draft-ietf-oauth-proof-of-possession-05.txt		draft-ietf-oauth-proof-of-possession-06.txt
	OAuth Working Group M. Jones		OAuth Working Group M. Jones
	Internet-Draft Microsoft		Internet-Draft Microsoft
	Intended status: Standards Track J. Bradley		Intended status: Standards Track J. Bradley
	Expires: April 21, 2016 Ping Identity		Expires: May 7, 2016 Ping Identity
	H. Tschofenig		H. Tschofenig
	ARM Limited		ARM Limited
	October 19, 2015		November 4, 2015
	Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)		Proof-of-Possession Key Semantics for JSON Web Tokens (JWTs)
	draft-ietf-oauth-proof-of-possession-05		draft-ietf-oauth-proof-of-possession-06
	Abstract		Abstract
	This specification defines how to express a declaration in a JSON Web		This specification defines how to express a declaration in a JSON Web
	Token (JWT) that the presenter of the JWT possesses a particular key		Token (JWT) that the presenter of the JWT possesses a particular key
	and that the recipient can cryptographically confirm proof-of-		and that the recipient can cryptographically confirm proof-of-
	possession of the key by the presenter. Being able to prove		possession of the key by the presenter. Being able to prove
	possession of a key is also sometimes described as the presenter		possession of a key is also sometimes described as the presenter
	being a holder-of-key.		being a holder-of-key.
	skipping to change at page 1, line 38		skipping to change at page 1, line 38
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
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	This Internet-Draft will expire on April 21, 2016.		This Internet-Draft will expire on May 7, 2016.
	Copyright Notice		Copyright Notice
	Copyright (c) 2015 IETF Trust and the persons identified as the		Copyright (c) 2015 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	described in the Simplified BSD License.		described in the Simplified BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
	1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 4		1.1. Notational Conventions . . . . . . . . . . . . . . . . . . 5
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
	3. Representations for Proof-of-Possession Keys . . . . . . . . . 4		3. Representations for Proof-of-Possession Keys . . . . . . . . . 6
	3.1. Confirmation Claim . . . . . . . . . . . . . . . . . . . . 5		3.1. Confirmation Claim . . . . . . . . . . . . . . . . . . . . 6
	3.2. Representation of an Asymmetric Proof-of-Possession Key . 6		3.2. Representation of an Asymmetric Proof-of-Possession Key . 7
	3.3. Representation of an Encrypted Symmetric		3.3. Representation of an Encrypted Symmetric
	Proof-of-Possession Key . . . . . . . . . . . . . . . . . 6		Proof-of-Possession Key . . . . . . . . . . . . . . . . . 7
	3.4. Representation of a Key ID for a Proof-of-Possession		3.4. Representation of a Key ID for a Proof-of-Possession
	Key . . . . . . . . . . . . . . . . . . . . . . . . . . . 7		Key . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
	3.5. Representation of a URL for a Proof-of-Possession Key . . 8		3.5. Representation of a URL for a Proof-of-Possession Key . . 9
	3.6. Specifics Intentionally Not Specified . . . . . . . . . . 8		3.6. Specifics Intentionally Not Specified . . . . . . . . . . 9
	4. Security Considerations . . . . . . . . . . . . . . . . . . . 9		4. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	5. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 10		5. Privacy Considerations . . . . . . . . . . . . . . . . . . . . 11
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10		6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
	6.1. JSON Web Token Claims Registration . . . . . . . . . . . . 11		6.1. JSON Web Token Claims Registration . . . . . . . . . . . . 12
	6.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 11		6.1.1. Registry Contents . . . . . . . . . . . . . . . . . . 12
	6.2. JWT Confirmation Methods Registry . . . . . . . . . . . . 11		6.2. JWT Confirmation Methods Registry . . . . . . . . . . . . 12
	6.2.1. Registration Template . . . . . . . . . . . . . . . . 11		6.2.1. Registration Template . . . . . . . . . . . . . . . . 12
	6.2.2. Initial Registry Contents . . . . . . . . . . . . . . 12		6.2.2. Initial Registry Contents . . . . . . . . . . . . . . 13
	7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12		7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13
	7.1. Normative References . . . . . . . . . . . . . . . . . . . 12		7.1. Normative References . . . . . . . . . . . . . . . . . . . 13
	7.2. Informative References . . . . . . . . . . . . . . . . . . 13		7.2. Informative References . . . . . . . . . . . . . . . . . . 14
	Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 14		Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 15
	Appendix B. Document History . . . . . . . . . . . . . . . . . . 14		Appendix B. Document History . . . . . . . . . . . . . . . . . . 15
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16
	1. Introduction		1. Introduction
	This specification defines how a JSON Web Token (JWT) [JWT] can		This specification defines how a JSON Web Token (JWT) [JWT] can
	declare that the presenter of the JWT possesses a key and that the		declare that the presenter of the JWT possesses a key and that the
	recipient can cryptographically confirm that the presenter possesses		recipient can cryptographically confirm that the presenter possesses
	that key. Proof-of-possession of a key is also sometimes described		that key. Proof-of-possession of a key is also sometimes described
	as the presenter being a holder-of-key. The		as the presenter being a holder-of-key. The
	[I-D.ietf-oauth-pop-architecture] specification describes key		[I-D.ietf-oauth-pop-architecture] specification describes key
	confirmation, among other confirmation mechanisms. This		confirmation, among other confirmation mechanisms. This
	specification defines how to communicate key confirmation key		specification defines how to communicate key confirmation key
	information in JWTs.		information in JWTs.
	Envision the following two use cases. The first use case describes		Envision the following two use cases. The first use case employs a
	the use of a symmetric proof-of-possession key and the second use		symmetric proof-of-possession key and the second use case employs an
	case uses an asymmetric proof-of-possession key.		asymmetric proof-of-possession key.
	An issuer generates a JWT and places an encrypted symmetric key		+--------------+
	inside the newly introduced confirmation claim. This symmetric key		| | +--------------+
	is encrypted with a key known only to the issuer and the recipient.		| |--(4) Presentation of -->| |
	The entire JWT is then integrity protected by the issuer. The JWT is		| | JWT w/ Encrypted | |
	then sent to the presenter. Since the presenter is unable to obtain		| Presenter | PoP Key | |
	the encrypted symmetric key from the JWT itself, the issuer conveys		| | | |
	that symmetric key separately to the presenter. Now, the presenter		| |<-(5) Communication ---->| |
	is in possession of the symmetric key as well as the JWT (which		| | Authenticated by | |
	includes the confirmation claim member). When the presenter needs to		+--------------+ PoP Key | |
	present the JWT to the recipient, it also needs to demonstrate		| ^ | |
	possession of the symmetric key; the presenter, for example, uses the		| | | |
	symmetric key in a challenge/response protocol with the recipient.		(1) Sym. (3) JWT w/ | Recipient |
	The recipient is then able to verify that it is interacting with the		| PoP | Encrypted | |
	genuine presenter by decrypting the JWK contained inside the		| Key | PoP Key | |
			v | | |
			+--------------+ | |
			| | | |
			| | | |
			| |<-(2) Key Exchange for ->| |
			| Issuer | Key Encryption Key | |
			| | | |
			| | | |
			| | +--------------+
			+--------------+
			Figure 1: Proof-of-Possession with a Symmetric Key
			In the case illustrated in Figure 1, the presenter generates a
			symmetric key and (1) privately sends it to the issuer. The issuer
			generates a JWT with an encrypted copy of this symmetric key in the
			newly introduced confirmation claim. This symmetric key is encrypted
			with a key known only to the issuer and the recipient, which is
			established in step (2), if it doesn't already exist. The entire JWT
			is integrity protected by the issuer. The JWT is then (3) sent to
			the presenter. Now, the presenter is in possession of the symmetric
			key as well as the JWT (which includes the confirmation claim). When
			the presenter (4) presents the JWT to the recipient, it also needs to
			demonstrate possession of the symmetric key; the presenter, for
			example, (5) uses the symmetric key in a challenge/response protocol
			with the recipient. The recipient is then able to verify that it is
			interacting with the genuine presenter by decrypting the key in the
	confirmation claim of the JWT. By doing this, the recipient obtains		confirmation claim of the JWT. By doing this, the recipient obtains
	the symmetric key, which it then uses to verify cryptographically		the symmetric key, which it then uses to verify cryptographically
	protected messages exchanged with the presenter. This symmetric key		protected messages exchanged with the presenter (5). This symmetric
	mechanism described above is conceptually similar to the use of		key mechanism described above is conceptually similar to the use of
	Kerberos tickets.		Kerberos tickets.
	In the second case, consider a presenter that generates a public/		+--------------+
	private key pair. It then sends the public key to an issuer, which		| | +--------------+
	creates a JWT and places a public key (or an identifier for it)		| |--(3) Presentation of -->| |
	inside the newly introduced confirmation claim. The entire JWT is		| | JWT w/ Public | |
	integrity protected using a digital signature to protect it against		| Presenter | PoP Key | |
	modifications. The JWT is then sent to the presenter. When the		| | | |
	presenter needs to present the JWT to the recipient, it also needs to		| |<-(4) Communication ---->| |
	demonstrate possession of the private key. The presenter, for		| | Authenticated by | |
	example, uses the private key in a TLS exchange with the recipient or		+--------------+ PoP Key | |
	signs a nonce with the private key. The recipient is able to verify		| ^ | |
	that it is interacting with the genuine presenter by extracting the		| | | |
	public key from the confirmation claim of the JWT (after verifying		(1) Public (2) JWT w/ | Recipient |
	the digital signature of the JWT) and utilizing it with the private		| PoP | Public | |
	key in the TLS exchange or checking the nonce signature.		| Key | PoP Key | |
			v | | |
			+--------------+ | |
			| | | |
			| | | |
			| | | |
			| Issuer | | |
			| | | |
			| | | |
			| | +--------------+
			+--------------+
			Figure 2: Proof-of-Possession with an Asymmetric Key
			In the case illustrated in Figure 2, the presenter generates a
			public/private key pair and (1) sends the public key to the issuer,
			which creates a JWT that contains the public key (or an identifier
			for it) in the newly introduced confirmation claim. The entire JWT
			is integrity protected using a digital signature to protect it
			against modifications. The JWT is then (2) sent to the presenter.
			When the presenter (3) presents the JWT to the recipient, it also
			needs to demonstrate possession of the private key. The presenter,
			for example, (4) uses the private key in a TLS exchange with the
			recipient or (4) signs a nonce with the private key. The recipient
			is able to verify that it is interacting with the genuine presenter
			by extracting the public key from the confirmation claim of the JWT
			(after verifying the digital signature of the JWT) and utilizing it
			with the private key in the TLS exchange or by checking the nonce
			signature.
	In both cases, the JWT may contain other claims that are needed by		In both cases, the JWT may contain other claims that are needed by
	the application.		the application.
	1.1. Notational Conventions		1.1. Notational Conventions
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and		"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
	"OPTIONAL" in this document are to be interpreted as described in RFC		"OPTIONAL" in this document are to be interpreted as described in RFC
	2119 [RFC2119].		2119 [RFC2119].
	skipping to change at page 14, line 22		skipping to change at page 15, line 22
	Appendix A. Acknowledgements		Appendix A. Acknowledgements
	The authors wish to thank Brian Campbell, Kepeng Li, James Manger,		The authors wish to thank Brian Campbell, Kepeng Li, James Manger,
	Justin Richer, and Nat Sakimura for their reviews of the		Justin Richer, and Nat Sakimura for their reviews of the
	specification.		specification.
	Appendix B. Document History		Appendix B. Document History
	[[ to be removed by the RFC Editor before publication as an RFC ]]		[[ to be removed by the RFC Editor before publication as an RFC ]]
			-06
			o Added diagrams to the introduction.
	-05		-05
	o Addressed review comments by Kepeng Li.		o Addressed review comments by Kepeng Li.
	-04		-04
	o Allowed the use of "jwk" for symmetric keys when the JWT is		o Allowed the use of "jwk" for symmetric keys when the JWT is
	encrypted.		encrypted.
	o Added the "jku" (JWK Set URL) member.		o Added the "jku" (JWK Set URL) member.
End of changes. 12 change blocks.
	60 lines changed or deleted		120 lines changed or added
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