< draft-ietf-kitten-sasl-oauth-09.txt		draft-ietf-kitten-sasl-oauth-10.txt >
	KITTEN W. Mills		KITTEN W. Mills
	Internet-Draft Yahoo! Inc.		Internet-Draft Yahoo! Inc.
	Intended status: Standards Track T. Showalter		Intended status: Standards Track T. Showalter
	Expires: June 20, 2013		Expires: August 28, 2013
	H. Tschofenig		H. Tschofenig
	Nokia Siemens Networks		Nokia Siemens Networks
	December 17, 2012		February 24, 2013
	A set of SASL and GSS-API Mechanisms for OAuth		A set of SASL and GSS-API Mechanisms for OAuth
	draft-ietf-kitten-sasl-oauth-09		draft-ietf-kitten-sasl-oauth-10.txt
	Abstract		Abstract
	OAuth enables a third-party application to obtain limited access to a		OAuth enables a third-party application to obtain limited access to a
	protected resource, either on behalf of a resource owner by		protected resource, either on behalf of a resource owner by
	orchestrating an approval interaction, or by allowing the third-party		orchestrating an approval interaction, or by allowing the third-party
	application to obtain access on its own behalf.		application to obtain access on its own behalf.
	This document defines how an application client uses credentials		This document defines how an application client uses credentials
	obtained via OAuth over the Simple Authentication and Security Layer		obtained via OAuth over the Simple Authentication and Security Layer
	skipping to change at page 2, line 4 ¶		skipping to change at page 2, line 4 ¶
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at http://datatracker.ietf.org/drafts/current/.		Drafts is at http://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on June 20, 2013.		This Internet-Draft will expire on August 28, 2013.
	Copyright Notice		Copyright Notice
	Copyright (c) 2012 IETF Trust and the persons identified as the		Copyright (c) 2013 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
	skipping to change at page 3, line 17 ¶		skipping to change at page 3, line 17 ¶
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
	2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7		2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 7
	3. OAuth SASL Mechanism Specifications . . . . . . . . . . . . . 8		3. OAuth SASL Mechanism Specifications . . . . . . . . . . . . . 8
	3.1. Initial Client Response . . . . . . . . . . . . . . . . . 9		3.1. Initial Client Response . . . . . . . . . . . . . . . . . 9
	3.1.1. Reserved Key/Values . . . . . . . . . . . . . . . . . 10		3.1.1. Reserved Key/Values . . . . . . . . . . . . . . . . . 10
	3.1.2. Use of the gs2-header . . . . . . . . . . . . . . . . 10		3.1.2. Use of the gs2-header . . . . . . . . . . . . . . . . 10
	3.2. Server's Response . . . . . . . . . . . . . . . . . . . . 10		3.2. Server's Response . . . . . . . . . . . . . . . . . . . . 10
	3.2.1. OAuth Identifiers in the SASL Context . . . . . . . . 11		3.2.1. OAuth Identifiers in the SASL Context . . . . . . . . 11
	3.2.2. Server Response to Failed Authentication . . . . . . . 11		3.2.2. Server Response to Failed Authentication . . . . . . . 11
	3.2.3. Completing an Error Message Sequence . . . . . . . . . 12		3.2.3. Completing an Error Message Sequence . . . . . . . . . 12
	3.3. OAuth Access Token Types using Digital Signatures and		3.3. OAuth Access Token Types using Keyed Message Digests . . . 12
	Keyed Message Digests . . . . . . . . . . . . . . . . . . 12
	3.4. Channel Binding . . . . . . . . . . . . . . . . . . . . . 13		3.4. Channel Binding . . . . . . . . . . . . . . . . . . . . . 13
	4. GSS-API OAuth Mechanism Specification . . . . . . . . . . . . 14		4. GSS-API OAuth Mechanism Specification . . . . . . . . . . . . 14
	5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 16		5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
	5.1. Successful Bearer Token Exchange . . . . . . . . . . . . . 16		5.1. Successful Bearer Token Exchange . . . . . . . . . . . . . 16
	5.2. OAuth 1.0a Authorization with Channel Binding . . . . . . 17		5.2. OAuth 1.0a Authorization with Channel Binding . . . . . . 17
	5.3. Failed Exchange . . . . . . . . . . . . . . . . . . . . . 18		5.3. Failed Exchange . . . . . . . . . . . . . . . . . . . . . 18
	5.4. Failed Channel Binding . . . . . . . . . . . . . . . . . . 19		5.4. Failed Channel Binding . . . . . . . . . . . . . . . . . . 19
	5.5. SMTP Example of a Failed Negotiation . . . . . . . . . . . 19		5.5. SMTP Example of a Failed Negotiation . . . . . . . . . . . 19
	6. Security Considerations . . . . . . . . . . . . . . . . . . . 21		6. Security Considerations . . . . . . . . . . . . . . . . . . . 21
	7. Internationalization Considerations . . . . . . . . . . . . . 22		7. Internationalization Considerations . . . . . . . . . . . . . 22
	8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23		8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23
	8.1. SASL Registration . . . . . . . . . . . . . . . . . . . . 23		8.1. SASL Registration . . . . . . . . . . . . . . . . . . . . 23
	8.2. GSS-API Registration . . . . . . . . . . . . . . . . . . . 24		8.2. GSS-API Registration . . . . . . . . . . . . . . . . . . . 24
	9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25		9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 25
	9.1. Normative References . . . . . . . . . . . . . . . . . . . 25		9.1. Normative References . . . . . . . . . . . . . . . . . . . 25
	9.2. Informative References . . . . . . . . . . . . . . . . . . 26		9.2. Informative References . . . . . . . . . . . . . . . . . . 26
	Appendix A. Acknowlegements . . . . . . . . . . . . . . . . . . . 28		Appendix A. Acknowlegements . . . . . . . . . . . . . . . . . . . 28
	Appendix B. Document History . . . . . . . . . . . . . . . . . . 29		Appendix B. Document History . . . . . . . . . . . . . . . . . . 29
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 31		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 32
	1. Introduction		1. Introduction
	OAuth [RFC6749] enables a third-party application to obtain limited		OAuth 1.0a [RFC5849] and OAuth 2.0 [RFC6749] are protocol frameworks
	access to a protected resource, either on behalf of a resource owner		that enable a third-party application to obtain limited access to a
	by orchestrating an approval interaction, or by allowing the third-		protected resource, either on behalf of a resource owner by
	party application to obtain access on its own behalf. The core OAuth		orchestrating an approval interaction, or by allowing the third-party
	2.0 specification [RFC6749] does not define the interaction between		application to obtain access on its own behalf.
	the client and the resource server with the access to a protected
	resource using an Access Token. This functionality is described in
	separate specifications, for example bearer tokens [RFC6750], OAuth
	2.0 MAC tokens [I-D.ietf-oauth-v2-http-mac]. OAuth 1.0a [RFC5849],
	the predecessor of OAuth 2.0, has a similar design. The main use
	cases for OAuth 2.0 and OAuth 1.0 have so far focused on an HTTP-
	based environment only.
	Figure 1 shows the abstract message flow as shown in Figure 1 of		The core OAuth 2.0 specification [RFC6749] does not define the
	OAuth 2.0 [RFC6749].		interaction between the OAuth client and the resource server for the
			access to a protected resource using an Access Token. Instead, this
			functionality is described in separate specifications, such as the
			bearer token specification [RFC6750]. OAuth 1.0a included the
			communication between the OAuth client and the resource server in
			[RFC5849].
	+--------+ +---------------+		The main use cases for OAuth 2.0 and OAuth 1.0a have so far focused
	| |--(A)- Authorization Request ->| Resource |		on an HTTP-based environment only. This document integrates OAuth
	| | | Owner |		1.0a and OAuth 2.0 into non-HTTP-based applications using the
	| |<-(B)-- Authorization Grant ---| |		integration into SASL and the GSS-API. Hence, this document takes
	| | +---------------+		advantage of the OAuth protocol and its deployment base to provide a
	| |		way to use SASL [RFC4422] and the GSS-API [RFC2743] to gain access to
	| | +---------------+		resources when using non-HTTP-based protocols, such as the Internet
	| |--(C)-- Authorization Grant -->| Authorization |		Message Access Protocol (IMAP) [RFC3501] and SMTP [RFC5321], which is
	| Client | | Server |		what this memo uses in the examples.
	| |<-(D)----- Access Token -------| |
	| | +---------------+
	| |
	| | +---------------+
	| |--(E)----- Access Token ------>| Resource |
	| | | Server |
	| |<-(F)--- Protected Resource ---| |
	+--------+ +---------------+
	Figure 1: Abstract OAuth 2.0 Protocol Flow		To illustrate the impact of integrating this specification into an
			OAuth-enabled application environment Figure 1 shows the abstract
			message flow of OAuth 2.0 [RFC6749]. As indicated in the figure,
			this document impacts the exchange of messages (E) and (F) since SASL
			or the GSS-API is used for interaction between the client and the
			resource server instead of HTTP.
	This document takes advantage of the OAuth protocol and its		----+
	deployment base to provide a way to use SASL [RFC4422] as well as the		+--------+ +---------------+ |
	GSS-API [RFC2743] to gain access to resources when using non-HTTP-		| |--(A)-- Authorization Request --->| Resource | |
	based protocols, such as the Internet Message Access Protocol (IMAP)		| | | Owner | |Plain
	[RFC3501] and SMTP [RFC5321], which is what this memo uses in the		| |<-(B)------ Access Grant ---------| | |OAuth
	examples.		| | +---------------+ |2.0
			| | |
			| | Client Credentials & +---------------+ |
			| |--(C)------ Access Grant -------->| Authorization | |
			| Client | | Server | |
			| |<-(D)------ Access Token ---------| | |
			| | (w/ Optional Refresh Token) +---------------+ |
			| | ----+
			| | ----+
			| | +---------------+ |
			| | | | |OAuth
			| |--(E)------ Access Token -------->| Resource | |over
			| | | Server | |SASL/
			| |<-(F)---- Protected Resource -----| | |GSS-
			| | | | |API
			+--------+ +---------------+ |
			----+
			Figure 1: OAuth 2.0 Protocol Flow
	The Simple Authentication and Security Layer (SASL) is a framework		The Simple Authentication and Security Layer (SASL) is a framework
	for providing authentication and data security services in		for providing authentication and data security services in
	connection-oriented protocols via replaceable mechanisms. It		connection-oriented protocols via replaceable mechanisms. It
	provides a structured interface between protocols and mechanisms.		provides a structured interface between protocols and mechanisms.
	The resulting framework allows new protocols to reuse existing		The resulting framework allows new protocols to reuse existing
	mechanisms and allows old protocols to make use of new mechanisms.		mechanisms and allows old protocols to make use of new mechanisms.
	The framework also provides a protocol for securing subsequent		The framework also provides a protocol for securing subsequent
	protocol exchanges within a data security layer.		protocol exchanges within a data security layer.
	skipping to change at page 6, line 5 ¶		skipping to change at page 6, line 33 ¶
	(D) The authorization server authenticates the client and		(D) The authorization server authenticates the client and
	validates the authorization grant, and if valid issues an access		validates the authorization grant, and if valid issues an access
	token.		token.
	(E) The client requests the protected resource from the resource		(E) The client requests the protected resource from the resource
	server and authenticates by presenting the access token.		server and authenticates by presenting the access token.
	(F) The resource server validates the access token, and if valid,		(F) The resource server validates the access token, and if valid,
	indicates a successful authentication.		indicates a successful authentication.
	Steps (E) and (F) are not defined in [RFC6749] and are the main		Again, steps (E) and (F) are not defined in [RFC6749] (but are
	functionality specified within this document. Consequently, the		described in [RFC6750] instead) and are the main functionality
	message exchange shown in Figure 2 is the result of this		specified within this document. Consequently, the message exchange
	specification. The client will generally need to determine the		shown in Figure 1 is the result of this specification. The client
	authentication endpoints (and perhaps the service endpoints) before		will generally need to determine the authentication endpoints (and
	the OAuth 2.0 protocol exchange messages in steps (A)-(D) are		perhaps the service endpoints) before the OAuth 2.0 protocol exchange
	executed. The discovery of the resource owner and authorization		messages in steps (A)-(D) are executed. The discovery of the
	server endpoints is outside the scope of this specification. The		resource owner and authorization server endpoints is outside the
	client must discover those endpoints using a discovery mechanisms		scope of this specification. The client must discover those
	such as Webfinger using host-meta [I-D.ietf-appsawg-webfinger]. In		endpoints using a discovery mechanisms, such as Webfinger using host-
	band discovery is not tenable if clients support the OAuth 2.0		meta [I-D.ietf-appsawg-webfinger]. In band discovery is not tenable
	password grant. Once credentials are obtained the client proceeds to		if clients support the OAuth 2.0 password grant. Once credentials
	steps (E) and (F) defined in this specification.		are obtained the client proceeds to steps (E) and (F) defined in this
			specification.
	----+
	+--------+ +---------------+ |
	| |--(A)-- Authorization Request --->| Resource | |
	| | | Owner | |Plain
	| |<-(B)------ Access Grant ---------| | |OAuth
	| | +---------------+ |2.0
	| | |
	| | Client Credentials & +---------------+ |
	| |--(C)------ Access Grant -------->| Authorization | |
	| Client | | Server | |
	| |<-(D)------ Access Token ---------| | |
	| | (w/ Optional Refresh Token) +---------------+ |
	| | ----+
	| | ----+
	| | +---------------+ |
	| | | | |OAuth
	| |--(E)------ Access Token -------->| Resource | |over
	| | | Server | |SASL/
	| |<-(F)---- Protected Resource -----| | |GSS-
	| | | | |API
	+--------+ +---------------+ |
	----+
	Figure 2: OAuth SASL Architecture		OAuth 1.0 follows a similar model but uses a different terminology
			and does not separate the resource server from the authorization
			server.
	2. Terminology		2. Terminology
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in [RFC2119].		document are to be interpreted as described in [RFC2119].
	The reader is assumed to be familiar with the terms used in the OAuth		The reader is assumed to be familiar with the terms used in the OAuth
	2.0 specification [RFC6749].		2.0 specification [RFC6749].
	skipping to change at page 8, line 11 ¶		skipping to change at page 8, line 11 ¶
	Note that the IMAP SASL specification requires base64 encoding, see		Note that the IMAP SASL specification requires base64 encoding, see
	Section 4 of [RFC4648], not this memo.		Section 4 of [RFC4648], not this memo.
	3. OAuth SASL Mechanism Specifications		3. OAuth SASL Mechanism Specifications
	SASL is used as an authentication framework in a variety of		SASL is used as an authentication framework in a variety of
	application layer protocols. This document defines the following		application layer protocols. This document defines the following
	SASL mechanisms for usage with OAuth:		SASL mechanisms for usage with OAuth:
	OAUTHBEARER: Authorization using OAuth 2.0 bearer tokens as		OAUTHBEARER: OAuth 2.0 bearer tokens, as described in [RFC6750].
	described in [RFC6750].		RFC 6750 uses Transport Layer Security (TLS) to secure the
			protocol interaction between the client and the resource
			server.
	OAUTH10A: Authorization using OAuth 1.0a MAC tokens (using the		OAUTH10A: OAuth 1.0a MAC tokens (using the HMAC-SHA1 keyed
	HMAC-SHA1 keyed message digest) as described in Section 3.4.2		message digest), as described in Section 3.4.2 of [RFC5849].
	of [RFC5849].
	OAUTH10A-PLUS: Adds channel binding [RFC5056] capability to		OAUTH10A-PLUS: Adds channel binding [RFC5056] capability to
	OAUTH10A for protection against man-in-the-middle attacks.		OAUTH10A for protection against man-in-the-middle attacks.
			OAUTH10A-PLUS mandates the usage of Transport Layer Security
			(TLS).
	New extensions may be defined to add additional OAuth Access Token		New extensions may be defined to add additional OAuth Access Token
	Types. Such a new SASL OAuth mechanism can be added by simply		Types. Such a new SASL OAuth mechanism can be added by simply
	registering the new name(s) and citing this specification for the		registering the new name(s) and citing this specification for the
	further definition. New channel binding enabled "-PLUS" mechanisms		further definition. New channel binding enabled "-PLUS" mechanisms
	defined in this way MUST include message integrity protection. A		defined in this way MUST include message integrity protection. A
	newly defined mechanism would also need to register a new GS2 OID.		newly defined mechanism would also need to register a new GS2 OID.
	These mechanisms are client initiated and lock-step, the server		These mechanisms are client initiated and lock-step, the server
	always replying to a client message. In the case where the client		always replying to a client message. In the case where the client
	skipping to change at page 9, line 41 ¶		skipping to change at page 9, line 43 ¶
	port: Contains the port number represented as a decimal positive		port: Contains the port number represented as a decimal positive
	integer string without leading zeros to which the client		integer string without leading zeros to which the client
	connected.		connected.
	qs: The HTTP query string. In non-channel binding mechanisms		qs: The HTTP query string. In non-channel binding mechanisms
	this is reserved, the client SHOUD NOT send it, and has the		this is reserved, the client SHOUD NOT send it, and has the
	default value of "". In "-PLUS" variants this carries a single		default value of "". In "-PLUS" variants this carries a single
	key value pair "cbdata" for the channel binding data payload		key value pair "cbdata" for the channel binding data payload
	formatted as an HTTP query string.		formatted as an HTTP query string.
	For OAuth Access Token Types that use digital signatures or keyed		For OAuth token types that use keyed message digests the client MUST
	message digests the client MUST send host and port number key/values,		send host and port number key/values, and the server MUST fail an
	and the server MUST fail an authorization request requiring		authorization request requiring keyed message digests that do not
	signatures or keyed message digests that do not have host and port		have host and port values. In OAuth 1.0a for example, the so-called
	values. For authorization schemes that require a URI scheme as part		"signature base string calculation" includes the reconstructed HTTP
	of the data being signed "http" is always used. In OAuth 1.0a for		URL.
	example, the so-called signature base string calculation includes the
	reconstructed HTTP URL.
	3.1.1. Reserved Key/Values		3.1.1. Reserved Key/Values
	In these mechanisms values for path, query string and post body are		In these mechanisms values for path, query string and post body are
	assigned default values. OAuth authorization schemes MAY define		assigned default values. OAuth authorization schemes MAY define
	usage of these in the SASL context and extend this specification.		usage of these in the SASL context and extend this specification.
	For OAuth Access Token Types that use request signatures the default		For OAuth Access Token Types that use request keyed message digest
	values MUST be used unless explicit values are provided in the client		the default values MUST be used unless explicit values are provided
	response. The following key values are reserved for future use:		in the client response. The following key values are reserved for
			future use:
	mthd (RESERVED): HTTP method for use in signatures, the default		mthd (RESERVED): HTTP method, the default value is "POST".
	value is "POST".
	path (RESERVED): HTTP path data, the default value is "/".		path (RESERVED): HTTP path data, the default value is "/".
	post (RESERVED): HTTP post data, the default value is "".		post (RESERVED): HTTP post data, the default value is "".
	3.1.2. Use of the gs2-header		3.1.2. Use of the gs2-header
	The OAuth scheme related mechanisms are also GSS-API mechanisms, see		The OAuth scheme related mechanisms are also GSS-API mechanisms, see
	Section 4 for further detail. The gs2-header is used as follows:		Section 4 for further detail. The gs2-header is used as follows:
	skipping to change at page 10, line 43 ¶		skipping to change at page 10, line 43 ¶
	In the non "-PLUS" mechanisms the "gs2-cb-flag" MUST be set to "n"		In the non "-PLUS" mechanisms the "gs2-cb-flag" MUST be set to "n"
	because channel-binding [RFC5056] data is not expected. In the		because channel-binding [RFC5056] data is not expected. In the
	OAUTH10A-PLUS mechanism (or other -PLUS variants based on this		OAUTH10A-PLUS mechanism (or other -PLUS variants based on this
	specification) the "gs2-cb-flag" MUST be set appropriately by the		specification) the "gs2-cb-flag" MUST be set appropriately by the
	client.		client.
	3.2. Server's Response		3.2. Server's Response
	The server validates the response per the specification for the OAuth		The server validates the response per the specification for the OAuth
	Access Token Types used. If the OAuth Access Token Type utilizes a		Access Token Types used. If the OAuth Access Token Type utilizes a
	digital signature or a keyed message digest of the request parameters		keyed message digest of the request parameters then the client must
	then the client must provide a client response that satisfies the		provide a client response that satisfies the data requirements for
	data requirements for the scheme in use.		the scheme in use.
	In a "-PLUS" mechanism the server examines the channel binding data,		In a "-PLUS" mechanism the server examines the channel binding data,
	extracts the channel binding unique prefix, and extracts the raw		extracts the channel binding unique prefix, and extracts the raw
	channel biding data based on the channel binding type used. It then		channel biding data based on the channel binding type used. It then
	computes it's own copy of the channel binding payload and compares		computes it's own copy of the channel binding payload and compares
	that to the payload sent by the client in the cbdata key/value.		that to the payload sent by the client in the cbdata key/value.
	Those two must be equal for channel binding to succeed.		Those two must be equal for channel binding to succeed.
	The server responds to a successfully verified client message by		The server responds to a successfully verified client message by
	completing the SASL negotiation. The authenticated identity reported		completing the SASL negotiation. The authenticated identity reported
	by the SASL mechanism is the identity securely established for the		by the SASL mechanism is the identity securely established for the
	client with the OAuth credential. The application, not the SASL		client with the OAuth credential. The application, not the SASL
	mechanism, based on local access policy determines whether the		mechanism, based on local access policy determines whether the
	identity reported by the mechanism is allowed access to the requested		identity reported by the mechanism is allowed access to the requested
	resource. Note that the semantics of the authz-id is specified by		resource. Note that the semantics of the authz-id is specified by
	the SASL framework [RFC4422].		the SASL framework [RFC4422].
	3.2.1. OAuth Identifiers in the SASL Context		3.2.1. OAuth Identifiers in the SASL Context
	OAuth access tokens may carry the authenticated identifier of the		In the OAuth framework the client may be authenticated by the
	resource owner and client authentication provides the authenticated		authorization server and the resource owner is authenticated to the
	identity of the client issuing the request to the resource server.		authorization server. OAuth access tokens may contain information
			about the authentication of the resource owner and about the client
			and may therefore make this information accessible to the resource
			server.
	If both identities are needed by an application the developer will		If both identifiers are needed by an application the developer will
	need to provide a way to communicate that from the SASL mechanism		need to provide a way to communicate that from the SASL mechanism
	back to the application such as a GSS-API [RFC2743] named type like		back to the application, such as a GSS-API [RFC2743] named type like
	GSS_C_NT_USER_NAME or a comparable newly defined GSS-API name type or		GSS_C_NT_USER_NAME or a comparable newly defined GSS-API name type or
	name attribute [RFC6680].		name attribute [RFC6680].
	3.2.2. Server Response to Failed Authentication		3.2.2. Server Response to Failed Authentication
	For a failed authentication the server returns a JSON [RFC4627]		For a failed authentication the server returns a JSON [RFC4627]
	formatted error result, and fails the authentication. The error		formatted error result, and fails the authentication. The error
	result consists of the following values:		result consists of the following values:
	status (REQUIRED): The authorization error code. Valid error		status (REQUIRED): The authorization error code. Valid error
	skipping to change at page 12, line 17 ¶		skipping to change at page 12, line 20 ¶
	3.2.3. Completing an Error Message Sequence		3.2.3. Completing an Error Message Sequence
	Section 3.6 of [RFC4422] explicitly prohibits additional information		Section 3.6 of [RFC4422] explicitly prohibits additional information
	in an unsuccessful authentication outcome. Therefore, the error		in an unsuccessful authentication outcome. Therefore, the error
	message is sent in a normal message. The client MUST then send an		message is sent in a normal message. The client MUST then send an
	additional client response consisting of a single %x01 (control A)		additional client response consisting of a single %x01 (control A)
	character to the server in order to allow the server to finish the		character to the server in order to allow the server to finish the
	exchange.		exchange.
	3.3. OAuth Access Token Types using Digital Signatures and Keyed		3.3. OAuth Access Token Types using Keyed Message Digests
	Message Digests
	OAuth Access Token Types may use digital signatures or keyed message		OAuth Access Token Types may use keyed message digests and the client
	digests. The client and the resource server need to perform a		and the resource server may need to perform a cryptographic
	cryptographic computation for integrity protection and data origin		computation for integrity protection and data origin authentication.
	authentication.
	OAuth is designed for access to resources identified by URIs. SASL		OAuth is designed for access to resources identified by URIs. SASL
	is designed for user authentication, and has no facility for more		is designed for user authentication, and has no facility for more
	fine-grained access control. In this specification we require or		fine-grained access control. In this specification we require or
	define default values for the data elements from an HTTP request		define default values for the data elements from an HTTP request
	which allow the signature base string to be constructed properly.		which allow the signature base string to be constructed properly.
	The default HTTP path is "/" and the default post body is empty.		The default HTTP path is "/" and the default post body is empty.
	These atoms are defined as extension points so that no changes are		These atoms are defined as extension points so that no changes are
	needed if there is a revision of SASL which supports more specific		needed if there is a revision of SASL which supports more specific
	resource authorization, e.g., IMAP access to a specific folder or FTP		resource authorization, e.g., IMAP access to a specific folder or FTP
	skipping to change at page 13, line 33 ¶		skipping to change at page 13, line 33 ¶
	A1%26oauth_timestamp%3D137131201%26oauth_token%3Dkkk9d7dh3k39sjv7		A1%26oauth_timestamp%3D137131201%26oauth_token%3Dkkk9d7dh3k39sjv7
	3.4. Channel Binding		3.4. Channel Binding
	The channel binding data is carried in the "qs" (query string) key		The channel binding data is carried in the "qs" (query string) key
	value pair formatted as a standard HTTP query parameter with the name		value pair formatted as a standard HTTP query parameter with the name
	"cbdata". Channel binding requires that the channel binding data be		"cbdata". Channel binding requires that the channel binding data be
	integrity protected end-to-end in order to protect against man-in-		integrity protected end-to-end in order to protect against man-in-
	the-middle attacks. All SASL OAuth mechanisms with a "-PLUS" postfix		the-middle attacks. All SASL OAuth mechanisms with a "-PLUS" postfix
	MUST provide integrity protection. It should be noted that while the		MUST provide integrity protection. It should be noted that while the
	Bearer Access Token Type mandates TLS it does not create keying		OAuth 2.0 Bearer Token mandates TLS it does not create keying
	material at the application layer and is not suitable for use with		material at the application layer and is not suitable for use with
	channel bindings.		channel bindings.
	The channel binding data is computed by the client based on it's		The channel binding data is computed by the client based on it's
	choice of preferred channel binding type. As specified in [RFC5056],		choice of preferred channel binding type. As specified in [RFC5056],
	the channel binding information MUST start with the channel binding		the channel binding information MUST start with the channel binding
	unique prefix, followed by a colon (ASCII 0x3A), followed by a base64		unique prefix, followed by a colon (ASCII 0x3A), followed by a base64
	encoded channel binding payload. The channel binding payload is the		encoded channel binding payload. The channel binding payload is the
	raw data from the channel binding type. For example, if the client		raw data from the channel binding type. For example, if the client
	is using tls-unique for channel binding then the raw channel binding		is using tls-unique for channel binding then the raw channel binding
	skipping to change at page 14, line 19 ¶		skipping to change at page 14, line 19 ¶
	A SASL OAuth mechanism is also a GSS-API mechanism and the messages		A SASL OAuth mechanism is also a GSS-API mechanism and the messages
	described in Section 3 are the same with the following changes to the		described in Section 3 are the same with the following changes to the
	GS2 related elements:		GS2 related elements:
	1. the GS2 header on the client's first message is excluded when		1. the GS2 header on the client's first message is excluded when
	used as a GSS-API mechanism.		used as a GSS-API mechanism.
	2. the initial context token header is prefixed to the client's		2. the initial context token header is prefixed to the client's
	first authentication message (context token), as described in		first authentication message (context token), as described in
	Section 3.1 of RFC 2743,		Section 3.1 of RFC 2743 [RFC2743],
	The GSS-API mechanism OIDs are:		The GSS-API mechanism OIDs are:
	o OAUTHBEARER: [[TBD: IANA -- probably in the 1.3.6.1.5.5 tree]]		o OAUTHBEARER: [[TBD: IANA -- probably in the 1.3.6.1.5.5 tree]]
	o OAUTH10A: [[TBD: IANA -- probably in the 1.3.6.1.5.5 tree]]		o OAUTH10A: [[TBD: IANA -- probably in the 1.3.6.1.5.5 tree]]
	OAuth mechanims security contexts always have the mutual_state flag		o OAUTH10A-PLUS: [[TBD: IANA -- probably in the 1.3.6.1.5.5 tree]]
	(GSS_C_MUTUAL_FLAG) set to TRUE. OAuth supports credential
	delegation, therefore security contexts may have the deleg_state flag
	(GSS_C_DELEG_FLAG) set to either TRUE or FALSE.
	The mutual authentication property of this mechanism relies on		The setting of the security context flags depends on the selected
	successfully comparing the TLS server identity with the negotiated		mechanism:
	target name. Since the TLS channel is managed by the application
	outside of the GSS-API mechanism, the mechanism itself is unable to		o OAUTHBEARER: The mutual_state flag (GSS_C_MUTUAL_FLAG) MUST be set
	confirm the name while the application is able to perform this		to FALSE since the TLS protocol execution happens outside the
	comparison for the mechanism. For this reason, applications MUST		SASL/GSS-API method. Server-side authentication is accomplished
	match the TLS server identity with the target name using the		via the mandatory use of TLS at the application layer utilizing
	appropriate application profile, as discussed in [RFC6125]. For		SASL. Without TLS usage at the application layer protecting the
	example, when SASL OAuth is run over IMAP then the IMAP profile of		by OAuth Bearer Token this SASL method is insecure.
	RFC 6125 is used.
			o OAUTH10A: The mutual_state flag (GSS_C_MUTUAL_FLAG) MUST be set to
			FALSE since server authentication is not provided by this SASL/
			GSS-API method. Since the TLS channel is managed by the
			application outside of the GSS-API mechanism, the OAUTH10A
			mechanism itself is unable to confirm the name while the
			application is able to perform this comparison for the mechanism.
			For this reason, applications MUST match the TLS server identity
			with the target name using the appropriate application profile, as
			discussed in [RFC6125]. For example, when SASL OAuth is run over
			IMAP then the IMAP profile of RFC 6125 is used.
			o OAUTH10A-PLUS: The mutual_state flag (GSS_C_MUTUAL_FLAG) MUST be
			set to FALSE since only the client demonstrates possession of the
			session key by applying a keyed message digest function over
			various fields of the request. TLS-based server-side
			authentication MUST be provided by the application using SASL.
			Credential delegation is not supported by any of the SASL/GSS-API
			mechanisms with this specification. Therefore, security contexts
			MUST have the deleg_state flag (GSS_C_DELEG_FLAG) set to FALSE.
	OAuth mechanisms do not support per-message tokens or		OAuth mechanisms do not support per-message tokens or
	GSS_Pseudo_random.		GSS_Pseudo_random.
	OAuth supports a standard generic name syntax for acceptors, such as		OAuth supports a standard generic name syntax for acceptors, such as
	GSS_C_NT_HOSTBASED_SERVICE (see [RFC2743], Section 4.1). These		GSS_C_NT_HOSTBASED_SERVICE (see Section 4.1 of [RFC2743]). These
	service names MUST be associated with the "entityID" claimed by the		service names MUST be associated with the "entityID" claimed by the
	RP. OAuth mechanisms support only a single name type for initiators:		RP.
			OAuth mechanisms support only a single name type for initiators:
	GSS_C_NT_USER_NAME. GSS_C_NT_USER_NAME is the default name type.		GSS_C_NT_USER_NAME. GSS_C_NT_USER_NAME is the default name type.
	The query, display, and exported name syntaxes for OAuth principal		The query, display, and exported name syntaxes for OAuth principal
	names are all the same. There is no OAuth-specific name syntax;		names are all the same. There is no OAuth-specific name syntax;
	applications SHOULD use generic GSS-API name types, such as		applications SHOULD use generic GSS-API name types, such as
	GSS_C_NT_USER_NAME and GSS_C_NT_HOSTBASED_SERVICE (see [RFC2743],		GSS_C_NT_USER_NAME and GSS_C_NT_HOSTBASED_SERVICE (see Section 4 of
	Section 4). The exported name token does, of course, conform to		[RFC2743]). The exported name token does, of course, conform to
	[RFC2743], Section 3.2, but the "NAME" part of the token should be		Section 3.2 of [RFC2743], but the "NAME" part of the token should be
	treated as a potential input string to the OAuth name normalization		treated as a potential input string to the OAuth name normalization
	rules.		rules.
	5. Examples		5. Examples
	These examples illustrate exchanges between an IMAP and SMTP clients		These examples illustrate exchanges between an IMAP and SMTP clients
	and servers.		and servers.
	Note to implementers: The SASL OAuth method names are case		Note to implementers: The SASL OAuth method names are case
	insensitive. One example uses "Bearer" but that could as easily be		insensitive. One example uses "Bearer" but that could as easily be
	"bearer", "BEARER", or "BeArEr".		"bearer", "BEARER", or "BeArEr".
	5.1. Successful Bearer Token Exchange		5.1. Successful Bearer Token Exchange
	This example shows a successful OAuth 2.0 bearer token exchange.		This example shows a successful OAuth 2.0 bearer token exchange.
	Note that line breaks are inserted for readability.		Note that line breaks are inserted for readability and the underlying
			TLS establishment is not shown either.
	S: * OK IMAP4rev1 Server Ready		S: * OK IMAP4rev1 Server Ready
	C: t0 CAPABILITY		C: t0 CAPABILITY
	S: * CAPABILITY IMAP4rev1 AUTH=OAUTHBEARER SASL-IR		S: * CAPABILITY IMAP4rev1 AUTH=OAUTHBEARER SASL-IR
	S: t0 OK Completed		S: t0 OK Completed
	C: t1 AUTHENTICATE OAUTHBEARER bixhPXVzZXJAZXhhbXBsZS5jb20BaG9zdD1zZX		C: t1 AUTHENTICATE OAUTHBEARER bixhPXVzZXJAZXhhbXBsZS5jb20BaG9zdD1zZX
	J2ZXIuZXhhbXBsZS5jb20BcG9ydD0xNDMBYXV0aD1CZWFyZXIgdkY5ZGZ0NHFtV		J2ZXIuZXhhbXBsZS5jb20BcG9ydD0xNDMBYXV0aD1CZWFyZXIgdkY5ZGZ0NHFtV
	GMyTnZiM1JsY2tCaGJIUmhkbWx6ZEdFdVkyOXRDZz09AQE=		GMyTnZiM1JsY2tCaGJIUmhkbWx6ZEdFdVkyOXRDZz09AQE=
	S: t1 OK SASL authentication succeeded		S: t1 OK SASL authentication succeeded
	skipping to change at page 21, line 8 ¶		skipping to change at page 21, line 8 ¶
	S: 535 5.7.1 http://support.example.com/mail/oauth		S: 535 5.7.1 http://support.example.com/mail/oauth
	[connection continues...]		[connection continues...]
	The server returned an error message in the 334 SASL message, the		The server returned an error message in the 334 SASL message, the
	client responds with the required dummy response, and the server		client responds with the required dummy response, and the server
	finalizes the negotiation.		finalizes the negotiation.
	6. Security Considerations		6. Security Considerations
	OAuth 1.0a and OAuth 2 allows for a variety of deployment scenarios,		OAuth 1.0a and OAuth 2 allows for a variety of deployment scenarios,
	and the security properties of these profiles vary. Application		and the security properties of these profiles vary. As shown in
	developers therefore need to understand the needs of their		Figure 1 this specification is aimed to be integrated into a larger
	applications before selecting a specific SASL OAuth mechanism.		OAuth deployment. Application developers therefore need to
			understand the needs of their security requirements based on a threat
			assessment before selecting a specific SASL OAuth mechanism. For
			OAuth 2.0 a detailed security document [RFC6819] provides guidance to
			select those OAuth 2.0 components that help to mitigate threats for a
			given deployment. For OAuth 1.0a Section 4 of RFC 5849 [RFC5849]
			provides guidance specific to OAuth 1.0.
	The channel binding in this mechanism has different properties based		This document specifies three SASL and GSS-API Mechanisms for OAuth
	on the Access Token Type used.		and each comes with different security properties.
	It is possible that SASL will be authenticating a connection and the		OAUTHBEARER: This mechanism borrows from OAuth 2.0 bearer tokens
	life of that connection may outlast the life of the access token used		[RFC6750]. It relies on the application using TLS to protect the
	to establish it. This is a common problem in application protocols		OAuth 2.0 Bearer Token exchange; without TLS usage at the
	where connections are long-lived, and not a problem with this		application layer this method is completely insecure.
	mechanism per se. Servers MAY unilaterally disconnect clients in
	accordance with the application protocol.
	The OAuth access token (and related keying material) is not		OAUTH10A: This mechanism re-uses OAuth 1.0a MAC tokens (using the
	equivalent to the user's long term password. As such, care has to be		HMAC-SHA1 keyed message digest), as described in Section 3.4.2 of
	taken when these OAuth credentials are used for actions like changing		[RFC5849]. To compute the keyed message digest in the same way
	passwords (as it is possible with some protocols, e.g., XMPP). The		was in RFC 5839 this specification conveys additional parameters
	server SHOULD ensure that actions taken in the authenticated channel		between the client and the server. This SASL/GSS-API mechanism
	are appropriate to the strength of the presented credential.		only supports client authentication. If server-side
			authentication is desireable then it must be provided by the
			application underneath the SASL/GSS-API layer.
	Access tokens have a lifetime. Reducing the lifetime of an access		OAUTH10A-PLUS: This mechanism adds the channel binding [RFC5056]
	token provides security benefits, as described in		capability to OAUTH10A for protection against man-in-the-middle
	[I-D.ietf-oauth-v2-threatmodel], and OAuth 2.0 introduces refresh		attacks. OAUTH10A-PLUS mandates the usage of Transport Layer
	tokens to obtain new access token on the fly. Additionally, a		Security (TLS) at the application layer.
	previously obtained access token MAY be revoked or rendered invalid
	at any time. The client MAY request a new access token for each
	connection to a resource server, but it SHOULD cache and re-use
	access credentials that appear to be valid.
	7. Internationalization Considerations		7. Internationalization Considerations
	The identifer asserted by the OAuth authorization server about the		The identifer asserted by the OAuth authorization server about the
	resource owner inside the access token may be displayed to a human.		resource owner inside the access token may be displayed to a human.
	For example, when SASL is used in the context of IMAP the resource		For example, when SASL is used in the context of IMAP the resource
	server may assert the resource owner's email address to the IMAP		server may assert the resource owner's email address to the IMAP
	server for usage in an email-based application. The identifier may		server for usage in an email-based application. The identifier may
	therefore contain internationalized characters and an application		therefore contain internationalized characters and an application
	needs to ensure that the mapping between the identifier provided by		needs to ensure that the mapping between the identifier provided by
	skipping to change at page 26, line 36 ¶		skipping to change at page 26, line 36 ¶
	[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework",		[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework",
	RFC 6749, October 2012.		RFC 6749, October 2012.
	[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization		[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
	Framework: Bearer Token Usage", RFC 6750, October 2012.		Framework: Bearer Token Usage", RFC 6750, October 2012.
	9.2. Informative References		9.2. Informative References
	[I-D.ietf-appsawg-webfinger]		[I-D.ietf-appsawg-webfinger]
	Jones, P., Salgueiro, G., and J. Smarr, "WebFinger",		Jones, P., Salgueiro, G., and J. Smarr, "WebFinger",
	draft-ietf-appsawg-webfinger-07 (work in progress),		draft-ietf-appsawg-webfinger-10 (work in progress),
	December 2012.		February 2013.
	[I-D.ietf-oauth-json-web-token]		[I-D.ietf-oauth-json-web-token]
	Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token		Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
	(JWT)", draft-ietf-oauth-json-web-token-05 (work in		(JWT)", draft-ietf-oauth-json-web-token-06 (work in
	progress), November 2012.		progress), December 2012.
	[I-D.ietf-oauth-v2-http-mac]		[I-D.ietf-oauth-v2-http-mac]
	Richer, J., Mills, W., and H. Tschofenig, "OAuth 2.0		Richer, J., Mills, W., and H. Tschofenig, "OAuth 2.0
	Message Authentication Code (MAC) Tokens",		Message Authentication Code (MAC) Tokens",
	draft-ietf-oauth-v2-http-mac-02 (work in progress),		draft-ietf-oauth-v2-http-mac-02 (work in progress),
	November 2012.		November 2012.
	[I-D.ietf-oauth-v2-threatmodel]
	Lodderstedt, T., McGloin, M., and P. Hunt, "OAuth 2.0
	Threat Model and Security Considerations",
	draft-ietf-oauth-v2-threatmodel-08 (work in progress),
	October 2012.
	[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION		[RFC3501] Crispin, M., "INTERNET MESSAGE ACCESS PROTOCOL - VERSION
	4rev1", RFC 3501, March 2003.		4rev1", RFC 3501, March 2003.
			[RFC6819] Lodderstedt, T., McGloin, M., and P. Hunt, "OAuth 2.0
			Threat Model and Security Considerations", RFC 6819,
			January 2013.
	Appendix A. Acknowlegements		Appendix A. Acknowlegements
	The authors would like to thank the members of the Kitten working		The authors would like to thank the members of the Kitten working
	group, and in addition and specifically: Simon Josefson, Torsten		group, and in addition and specifically: Simon Josefson, Torsten
	Lodderstadt, Ryan Troll, Alexey Melnikov, and Nico Williams.		Lodderstadt, Ryan Troll, Alexey Melnikov, Jeffrey Hutzelman, and Nico
			Williams.
	This document was produced under the chairmanship of Alexey Melnikov,		This document was produced under the chairmanship of Alexey Melnikov,
	Tom Yu, Shawn Emery, Josh Howlett, Sam Hartman. The area directors		Tom Yu, Shawn Emery, Josh Howlett, Sam Hartman. The supervising area
	included Stephen Farrell.		directors was Stephen Farrell.
	Appendix B. Document History		Appendix B. Document History
	[[ to be removed by RFC editor before publication as an RFC ]]		[[ to be removed by RFC editor before publication as an RFC ]]
			-10
			o Clarifications throughout the document in response to the feedback
			from Jeffrey Hutzelman.
	-09		-09
	o Incorporated review by Alexey and Hannes.		o Incorporated review by Alexey and Hannes.
	o Clarified the three OAuth SASL mechanisms.		o Clarified the three OAuth SASL mechanisms.
	o Updated references		o Updated references
	o Extended acknowledgements		o Extended acknowledgements
End of changes. 47 change blocks.
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