JSON Web Token (JWT)
draft-jones-json-web-token-07
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Replaced".
|
|
|---|---|---|---|
| Authors | Michael B. Jones , Dirk Balfanz , John Bradley , Yaron Y. Goland , John Panzer , Nat Sakimura , Paul Tarjan | ||
| Last updated | 2011-12-14 (Latest revision 2011-10-31) | ||
| Replaced by | draft-ietf-oauth-json-web-token, RFC 7519 | ||
| RFC stream | (None) | ||
| Formats | |||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | I-D Exists | |
| Telechat date | (None) | ||
| Responsible AD | (None) | ||
| Send notices to | (None) |
draft-jones-json-web-token-07
Network Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track D. Balfanz
Expires: June 15, 2012 Google
J. Bradley
independent
Y. Goland
Microsoft
J. Panzer
Google
N. Sakimura
Nomura Research Institute
P. Tarjan
Facebook
December 13, 2011
JSON Web Token (JWT)
draft-jones-json-web-token-07
Abstract
JSON Web Token (JWT) is a means of representing claims to be
transferred between two parties. The claims in a JWT are encoded as
a JSON object that is digitally signed using JSON Web Signature (JWS)
and/or encrypted using JSON Web Encryption (JWE).
The suggested pronunciation of JWT is the same as the English word
"jot".
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on June 15, 2012.
Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. JSON Web Token (JWT) Overview . . . . . . . . . . . . . . . . 5
3.1. Example JWT . . . . . . . . . . . . . . . . . . . . . . . 6
4. JWT Claims . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Reserved Claim Names . . . . . . . . . . . . . . . . . . . 7
4.2. Public Claim Names . . . . . . . . . . . . . . . . . . . . 9
4.3. Private Claim Names . . . . . . . . . . . . . . . . . . . 10
5. JWT Header . . . . . . . . . . . . . . . . . . . . . . . . . . 10
6. Plaintext JWTs . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Example Plaintext JWT . . . . . . . . . . . . . . . . . . 11
7. Rules for Creating and Validating a JWT . . . . . . . . . . . 12
8. Cryptographic Algorithms . . . . . . . . . . . . . . . . . . . 15
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
10. Security Considerations . . . . . . . . . . . . . . . . . . . 15
10.1. Unicode Comparison Security Issues . . . . . . . . . . . . 16
11. Open Issues and Things To Be Done (TBD) . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.1. Normative References . . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . . 18
Appendix A. Relationship of JWTs to SAML Tokens . . . . . . . . . 19
Appendix B. Relationship of JWTs to Simple Web Tokens (SWTs) . . 19
Appendix C. Acknowledgements . . . . . . . . . . . . . . . . . . 19
Appendix D. Document History . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
JSON Web Token (JWT) is a compact token format intended for space
constrained environments such as HTTP Authorization headers and URI
query parameters. JWTs encode claims to be transmitted as a JSON
object (as defined in RFC 4627 [RFC4627]) that is base64url encoded
and digitally signed and/or encrypted. Signing is accomplished using
JSON Web Signature (JWS) [JWS]. Encryption is accomplished using
JSON Web Encryption (JWE) [JWE].
The suggested pronunciation of JWT is the same as the English word
"jot".
2. Terminology
JSON Web Token (JWT) A string consisting of three parts: the Encoded
JWT Header, the JWT Second Part, and the JWT Third Part, in that
order, with the parts being separated by period ('.') characters,
and each part containing base64url encoded content.
JWT Header A string representing a JSON object that describes the
cryptographic operations applied to the JWT. When the JWT is
signed, the JWT Header is the JWS Header. When the JWT is
encrypted, the JWT Header is the JWE Header.
Header Parameter Names The names of the members within the JWT
Header.
Header Parameter Values The values of the members within the JWT
Header.
JWT Second Part When the JWT is signed, the JWT Second Part is the
Encoded JWS Payload. When the JWT is encrypted, the JWT Second
Part is the Encoded JWE Encrypted Key.
JWT Third Part When the JWT is signed, the JWT Third Part is the
Encoded JWS Signature. When the JWT is encrypted, the JWT Third
Part is the Encoded JWE Ciphertext.
JWT Claims Set A string representing a JSON object that contains the
claims conveyed by the JWT. When the JWT is signed, the bytes of
the UTF-8 representation of the JWT Claims Set are base64url
encoded to create the Encoded JWS Payload. When the JWT is
encrypted, the bytes of the UTF-8 representation of the JWT Claims
Set are used as the JWE Plaintext.
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Claim Names The names of the members of the JSON object represented
by the JWT Claims Set.
Claim Values The values of the members of the JSON object
represented by the JWT Claims Set.
Encoded JWT Header Base64url encoding of the bytes of the UTF-8 RFC
3629 [RFC3629] representation of the JWT Header.
Base64url Encoding For the purposes of this specification, this term
always refers to the URL- and filename-safe Base64 encoding
described in RFC 4648 [RFC4648], Section 5, with the (non URL-
safe) '=' padding characters omitted, as permitted by Section 3.2.
(See Appendix C of [JWS] for notes on implementing base64url
encoding without padding.)
3. JSON Web Token (JWT) Overview
JWTs represent a set of claims as a JSON object that is base64url
encoded and digitally signed and/or encrypted. The JWT Claims Set
represents this JSON object. As per RFC 4627 [RFC4627] Section 2.2,
the JSON object consists of zero or more name/value pairs (or
members), where the names are strings and the values are arbitrary
JSON values. These members are the claims represented by the JWT.
The member names within the JWT Claims Set are referred to as Claim
Names. The corresponding values are referred to as Claim Values.
The bytes of the UTF-8 representation of the JWT Claims Set are
signed in the manner described in JSON Web Signature (JWS) [JWS]
and/or encrypted in the manner described in JSON Web Encryption (JWE)
[JWE].
The contents of the JWT Header describe the cryptographic operations
applied to the JWT Claims Set. If the JWT Header is a JWS Header, the
claims are signed. If the JWT Header is a JWE Header, the claims are
encrypted.
A JWT is represented as the concatenation of the Encoded JWT Header,
the JWT Second Part, and the JWT Third Part, in that order, with the
parts being separated by period ('.') characters. When signed, the
three parts of the JWT are the three parts of a JWS used to represent
the JWT. When encrypted, the three parts of the JWT are the three
parts of a JWE used to represent the JWT.
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3.1. Example JWT
The following example JWT Header declares that the encoded object is
a JSON Web Token (JWT) and the JWT is signed using the HMAC SHA-256
algorithm:
{"typ":"JWT",
"alg":"HS256"}
Base64url encoding the bytes of the UTF-8 representation of the JWT
Header yields this Encoded JWS Header value, which is used as the
Encoded JWT Header:
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
The following is an example of a JWT Claims Set:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Base64url encoding the bytes of the UTF-8 representation of the JSON
Claims Set yields this Encoded JWS Payload, which is used as the JWT
Second Part (with line breaks for display purposes only):
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly
9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
Signing the Encoded JWS Header and Encoded JWS Payload with the HMAC
SHA-256 algorithm and base64url encoding the signature in the manner
specified in [JWS], yields this Encoded JWS Signature, which is used
as the JWT Third Part:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Concatenating these parts in the order Header.Second.Third with
period characters between the parts yields this complete JWT (with
line breaks for display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
This computation is illustrated in more detail in [JWS], Appendix
A.1.
4. JWT Claims
The JWT Claims Set represents a JSON object whose members are the
claims conveyed by the JWT. The Claim Names within this object MUST
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be unique. Note however, that the set of claims that a JWT must
contain to be considered valid is context-dependent and is outside
the scope of this specification. When used in a security-related
context, implementations MUST understand and support all of the
claims present; otherwise, the JWT MUST be rejected for processing.
There are three classes of JWT Claim Names: Reserved Claim Names,
Public Claim Names, and Private Claim Names.
4.1. Reserved Claim Names
The following claim names are reserved. None of the claims defined
in the table below are intended to be mandatory, but rather, provide
a starting point for a set of useful, interoperable claims. All the
names are short because a core goal of JWTs is for the tokens to be
compact.
+-------+--------+-------------+------------------------------------+
| Claim | JSON | Claim | Claim Semantics |
| Name | Value | Syntax | |
| | Type | | |
+-------+--------+-------------+------------------------------------+
| exp | number | IntDate | The "exp" (expiration time) claim |
| | | | identifies the expiration time on |
| | | | or after which the token MUST NOT |
| | | | be accepted for processing. The |
| | | | processing of the "exp" claim |
| | | | requires that the current |
| | | | date/time MUST be before the |
| | | | expiration date/time listed in the |
| | | | "exp" claim. Implementers MAY |
| | | | provide for some small leeway, |
| | | | usually no more than a few |
| | | | minutes, to account for clock |
| | | | skew. This claim is OPTIONAL. |
| nbf | number | IntDate | The "nbf" (not before) claim |
| | | | identifies the time before which |
| | | | the token MUST NOT be accepted for |
| | | | processing. The processing of the |
| | | | "nbf" claim requires that the |
| | | | current date/time MUST be after or |
| | | | equal to the not-before date/time |
| | | | listed in the "nbf" claim. |
| | | | Implementers MAY provide for some |
| | | | small leeway, usually no more than |
| | | | a few minutes, to account for |
| | | | clock skew. This claim is |
| | | | OPTIONAL. |
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| iat | number | IntDate | The "iat" (issued at) claim |
| | | | identifies the time at which the |
| | | | JWT was issued. This claim can be |
| | | | used to determine the age of the |
| | | | token. This claim is OPTIONAL. |
| iss | string | StringOrURI | The "iss" (issuer) claim |
| | | | identifies the principal that |
| | | | issued the JWT. The processing of |
| | | | this claim is generally |
| | | | application specific. The "iss" |
| | | | value is case sensitive. This |
| | | | claim is OPTIONAL. |
| aud | string | StringOrURI | The "aud" (audience) claim |
| | | | identifies the audience that the |
| | | | JWT is intended for. The |
| | | | principal intended to process the |
| | | | JWT MUST be identified with the |
| | | | value of the audience claim. If |
| | | | the principal processing the claim |
| | | | does not identify itself with the |
| | | | identifier in the "aud" claim |
| | | | value then the JWT MUST be |
| | | | rejected. The interpretation of |
| | | | the audience value is generally |
| | | | application specific. The "aud" |
| | | | value is case sensitive. This |
| | | | claim is OPTIONAL. |
| prn | string | StringOrURI | The "prn" (principal) claim |
| | | | identifies the subject of the JWT. |
| | | | The processing of this claim is |
| | | | generally application specific. |
| | | | The "prn" value is case sensitive. |
| | | | This claim is OPTIONAL. |
| jti | string | String | The "jti" (JWT ID) claim provides |
| | | | a unique identifier for the JWT. |
| | | | The identifier value MUST be |
| | | | assigned in a manner that ensures |
| | | | that there is a negligible |
| | | | probability that the same value |
| | | | will be accidentally assigned to a |
| | | | different data object. The "jti" |
| | | | claim can be used to prevent the |
| | | | JWT from being replayed. The |
| | | | "jti" value is case sensitive. |
| | | | This claim is OPTIONAL. |
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| typ | string | String | The "typ" (type) claim is used to |
| | | | declare a type for the contents of |
| | | | this JWT Claims Set. The "typ" |
| | | | value is case sensitive. This |
| | | | claim is OPTIONAL. |
+-------+--------+-------------+------------------------------------+
Table 1: Reserved Claim Definitions
Additional reserved claim names MAY be defined via the IANA JSON Web
Token Claims registry, as per Section 9. The syntax values used
above are defined as follows:
+-------------+-----------------------------------------------------+
| Syntax Name | Syntax Definition |
+-------------+-----------------------------------------------------+
| IntDate | The number of seconds from 1970-01-01T0:0:0Z as |
| | measured in UTC until the desired date/time. See |
| | RFC 3339 [RFC3339] for details regarding date/times |
| | in general and UTC in particular. |
| String | Any string value MAY be used. |
| StringOrURI | Any string value MAY be used but a value containing |
| | a ":" character MUST be a URI as defined in RFC |
| | 3986 [RFC3986]. |
+-------------+-----------------------------------------------------+
Table 2: Claim Syntax Definitions
4.2. Public Claim Names
Claim names can be defined at will by those using JWTs. However, in
order to prevent collisions, any new claim name SHOULD either be
defined in the IANA JSON Web Token Claims registry or be defined as a
URI that contains a collision resistant namespace. Examples of
collision resistant namespaces include:
o Domain Names,
o Object Identifiers (OIDs) as defined in the ITU-T X.660 and X.670
Recommendation series, or
o Universally Unique IDentifier (UUID) as defined in RFC 4122
[RFC4122].
In each case, the definer of the name or value needs to take
reasonable precautions to make sure they are in control of the part
of the namespace they use to define the claim name.
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4.3. Private Claim Names
A producer and consumer of a JWT may agree to any claim name that is
not a Reserved Name Section 4.1 or a Public Name Section 4.2. Unlike
Public Names, these private names are subject to collision and should
be used with caution.
5. JWT Header
The members of the JSON object represented by the JWT Header describe
the cryptographic operations applied to the JWT and optionally,
additional properties of the JWT. The member names within the JWT
Header are referred to as Header Parameter Names. These names MUST
be unique. The corresponding values are referred to as Header
Parameter Values.
Implementations MUST understand the entire contents of the header;
otherwise, the JWT MUST be rejected for processing.
There are two ways of distinguishing whether the JWT is a JWS or JWE.
The first is by examining the "alg" (algorithm) header value. If the
value represents a signature algorithm, the JWT is a JWS; if it
represents an encryption algorithm, the JWT is a JWE. A second
method is determining whether an "enc" (encryption method) member
exists. If the "enc" member exists, the JWT is a JWE; otherwise, the
JWT is a JWS. Both methods will yield the same result.
JWS Header Parameters are defined by [JWS]. JWE Header Parameters
are defined by [JWE]. This specification further specifies the use
of the following header parameters in both the cases where the JWT is
a JWS and where it is a JWE.
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+----------+--------+-----------+-----------------------------------+
| Header | JSON | Header | Header Parameter Semantics |
| Paramete | Value | Parameter | |
| rName | Type | Syntax | |
+----------+--------+-----------+-----------------------------------+
| typ | string | String | The "typ" (type) header parameter |
| | | | is used to declare structural |
| | | | information about the JWT. In |
| | | | the normal case where nested |
| | | | signing or encryption operations |
| | | | are not employed, the use of this |
| | | | header parameter is OPTIONAL, and |
| | | | if present, it is RECOMMENDED |
| | | | that its value be either "JWT" or |
| | | | "http://openid.net/specs/jwt/1.0" |
| | | | .In the case that nested signing |
| | | | or encryption steps are employed |
| | | | ,the use of this header parameter |
| | | | is REQUIRED; in this case, the |
| | | | value MUST either be "JWS", to |
| | | | indicate that a nested signed JW |
| | | | Tis carried in this JWT or "JWE", |
| | | | to indicate that a nested |
| | | | encrypted JWT is carried in this |
| | | | JWT. |
+----------+--------+-----------+-----------------------------------+
Table 3: Reserved Header Parameter Usage
6. Plaintext JWTs
To support use cases where the JWT content is secured by a means
other than a signature and/or encryption contained within the token
(such as a signature on a data structure containing the token), JWTs
MAY also be created without a signature or encryption. Plaintext
JWTs MUST use the "alg" value "none", and are formatted identically
to a signed JWT with an empty signature. This means that the
base64url encoding of the bytes representing the UTF-8 encoding of
the JWT Claims Set is the JWT Second Part, and the empty string is
the JWT Third Part.
6.1. Example Plaintext JWT
The following example JWT Header declares that the encoded object is
a Plaintext JWT:
{"alg":"none"}
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Base64url encoding the bytes of the UTF-8 representation of the JWT
Header yields this Encoded JWT Header:
eyJhbGciOiJub25lIn0
The following is an example of a JWT Claims Set:
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Base64url encoding the bytes of the UTF-8 representation of the JSON
Claims Set yields this Encoded JWS Payload, which is used as the JWT
Second Part (with line breaks for display purposes only):
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The JWT Third Part is the empty string.
Concatenating these parts in the order Header.Second.Third with
period characters between the parts yields this complete JWT (with
line breaks for display purposes only):
eyJhbGciOiJub25lIn0
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
7. Rules for Creating and Validating a JWT
To create a JWT, one MUST perform these steps:
1. Create a JWT Claims Set containing the desired claims. Note that
white space is explicitly allowed in the representation and no
canonicalization is performed before encoding.
2. Let the Message be the bytes of the UTF-8 representation of the
JWT Claims Set.
3. Create a JWT Header containing the desired set of header
parameters. If the JWT is to be signed or encrypted, they MUST
conform to either the [JWS] or [JWE] specifications,
respectively. Else, if the JWT is to be plaintext, the "alg"
value "none" MUST be used. Note that white space is explicitly
allowed in the representation and no canonicalization is
performed before encoding.
4. Base64url encode the bytes of the UTF-8 representation of the JWT
Header. Let this be the Encoded JWT Header.
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5. Depending upon whether the JWT is to be signed, encrypted, or
plaintext, there are three cases:
* If the JWT is to be signed, create a JWS using the JWT Header
as the JWS Header and the Message as the JWS Payload; all
steps specified in [JWS] for creating a JWS MUST be followed.
Let the JWT Second Part be the Encoded JWS Payload and let the
JWT Third Part be the Encoded JWS Signature.
* If the JWT is to be encrypted, create a JWE using the JWT
Header as the JWE Header and the Message as the JWE Plaintext;
all steps specified in [JWE] for creating a JWE MUST be
followed. Let the JWT Second Part be the Encoded JWE
Encrypted Key and let the JWT Third Part be the Encoded JWS
Ciphertext.
* Else, if the JWT is to be plaintext, let the JWT Second Part
be the base64url encoding of the Message and let the JWT Third
Part be the empty string.
6. Concatenate the Encoded JWT Header, the JWT Second Part, and the
JWT Third Part in that order, separating each by period ('.')
characters.
7. If a nested signing or encryption operation will be performed,
let the Message be this concatenation, and return to Step 3,
using a "typ" value of either "JWS" or "JWE" respectively in the
new JWT Header created in that step.
8. Otherwise, let the resulting JWT be this concatenation.
When validating a JWT the following steps MUST be taken. If any of
the listed steps fails then the token MUST be rejected for
processing.
1. The JWT MUST contain exactly two period characters.
2. The JWT MUST be split on the two period characters resulting in
three strings. The first string is the Encoded JWT Header; the
second is the JWT Second Part; the third is the JWT Third Part.
3. The Encoded JWT Header MUST be successfully base64url decoded
following the restriction given in this specification that no
padding characters have been used.
4. The JWT Header MUST be completely valid JSON syntax conforming
to RFC 4627 [RFC4627].
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5. The JWT Header MUST be validated to only include parameters and
values whose syntax and semantics are both understood and
supported.
6. Determine whether the JWT is signed, encrypted, or plaintext by
examining the "alg" (algorithm) header value and optionally, the
"enc" (encryption method) header value, if present.
7. Depending upon whether the JWT signed, encrypted, or plaintext,
there are three cases:
* If the JWT is signed, all steps specified in [JWS] for
validating a JWS MUST be followed. Let the Message be the
result of base64url decoding the JWS Payload.
* If the JWT is encrypted, all steps specified in [JWE] for
validating a JWE MUST be followed. Let the Message be the
JWE Plaintext.
* Else, if the JWT is plaintext, let the Message be the result
of base64url decoding the JWE Second Part. The Third Part
MUST be verified to be the empty string.
8. If the JWT Header contains a "typ" value of either "JWS" or
"JWE", then the Message contains a JWT that was the subject of
nested signing or encryption operations, respectively. In this
case, return to Step 1, using the Message as the JWT.
9. Otherwise, let the JWT Claims Set be the Message.
10. The JWT Claims Set MUST be completely valid JSON syntax
conforming to RFC 4627 [RFC4627].
11. When used in a security-related context, the JWT Claims Set MUST
be validated to only include claims whose syntax and semantics
are both understood and supported.
Processing a JWT inevitably requires comparing known strings to
values in the token. For example, in checking what the algorithm is,
the Unicode string encoding "alg" will be checked against the member
names in the JWT Header to see if there is a matching header
parameter name. A similar process occurs when determining if the
value of the "alg" header parameter represents a supported algorithm.
Comparisons between JSON strings and other Unicode strings MUST be
performed as specified below:
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1. Remove any JSON applied escaping to produce an array of Unicode
code points.
2. Unicode Normalization [USA15] MUST NOT be applied at any point to
either the JSON string or to the string it is to be compared
against.
3. Comparisons between the two strings MUST be performed as a
Unicode code point to code point equality comparison.
8. Cryptographic Algorithms
JWTs use JSON Web Signature (JWS) [JWS] and JSON Web Encryption (JWE)
[JWE] to sign and/or encrypt the contents of the JWT.
Of the JWS signing algorithms, only HMAC SHA-256 MUST be implemented
by conforming JWT implementations. It is RECOMMENDED that
implementations also support the RSA SHA-256 and ECDSA P-256 SHA-256
algorithms. Support for other algorithms and key sizes is OPTIONAL.
If an implementation provides encryption capabilities, of the JWE
encryption algorithms, only RSA-PKCS1-1.5 with 2048 bit keys, AES-
128-CBC, and AES-256-CBC MUST be implemented by conforming
implementations. It is RECOMMENDED that implementations also support
ECDH-ES with 256 bit keys, AES-128-GCM, and AES-256-GCM. Support for
other algorithms and key sizes is OPTIONAL.
9. IANA Considerations
This specification calls for:
o A new IANA registry entitled "JSON Web Token Claims" for reserved
claim names is defined in Section 4.1. Inclusion in the registry
is RFC Required in the RFC 5226 [RFC5226] sense for reserved JWT
claim names that are intended to be interoperable between
implementations. The registry will just record the reserved claim
name and a pointer to the RFC that defines it. This specification
defines inclusion of the claim names defined in Table 1.
10. Security Considerations
TBD: Lots of work to do here. We need to remember to look into any
issues relating to security and JSON parsing. One wonders just how
secure most JSON parsing libraries are. Were they ever hardened for
security scenarios? If not, what kind of holes does that open up?
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Also, we need to walk through the JSON standard and see what kind of
issues we have especially around comparison of names. For instance,
comparisons of claim names and other parameters must occur after they
are unescaped. Need to also put in text about: Importance of keeping
secrets secret. Rotating keys. Strengths and weaknesses of the
different algorithms.
TBD: Need to put in text about why strict JSON validation is
necessary. Basically, that if malformed JSON is received then the
intent of the sender is impossible to reliably discern. One example
of malformed JSON that MUST be rejected is an object in which the
same member name occurs multiple times. While in non-security
contexts it's o.k. to be generous in what one accepts, in security
contexts this can lead to serious security holes. For example,
malformed JSON might indicate that someone has managed to find a
security hole in the issuer's code and is leveraging it to get the
issuer to issue "bad" tokens whose content the attacker can control.
TBD: Write about the need to secure the token content if a signature
is not contained in the JWT itself.
10.1. Unicode Comparison Security Issues
Claim names in JWTs are Unicode strings. For security reasons, the
representations of these names must be compared verbatim after
performing any escape processing (as per RFC 4627 [RFC4627], Section
2.5).
This means, for instance, that these JSON strings must compare as
being equal ("JWT", "\u004aWT"), whereas these must all compare as
being not equal to the first set or to each other ("jwt", "Jwt",
"JW\u0074").
JSON strings MAY contain characters outside the Unicode Basic
Multilingual Plane. For instance, the G clef character (U+1D11E) may
be represented in a JSON string as "\uD834\uDD1E". Ideally, JWT
implementations SHOULD ensure that characters outside the Basic
Multilingual Plane are preserved and compared correctly;
alternatively, if this is not possible due to these characters
exercising limitations present in the underlying JSON implementation,
then input containing them MUST be rejected.
11. Open Issues and Things To Be Done (TBD)
The following items remain to be done in this draft:
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o Provide an example of an encrypted JWT.
o Clarify the optional ability to provide type information for JWTs
and/or their parts. Specifically, clarify whether we need to
specify the "typ" Claim Name in addition to the Header Parameter,
whether it conveys syntax or semantics, and indeed, whether this
is the right approach. Also clarify the relationship between
these type values and MIME [RFC2045] types (if any).
o Think about how to best describe the concept currently described
as "the bytes of the UTF-8 representation of". Possible terms to
use instead of "bytes of" include "byte sequence", "octet series",
and "octet sequence". Also consider whether we want to add an
overall clarifying statement somewhere in each spec something like
"every place we say 'the UTF-8 representation of X', we mean 'the
bytes of the UTF-8 representation of X'". That would potentially
allow us to omit the "the bytes of" part everywhere else.
o Consider whether a media type should be proposed, such as
"application/jwt".
o Finish the Security Considerations section.
o Possibly write a companion specification that contains the former
JWT JSON Serialization.
12. References
12.1. Normative References
[JWS] Jones, M., Balfanz, D., Bradley, J., Goland, Y., Panzer,
J., Sakimura, N., and P. Tarjan, "JSON Web Signature
(JWS)", December 2011.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3339] Klyne, G., Ed. and C. Newman, "Date and Time on the
Internet: Timestamps", RFC 3339, July 2002.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
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[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4627] Crockford, D., "The application/json Media Type for
JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[USA15] Davis, M., Whistler, K., and M. Duerst, "Unicode
Normalization Forms", Unicode Standard Annex 15, 09 2009.
12.2. Informative References
[CanvasApp]
Facebook, "Canvas Applications", 2010.
[JSS] Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
September 2010.
[JWE] Jones, M., Rescorla, E., and J. Hildebrand, "JSON Web
Encryption (JWE)", December 2011.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
Signatures", August 2010.
[OASIS.saml-core-2.0-os]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocol for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
2.0-os, March 2005.
[RFC3275] Eastlake, D., Reagle, J., and D. Solo, "(Extensible Markup
Language) XML-Signature Syntax and Processing", RFC 3275,
March 2002.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
[SWT] Hardt, D. and Y. Goland, "Simple Web Token (SWT)",
Version 0.9.5.1, November 2009.
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[W3C.CR-xml11-20021015]
Cowan, J., "Extensible Markup Language (XML) 1.1", W3C
CR CR-xml11-20021015, October 2002.
Appendix A. Relationship of JWTs to SAML Tokens
SAML 2.0 [OASIS.saml-core-2.0-os] provides a standard for creating
tokens with much greater expressivity and more security options than
supported by JWTs. However, the cost of this flexibility and
expressiveness is both size and complexity. In addition, SAML's use
of XML [W3C.CR-xml11-20021015] and XML DSIG [RFC3275] only
contributes to the size of SAML tokens.
JWTs are intended to provide a simple token format that is small
enough to fit into HTTP headers and query arguments in URIs. It does
this by supporting a much simpler token model than SAML and using the
JSON [RFC4627] object encoding syntax. It also supports securing
tokens using Hash-based Message Authentication Codes (HMACs) and
digital signatures using a smaller (and less flexible) format than
XML DSIG.
Therefore, while JWTs can do some of the things SAML tokens do, JWTs
are not intended as a full replacement for SAML tokens, but rather as
a compromise token format to be used when space is at a premium.
Appendix B. Relationship of JWTs to Simple Web Tokens (SWTs)
Both JWTs and Simple Web Tokens SWT [SWT], at their core, enable sets
of claims to be communicated between applications. For SWTs, both
the claim names and claim values are strings. For JWTs, while claim
names are strings, claim values can be any JSON type. Both token
types offer cryptographic protection of their content: SWTs with HMAC
SHA-256 and JWTs with a choice of algorithms, including HMAC SHA-256,
RSA SHA-256, and ECDSA P-256 SHA-256.
Appendix C. Acknowledgements
The authors acknowledge that the design of JWTs was intentionally
influenced by the design and simplicity of Simple Web Tokens [SWT]
and ideas for JSON tokens that Dick Hardt discussed within the OpenID
community.
Solutions for signing JSON content were previously explored by Magic
Signatures [MagicSignatures], JSON Simple Sign [JSS], and Canvas
Applications [CanvasApp], all of which influenced this draft.
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Appendix D. Document History
-07
o Defined the "prn" (principal) claim to identify the subject of the
JWT.
o Defined the "jti" (JWT ID) claim to enable replay protection.
o Use the term "JWT Claims Set" rather than "JWT Claims Object"
since this is actually a string representing a JSON object and not
the JSON object itself.
o Moved "MUST" requirements from the Overview to later in the spec.
o Respect line length restrictions in examples.
o Applied other editorial improvements.
-06
o Reference and use content from [JWS] and [JWE], rather than
repeating it here.
o Simplified terminology to better match JWE, where the terms "JWT
Header" and "Encoded JWT Header" are now used, for instance,
rather than the previous terms "Decoded JWT Header Segment" and
"JWT Header Segment". Also changed to "Plaintext JWT" from
"Unsigned JWT".
o Describe how to perform nested encryption and signing operations.
o Changed "integer" to "number", since that is the correct JSON
type.
o Changed StringAndURI to StringOrURI.
-05
o Added the "nbf" (not before) claim and clarified the meaning of
the "iat" (issued at) claim.
-04
o Correct typo found by John Bradley: "the JWT Claim Segment is the
empty string" -> "the JWT Crypto Segment is the empty string".
-03
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o Added "http://openid.net/specs/jwt/1.0" as a token type identifier
URI for JWTs.
o Added "iat" (issued at) claim.
o Changed RSA SHA-256 from MUST be supported to RECOMMENDED that it
be supported. Rationale: Several people have objected to the
requirement for implementing RSA SHA-256, some because they will
only be using HMACs and symmetric keys, and others because they
only want to use ECDSA when using asymmetric keys, either for
security or key length reasons, or both.
o Defined "alg" value "none" to represent unsigned JWTs.
-02
o Split signature specification out into separate
draft-jones-json-web-signature-00. This split introduced no
semantic changes.
o The JWT Compact Serialization is now the only token serialization
format specified in this draft. The JWT JSON Serialization can
continue to be defined in a companion specification.
-01
o Draft incorporating consensus decisions reached at IIW.
-00
o Public draft published before November 2010 IIW based upon the
JSON token convergence proposal incorporating input from several
implementers of related specifications.
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
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Dirk Balfanz
Google
Email: balfanz@google.com
John Bradley
independent
Email: ve7jtb@ve7jtb.com
Yaron Y. Goland
Microsoft
Email: yarong@microsoft.com
John Panzer
Google
Email: jpanzer@google.com
Nat Sakimura
Nomura Research Institute
Email: n-sakimura@nri.co.jp
Paul Tarjan
Facebook
Email: pt@fb.com
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