Network Working Group T. Looker, Ed.
Internet-Draft Mattr
Intended status: Standards Track December 21, 2019
Expires: June 23, 2020
JSON Web Message
draft-looker-jwm-00
Abstract
JSON Web Message (JWM) is a flexible way of describing an
application-level message encoded in JSON that is suitable for
transfer over a variety of transport protocols. JWMs through the
application of JSON Web Signature (JWS) and JSON Web Encryption (JWE)
can be digitally signed, integrity protected and or achieve
confidentiality via encryption.
Status of This Memo
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provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on June 23, 2020.
Copyright Notice
Copyright (c) 2019 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
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include Simplified BSD License text as described in Section 4.e of
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Notational Conventions . . . . . . . . . . . . . . . . . 3
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. JSON Web Message (JWM) Overview . . . . . . . . . . . . . . . 4
2.1. Relationship to JWT . . . . . . . . . . . . . . . . . . . 4
2.2. Example Signed JWM . . . . . . . . . . . . . . . . . . . 5
2.3. Example Encrypted JWM . . . . . . . . . . . . . . . . . . 7
3. JWM Attributes . . . . . . . . . . . . . . . . . . . . . . . 9
3.1. Registered Attribute Names . . . . . . . . . . . . . . . 10
3.1.1. "id" Attribute . . . . . . . . . . . . . . . . . . . 10
3.1.2. "type" Attribute . . . . . . . . . . . . . . . . . . 10
3.1.3. "body" Attribute . . . . . . . . . . . . . . . . . . 10
3.1.4. "to" Attribute . . . . . . . . . . . . . . . . . . . 11
3.1.5. "from" Attribute . . . . . . . . . . . . . . . . . . 11
3.1.6. "thread_id" Attribute . . . . . . . . . . . . . . . . 11
3.1.7. "referent_id" Attribute . . . . . . . . . . . . . . . 11
3.1.8. "time_stamp" Attribute . . . . . . . . . . . . . . . 11
3.1.9. "expiry" Attribute . . . . . . . . . . . . . . . . . 11
3.1.10. "reply_url" Attribute . . . . . . . . . . . . . . . . 12
3.1.11. "reply_to" Attribute . . . . . . . . . . . . . . . . 12
3.2. Public Attribute Names . . . . . . . . . . . . . . . . . 12
3.3. Private Attribute Names . . . . . . . . . . . . . . . . . 12
4. JOSE Header . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. "typ" (Type) Header Parameter . . . . . . . . . . . . . . 13
4.2. "cty" (Content Type) Header Parameter . . . . . . . . . . 13
4.3. Replicating Attributes as Header Parameters . . . . . . . 13
5. Creating and Validating JWMs . . . . . . . . . . . . . . . . 14
5.1. Creating a JWM . . . . . . . . . . . . . . . . . . . . . 14
5.2. Validating a JWM . . . . . . . . . . . . . . . . . . . . 15
5.3. String Comparison Rules . . . . . . . . . . . . . . . . . 16
6. Implementation Requirements . . . . . . . . . . . . . . . . . 17
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7.1. Registration Template . . . . . . . . . . . . . . . . . . 17
7.1.1. Attribute Name: . . . . . . . . . . . . . . . . . . . 17
7.1.2. Attribute Description . . . . . . . . . . . . . . . . 18
7.1.3. Change Controller . . . . . . . . . . . . . . . . . . 18
7.1.4. Specification Document(s) . . . . . . . . . . . . . . 18
7.1.5. Initial Registry Contents . . . . . . . . . . . . . . 18
8. Media Type Registration . . . . . . . . . . . . . . . . . . . 19
8.1. Registry Contents . . . . . . . . . . . . . . . . . . . . 19
9. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9.1. Trust Decisions . . . . . . . . . . . . . . . . . . . . . 19
9.2. Signing and Encryption Order . . . . . . . . . . . . . . 20
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10. Privacy Considerations . . . . . . . . . . . . . . . . . . . 20
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
12. Normative References . . . . . . . . . . . . . . . . . . . . 20
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction
JSON Web Message (JWM) is a flexible way of describing an
application-level message encoded in JSON that is suitable for
transfer over a variety of transport protocols. JWMs through the
application of JSON Web Signature (JWS) and JSON Web Encryption (JWE)
can be digitally signed, integrity protected and or achieve
confidentiality via encryption. JWMs are inspired by JWTs [RFC7519],
more details about this relationship is documented in Section 2.1.
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 BCP
14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they
appear in all capitals, as shown here.
1.2. Terminology
The terms "JSON Web Signature (JWS)", "Base64url Encoding", "Header
Parameter", "JOSE Header", "JWS Payload", "JWS Signature", "JWS
Compact Serialization" and "JWS JSON Serialization" are defined by
the JWS specification [RFC7515].
The terms "JSON Web Encryption (JWE)", "JWE Compact Serialization"
and "JWE JSON Serialization" are defined by the JWE specification
[RFC7516].
The terms "StringOrURI", "NumericDate" are defined by the JWT
specification [RFC7519].
The following terms are defined by this specification:
JSON Web Message A JWM Attribute Set, encoded in a JWS and or JWE,
enabling it to be digitally signed and/or encrypted.
JWM Attribute Set A JSON object of attributes conveyed by the JWM.
Attribute A piece of information conveyed in a message, sent from a
sender intended for processing by a recipient or recipients. An
attribute is represented as a name/value pair consisting of an
Attribute Name and an Attribute Value.
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Attribute Name The name portion of an attribute representation. An
attribute name is always a string.
Attribute Value The value portion of an attribute representation.
An attribute value can be any JSON value.
Nested JWM A JWM in which nested signing and/or encryption is
employed. In Nested JWMs, a JWM is used as the payload or
plaintext value of an enclosing JWS or JWE structure,
respectively.
2. JSON Web Message (JWM) Overview
2.1. Relationship to JWT
JWMs conceptually share many parallels to JWTs, these similarities
can be summarized in the following way.
o A JWM contains a JSON object comprised of attributes known as a
JWM Attribute Set, where the attributes featured in the set can be
public, private or registered in an IANA registry, this is
conceptually parallel to claims in JWTs, the JWT Claim Set and the
JWT claims IANA registry.
o A JWM leverages JSON Web Signature (JWS) and or JSON Web
Encryption (JWE) to achieve digital signing, integrity protection
and or confidentiality via encryption for the JWM attribute set in
similar ways to JWT for the JWT claim set.
JWMs also deviate in important ways from JWTs which prevents using
the JWT specification directly to achieve the functionality provided
by a JWM.
o JWTs due to the requirement of them being compact in nature and
URL safe, mandate the usage of compact serialization for both JWS
and JWE representations. This compact serialization requirement
for JWS and JWE limits JWTs to only being able to feature a single
digital signature and or encrypt a payload to a single recipient.
Whereas JWMs do not require the use of compact serialization of
JWE, instead they permit the JSON based serialization of JWS and
JWE, which allows for a JWM to feature multiple digital signature
or encrypted to multiple recipients.
o JWM and JWT have different intents. A JWM is about a sender
creating a message composed of attributes, where the message is
destined for a recipient or recipients. Whereas a JWT is about an
issuer expressing claims about a subject to an audience.
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o The primary usage of JWTs centers around creating tokens that are
digitally signed or integrity protected through a Message
Authentication Code (MAC) by leveraging JWS. Encrypted JWTs via
JWE are less common and as defined in Section 8 of [RFC7519] they
are optional to implement. Whereas JWMs require both JWS and JWE
implementations.
o JWTs support an insecure format as defined in Section 6 of
[RFC7519], JWMs do not allow this format due to the
vulnerabilities it introduces.
In the spirit of specification re-use and promoting ease of
understanding, this specifications structure is inspired by
[RFC7519].
2.2. Example Signed JWM
The following example JOSE Header declares that the object is a JWM,
and the JWM is a JWS that has been digitally signed using ECDSA with
the curve p-256 and SHA-256 as the hashing algorithm ("ES256"). The
signer of the JWM has indicated that the key used to sign the JWM is
identified by "Ef1sFuyOozYm3CEY4iCdwqxiSyXZ5Br-eUDdQXk6jaQ" (with
line breaks for display purposes only):
{"typ":"JWM",
"kid":"Ef1sFuyOozYm3CEY4iCdwqxiSyXZ5Br-eUDdQXk6jaQ",
"alg":"ES256"}
Base64url encoding the octets of the UTF-8 representation of the JOSE
Header yields this encoded JOSE Header value (with line breaks for
display purposes only):
eyJ0eXAiOiJKV00iLCJraWQiOiJFZjFzRnV5T296WW0zQ0VZNGlDZHdxeGlTeVhaNUJyL
WVVRGRRWGs2amFRIiwiYWxnIjoiRVMyNTYifQ
The following is an example of a JWM Attributes Set (with line breaks
for display purposes only):
{"id":"urn:uuid:ef5a7369-f0b9-4143-a49d-2b9c7ee51117",
"type":"hello-world-message-type",
"from":"urn:uuid:8abdf5fb-621e-4cf5-a595-071bc2c91d82",
"expiry":1516239022,
"time_stamp":1516269022,
"body":{"message": "Hello world!"}}
Base64url encoding the octets of the UTF-8 the JWS Payload yields
this encoded JWS Payload (with line breaks for display purposes
only):
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eyJpZCI6InVybjp1dWlkOmVmNWE3MzY5LWYwYjktNDE0My1hNDlkLTJiOWM3ZWU1MTExN
yIsInR5cGUiOiJoZWxsby13b3JsZC1tZXNzYWdlLXR5cGUiLCJmcm9tIjoidXJuOnV1aW
Q6OGFiZGY1ZmItNjIxZS00Y2Y1LWE1OTUtMDcxYmMyYzkxZDgyIiwiZXhwaXJ5IjoxNTE
2MjM5MDIyLCJ0aW1lX3N0YW1wIjoxNTE2MjY5MDIyLCJib2R5Ijp7Im1lc3NhZ2UiOiJI
ZWxsbyB3b3JsZCEifX0
Computing the signature of the encoded JOSE Header and encoded JWS
Payload with the ECDSA with the curve p-256 and SHA-256 as the
hashing algorithm algorithm and base64url encoding the value in the
manner specified in [RFC7515] yields this encoded JWS Signature:
H8-ceviETFwgo7A2kMhrKGmlw0cEDEzCCmN8MzOVoL1RMz5dAY0kzG1Fsou_r_FUftb7t
lGqCdOVeR9EajIe6Q
Compact Serialization (with line breaks for display purposes only):
eyJ0eXAiOiJKV00iLCJraWQiOiJFZjFzRnV5T296WW0zQ0VZNGlDZHdxeGlTeVhaNUJyL
WVVRGRRWGs2amFRIiwiYWxnIjoiRVMyNTYifQ
.
eyJpZCI6InVybjp1dWlkOmVmNWE3MzY5LWYwYjktNDE0My1hNDlkLTJiOWM3ZWU1MTExN
yIsInR5cGUiOiJoZWxsby13b3JsZC1tZXNzYWdlLXR5cGUiLCJmcm9tIjoidXJuOnV1aW
Q6OGFiZGY1ZmItNjIxZS00Y2Y1LWE1OTUtMDcxYmMyYzkxZDgyIiwiZXhwaXJ5IjoxNTE
2MjM5MDIyLCJ0aW1lX3N0YW1wIjoxNTE2MjY5MDIyLCJib2R5Ijp7Im1lc3NhZ2UiOiJI
ZWxsbyB3b3JsZCEifX0
.
H8-ceviETFwgo7A2kMhrKGmlw0cEDEzCCmN8MzOVoL1RMz5dAY0kzG1Fsou_r_FUftb7t
lGqCdOVeR9EajIe6Q
JSON Serialization: (with line breaks for display purposes only):
{
"payload":"eyJpZCI6InVybjp1dWlkOmVmNWE3MzY5LWYwYjktNDE0My1hNDl
kLTJiOWM3ZWU1MTExNyIsInR5cGUiOiJoZWxsby13b3JsZC1tZXNzYWdlLXR5c
GUiLCJmcm9tIjoidXJuOnV1aWQ6OGFiZGY1ZmItNjIxZS00Y2Y1LWE1OTUtMDc
xYmMyYzkxZDgyIiwiZXhwaXJ5IjoxNTE2MjM5MDIyLCJ0aW1lX3N0YW1wIjoxN
TE2MjY5MDIyLCJib2R5Ijp7Im1lc3NhZ2UiOiJIZWxsbyB3b3JsZCEifX0=",
"signatures":[
{
"protected":"eyJhbGciOiJub25lIn0",
"signature":"CtPivEwo4eDSyjdEGJNi7wudp7suB2l9gj3jWR1FW8J8y
PAp8qgo-8yJeJr5Dsl_w4XIMa_2Wt2O7AE2Kuckw"
}
]
}
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2.3. Example Encrypted JWM
The following example JOSE Header declares that the object is a JWM,
and the JWM is a JWE that has been encrypted using AES in Galois/
Counter Mode (GCM) with 256-bit for content encryption (with line
breaks for display purposes only):
{
"typ":"JWM",
"enc":"A256GCM"
}
The following JOSE Header declares that the sender has used Elliptic
Curve Diffie-Hellman Ephemeral Static (ECDH-ES+A256KW) for key
agreement with AES based key wrapping to encrypt the content
encryption key (CEK). The keys required to perform the opposite
Diffie-Helman are identified by the key id of
"PGoXzs0NWaR_meKgTZLbEuDoSVTaFuyrbWI7V9dpjCg" along with the
ephemeral public key declared by the JSON object "epk". The
encrypted CEK is represented by the "encrypted_key" field (with line
breaks for display purposes only):
{
"kid": "PGoXzs0NWaR_meKgTZLbEuDoSVTaFuyrbWI7V9dpjCg",
"alg": "ECDH-ES+A256KW",
"epk": {
"kty": "EC",
"crv": "P-256",
"x": "6PbSGRsybgGnT0uWu1r6ZyY6gMBTYTmv-SYIjJGYGrw",
"y": "8SniQTY5zS7QolG3gy6SapqPE1ZxI_W43FiPmFoP2R4"
}
}
Because the JWE features a single recipient, the two JOSE headers are
combined into a single JOSE header, that can be represented as the
following.
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{
"typ": "JWM",
"enc": "A256GCM",
"kid": "PGoXzs0NWaR_meKgTZLbEuDoSVTaFuyrbWI7V9dpjCg",
"alg": "ECDH-ES+A256KW",
"epk": {
"kty": "EC",
"crv": "P-256",
"x": "6PbSGRsybgGnT0uWu1r6ZyY6gMBTYTmv-SYIjJGYGrw",
"y": "8SniQTY5zS7QolG3gy6SapqPE1ZxI_W43FiPmFoP2R4"
}
}
The following is an example of a JWM Attributes Set (with line breaks
for display purposes only):
{"id":"urn:uuid:ef5a7369-f0b9-4143-a49d-2b9c7ee51117",
"type":"hello-world-message-type",
"from":"urn:uuid:8abdf5fb-621e-4cf5-a595-071bc2c91d82",
"expiry":1516239022,
"time_stamp":1516269022,
"body":{"message": "Hello world!"}}
Encrypting the above plaintext for the recipient yields the following
ciphertext in base64url form.
G61Yg068PU9t9kMzmY9c9w0TR_VV2jopBdb6ncZcC1OvkhhEdvcds0HIt6uv6A6VG2VP_
zerVATrI2_vy5uQlDp6YgULir0RV43LUn8fh5xo
KrV2ZTf8jfNGTTeVIIl5xEd9NRC4CeT8kC6HGc419FwvMAPjractIr6O-
KREscWn4LjRfm-shmQWFWw2FyI0PQdC0ufHgcriDdDwKbI8Leo7nMk E6d9MlXqZT2aLH
9jpY1dI28_8n0Nc9NQBv6c6RCxl5fJkHwQZ_4egRg6kX6OZh1e_JWowejjE5t8
Composing this information into a valid JWE leads to the following
possible expressions
Compact Serialization (with line breaks for display purposes only):
eyJ0eXAiOiJKV00iLCJlbmMiOiJBMjU2R0NNIiwia2lkIjoiUEdvWHpzME5XYVJfbWVLZ
1RaTGJFdURvU1ZUYUZ1eXJiV0k3VjlkcGpDZyIsImFsZyI6I kVDREgtRVMrQTI1NktXI
iwiZXBrIjp7Imt0eSI6IkVDIiwiY3J2IjoiUC0yNTYiLCJ4IjoibzhKbktsdWVFbEtLOX
JiQ2NaS0Zjb0RKNElkNFJZU2VabUpiT nB1Zl9FTSIsInkiOiJ5VXpYdUJHNXhrU0xGdG
dOQ0xxaldDdmgwRFRtZDlHczZkYlJyS1lzamJjIn19
.
nFeVxpB6qASyQORVqOX9o89bYvD0GV-uhAsHpiVmQYmcT513j8uzOw
.
bYeutdVSJGG57heL
.
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G61Yg068PU9t9kMzmY9c9w0TR_VV2jopBdb6ncZcC1OvkhhEdvcds0HIt6uv6A6VG2VP_
zerVATrI2_vy5uQlDp6YgULir0RV43LUn8fh5xoKrV2ZTf8jfNGT
TeVIIl5xEd9NRC4CeT8kC6HGc419FwvMAPjractIr6O-KREscWn4LjRfm-
shmQWFWw2FyI0PQdC0ufHgcriDdDwKbI8Leo7nMkE6d9MlXqZT2aLH9jpY1dI28
_8n0Nc9NQBv6c6RCxl5fJkHwQZ_4egRg6kX6OZh1e_JWowejjE5t8
.
_8MLOQ4SkPksmydaWTCJ9w
JSON Serialization (with line breaks for display purposes only):
{
"protected": "eyJ0eXAiOiJKV00iLCJlbmMiOiJBMjU2R0NNIiwi
a2lkIjoiUEdvWHpzME5XYVJfbWVLZ1RaTGJFdURvU1ZUYUZ1eXJiV0
k3VjlkcGpDZyIsImFsZyI6IkVDREgtRVMrQTI1NktXIiwiZXBrIjp7
Imt0eSI6IkVDIiwiY3J2IjoiUC0yNTYiLCJ4IjoiNlBiU0dSc3liZ0
duVDB1V3UxcjZaeVk2Z01CVFlUbXYtU1lJakpHWUdydyIsInkiOiI4
U25pUVRZNXpTN1FvbEczZ3k2U2FwcVBFMVp4SV9XNDNGaVBtRm9QMl
I0In19",
"recipients": [
{
"encrypted_key": "RU_RpQKd4lglN_Nslxf4OZiUCjah6zeu
wrnrbmmmN5wsBZQfP0LGvg"
}
],
"iv": "aoTg7H1txyzHw0N8",
"ciphertext": "eu9aQQA-s3lmozzZn5viTGszQKtD1l44WG-JtpC
o1-ONQh1aTT5v7BQXbtKNCrNjxCUKWngHeZxe5pSzylDqklUie4S4u
UiVCEkAMcqRlgF8eAWBgDZkeUeoZaViSQ0kdVfhPhzlOSA7kU8gjY1
82Nochaf8rnn6DUTcJqii11E_2eav0y176vWEyYvbHvxiXvCUKEVZV
0VAV3SoVTLwlrCUth6D-975XfBfvl_BlRsYcP0myMs1tOgVSb7nRF0
N2crrCMyc5FC6tdYqLiKZC2K6HBxBp1K-AcVY1Ww",
"tag": "pBF3Dpz3CAWm5CwCMt6rxw"
}
3. JWM Attributes
The JWM Attributes Set represents a JSON object whose members are the
attributes conveyed by the JWM. The Attribute Names within a JWM
Attributes Set MUST be unique; JWM parsers MUST either reject JWMs
with duplicate Attribute 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].
The set of attributes that a JWM must contain to be considered valid
is context dependent and is outside the scope of this specification.
Specific applications of JWMs will require implementations to
understand and process some attributes in particular ways. However,
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in the absence of such requirements, all attributes that are not
understood by implementations MUST be ignored.
There are three classes of JWM Attribute Names: Registered Attribute
Names, Public Attribute Names and Private Attribute Names.
3.1. Registered Attribute Names
The following Attribute Names are registered in the IANA "JSON Web
Message Attributes" registry established by Section 7. None of the
attributes defined below are intended to be mandatory to use or
implement in all cases, but rather they provide a starting point for
a set of useful, interoperable attributes. Applications using JWMs
should define which specific Attributes they use and when they are
required or optional.
3.1.1. "id" Attribute
The "id" attribute is used to define a unique identifier for a JWM.
The "id" attribute value MUST be assigned in a manner that ensures
that there is a negligible probability that the same value will be
accidentally assigned to another JWM. The processing of this
attribute is generally application specific. The "id" attribute
value is a case-sensitive string containing a StringOrURI value. Use
of this attribute is OPTIONAL.
3.1.2. "type" Attribute
The "type" attribute is used to define the type of the message. The
processing of this attribute is generally application specific. The
"type" attribute value is a case-sensitive string containing a
StringOrURI value. The "type" attribute value can be used by
applications to inform the structure and content of the "message
body" and indicate the presence of other JWM attributes. Use of this
attribute is OPTIONAL.
3.1.3. "body" Attribute
The "body" attribute is used to define a location for application
level message content. The "body" attribute value is a JSON object
conforming to RFC 7159 [RFC7159]. The processing of this attribute
is generally application specific. Use of this attribute is
OPTIONAL.
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3.1.4. "to" Attribute
The "to" attribute is used to define the intended recipients of the
JWM. The "to" attribute value is an array of case-sensitive strings
each containing a StringOrURI value. The processing of this
attribute is generally application specific. Use of this attribute
is OPTIONAL.
3.1.5. "from" Attribute
The "from" attribute is used to define the sender of the JWM. The
"from" attribute value is a case-sensitive string containing a
StringOrURI value. The processing of this attribute is generally
application specific. Use of this attribute is OPTIONAL.
3.1.6. "thread_id" Attribute
The "thread_id" attribute is used to associate the JWM to a group of
related messages often referred to as a thread. The "thread_id"
attribute value is a case-sensitive string containing a StringOrURI
value. The processing of this attribute is generally application
specific. Use of this attribute is OPTIONAL.
3.1.7. "referent_id" Attribute
The "referent_id" attribute is used to associated the JWM directly to
another JWM. The "referent_id" attribute value is a case-sensitive
string containing a StringOrURI value. The processing of this
attribute is generally application specific. Use of this attribute
is OPTIONAL.
3.1.8. "time_stamp" Attribute
The "time_stamp" attribute is used to define the time in which the
message was created. The "time_stamp" attributes value MUST be a
number containing a NumericDate value. The processing of this
attribute is generally application specific. Use of this attribute
is OPTIONAL.
3.1.9. "expiry" Attribute
The "expiry" attribute is used to define the lifespan or lifetime of
the JWM. The "expiry" attributes value MUST be a number containing a
NumericDate value. The processing of this attribute is generally
application specific. Use of this attribute is OPTIONAL.
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3.1.10. "reply_url" Attribute
The "reply_url" attribute is used to define a url to which a response
to the message can be sent. The "reply_url" attribute value is a
case-sensitive string containing a StringOrURI value. The processing
of this attribute is generally application specific. Use of this
attribute is OPTIONAL.
3.1.11. "reply_to" Attribute
The "reply_to" attribute is used to define who a response to the
message should be sent to. The "reply_to" attribute value is a case-
sensitive string containing a StringOrURI value OR an array of case-
sensitive strings containing StringOrURI values. The processing of
this attribute is generally application specific. Use of this
attribute is OPTIONAL.
3.2. Public Attribute Names
Attribute Names can be defined at will by those using JWMs. However,
in order to prevent collisions, any new Attribute Name should either
be registered in the IANA "JSON Web Message Attributes" registry
established by Section 7 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 Attribute
Name.
3.3. Private Attribute Names
A producer and consumer of a JWM MAY agree to use Attribute Names
that are Private Names: names that are not Registered Attribute Names
Section 3.1 or Public Attribute Names Section 3.2. Unlike Public
Attribute Names, Private Attribute Names are subject to collision and
should be used with caution.
4. JOSE Header
For a JWM object, the members of the JSON object represented by the
JOSE Header describe the cryptographic operations applied to the JWM
and optionally, additional properties of the JWM. Depending upon
whether the JWM is a JWS or JWE, the corresponding rules for the JOSE
Header values apply.
This specification further specifies the use of the following header
parameters in both the cases where the JWM is a JWS and where it is a
JWE.
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4.1. "typ" (Type) Header Parameter
The "typ" (type) Header Parameter defined by [RFC7515] and [RFC7516]
is used by JWM applications to declare the media type
[IANA.MediaTypes] of this complete JWM. This is intended for use by
the JWM application when values that are not JWMs could also be
present in an application data structure that can contain a JWM
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 it is already known that the object
is a JWM. This parameter is ignored by JWM implementations; any
processing of this parameter is performed by the JWM application. If
present, it is RECOMMENDED that its value be "JWM" to indicate that
this object is a JWM. While media type names are not case sensitive,
it is RECOMMENDED that "JWM" always be spelled using uppercase
characters for compatibility with legacy implementations. Use of
this Header Parameter is OPTIONAL.
4.2. "cty" (Content Type) Header Parameter
The "cty" (content type) Header Parameter defined by [RFC7515] and
[RFC7516] is used by this specification to convey structural
information about the JWM.
In the normal case in which nested signing or encryption operations
are not employed, the use of this Header Parameter is NOT
RECOMMENDED. In the case that nested signing or encryption is
employed, this Header Parameter MUST be present; in this case, the
value MUST be "JWM", to indicate that a Nested JWM is carried in this
JWM. While media type names are not case sensitive, it is
RECOMMENDED that "JWM" always be spelled using uppercase characters
for compatibility with legacy implementations.
4.3. Replicating Attributes as Header Parameters
In some applications using encrypted JWMs, it is useful to have an
unencrypted representation of some attributes. This might be used,
for instance, in application processing rules to determine whether
and how to process the JWM before it is decrypted.
This specification allows Attributes present in the JWM Attributes
Set to be replicated as JOSE Header Parameters in a JWM that is a
JWE, as needed by the application. If such replicated attributes are
present, the application receiving them SHOULD verify that their
values are identical, unless the application defines other specific
processing rules for these attributes. It is the responsibility of
the application to ensure that only attributes that are safe to be
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transmitted in an unencrypted manner are replicated as JOSE Header
Parameter values in the JWM.
5. Creating and Validating JWMs
5.1. Creating a JWM
To create a JWM, the following steps are performed. 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 a JWM Attribute Set containing the desired attributes.
Note that whitespace is explicitly allowed in the representation
and no canonicalization need be performed before encoding.
2. Let the Message be the octets of the UTF-8 representation of the
JWM Attributes Set.
3. Create a JOSE Header containing the desired set of Header
Parameters. The JWM MUST conform to either the JWS [RFC7515] or
JWE [RFC7516] specification. Note that whitespace is explicitly
allowed in the representation and no canonicalization need be
performed before encoding. THE JOSE "typ" header must be set to
"JWM".
4. Depending upon whether the JWM is a JWS or JWE, there are two
cases:
o If the JWM is a JWS, create a JWS using the JWM Attribute Set as
the JWS Payload; all steps specified in JWS [RFC7515] for creating
a JWS MUST be followed. If the resulting JWS features only a
single signature, it can optionally be formated into JWS compact
serialization format allowing the message to be URL safe. If
however, the resulting JWS features multiple signatures and URL
safety for the message is still required, the entire JWS in JSON
serialization format MUST be encoded to base64url format.
Otherwise the output format for the JWS MUST be JWS JSON
serialization format.
o Else, if the JWM is a JWE, create a JWE using the JWM Attribute
Set as the plaintext for the JWE; all steps specified in JWE
[RFC7516] for creating a JWE MUST be followed. If the resulting
JWE features only a single recipient, it can optionally be
formated into JWE compact serialization format allowing the
message to be URL safe. If however, the resulting JWE features
multiple recipients and URL safety for the message is still
required, the entire JWE in JSON serialization format MUST be
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encoded to base64url format. Otherwise the output format for the
JWE MUST be JWE JSON serialization format.
1. If a Nested JWM is desired, let the Message be the JWS or JWE,
and return to Step 3, using a "cty" (content type) value of "JWM"
in the new JOSE Header created in that step.
2. Otherwise, let the resulting JWM be the JWS or JWE.
5.2. Validating a JWM
When validating a JWM, the following steps are performed. 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 fail, then the JWM MUST be rejected; that is,
treated by the application as an invalid input.
1. If the JWM is a valid base64url string containing at least one
period ('.') character.
1. Let the Encoded JOSE Header be the portion of the JWM before
the first period ('.') character.
2. Base64url decode the Encoded JOSE Header following the
restriction that no line breaks, whitespace, or other
additional characters have been used.
3. Verify that the resulting octet sequence is a UTF-8-encoded
representation of a completely valid JSON object conforming
to RFC 7159 [RFC7159]; let the JOSE Header be this JSON
object.
2. Else, if the JWM is a valid base64url string containing no period
('.') characters.
1. Let the Encoded JWS or JWE be the entire base64url string.
2. Base64url decode the Encoded JWS or JWE following the
restriction that no line breaks, whitespace, or other
additional characters have been used.
3. Verify that the resulting octet sequence is a UTF-8-encoded
representation of a completely valid JSON object conforming
to RFC 7159 [RFC7159]; let the JWS or JWE be this JSON
object.
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3. Else, if the JWM is a UTF-8-encoded representation of a
completely valid JSON object conforming to RFC 7159 [RFC7159];
let the JWS or JWE be this JSON object.
4. Verify that the resulting JOSE Header includes only parameters
and values whose syntax and semantics are both understood and
supported or that are specified as being ignored when not
understood.
5. Determine whether the JWM is a JWS or a JWE using any of the
methods described in Section 9 of [RFC7516].
6. Depending upon whether the JWM is a JWS or JWE, there are two
cases:
* If the JWM is a JWS, follow the steps specified in [RFC7515]
for validating a JWS. Let the Message be the result of
base64url decoding the JWS Payload.
* Else, if the JWM is a JWE, follow the steps specified in
[RFC7516] for validating a JWE. Let the Message be the
resulting plaintext.
7. If the JOSE Header contains a "cty" (content type) value of
"JWM", then the Message is a JWM that was the subject of nested
signing or encryption operations. In this case, return to Step
1, using the Message as the JWM.
8. Otherwise, base64url decode the Message following the restriction
that no line breaks, whitespace, or other additional characters
have been used.
9. Verify that the resulting octet sequence is a UTF-8-encoded
representation of a completely valid JSON object conforming to
RFC 7159 [RFC7159]; let the JWM Attributes Set be this JSON
object.
Finally, note that it is an application decision which algorithms may
be used in a given context. Even if a JWM can be successfully
validated, unless the algorithms used in the JWM are acceptable to
the application, it SHOULD reject the JWM.
5.3. String Comparison Rules
These rules are identical to those applied to JWTs outlined in
Section 7.3 of [RFC7519].
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6. Implementation Requirements
This section defines which algorithms and features of this
specification are mandatory to implement. Applications using this
specification can impose additional requirements upon implementations
that they use.
Support for digitally signed JWMs using JWS is REQUIRED. Of the
signature and MAC algorithms specified in JSON Web Algorithms
[RFC7518], only ECDSA using the P-256 curve and SHA-256 hash
algorithm ("ES256") MUST be implemented by conforming JWM
implementations. It is RECOMMENDED that implementations also support
ECDSA using the P-521 curve and the SHA-512 hash algorithm ("ES512")
and EdDSA using the Ed25519 curve and SHA-512 hash algorithm.
Support for other algorithms and key sizes is OPTIONAL.
Support for encrypted JWMs using JWE is also REQUIRED. Of the
encryption algorithms specified in [RFC7518], using Elliptic Curve
Diffie-Hellman Ephemeral Static (ECDH-ES) to agree upon a key and
using this key to to perform key wrapping of a Content Encryption Key
("ECDH-ES+A128KW" and "ECDH-ES+A256KW") MUST be supported. With
regards to content encryption, AES in Galois/Counter Mode (GCM) with
128-bit and 256-bit keys ("A128GCM" and "A256GCM") MUST also be
supported.
Usage of the "none" algorithm identifier in a JWM as defined in the
JOSE Web Algorithms section 3.6 [RFC7518] MUST be considered invalid.
Support for Nested JWMs is also REQUIRED.
7. IANA Considerations
7.1. Registration Template
7.1.1. Attribute Name:
The name requested (e.g., "type"). Because a core goal of this
specification is for the resulting representations to be compact, it
is RECOMMENDED that the name be short - that is, 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 Experts state that there is
a compelling reason to allow an exception.
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7.1.2. Attribute Description
Brief description of the attribute (e.g., "Message Type").
7.1.3. Change Controller
For Standards Track RFCs, list the "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.
7.1.4. Specification Document(s)
Reference to the document or documents that specify the parameter,
preferably including URIs that can be used to retrieve copies of the
documents. An indication of the relevant sections may also be
included but is not required.
7.1.5. Initial Registry Contents
o Attribute Name: "id"
o Attribute Description: Message ID
o Change Controller:
o Specification Document(s):
o Attribute Name: "type"
o Attribute Description: Message Type
o Change Controller:
o Specification Document(s):
o Attribute Name: "body"
o Attribute Description: Message Body
o Change Controller:
o Specification Document(s):
o Attribute Name: "to"
o Attribute Description: Message Recipients
o Change Controller:
o Specification Document(s):
o Attribute Name: "from"
o Attribute Description: Message From
o Change Controller:
o Specification Document(s):
o Attribute Name: "thread_id"
o Attribute Description: Message Thread ID
o Change Controller:
o Specification Document(s):
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o Attribute Name: "referent_id"
o Attribute Description: Message Referent ID
o Change Controller:
o Specification Document(s):
o Attribute Name: "time_stamp"
o Attribute Description: Message Timestamp
o Change Controller:
o Specification Document(s):
o Attribute Name: "expiry"
o Attribute Description: Message Expiry
o Change Controller:
o Specification Document(s):
o Attribute Name: "reply_url"
o Attribute Description: Message Reply URL
o Change Controller:
o Specification Document(s):
o Attribute Name: "reply_to"
o Attribute Description: Message Reply To
o Change Controller:
o Specification Document(s):
8. Media Type Registration
8.1. Registry Contents
9. Security Considerations
All of the security issues that are pertinent to any cryptographic
application must be addressed by JWM/JWS/JWE/JWK agents. Among these
issues are protecting the user's asymmetric private and symmetric
secret keys and employing countermeasures to various attacks.
All the security considerations in the JWS specification also apply
to JWM, as do the JWE security considerations when encryption is
employed. In particular, Sections 10.12 ("JSON Security
Considerations") and 10.13 ("Unicode Comparison Security
Considerations") of [RFC7515] apply equally to the JWM Attributes Set
in the same manner that they do to the JOSE Header.
9.1. Trust Decisions
The contents of a JWM cannot be relied upon in a trust decision
unless its contents have been cryptographically secured and bound to
the context necessary for the trust decision. In particular, the
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key(s) used to sign and/or encrypt the JWM will typically need to
verifiably be under the control of the party identified by the
associated cryptographic operation.
9.2. Signing and Encryption Order
While syntactically the signing and encryption operations for Nested
JWMs may be applied in any order, if both signing and encryption are
necessary, normally producers should sign the message and then
encrypt the result (thus encrypting the signature). This prevents
attacks in which the signature is stripped, leaving just an encrypted
message, as well as providing privacy for the signer. Furthermore,
signatures over encrypted text are not considered valid in many
jurisdictions.
Note that potential concerns about security issues related to the
order of signing and encryption operations are already addressed by
the underlying JWS and JWE specifications; in particular, because JWE
only supports the use of authenticated encryption algorithms,
cryptographic concerns about the potential need to sign after
encryption that apply in many contexts do not apply to this
specification.
10. Privacy Considerations
A JWM may contain privacy-sensitive information. When this is the
case, measures MUST be taken to prevent disclosure of this
information to unintended parties. One way to achieve this is to use
an encrypted JWM and authenticate the recipient. Another way is to
ensure that JWMs containing unencrypted privacy-sensitive information
are only transmitted using protocols utilizing encryption that
support endpoint authentication, such as Transport Layer Security
(TLS). Omitting privacy-sensitive information from a JWM is the
simplest way of minimizing privacy issues.
11. Acknowledgements
The authors of this specification would like to acknowledge the
following individuals for the significant contribution of ideas and
time spent reviewing this document:
Kyle Den Hartog
12. Normative References
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[ECMAScript]
Ecma International, "ECMAScript Language Specification,
5.1 Edition", ECMA Standard 262, June 2011,
<http://www.ecma-international.org/ecma-262/5.1/ECMA-
262.pdf>.
[IANA.MediaTypes]
IANA, "Media Types",
<http://www.iana.org/assignments/media-types>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data
Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March
2014, <https://www.rfc-editor.org/info/rfc7159>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7516] Jones, M. and J. Hildebrand, "JSON Web Encryption (JWE)",
RFC 7516, DOI 10.17487/RFC7516, May 2015,
<https://www.rfc-editor.org/info/rfc7516>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
Author's Address
Tobias Looker (editor)
Mattr
Email: tobias.looker@mattr.global
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