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JOSE Working Group M. Jones
Internet-Draft Microsoft
Intended status: Standards Track J. Bradley
Expires: January 5, 2015 Ping Identity
N. Sakimura
NRI
July 4, 2014
JSON Web Signature (JWS)
draft-ietf-jose-json-web-signature-31
Abstract
JSON Web Signature (JWS) represents content secured with digital
signatures or Message Authentication Codes (MACs) using JavaScript
Object Notation (JSON) based data structures. Cryptographic
algorithms and identifiers for use with this specification are
described in the separate JSON Web Algorithms (JWA) specification and
an IANA registry defined by that specification. Related encryption
capabilities are described in the separate JSON Web Encryption (JWE)
specification.
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
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 January 5, 2015.
Copyright Notice
Copyright (c) 2014 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
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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.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. JSON Web Signature (JWS) Overview . . . . . . . . . . . . . . 6
3.1. JWS Compact Serialization Overview . . . . . . . . . . . . 7
3.2. JWS JSON Serialization Overview . . . . . . . . . . . . . 7
3.3. Example JWS . . . . . . . . . . . . . . . . . . . . . . . 8
4. JOSE Header . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.1. Registered Header Parameter Names . . . . . . . . . . . . 10
4.1.1. "alg" (Algorithm) Header Parameter . . . . . . . . . . 10
4.1.2. "jku" (JWK Set URL) Header Parameter . . . . . . . . . 10
4.1.3. "jwk" (JSON Web Key) Header Parameter . . . . . . . . 10
4.1.4. "kid" (Key ID) Header Parameter . . . . . . . . . . . 11
4.1.5. "x5u" (X.509 URL) Header Parameter . . . . . . . . . . 11
4.1.6. "x5c" (X.509 Certificate Chain) Header Parameter . . . 11
4.1.7. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header
Parameter . . . . . . . . . . . . . . . . . . . . . . 12
4.1.8. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint)
Header Parameter . . . . . . . . . . . . . . . . . . . 12
4.1.9. "typ" (Type) Header Parameter . . . . . . . . . . . . 12
4.1.10. "cty" (Content Type) Header Parameter . . . . . . . . 13
4.1.11. "crit" (Critical) Header Parameter . . . . . . . . . . 13
4.2. Public Header Parameter Names . . . . . . . . . . . . . . 14
4.3. Private Header Parameter Names . . . . . . . . . . . . . . 14
5. Producing and Consuming JWSs . . . . . . . . . . . . . . . . . 14
5.1. Message Signature or MAC Computation . . . . . . . . . . . 14
5.2. Message Signature or MAC Validation . . . . . . . . . . . 15
5.3. String Comparison Rules . . . . . . . . . . . . . . . . . 16
6. Key Identification . . . . . . . . . . . . . . . . . . . . . . 17
7. Serializations . . . . . . . . . . . . . . . . . . . . . . . . 17
7.1. JWS Compact Serialization . . . . . . . . . . . . . . . . 18
7.2. JWS JSON Serialization . . . . . . . . . . . . . . . . . . 18
8. TLS Requirements . . . . . . . . . . . . . . . . . . . . . . . 19
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
9.1. JSON Web Signature and Encryption Header Parameters
Registry . . . . . . . . . . . . . . . . . . . . . . . . . 21
9.1.1. Registration Template . . . . . . . . . . . . . . . . 21
9.1.2. Initial Registry Contents . . . . . . . . . . . . . . 22
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9.2. Media Type Registration . . . . . . . . . . . . . . . . . 23
9.2.1. Registry Contents . . . . . . . . . . . . . . . . . . 23
10. Security Considerations . . . . . . . . . . . . . . . . . . . 24
10.1. Key Entropy . . . . . . . . . . . . . . . . . . . . . . . 25
10.2. Chosen Plaintext Attacks . . . . . . . . . . . . . . . . . 25
10.3. Timing Attacks . . . . . . . . . . . . . . . . . . . . . . 25
10.4. Differences between Digital Signatures and MACs . . . . . 25
10.5. SHA-1 Certificate Thumbprints . . . . . . . . . . . . . . 26
10.6. JSON Security Considerations . . . . . . . . . . . . . . . 26
10.7. Unicode Comparison Security Considerations . . . . . . . . 27
11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 27
11.1. Normative References . . . . . . . . . . . . . . . . . . . 27
11.2. Informative References . . . . . . . . . . . . . . . . . . 29
Appendix A. JWS Examples . . . . . . . . . . . . . . . . . . . . 30
A.1. Example JWS using HMAC SHA-256 . . . . . . . . . . . . . . 30
A.1.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 30
A.1.2. Validating . . . . . . . . . . . . . . . . . . . . . . 32
A.2. Example JWS using RSASSA-PKCS-v1_5 SHA-256 . . . . . . . . 32
A.2.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 33
A.2.2. Validating . . . . . . . . . . . . . . . . . . . . . . 35
A.3. Example JWS using ECDSA P-256 SHA-256 . . . . . . . . . . 35
A.3.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 35
A.3.2. Validating . . . . . . . . . . . . . . . . . . . . . . 37
A.4. Example JWS using ECDSA P-521 SHA-512 . . . . . . . . . . 38
A.4.1. Encoding . . . . . . . . . . . . . . . . . . . . . . . 38
A.4.2. Validating . . . . . . . . . . . . . . . . . . . . . . 40
A.5. Example Plaintext JWS . . . . . . . . . . . . . . . . . . 40
A.6. Example JWS Using JWS JSON Serialization . . . . . . . . . 41
A.6.1. JWS Per-Signature Protected Headers . . . . . . . . . 41
A.6.2. JWS Per-Signature Unprotected Headers . . . . . . . . 42
A.6.3. Complete JOSE Header Values . . . . . . . . . . . . . 42
A.6.4. Complete JWS JSON Serialization Representation . . . . 42
Appendix B. "x5c" (X.509 Certificate Chain) Example . . . . . . . 43
Appendix C. Notes on implementing base64url encoding without
padding . . . . . . . . . . . . . . . . . . . . . . . 45
Appendix D. Notes on Key Selection . . . . . . . . . . . . . . . 46
Appendix E. Negative Test Case for "crit" Header Parameter . . . 47
Appendix F. Detached Content . . . . . . . . . . . . . . . . . . 48
Appendix G. Acknowledgements . . . . . . . . . . . . . . . . . . 48
Appendix H. Document History . . . . . . . . . . . . . . . . . . 49
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 58
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1. Introduction
JSON Web Signature (JWS) represents content secured with digital
signatures or Message Authentication Codes (MACs) using JavaScript
Object Notation (JSON) [RFC7159] based data structures. The JWS
cryptographic mechanisms provide integrity protection for an
arbitrary sequence of octets.
Two closely related serializations for JWS objects are defined. The
JWS Compact Serialization is a compact, URL-safe representation
intended for space constrained environments such as HTTP
Authorization headers and URI query parameters. The JWS JSON
Serialization represents JWS objects as JSON objects and enables
multiple signatures and/or MACs to be applied to the same content.
Both share the same cryptographic underpinnings.
Cryptographic algorithms and identifiers for use with this
specification are described in the separate JSON Web Algorithms (JWA)
[JWA] specification and an IANA registry defined by that
specification. Related encryption capabilities are described in the
separate JSON Web Encryption (JWE) [JWE] specification.
Names defined by this specification are short because a core goal is
for the resulting representations to be compact.
1.1. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in Key
words for use in RFCs to Indicate Requirement Levels [RFC2119]. If
these words are used without being spelled in uppercase then they are
to be interpreted with their normal natural language meanings.
BASE64URL(OCTETS) denotes the base64url encoding of OCTETS, per
Section 2.
UTF8(STRING) denotes the octets of the UTF-8 [RFC3629] representation
of STRING.
ASCII(STRING) denotes the octets of the ASCII [USASCII]
representation of STRING.
The concatenation of two values A and B is denoted as A || B.
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2. Terminology
These terms are defined by this specification:
JSON Web Signature (JWS)
A data structure representing a digitally signed or MACed message.
JOSE Header
JSON object containing the parameters describing the cryptographic
operations and parameters employed. The members of the JOSE
Header are Header Parameters.
JWS Payload
The sequence of octets to be secured -- a.k.a., the message. The
payload can contain an arbitrary sequence of octets.
JWS Signature
Digital signature or MAC over the JWS Protected Header and the JWS
Payload.
Header Parameter
A name/value pair that is member of the JOSE Header.
JWS Protected Header
JSON object that contains the Header Parameters that are integrity
protected by the JWS Signature digital signature or MAC operation.
For the JWS Compact Serialization, this comprises the entire JOSE
Header. For the JWS JSON Serialization, this is one component of
the JOSE Header.
JWS Unprotected Header
JSON object that contains the Header Parameters that are not
integrity protected. This can only be present when using the JWS
JSON Serialization.
Base64url Encoding
Base64 encoding using the URL- and filename-safe character set
defined in Section 5 of RFC 4648 [RFC4648], with all trailing '='
characters omitted (as permitted by Section 3.2) and without the
inclusion of any line breaks, white space, or other additional
characters. (See Appendix C for notes on implementing base64url
encoding without padding.)
JWS Signing Input
The input to the digital signature or MAC computation. Its value
is ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' ||
BASE64URL(JWS Payload)).
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JWS Compact Serialization
A representation of the JWS as a compact, URL-safe string.
JWS JSON Serialization
A representation of the JWS as a JSON object. Unlike the JWS
Compact Serialization, the JWS JSON Serialization enables multiple
digital signatures and/or MACs to be applied to the same content.
This representation is neither optimized for compactness nor URL-
safe.
Plaintext JWS
A JWS object that provides no integrity protection.
Collision-Resistant Name
A name in a namespace that enables names to be allocated in a
manner such that they are highly unlikely to collide with other
names. Examples of collision-resistant namespaces include: Domain
Names, Object Identifiers (OIDs) as defined in the ITU-T X.660 and
X.670 Recommendation series, and Universally Unique IDentifiers
(UUIDs) [RFC4122]. When using an administratively delegated
namespace, the definer of a name needs to take reasonable
precautions to ensure they are in control of the portion of the
namespace they use to define the name.
StringOrURI
A JSON string value, with the additional requirement that while
arbitrary string values MAY be used, any value containing a ":"
character MUST be a URI [RFC3986]. StringOrURI values are
compared as case-sensitive strings with no transformations or
canonicalizations applied.
These terms defined by the JSON Web Encryption (JWE) [JWE]
specification are incorporated into this specification: "JSON Web
Encryption (JWE)" and "JWE Compact Serialization".
3. JSON Web Signature (JWS) Overview
JWS represents digitally signed or MACed content using JSON data
structures and base64url encoding. A JWS represents these logical
values:
JOSE Header
JSON object containing the parameters describing the cryptographic
operations and parameters employed. For a JWS object, the JOSE
Header members are the union of the members of the JWS Protected
Header and the JWS Unprotected Header, as described below.
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JWS Payload
The sequence of octets to be secured -- a.k.a., the message. The
payload can contain an arbitrary sequence of octets.
JWS Signature
Digital signature or MAC over the JWS Protected Header and the JWS
Payload.
For a JWS object, the JOSE Header represents the combination of these
values:
JWS Protected Header
JSON object that contains the Header Parameters that are integrity
protected by the JWS Signature digital signature or MAC operation.
JWS Unprotected Header
JSON object that contains the Header Parameters that are not
integrity protected.
This document defines two serializations for JWS objects: a compact,
URL-safe serialization called the JWS Compact Serialization and a
JSON serialization called the JWS JSON Serialization. In both
serializations, the JWS Protected Header, JWS Payload, and JWS
Signature are base64url encoded for transmission, since JSON lacks a
way to directly represent octet sequences.
3.1. JWS Compact Serialization Overview
In the JWS Compact Serialization, no JWS Unprotected Header is used.
In this case, the JOSE Header and the JWS Protected Header are the
same.
In the JWS Compact Serialization, a JWS object is represented as the
combination of these three string values,
BASE64URL(UTF8(JWS Protected Header)),
BASE64URL(JWS Payload), and
BASE64URL(JWS Signature),
concatenated in that order, with the three strings being separated by
two period ('.') characters.
3.2. JWS JSON Serialization Overview
In the JWS JSON Serialization, one or both of the JWS Protected
Header and JWS Unprotected Header MUST be present. In this case, the
members of the JOSE Header are the combination of the members of the
JWS Protected Header and the JWS Unprotected Header values that are
present.
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In the JWS JSON Serialization, a JWS object is represented as the
combination of these four values,
BASE64URL(UTF8(JWS Protected Header)),
JWS Unprotected Header,
BASE64URL(JWS Payload), and
BASE64URL(JWS Signature),
with the three base64url encoding result strings and the JWS
Unprotected Header value being represented as members within a JSON
object. The inclusion of some of these values is OPTIONAL. The JWS
JSON Serialization can also represent multiple signature and/or MAC
values, rather than just one. See Section 7.2 for more information
about the JWS JSON Serialization.
3.3. Example JWS
This section provides an example of a JWS. Its computation is
described in more detail in Appendix A.1, including specifying the
exact octet sequences representing the JSON values used and the key
value used.
The following example JWS Protected Header declares that the encoded
object is a JSON Web Token (JWT) [JWT] and the JWS Protected Header
and the JWS Payload are secured using the HMAC SHA-256 [RFC2104, SHS]
algorithm:
{"typ":"JWT",
"alg":"HS256"}
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
The UTF-8 representation of following JSON object is used as the JWS
Payload. (Note that the payload can be any content, and need not be
a representation of a JSON object.)
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Encoding this JWS Payload as BASE64URL(JWS Payload) gives this value
(with line breaks for display purposes only):
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
Computing the HMAC of the JWS Signing Input ASCII(BASE64URL(UTF8(JWS
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Protected Header)) || '.' || BASE64URL(JWS Payload)) with the HMAC
SHA-256 algorithm using the key specified in Appendix A.1 and
base64url encoding the result yields this BASE64URL(JWS Signature)
value:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Concatenating these values in the order Header.Payload.Signature with
period ('.') characters between the parts yields this complete JWS
representation using the JWS Compact Serialization (with line breaks
for display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
See Appendix A for additional examples.
4. JOSE Header
For a JWS object, the members of the JSON object(s) representing the
JOSE Header describe the digital signature or MAC applied to the JWS
Protected Header and the JWS Payload and optionally additional
properties of the JWS. The Header Parameter names within the JOSE
Header MUST be unique; recipients MUST either reject JWSs with
duplicate Header Parameter names or use a JSON parser that returns
only the lexically last duplicate member name, as specified in
Section 15.12 (The JSON Object) of ECMAScript 5.1 [ECMAScript].
Implementations are required to understand the specific Header
Parameters defined by this specification that are designated as "MUST
be understood" and process them in the manner defined in this
specification. All other Header Parameters defined by this
specification that are not so designated MUST be ignored when not
understood. Unless listed as a critical Header Parameter, per
Section 4.1.11, all Header Parameters not defined by this
specification MUST be ignored when not understood.
There are three classes of Header Parameter names: Registered Header
Parameter names, Public Header Parameter names, and Private Header
Parameter names.
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4.1. Registered Header Parameter Names
The following Header Parameter names for use in JWS objects are
registered in the IANA JSON Web Signature and Encryption Header
Parameters registry defined in Section 9.1, with meanings as defined
below.
As indicated by the common registry, JWSs and JWEs share a common
Header Parameter space; when a parameter is used by both
specifications, its usage must be compatible between the
specifications.
4.1.1. "alg" (Algorithm) Header Parameter
The "alg" (algorithm) Header Parameter identifies the cryptographic
algorithm used to secure the JWS. The signature, MAC, or plaintext
value is not valid if the "alg" value does not represent a supported
algorithm, or if there is not a key for use with that algorithm
associated with the party that digitally signed or MACed the content.
"alg" values should either be registered in the IANA JSON Web
Signature and Encryption Algorithms registry defined in [JWA] or be a
value that contains a Collision-Resistant Name. The "alg" value is a
case-sensitive string containing a StringOrURI value. This Header
Parameter MUST be present and MUST be understood and processed by
implementations.
A list of defined "alg" values for this use can be found in the IANA
JSON Web Signature and Encryption Algorithms registry defined in
[JWA]; the initial contents of this registry are the values defined
in Section 3.1 of the JSON Web Algorithms (JWA) [JWA] specification.
4.1.2. "jku" (JWK Set URL) Header Parameter
The "jku" (JWK Set URL) Header Parameter is a URI [RFC3986] that
refers to a resource for a set of JSON-encoded public keys, one of
which corresponds to the key used to digitally sign the JWS. The
keys MUST be encoded as a JSON Web Key Set (JWK Set) [JWK]. The
protocol used to acquire the resource MUST provide integrity
protection; an HTTP GET request to retrieve the JWK Set MUST use TLS
[RFC2818, RFC5246]; the identity of the server MUST be validated, as
per Section 6 of RFC 6125 [RFC6125]. Use of this Header Parameter is
OPTIONAL.
4.1.3. "jwk" (JSON Web Key) Header Parameter
The "jwk" (JSON Web Key) Header Parameter is the public key that
corresponds to the key used to digitally sign the JWS. This key is
represented as a JSON Web Key [JWK]. Use of this Header Parameter is
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OPTIONAL.
4.1.4. "kid" (Key ID) Header Parameter
The "kid" (key ID) Header Parameter is a hint indicating which key
was used to secure the JWS. This parameter allows originators to
explicitly signal a change of key to recipients. The structure of
the "kid" value is unspecified. Its value MUST be a string. Use of
this Header Parameter is OPTIONAL.
When used with a JWK, the "kid" value is used to match a JWK "kid"
parameter value.
4.1.5. "x5u" (X.509 URL) Header Parameter
The "x5u" (X.509 URL) Header Parameter is a URI [RFC3986] that refers
to a resource for the X.509 public key certificate or certificate
chain [RFC5280] corresponding to the key used to digitally sign the
JWS. The identified resource MUST provide a representation of the
certificate or certificate chain that conforms to RFC 5280 [RFC5280]
in PEM encoded form [RFC1421]. The certificate containing the public
key corresponding to the key used to digitally sign the JWS MUST be
the first certificate. This MAY be followed by additional
certificates, with each subsequent certificate being the one used to
certify the previous one. The protocol used to acquire the resource
MUST provide integrity protection; an HTTP GET request to retrieve
the certificate MUST use TLS [RFC2818, RFC5246]; the identity of the
server MUST be validated, as per Section 6 of RFC 6125 [RFC6125].
Use of this Header Parameter is OPTIONAL.
4.1.6. "x5c" (X.509 Certificate Chain) Header Parameter
The "x5c" (X.509 Certificate Chain) Header Parameter contains the
X.509 public key certificate or certificate chain [RFC5280]
corresponding to the key used to digitally sign the JWS. The
certificate or certificate chain is represented as a JSON array of
certificate value strings. Each string in the array is a base64
encoded ([RFC4648] Section 4 -- not base64url encoded) DER
[ITU.X690.1994] PKIX certificate value. The certificate containing
the public key corresponding to the key used to digitally sign the
JWS MUST be the first certificate. This MAY be followed by
additional certificates, with each subsequent certificate being the
one used to certify the previous one. The recipient MUST validate
the certificate chain according to RFC 5280 [RFC5280] and reject the
signature if any validation failure occurs. Use of this Header
Parameter is OPTIONAL.
See Appendix B for an example "x5c" value.
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4.1.7. "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter
The "x5t" (X.509 Certificate SHA-1 Thumbprint) Header Parameter is a
base64url encoded SHA-1 thumbprint (a.k.a. digest) of the DER
encoding of the X.509 certificate [RFC5280] corresponding to the key
used to digitally sign the JWS. Use of this Header Parameter is
OPTIONAL.
4.1.8. "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header
Parameter
The "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) Header
Parameter is a base64url encoded SHA-256 thumbprint (a.k.a. digest)
of the DER encoding of the X.509 certificate [RFC5280] corresponding
to the key used to digitally sign the JWS. Use of this Header
Parameter is OPTIONAL.
4.1.9. "typ" (Type) Header Parameter
The "typ" (type) Header Parameter is used by JWS applications to
declare the MIME Media Type [IANA.MediaTypes] of this complete JWS
object. This is intended for use by the application when more than
one kind of object could be present in an application data structure
that can contain a JWS object; the application can use this value to
disambiguate among the different kinds of objects that might be
present. It will typically not be used by applications when the kind
of object is already known. This parameter is ignored by JWS
implementations; any processing of this parameter is performed by the
JWS application. Use of this Header Parameter is OPTIONAL.
Per RFC 2045 [RFC2045], all media type values, subtype values, and
parameter names are case-insensitive. However, parameter values are
case-sensitive unless otherwise specified for the specific parameter.
To keep messages compact in common situations, it is RECOMMENDED that
senders omit an "application/" prefix of a media type value in a
"typ" Header Parameter when no other '/' appears in the media type
value. A recipient using the media type value MUST treat it as if
"application/" were prepended to any "typ" value not containing a
'/'. For instance, a "typ" value of "example" SHOULD be used to
represent the "application/example" media type; whereas, the media
type "application/example;part="1/2"" cannot be shortened to
"example;part="1/2"".
The "typ" value "JOSE" can be used by applications to indicate that
this object is a JWS or JWE using the JWS Compact Serialization or
the JWE Compact Serialization. The "typ" value "JOSE+JSON" can be
used by applications to indicate that this object is a JWS or JWE
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using the JWS JSON Serialization or the JWE JSON Serialization.
Other type values can also be used by applications.
4.1.10. "cty" (Content Type) Header Parameter
The "cty" (content type) Header Parameter is used by JWS applications
to declare the MIME Media Type [IANA.MediaTypes] of the secured
content (the payload). This is intended for use by the application
when more than one kind of object could be present in the JWS
payload; the application can use this value to disambiguate among the
different kinds of objects that might be present. It will typically
not be used by applications when the kind of object is already known.
This parameter is ignored by JWS implementations; any processing of
this parameter is performed by the JWS application. Use of this
Header Parameter is OPTIONAL.
Per RFC 2045 [RFC2045], all media type values, subtype values, and
parameter names are case-insensitive. However, parameter values are
case-sensitive unless otherwise specified for the specific parameter.
To keep messages compact in common situations, it is RECOMMENDED that
senders omit an "application/" prefix of a media type value in a
"cty" Header Parameter when no other '/' appears in the media type
value. A recipient using the media type value MUST treat it as if
"application/" were prepended to any "cty" value not containing a
'/'. For instance, a "cty" value of "example" SHOULD be used to
represent the "application/example" media type; whereas, the media
type "application/example;part="1/2"" cannot be shortened to
"example;part="1/2"".
4.1.11. "crit" (Critical) Header Parameter
The "crit" (critical) Header Parameter indicates that extensions to
the initial RFC versions of [[ this specification ]] and [JWA] are
being used that MUST be understood and processed. Its value is an
array listing the Header Parameter names present in the JOSE Header
that use those extensions. If any of the listed extension Header
Parameters are not understood and supported by the receiver, it MUST
reject the JWS. Senders MUST NOT include Header Parameter names
defined by the initial RFC versions of [[ this specification ]] or
[JWA] for use with JWS, duplicate names, or names that do not occur
as Header Parameter names within the JOSE Header in the "crit" list.
Senders MUST NOT use the empty list "[]" as the "crit" value.
Recipients MAY reject the JWS if the critical list contains any
Header Parameter names defined by the initial RFC versions of [[ this
specification ]] or [JWA] for use with JWS, or any other constraints
on its use are violated. This Header Parameter MUST be integrity
protected, and therefore MUST occur only within the JWS Protected
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Header, when used. Use of this Header Parameter is OPTIONAL. This
Header Parameter MUST be understood and processed by implementations.
An example use, along with a hypothetical "exp" (expiration-time)
field is:
{"alg":"ES256",
"crit":["exp"],
"exp":1363284000
}
4.2. Public Header Parameter Names
Additional Header Parameter names can be defined by those using JWSs.
However, in order to prevent collisions, any new Header Parameter
name should either be registered in the IANA JSON Web Signature and
Encryption Header Parameters registry defined in Section 9.1 or be a
Public Name: a value that contains a Collision-Resistant Name. 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 Header Parameter name.
New Header Parameters should be introduced sparingly, as they can
result in non-interoperable JWSs.
4.3. Private Header Parameter Names
A producer and consumer of a JWS may agree to use Header Parameter
names that are Private Names: names that are not Registered Header
Parameter names Section 4.1 or Public Header Parameter names
Section 4.2. Unlike Public Header Parameter names, Private Header
Parameter names are subject to collision and should be used with
caution.
5. Producing and Consuming JWSs
5.1. Message Signature or MAC Computation
To create a JWS, one MUST perform these steps. The order of the
steps is not significant in cases where there are no dependencies
between the inputs and outputs of the steps.
1. Create the content to be used as the JWS Payload.
2. Compute the encoded payload value BASE64URL(JWS Payload).
3. Create the JSON object(s) containing the desired set of Header
Parameters, which together comprise the JOSE Header: the JWS
Protected Header, and if the JWS JSON Serialization is being
used, the JWS Unprotected Header.
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4. Compute the encoded header value BASE64URL(UTF8(JWS Protected
Header)). If the JWS Protected Header is not present (which can
only happen when using the JWS JSON Serialization and no
"protected" member is present), let this value be the empty
string.
5. Compute the JWS Signature in the manner defined for the
particular algorithm being used over the JWS Signing Input
ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.' ||
BASE64URL(JWS Payload)). The "alg" (algorithm) Header Parameter
MUST be present in the JOSE Header, with the algorithm value
accurately representing the algorithm used to construct the JWS
Signature.
6. Compute the encoded signature value BASE64URL(JWS Signature).
7. These three encoded values are used in both the JWS Compact
Serialization and the JWS JSON Serialization representations.
8. If the JWS JSON Serialization is being used, repeat this process
(steps 3-7) for each digital signature or MAC operation being
performed.
9. Create the desired serialized output. The JWS Compact
Serialization of this result is BASE64URL(UTF8(JWS Protected
Header)) || '.' || BASE64URL(JWS Payload) || '.' || BASE64URL(JWS
Signature). The JWS JSON Serialization is described in
Section 7.2.
5.2. Message Signature or MAC Validation
When validating a JWS, the following steps MUST be taken. The order
of the steps is not significant in cases where there are no
dependencies between the inputs and outputs of the steps. If any of
the listed steps fails, then the signature or MAC cannot be
validated.
It is an application decision which signatures, MACs, or plaintext
values must successfully validate for the JWS to be accepted. In
some cases, all must successfully validate or the JWS will be
rejected. In other cases, only a specific signature, MAC, or
plaintext value needs to be successfully validated. However, in all
cases, at least one signature, MAC, or plaintext value MUST
successfully validate or the JWS MUST be rejected.
1. Parse the JWS representation to extract the serialized values
for the components of the JWS. When using the JWS Compact
Serialization, these components are the base64url encoded
representations of the JWS Protected Header, the JWS Payload,
and the JWS Signature, and when using the JWS JSON
Serialization, these components also include the unencoded JWS
Unprotected Header value. When using the JWS Compact
Serialization, the JWS Protected Header, the JWS Payload, and
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the JWS Signature are represented as base64url encoded values in
that order, separated by two period ('.') characters. The JWS
JSON Serialization is described in Section 7.2.
2. The encoded representation of the JWS Protected Header MUST be
successfully base64url decoded following the restriction that no
padding characters have been used.
3. The resulting octet sequence MUST be a UTF-8 encoded
representation of a completely valid JSON object conforming to
RFC 7159 [RFC7159], which is the JWS Protected Header.
4. If using the JWS Compact Serialization, let the JOSE Header be
the JWS Protected Header. Otherwise, when using the JWS JSON
Serialization, let the JOSE Header be the union of the members
of the corresponding JWS Protected Header and JWS Unprotected
Header, all of which must be completely valid JSON objects.
5. The resulting JOSE Header MUST NOT contain duplicate Header
Parameter names. When using the JWS JSON Serialization, this
restriction includes that the same Header Parameter name also
MUST NOT occur in distinct JSON object values that together
comprise the JOSE Header.
6. Verify that the implementation understands and can process all
fields that it is required to support, whether required by this
specification, by the algorithm being used, or by the "crit"
Header Parameter value, and that the values of those parameters
are also understood and supported.
7. The encoded representation of the JWS Payload MUST be
successfully base64url decoded following the restriction that no
padding characters have been used.
8. The encoded representation of the JWS Signature MUST be
successfully base64url decoded following the restriction that no
padding characters have been used.
9. The JWS Signature MUST be successfully validated against the JWS
Signing Input ASCII(BASE64URL(UTF8(JWS Protected Header)) || '.'
|| BASE64URL(JWS Payload)) in the manner defined for the
algorithm being used, which MUST be accurately represented by
the value of the "alg" (algorithm) Header Parameter, which MUST
be present.
10. If the JWS JSON Serialization is being used, repeat this process
(steps 4-9) for each digital signature or MAC value contained in
the representation.
5.3. String Comparison Rules
Processing a JWS inevitably requires comparing known strings to
members and values in a JSON object. For example, in checking what
the algorithm is, the Unicode string "alg" will be checked against
the member names in the JOSE Header to see if there is a matching
Header Parameter name. The same process is then used to determine if
the value of the "alg" Header Parameter represents a supported
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algorithm.
Since the only string comparison operations that are performed are
equality and inequality, the same rules can be used for comparing
both member names and member values against known strings. The JSON
rules for doing member name comparison are described in Section 8.3
of RFC 7159 [RFC7159].
Also, see the JSON security considerations in Section 10.6 and the
Unicode security considerations in Section 10.7.
6. Key Identification
It is necessary for the recipient of a JWS to be able to determine
the key that was employed for the digital signature or MAC operation.
The key employed can be identified using the Header Parameter methods
described in Section 4.1 or can be identified using methods that are
outside the scope of this specification. Specifically, the Header
Parameters "jku", "jwk", "kid", "x5u", "x5c", "x5t", and "x5t#S256"
can be used to identify the key used. These Header Parameters MUST
be integrity protected if the information that they convey is to be
utilized in a trust decision.
The sender SHOULD include sufficient information in the Header
Parameters to identify the key used, unless the application uses
another means or convention to determine the key used. Validation of
the signature or MAC fails when the algorithm used requires a key
(which is true of all algorithms except for "none") and the key used
cannot be determined.
The means of exchanging any shared symmetric keys used is outside the
scope of this specification.
Also, see Appendix D for notes on possible key selection algorithms.
7. Serializations
JWS objects use one of two serializations, the JWS Compact
Serialization or the JWS JSON Serialization. Applications using this
specification need to specify what serialization and serialization
features are used for that application. For instance, applications
might specify that only the JWS JSON Serialization is used, that only
JWS JSON Serialization support for a single signature or MAC value is
used, or that support for multiple signatures and/or MAC values is
used. JWS implementations only need to implement the features needed
for the applications they are designed to support.
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7.1. JWS Compact Serialization
The JWS Compact Serialization represents digitally signed or MACed
content as a compact URL-safe string. This string is
BASE64URL(UTF8(JWS Protected Header)) || '.' || BASE64URL(JWS
Payload) || '.' || BASE64URL(JWS Signature). Only one signature/MAC
is supported by the JWS Compact Serialization and it provides no
syntax to represent a JWS Unprotected Header value.
7.2. JWS JSON Serialization
The JWS JSON Serialization represents digitally signed or MACed
content as a JSON object. Content using the JWS JSON Serialization
can be secured with more than one digital signature and/or MAC
operation. This representation is neither optimized for compactness
nor URL-safe.
The following members are defined for use in top-level JSON objects
used for the JWS JSON Serialization:
payload
The "payload" member MUST be present and contain the value
BASE64URL(JWS Payload).
signatures
The "signatures" member value MUST be an array of JSON objects.
Each object represents a signature or MAC over the JWS Payload and
the JWS Protected Header.
The following members are defined for use in the JSON objects that
are elements of the "signatures" array:
protected
The "protected" member MUST be present and contain the value
BASE64URL(UTF8(JWS Protected Header)) when the JWS Protected
Header value is non-empty; otherwise, it MUST be absent. These
Header Parameter values are integrity protected.
header
The "header" member MUST be present and contain the value JWS
Unprotected Header when the JWS Unprotected Header value is non-
empty; otherwise, it MUST be absent. This value is represented as
an unencoded JSON object, rather than as a string. These Header
Parameter values are not integrity protected.
signature
The "signature" member MUST be present and contain the value
BASE64URL(JWS Signature).
At least one of the "protected" and "header" members MUST be present
for each signature/MAC computation so that an "alg" Header Parameter
value is conveyed.
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Additional members can be present in both the JSON objects defined
above; if not understood by implementations encountering them, they
MUST be ignored.
The Header Parameter values used when creating or validating
individual signature or MAC values are the union of the two sets of
Header Parameter values that may be present: (1) the JWS Protected
Header represented in the "protected" member of the signature/MAC's
array element, and (2) the JWS Unprotected Header in the "header"
member of the signature/MAC's array element. The union of these sets
of Header Parameters comprises the JOSE Header. The Header Parameter
names in the two locations MUST be disjoint.
Each JWS Signature value is computed using the parameters of the
corresponding JOSE Header value in the same manner as for the JWS
Compact Serialization. This has the desirable property that each JWS
Signature value represented in the "signatures" array is identical to
the value that would have been computed for the same parameter in the
JWS Compact Serialization, provided that the JWS Protected Header
value for that signature/MAC computation (which represents the
integrity-protected Header Parameter values) matches that used in the
JWS Compact Serialization.
In summary, the syntax of a JWS using the JWS JSON Serialization is
as follows:
{
"payload":"<payload contents>",
"signatures":[
{"protected":"<integrity-protected header 1 contents>",
"header":<non-integrity-protected header 1 contents>,
"signature":"<signature 1 contents>"},
...
{"protected":"<integrity-protected header N contents>",
"header":<non-integrity-protected header N contents>,
"signature":"<signature N contents>"}]
}
See Appendix A.6 for an example of computing a JWS using the JWS JSON
Serialization.
8. TLS Requirements
Implementations MUST support TLS. Which version(s) ought to be
implemented will vary over time, and depend on the widespread
deployment and known security vulnerabilities at the time of
implementation. At the time of this writing, TLS version 1.2
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[RFC5246] is the most recent version.
To protect against information disclosure and tampering,
confidentiality protection MUST be applied using TLS with a
ciphersuite that provides confidentiality and integrity protection.
See current publications by the IETF TLS working group, including RFC
6176 [RFC6176], for guidance on the ciphersuites currently considered
to be appropriate for use.
Whenever TLS is used, the identity of the service provider encoded in
the TLS server certificate MUST be verified using the procedures
described in Section 6 of RFC 6125 [RFC6125].
9. IANA Considerations
The following registration procedure is used for all the registries
established by this specification.
Values are registered on a Specification Required [RFC5226] basis
after a two-week review period on the [TBD]@ietf.org mailing list, on
the advice of one or more Designated Experts. However, to allow for
the allocation of values prior to publication, the Designated
Expert(s) may approve registration once they are satisfied that such
a specification will be published.
Registration requests must be sent to the [TBD]@ietf.org mailing list
for review and comment, with an appropriate subject (e.g., "Request
for access token type: example"). [[ Note to the RFC Editor: The name
of the mailing list should be determined in consultation with the
IESG and IANA. Suggested name: jose-reg-review. ]]
Within the review period, the Designated Expert(s) will either
approve or deny the registration request, communicating this decision
to the review list and IANA. Denials should include an explanation
and, if applicable, suggestions as to how to make the request
successful. Registration requests that are undetermined for a period
longer than 21 days can be brought to the IESG's attention (using the
iesg@iesg.org mailing list) for resolution.
Criteria that should be applied by the Designated Expert(s) includes
determining whether the proposed registration duplicates existing
functionality, determining whether it is likely to be of general
applicability or whether it is useful only for a single application,
and whether the registration makes sense.
IANA must only accept registry updates from the Designated Expert(s)
and should direct all requests for registration to the review mailing
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list.
It is suggested that multiple Designated Experts be appointed who are
able to represent the perspectives of different applications using
this specification, in order to enable broadly-informed review of
registration decisions. In cases where a registration decision could
be perceived as creating a conflict of interest for a particular
Expert, that Expert should defer to the judgment of the other
Expert(s).
9.1. JSON Web Signature and Encryption Header Parameters Registry
This specification establishes the IANA JSON Web Signature and
Encryption Header Parameters registry for Header Parameter names.
The registry records the Header Parameter name and a reference to the
specification that defines it. The same Header Parameter name can be
registered multiple times, provided that the parameter usage is
compatible between the specifications. Different registrations of
the same Header Parameter name will typically use different Header
Parameter Usage Location(s) values.
9.1.1. Registration Template
Header Parameter Name:
The name requested (e.g., "example"). Because a core goal of this
specification is for the resulting representations to be compact,
it is RECOMMENDED that the name be short -- not to exceed 8
characters without a compelling reason to do so. This name is
case-sensitive. Names may not match other registered names in a
case-insensitive manner unless the Designated Expert(s) state that
there is a compelling reason to allow an exception in this
particular case.
Header Parameter Description:
Brief description of the Header Parameter (e.g., "Example
description").
Header Parameter Usage Location(s):
The Header Parameter usage locations, which should be one or more
of the values "JWS" or "JWE".
Change Controller:
For Standards Track RFCs, state "IESG". For others, give the name
of the responsible party. Other details (e.g., postal address,
email address, home page URI) may also be included.
Specification Document(s):
Reference to the document(s) that specify the parameter,
preferably including URI(s) that can be used to retrieve copies of
the document(s). An indication of the relevant sections may also
be included but is not required.
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9.1.2. Initial Registry Contents
This specification registers the Header Parameter names defined in
Section 4.1 in this registry.
o Header Parameter Name: "alg"
o Header Parameter Description: Algorithm
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.1 of [[ this document ]]
o Header Parameter Name: "jku"
o Header Parameter Description: JWK Set URL
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.2 of [[ this document ]]
o Header Parameter Name: "jwk"
o Header Parameter Description: JSON Web Key
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification document(s): Section 4.1.3 of [[ this document ]]
o Header Parameter Name: "kid"
o Header Parameter Description: Key ID
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.4 of [[ this document ]]
o Header Parameter Name: "x5u"
o Header Parameter Description: X.509 URL
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.5 of [[ this document ]]
o Header Parameter Name: "x5c"
o Header Parameter Description: X.509 Certificate Chain
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.6 of [[ this document ]]
o Header Parameter Name: "x5t"
o Header Parameter Description: X.509 Certificate SHA-1 Thumbprint
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.7 of [[ this document ]]
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o Header Parameter Name: "x5t#S256"
o Header Parameter Description: X.509 Certificate SHA-256 Thumbprint
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.8 of [[ this document ]]
o Header Parameter Name: "typ"
o Header Parameter Description: Type
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.9 of [[ this document ]]
o Header Parameter Name: "cty"
o Header Parameter Description: Content Type
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.10 of [[ this document ]]
o Header Parameter Name: "crit"
o Header Parameter Description: Critical
o Header Parameter Usage Location(s): JWS
o Change Controller: IESG
o Specification Document(s): Section 4.1.11 of [[ this document ]]
9.2. Media Type Registration
9.2.1. Registry Contents
This specification registers the "application/jose" Media Type
[RFC2046] in the MIME Media Types registry [IANA.MediaTypes], which
can be used to indicate that the content is a JWS or JWE object using
the JWS Compact Serialization or the JWE Compact Serialization and
the "application/jose+json" Media Type in the MIME Media Types
registry, which can be used to indicate that the content is a JWS or
JWE object using the JWS JSON Serialization or the JWE JSON
Serialization.
o Type name: application
o Subtype name: jose
o Required parameters: n/a
o Optional parameters: n/a
o Encoding considerations: 8bit; application/jose values are encoded
as a series of base64url encoded values (some of which may be the
empty string) separated by period ('.') characters.
o Security considerations: See the Security Considerations section
of [[ this document ]]
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o Interoperability considerations: n/a
o Published specification: [[ this document ]]
o Applications that use this media type: OpenID Connect, Mozilla
Persona, Salesforce, Google, Android, Windows Azure, Xbox One, and
numerous others that use JWTs
o Additional information: Magic number(s): n/a, File extension(s):
n/a, Macintosh file type code(s): n/a
o Person & email address to contact for further information: Michael
B. Jones, mbj@microsoft.com
o Intended usage: COMMON
o Restrictions on usage: none
o Author: Michael B. Jones, mbj@microsoft.com
o Change Controller: IESG
o Type name: application
o Subtype name: jose+json
o Required parameters: n/a
o Optional parameters: n/a
o Encoding considerations: 8bit; application/jose+json values are
represented as a JSON Object; UTF-8 encoding SHOULD be employed
for the JSON object.
o Security considerations: See the Security Considerations section
of [[ this document ]]
o Interoperability considerations: n/a
o Published specification: [[ this document ]]
o Applications that use this media type: TBD
o Additional information: Magic number(s): n/a, File extension(s):
n/a, Macintosh file type code(s): n/a
o Person & email address to contact for further information: Michael
B. Jones, mbj@microsoft.com
o Intended usage: COMMON
o Restrictions on usage: none
o Author: Michael B. Jones, mbj@microsoft.com
o Change Controller: IESG
10. Security Considerations
All of the security issues that are pertinent to any cryptographic
application must be addressed by JWS/JWE/JWK agents. Among these
issues are protecting the user's asymmetric private and symmetric
secret keys, preventing various attacks, and helping avoid mistakes
such as inadvertently encrypting a message to the wrong recipient.
The entire list of security considerations is beyond the scope of
this document, but some significant considerations are listed here.
All the security considerations in XML DSIG 2.0
[W3C.NOTE-xmldsig-core2-20130411], also apply to this specification,
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other than those that are XML specific. Likewise, many of the best
practices documented in XML Signature Best Practices
[W3C.NOTE-xmldsig-bestpractices-20130411] also apply to this
specification, other than those that are XML specific.
10.1. Key Entropy
Keys are only as strong as the amount of entropy used to generate
them. A minimum of 128 bits of entropy should be used for all keys,
and depending upon the application context, more may be required. In
particular, it may be difficult to generate sufficiently random
values in some browsers and application environments.
10.2. Chosen Plaintext Attacks
Creators of JWSs should not allow third parties to insert arbitrary
content into the message without adding entropy not controlled by the
third party.
10.3. Timing Attacks
When cryptographic algorithms are implemented in such a way that
successful operations take a different amount of time than
unsuccessful operations, attackers may be able to use the time
difference to obtain information about the keys employed. Therefore,
such timing differences must be avoided.
10.4. Differences between Digital Signatures and MACs
While MACs and digital signatures can both be used for integrity
checking, there are some significant differences between the security
properties that each of them provides. These need to be taken into
consideration when designing protocols and selecting the algorithms
to be used in protocols.
Both signatures and MACs provide for integrity checking -- verifying
that the message has not been modified since the integrity value was
computed. However, MACs provide for origination identification only
under specific circumstances. It can normally be assumed that a
private key used for a signature is only in the hands of a single
entity (although perhaps a distributed entity, in the case of
replicated servers); however, a MAC key needs to be in the hands of
all the entities that use it for integrity computation and checking.
This means that origination can only be determined if a MAC key is
known only to two entities and the receiver knows that it did not
create the message. MAC validation cannot be used to prove
origination to a third party.
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10.5. SHA-1 Certificate Thumbprints
A SHA-1 hash is used when computing "x5t" (X.509 Certificate SHA-1
Thumbprint) values, for compatibility reasons. Should an effective
means of producing SHA-1 hash collisions be developed, and should an
attacker wish to interfere with the use of a known certificate on a
given system, this could be accomplished by creating another
certificate whose SHA-1 hash value is the same and adding it to the
certificate store used by the intended victim. A prerequisite to
this attack succeeding is the attacker having write access to the
intended victim's certificate store.
Alternatively, the "x5t#S256" (X.509 Certificate SHA-256 Thumbprint)
Header Parameter could be used instead of "x5t". However, at the
time of this writing, no development platform is known to support
SHA-256 certificate thumbprints.
10.6. JSON Security Considerations
Strict JSON [RFC7159] validation is a security requirement. If
malformed JSON is received, then the intent of the sender is
impossible to reliably discern. Ambiguous and potentially
exploitable situations could arise if the JSON parser used does not
reject malformed JSON syntax. In particular, any JSON inputs not
conforming to the JSON-text syntax defined in RFC 7159 input MUST be
rejected in their entirety.
Section 4 of the JSON Data Interchange Format specification [RFC7159]
states "The names within an object SHOULD be unique", whereas this
specification states that "Header Parameter names within this object
MUST be unique; recipients MUST either reject JWSs with duplicate
Header Parameter names or use a JSON parser that returns only the
lexically last duplicate member name, as specified in Section 15.12
(The JSON Object) of ECMAScript 5.1 [ECMAScript]". Thus, this
specification requires that the Section 4 "SHOULD" be treated as a
"MUST" by senders and that it be either treated as a "MUST" or in the
manner specified in ECMAScript 5.1 by receivers. Ambiguous and
potentially exploitable situations could arise if the JSON parser
used does not enforce the uniqueness of member names or returns an
unpredictable value for duplicate member names.
Some JSON parsers might not reject input that contains extra
significant characters after a valid input. For instance, the input
"{"tag":"value"}ABCD" contains a valid JSON-text object followed by
the extra characters "ABCD". Such input MUST be rejected in its
entirety.
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10.7. Unicode Comparison Security Considerations
Header Parameter names and algorithm names are Unicode strings. For
security reasons, the representations of these names must be compared
verbatim after performing any escape processing (as per Section 8.3
of RFC 7159 [RFC7159]). This means, for instance, that these JSON
strings must compare as being equal ("sig", "\u0073ig"), whereas
these must all compare as being not equal to the first set or to each
other ("SIG", "Sig", "si\u0047").
JSON strings can 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, JWS
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. References
11.1. Normative References
[ECMAScript]
Ecma International, "ECMAScript Language Specification,
5.1 Edition", ECMA 262, June 2011.
[IANA.MediaTypes]
Internet Assigned Numbers Authority (IANA), "MIME Media
Types", 2005.
[ITU.X690.1994]
International Telecommunications Union, "Information
Technology - ASN.1 encoding rules: Specification of Basic
Encoding Rules (BER), Canonical Encoding Rules (CER) and
Distinguished Encoding Rules (DER)", ITU-T Recommendation
X.690, 1994.
[JWA] Jones, M., "JSON Web Algorithms (JWA)",
draft-ietf-jose-json-web-algorithms (work in progress),
July 2014.
[JWK] Jones, M., "JSON Web Key (JWK)",
draft-ietf-jose-json-web-key (work in progress),
July 2014.
[RFC1421] Linn, J., "Privacy Enhancement for Internet Electronic
Jones, et al. Expires January 5, 2015 [Page 27]
Internet-Draft JSON Web Signature (JWS) July 2014
Mail: Part I: Message Encryption and Authentication
Procedures", RFC 1421, February 1993.
[RFC2045] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part One: Format of Internet Message
Bodies", RFC 2045, November 1996.
[RFC2046] Freed, N. and N. Borenstein, "Multipurpose Internet Mail
Extensions (MIME) Part Two: Media Types", RFC 2046,
November 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011.
[RFC6176] Turner, S. and T. Polk, "Prohibiting Secure Sockets Layer
(SSL) Version 2.0", RFC 6176, March 2011.
[RFC7159] Bray, T., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, March 2014.
[USASCII] American National Standards Institute, "Coded Character
Set -- 7-bit American Standard Code for Information
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Internet-Draft JSON Web Signature (JWS) July 2014
Interchange", ANSI X3.4, 1986.
11.2. Informative References
[CanvasApp]
Facebook, "Canvas Applications", 2010.
[JSS] Bradley, J. and N. Sakimura (editor), "JSON Simple Sign",
September 2010.
[JWE] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
draft-ietf-jose-json-web-encryption (work in progress),
July 2014.
[JWT] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", draft-ietf-oauth-json-web-token (work in
progress), July 2014.
[MagicSignatures]
Panzer (editor), J., Laurie, B., and D. Balfanz, "Magic
Signatures", January 2011.
[RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
Hashing for Message Authentication", RFC 2104,
February 1997.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
[SHS] National Institute of Standards and Technology, "Secure
Hash Standard (SHS)", FIPS PUB 180-3, October 2008.
[W3C.NOTE-xmldsig-bestpractices-20130411]
Hirsch, F. and P. Datta, "XML Signature Best Practices",
World Wide Web Consortium Note NOTE-xmldsig-bestpractices-
20130411, April 2013, <http://www.w3.org/TR/2013/
NOTE-xmldsig-bestpractices-20130411/>.
[W3C.NOTE-xmldsig-core2-20130411]
Eastlake, D., Reagle, J., Solo, D., Hirsch, F., Roessler,
T., Yiu, K., Datta, P., and S. Cantor, "XML Signature
Syntax and Processing Version 2.0", World Wide Web
Consortium Note NOTE-xmldsig-core2-20130411, April 2013,
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<http://www.w3.org/TR/2013/NOTE-xmldsig-core2-20130411/>.
Appendix A. JWS Examples
This section provides several examples of JWSs. While the first
three examples all represent JSON Web Tokens (JWTs) [JWT], the
payload can be any octet sequence, as shown in Appendix A.4.
A.1. Example JWS using HMAC SHA-256
A.1.1. Encoding
The following example JWS Protected Header declares that the data
structure is a JSON Web Token (JWT) [JWT] and the JWS Signing Input
is secured using the HMAC SHA-256 algorithm.
{"typ":"JWT",
"alg":"HS256"}
To remove potential ambiguities in the representation of the JSON
object above, the actual octet sequence representing UTF8(JWS
Protected Header) used in this example is also included below. (Note
that ambiguities can arise due to differing platform representations
of line breaks (CRLF versus LF), differing spacing at the beginning
and ends of lines, whether the last line has a terminating line break
or not, and other causes. In the representation used in this
example, the first line has no leading or trailing spaces, a CRLF
line break (13, 10) occurs between the first and second lines, the
second line has one leading space (32) and no trailing spaces, and
the last line does not have a terminating line break.) The octets
representing UTF8(JWS Protected Header) in this example (using JSON
array notation) are:
[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]
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
The JWS Payload used in this example is the octets of the UTF-8
representation of the JSON object below. (Note that the payload can
be any base64url encoded octet sequence, and need not be a base64url
encoded JSON object.)
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{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
The following octet sequence, which is the UTF-8 representation used
in this example for the JSON object above, is the JWS Payload:
[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]
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value (with line breaks for display purposes
only):
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
BASE64URL(JWS Payload) gives this string (with line breaks for
display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The resulting JWS Signing Input value, which is the ASCII
representation of above string, is the following octet sequence
(using JSON array notation):
[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]
HMACs are generated using keys. This example uses the symmetric key
represented in JSON Web Key [JWK] format below (with line breaks
within values for display purposes only):
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{"kty":"oct",
"k":"AyM1SysPpbyDfgZld3umj1qzKObwVMkoqQ-EstJQLr_T-1qS0gZH75
aKtMN3Yj0iPS4hcgUuTwjAzZr1Z9CAow"
}
Running the HMAC SHA-256 algorithm on the JWS Signing Input with this
key yields this JWS Signature octet sequence:
[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]
Encoding this JWS Signature as BASE64URL(JWS Signature) gives this
value:
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
Concatenating these values in the order Header.Payload.Signature with
period ('.') characters between the parts yields this complete JWS
representation using the JWS Compact Serialization (with line breaks
for display purposes only):
eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk
A.1.2. Validating
Since the "alg" Header Parameter is "HS256", we validate the HMAC
SHA-256 value contained in the JWS Signature.
To validate the HMAC value, we repeat the previous process of using
the correct key and the JWS Signing Input (which is the initial
substring of the JWS Compact Serialization representation up until
but not including the second period character) as input to the HMAC
SHA-256 function and then taking the output and determining if it
matches the JWS Signature (which is base64url decoded from the value
encoded in the JWS representation). If it matches exactly, the HMAC
has been validated.
A.2. Example JWS using RSASSA-PKCS-v1_5 SHA-256
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A.2.1. Encoding
The JWS Protected Header in this example is different from the
previous example 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 algorithm employed.) The JWS
Protected Header used is:
{"alg":"RS256"}
The octets representing UTF8(JWS Protected Header) in this example
(using JSON array notation) are:
[123, 34, 97, 108, 103, 34, 58, 34, 82, 83, 50, 53, 54, 34, 125]
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJhbGciOiJSUzI1NiJ9
The JWS Payload used in this example, which follows, is the same as
in the previous example. Since the BASE64URL(JWS Payload) value will
therefore be the same, its computation is not repeated here.
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
BASE64URL(JWS Payload) gives this string (with line breaks for
display purposes only):
eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The resulting JWS Signing Input value, which is the ASCII
representation of above string, is the following octet sequence:
[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,
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99, 110, 86, 108, 102, 81]
This example uses the RSA key represented in JSON Web Key [JWK]
format below (with line breaks within values for display purposes
only):
{"kty":"RSA",
"n":"ofgWCuLjybRlzo0tZWJjNiuSfb4p4fAkd_wWJcyQoTbji9k0l8W26mPddx
HmfHQp-Vaw-4qPCJrcS2mJPMEzP1Pt0Bm4d4QlL-yRT-SFd2lZS-pCgNMs
D1W_YpRPEwOWvG6b32690r2jZ47soMZo9wGzjb_7OMg0LOL-bSf63kpaSH
SXndS5z5rexMdbBYUsLA9e-KXBdQOS-UTo7WTBEMa2R2CapHg665xsmtdV
MTBQY4uDZlxvb3qCo5ZwKh9kG4LT6_I5IhlJH7aGhyxXFvUK-DWNmoudF8
NAco9_h9iaGNj8q2ethFkMLs91kzk2PAcDTW9gb54h4FRWyuXpoQ",
"e":"AQAB",
"d":"Eq5xpGnNCivDflJsRQBXHx1hdR1k6Ulwe2JZD50LpXyWPEAeP88vLNO97I
jlA7_GQ5sLKMgvfTeXZx9SE-7YwVol2NXOoAJe46sui395IW_GO-pWJ1O0
BkTGoVEn2bKVRUCgu-GjBVaYLU6f3l9kJfFNS3E0QbVdxzubSu3Mkqzjkn
439X0M_V51gfpRLI9JYanrC4D4qAdGcopV_0ZHHzQlBjudU2QvXt4ehNYT
CBr6XCLQUShb1juUO1ZdiYoFaFQT5Tw8bGUl_x_jTj3ccPDVZFD9pIuhLh
BOneufuBiB4cS98l2SR_RQyGWSeWjnczT0QU91p1DhOVRuOopznQ"
}
The RSA private key is then passed to the RSA signing function, which
also takes the hash type, SHA-256, and the JWS Signing Input as
inputs. The result of the digital signature is an octet sequence,
which represents a big endian integer. In this example, it is:
[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]
Encoding the signature as BASE64URL(JWS Signature) produces this
value (with line breaks for display purposes only):
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cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7
AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4
BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K
0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv
hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB
p0igcN_IoypGlUPQGe77Rw
Concatenating these values in the order Header.Payload.Signature with
period ('.') characters between the parts yields this complete JWS
representation using the JWS Compact Serialization (with line breaks
for display purposes only):
eyJhbGciOiJSUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZmh7
AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjbKBYNX4
BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHlb1L07Qe7K
0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZESc6BfI7noOPqv
hJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AXLIhWkWywlVmtVrB
p0igcN_IoypGlUPQGe77Rw
A.2.2. Validating
Since the "alg" Header Parameter is "RS256", we validate the RSASSA-
PKCS-v1_5 SHA-256 digital signature contained in the JWS Signature.
Validating the JWS Signature is a bit different from the previous
example. We pass the public key (n, e), the JWS Signature (which is
base64url decoded from the value encoded in the JWS representation),
and the JWS Signing Input (which is the initial substring of the JWS
Compact Serialization representation up until but not including the
second period character) to an RSASSA-PKCS-v1_5 signature verifier
that has been configured to use the SHA-256 hash function.
A.3. Example JWS using ECDSA P-256 SHA-256
A.3.1. Encoding
The JWS Protected Header for this example differs from the previous
example because a different algorithm is being used. The JWS
Protected Header used is:
{"alg":"ES256"}
The octets representing UTF8(JWS Protected Header) in this example
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(using JSON array notation) are:
[123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 50, 53, 54, 34, 125]
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJhbGciOiJFUzI1NiJ9
The JWS Payload used in this example, which follows, is the same as
in the previous examples. Since the BASE64URL(JWS Payload) value
will therefore be the same, its computation is not repeated here.
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
BASE64URL(JWS Payload) gives this string (with line breaks for
display purposes only):
eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
The resulting JWS Signing Input value, which is the ASCII
representation of above string, is the following octet sequence:
[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]
This example uses the elliptic curve key represented in JSON Web Key
[JWK] format below:
{"kty":"EC",
"crv":"P-256",
"x":"f83OJ3D2xF1Bg8vub9tLe1gHMzV76e8Tus9uPHvRVEU",
"y":"x_FEzRu9m36HLN_tue659LNpXW6pCyStikYjKIWI5a0",
"d":"jpsQnnGQmL-YBIffH1136cspYG6-0iY7X1fCE9-E9LI"
}
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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 JWS Signing Input as inputs. The result of the digital signature
is the EC point (R, S), where R and S are unsigned integers. In this
example, the R and S values, given as octet sequences representing
big endian integers are:
+--------+----------------------------------------------------------+
| Result | Value |
| Name | |
+--------+----------------------------------------------------------+
| R | [14, 209, 33, 83, 121, 99, 108, 72, 60, 47, 127, 21, 88, |
| | 7, 212, 2, 163, 178, 40, 3, 58, 249, 124, 126, 23, 129, |
| | 154, 195, 22, 158, 166, 101] |
| S | [197, 10, 7, 211, 140, 60, 112, 229, 216, 241, 45, 175, |
| | 8, 74, 84, 128, 166, 101, 144, 197, 242, 147, 80, 154, |
| | 143, 63, 127, 138, 131, 163, 84, 213] |
+--------+----------------------------------------------------------+
The JWS Signature is the value R || S. Encoding the signature as
BASE64URL(JWS Signature) produces this value (with line breaks for
display purposes only):
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA
pmWQxfKTUJqPP3-Kg6NU1Q
Concatenating these values in the order Header.Payload.Signature with
period ('.') characters between the parts yields this complete JWS
representation using the JWS Compact Serialization (with line breaks
for display purposes only):
eyJhbGciOiJFUzI1NiJ9
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8ISlSA
pmWQxfKTUJqPP3-Kg6NU1Q
A.3.2. Validating
Since the "alg" Header Parameter is "ES256", we validate the ECDSA
P-256 SHA-256 digital signature contained in the JWS Signature.
Validating the JWS Signature is a bit different from the previous
examples. We need to split the 64 member octet sequence of the JWS
Signature (which is base64url decoded from the value encoded in the
JWS representation) into two 32 octet sequences, the first
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representing R and the second S. We then pass the public key (x, y),
the signature (R, S), and the JWS Signing Input (which is the initial
substring of the JWS Compact Serialization representation up until
but not including the second period character) to an ECDSA signature
verifier that has been configured to use the P-256 curve with the
SHA-256 hash function.
A.4. Example JWS using ECDSA P-521 SHA-512
A.4.1. Encoding
The JWS Protected Header for this example differs from the previous
example because different ECDSA curves and hash functions are used.
The JWS Protected Header used is:
{"alg":"ES512"}
The octets representing UTF8(JWS Protected Header) in this example
(using JSON array notation) are:
[123, 34, 97, 108, 103, 34, 58, 34, 69, 83, 53, 49, 50, 34, 125]
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJhbGciOiJFUzUxMiJ9
The JWS Payload used in this example, is the ASCII string "Payload".
The representation of this string is the octet sequence:
[80, 97, 121, 108, 111, 97, 100]
Encoding this JWS Payload as BASE64URL(JWS Payload) gives this value:
UGF5bG9hZA
Combining these as BASE64URL(UTF8(JWS Protected Header)) || '.' ||
BASE64URL(JWS Payload) gives this string:
eyJhbGciOiJFUzUxMiJ9.UGF5bG9hZA
The resulting JWS Signing Input value, which is the ASCII
representation of above string, is the following octet sequence:
[101, 121, 74, 104, 98, 71, 99, 105, 79, 105, 74, 70, 85, 122, 85,
120, 77, 105, 74, 57, 46, 85, 71, 70, 53, 98, 71, 57, 104, 90, 65]
This example uses the elliptic curve key represented in JSON Web Key
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[JWK] format below (with line breaks within values for display
purposes only):
{"kty":"EC",
"crv":"P-521",
"x":"AekpBQ8ST8a8VcfVOTNl353vSrDCLLJXmPk06wTjxrrjcBpXp5EOnYG_
NjFZ6OvLFV1jSfS9tsz4qUxcWceqwQGk",
"y":"ADSmRA43Z1DSNx_RvcLI87cdL07l6jQyyBXMoxVg_l2Th-x3S1WDhjDl
y79ajL4Kkd0AZMaZmh9ubmf63e3kyMj2",
"d":"AY5pb7A0UFiB3RELSD64fTLOSV_jazdF7fLYyuTw8lOfRhWg6Y6rUrPA
xerEzgdRhajnu0ferB0d53vM9mE15j2C"
}
The ECDSA private part d is then passed to an ECDSA signing function,
which also takes the curve type, P-521, the hash type, SHA-512, and
the JWS Signing Input as inputs. The result of the digital signature
is the EC point (R, S), where R and S are unsigned integers. In this
example, the R and S values, given as octet sequences representing
big endian integers are:
+--------+----------------------------------------------------------+
| Result | Value |
| Name | |
+--------+----------------------------------------------------------+
| R | [1, 220, 12, 129, 231, 171, 194, 209, 232, 135, 233, |
| | 117, 247, 105, 122, 210, 26, 125, 192, 1, 217, 21, 82, |
| | 91, 45, 240, 255, 83, 19, 34, 239, 71, 48, 157, 147, |
| | 152, 105, 18, 53, 108, 163, 214, 68, 231, 62, 153, 150, |
| | 106, 194, 164, 246, 72, 143, 138, 24, 50, 129, 223, 133, |
| | 206, 209, 172, 63, 237, 119, 109] |
| S | [0, 111, 6, 105, 44, 5, 41, 208, 128, 61, 152, 40, 92, |
| | 61, 152, 4, 150, 66, 60, 69, 247, 196, 170, 81, 193, |
| | 199, 78, 59, 194, 169, 16, 124, 9, 143, 42, 142, 131, |
| | 48, 206, 238, 34, 175, 83, 203, 220, 159, 3, 107, 155, |
| | 22, 27, 73, 111, 68, 68, 21, 238, 144, 229, 232, 148, |
| | 188, 222, 59, 242, 103] |
+--------+----------------------------------------------------------+
The JWS Signature is the value R || S. Encoding the signature as
BASE64URL(JWS Signature) produces this value (with line breaks for
display purposes only):
AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq
wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp
EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn
Concatenating these values in the order Header.Payload.Signature with
period ('.') characters between the parts yields this complete JWS
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representation using the JWS Compact Serialization (with line breaks
for display purposes only):
eyJhbGciOiJFUzUxMiJ9
.
UGF5bG9hZA
.
AdwMgeerwtHoh-l192l60hp9wAHZFVJbLfD_UxMi70cwnZOYaRI1bKPWROc-mZZq
wqT2SI-KGDKB34XO0aw_7XdtAG8GaSwFKdCAPZgoXD2YBJZCPEX3xKpRwcdOO8Kp
EHwJjyqOgzDO7iKvU8vcnwNrmxYbSW9ERBXukOXolLzeO_Jn
A.4.2. Validating
Since the "alg" Header Parameter is "ES512", we validate the ECDSA
P-521 SHA-512 digital signature contained in the JWS Signature.
Validating this JWS Signature is very similar to the previous
example. We need to split the 132 member octet sequence of the JWS
Signature into two 66 octet sequences, the first representing R and
the second S. We then pass the public key (x, y), the signature (R,
S), and the JWS Signing Input to an ECDSA signature verifier that has
been configured to use the P-521 curve with the SHA-512 hash
function.
A.5. Example Plaintext JWS
The following example JWS Protected Header declares that the encoded
object is a Plaintext JWS:
{"alg":"none"}
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJhbGciOiJub25lIn0
The JWS Payload used in this example, which follows, is the same as
in the previous examples. Since the BASE64URL(JWS Payload) value
will therefore be the same, its computation is not repeated here.
{"iss":"joe",
"exp":1300819380,
"http://example.com/is_root":true}
The JWS Signature is the empty octet string and BASE64URL(JWS
Signature) is the empty string.
Concatenating these parts in the order Header.Payload.Signature with
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period ('.') characters between the parts yields this complete JWS
(with line breaks for display purposes only):
eyJhbGciOiJub25lIn0
.
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
.
A.6. Example JWS Using JWS JSON Serialization
This section contains an example using the JWS JSON Serialization.
This example demonstrates the capability for conveying multiple
digital signatures and/or MACs for the same payload.
The JWS Payload used in this example is the same as that used in the
examples in Appendix A.2 and Appendix A.3 (with line breaks for
display purposes only):
eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFt
cGxlLmNvbS9pc19yb290Ijp0cnVlfQ
Two digital signatures are used in this example: the first using
RSASSA-PKCS-v1_5 SHA-256 and the second using ECDSA P-256 SHA-256.
For the first, the JWS Protected Header and key are the same as in
Appendix A.2, resulting in the same JWS Signature value; therefore,
its computation is not repeated here. For the second, the JWS
Protected Header and key are the same as in Appendix A.3, resulting
in the same JWS Signature value; therefore, its computation is not
repeated here.
A.6.1. JWS Per-Signature Protected Headers
The JWS Protected Header value used for the first signature is:
{"alg":"RS256"}
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
eyJhbGciOiJSUzI1NiJ9
The JWS Protected Header value used for the second signature is:
{"alg":"ES256"}
Encoding this JWS Protected Header as BASE64URL(UTF8(JWS Protected
Header)) gives this value:
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eyJhbGciOiJFUzI1NiJ9
A.6.2. JWS Per-Signature Unprotected Headers
Key ID values are supplied for both keys using per-signature Header
Parameters. The two values used to represent these Key IDs are:
{"kid":"2010-12-29"}
and
{"kid":"e9bc097a-ce51-4036-9562-d2ade882db0d"}
A.6.3. Complete JOSE Header Values
Combining the protected and unprotected header values supplied, the
JOSE Header values used for the first and second signatures
respectively are:
{"alg":"RS256",
"kid":"2010-12-29"}
and
{"alg":"ES256",
"kid":"e9bc097a-ce51-4036-9562-d2ade882db0d"}
A.6.4. Complete JWS JSON Serialization Representation
The complete JSON Web Signature JSON Serialization for these values
is as follows (with line breaks within values for display purposes
only):
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{"payload":
"eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGF
tcGxlLmNvbS9pc19yb290Ijp0cnVlfQ",
"signatures":[
{"protected":"eyJhbGciOiJSUzI1NiJ9",
"header":
{"kid":"2010-12-29"},
"signature":
"cC4hiUPoj9Eetdgtv3hF80EGrhuB__dzERat0XF9g2VtQgr9PJbu3XOiZj5RZ
mh7AAuHIm4Bh-0Qc_lF5YKt_O8W2Fp5jujGbds9uJdbF9CUAr7t1dnZcAcQjb
KBYNX4BAynRFdiuB--f_nZLgrnbyTyWzO75vRK5h6xBArLIARNPvkSjtQBMHl
b1L07Qe7K0GarZRmB_eSN9383LcOLn6_dO--xi12jzDwusC-eOkHWEsqtFZES
c6BfI7noOPqvhJ1phCnvWh6IeYI2w9QOYEUipUTI8np6LbgGY9Fs98rqVt5AX
LIhWkWywlVmtVrBp0igcN_IoypGlUPQGe77Rw"},
{"protected":"eyJhbGciOiJFUzI1NiJ9",
"header":
{"kid":"e9bc097a-ce51-4036-9562-d2ade882db0d"},
"signature":
"DtEhU3ljbEg8L38VWAfUAqOyKAM6-Xx-F4GawxaepmXFCgfTjDxw5djxLa8IS
lSApmWQxfKTUJqPP3-Kg6NU1Q"}]
}
Appendix B. "x5c" (X.509 Certificate Chain) Example
The JSON array below is an example of a certificate chain that could
be used as the value of an "x5c" (X.509 Certificate Chain) Header
Parameter, per Section 4.1.6. Note that since these strings contain
base64 encoded (not base64url encoded) values, they are allowed to
contain white space and line breaks.
["MIIE3jCCA8agAwIBAgICAwEwDQYJKoZIhvcNAQEFBQAwYzELMAkGA1UEBhMCVVM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keS5jb20wRgYDVR0fBD8wPTA7oDmgN4Y1aHR0cDovL2NlcnRpZmljYXRlcy5nb2
RhZGR5LmNvbS9yZXBvc2l0b3J5L2dkcm9vdC5jcmwwSwYDVR0gBEQwQjBABgRVH
SAAMDgwNgYIKwYBBQUHAgEWKmh0dHA6Ly9jZXJ0aWZpY2F0ZXMuZ29kYWRkeS5j
b20vcmVwb3NpdG9yeTAOBgNVHQ8BAf8EBAMCAQYwDQYJKoZIhvcNAQEFBQADggE
BANKGwOy9+aG2Z+5mC6IGOgRQjhVyrEp0lVPLN8tESe8HkGsz2ZbwlFalEzAFPI
UyIXvJxwqoJKSQ3kbTJSMUA2fCENZvD117esyfxVgqwcSeIaha86ykRvOe5GPLL
5CkKSkB2XIsKd83ASe8T+5o0yGPwLPk9Qnt0hCqU7S+8MxZC9Y7lhyVJEnfzuz9
p0iRFEUOOjZv2kWzRaJBydTXRE4+uXR21aITVSzGh6O1mawGhId/dQb8vxRMDsx
uxN89txJx9OjxUUAiKEngHUuHqDTMBqLdElrRhjZkAzVvb3du6/KFUJheqwNTrZ
EjYx8WnM25sgVjOuH0aBsXBTWVU+4=",
"MIIE+zCCBGSgAwIBAgICAQ0wDQYJKoZIhvcNAQEFBQAwgbsxJDAiBgNVBAcTG1Z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",
"MIIC5zCCAlACAQEwDQYJKoZIhvcNAQEFBQAwgbsxJDAiBgNVBAcTG1ZhbGlDZXJ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vIWZJV16vYdA757tn2VUdZZUcOBVXc65g2PFxTXdMwzzjsvUGJ7SVCCSRrCl6zf
N1SLUzm1NZ9WlmpZdRJEy0kTRxQb7XBhVQ7/nHk01xC+YDgkRoKWzk2Z/M/VXwb
P7RfZHM047QSv4dk+NoS/zcnwbNDu+97bi5p9wIDAQABMA0GCSqGSIb3DQEBBQU
AA4GBADt/UG9vUJSZSWI4OB9L+KXIPqeCgfYrx+jFzug6EILLGACOTb2oWH+heQ
C1u+mNr0HZDzTuIYEZoDJJKPTEjlbVUjP9UNV+mWwD5MlM/Mtsq2azSiGM5bUMM
j4QssxsodyamEwCW/POuZ6lcg5Ktz885hZo+L7tdEy8W9ViH0Pd"]
Appendix C. Notes on implementing base64url encoding without padding
This appendix describes how to implement base64url encoding and
decoding functions without padding based upon standard base64
encoding and decoding functions that do use padding.
To be concrete, example C# code implementing these functions is shown
below. Similar code could be used in other languages.
static string base64urlencode(byte [] arg)
{
string s = Convert.ToBase64String(arg); // Regular base64 encoder
s = s.Split('=')[0]; // Remove any trailing '='s
s = s.Replace('+', '-'); // 62nd char of encoding
s = s.Replace('/', '_'); // 63rd char of encoding
return s;
}
static byte [] base64urldecode(string arg)
{
string s = arg;
s = s.Replace('-', '+'); // 62nd char of encoding
s = s.Replace('_', '/'); // 63rd char of encoding
switch (s.Length % 4) // Pad with trailing '='s
{
case 0: break; // No pad chars in this case
case 2: s += "=="; break; // Two pad chars
case 3: s += "="; break; // One pad char
default: throw new System.Exception(
"Illegal base64url string!");
}
return Convert.FromBase64String(s); // Standard base64 decoder
}
As per the example code above, the number of '=' padding characters
that needs to be added to the end of a base64url encoded string
without padding to turn it into one with padding is a deterministic
function of the length of the encoded string. Specifically, if the
length mod 4 is 0, no padding is added; if the length mod 4 is 2, two
'=' padding characters are added; if the length mod 4 is 3, one '='
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padding character is added; if the length mod 4 is 1, the input is
malformed.
An example correspondence between unencoded and encoded values
follows. The octet sequence below encodes into the string below,
which when decoded, reproduces the octet sequence.
3 236 255 224 193
A-z_4ME
Appendix D. Notes on Key Selection
This appendix describes a set of possible algorithms for selecting
the key to be used to validate the digital signature or MAC of a JWS
object or for selecting the key to be used to decrypt a JWE object.
This guidance describes a family of possible algorithms, rather than
a single algorithm, because in different contexts, not all the
sources of keys will be used, they can be tried in different orders,
and sometimes not all the collected keys will be tried; hence,
different algorithms will be used in different application contexts.
The steps below are described for illustration purposes only;
specific applications can and are likely to use different algorithms
or perform some of the steps in different orders. Specific
applications will frequently have a much simpler method of
determining the keys to use, as there may be one or two key selection
methods that are profiled for the application's use. This appendix
supplements the normative information on key location in Section 6.
These algorithms include the following steps. Note that the steps
can be performed in any order and do not need to be treated as
distinct. For example, keys can be tried as soon as they are found,
rather than collecting all the keys before trying any.
1. Collect the set of potentially applicable keys. Sources of keys
may include:
* Keys supplied by the application protocol being used.
* Keys referenced by the "jku" (JWK Set URL) Header Parameter.
* The key provided by the "jwk" (JSON Web Key) Header Parameter.
* The key referenced by the "x5u" (X.509 URL) Header Parameter.
* The key provided by the "x5c" (X.509 Certificate Chain) Header
Parameter.
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* Other applicable keys available to the application.
The order for collecting and trying keys from different key
sources is typically application dependent. For example,
frequently all keys from a one set of locations, such as local
caches, will be tried before collecting and trying keys from
other locations.
2. Filter the set of collected keys. For instance, some
applications will use only keys referenced by "kid" (key ID) or
"x5t" (X.509 certificate SHA-1 thumbprint) parameters. If the
application uses the "alg" (algorithm), "use" (public key use),
or "key_ops" (key operations) parameters, keys with keys with
inappropriate values of those parameters would be excluded.
Additionally, keys might be filtered to include or exclude keys
with certain other member values in an application specific
manner. For some applications, no filtering will be applied.
3. Order the set of collected keys. For instance, keys referenced
by "kid" (Key ID) or "x5t" (X.509 Certificate SHA-1 Thumbprint)
parameters might be tried before keys with neither of these
values. Likewise, keys with certain member values might be
ordered before keys with other member values. For some
applications, no ordering will be applied.
4. Make trust decisions about the keys. Signatures made with keys
not meeting the application's trust criteria would not be
accepted. Such criteria might include, but is not limited to the
source of the key, whether the TLS certificate validates for keys
retrieved from URLs, whether a key in an X.509 certificate is
backed by a valid certificate chain, and other information known
by the application.
5. Attempt signature or MAC validation for a JWS object or
decryption of a JWE object with some or all of the collected and
possibly filtered and/or ordered keys. A limit on the number of
keys to be tried might be applied. This process will normally
terminate following a successful validation or decryption.
Note that it is reasonable for some applications to perform signature
or MAC validation prior to making a trust decision about a key, since
keys for which the validation fails need no trust decision.
Appendix E. Negative Test Case for "crit" Header Parameter
Conforming implementations must reject input containing critical
extensions that are not understood or cannot be processed. The
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following JWS must be rejected by all implementations, because it
uses an extension Header Parameter name
"http://example.invalid/UNDEFINED" that they do not understand. Any
other similar input, in which the use of the value
"http://example.invalid/UNDEFINED" is substituted for any other
Header Parameter name not understood by the implementation, must also
be rejected.
The JWS Protected Header value for this JWS is:
{"alg":"none",
"crit":["http://example.invalid/UNDEFINED"],
"http://example.invalid/UNDEFINED":true
}
The complete JWS that must be rejected is as follows (with line
breaks for display purposes only):
eyJhbGciOiJub25lIiwNCiAiY3JpdCI6WyJodHRwOi8vZXhhbXBsZS5jb20vVU5ERU
ZJTkVEIl0sDQogImh0dHA6Ly9leGFtcGxlLmNvbS9VTkRFRklORUQiOnRydWUNCn0.
RkFJTA.
Appendix F. Detached Content
In some contexts, it is useful integrity protect content that is not
itself contained in a JWS object. One way to do this is create a JWS
object in the normal fashion using a representation of the content as
the payload, but then delete the payload representation from the JWS,
and send this modified object to the recipient, rather than the JWS.
When using the JWS Compact Serialization, the deletion is
accomplished by replacing the second field (which contains
BASE64URL(JWS Payload)) value with the empty string; when using the
JWS JSON Serialization, the deletion is accomplished by deleting the
"payload" member. This method assumes that the recipient can
reconstruct the exact payload used in the JWS. To use the modified
object, the recipient reconstructs the JWS by re-inserting the
payload representation into the modified object, and uses the
resulting JWS in the usual manner. Note that this method needs no
support from JWS libraries, as applications can use this method by
modifying the inputs and outputs of standard JWS libraries.
Appendix G. Acknowledgements
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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Thanks to Axel Nennker for his early implementation and feedback on
the JWS and JWE specifications.
This specification is the work of the JOSE Working Group, which
includes dozens of active and dedicated participants. In particular,
the following individuals contributed ideas, feedback, and wording
that influenced this specification:
Dirk Balfanz, Richard Barnes, Brian Campbell, Breno de Medeiros, Dick
Hardt, Joe Hildebrand, Jeff Hodges, Edmund Jay, Yaron Y. Goland, Ben
Laurie, James Manger, Matt Miller, Kathleen Moriarty, Tony Nadalin,
Hideki Nara, Axel Nennker, John Panzer, Emmanuel Raviart, Eric
Rescorla, Jim Schaad, Paul Tarjan, Hannes Tschofenig, and Sean
Turner.
Jim Schaad and Karen O'Donoghue chaired the JOSE working group and
Sean Turner, Stephen Farrell, and Kathleen Moriarty served as
Security area directors during the creation of this specification.
Appendix H. Document History
[[ to be removed by the RFC Editor before publication as an RFC ]]
-31
o Reworded the language about JWS implementations ignoring the "typ"
and "cty" parameters, explicitly saying that their processing is
performed by JWS applications.
o Added additional guidance on ciphersuites currently considered to
be appropriate for use, including a reference to a recent update
by the TLS working group.
-30
o Added subsection headings within the Overview section for the two
serializations.
o Added references and cleaned up the reference syntax in a few
places.
o Applied minor wording changes to the Security Considerations
section and made other local editorial improvements.
-29
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o Replaced the terms JWS Header, JWE Header, and JWT Header with a
single JOSE Header term defined in the JWS specification. This
also enabled a single Header Parameter definition to be used and
reduced other areas of duplication between specifications.
-28
o Revised the introduction to the Security Considerations section.
Also introduced additional subsection headings for security
considerations items and also moved a security consideration item
here from the JWA draft.
o Added text about when applications typically would and would not
use "typ" and "cty" header parameters.
-27
o Added the "x5t#S256" (X.509 Certificate SHA-256 Thumbprint) header
parameter.
o Stated that any JSON inputs not conforming to the JSON-text syntax
defined in RFC 7159 input MUST be rejected in their entirety.
o Simplified the TLS requirements.
-26
o Referenced Section 6 of RFC 6125 for TLS server certificate
identity validation.
o Described potential sources of ambiguity in representing the JSON
objects used in the examples. The octets of the actual UTF-8
representations of the JSON objects used in the examples are
included to remove these ambiguities.
o Added a small amount of additional explanatory text to the
signature validation examples to aid implementers.
o Noted that octet sequences are depicted using JSON array notation.
o Updated references, including to W3C specifications.
-25
o No changes were made, other than to the version number and date.
-24
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o Updated the JSON reference to RFC 7159.
-23
o Clarified that the base64url encoding includes no line breaks,
white space, or other additional characters.
-22
o Corrected RFC 2119 terminology usage.
o Replaced references to draft-ietf-json-rfc4627bis with RFC 7158.
-21
o Applied review comments to the appendix "Notes on Key Selection",
addressing issue #93.
o Changed some references from being normative to informative,
addressing issue #90.
o Applied review comments to the JSON Serialization section,
addressing issue #121.
-20
o Made terminology definitions more consistent, addressing issue
#165.
o Restructured the JSON Serialization section to call out the
parameters used in hanging lists, addressing issue #121.
o Described key filtering and refined other aspects of the text in
the appendix "Notes on Key Selection", addressing issue #93.
o Replaced references to RFC 4627 with draft-ietf-json-rfc4627bis,
addressing issue #90.
-19
o Added the appendix "Notes on Validation Key Selection", addressing
issue #93.
o Reordered the key selection parameters.
-18
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o Updated the mandatory-to-implement (MTI) language to say that
applications using this specification need to specify what
serialization and serialization features are used for that
application, addressing issue #119.
o Changes to address editorial and minor issues #25, #89, #97, #110,
#114, #115, #116, #117, #120, and #184.
o Added and used Header Parameter Description registry field.
-17
o Refined the "typ" and "cty" definitions to always be MIME Media
Types, with the omission of "application/" prefixes recommended
for brevity, addressing issue #50.
o Updated the mandatory-to-implement (MTI) language to say that
general-purpose implementations must implement the single
signature/MAC value case for both serializations whereas special-
purpose implementations can implement just one serialization if
that meets the needs of the use cases the implementation is
designed for, addressing issue #119.
o Explicitly named all the logical components of a JWS and defined
the processing rules and serializations in terms of those
components, addressing issues #60, #61, and #62.
o Replaced verbose repetitive phases such as "base64url encode the
octets of the UTF-8 representation of X" with mathematical
notation such as "BASE64URL(UTF8(X))".
o Terms used in multiple documents are now defined in one place and
incorporated by reference. Some lightly used or obvious terms
were also removed. This addresses issue #58.
-16
o Changes to address editorial and minor issues #50, #98, #99, #102,
#104, #106, #107, #111, and #112.
-15
o Clarified that it is an application decision which signatures,
MACs, or plaintext values must successfully validate for the JWS
to be accepted, addressing issue #35.
o Corrected editorial error in "ES512" example.
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o Changes to address editorial and minor issues #34, #96, #100,
#101, #104, #105, and #106.
-14
o Stated that the "signature" parameter is to be omitted in the JWS
JSON Serialization when its value would be empty (which is only
the case for a Plaintext JWS).
-13
o Made all header parameter values be per-signature/MAC, addressing
issue #24.
-12
o Clarified that the "typ" and "cty" header parameters are used in
an application-specific manner and have no effect upon the JWS
processing.
o Replaced the MIME types "application/jws+json" and
"application/jws" with "application/jose+json" and
"application/jose".
o Stated that recipients MUST either reject JWSs with duplicate
Header Parameter Names or use a JSON parser that returns only the
lexically last duplicate member name.
o Added a Serializations section with parallel treatment of the JWS
Compact Serialization and the JWS JSON Serialization and also
moved the former Implementation Considerations content there.
-11
o Added Key Identification section.
o For the JWS JSON Serialization, enable header parameter values to
be specified in any of three parameters: the "protected" member
that is integrity protected and shared among all recipients, the
"unprotected" member that is not integrity protected and shared
among all recipients, and the "header" member that is not
integrity protected and specific to a particular recipient. (This
does not affect the JWS Compact Serialization, in which all header
parameter values are in a single integrity protected JWE Header
value.)
o Removed suggested compact serialization for multiple digital
signatures and/or MACs.
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o Changed the MIME type name "application/jws-js" to
"application/jws+json", addressing issue #22.
o Tightened the description of the "crit" (critical) header
parameter.
o Added a negative test case for the "crit" header parameter
-10
o Added an appendix suggesting a possible compact serialization for
JWSs with multiple digital signatures and/or MACs.
-09
o Added JWS JSON Serialization, as specified by
draft-jones-jose-jws-json-serialization-04.
o Registered "application/jws-js" MIME type and "JWS-JS" typ header
parameter value.
o Defined that the default action for header parameters that are not
understood is to ignore them unless specifically designated as
"MUST be understood" or included in the new "crit" (critical)
header parameter list. This addressed issue #6.
o Changed term "JWS Secured Input" to "JWS Signing Input".
o Changed from using the term "byte" to "octet" when referring to 8
bit values.
o Changed member name from "recipients" to "signatures" in the JWS
JSON Serialization.
o Added complete values using the JWS Compact Serialization for all
examples.
-08
o Applied editorial improvements suggested by Jeff Hodges and Hannes
Tschofenig. Many of these simplified the terminology used.
o Clarified statements of the form "This header parameter is
OPTIONAL" to "Use of this header parameter is OPTIONAL".
o Added a Header Parameter Usage Location(s) field to the IANA JSON
Web Signature and Encryption Header Parameters registry.
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o Added seriesInfo information to Internet Draft references.
-07
o Updated references.
-06
o Changed "x5c" (X.509 Certificate Chain) representation from being
a single string to being an array of strings, each containing a
single base64 encoded DER certificate value, representing elements
of the certificate chain.
o Applied changes made by the RFC Editor to RFC 6749's registry
language to this specification.
-05
o Added statement that "StringOrURI values are compared as case-
sensitive strings with no transformations or canonicalizations
applied".
o Indented artwork elements to better distinguish them from the body
text.
-04
o Completed JSON Security Considerations section, including
considerations about rejecting input with duplicate member names.
o Completed security considerations on the use of a SHA-1 hash when
computing "x5t" (x.509 certificate thumbprint) values.
o Refer to the registries as the primary sources of defined values
and then secondarily reference the sections defining the initial
contents of the registries.
o Normatively reference XML DSIG 2.0 for its security
considerations.
o Added this language to Registration Templates: "This name is case
sensitive. Names that match other registered names in a case
insensitive manner SHOULD NOT be accepted."
o Reference draft-jones-jose-jws-json-serialization instead of
draft-jones-json-web-signature-json-serialization.
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o Described additional open issues.
o Applied editorial suggestions.
-03
o Added the "cty" (content type) header parameter for declaring type
information about the secured content, as opposed to the "typ"
(type) header parameter, which declares type information about
this object.
o Added "Collision Resistant Namespace" to the terminology section.
o Reference ITU.X690.1994 for DER encoding.
o Added an example JWS using ECDSA P-521 SHA-512. This has
particular illustrative value because of the use of the 521 bit
integers in the key and signature values. This is also an example
in which the payload is not a base64url encoded JSON object.
o Added an example "x5c" value.
o No longer say "the UTF-8 representation of the JWS Secured Input
(which is the same as the ASCII representation)". Just call it
"the ASCII representation of the JWS Secured Input".
o Added Registration Template sections for defined registries.
o Added Registry Contents sections to populate registry values.
o Changed name of the JSON Web Signature and Encryption "typ" Values
registry to be the JSON Web Signature and Encryption Type Values
registry, since it is used for more than just values of the "typ"
parameter.
o Moved registries JSON Web Signature and Encryption Header
Parameters and JSON Web Signature and Encryption Type Values to
the JWS specification.
o Numerous editorial improvements.
-02
o Clarified that it is an error when a "kid" value is included and
no matching key is found.
o Removed assumption that "kid" (key ID) can only refer to an
asymmetric key.
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o Clarified that JWSs with duplicate Header Parameter Names MUST be
rejected.
o Clarified the relationship between "typ" header parameter values
and MIME types.
o Registered application/jws MIME type and "JWS" typ header
parameter value.
o Simplified JWK terminology to get replace the "JWK Key Object" and
"JWK Container Object" terms with simply "JSON Web Key (JWK)" and
"JSON Web Key Set (JWK Set)" and to eliminate potential confusion
between single keys and sets of keys. As part of this change, the
Header Parameter Name for a public key value was changed from
"jpk" (JSON Public Key) to "jwk" (JSON Web Key).
o Added suggestion on defining additional header parameters such as
"x5t#S256" in the future for certificate thumbprints using hash
algorithms other than SHA-1.
o Specify RFC 2818 server identity validation, rather than RFC 6125
(paralleling the same decision in the OAuth specs).
o Generalized language to refer to Message Authentication Codes
(MACs) rather than Hash-based Message Authentication Codes (HMACs)
unless in a context specific to HMAC algorithms.
o Reformatted to give each header parameter its own section heading.
-01
o Moved definition of Plaintext JWSs (using "alg":"none") here from
the JWT specification since this functionality is likely to be
useful in more contexts that just for JWTs.
o Added "jpk" and "x5c" header parameters for including JWK public
keys and X.509 certificate chains directly in the header.
o Clarified that this specification is defining the JWS Compact
Serialization. Referenced the new JWS-JS spec, which defines the
JWS JSON Serialization.
o Added text "New header parameters should be introduced sparingly
since an implementation that does not understand a parameter MUST
reject the JWS".
o Clarified that the order of the creation and validation steps is
not significant in cases where there are no dependencies between
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the inputs and outputs of the steps.
o Changed "no canonicalization is performed" to "no canonicalization
need be performed".
o Corrected the Magic Signatures reference.
o Made other editorial improvements suggested by JOSE working group
participants.
-00
o Created the initial IETF draft based upon
draft-jones-json-web-signature-04 with no normative changes.
o Changed terminology to no longer call both digital signatures and
HMACs "signatures".
Authors' Addresses
Michael B. Jones
Microsoft
Email: mbj@microsoft.com
URI: http://self-issued.info/
John Bradley
Ping Identity
Email: ve7jtb@ve7jtb.com
URI: http://www.thread-safe.com/
Nat Sakimura
Nomura Research Institute
Email: n-sakimura@nri.co.jp
URI: http://nat.sakimura.org/
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