One document matched: draft-jones-json-web-token-01.xml
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<rfc category="std" docName="draft-jones-json-web-token-01"
ipr="trust200902">
<front>
<title>JSON Web Token (JWT) - Claims and Signing</title>
<author fullname="Michael B. Jones" initials="M.B." surname="Jones"> <!-- role="editor" -->
<organization>Microsoft</organization>
<address>
<email>mbj@microsoft.com</email>
<uri>http://self-issued.info/</uri>
</address>
</author>
<author fullname="Dirk Balfanz" initials="D." surname="Balfanz">
<organization>Google</organization>
<address>
<email>balfanz@google.com</email>
</address>
</author>
<author fullname="John Bradley" initials="J." surname="Bradley">
<organization>independent</organization>
<address>
<email>ve7jtb@ve7jtb.com</email>
</address>
</author>
<author fullname="Yaron Y. Goland" initials="Y.Y." surname="Goland">
<organization>Microsoft</organization>
<address>
<email>yarong@microsoft.com</email>
</address>
</author>
<author fullname="John Panzer" initials="J." surname="Panzer">
<organization>Google</organization>
<address>
<email>jpanzer@google.com</email>
</address>
</author>
<author fullname="Nat Sakimura" initials="N." surname="Sakimura">
<organization>Nomura Research Institute</organization>
<address>
<email>n-sakimura@nri.co.jp</email>
</address>
</author>
<author fullname="Paul Tarjan" initials="P." surname="Tarjan">
<organization>Facebook</organization>
<address>
<email>paul.tarjan@facebook.com</email>
</address>
</author>
<date day="04" month="January" year="2011" />
<area>Applications</area>
<keyword>RFC</keyword>
<keyword>Request for Comments</keyword>
<keyword>I-D</keyword>
<keyword>Internet-Draft</keyword>
<keyword>Assertion</keyword>
<keyword>Claim</keyword>
<keyword>Simple Web Token</keyword>
<keyword>Security Token</keyword>
<keyword>SWT</keyword>
<keyword>JSON Web Token</keyword>
<keyword>JWT</keyword>
<keyword>JavaScript Object Notation</keyword>
<keyword>JSON</keyword>
<abstract>
<t>
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.
</t>
<t>
The suggested pronunciation of JWT is the same as the English
word "jot".
</t>
</abstract>
<note title="Requirements Language">
<t>
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 <xref target="RFC2119">RFC 2119</xref>.
</t>
</note>
</front>
<middle>
<section title="Introduction">
<t>
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 <xref
target="RFC4627">RFC 4627</xref>) 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.
</t>
<t>
The suggested pronunciation of JWT is the same as the English
word "jot".
</t>
</section>
<section title="Terminology">
<t>
<list style="hanging">
<t hangText="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.
</t>
<t hangText="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.
</t>
<t hangText="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.
</t>
<t hangText="JWT Token Segment">
One of the three parts that make up a JSON Web Token
(JWT). JWT Token Segments are always base64url encoded
values.
</t>
<t hangText="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.
</t>
<t hangText="JWT Payload Segment">
A JWT Token Segment containing base64url encoded
content. This may be a JWT Claims Object.
</t>
<t hangText="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.
</t>
<t hangText="Decoded JWT Header Segment">
A JWT Header Segment that has been base64url decoded
back into a JSON object.
</t>
<t hangText="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.
</t>
<t hangText="Decoded JWT Crypto Segment">
A JWT Crypto Segment that has been base64url decoded back
into cryptographic material.
</t>
<t hangText="JWT Claims Object">
A base64url encoded JSON object that represents the claims
contained in the JWT.
</t>
<t hangText="Decoded JWT Claims Object">
A JSON object that represents the claims contained in the JWT.
</t>
<t hangText="JWT Signing Input">
The concatenation of the JWT Header Segment, a period
('.') character, and the JWT Payload Segment.
</t>
<t hangText="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.
</t>
<t hangText="Base64url Encoding">
For the purposes of this specification, this term always
refers to the he URL- and filename-safe Base64 encoding
described in <xref target="RFC4648">RFC 4648</xref>,
Section 5, with the '=' padding characters omitted, as
permitted by Section 3.2; see <xref
target="base64urllogic"></xref> for more details.
</t>
<t hangText="Header Parameter Names">
The names of the members within the JSON object
represented in a JWT Header Segment.
</t>
<t hangText="Header Parameter Values">
The values of the members within the JSON object
represented in a JWT Header Segment.
</t>
<t hangText="Claim Names">
The names of the members of the JSON object represented
in a JWT Claims Object.
</t>
<t hangText="Claim Values">
The values of the members of the JSON object represented
in a JWT Claims Object.
</t>
</list>
</t>
</section>
<section title="JSON Web Token (JWT) Overview">
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<section title="Example JWT" anchor="ExampleJWT">
<t>
The following is an example of a JSON object that can be
encoded to produce a JWT Claims Object:
</t>
<artwork><![CDATA[{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}]]></artwork>
<t>
Base64url encoding the UTF-8 representation of the JSON
object yields this JWT Claims Object, which is used as the
JWT Payload Segment:
</t>
<artwork><![CDATA[eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ]]></artwork>
<t>
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:
</t>
<artwork><![CDATA[{"typ":"JWT",
"alg":"HS256"}]]></artwork>
<t>
Base64url encoding the UTF-8 representation of the JSON
header object yields this JWT Header Segment value:
</t>
<artwork><![CDATA[eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9]]></artwork>
<t>
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
<xref target="SigningWithHMACSHA256"></xref>, yields this
JWT Crypto Segment value:
</t>
<artwork><![CDATA[dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk]]></artwork>
<t>
This computation is illustrated in more detail in <xref
target="HMACSHA256Example"></xref>.
</t>
</section>
</section>
<section title="JWT Claims">
<t>
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.
</t>
<t>
There are three classes of JWT Claim Names: Reserved Claim
Names, Public Claim Names, and Private Claim Names.
</t>
<section title="Reserved Claim Names" anchor="ReservedClaimName">
<t>
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 themselves to be short.
</t>
<texttable title="Reserved Claim Definitions" anchor="ClaimTable">
<ttcol align="left">Claim Name</ttcol>
<ttcol align="left">JSON Value Type</ttcol>
<ttcol align="left">Claim Syntax</ttcol>
<ttcol align="left">Claim Semantics</ttcol>
<c>exp</c>
<c>integer</c>
<c>IntDate</c>
<c>
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.
</c>
<c>iss</c>
<c>string</c>
<c>StringAndURI</c>
<c>
The "iss" (issuer) claim identifies the principal that
issued the JWT. The processing of this claim is generally
application specific. This claim is OPTIONAL.
</c>
<c>aud</c>
<c>string</c>
<c>StringAndURI</c>
<c>
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.
</c>
<c>typ</c>
<c>string</c>
<c>String</c>
<c>
The "typ" (type) claim is used to declare a type for the
contents of this JWT. This claim is OPTIONAL.
</c>
</texttable>
<t>
Additional reserved claim names MAY be defined via the IANA
JSON Web Token Claims registry, as per <xref target="IANA"
/>. The syntax values used above and in <xref
target="HeaderParameterTable" /> are defined as follows:
</t>
<texttable anchor="SyntaxDefinitions">
<ttcol align="left">Syntax Name</ttcol>
<ttcol align="left">Syntax Definition</ttcol>
<c>IntDate</c>
<c>
The number of seconds from 1970-01-01T0:0:0Z as measured
in UTC until the desired date/time. See <xref
target="RFC3339">RFC 3339</xref> for details regarding
date/times in general and UTC in particular.
</c>
<c>String</c>
<c>
Any string value MAY be used.
</c>
<c>StringAndURI</c>
<c>
Any string value MAY be used but a value containing a ":"
character MUST be a URI as defined in <xref
target="RFC3986">RFC 3986</xref>.
</c>
<c>URI</c>
<c>
A URI as defined in <xref target="RFC3986">RFC 3986</xref>.
</c>
<c>URL</c>
<c>
A URL as defined in <xref target="RFC1738">RFC 1738</xref>.
</c>
</texttable>
</section>
<section title="Public Claim Names" anchor="PublicClaimName">
<t>
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:
<list style="symbols">
<t>
Domain Names,
</t>
<t>
Object Identifiers (OIDs) as defined in the ITU-T X 660
and X 670 Recommendation series or
</t>
<t>
Universally Unique IDentifier (UUID) as defined in <xref
target="RFC4122">RFC 4122</xref>.
</t>
</list>
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.</t>
</section>
<section title="Private Claim Names" anchor="PrivateClaimName">
<t>
A producer and consumer of a JWT may agree to any claim
name that is not a Reserved Name <xref
target="ReservedClaimName"></xref> or a Public Name <xref
target="PublicClaimName"></xref>. Unlike Public Names,
these private names are subject to collision and should be
used with caution.
</t>
</section>
</section>
<section title="JWT Header">
<t>
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.
</t>
<section title="Reserved Header Parameter Names" anchor="ReservedHeaderParameterName">
<t>
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.
</t>
<texttable title="Reserved Header Parameter Definitions" anchor="HeaderParameterTable">
<ttcol align="left">Header Parameter Name</ttcol>
<ttcol align="left">JSON Value Type</ttcol>
<ttcol align="left">Header Parameter Syntax</ttcol>
<ttcol align="left">Header Parameter Semantics</ttcol>
<c>alg</c>
<c>string</c>
<c>StringAndURI</c>
<c>
The "alg" (algorithm) header parameter identifies the
cryptographic algorithm used to secure the JWT. A list of
reserved alg values is in <xref target="AlgTable"></xref>.
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.
</c>
<c>typ</c>
<c>string</c>
<c>String</c>
<c>
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.
</c>
<c>jku</c>
<c>string</c>
<c>URL</c>
<c>
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.
</c>
<c>kid</c>
<c>string</c>
<c>String</c>
<c>
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.
</c>
<c>x5u</c>
<c>string</c>
<c>URL</c>
<c>
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 <xref target="RFC5280">RFC 5280</xref>. This header
parameter is OPTIONAL.
</c>
<c>x5t</c>
<c>string</c>
<c>String</c>
<c>
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.
</c>
</texttable>
<t>
Additional reserved header parameter names MAY be defined
via the IANA JSON Web Token Header Parameters registry, as
per <xref target="IANA" />. The syntax values used above
and in <xref target="ClaimTable" /> are defined in <xref
target="SyntaxDefinitions" />.
</t>
</section>
<section title="Public Header Parameter Names" anchor="PublicHeaderParameterName">
<t>
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.
</t>
<t>
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.
</t>
</section>
<section title="Private Header Parameter Names" anchor="PrivateHeaderParameterName">
<t>
A producer and consumer of a JWT may agree to any header
parameter name that is not a Reserved Name <xref
target="ReservedHeaderParameterName"></xref> or a Public
Name <xref
target="PublicHeaderParameterName"></xref>. Unlike Public
Names, these private names are subject to collision and
should be used with caution.
</t>
<t>
New header parameters should be introduced sparingly, as
they can result in non-interoperable JWTs.
</t>
</section>
</section>
<section title="Rules for Creating and Validating a JWT">
<t>
To create a JWT one MUST follow these steps:
<list style="numbers">
<t>
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:
<list style="symbols">
<t>
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.
</t>
<t>
Translate this JSON object's Unicode code points into
UTF-8, as defined in <xref target="RFC3629">RFC
3629</xref>. This is the Decoded JWT Payload Segment.
</t>
</list>
</t>
<t>
Base64url encode the Decoded JWT Payload Segment. This
encoding becomes the JWT Payload Segment.
</t>
<t>
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.
</t>
<t>
Translate this JSON object's Unicode code points into
UTF-8, as defined in <xref target="RFC3629">RFC
3629</xref>.
</t>
<t>
Base64url encode the UTF-8 representation of this JSON
object as defined in this specification (without
padding). This encoding becomes a JWT Header Segment.
</t>
<t>
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.
</t>
<t>
If the JWT Compact Serialization is being used, then:
<list style="symbols">
<t>
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.
</t>
</list>
Else if the JWT JSON Serialization is being used, then:
<list style="symbols">
<t>
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 Segments.
</t>
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
</list>
</t>
<t>
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.
</t>
<t>
<list style="numbers">
<t>
If the JWT Compact Serialization is being used, then:
<list style="symbols">
<t>
The JWT MUST contain two period characters.
</t>
<t>
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.
</t>
</list>
Else if the JWT JSON Serialization is being used, then:
<list style="symbols">
<t>
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.
</t>
<t>
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.
</t>
</list>
</t>
<t>
The JWT Payload Segment MUST be successfully base64url
decoded following the restriction given in this spec that
no padding characters have been used.
</t>
<t>
If the payload represents a JWT Claims Object, then these
steps for validating the Decoded JWT Payload Segment also
apply:
<list style="symbols">
<t>
The Decoded JWT Payload Segment, which is the Decoded
JWT Claims Object, MUST be completely valid JSON
syntax conforming to <xref target="RFC4627">RFC
4627</xref>.
</t>
<t>
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.
</t>
</list>
</t>
<t>
The JWT Header Segment MUST be successfully base64url
decoded following the restriction given in this spec that
no padding characters have been used.
</t>
<t>
The Decoded JWT Header Segment MUST be completely valid
JSON syntax conforming to <xref target="RFC4627">RFC
4627</xref>.
</t>
<t>
The JWT Crypto Segment MUST be successfully base64url
decoded following the restriction given in this spec that
no padding characters have been used.
</t>
<t>
The JWT Header Segment MUST be validated to only include
parameters and values whose syntax and semantics are both
understood and supported.
</t>
<t>
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.
</t>
<t>
If the JWT JSON Serialization is being used, then repeat
steps 4 to 8 for each element of the header and signature
arrays.
</t>
</list>
</t>
<t>
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 <xref target="Security"></xref>.
</t>
<t>
Comparisons between JSON strings and other Unicode strings
MUST be performed as specified below:
</t>
<t>
<list style="numbers">
<t>
Remove any JSON applied escaping to produce an array of
Unicode code points.
</t>
<t>
<xref target="USA15">Unicode Normalization</xref> MUST NOT
be applied at any point to either the JSON string or to
the string it is to be compared against.
</t>
<t>
Comparisons between the two strings MUST be performed as a
Unicode code point to code point equality comparison.
</t>
</list>
</t>
</section>
<section title="Base64url encoding as used by JWTs" anchor="base64urllogic">
<t>
JWTs make use of the base64url encoding as defined in <xref
target="RFC4648">RFC 4648</xref>. 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.
</t>
<t>
For notes on implementing base64url encoding without padding,
see <xref target="base64urlnotes"></xref>.
</t>
</section>
<section title="Signing JWTs with Cryptographic Algorithms" anchor="Signing">
<t>
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:
</t>
<texttable title="JSON Web Token Reserved Algorithm Values" anchor="AlgTable">
<ttcol align="left">Alg Parameter Value</ttcol>
<ttcol align="left">Algorithm</ttcol>
<c>HS256</c>
<c>HMAC using SHA-256 hash algorithm</c>
<c>HS384</c>
<c>HMAC using SHA-384 hash algorithm</c>
<c>HS512</c>
<c>HMAC using SHA-512 hash algorithm</c>
<c>RS256</c>
<c>RSA using SHA-256 hash algorithm</c>
<c>RS384</c>
<c>RSA using SHA-384 hash algorithm</c>
<c>RS512</c>
<c>RSA using SHA-512 hash algorithm</c>
<c>ES256</c>
<c>ECDSA using P-256 curve and SHA-256 hash algorithm</c>
<c>ES384</c>
<c>ECDSA using P-384 curve and SHA-384 hash algorithm</c>
<c>ES512</c>
<c>ECDSA using P-521 curve and SHA-512 hash algorithm</c>
</texttable>
<t>
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. Support for other algorithms is OPTIONAL.
</t>
<t>
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.
</t>
<section title="Signing a JWT with HMAC SHA-256" anchor="SigningWithHMACSHA256">
<t>
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.
</t>
<t>
The algorithm for implementing and validating HMACs is
provided in <xref target="RFC2104">RFC 2104</xref>. Although
any HMAC can be used with JWTs, this section defines the use
of the SHA-256 cryptographic hash function as defined in <xref
target="FIPS.180-3">FIPS 180-3</xref>. 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.
</t>
<t>
The HMAC SHA-256 MAC is generated as follows:
<list style="numbers">
<t>
Apply the HMAC SHA-256 algorithm to the UTF-8
representation of the JWT Signing Input using the shared
key to produce an HMAC.
</t>
<t>
Base64url encode the HMAC as defined in this document.
</t>
</list>
The output is placed in the JWT Crypto Segment for that JWT.
</t>
<t>
The HMAC SHA-256 MAC on a JWT is validated as follows:
<list style="numbers">
<t>
Apply the HMAC SHA-256 algorithm to the UTF-8
representation of the JWT Signing Input of the JWT using
the shared key.
</t>
<t>
Base64url encode the previously generated HMAC as defined
in this document.
</t>
<t>
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 have not be tampered with.
</t>
<t>
If the validation fails, the token MUST be rejected.
</t>
</list>
</t>
<t>
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.
</t>
</section>
<section title="Signing a JWT with RSA SHA-256" anchor="DefiningRSA">
<t>
This section defines the use of the RSASSA-PKCS1-v1_5
signature algorithm as defined in <xref target="RFC3447">RFC
3447</xref>, 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 <xref
target="FIPS.186-3">FIPS 186-3</xref>, Section 5.5, as is the
SHA-256 cryptographic hash function, which is defined in <xref
target="FIPS.180-3">FIPS 180-3</xref>. 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.
</t>
<t>
A 2048-bit or longer key length MUST be used with this
algorithm.
</t>
<t>
The RSA SHA-256 signature is generated as follows:
<list style="numbers">
<t>
Let K be the signer's RSA private key and let M be the
UTF-8 representation of the JWT Signing Input.
</t>
<t>
Compute the octet string S = RSASSA-PKCS1-V1_5-SIGN (K,
M) using SHA-256 as the hash function.
</t>
<t>
Base64url encode the octet string S, as defined in this
document.
</t>
</list>
The output is placed in the JWT Crypto Segment for that JWT.
</t>
<t>
The RSA SHA-256 signature on a JWT is validated as follows:
<list style="numbers">
<t>
Take the JWT Crypto Segment and base64url decode it into
an octet string S. If decoding fails, then the token MUST
be rejected.
</t>
<t>
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.
</t>
<t>
Validate the signature with RSASSA-PKCS1-V1_5-VERIFY ((n,
e), M, S) using SHA-256 as the hash function.
</t>
<t>
If the validation fails, the token MUST be rejected.
</t>
</list>
</t>
<t>
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.
</t>
</section>
<section title="Signing a JWT with ECDSA P-256 SHA-256" anchor="DefiningECDSA">
<t>
The Elliptic Curve Digital Signature Algorithm (ECDSA) is
defined by <xref target="FIPS.186-3">FIPS 186-3</xref>. 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.
</t>
<t>
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.
</t>
<t>
A JWT is signed with an ECDSA P-256 SHA-256 signature as
follows:
<list style="numbers">
<t>
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.
</t>
<t>
Turn R and S into byte arrays in big endian order. Each
array will be 32 bytes long.
</t>
<t>
Concatenate the two byte arrays in the order R and then S.
</t>
<t>
Base64url encode the 64 byte array as defined in this
specification.
</t>
</list>
The output becomes the JWT Crypto Segment for the JWT.
</t>
<t>
The following procedure is used to validate the ECDSA
signature of a JWT:
<list style="numbers">
<t>
Take the JWT Crypto Segment and base64url decode it into a
byte array. If decoding fails, the token MUST be rejected.
</t>
<t>
The output of the base64url decoding MUST be a 64 byte
array.
</t>
<t>
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 see what byte order it requires.
</t>
<t>
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.
</t>
<t>
If the validation fails, the token MUST be rejected.
</t>
</list>
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.
</t>
<t>
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.
</t>
</section>
<section title="Additional Algorithms" anchor="MoreAlgs">
<t>
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 <xref target="RFC3275">XML DSIG</xref>
and related specifications is permitted.
</t>
</section>
</section>
<section title="JWT Serialization Formats" anchor="Serializations">
<t>
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.
</t>
<section title="JWT Compact Serialization" anchor="CompactSerialization">
<t>
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.
</t>
<t>
The Compact Serialization contains only one signature to
keep this format simple. The example JWT in <xref
target="ExampleJWT" /> uses the Compact Serialization.
</t>
</section>
<section title="JWT JSON Serialization" anchor="JSONSerialization">
<t>
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.
</t>
<t>
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:
</t>
<artwork><![CDATA[{"header":["<header 1 contents>",...,"<header N contents>"],
"payload":"<payload contents>",
"signature":["<signature 1 contents>",...,"<signature N contents>"]
}
]]></artwork>
<t>
The i'th signature is computed on the concatenation of
<header i contents>.<payload contents>.
</t>
<t>
<xref target="JSONSerializationExample" /> contains an
example JWT using the JSON Serialization.
</t>
</section>
</section>
<section title="IANA Considerations" anchor="IANA">
<t>
This specification calls for:
<list style="symbols">
<t>
A new IANA registry entitled "JSON Web Token Claims" for
reserved claim names is defined in <xref
target="ReservedClaimName"></xref>. Inclusion in the
registry is RFC Required in the <xref target="RFC5226">RFC
5226</xref> 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 <xref
target="ClaimTable"></xref>.
</t>
<t>
A new IANA registry entitled "JSON Web Token Header
Parameters" for reserved header parameter names is defined
in <xref target="ReservedHeaderParameterName"></xref>.
Inclusion in the registry is RFC Required in the <xref
target="RFC5226">RFC 5226</xref> 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
pointer to the RFC that defines it. This specification
defines inclusion of the header parameter names defined in
<xref target="HeaderParameterTable"></xref>.
</t>
<t>
A new IANA registry entitled "JSON Web Token Algorithms"
for reserved values used with the "alg" header parameter
values is defined in <xref target="MoreAlgs"></xref>. Inclusion
in the registry is RFC Required in the <xref
target="RFC5226">RFC 5226</xref> 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 <xref
target="AlgTable"></xref>.
</t>
</list>
</t>
</section>
<section title="Security Considerations" anchor="Security">
<t>
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.
</t>
<t>
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.
</t>
<section title="Unicode Comparison Security Issues">
<t>
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
<xref target="RFC4627">RFC 4627</xref>, Section 2.5).
</t>
<t>
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").
</t>
<t>
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.
</t>
</section>
</section>
<section title="Open Issues and Things To Be Done (TBD)" anchor="TBD">
<t>
The following items remain to be done in this draft (and related drafts):
</t>
<list style="symbols">
<t>
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.
</t>
<t>
Consider whether there is a better term than "Digital
Signature" for the concept that includes both HMACs and
digital signatures using public keys.
</t>
<t>
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.
</t>
<t>
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 <xref
target="RFC2045">MIME</xref> types.
</t>
<t>
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?
</t>
<t>
The "x5t" parameter is currently specified as "a base64url
encoded SHA-256 thumbprint of the DER encoding of an X.509
certificate". 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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
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.
</t>
<t>
Add a table cross-referencing the algorithm name strings
used in standard software packages and specifications.
</t>
<t>
Add Security Considerations text on timing attacks.
</t>
<t>
Finish the Security Considerations section.
</t>
<t>
Sort out what to do with the IANA registries if this is
first standardized as an OpenID specification.
</t>
<t>
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.
</t>
<t>
Write the companion encryption specification, per the
agreements documented at http://self-issued.info/?p=378.
</t>
</list>
</section>
</middle>
<back>
<references title="Normative References">
&RFC1738;
&RFC2045;
&RFC2104;
&rfc2119;
&RFC3339;
&RFC3447;
&RFC3629;
&RFC3986;
&RFC4627;
&RFC4648;
&RFC5226;
&RFC5280;
<reference anchor="FIPS.180-3">
<front>
<title>Secure Hash Standard (SHS)</title>
<author>
<organization>National Institute of Standards and
Technology</organization>
</author>
<date month="October" year="2008" />
</front>
<format target="http://csrc.nist.gov/publications/fips/fips180-3/fips180-3_final.pdf" type="PDF" />
<seriesInfo name="FIPS" value="PUB 180-3" />
</reference>
<reference anchor="FIPS.186-3">
<front>
<title>Digital Signature Standard (DSS)</title>
<author>
<organization>National Institute of Standards and
Technology</organization>
</author>
<date month="June" year="2009" />
</front>
<format target="http://csrc.nist.gov/publications/fips/fips186-3/fips_186-3.pdf" type="PDF" />
<seriesInfo name="FIPS" value="PUB 186-3" />
</reference>
<reference anchor="USA15">
<front>
<title>Unicode Normalization Forms</title>
<author fullname="Mark Davis" initials="M." surname="Davis">
<address>
<email>markdavis@google.com</email>
</address>
</author>
<author fullname="Ken Whistler" initials="K." surname="Whistler">
<address>
<email>ken@unicode.org</email>
</address>
</author>
<author fullname="Martin Dürst" initials="M."
surname="Dürst"></author>
<date day="03" month="09" year="2009" />
</front>
<seriesInfo name="Unicode Standard Annex" value="15" />
</reference>
</references>
<references title="Informative References">
&OASIS.saml-core-2.0-os;
&W3C.CR-xml11-20021015;
&RFC3275;
&RFC4122;
<reference anchor="SWT">
<front>
<title>Simple Web Token (SWT)</title>
<author fullname="Dick Hardt" initials="D." surname="Hardt"></author>
<author fullname="Yaron Y. Goland" initials="Y.Y." surname="Goland"></author>
<date month="November" year="2009" />
</front>
<format target="http://oauth-wrap-wg.googlegroups.com/web/SWT-v0.9.5.1.pdf?gda=Sn4MsEMAAABFB7PFAFiVedPtjcqT8uuIImHXUksNUKMXLyrSumAs_dF2tzlQ33RhT1wW8BFYO1QytiJ-HdGYYcPi_09pl8N7FWLveOaWjzbYnpnkpmxcWg" type="PDF" />
<seriesInfo name="Version" value="0.9.5.1" />
</reference>
<reference anchor="MagicSignatures">
<front>
<title>Magic Signatures</title>
<author fullname="John Panzer (editor)" initials="J." surname="Panzer (editor)"></author>
<author fullname="Ben Laurie" initials="B." surname="Laurie"></author>
<author fullname="Dirk Balfanz" initials="D." surname="Balfanz"></author>
<date month="August" year="2010" />
</front>
<format target="http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-magicsig-experimental-00.html" type="HTML" />
</reference>
<reference anchor="JSS">
<front>
<title>JSON Simple Sign</title>
<author fullname="John Bradley" initials="J." surname="Bradley">
<organization>independent</organization>
</author>
<author fullname="Nat Sakimura (editor)" initials="N. " surname="Sakimura (editor)">
<organization>Nomura Research Institute</organization>
</author>
<date month="September" year="2010" />
</front>
<format target="http://jsonenc.info/jss/1.0/" type="HTML" />
</reference>
<reference anchor="CanvasApp">
<front>
<title>Canvas Applications</title>
<author fullname="Facebook" surname="Facebook"></author>
<date year="2010" />
</front>
<format target="http://developers.facebook.com/docs/authentication/canvas" type="HTML" />
</reference>
</references>
<section title="JWT Examples" anchor="JWTExamples">
<section title="JWT using HMAC SHA-256" anchor="HMACSHA256Example">
<section title="Encoding">
<t>
The Decoded JWT Payload Segment used in this example is:
</t>
<artwork><![CDATA[{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}]]></artwork>
<t>
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:
</t>
<t>
[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]
</t>
<t>
Base64url encoding the above yields the JWT Payload Segment value:
</t>
<artwork><![CDATA[eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ]]></artwork>
<t>
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:
</t>
<artwork><![CDATA[{"typ":"JWT",
"alg":"HS256"}]]></artwork>
<t>
The following byte array contains the UTF-8 characters for
the Decoded JWT Header Segment:
</t>
<t>
[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]
</t>
<t>
Base64url encoding this UTF-8 representation yields this
JWT Header Segment value:
</t>
<artwork><![CDATA[eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ]]></artwork>
<t>
The UTF-8 representation of the JWT Signing Input is the
following byte array:
</t>
<t>
[101, 121, 74, 48, 101, 88, 65, 105, 79, 105, 74, 75, 86, 49, 81, 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]
</t>
<t>
HMACs are generated using keys. This example used the key
represented by the following byte array:
</t>
<t>
[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]
</t>
<t>
Running the HMAC SHA-256 algorithm on the UTF-8
representation of the JWT Signing Input with this key
yields the following byte array:
</t>
<t>
[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]
</t>
<t>
Base64url encoding the above HMAC output yields the JWT Crypto
Segment value:
</t>
<artwork><![CDATA[dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk]]></artwork>
</section>
<section title="Decoding">
<t>
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 <xref target="base64urllogic"></xref> 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 array
containing UTF-8 encoded characters into a Decoded JWT
Claims Object string.
</t>
</section>
<section title="Validating">
<t>
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.
</t>
<t>
First, we validate that the decoded JWT Header Segment
string is legal JSON.
</t>
<t>
If the payload represents a JWT Claims Object, we also
validate that the decoded JWT Payload Segment string is
legal JSON.
</t>
<t>
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.
</t>
</section>
</section>
<section title="JWT using RSA SHA-256" anchor="RSASHA256Example">
<section title="Encoding">
<t>
The Decoded JWT Payload Segment used in this example is the
same as in the previous example:
</t>
<artwork><![CDATA[{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}]]></artwork>
<t>
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:
</t>
<artwork><![CDATA[{"alg":"RS256"}]]></artwork>
<t>
The following byte array contains the UTF-8 characters for
the Decoded JWT Header Segment:
</t>
<t>
[123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125]
</t>
<t>
Base64url encoding this UTF-8 representation yields this
JWT Header Segment value:
</t>
<artwork><![CDATA[eyJhbGciOiJSUzI1NiJ9]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ]]></artwork>
<t>
The UTF-8 representation of the JWT Signing Input is the
following byte array:
</t>
<t>
[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]
</t>
<t>
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:
</t>
<texttable>
<ttcol align="left">Parameter Name</ttcol>
<ttcol align="left">Value</ttcol>
<c>n</c>
<c>
[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]
</c>
<c>e</c>
<c>
[1, 0, 1]
</c>
<c>d</c>
<c>
[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]
</c>
</texttable>
<t>
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:
</t>
<texttable>
<ttcol align="left">Result Name</ttcol>
<ttcol align="left">Value</ttcol>
<c>S</c>
<c>
[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]
</c>
</texttable>
<t>
Base64url encoding the signature produces this value for
the JWT Crypto Segment:
</t>
<artwork><![CDATA[cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw]]></artwork>
</section>
<section title="Decoding">
<t>
Decoding the JWT from this example requires processing the
JWT Header Segment and JWT Payload Segment exactly as
done in the first example.
</t>
</section>
<section title="Validating">
<t>
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.
</t>
<t>
First, we validate that the decoded JWT Header Segment
string is legal JSON.
</t>
<t>
If the payload represents a JWT Claims Object, we also
validate that the decoded JWT Payload Segment string is
legal JSON.
</t>
<t>
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.
</t>
</section>
</section>
<section title="JWT using ECDSA P-256 SHA-256" anchor="ECDSASHA256Example">
<section title="Encoding">
<t>
The Decoded JWT Payload Segment used in this example is the
same as in the previous examples:
</t>
<artwork><![CDATA[{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}]]></artwork>
<t>
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:
</t>
<artwork><![CDATA[{"alg":"ES256"}]]></artwork>
<t>
The following byte array contains the UTF-8 characters for
the Decoded JWT Header Segment:
</t>
<t>
[123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125]
</t>
<t>
Base64url encoding this UTF-8 representation yields this
JWT Header Segment value:
</t>
<artwork><![CDATA[eyJhbGciOiJFUzI1NiJ9]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ]]></artwork>
<t>
The UTF-8 representation of the JWT Signing Input is the
following byte array:
</t>
<t>
[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]
</t>
<t>
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:
</t>
<texttable>
<ttcol align="left">Parameter Name</ttcol>
<ttcol align="left">Value</ttcol>
<c>x</c>
<c>
[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]
</c>
<c>y</c>
<c>
[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]
</c>
<c>d</c>
<c>
[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]
</c>
</texttable>
<t>
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:
</t>
<texttable>
<ttcol align="left">Result Name</ttcol>
<ttcol align="left">Value</ttcol>
<c>R</c>
<c>
[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]
</c>
<c>S</c>
<c>
[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]
</c>
</texttable>
<t>
Concatenating the S array to the end of the R array and
base64url encoding the result produces this value for the
JWT Crypto Segment:
</t>
<artwork><![CDATA[DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q]]></artwork>
<t>
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):
</t>
<artwork><![CDATA[eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q]]></artwork>
</section>
<section title="Decoding">
<t>
Decoding the JWT from this example requires processing the
JWT Header Segment and JWT Payload Segment exactly as
done in the first example.
</t>
</section>
<section title="Validating">
<t>
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.
</t>
<t>
First, we validate that the decoded JWT Header Segment
string is legal JSON.
</t>
<t>
If the payload represents a JWT Claims Object, we also
validate that the decoded JWT Payload Segment string is
legal JSON.
</t>
<t>
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
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.
</t>
<t>
As explained in <xref target="DefiningECDSA"></xref>, 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.
</t>
</section>
</section>
<section title="JWT using JSON Serialization" anchor="JSONSerializationExample">
<t>
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.
</t>
<section title="Encoding">
<t>
The Decoded JWT Payload Segment used in this example is the
same as in the previous examples:
</t>
<artwork><![CDATA[{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}]]></artwork>
<t>
Two signatures are used in this JWT: an RSA SHA-256
signature, for which the header and signature values are
the same as in <xref target="RSASHA256Example" />, and an
ECDSA P-256 SHA-256 signature, for which the header and
signature values are the same as in <xref
target="ECDSASHA256Example" />. The two Decoded JWT
Header Segments used are:
</t>
<artwork><![CDATA[{"alg":"RS256"}]]></artwork>
<t>
and:
</t>
<artwork><![CDATA[{"alg":"ES256"}]]></artwork>
<t>
Since the computations for all JWT Token Segments used in
this example were already presented in previous examples,
they are not repeated here.
</t>
<t>
A JSON Serialization of this JWT is as follows:
</t>
<artwork><![CDATA[{"header":[
"eyJhbGciOiJSUzI1NiJ9",
"eyJhbGciOiJFUzI1NiJ9"],
"payload":"eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ",
"signature":[
"cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw",
"DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSApmWQxfKTUJqPP3-Kg6NU1Q"]
}]]></artwork>
</section>
<section title="Decoding">
<t>
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 <xref
target="base64urllogic"></xref> 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.
</t>
</section>
<section title="Validating">
<t>
If any of the validation steps fail, the token MUST be
rejected.
</t>
<t>
First, we validate that the header and signature arrays
contain the same number of elements.
</t>
<t>
Next, we validate that the Decoded JWT Header Segment
strings are all legal JSON.
</t>
<t>
If the payload represents a JWT Claims Object, we also
validate that the decoded JWT Payload Segment string is
legal JSON.
</t>
<t>
Finally, for each Decoded JWT Header Segment, we validate
the corresponding signature using the algorithm specified
in the "alg" parameter, which must be present.
</t>
</section>
</section>
</section>
<section title="Notes on implementing base64url encoding without padding" anchor="base64urlnotes">
<t>
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.
</t>
<t>
To be concrete, example C# code implementing these functions
is shown below. Similar code could be used in other
languages.
</t>
<artwork><![CDATA[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
}]]></artwork>
<t>
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.
</t>
<t>
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.
</t>
<artwork>3 236 255 224 193</artwork>
<artwork>A-z_4ME</artwork>
</section>
<section title="Relationship of JWTs to SAML Tokens">
<t>
<xref target="OASIS.saml-core-2.0-os">SAML 2.0</xref> 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 <xref
target="W3C.CR-xml11-20021015">XML</xref> and <xref
target="RFC3275">XML DSIG</xref> only contributes to the size
of SAML tokens.
</t>
<t>
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 <xref target="RFC4627">JSON</xref>
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.
</t>
<t>
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.
</t>
</section>
<section title="Relationship of JWTs to Simple Web Tokens (SWTs)">
<t>
Both JWTs and Simple Web Tokens <xref target="SWT">SWT</xref>,
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.
</t>
</section>
<section title="Acknowledgements" anchor="Acknowledgements">
<t>
The authors acknowledge that the design of JWTs was
intentionally influenced by the design and simplicity of <xref
target="SWT">Simple Web Tokens</xref>. Solutions for signing
JSON tokens were also previously explored by <xref
target="MagicSignatures">Magic Signatures</xref>, <xref
target="JSS">JSON Simple Sign</xref>, and <xref
target="CanvasApp">Canvas Applications</xref>, all of which
influenced this draft.
</t>
</section>
<section title='Document History'>
<t>
-01
<list style='symbols'>
<t>
Draft incorporating consensus decisions reached at IIW.
</t>
</list>
</t>
<t>
-00
<list style='symbols'>
<t>
Public draft published before November 2010 IIW based upon
the JSON token convergence proposal incorporating input
from several implementers of related specifications.
</t>
</list>
</t>
</section>
</back>
</rfc>
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