHA-384 hash algorithm |
| HS512 | HMAC using SHA-512 hash algorithm |
| RS256 | RSA using SHA-256 hash algorithm |
| RS384 | RSA using SHA-384 hash algorithm |
| RS512 | RSA using SHA-512 hash algorithm |
| ES256 | ECDSA using P-256 curve and SHA-256 hash |
| | algorithm |
| ES384 | ECDSA using P-384 curve and SHA-384 hash |
| | algorithm |
| ES512 | ECDSA using P-521 curve and SHA-512 hash |
| | algorithm |
+--------------------+----------------------------------------------+
Table 4: JSON Web Token Reserved Algorithm Values
Of these algorithms, only HMAC SHA-256 and RSA SHA-256 MUST be
implemented by conforming implementations. It is RECOMMENDED that
implementations also support the ECDSA P-256 SHA-256 algorithm.
Jones, et al. Expires July 8, 2011 [Page 17]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
Support for other algorithms is OPTIONAL.
The portion of a JWT that is signed is the same for all algorithms:
the concatenation of the JWT Header Segment, a period ('.')
character, and the JWT Payload Segment. This character sequence is
referred to as the JWT Signing Input. Note that in the JWT Compact
Serialization, this corresponds to the portion of the JWT
representation preceding the second period character. The UTF-8
representation of the JWT Signing Input is passed to the respective
signing algorithms.
8.1. Signing a JWT with HMAC SHA-256
Hash based Message Authentication Codes (HMACs) enable one to use a
secret plus a cryptographic hash function to generate a Message
Authentication Code (MAC). This can be used to demonstrate that the
MAC matches the hashed content, in this case the JWT Signing Input,
which therefore demonstrates that whoever generated the MAC was in
possession of the secret.
The algorithm for implementing and validating HMACs is provided in
RFC 2104 [RFC2104]. Although any HMAC can be used with JWTs, this
section defines the use of the SHA-256 cryptographic hash function as
defined in FIPS 180-3 [FIPS.180-3]. The reserved "alg" header
parameter value "HS256" is used in the JWT Header Segment to indicate
that the JWT Crypto Segment contains a base64url encoded HMAC SHA-256
HMAC value.
The HMAC SHA-256 MAC is generated as follows:
1. Apply the HMAC SHA-256 algorithm to the UTF-8 representation of
the JWT Signing Input using the shared key to produce an HMAC.
2. Base64url encode the HMAC as defined in this document.
The output is placed in the JWT Crypto Segment for that JWT.
The HMAC SHA-256 MAC on a JWT is validated as follows:
1. Apply the HMAC SHA-256 algorithm to the UTF-8 representation of
the JWT Signing Input of the JWT using the shared key.
2. Base64url encode the previously generated HMAC as defined in this
document.
3. If the JWT Crypto Segment and the previously calculated value
exactly match, then one has confirmation that the key was used to
generate the HMAC on the JWT and that the contents of the JWT
Jones, et al. Expires July 8, 2011 [Page 18]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
have not be tampered with.
4. If the validation fails, the token MUST be rejected.
Signing with the HMAC SHA-384 and HMAC SHA-512 algorithms is
performed identically to the procedure for HMAC SHA-256 - just with
correspondingly longer key and result values.
8.2. Signing a JWT with RSA SHA-256
This section defines the use of the RSASSA-PKCS1-v1_5 signature
algorithm as defined in RFC 3447 [RFC3447], Section 8.2 (commonly
known as PKCS#1), using SHA-256 as the hash function. Note that the
use of the RSASSA-PKCS1-v1_5 algorithm is described in FIPS 186-3
[FIPS.186-3], Section 5.5, as is the SHA-256 cryptographic hash
function, which is defined in FIPS 180-3 [FIPS.180-3]. The reserved
"alg" header parameter value "RS256" is used in the JWT Header
Segment to indicate that the JWT Crypto Segment contains an RSA SHA-
256 signature.
A 2048-bit or longer key length MUST be used with this algorithm.
The RSA SHA-256 signature is generated as follows:
1. Let K be the signer's RSA private key and let M be the UTF-8
representation of the JWT Signing Input.
2. Compute the octet string S = RSASSA-PKCS1-V1_5-SIGN (K, M) using
SHA-256 as the hash function.
3. Base64url encode the octet string S, as defined in this document.
The output is placed in the JWT Crypto Segment for that JWT.
The RSA SHA-256 signature on a JWT is validated as follows:
1. Take the JWT Crypto Segment and base64url decode it into an octet
string S. If decoding fails, then the token MUST be rejected.
2. Let M be the UTF-8 representation of the JWT Signing Input and
let (n, e) be the public key corresponding to the private key
used by the signer.
3. Validate the signature with RSASSA-PKCS1-V1_5-VERIFY ((n, e), M,
S) using SHA-256 as the hash function.
4. If the validation fails, the token MUST be rejected.
Jones, et al. Expires July 8, 2011 [Page 19]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
Signing with the RSA SHA-384 and RSA SHA-512 algorithms is performed
identically to the procedure for RSA SHA-256 - just with
correspondingly longer key and result values.
8.3. Signing a JWT with ECDSA P-256 SHA-256
The Elliptic Curve Digital Signature Algorithm (ECDSA) is defined by
FIPS 186-3 [FIPS.186-3]. ECDSA provides for the use of Elliptic
Curve cryptography, which is able to provide equivalent security to
RSA cryptography but using shorter key lengths and with greater
processing speed. This means that ECDSA signatures will be
substantially smaller in terms of length than equivalently strong RSA
Digital Signatures.
This specification defines the use of ECDSA with the P-256 curve and
the SHA-256 cryptographic hash function. The P-256 curve is also
defined in FIPS 186-3. The reserved "alg" header parameter value
"ES256" is used in the JWT Header Segment to indicate that the JWT
Crypto Segment contains an ECDSA P-256 SHA-256 signature.
A JWT is signed with an ECDSA P-256 SHA-256 signature as follows:
1. Generate a digital signature of the UTF-8 representation of the
JWT Signing Input using ECDSA P-256 SHA-256 with the desired
private key. The output will be the EC point (R, S), where R and
S are unsigned integers.
2. Turn R and S into byte arrays in big endian order. Each array
will be 32 bytes long.
3. Concatenate the two byte arrays in the order R and then S.
4. Base64url encode the 64 byte array as defined in this
specification.
The output becomes the JWT Crypto Segment for the JWT.
The following procedure is used to validate the ECDSA signature of a
JWT:
1. Take the JWT Crypto Segment and base64url decode it into a byte
array. If decoding fails, the token MUST be rejected.
2. The output of the base64url decoding MUST be a 64 byte array.
3. Split the 64 byte array into two 32 byte arrays. The first array
will be R and the second S. Remember that the byte arrays are in
big endian byte order; please check the ECDSA validator in use to
Jones, et al. Expires July 8, 2011 [Page 20]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
see what byte order it requires.
4. Submit the UTF-8 representation of the JWT Signing Input, R, S
and the public key (x, y) to the ECDSA P-256 SHA-256 validator.
5. If the validation fails, the token MUST be rejected.
The ECDSA validator will then determine if the digital signature is
valid, given the inputs. Note that ECDSA digital signature contains
a value referred to as K, which is a random number generated for each
digital signature instance. This means that two ECDSA digital
signatures using exactly the same input parameters will output
different signatures because their K values will be different. The
consequence of this is that one must validate an ECDSA signature by
submitting the previously specified inputs to an ECDSA validator.
Signing with the ECDSA P-384 SHA-384 and ECDSA P-521 SHA-512
algorithms is performed identically to the procedure for ECDSA P-256
SHA-256 - just with correspondingly longer key and result values.
8.4. Additional Algorithms
Additional algorithms MAY be used to protect JWTs with corresponding
"alg" header parameter values being defined to refer to them. Like
claim names, new "alg" header parameter values SHOULD either be
defined in the IANA JSON Web Token Algorithms registry or be a URI
that contains a collision resistant namespace. In particular, the
use of algorithm identifiers defined in XML DSIG [RFC3275] and
related specifications is permitted.
9. JWT Serialization Formats
JSON Web Tokens (JWTs) support two serialization formats: the JWT
Compact Serialization, which is more space efficient and intended for
uses where the token is passed as a simple string-valued parameter,
and the JWT JSON Serialization, which is more general, being able to
contain multiple signatures over the same content. The two
serialization formats are intended for use in different contexts.
9.1. JWT Compact Serialization
The JWT Compact Serialization represents a JWT as a string consisting
of three JWT Token Segments: the JWT Header Segment, the JWT Payload
Segment, and the JWT Crypto Segment, in that order, with the segments
being separated by period ('.') characters. It is intended for uses
where the token is passed as a simple string-valued parameter,
including in URLs.
Jones, et al. Expires July 8, 2011 [Page 21]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
The Compact Serialization contains only one signature to keep this
format simple. The example JWT in Section 3.1 uses the Compact
Serialization.
9.2. JWT JSON Serialization
The JWT JSON Serialization represents a JWT as a JSON object with
members for each of three kinds of JWT Token Segments: a "header"
member whose value is a non-empty array of JWT Header Segments, a
"payload" member whose value is the JWT Payload Segment, and a
"signature" member whose value is a non-empty array of JWT Crypto
Segments, where the cardinality of both arrays is the same.
Unlike the Compact Serialization, JWTs using the JSON Serialization
MAY contain multiple signatures. Each signature is represented as a
JWT Crypto Segment in the "signature" member array. For each
signature, there is a corresponding "header" member array element
that specifies the signature algorithm for that signature, and
potentially other information as well. Therefore, the syntax is:
{"header":["<header 1 contents>",...,"<header N contents>"],
"payload":"<payload contents>",
"signature":["<signature 1 contents>",...,"<signature N contents>"]
}
The i'th signature is computed on the concatenation of <header i
contents>.<payload contents>.
Appendix A.4 contains an example JWT using the JSON Serialization.
10. 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.
o A new IANA registry entitled "JSON Web Token Header Parameters"
for reserved header parameter names is defined in Section 5.1.
Inclusion in the registry is RFC Required in the RFC 5226
[RFC5226] sense for reserved JWT header parameter names that are
intended to be interoperable between implementations. The
registry will just record the reserved header parameter name and a
Jones, et al. Expires July 8, 2011 [Page 22]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
pointer to the RFC that defines it. This specification defines
inclusion of the header parameter names defined in Table 3.
o A new IANA registry entitled "JSON Web Token Algorithms" for
reserved values used with the "alg" header parameter values is
defined in Section 8.4. Inclusion in the registry is RFC Required
in the RFC 5226 [RFC5226] sense. The registry will just record
the "alg" value and a pointer to the RFC that defines it. This
specification defines inclusion of the algorithm values defined in
Table 4.
11. 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
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.
11.1. 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
Jones, et al. Expires July 8, 2011 [Page 23]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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.
12. Open Issues and Things To Be Done (TBD)
The following items remain to be done in this draft (and related
drafts):
o The specification will be a lot clearer if the signature portions
are cleanly separated from the claims token format and
serialization portions. Having tried it this way and being
dissatisfied with the sometimes unwieldy readability of the
result, I plan to perform the separation in the next draft.
o Consider whether there is a better term than "Digital Signature"
for the concept that includes both HMACs and digital signatures
using public keys.
o Consider whether we really want to allow private claim names and
header parameters 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.
o Clarify the optional ability to provide type information 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 Clarify the semantics of the "kid" (key ID) header parameter.
Open issues include: What happens if a kid header is received with
an unrecognized value? Is that an error? Should it be treated as
if it's empty? What happens if the header has a recognized value
but the value doesn't match the key associated with that value,
but it does match another key that is associated with the issuer?
Is that an error?
o The "x5t" parameter is currently specified as "a base64url encoded
SHA-256 thumbprint of the DER encoding of an X.509 certificate".
Jones, et al. Expires July 8, 2011 [Page 24]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
SHA-1 was traditionally used for certificate digests but
collisions are possible to create and can be used for denial of
service attacks within multi-tenant services. We need to
understand the compatibility issues of using SHA-256 thumbprints
instead. We also likely want to specify the digest algorithm
explicitly.
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 Since RFC 3447 Section 8 explicitly calls for people NOT to adopt
RSASSA-PKCS1 for new applications and instead requests that people
transition to RSASSA-PSS, we probably need some Security
Considerations text explaining why RSASSA-PKCS1 is being used
(it's what's commonly implemented) and what the potential
consequences are.
o Generalize the normative text on signing algorithms so that the
descriptions apply equally to the use of various key lengths - not
just HMAC SHA-256, RSA SHA-256, and ECDSA P-256 SHA-256.
o Add a table cross-referencing the algorithm name strings used in
standard software packages and specifications.
o Add Security Considerations text on timing attacks.
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 the related specification for encoding public keys using
JSON, as per the agreement documented at
http://self-issued.info/?p=390. This will be used by the "jku"
(JSON Key URL) header parameter.
o Write the companion encryption specification, per the agreements
documented at http://self-issued.info/?p=378.
13. References
Jones, et al. Expires July 8, 2011 [Page 25]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
13.1. Normative References
[FIPS.180-3]
National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", FIPS PUB 180-3, October 2008.
[FIPS.186-3]
National Institute of Standards and Technology, "Digital
Signature Standard (DSS)", FIPS PUB 186-3, June 2009.
[RFC1738] Berners-Lee, T., Masinter, L., and M. McCahill, "Uniform
Resource Locators (URL)", RFC 1738, December 1994.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
February 1997.
[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.
[RFC3447] Jonsson, J. and B. Kaliski, "Public-Key Cryptography
Standards (PKCS) #1: RSA Cryptography Specifications
Version 2.1", RFC 3447, February 2003.
[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.
[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.
Jones, et al. Expires July 8, 2011 [Page 26]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
[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, May 2008.
[USA15] Davis, M., Whistler, K., and M. Duerst, "Unicode
Normalization Forms", Unicode Standard Annex 15, 09 2009.
13.2. Informative References
[CanvasApp]
Facebook, "Canvas Applications", 2010.
[JSS] Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
September 2010.
[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.
Appendix A. JWT Examples
A.1. JWT using HMAC SHA-256
Jones, et al. Expires July 8, 2011 [Page 27]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
A.1.1. Encoding
The Decoded JWT Payload 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 Claims
Objects and no canonicalization is performed before encoding. The
following byte array contains the UTF-8 characters for the Decoded
JWT Payload 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 Payload Segment value:
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The following example JSON header object declares that the data
structure is a JSON Web Token (JWT) and the JWT Signing Input is
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
Concatenating the JWT Header Segment, a period character, and the JWT
Payload Segment yields this JWT Signing Input value (with line breaks
for display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The UTF-8 representation of the JWT Signing Input is the following
byte array:
[101, 121, 74, 48, 101, 88, 65, 105, 79, 105, 74, 75, 86, 49, 81,
Jones, et al. Expires July 8, 2011 [Page 28]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
105, 76, 65, 48, 75, 73, 67, 74, 104, 98, 71, 99, 105, 79, 105, 74,
73, 85, 122, 73, 49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51,
77, 105, 79, 105, 74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67,
74, 108, 101, 72, 65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84,
107, 122, 79, 68, 65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100,
72, 65, 54, 76, 121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76,
109, 78, 118, 98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73,
106, 112, 48, 99, 110, 86, 108, 102, 81]
HMACs are generated using keys. This example used 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,
98, 61, 34, 61, 46, 33, 114, 5, 46, 79, 8, 192, 205, 154, 245, 103,
208, 128, 163]
Running the HMAC SHA-256 algorithm on the UTF-8 representation of the
JWT Signing Input with this key yields the following byte array:
[116, 24, 223, 180, 151, 153, 224, 37, 79, 250, 96, 125, 216, 173,
187, 186, 22, 212, 37, 77, 105, 214, 191, 240, 91, 88, 5, 88, 83,
132, 141, 121]
Base64url encoding the above HMAC output yields the JWT Crypto
Segment value:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Combining these segments in the order Header.Payload.Signature with
period characters between the segments yields this complete JWT using
the JWT Compact Serialization (with line breaks for display purposes
only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
A.1.2. Decoding
Decoding the JWT first requires removing the base64url encoding from
the JWT Header Segment, the JWT Payload Segment, and the JWT Crypto
Segment. We base64url decode the segments per Section 7 and turn
them into the corresponding byte arrays. We translate the header
segment byte array containing UTF-8 encoded characters into the
Decoded JWT Header Segment string. Likewise, if the payload
represents a JWT Claims Object, we translate the payload segment byte
Jones, et al. Expires July 8, 2011 [Page 29]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
array containing UTF-8 encoded characters into a Decoded JWT Claims
Object string.
A.1.3. Validating
Next we validate the decoded results. Since the "alg" parameter in
the header is "HS256", we validate the HMAC SHA-256 signature
contained in the JWT Crypto Segment. If any of the validation steps
fail, the token MUST be rejected.
First, we validate that the decoded JWT Header Segment string is
legal JSON.
If the payload represents a JWT Claims Object, we also validate that
the decoded JWT Payload Segment string is legal JSON.
To validate the signature, we repeat the previous process of using
the correct key and the UTF-8 representation of the JWT Signing Input
as input to a SHA-256 HMAC function and then taking the output and
determining if it matches the Decoded JWT Crypto Segment. If it
matches exactly, the token has been validated.
A.2. JWT using RSA SHA-256
A.2.1. Encoding
The Decoded JWT Payload 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 Payload 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:
Jones, et al. Expires July 8, 2011 [Page 30]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
eyJhbGciOiJSUzI1NiJ9
Concatenating the JWT Header Segment, a period character, and the JWT
Payload Segment yields this JWT Signing Input value (with line breaks
for display purposes only):
eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The UTF-8 representation of the JWT Signing Input is the following
byte array:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 83, 85, 122, 73,
49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105,
74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72,
65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68,
65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76,
121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118,
98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48,
99, 110, 86, 108, 102, 81]
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:
Jones, et al. Expires July 8, 2011 [Page 31]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
+-----------+-------------------------------------------------------+
| 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] |
Jones, et al. Expires July 8, 2011 [Page 32]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
| 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] |
+-----------+-------------------------------------------------------+
The RSA private key (n, d) is then passed to the RSA signing
function, which also takes the hash type, SHA-256, and the UTF-8
representation of the JWT Signing Input as inputs. The result of the
signature is a byte array S, which represents a big endian integer.
In this example, S is:
Jones, et al. Expires July 8, 2011 [Page 33]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
+--------+----------------------------------------------------------+
| Result | Value |
| Name | |
+--------+----------------------------------------------------------+
| S | [112, 46, 33, 137, 67, 232, 143, 209, 30, 181, 216, 45, |
| | 191, 120, 69, 243, 65, 6, 174, 27, 129, 255, 247, 115, |
| | 17, 22, 173, 209, 113, 125, 131, 101, 109, 66, 10, 253, |
| | 60, 150, 238, 221, 115, 162, 102, 62, 81, 102, 104, 123, |
| | 0, 11, 135, 34, 110, 1, 135, 237, 16, 115, 249, 69, 229, |
| | 130, 173, 252, 239, 22, 216, 90, 121, 142, 232, 198, |
| | 109, 219, 61, 184, 151, 91, 23, 208, 148, 2, 190, 237, |
| | 213, 217, 217, 112, 7, 16, 141, 178, 129, 96, 213, 248, |
| | 4, 12, 167, 68, 87, 98, 184, 31, 190, 127, 249, 217, 46, |
| | 10, 231, 111, 36, 242, 91, 51, 187, 230, 244, 74, 230, |
| | 30, 177, 4, 10, 203, 32, 4, 77, 62, 249, 18, 142, 212, |
| | 1, 48, 121, 91, 212, 189, 59, 65, 238, 202, 208, 102, |
| | 171, 101, 25, 129, 253, 228, 141, 247, 127, 55, 45, 195, |
| | 139, 159, 175, 221, 59, 239, 177, 139, 93, 163, 204, 60, |
| | 46, 176, 47, 158, 58, 65, 214, 18, 202, 173, 21, 145, |
| | 18, 115, 160, 95, 35, 185, 232, 56, 250, 175, 132, 157, |
| | 105, 132, 41, 239, 90, 30, 136, 121, 130, 54, 195, 212, |
| | 14, 96, 69, 34, 165, 68, 200, 242, 122, 122, 45, 184, 6, |
| | 99, 209, 108, 247, 202, 234, 86, 222, 64, 92, 178, 33, |
| | 90, 69, 178, 194, 85, 102, 181, 90, 193, 167, 72, 160, |
| | 112, 223, 200, 163, 42, 70, 149, 67, 208, 25, 238, 251, |
| | 71] |
+--------+----------------------------------------------------------+
Base64url encoding the signature produces this value for the JWT
Crypto Segment:
cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw
Combining these segments in the order Header.Payload.Signature with
period characters between the segments yields this complete JWT using
the JWT Compact Serialization (with line breaks for display purposes
only):
eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw
A.2.2. Decoding
Decoding the JWT from this example requires processing the JWT Header
Segment and JWT Payload Segment exactly as done in the first example.
Jones, et al. Expires July 8, 2011 [Page 34]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
A.2.3. Validating
Since the "alg" parameter in the header is "RS256", we validate the
RSA SHA-256 signature contained in the JWT Crypto Segment. If any of
the validation steps fail, the token MUST be rejected.
First, we validate that the decoded JWT Header Segment string is
legal JSON.
If the payload represents a JWT Claims Object, we also validate that
the decoded JWT Payload Segment string is legal JSON.
Validating the JWT Crypto Segment is a little different from the
previous example. First, we base64url decode the JWT Crypto Segment
to produce a signature S to check. We then pass (n, e), S and the
UTF-8 representation of the JWT Signing Input to an RSA signature
verifier that has been configured to use the SHA-256 hash function.
A.3. JWT using ECDSA P-256 SHA-256
A.3.1. Encoding
The Decoded JWT Payload 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 Payload Segment will therefore be the same, its
computation is not repeated here. However, the Decoded JWT Header
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
Concatenating the JWT Header Segment, a period character, and the JWT
Payload Segment yields this JWT Signing Input value (with line breaks
for display purposes only):
Jones, et al. Expires July 8, 2011 [Page 35]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The UTF-8 representation of the JWT Signing Input is the following
byte array:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 73,
49, 78, 105, 74, 57, 46, 101, 121, 74, 112, 99, 51, 77, 105, 79, 105,
74, 113, 98, 50, 85, 105, 76, 65, 48, 75, 73, 67, 74, 108, 101, 72,
65, 105, 79, 106, 69, 122, 77, 68, 65, 52, 77, 84, 107, 122, 79, 68,
65, 115, 68, 81, 111, 103, 73, 109, 104, 48, 100, 72, 65, 54, 76,
121, 57, 108, 101, 71, 70, 116, 99, 71, 120, 108, 76, 109, 78, 118,
98, 83, 57, 112, 99, 49, 57, 121, 98, 50, 57, 48, 73, 106, 112, 48,
99, 110, 86, 108, 102, 81]
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] |
+-----------+-------------------------------------------------------+
The ECDSA private part d is then passed to an ECDSA signing function,
which also takes the curve type, P-256, the hash type, SHA-256, and
the UTF-8 representation of the JWT Signing Input as inputs. The
result of the signature is the EC point (R, S), where R and S are
unsigned integers. In this example, the R and S values, given as
byte arrays representing big endian integers are:
Jones, et al. Expires July 8, 2011 [Page 36]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
+--------+----------------------------------------------------------+
| Result | Value |
| Name | |
+--------+----------------------------------------------------------+
| R | [14, 209, 33, 83, 121, 99, 108, 72, 60, 47, 127, 21, 88, |
| | 7, 212, 2, 163, 178, 40, 3, 58, 249, 124, 126, 23, 129, |
| | 154, 195, 22, 158, 166, 101] |
| S | [197, 10, 7, 211, 140, 60, 112, 229, 216, 241, 45, 175, |
| | 8, 74, 84, 128, 166, 101, 144, 197, 242, 147, 80, 154, |
| | 143, 63, 127, 138, 131, 163, 84, 213] |
+--------+----------------------------------------------------------+
Concatenating the S array to the end of the R array and base64url
encoding the result produces this value for the JWT Crypto Segment:
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q
Combining these segments in the order Header.Payload.Signature with
period characters between the segments yields this complete JWT using
the JWT Compact Serialization (with line breaks for display purposes
only):
eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q
A.3.2. Decoding
Decoding the JWT from this example requires processing the JWT Header
Segment and JWT Payload Segment exactly as done in the first example.
A.3.3. Validating
Since the "alg" parameter in the header is "ES256", we validate the
ECDSA P-256 SHA-256 signature contained in the JWT Crypto Segment.
If any of the validation steps fail, the token MUST be rejected.
First, we validate that the decoded JWT Header Segment string is
legal JSON.
If the payload represents a JWT Claims Object, we also validate that
the decoded JWT Payload Segment string is legal JSON.
Validating the JWT Crypto Segment is a little different from the
first example. First, we base64url decode the JWT Crypto Segment as
in the previous examples but we then need to split the 64 member byte
array that must result into two 32 byte arrays, the first R and the
second S. We then pass (x, y), (R, S) and the UTF-8 representation of
Jones, et al. Expires July 8, 2011 [Page 37]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
the JWT Signing Input to an ECDSA signature verifier that has been
configured to use the P-256 curve with the SHA-256 hash function.
As explained in Section 8.3, the use of the k value in ECDSA means
that we cannot validate the correctness of the signature in the same
way we validated the correctness of the HMAC. Instead,
implementations MUST use an ECDSA validator to validate the
signature.
A.4. JWT using JSON Serialization
Previous example JWTs shown have used the JWT Compact Serialization.
This section contains an example JWT using the JWT JSON
Serialization. This example demonstrates the capability for
conveying multiple signatures for the same JWT.
A.4.1. Encoding
The Decoded JWT Payload Segment used in this example is the same as
in the previous examples:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Two signatures are used in this JWT: an RSA SHA-256 signature, for
which the header and signature values are the same as in
Appendix A.2, and an ECDSA P-256 SHA-256 signature, for which the
header and signature values are the same as in Appendix A.3. The two
Decoded JWT Header Segments used are:
{"alg":"RS256"}
and:
{"alg":"ES256"}
Since the computations for all JWT Token Segments used in this
example were already presented in previous examples, they are not
repeated here.
A JSON Serialization of this JWT is as follows:
{"header":[
"eyJhbGciOiJSUzI1NiJ9",
"eyJhbGciOiJFUzI1NiJ9"],
"payload":"eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ",
"signature":[
"cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw",
"DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q"]
}
Jones, et al. Expires July 8, 2011 [Page 38]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
A.4.2. Decoding
Decoding the JWT first requires removing the base64url encoding from
the array of JWT Header Segments, the JWT Payload Segment, and the
array of JWT Crypto Segments. We base64url decode the segments per
Section 7 and turn them into the corresponding byte arrays. We
translate the header segment byte arrays containing UTF-8 encoded
characters into Decoded JWT Header Segment strings. Likewise, if the
payload represents a JWT Claims Object, we translate the payload
segment byte array into a Decoded JWT Claims Object string.
A.4.3. Validating
If any of the validation steps fail, the token MUST be rejected.
First, we validate that the header and signature arrays contain the
same number of elements.
Next, we validate that the Decoded JWT Header Segment strings are all
legal JSON.
If the payload represents a JWT Claims Object, we also validate that
the decoded JWT Payload Segment string is legal JSON.
Finally, for each Decoded JWT Header Segment, we validate the
corresponding signature using the algorithm specified in the "alg"
parameter, which must be present.
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.
Jones, et al. Expires July 8, 2011 [Page 39]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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
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
Jones, et al. Expires July 8, 2011 [Page 40]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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. The signed content of a SWT
must be a set of claims, whereas the payload of a JWT, in general,
can be any base64url encoded content.
Appendix E. Acknowledgements
The authors acknowledge that the design of JWTs was intentionally
influenced by the design and simplicity of Simple Web Tokens [SWT].
Solutions for signing JSON tokens were also previously explored by
Magic Signatures [MagicSignatures], JSON Simple Sign [JSS], and
Canvas Applications [CanvasApp], all of which influenced this draft.
Appendix F. Document History
-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.
Jones, et al. Expires July 8, 2011 [Page 41]
Internet-Draft JSON Web Token (JWT) - Claims and Signing January 2011
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
John Panzer
Google
Email: jpanzer@google.com
Nat Sakimura
Nomura Research Institute
Email: n-sakimura@nri.co.jp
Paul Tarjan
Facebook
Email: paul.tarjan@facebook.com
Jones, et al. Expires July 8, 2011 [Page 42]