< draft-ietf-oauth-v2-1-03.txt		draft-ietf-oauth-v2-1-04.txt >
	OAuth Working Group D. Hardt		OAuth Working Group D. Hardt
	Internet-Draft SignIn.Org		Internet-Draft Hellō
	Intended status: Standards Track A. Parecki		Intended status: Standards Track A. Parecki
	Expires: 12 March 2022 Okta		Expires: 8 April 2022 Okta
	T. Lodderstedt		T. Lodderstedt
	yes.com		yes.com
	8 September 2021		5 October 2021
	The OAuth 2.1 Authorization Framework		The OAuth 2.1 Authorization Framework
	draft-ietf-oauth-v2-1-03		draft-ietf-oauth-v2-1-04
	Abstract		Abstract
	The OAuth 2.1 authorization framework enables a third-party		The OAuth 2.1 authorization framework enables a third-party
	application to obtain limited access to an HTTP service, either on		application to obtain limited access to an HTTP service, either on
	behalf of a resource owner by orchestrating an approval interaction		behalf of a resource owner by orchestrating an approval interaction
	between the resource owner and an authorization service, or by		between the resource owner and an authorization service, or by
	allowing the third-party application to obtain access on its own		allowing the third-party application to obtain access on its own
	behalf. This specification replaces and obsoletes the OAuth 2.0		behalf. This specification replaces and obsoletes the OAuth 2.0
	Authorization Framework described in RFC 6749.		Authorization Framework described in RFC 6749.
	skipping to change at page 1, line 39 ¶		skipping to change at page 1, line 39 ¶
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	This Internet-Draft will expire on 12 March 2022.		This Internet-Draft will expire on 8 April 2022.
	Copyright Notice		Copyright Notice
	Copyright (c) 2021 IETF Trust and the persons identified as the		Copyright (c) 2021 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
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	Please review these documents carefully, as they describe your rights		Please review these documents carefully, as they describe your rights
	skipping to change at page 2, line 28 ¶		skipping to change at page 2, line 28 ¶
	1.4. Access Token . . . . . . . . . . . . . . . . . . . . . . 11		1.4. Access Token . . . . . . . . . . . . . . . . . . . . . . 11
	1.5. TLS Version . . . . . . . . . . . . . . . . . . . . . . . 12		1.5. TLS Version . . . . . . . . . . . . . . . . . . . . . . . 12
	1.6. HTTP Redirections . . . . . . . . . . . . . . . . . . . . 12		1.6. HTTP Redirections . . . . . . . . . . . . . . . . . . . . 12
	1.7. Interoperability . . . . . . . . . . . . . . . . . . . . 12		1.7. Interoperability . . . . . . . . . . . . . . . . . . . . 12
	1.8. Compatibility with OAuth 2.0 . . . . . . . . . . . . . . 13		1.8. Compatibility with OAuth 2.0 . . . . . . . . . . . . . . 13
	1.9. Notational Conventions . . . . . . . . . . . . . . . . . 13		1.9. Notational Conventions . . . . . . . . . . . . . . . . . 13
	2. Client Registration . . . . . . . . . . . . . . . . . . . . . 14		2. Client Registration . . . . . . . . . . . . . . . . . . . . . 14
	2.1. Client Types . . . . . . . . . . . . . . . . . . . . . . 14		2.1. Client Types . . . . . . . . . . . . . . . . . . . . . . 14
	2.2. Client Identifier . . . . . . . . . . . . . . . . . . . . 16		2.2. Client Identifier . . . . . . . . . . . . . . . . . . . . 16
	2.3. Client Redirection Endpoint . . . . . . . . . . . . . . . 16		2.3. Client Redirection Endpoint . . . . . . . . . . . . . . . 16
	2.3.1. Endpoint Request Confidentiality . . . . . . . . . . 16		2.3.1. Endpoint Request Confidentiality . . . . . . . . . . 17
	2.3.2. Registration Requirements . . . . . . . . . . . . . . 17		2.3.2. Registration Requirements . . . . . . . . . . . . . . 17
	2.3.3. Multiple Redirect URIs . . . . . . . . . . . . . . . 17		2.3.3. Multiple Redirect URIs . . . . . . . . . . . . . . . 17
	2.3.4. Invalid Endpoint . . . . . . . . . . . . . . . . . . 17		2.3.4. Invalid Endpoint . . . . . . . . . . . . . . . . . . 17
	2.3.5. Endpoint Content . . . . . . . . . . . . . . . . . . 17		2.3.5. Endpoint Content . . . . . . . . . . . . . . . . . . 18
	2.4. Client Authentication . . . . . . . . . . . . . . . . . . 18		2.4. Client Authentication . . . . . . . . . . . . . . . . . . 18
	2.4.1. Client Secret . . . . . . . . . . . . . . . . . . . . 19		2.4.1. Client Secret . . . . . . . . . . . . . . . . . . . . 19
	2.4.2. Other Authentication Methods . . . . . . . . . . . . 20		2.4.2. Other Authentication Methods . . . . . . . . . . . . 20
	2.5. Unregistered Clients . . . . . . . . . . . . . . . . . . 20		2.5. Unregistered Clients . . . . . . . . . . . . . . . . . . 20
	3. Protocol Endpoints . . . . . . . . . . . . . . . . . . . . . 20		3. Protocol Endpoints . . . . . . . . . . . . . . . . . . . . . 20
	3.1. Authorization Endpoint . . . . . . . . . . . . . . . . . 21		3.1. Authorization Endpoint . . . . . . . . . . . . . . . . . 21
	3.2. Token Endpoint . . . . . . . . . . . . . . . . . . . . . 21		3.2. Token Endpoint . . . . . . . . . . . . . . . . . . . . . 21
	3.2.1. Client Authentication . . . . . . . . . . . . . . . . 22		3.2.1. Client Authentication . . . . . . . . . . . . . . . . 22
	3.2.2. Token Request . . . . . . . . . . . . . . . . . . . . 22		3.2.2. Token Request . . . . . . . . . . . . . . . . . . . . 22
	3.2.3. Token Response . . . . . . . . . . . . . . . . . . . 24		3.2.3. Token Response . . . . . . . . . . . . . . . . . . . 24
	4. Grant Types . . . . . . . . . . . . . . . . . . . . . . . . . 27		4. Grant Types . . . . . . . . . . . . . . . . . . . . . . . . . 27
	4.1. Authorization Code Grant . . . . . . . . . . . . . . . . 28		4.1. Authorization Code Grant . . . . . . . . . . . . . . . . 28
	4.1.1. Authorization Request . . . . . . . . . . . . . . . . 29		4.1.1. Authorization Request . . . . . . . . . . . . . . . . 29
	4.1.2. Authorization Response . . . . . . . . . . . . . . . 32		4.1.2. Authorization Response . . . . . . . . . . . . . . . 32
	4.1.3. Token Endpoint Extension . . . . . . . . . . . . . . 35		4.1.3. Token Endpoint Extension . . . . . . . . . . . . . . 35
	4.2. Client Credentials Grant . . . . . . . . . . . . . . . . 36		4.2. Client Credentials Grant . . . . . . . . . . . . . . . . 36
	4.2.1. Token Endpoint Extension . . . . . . . . . . . . . . 37		4.2.1. Token Endpoint Extension . . . . . . . . . . . . . . 37
	4.3. Refresh Token Grant . . . . . . . . . . . . . . . . . . . 38		4.3. Refresh Token Grant . . . . . . . . . . . . . . . . . . . 37
	4.3.1. Token Endpoint Extension . . . . . . . . . . . . . . 38		4.3.1. Token Endpoint Extension . . . . . . . . . . . . . . 37
	4.3.2. Refresh Token Response . . . . . . . . . . . . . . . 39		4.3.2. Refresh Token Response . . . . . . . . . . . . . . . 39
	4.4. Extension Grants . . . . . . . . . . . . . . . . . . . . 40		4.4. Extension Grants . . . . . . . . . . . . . . . . . . . . 39
	5. Accessing Protected Resources . . . . . . . . . . . . . . . . 41		5. Accessing Protected Resources . . . . . . . . . . . . . . . . 40
	5.1. Access Token Types . . . . . . . . . . . . . . . . . . . 41		5.1. Access Token Types . . . . . . . . . . . . . . . . . . . 40
	5.2. Bearer Tokens . . . . . . . . . . . . . . . . . . . . . . 42		5.2. Bearer Tokens . . . . . . . . . . . . . . . . . . . . . . 41
	5.2.1. Authenticated Requests . . . . . . . . . . . . . . . 42		5.2.1. Authenticated Requests . . . . . . . . . . . . . . . 41
	5.2.2. The WWW-Authenticate Response Header Field . . . . . 44		5.2.2. The WWW-Authenticate Response Header Field . . . . . 43
	5.2.3. Error Codes . . . . . . . . . . . . . . . . . . . . . 45		5.2.3. Error Codes . . . . . . . . . . . . . . . . . . . . . 44
	5.3. Error Response . . . . . . . . . . . . . . . . . . . . . 46		5.3. Error Response . . . . . . . . . . . . . . . . . . . . . 45
	5.3.1. Extension Token Types . . . . . . . . . . . . . . . . 46		5.3.1. Extension Token Types . . . . . . . . . . . . . . . . 45
	6. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 46		6. Extensibility . . . . . . . . . . . . . . . . . . . . . . . . 46
	6.1. Defining Access Token Types . . . . . . . . . . . . . . . 47		6.1. Defining Access Token Types . . . . . . . . . . . . . . . 46
	6.2. Defining New Endpoint Parameters . . . . . . . . . . . . 47		6.2. Defining New Endpoint Parameters . . . . . . . . . . . . 46
	6.3. Defining New Authorization Grant Types . . . . . . . . . 47		6.3. Defining New Authorization Grant Types . . . . . . . . . 47
	6.4. Defining New Authorization Endpoint Response Types . . . 48		6.4. Defining New Authorization Endpoint Response Types . . . 47
	6.5. Defining Additional Error Codes . . . . . . . . . . . . . 48		6.5. Defining Additional Error Codes . . . . . . . . . . . . . 47
	7. Security Considerations . . . . . . . . . . . . . . . . . . . 49		7. Security Considerations . . . . . . . . . . . . . . . . . . . 48
	7.1. Access Token Security Considerations . . . . . . . . . . 49		7.1. Access Token Security Considerations . . . . . . . . . . 48
	7.1.1. Security Threats . . . . . . . . . . . . . . . . . . 49		7.1.1. Security Threats . . . . . . . . . . . . . . . . . . 48
	7.1.2. Threat Mitigation . . . . . . . . . . . . . . . . . . 50		7.1.2. Threat Mitigation . . . . . . . . . . . . . . . . . . 49
	7.1.3. Summary of Recommendations . . . . . . . . . . . . . 52		7.1.3. Summary of Recommendations . . . . . . . . . . . . . 51
	7.1.4. Token Replay Prevention . . . . . . . . . . . . . . . 53		7.1.4. Token Replay Prevention . . . . . . . . . . . . . . . 52
	7.1.5. Access Token Privilege Restriction . . . . . . . . . 54		7.1.5. Access Token Privilege Restriction . . . . . . . . . 52
	7.2. Client Authentication . . . . . . . . . . . . . . . . . . 54		7.2. Client Authentication . . . . . . . . . . . . . . . . . . 53
	7.2.1. Client Authentication of Native Apps . . . . . . . . 55		7.2.1. Client Authentication of Native Apps . . . . . . . . 54
	7.3. Registration of Native App Clients . . . . . . . . . . . 55		7.3. Registration of Native App Clients . . . . . . . . . . . 54
	7.4. Client Impersonation . . . . . . . . . . . . . . . . . . 56		7.4. Client Impersonation . . . . . . . . . . . . . . . . . . 54
	7.4.1. Impersonation of Native Apps . . . . . . . . . . . . 56		7.4.1. Impersonation of Native Apps . . . . . . . . . . . . 55
	7.4.2. Access Token Privilege Restriction . . . . . . . . . 57		7.4.2. Access Token Privilege Restriction . . . . . . . . . 55
	7.4.3. Access Token Replay Prevention . . . . . . . . . . . 57		7.4.3. Access Token Replay Prevention . . . . . . . . . . . 56
	7.5. Refresh Tokens . . . . . . . . . . . . . . . . . . . . . 58		7.5. Refresh Tokens . . . . . . . . . . . . . . . . . . . . . 56
	7.6. Client Impersonating Resource Owner . . . . . . . . . . . 58		7.6. Client Impersonating Resource Owner . . . . . . . . . . . 57
	7.7. Protecting the Authorization Code Flow . . . . . . . . . 59		7.7. Protecting the Authorization Code Flow . . . . . . . . . 57
	7.7.1. Loopback Redirect Considerations in Native Apps . . . 59		7.7.1. Loopback Redirect Considerations in Native Apps . . . 58
	7.7.2. HTTP 307 Redirect . . . . . . . . . . . . . . . . . . 60		7.7.2. HTTP 307 Redirect . . . . . . . . . . . . . . . . . . 58
	7.8. Authorization Codes . . . . . . . . . . . . . . . . . . . 61		7.8. Authorization Codes . . . . . . . . . . . . . . . . . . . 59
	7.9. Request Confidentiality . . . . . . . . . . . . . . . . . 62		7.9. Request Confidentiality . . . . . . . . . . . . . . . . . 60
	7.10. Ensuring Endpoint Authenticity . . . . . . . . . . . . . 62		7.10. Ensuring Endpoint Authenticity . . . . . . . . . . . . . 61
	7.11. Credentials-Guessing Attacks . . . . . . . . . . . . . . 62		7.11. Credentials-Guessing Attacks . . . . . . . . . . . . . . 61
	7.12. Phishing Attacks . . . . . . . . . . . . . . . . . . . . 63		7.12. Phishing Attacks . . . . . . . . . . . . . . . . . . . . 61
	7.13. Fake External User-Agents in Native Apps . . . . . . . . 63		7.13. Fake External User-Agents in Native Apps . . . . . . . . 62
	7.14. Malicious External User-Agents in Native Apps . . . . . . 64		7.14. Malicious External User-Agents in Native Apps . . . . . . 62
	7.15. Cross-Site Request Forgery . . . . . . . . . . . . . . . 64		7.15. Cross-Site Request Forgery . . . . . . . . . . . . . . . 62
	7.16. Clickjacking . . . . . . . . . . . . . . . . . . . . . . 65		7.16. Clickjacking . . . . . . . . . . . . . . . . . . . . . . 63
	7.17. Code Injection and Input Validation . . . . . . . . . . . 66		7.17. Code Injection and Input Validation . . . . . . . . . . . 64
	7.18. Open Redirectors . . . . . . . . . . . . . . . . . . . . 66		7.18. Open Redirectors . . . . . . . . . . . . . . . . . . . . 64
	7.18.1. Client as Open Redirector . . . . . . . . . . . . . 66		7.18.1. Client as Open Redirector . . . . . . . . . . . . . 64
	7.18.2. Authorization Server as Open Redirector . . . . . . 66		7.18.2. Authorization Server as Open Redirector . . . . . . 65
	7.19. Authorization Server Mix-Up Mitigation in Native Apps . . 67		7.19. Authorization Server Mix-Up Mitigation in Native Apps . . 65
	7.20. Embedded User Agents in Native Apps . . . . . . . . . . . 67		7.20. Embedded User Agents in Native Apps . . . . . . . . . . . 66
	7.21. Other Recommendations . . . . . . . . . . . . . . . . . . 68		7.21. Other Recommendations . . . . . . . . . . . . . . . . . . 66
	8. Native Applications . . . . . . . . . . . . . . . . . . . . . 68		8. Native Applications . . . . . . . . . . . . . . . . . . . . . 67
	8.1. Using Inter-App URI Communication for OAuth in Native		8.1. Using Inter-App URI Communication for OAuth in Native
	Apps . . . . . . . . . . . . . . . . . . . . . . . . . . 69		Apps . . . . . . . . . . . . . . . . . . . . . . . . . . 68
	8.2. Initiating the Authorization Request from a Native App . 70		8.2. Initiating the Authorization Request from a Native App . 68
	8.3. Receiving the Authorization Response in a Native App . . 70		8.3. Receiving the Authorization Response in a Native App . . 69
	8.3.1. Private-Use URI Scheme Redirection . . . . . . . . . 71		8.3.1. Private-Use URI Scheme Redirection . . . . . . . . . 69
	8.3.2. Claimed "https" Scheme URI Redirection . . . . . . . 72		8.3.2. Claimed "https" Scheme URI Redirection . . . . . . . 70
	8.3.3. Loopback Interface Redirection . . . . . . . . . . . 72		8.3.3. Loopback Interface Redirection . . . . . . . . . . . 71
	9. Browser-Based Apps . . . . . . . . . . . . . . . . . . . . . 73		9. Browser-Based Apps . . . . . . . . . . . . . . . . . . . . . 72
	10. Differences from OAuth 2.0 . . . . . . . . . . . . . . . . . 73		10. Differences from OAuth 2.0 . . . . . . . . . . . . . . . . . 72
	11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 74		11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 73
	12. References . . . . . . . . . . . . . . . . . . . . . . . . . 74		12. References . . . . . . . . . . . . . . . . . . . . . . . . . 73
	12.1. Normative References . . . . . . . . . . . . . . . . . . 74		12.1. Normative References . . . . . . . . . . . . . . . . . . 73
	12.2. Informative References . . . . . . . . . . . . . . . . . 77		12.2. Informative References . . . . . . . . . . . . . . . . . 75
	Appendix A. Augmented Backus-Naur Form (ABNF) Syntax . . . . . . 80		Appendix A. Augmented Backus-Naur Form (ABNF) Syntax . . . . . . 79
	A.1. "client_id" Syntax . . . . . . . . . . . . . . . . . . . 80		A.1. "client_id" Syntax . . . . . . . . . . . . . . . . . . . 79
	A.2. "client_secret" Syntax . . . . . . . . . . . . . . . . . 80		A.2. "client_secret" Syntax . . . . . . . . . . . . . . . . . 79
	A.3. "response_type" Syntax . . . . . . . . . . . . . . . . . 80		A.3. "response_type" Syntax . . . . . . . . . . . . . . . . . 79
	A.4. "scope" Syntax . . . . . . . . . . . . . . . . . . . . . 81		A.4. "scope" Syntax . . . . . . . . . . . . . . . . . . . . . 79
	A.5. "state" Syntax . . . . . . . . . . . . . . . . . . . . . 81		A.5. "state" Syntax . . . . . . . . . . . . . . . . . . . . . 80
	A.6. "redirect_uri" Syntax . . . . . . . . . . . . . . . . . . 81		A.6. "redirect_uri" Syntax . . . . . . . . . . . . . . . . . . 80
	A.7. "error" Syntax . . . . . . . . . . . . . . . . . . . . . 81		A.7. "error" Syntax . . . . . . . . . . . . . . . . . . . . . 80
	A.8. "error_description" Syntax . . . . . . . . . . . . . . . 81		A.8. "error_description" Syntax . . . . . . . . . . . . . . . 80
	A.9. "error_uri" Syntax . . . . . . . . . . . . . . . . . . . 81		A.9. "error_uri" Syntax . . . . . . . . . . . . . . . . . . . 80
	A.10. "grant_type" Syntax . . . . . . . . . . . . . . . . . . . 81		A.10. "grant_type" Syntax . . . . . . . . . . . . . . . . . . . 80
	A.11. "code" Syntax . . . . . . . . . . . . . . . . . . . . . . 82		A.11. "code" Syntax . . . . . . . . . . . . . . . . . . . . . . 81
	A.12. "access_token" Syntax . . . . . . . . . . . . . . . . . . 82		A.12. "access_token" Syntax . . . . . . . . . . . . . . . . . . 81
	A.13. "token_type" Syntax . . . . . . . . . . . . . . . . . . . 82		A.13. "token_type" Syntax . . . . . . . . . . . . . . . . . . . 81
	A.14. "expires_in" Syntax . . . . . . . . . . . . . . . . . . . 82		A.14. "expires_in" Syntax . . . . . . . . . . . . . . . . . . . 81
	A.15. "refresh_token" Syntax . . . . . . . . . . . . . . . . . 82		A.15. "refresh_token" Syntax . . . . . . . . . . . . . . . . . 81
	A.16. Endpoint Parameter Syntax . . . . . . . . . . . . . . . . 82		A.16. Endpoint Parameter Syntax . . . . . . . . . . . . . . . . 81
	A.17. "code_verifier" Syntax . . . . . . . . . . . . . . . . . 83		A.17. "code_verifier" Syntax . . . . . . . . . . . . . . . . . 81
	A.18. "code_challenge" Syntax . . . . . . . . . . . . . . . . . 83		A.18. "code_challenge" Syntax . . . . . . . . . . . . . . . . . 82
	Appendix B. Use of application/x-www-form-urlencoded Media		Appendix B. Use of application/x-www-form-urlencoded Media
	Type . . . . . . . . . . . . . . . . . . . . . . . . . . 83		Type . . . . . . . . . . . . . . . . . . . . . . . . . . 82
	Appendix C. Extensions . . . . . . . . . . . . . . . . . . . . . 84		Appendix C. Extensions . . . . . . . . . . . . . . . . . . . . . 82
	Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 85		Appendix D. Acknowledgements . . . . . . . . . . . . . . . . . . 84
	Appendix E. Document History . . . . . . . . . . . . . . . . . . 85		Appendix E. Document History . . . . . . . . . . . . . . . . . . 84
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 86		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 85
	1. Introduction		1. Introduction
	In the traditional client-server authentication model, the client		In the traditional client-server authentication model, the client
	requests an access-restricted resource (protected resource) on the		requests an access-restricted resource (protected resource) on the
	server by authenticating with the server using the resource owner's		server by authenticating with the server using the resource owner's
	credentials. In order to provide third-party applications access to		credentials. In order to provide third-party applications access to
	restricted resources, the resource owner shares its credentials with		restricted resources, the resource owner shares its credentials with
	the third party. This creates several problems and limitations:		the third party. This creates several problems and limitations:
	skipping to change at page 10, line 37 ¶		skipping to change at page 10, line 37 ¶
	credentials. The client authentication requirements are based on		credentials. The client authentication requirements are based on
	the client type and on the authorization server policies.		the client type and on the authorization server policies.
	8. The authorization server authenticates the client and validates		8. The authorization server authenticates the client and validates
	the refresh token, and if valid, issues a new access token (and,		the refresh token, and if valid, issues a new access token (and,
	optionally, a new refresh token).		optionally, a new refresh token).
	1.3.3. Client Credentials		1.3.3. Client Credentials
	The client credentials or other forms of client authentication (e.g.		The client credentials or other forms of client authentication (e.g.
	a "client_secret" or a private key used to sign a JWT) can be used as		a client_secret or a private key used to sign a JWT) can be used as
	an authorization grant when the authorization scope is limited to the		an authorization grant when the authorization scope is limited to the
	protected resources under the control of the client, or to protected		protected resources under the control of the client, or to protected
	resources previously arranged with the authorization server. Client		resources previously arranged with the authorization server. Client
	credentials are used as an authorization grant typically when the		credentials are used as an authorization grant typically when the
	client is acting on its own behalf (the client is also the resource		client is acting on its own behalf (the client is also the resource
	owner) or is requesting access to protected resources based on an		owner) or is requesting access to protected resources based on an
	authorization previously arranged with the authorization server.		authorization previously arranged with the authorization server.
	1.4. Access Token		1.4. Access Token
	skipping to change at page 14, line 49 ¶		skipping to change at page 14, line 49 ¶
	Dynamic Client Registration ([RFC7591]) defines a common general data		Dynamic Client Registration ([RFC7591]) defines a common general data
	model for clients that may be used even with manual client		model for clients that may be used even with manual client
	registration.		registration.
	2.1. Client Types		2.1. Client Types
	OAuth 2.1 defines three client types based on their ability to		OAuth 2.1 defines three client types based on their ability to
	authenticate securely with the authorization server as well as the		authenticate securely with the authorization server as well as the
	authorization server's assurance of the client's identity.		authorization server's assurance of the client's identity.
	"confidential": Clients that have credentials and their identity has		"confidential": Clients that have credentials and have a prior
	been confirmed by the AS are designated as "confidential clients"		relationship with the AS are designated as "confidential clients"
	"credentialed": Clients that have credentials and their identity has		"credentialed": Clients that have credentials but no prior
	been not been confirmed by the AS are designated as "credentialed		relationship with the AS are designated as "credentialed clients"
	clients"
	"public": Clients without credentials are called "public clients"		"public": Clients without credentials are called "public clients"
	Any clients with credentials MUST take precautions to prevent leakage		Any clients with credentials MUST take precautions to prevent leakage
	and abuse of their credentials.		and abuse of their credentials.
	Authorization servers SHOULD consider the level of confidence in a		Authorization servers SHOULD consider the level of confidence in a
	client's identity when deciding whether they allow such a client		client's identity when deciding whether they allow such a client
	access to more critical functions, such as the Client Credentials		access to more critical functions, such as the Client Credentials
	grant type.		grant type.
	A single "client_id" MUST NOT be treated as more than one type of		A single client_id MUST NOT be treated as more than one type of
	client.		client.
			For example, a client that has been registered at the authorization
			server by a registered application developer, where the client is
			expected to be run as server-side code, would be considered a
			confidential client. A client that runs on an end-user's device, and
			uses Dynamic Client Registration ([RFC7591]) to establish credentials
			the first time the app runs, would be considered a credentialed
			client. An application deployed as a single-page app on a static web
			host would be considered a public client.
	This specification has been designed around the following client		This specification has been designed around the following client
	profiles:		profiles:
	"web application": A web application is a confidential client		"web application": A web application is a confidential client
	running on a web server. Resource owners access the client via an		running on a web server. Resource owners access the client via an
	HTML user interface rendered in a user agent on the device used by		HTML user interface rendered in a user agent on the device used by
	the resource owner. The client credentials as well as any access		the resource owner. The client credentials as well as any access
	tokens issued to the client are stored on the web server and are		tokens issued to the client are stored on the web server and are
	not exposed to or accessible by the resource owner.		not exposed to or accessible by the resource owner.
	skipping to change at page 16, line 20 ¶		skipping to change at page 16, line 26 ¶
	secret; it is exposed to the resource owner and MUST NOT be used		secret; it is exposed to the resource owner and MUST NOT be used
	alone for client authentication. The client identifier is unique to		alone for client authentication. The client identifier is unique to
	the authorization server.		the authorization server.
	The client identifier string size is left undefined by this		The client identifier string size is left undefined by this
	specification. The client should avoid making assumptions about the		specification. The client should avoid making assumptions about the
	identifier size. The authorization server SHOULD document the size		identifier size. The authorization server SHOULD document the size
	of any identifier it issues.		of any identifier it issues.
	Authorization servers SHOULD NOT allow clients to choose or influence		Authorization servers SHOULD NOT allow clients to choose or influence
	their "client_id" value. See Section 7.6 for details.		their client_id value. See Section 7.6 for details.
	2.3. Client Redirection Endpoint		2.3. Client Redirection Endpoint
	The client redirection endpoint (also referred to as "redirect		The client redirection endpoint (also referred to as "redirect
	endpoint") is the URI of the client that the authorization server		endpoint") is the URI of the client that the authorization server
	redirects the user agent back to after completing its interaction		redirects the user agent back to after completing its interaction
	with the resource owner.		with the resource owner.
	The authorization server redirects the user agent to one of the		The authorization server redirects the user agent to one of the
	client's redirection endpoints previously established with the		client's redirection endpoints previously established with the
	skipping to change at page 16, line 43 ¶		skipping to change at page 17, line 8 ¶
	The redirect URI MUST be an absolute URI as defined by [RFC3986]		The redirect URI MUST be an absolute URI as defined by [RFC3986]
	Section 4.3. The endpoint URI MAY include an "application/x-www-		Section 4.3. The endpoint URI MAY include an "application/x-www-
	form-urlencoded" formatted (per Appendix B) query component		form-urlencoded" formatted (per Appendix B) query component
	([RFC3986] Section 3.4), which MUST be retained when adding		([RFC3986] Section 3.4), which MUST be retained when adding
	additional query parameters. The endpoint URI MUST NOT include a		additional query parameters. The endpoint URI MUST NOT include a
	fragment component.		fragment component.
	2.3.1. Endpoint Request Confidentiality		2.3.1. Endpoint Request Confidentiality
	The redirection endpoint SHOULD require the use of TLS as described		The redirection endpoint SHOULD require the use of TLS as described
	in Section 1.5 when the requested response type is "code", or when		in Section 1.5 when the requested response type is code, or when the
	the redirection request will result in the transmission of sensitive		redirection request will result in the transmission of sensitive
	credentials over an open network. If TLS is not available, the		credentials over an open network. If TLS is not available, the
	authorization server SHOULD warn the resource owner about the		authorization server SHOULD warn the resource owner about the
	insecure endpoint prior to redirection (e.g., display a message		insecure endpoint prior to redirection (e.g., display a message
	during the authorization request).		during the authorization request).
	2.3.2. Registration Requirements		2.3.2. Registration Requirements
	Authorization servers MUST require clients to register their complete		Authorization servers MUST require clients to register their complete
	redirect URI (including the path component) and reject authorization		redirect URI (including the path component) and reject authorization
	requests that specify a redirect URI that doesn't exactly match one		requests that specify a redirect URI that doesn't exactly match one
	that was registered; the exception is loopback redirects, where an		that was registered; the exception is loopback redirects, where an
	exact match is required except for the port URI component.		exact match is required except for the port URI component.
	For private-use URI scheme-based redirect URIs, authorization servers		For private-use URI scheme-based redirect URIs, authorization servers
	SHOULD enforce the requirement in Section 8.3.1 that clients use		SHOULD enforce the requirement in Section 8.3.1 that clients use
	schemes that are reverse domain name based. At a minimum, any		schemes that are reverse domain name based. At a minimum, any
	private-use URI scheme that doesn't contain a period character (".")		private-use URI scheme that doesn't contain a period character (.)
	SHOULD be rejected.		SHOULD be rejected.
	The client MAY use the "state" request parameter to achieve per-		The client MAY use the state request parameter to achieve per-request
	request customization if needed rather than varying the redirect URI		customization if needed rather than varying the redirect URI per
	per request.		request.
	The authorization server MAY allow the client to register multiple		The authorization server MAY allow the client to register multiple
	redirect URIs.		redirect URIs.
	Without requiring registration of redirect URIs, attackers can use		Without requiring registration of redirect URIs, attackers can use
	the authorization endpoint as an open redirector as described in		the authorization endpoint as an open redirector as described in
	Section 7.18.		Section 7.18.
	2.3.3. Multiple Redirect URIs		2.3.3. Multiple Redirect URIs
	If multiple redirect URIs have been registered, the client MUST		If multiple redirect URIs have been registered, the client MUST
	include a redirect URI with the authorization request using the		include a redirect URI with the authorization request using the
	"redirect_uri" request parameter.		redirect_uri request parameter.
	2.3.4. Invalid Endpoint		2.3.4. Invalid Endpoint
	If an authorization request fails validation due to a missing,		If an authorization request fails validation due to a missing,
	invalid, or mismatching redirect URI, the authorization server SHOULD		invalid, or mismatching redirect URI, the authorization server SHOULD
	inform the resource owner of the error and MUST NOT automatically		inform the resource owner of the error and MUST NOT automatically
	redirect the user agent to the invalid redirect URI.		redirect the user agent to the invalid redirect URI.
	2.3.5. Endpoint Content		2.3.5. Endpoint Content
	skipping to change at page 18, line 16 ¶		skipping to change at page 18, line 27 ¶
	party analytics, social plug-ins, ad networks) in the redirection		party analytics, social plug-ins, ad networks) in the redirection
	endpoint response. Instead, it SHOULD extract the credentials from		endpoint response. Instead, it SHOULD extract the credentials from
	the URI and redirect the user agent again to another endpoint without		the URI and redirect the user agent again to another endpoint without
	exposing the credentials (in the URI or elsewhere). If third-party		exposing the credentials (in the URI or elsewhere). If third-party
	scripts are included, the client MUST ensure that its own scripts		scripts are included, the client MUST ensure that its own scripts
	(used to extract and remove the credentials from the URI) will		(used to extract and remove the credentials from the URI) will
	execute first.		execute first.
	2.4. Client Authentication		2.4. Client Authentication
	Confidential and credentialed clients establish a client		If the client is confidential or credentialed, the authorization
	authentication method with the authorization server suitable for the
	security requirements of the authorization server. The authorization
	server MAY accept any form of client authentication meeting its		server MAY accept any form of client authentication meeting its
	security requirements.		security requirements (e.g., password, public/private key pair).
	Confidential and credentialed clients are typically issued (or
	establish) a set of client credentials used for authenticating with
	the authorization server (e.g., password, public/private key pair).
	The authorization server MUST authenticate the client whenever		The authorization server MUST authenticate the client whenever
	possible. If the authorization server cannot authenticate the client		possible. If the authorization server cannot authenticate the client
	due to the client's nature, the authorization server SHOULD utilize		due to the client's nature, the authorization server SHOULD utilize
	other means to protect resource owners from such potentially		other means to protect resource owners from such potentially
	malicious clients. For example, the authorization server can engage		malicious clients. For example, the authorization server can engage
	the resource owner to assist in identifying the client and its		the resource owner to assist in identifying the client and its
	origin.		origin.
	It is RECOMMENDED to use asymmetric (public-key based) methods for		It is RECOMMENDED to use asymmetric (public-key based) methods for
	skipping to change at page 18, line 46 ¶		skipping to change at page 18, line 51 ¶
	[OpenID]. When asymmetric methods for client authentication are		[OpenID]. When asymmetric methods for client authentication are
	used, authorization servers do not need to store sensitive symmetric		used, authorization servers do not need to store sensitive symmetric
	keys, making these methods more robust against a number of attacks.		keys, making these methods more robust against a number of attacks.
	The authorization server MAY establish a client authentication method		The authorization server MAY establish a client authentication method
	with public clients, which converts them to credentialed clients.		with public clients, which converts them to credentialed clients.
	However, the authorization server MUST NOT rely on credentialed		However, the authorization server MUST NOT rely on credentialed
	client authentication for the purpose of identifying the client.		client authentication for the purpose of identifying the client.
	The client MUST NOT use more than one authentication method in each		The client MUST NOT use more than one authentication method in each
	request.		request to prevent a conflict of which authentication mechanism is
			authoritative for the request.
	2.4.1. Client Secret		2.4.1. Client Secret
	Clients in possession of a client secret, sometimes known as a client		Clients in possession of a client secret, sometimes known as a client
	password, MAY use the HTTP Basic authentication scheme as defined in		password, MAY use the HTTP Basic authentication scheme as defined in
	[RFC7235] to authenticate with the authorization server. The client		[RFC7235] to authenticate with the authorization server. The client
	identifier is encoded using the "application/x-www-form-urlencoded"		identifier is encoded using the application/x-www-form-urlencoded
	encoding algorithm per Appendix B, and the encoded value is used as		encoding algorithm per Appendix B, and the encoded value is used as
	the username; the client secret is encoded using the same algorithm		the username; the client secret is encoded using the same algorithm
	and used as the password. The authorization server MUST support the		and used as the password. The authorization server MUST support the
	HTTP Basic authentication scheme for authenticating clients that were		HTTP Basic authentication scheme for authenticating clients that were
	issued a client secret.		issued a client secret.
	For example (with extra line breaks for display purposes only):		For example (with extra line breaks for display purposes only):
	Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3		Authorization: Basic czZCaGRSa3F0Mzo3RmpmcDBaQnIxS3REUmJuZlZkbUl3
	skipping to change at page 21, line 30 ¶		skipping to change at page 21, line 30 ¶
	formatted (per Appendix B) query component ([RFC3986] Section 3.4),		formatted (per Appendix B) query component ([RFC3986] Section 3.4),
	which MUST be retained when adding additional query parameters. The		which MUST be retained when adding additional query parameters. The
	endpoint URI MUST NOT include a fragment component.		endpoint URI MUST NOT include a fragment component.
	Since requests to the authorization endpoint result in user		Since requests to the authorization endpoint result in user
	authentication and the transmission of clear-text credentials (in the		authentication and the transmission of clear-text credentials (in the
	HTTP response), the authorization server MUST require the use of TLS		HTTP response), the authorization server MUST require the use of TLS
	as described in Section 1.5 when sending requests to the		as described in Section 1.5 when sending requests to the
	authorization endpoint.		authorization endpoint.
	The authorization server MUST support the use of the HTTP "GET"		The authorization server MUST support the use of the HTTP GET method
	method [RFC7231] for the authorization endpoint and MAY support the		[RFC7231] for the authorization endpoint and MAY support the use of
	use of the "POST" method as well.		the POST method as well.
	The authorization server MUST ignore unrecognized request parameters.		The authorization server MUST ignore unrecognized request parameters.
	Request and response parameters defined by this specification MUST		Request and response parameters defined by this specification MUST
	NOT be included more than once. Parameters sent without a value MUST		NOT be included more than once. Parameters sent without a value MUST
	be treated as if they were omitted from the request.		be treated as if they were omitted from the request.
	3.2. Token Endpoint		3.2. Token Endpoint
	The token endpoint is used by the client to obtain an access token		The token endpoint is used by the client to obtain an access token
	using a grant such as those described in Section 4 and Section 4.3.		using a grant such as those described in Section 4 and Section 4.3.
	The means through which the client obtains the location of the token		The means through which the client obtains the location of the token
	endpoint are beyond the scope of this specification, but the location		endpoint are beyond the scope of this specification, but the location
	is typically provided in the service documentation and configured		is typically provided in the service documentation and configured
	during development of the client, or provided in the authorization		during development of the client, or provided in the authorization
	server's metadata document ([RFC8414]) and fetched programmatically		server's metadata document ([RFC8414]) and fetched programmatically
	at runtime.		at runtime.
	The endpoint URI MAY include an "application/x-www-form-urlencoded"		The endpoint URI MAY include an application/x-www-form-urlencoded
	formatted (per Appendix B) query component ([RFC3986] Section 3.4)		formatted (per Appendix B) query component ([RFC3986] Section 3.4)
	and MUST NOT include a fragment component.		and MUST NOT include a fragment component.
	Since requests to the token endpoint result in the transmission of		Since requests to the token endpoint result in the transmission of
	clear-text credentials (in the HTTP request and response), the		clear-text credentials (in the HTTP request and response), the
	authorization server MUST require the use of TLS as described in		authorization server MUST require the use of TLS as described in
	Section 1.5 when sending requests to the token endpoint.		Section 1.5 when sending requests to the token endpoint.
	The client MUST use the HTTP "POST" method when making access token		The client MUST use the HTTP POST method when making access token
	requests.		requests.
	The authorization server MUST ignore unrecognized request parameters.		The authorization server MUST ignore unrecognized request parameters.
	Parameters sent without a value MUST be treated as if they were		Parameters sent without a value MUST be treated as if they were
	omitted from the request. Request and response parameters defined by		omitted from the request. Request and response parameters defined by
	this specification MUST NOT be included more than once.		this specification MUST NOT be included more than once.
	3.2.1. Client Authentication		3.2.1. Client Authentication
	skipping to change at page 22, line 50 ¶		skipping to change at page 22, line 50 ¶
	refresh tokens.		refresh tokens.
	* Implementing authentication management best practices, which		* Implementing authentication management best practices, which
	require periodic credential rotation. Rotation of an entire set		require periodic credential rotation. Rotation of an entire set
	of refresh tokens can be challenging, while rotation of a single		of refresh tokens can be challenging, while rotation of a single
	set of client credentials is significantly easier.		set of client credentials is significantly easier.
	3.2.2. Token Request		3.2.2. Token Request
	The client makes a request to the token endpoint by sending the		The client makes a request to the token endpoint by sending the
	following parameters using the "application/x-www-form-urlencoded"		following parameters using the application/x-www-form-urlencoded
	format per Appendix B with a character encoding of UTF-8 in the HTTP		format per Appendix B with a character encoding of UTF-8 in the HTTP
	request payload:		request payload:
	"client_id": REQUIRED, if the client is not authenticating with the		"client_id": REQUIRED, if the client is not authenticating with the
	authorization server as described in Section 3.2.1.		authorization server as described in Section 3.2.1.
	"scope": OPTIONAL. The scope of the access request as described by		"scope": OPTIONAL. The scope of the access request as described by
	Section 3.2.2.1.		Section 3.2.2.1.
	"grant_type": REQUIRED. Identifier of the grant type the client		"grant_type": REQUIRED. Identifier of the grant type the client
	uses with the particular token request. This specification		uses with the particular token request. This specification
	defines the values "authorization_code", "refresh_token", and		defines the values authorization_code, refresh_token, and
	"client_credentials". The grant type determines the further		client_credentials. The grant type determines the further
	parameters required or supported by the token request. The		parameters required or supported by the token request. The
	details of those grant types are defined below.		details of those grant types are defined below.
	Confidential or credentialed clients MUST authenticate with the		Confidential or credentialed clients MUST authenticate with the
	authorization server as described in Section 3.2.1.		authorization server as described in Section 3.2.1.
	For example, the client makes the following HTTP request using TLS		For example, the client makes the following HTTP request using TLS
	(with extra line breaks for display purposes only):		(with extra line breaks for display purposes only):
	POST /token HTTP/1.1		POST /token HTTP/1.1
	skipping to change at page 23, line 46 ¶		skipping to change at page 23, line 46 ¶
	clients (or clients with other authentication requirements),		clients (or clients with other authentication requirements),
	* authenticate the client if client authentication is included		* authenticate the client if client authentication is included
	Further grant type specific processing rules apply and are specified		Further grant type specific processing rules apply and are specified
	with the respective grant type.		with the respective grant type.
	3.2.2.1. Access Token Scope		3.2.2.1. Access Token Scope
	The authorization and token endpoints allow the client to specify the		The authorization and token endpoints allow the client to specify the
	scope of the access request using the "scope" request parameter. In		scope of the access request using the scope request parameter. In
	turn, the authorization server uses the "scope" response parameter to		turn, the authorization server uses the scope response parameter to
	inform the client of the scope of the access token issued.		inform the client of the scope of the access token issued.
	The value of the scope parameter is expressed as a list of space-		The value of the scope parameter is expressed as a list of space-
	delimited, case-sensitive strings. The strings are defined by the		delimited, case-sensitive strings. The strings are defined by the
	authorization server. If the value contains multiple space-delimited		authorization server. If the value contains multiple space-delimited
	strings, their order does not matter, and each string adds an		strings, their order does not matter, and each string adds an
	additional access range to the requested scope.		additional access range to the requested scope.
	scope = scope-token *( SP scope-token )		scope = scope-token *( SP scope-token )
	scope-token = 1*( %x21 / %x23-5B / %x5D-7E )		scope-token = 1*( %x21 / %x23-5B / %x5D-7E )
	The authorization server MAY fully or partially ignore the scope		The authorization server MAY fully or partially ignore the scope
	requested by the client, based on the authorization server policy or		requested by the client, based on the authorization server policy or
	the resource owner's instructions. If the issued access token scope		the resource owner's instructions. If the issued access token scope
	is different from the one requested by the client, the authorization		is different from the one requested by the client, the authorization
	server MUST include the "scope" response parameter to inform the		server MUST include the scope response parameter to inform the client
	client of the actual scope granted.		of the actual scope granted.
	If the client omits the scope parameter when requesting		If the client omits the scope parameter when requesting
	authorization, the authorization server MUST either process the		authorization, the authorization server MUST either process the
	request using a pre-defined default value or fail the request		request using a pre-defined default value or fail the request
	indicating an invalid scope. The authorization server SHOULD		indicating an invalid scope. The authorization server SHOULD
	document its scope requirements and default value (if defined).		document its scope requirements and default value (if defined).
	3.2.3. Token Response		3.2.3. Token Response
	If the access token request is valid and authorized, the		If the access token request is valid and authorized, the
	authorization server issues an access token and optional refresh		authorization server issues an access token and optional refresh
	token.		token.
	If the request client authentication failed or is invalid, the		If the request client authentication failed or is invalid, the
	authorization server returns an error response as described in		authorization server returns an error response as described in
	Section 3.2.3.1.		Section 3.2.3.1.
	The authorization server issues an access token and optional refresh		The authorization server issues an access token and optional refresh
	token by creating an HTTP response body using the "application/json"		token by creating an HTTP response body using the application/json
	media type as defined by [RFC8259] with the following parameters and		media type as defined by [RFC8259] with the following parameters and
	an HTTP 200 (OK) status code:		an HTTP 200 (OK) status code:
	"access_token": REQUIRED. The access token issued by the		"access_token": REQUIRED. The access token issued by the
	authorization server.		authorization server.
	"token_type": REQUIRED. The type of the access token issued as		"token_type": REQUIRED. The type of the access token issued as
	described in Section 5.1. Value is case insensitive.		described in Section 5.1. Value is case insensitive.
	"expires_in": RECOMMENDED. The lifetime in seconds of the access		"expires_in": RECOMMENDED. The lifetime in seconds of the access
	token. For example, the value "3600" denotes that the access		token. For example, the value 3600 denotes that the access token
	token will expire in one hour from the time the response was		will expire in one hour from the time the response was generated.
	generated. If omitted, the authorization server SHOULD provide		If omitted, the authorization server SHOULD provide the expiration
	the expiration time via other means or document the default value.		time via other means or document the default value.
	"scope": OPTIONAL, if identical to the scope requested by the		"scope": RECOMMENDED, if identical to the scope requested by the
	client; otherwise, REQUIRED. The scope of the access token as		client; otherwise, REQUIRED. The scope of the access token as
	described by Section 3.2.2.1.		described by Section 3.2.2.1.
	"refresh_token": OPTIONAL. The refresh token, which can be used to		"refresh_token": OPTIONAL. The refresh token, which can be used to
	obtain new access tokens based on the grant passed in the		obtain new access tokens based on the grant passed in the
	corresponding token request.		corresponding token request.
	Authorization servers SHOULD determine, based on a risk assessment		Authorization servers SHOULD determine, based on a risk assessment
	and their own policies, whether to issue refresh tokens to a certain		and their own policies, whether to issue refresh tokens to a certain
	client. If the authorization server decides not to issue refresh		client. If the authorization server decides not to issue refresh
	skipping to change at page 25, line 32 ¶		skipping to change at page 25, line 32 ¶
	the scope and resource servers as consented by the resource owner.		the scope and resource servers as consented by the resource owner.
	This is to prevent privilege escalation by the legitimate client and		This is to prevent privilege escalation by the legitimate client and
	reduce the impact of refresh token leakage.		reduce the impact of refresh token leakage.
	The parameters are serialized into a JavaScript Object Notation		The parameters are serialized into a JavaScript Object Notation
	(JSON) structure by adding each parameter at the highest structure		(JSON) structure by adding each parameter at the highest structure
	level. Parameter names and string values are included as JSON		level. Parameter names and string values are included as JSON
	strings. Numerical values are included as JSON numbers. The order		strings. Numerical values are included as JSON numbers. The order
	of parameters does not matter and can vary.		of parameters does not matter and can vary.
	The authorization server MUST include the HTTP "Cache-Control"		The authorization server MUST include the HTTP Cache-Control response
	response header field [RFC7234] with a value of "no-store" in any		header field [RFC7234] with a value of no-store in any response
	response containing tokens, credentials, or other sensitive		containing tokens, credentials, or other sensitive information.
	information.
	For example:		For example:
	HTTP/1.1 200 OK		HTTP/1.1 200 OK
	Content-Type: application/json		Content-Type: application/json
	Cache-Control: no-store		Cache-Control: no-store
	{		{
	"access_token":"2YotnFZFEjr1zCsicMWpAA",		"access_token":"2YotnFZFEjr1zCsicMWpAA",
	"token_type":"Bearer",		"token_type":"Bearer",
	skipping to change at page 26, line 23 ¶		skipping to change at page 26, line 23 ¶
	status code (unless specified otherwise) and includes the following		status code (unless specified otherwise) and includes the following
	parameters with the response:		parameters with the response:
	"error": REQUIRED. A single ASCII [USASCII] error code from the		"error": REQUIRED. A single ASCII [USASCII] error code from the
	following:		following:
	"invalid_request": The request is missing a required parameter,		"invalid_request": The request is missing a required parameter,
	includes an unsupported parameter value (other than grant		includes an unsupported parameter value (other than grant
	type), repeats a parameter, includes multiple credentials,		type), repeats a parameter, includes multiple credentials,
	utilizes more than one mechanism for authenticating the client,		utilizes more than one mechanism for authenticating the client,
	contains a "code_verifier" although no "code_challenge" was		contains a code_verifier although no code_challenge was sent in
	sent in the authorization request, or is otherwise malformed.		the authorization request, or is otherwise malformed.
	"invalid_client": Client authentication failed (e.g., unknown		"invalid_client": Client authentication failed (e.g., unknown
	client, no client authentication included, or unsupported		client, no client authentication included, or unsupported
	authentication method). The authorization server MAY return an		authentication method). The authorization server MAY return an
	HTTP 401 (Unauthorized) status code to indicate which HTTP		HTTP 401 (Unauthorized) status code to indicate which HTTP
	authentication schemes are supported. If the client attempted		authentication schemes are supported. If the client attempted
	to authenticate via the "Authorization" request header field,		to authenticate via the Authorization request header field, the
	the authorization server MUST respond with an HTTP 401		authorization server MUST respond with an HTTP 401
	(Unauthorized) status code and include the "WWW-Authenticate"		(Unauthorized) status code and include the WWW-Authenticate
	response header field matching the authentication scheme used		response header field matching the authentication scheme used
	by the client.		by the client.
	"invalid_grant": The provided authorization grant (e.g.,		"invalid_grant": The provided authorization grant (e.g.,
	authorization code, resource owner credentials) or refresh		authorization code, resource owner credentials) or refresh
	token is invalid, expired, revoked, does not match the redirect		token is invalid, expired, revoked, does not match the redirect
	URI used in the authorization request, or was issued to another		URI used in the authorization request, or was issued to another
	client.		client.
	"unauthorized_client": The authenticated client is not authorized		"unauthorized_client": The authenticated client is not authorized
	to use this authorization grant type.		to use this authorization grant type.
	"unsupported_grant_type": The authorization grant type is not		"unsupported_grant_type": The authorization grant type is not
	supported by the authorization server.		supported by the authorization server.
	"invalid_scope": The requested scope is invalid, unknown,		"invalid_scope": The requested scope is invalid, unknown,
	malformed, or exceeds the scope granted by the resource owner.		malformed, or exceeds the scope granted by the resource owner.
	Values for the "error" parameter MUST NOT include characters		Values for the error parameter MUST NOT include characters outside
	outside the set %x20-21 / %x23-5B / %x5D-7E.		the set %x20-21 / %x23-5B / %x5D-7E.
	"error_description": OPTIONAL. Human-readable ASCII [USASCII] text		"error_description": OPTIONAL. Human-readable ASCII [USASCII] text
	providing additional information, used to assist the client		providing additional information, used to assist the client
	developer in understanding the error that occurred. Values for		developer in understanding the error that occurred. Values for
	the "error_description" parameter MUST NOT include characters		the error_description parameter MUST NOT include characters
	outside the set %x20-21 / %x23-5B / %x5D-7E.		outside the set %x20-21 / %x23-5B / %x5D-7E.
	"error_uri": OPTIONAL. A URI identifying a human-readable web page		"error_uri": OPTIONAL. A URI identifying a human-readable web page
	with information about the error, used to provide the client		with information about the error, used to provide the client
	developer with additional information about the error. Values for		developer with additional information about the error. Values for
	the "error_uri" parameter MUST conform to the URI-reference syntax		the error_uri parameter MUST conform to the URI-reference syntax
	and thus MUST NOT include characters outside the set %x21 /		and thus MUST NOT include characters outside the set %x21 /
	%x23-5B / %x5D-7E.		%x23-5B / %x5D-7E.
	The parameters are included in the payload of the HTTP response using		The parameters are included in the payload of the HTTP response using
	the "application/json" media type as defined by [RFC7159]. The		the application/json media type as defined by [RFC7159]. The
	parameters are serialized into a JSON structure by adding each		parameters are serialized into a JSON structure by adding each
	parameter at the highest structure level. Parameter names and string		parameter at the highest structure level. Parameter names and string
	values are included as JSON strings. Numerical values are included		values are included as JSON strings. Numerical values are included
	as JSON numbers. The order of parameters does not matter and can		as JSON numbers. The order of parameters does not matter and can
	vary.		vary.
	For example:		For example:
	HTTP/1.1 400 Bad Request		HTTP/1.1 400 Bad Request
	Content-Type: application/json		Content-Type: application/json
	skipping to change at page 29, line 50 ¶		skipping to change at page 29, line 50 ¶
	redirect the user agent to this URI to initiate the request.		redirect the user agent to this URI to initiate the request.
	Clients use a unique secret per authorization request to protect		Clients use a unique secret per authorization request to protect
	against authorization code injection and CSRF attacks. The client		against authorization code injection and CSRF attacks. The client
	first generates this secret, which it can use at the time of		first generates this secret, which it can use at the time of
	redeeming the authorization code to prove that the client using the		redeeming the authorization code to prove that the client using the
	authorization code is the same client that requested it.		authorization code is the same client that requested it.
	The client constructs the request URI by adding the following		The client constructs the request URI by adding the following
	parameters to the query component of the authorization endpoint URI		parameters to the query component of the authorization endpoint URI
	using the "application/x-www-form-urlencoded" format, per Appendix B:		using the application/x-www-form-urlencoded format, per Appendix B:
	"response_type": REQUIRED. The authorization endpoint supports		"response_type": REQUIRED. The authorization endpoint supports
	different sets of request and response pameters. The client		different sets of request and response pameters. The client
	determines the type of flow by using a certain "response_type"		determines the type of flow by using a certain response_type
	value. This specification defines the value "code", which must be		value. This specification defines the value code, which must be
	used to signal that the client wants to use the authorization code		used to signal that the client wants to use the authorization code
	flow.		flow.
	Extension response types MAY contain a space-delimited (%x20) list of		Extension response types MAY contain a space-delimited (%x20) list of
	values, where the order of values does not matter (e.g., response		values, where the order of values does not matter (e.g., response
	type "a b" is the same as "b a"). The meaning of such composite		type a b is the same as b a). The meaning of such composite response
	response types is defined by their respective specifications.		types is defined by their respective specifications.
	Some extension response types are defined by ([OpenID]).		Some extension response types are defined by ([OpenID]).
	If an authorization request is missing the "response_type" parameter,		If an authorization request is missing the response_type parameter,
	or if the response type is not understood, the authorization server		or if the response type is not understood, the authorization server
	MUST return an error response as described in Section 4.1.2.1.		MUST return an error response as described in Section 4.1.2.1.
	"client_id": REQUIRED. The client identifier as described in		"client_id": REQUIRED. The client identifier as described in
	Section 2.2.		Section 2.2.
	"code_challenge": REQUIRED or RECOMMENDED (see Section 7.8). Code		"code_challenge": REQUIRED or RECOMMENDED (see Section 7.8). Code
	challenge.		challenge.
	"code_challenge_method": OPTIONAL, defaults to "plain" if not		"code_challenge_method": OPTIONAL, defaults to plain if not present
	present in the request. Code verifier transformation method is		in the request. Code verifier transformation method is S256 or
	"S256" or "plain".		plain.
	"redirect_uri": OPTIONAL. As described in Section 2.3.		"redirect_uri": OPTIONAL. As described in Section 2.3.
	"scope": OPTIONAL. The scope of the access request as described by		"scope": OPTIONAL. The scope of the access request as described by
	Section 3.2.2.1.		Section 3.2.2.1.
	"state": OPTIONAL. An opaque value used by the client to maintain		"state": OPTIONAL. An opaque value used by the client to maintain
	state between the request and callback. The authorization server		state between the request and callback. The authorization server
	includes this value when redirecting the user agent back to the		includes this value when redirecting the user agent back to the
	client.		client.
	The "code_verifier" is a unique high-entropy cryptographically random		The code_verifier is a unique high-entropy cryptographically random
	string generated for each authorization request, using the unreserved		string generated for each authorization request, using the unreserved
	characters "[A-Z] / [a-z] / [0-9] / "-" / "." / "_" / "~"", with a		characters [A-Z] / [a-z] / [0-9] / "-" / "." / "_" / "~", with a
	minimum length of 43 characters and a maximum length of 128		minimum length of 43 characters and a maximum length of 128
	characters.		characters.
	The client stores the "code_verifier" temporarily, and calculates the		The client stores the code_verifier temporarily, and calculates the
	"code_challenge" which it uses in the authorization request.		code_challenge which it uses in the authorization request.
	ABNF for "code_verifier" is as follows.		ABNF for code_verifier is as follows.
	code-verifier = 43*128unreserved		code-verifier = 43*128unreserved
	unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"		unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
	ALPHA = %x41-5A / %x61-7A		ALPHA = %x41-5A / %x61-7A
	DIGIT = %x30-39		DIGIT = %x30-39
	NOTE: The code verifier SHOULD have enough entropy to make it		NOTE: The code verifier SHOULD have enough entropy to make it
	impractical to guess the value. It is RECOMMENDED that the output of		impractical to guess the value. It is RECOMMENDED that the output of
	a suitable random number generator be used to create a 32-octet		a suitable random number generator be used to create a 32-octet
	sequence. The octet sequence is then base64url-encoded to produce a		sequence. The octet sequence is then base64url-encoded to produce a
	43-octet URL-safe string to use as the code verifier.		43-octet URL-safe string to use as the code verifier.
	The client then creates a "code_challenge" derived from the code		The client then creates a code_challenge derived from the code
	verifier by using one of the following transformations on the code		verifier by using one of the following transformations on the code
	verifier:		verifier:
	S256		S256
	code_challenge = BASE64URL-ENCODE(SHA256(ASCII(code_verifier)))		code_challenge = BASE64URL-ENCODE(SHA256(ASCII(code_verifier)))
	plain		plain
	code_challenge = code_verifier		code_challenge = code_verifier
	If the client is capable of using "S256", it MUST use "S256", as		If the client is capable of using S256, it MUST use S256, as S256 is
	"S256" is Mandatory To Implement (MTI) on the server. Clients are		Mandatory To Implement (MTI) on the server. Clients are permitted to
	permitted to use "plain" only if they cannot support "S256" for some		use plain only if they cannot support S256 for some technical reason,
	technical reason, for example constrained environments that do not		for example constrained environments that do not have a hashing
	have a hashing function available, and know via out-of-band		function available, and know via out-of-band configuration or via
	configuration or via Authorization Server Metadata ([RFC8414]) that		Authorization Server Metadata ([RFC8414]) that the server supports
	the server supports "plain".		plain.
	ABNF for "code_challenge" is as follows.		ABNF for code_challenge is as follows.
	code-challenge = 43*128unreserved		code-challenge = 43*128unreserved
	unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"		unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
	ALPHA = %x41-5A / %x61-7A		ALPHA = %x41-5A / %x61-7A
	DIGIT = %x30-39		DIGIT = %x30-39
	The properties "code_challenge" and "code_verifier" are adopted from		The properties code_challenge and code_verifier are adopted from the
	the OAuth 2.0 extension known as "Proof-Key for Code Exchange", or		OAuth 2.0 extension known as "Proof-Key for Code Exchange", or PKCE
	PKCE ([RFC7636]) where this technique was originally developed.		([RFC7636]) where this technique was originally developed.
	Clients MUST use "code_challenge" and "code_verifier" and		Clients MUST use code_challenge and code_verifier and authorization
	authorization servers MUST enforce their use except under the		servers MUST enforce their use except under the conditions described
	conditions described in Section 7.8. In this case, using and		in Section 7.8. In this case, using and enforcing code_challenge and
	enforcing "code_challenge" and "code_verifier" as described in the		code_verifier as described in the following is still RECOMMENDED.
	following is still RECOMMENDED.
	The client directs the resource owner to the constructed URI using an		The client directs the resource owner to the constructed URI using an
	HTTP redirection, or by other means available to it via the user		HTTP redirection, or by other means available to it via the user
	agent.		agent.
	For example, the client directs the user agent to make the following		For example, the client directs the user agent to make the following
	HTTP request using TLS (with extra line breaks for display purposes		HTTP request using TLS (with extra line breaks for display purposes
	only):		only):
	GET /authorize?response_type=code&client_id=s6BhdRkqt3&state=xyz		GET /authorize?response_type=code&client_id=s6BhdRkqt3&state=xyz
	&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb		&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
	&code_challenge=6fdkQaPm51l13DSukcAH3Mdx7_ntecHYd1vi3n0hMZY		&code_challenge=6fdkQaPm51l13DSukcAH3Mdx7_ntecHYd1vi3n0hMZY
	&code_challenge_method=S256 HTTP/1.1		&code_challenge_method=S256 HTTP/1.1
	Host: server.example.com		Host: server.example.com
	The authorization server validates the request to ensure that all		The authorization server validates the request to ensure that all
	required parameters are present and valid.		required parameters are present and valid.
	In particular, the authorization server MUST validate the		In particular, the authorization server MUST validate the
	"redirect_uri" in the request if present, ensuring that it matches		redirect_uri in the request if present, ensuring that it matches one
	one of the registered redirect URIs previously established during		of the registered redirect URIs previously established during client
	client registration (Section 2). When comparing the two URIs the		registration (Section 2). When comparing the two URIs the
	authorization server MUST using simple character-by-character string		authorization server MUST using simple character-by-character string
	comparison as defined in [RFC3986], Section 6.2.1.		comparison as defined in [RFC3986], Section 6.2.1.
	If the request is valid, the authorization server authenticates the		If the request is valid, the authorization server authenticates the
	resource owner and obtains an authorization decision (by asking the		resource owner and obtains an authorization decision (by asking the
	resource owner or by establishing approval via other means).		resource owner or by establishing approval via other means).
	When a decision is established, the authorization server directs the		When a decision is established, the authorization server directs the
	user agent to the provided client redirect URI using an HTTP		user agent to the provided client redirect URI using an HTTP
	redirection response, or by other means available to it via the user		redirection response, or by other means available to it via the user
	agent.		agent.
	4.1.2. Authorization Response		4.1.2. Authorization Response
	If the resource owner grants the access request, the authorization		If the resource owner grants the access request, the authorization
	server issues an authorization code and delivers it to the client by		server issues an authorization code and delivers it to the client by
	adding the following parameters to the query component of the		adding the following parameters to the query component of the
	redirect URI using the "application/x-www-form-urlencoded" format,		redirect URI using the application/x-www-form-urlencoded format, per
	per Appendix B:		Appendix B:
	"code": REQUIRED. The authorization code generated by the		"code": REQUIRED. The authorization code generated by the
	authorization server. The authorization code MUST expire shortly		authorization server and is opqaue to the client. The
	after it is issued to mitigate the risk of leaks. A maximum		authorization code MUST expire shortly after it is issued to
	authorization code lifetime of 10 minutes is RECOMMENDED. The		mitigate the risk of leaks. A maximum authorization code lifetime
	client MUST NOT use the authorization code more than once. If an		of 10 minutes is RECOMMENDED. The client MUST NOT use the
	authorization code is used more than once, the authorization		authorization code more than once. If an authorization code is
	server MUST deny the request and SHOULD revoke (when possible) all		used more than once, the authorization server MUST deny the
	access tokens and refresh tokens previously issued based on that		request and SHOULD revoke (when possible) all access tokens and
	authorization code. The authorization code is bound to the client		refresh tokens previously issued based on that authorization code.
	identifier and redirect URI.		The authorization code is bound to the client identifier, code
			challenge and redirect URI.
	"state": REQUIRED if the "state" parameter was present in the client		"state": REQUIRED if the state parameter was present in the client
	authorization request. The exact value received from the client.		authorization request. The exact value received from the client.
	For example, the authorization server redirects the user agent by		For example, the authorization server redirects the user agent by
	sending the following HTTP response:		sending the following HTTP response:
	HTTP/1.1 302 Found		HTTP/1.1 302 Found
	Location: https://client.example.com/cb?code=SplxlOBeZQQYbYS6WxSbIA		Location: https://client.example.com/cb?code=SplxlOBeZQQYbYS6WxSbIA
	&state=xyz		&state=xyz
	The client MUST ignore unrecognized response parameters. The		The client MUST ignore unrecognized response parameters. The
	authorization code string size is left undefined by this		authorization code string size is left undefined by this
	specification. The client should avoid making assumptions about code		specification. The client should avoid making assumptions about code
	value sizes. The authorization server SHOULD document the size of		value sizes. The authorization server SHOULD document the size of
	any value it issues.		any value it issues.
	The authorization server MUST associate the "code_challenge" and		The authorization server MUST associate the code_challenge and
	"code_challenge_method" values with the issued authorization code so		code_challenge_method values with the issued authorization code so
	the code challenge can be verified later.		the code challenge can be verified later.
	The exact method that the server uses to associate the		The exact method that the server uses to associate the code_challenge
	"code_challenge" with the issued code is out of scope for this		with the issued code is out of scope for this specification. The
	specification. The code challenge could be stored on the server and		code challenge could be stored on the server and associated with the
	associated with the code there. The "code_challenge" and		code there. The code_challenge and code_challenge_method values may
	"code_challenge_method" values may be stored in encrypted form in the		be stored in encrypted form in the code itself, but the server MUST
	code itself, but the server MUST NOT include the "code_challenge"		NOT include the code_challenge value in a response parameter in a
	value in a response parameter in a form that entities other than the		form that entities other than the AS can extract.
	AS can extract.
	4.1.2.1. Error Response		4.1.2.1. Error Response
	If the request fails due to a missing, invalid, or mismatching		If the request fails due to a missing, invalid, or mismatching
	redirect URI, or if the client identifier is missing or invalid, the		redirect URI, or if the client identifier is missing or invalid, the
	authorization server SHOULD inform the resource owner of the error		authorization server SHOULD inform the resource owner of the error
	and MUST NOT automatically redirect the user agent to the invalid		and MUST NOT automatically redirect the user agent to the invalid
	redirect URI.		redirect URI.
	An AS MUST reject requests without a "code_challenge" from public		An AS MUST reject requests without a code_challenge from public
	clients, and MUST reject such requests from other clients unless		clients, and MUST reject such requests from other clients unless
	there is reasonable assurance that the client mitigates authorization		there is reasonable assurance that the client mitigates authorization
	code injection in other ways. See Section 7.8 for details.		code injection in other ways. See Section 7.8 for details.
	If the server does not support the requested "code_challenge_method"		If the server does not support the requested code_challenge_method
	transformation, the authorization endpoint MUST return the		transformation, the authorization endpoint MUST return the
	authorization error response with "error" value set to		authorization error response with error value set to invalid_request.
	"invalid_request". The "error_description" or the response of		The error_description or the response of error_uri SHOULD explain the
	"error_uri" SHOULD explain the nature of error, e.g., transform		nature of error, e.g., transform algorithm not supported.
	algorithm not supported.
	If the resource owner denies the access request or if the request		If the resource owner denies the access request or if the request
	fails for reasons other than a missing or invalid redirect URI, the		fails for reasons other than a missing or invalid redirect URI, the
	authorization server informs the client by adding the following		authorization server informs the client by adding the following
	parameters to the query component of the redirect URI using the		parameters to the query component of the redirect URI using the
	"application/x-www-form-urlencoded" format, per Appendix B:		application/x-www-form-urlencoded format, per Appendix B:
	"error": REQUIRED. A single ASCII [USASCII] error code from the		"error": REQUIRED. A single ASCII [USASCII] error code from the
	following:		following:
	"invalid_request": The request is missing a required parameter,		"invalid_request": The request is missing a required parameter,
	includes an invalid parameter value, includes a parameter more		includes an invalid parameter value, includes a parameter more
	than once, or is otherwise malformed.		than once, or is otherwise malformed.
	"unauthorized_client": The client is not authorized to request an		"unauthorized_client": The client is not authorized to request an
	authorization code using this method.		authorization code using this method.
	skipping to change at page 34, line 49 ¶		skipping to change at page 34, line 42 ¶
	request. (This error code is needed because a 500 Internal		request. (This error code is needed because a 500 Internal
	Server Error HTTP status code cannot be returned to the client		Server Error HTTP status code cannot be returned to the client
	via an HTTP redirect.)		via an HTTP redirect.)
	"temporarily_unavailable": The authorization server is currently		"temporarily_unavailable": The authorization server is currently
	unable to handle the request due to a temporary overloading or		unable to handle the request due to a temporary overloading or
	maintenance of the server. (This error code is needed because		maintenance of the server. (This error code is needed because
	a 503 Service Unavailable HTTP status code cannot be returned		a 503 Service Unavailable HTTP status code cannot be returned
	to the client via an HTTP redirect.)		to the client via an HTTP redirect.)
	Values for the "error" parameter MUST NOT include characters		Values for the error parameter MUST NOT include characters outside
	outside the set %x20-21 / %x23-5B / %x5D-7E.		the set %x20-21 / %x23-5B / %x5D-7E.
	"error_description": OPTIONAL. Human-readable ASCII [USASCII] text		"error_description": OPTIONAL. Human-readable ASCII [USASCII] text
	providing additional information, used to assist the client		providing additional information, used to assist the client
	developer in understanding the error that occurred. Values for		developer in understanding the error that occurred. Values for
	the "error_description" parameter MUST NOT include characters		the error_description parameter MUST NOT include characters
	outside the set %x20-21 / %x23-5B / %x5D-7E.		outside the set %x20-21 / %x23-5B / %x5D-7E.
	"error_uri": OPTIONAL. A URI identifying a human-readable web page		"error_uri": OPTIONAL. A URI identifying a human-readable web page
	with information about the error, used to provide the client		with information about the error, used to provide the client
	developer with additional information about the error. Values for		developer with additional information about the error. Values for
	the "error_uri" parameter MUST conform to the URI-reference syntax		the error_uri parameter MUST conform to the URI-reference syntax
	and thus MUST NOT include characters outside the set %x21 /		and thus MUST NOT include characters outside the set %x21 /
	%x23-5B / %x5D-7E.		%x23-5B / %x5D-7E.
	"state": REQUIRED if a "state" parameter was present in the client		"state": REQUIRED if a state parameter was present in the client
	authorization request. The exact value received from the client.		authorization request. The exact value received from the client.
	For example, the authorization server redirects the user agent by		For example, the authorization server redirects the user agent by
	sending the following HTTP response:		sending the following HTTP response:
	HTTP/1.1 302 Found		HTTP/1.1 302 Found
	Location: https://client.example.com/cb?error=access_denied&state=xyz		Location: https://client.example.com/cb?error=access_denied&state=xyz
	4.1.3. Token Endpoint Extension		4.1.3. Token Endpoint Extension
	The authorization grant type is identified at the token endpoint with		The authorization grant type is identified at the token endpoint with
	the "grant_type" value of "authorization_code".		the grant_type value of authorization_code.
	If this value is set, the following additional token request		If this value is set, the following additional token request
	parameters beyond Section 3.2.2 are required:		parameters beyond Section 3.2.2 are required:
	"code": REQUIRED. The authorization code received from the		"code": REQUIRED. The authorization code received from the
	authorization server.		authorization server.
	"redirect_uri": REQUIRED, if the "redirect_uri" parameter was		"redirect_uri": REQUIRED, if the redirect_uri parameter was included
	included in the authorization request as described in		in the authorization request as described in Section 4.1.1, and
	Section 4.1.1, and their values MUST be identical.		their values MUST be identical.
	"code_verifier": REQUIRED, if the "code_challenge" parameter was		"code_verifier": REQUIRED, if the code_challenge parameter was
	included in the authorization request. MUST NOT be used		included in the authorization request. MUST NOT be used
	otherwise. The original code verifier string.		otherwise. The original code verifier string.
	For example, the client makes the following HTTP request using TLS		For example, the client makes the following HTTP request using TLS
	(with extra line breaks for display purposes only):		(with extra line breaks for display purposes only):
	POST /token HTTP/1.1		POST /token HTTP/1.1
	Host: server.example.com		Host: server.example.com
	Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW		Authorization: Basic czZCaGRSa3F0MzpnWDFmQmF0M2JW
	Content-Type: application/x-www-form-urlencoded		Content-Type: application/x-www-form-urlencoded
	grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA		grant_type=authorization_code&code=SplxlOBeZQQYbYS6WxSbIA
	&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb		&redirect_uri=https%3A%2F%2Fclient%2Eexample%2Ecom%2Fcb
	&code_verifier=3641a2d12d66101249cdf7a79c000c1f8c05d2aafcf14bf146497bed		&code_verifier=3641a2d12d66101249cdf7a79c000c1f8c05d2aafcf14bf146497bed
	In addition to the processing rules in Section 3.2.2, the		In addition to the processing rules in Section 3.2.2, the
	authorization server MUST:		authorization server MUST:
	* ensure that the authorization code was issued to the authenticated		* ensure that the authorization code was issued to the authenticated
	confidential or credentialed client, or if the client is public,		confidential or credentialed client, or if the client is public,
	ensure that the code was issued to "client_id" in the request,		ensure that the code was issued to client_id in the request,
	* verify that the authorization code is valid,		* verify that the authorization code is valid,
	* verify that the "code_verifier" parameter is present if and only		* verify that the code_verifier parameter is present if and only if
	if a "code_challenge" parameter was present in the authorization		a code_challenge parameter was present in the authorization
	request,		request,
	* if a "code_verifier" is present, verify the "code_verifier" by		* if a code_verifier is present, verify the code_verifier by
	calculating the code challenge from the received "code_verifier"		calculating the code challenge from the received code_verifier and
	and comparing it with the previously associated "code_challenge",		comparing it with the previously associated code_challenge, after
	after first transforming it according to the		first transforming it according to the code_challenge_method
	"code_challenge_method" method specified by the client, and		method specified by the client, and
	* ensure that the "redirect_uri" parameter is present if the		* ensure that the redirect_uri parameter is present if the
	"redirect_uri" parameter was included in the initial authorization		redirect_uri parameter was included in the initial authorization
	request as described in Section 4.1.1, and if included ensure that		request as described in Section 4.1.1, and if included ensure that
	their values are identical.		their values are identical.
	4.2. Client Credentials Grant		4.2. Client Credentials Grant
	The client can request an access token using only its client		The client can request an access token using only its client
	credentials (or other supported means of authentication) when the		credentials (or other supported means of authentication) when the
	client is requesting access to the protected resources under its		client is requesting access to the protected resources under its
	control, or those of another resource owner that have been previously		control, or those of another resource owner that have been previously
	arranged with the authorization server (the method of which is beyond		arranged with the authorization server (the method of which is beyond
	skipping to change at page 37, line 27 ¶		skipping to change at page 37, line 11 ¶
	(1) The client authenticates with the authorization server and		(1) The client authenticates with the authorization server and
	requests an access token from the token endpoint.		requests an access token from the token endpoint.
	(2) The authorization server authenticates the client, and if valid,		(2) The authorization server authenticates the client, and if valid,
	issues an access token.		issues an access token.
	4.2.1. Token Endpoint Extension		4.2.1. Token Endpoint Extension
	The authorization grant type is identified at the token endpoint with		The authorization grant type is identified at the token endpoint with
	the "grant_type" value of "client_credentials".		the grant_type value of client_credentials.
	If this value is set, no additional parameters beyond Section 3.2.2		If this value is set, no additional parameters beyond Section 3.2.2
	are required/supported:		are required/supported:
	For example, the client makes the following HTTP request using		For example, the client makes the following HTTP request using
	transport-layer security (with extra line breaks for display purposes		transport-layer security (with extra line breaks for display purposes
	only):		only):
	POST /token HTTP/1.1		POST /token HTTP/1.1
	Host: server.example.com		Host: server.example.com
	skipping to change at page 38, line 18 ¶		skipping to change at page 37, line 42 ¶
	to a client, which can be used to obtain new (fresh) access tokens		to a client, which can be used to obtain new (fresh) access tokens
	based on an existing grant. The client uses this option either		based on an existing grant. The client uses this option either
	because the previous access token has expired or the client		because the previous access token has expired or the client
	previously obtained an access token with a scope more narrow than		previously obtained an access token with a scope more narrow than
	approved by the respective grant and later requires an access token		approved by the respective grant and later requires an access token
	with a different scope under the same grant.		with a different scope under the same grant.
	4.3.1. Token Endpoint Extension		4.3.1. Token Endpoint Extension
	The authorization grant type is identified at the token endpoint with		The authorization grant type is identified at the token endpoint with
	the "grant_type" value of "refresh_token".		the grant_type value of refresh_token.
	If this value is set, the following additional parameters beyond		If this value is set, the following additional parameters beyond
	Section 3.2.2 are required/supported:		Section 3.2.2 are required/supported:
	"refresh_token": REQUIRED. The refresh token issued to the client.		"refresh_token": REQUIRED. The refresh token issued to the client.
	Because refresh tokens are typically long-lasting credentials used to		Because refresh tokens are typically long-lasting credentials used to
	request additional access tokens, the refresh token is bound to the		request additional access tokens, the refresh token is bound to the
	client to which it was issued. Confidential or credentialed clients		client to which it was issued. Confidential or credentialed clients
	MUST authenticate with the authorization server as described in		MUST authenticate with the authorization server as described in
	skipping to change at page 40, line 4 ¶		skipping to change at page 39, line 32 ¶
	issuing a new refresh token to the client. If a new refresh token is		issuing a new refresh token to the client. If a new refresh token is
	issued, the refresh token scope MUST be identical to that of the		issued, the refresh token scope MUST be identical to that of the
	refresh token included by the client in the request.		refresh token included by the client in the request.
	Authorization servers MAY revoke refresh tokens automatically in case		Authorization servers MAY revoke refresh tokens automatically in case
	of a security event, such as:		of a security event, such as:
	* password change		* password change
	* logout at the authorization server		* logout at the authorization server
	Refresh tokens SHOULD expire if the client has been inactive for some		Refresh tokens SHOULD expire if the client has been inactive for some
	time, i.e., the refresh token has not been used to obtain new access		time, i.e., the refresh token has not been used to obtain new access
	tokens for some time. The expiration time is at the discretion of		tokens for some time. The expiration time is at the discretion of
	the authorization server. It might be a global value or determined		the authorization server. It might be a global value or determined
	based on the client policy or the grant associated with the refresh		based on the client policy or the grant associated with the refresh
	token (and its sensitivity).		token (and its sensitivity).
	4.4. Extension Grants		4.4. Extension Grants
	The client uses an extension grant type by specifying the grant type		The client uses an extension grant type by specifying the grant type
	using an absolute URI (defined by the authorization server) as the		using an absolute URI (defined by the authorization server) as the
	value of the "grant_type" parameter of the token endpoint, and by		value of the grant_type parameter of the token endpoint, and by
	adding any additional parameters necessary.		adding any additional parameters necessary.
	For example, to request an access token using the Device		For example, to request an access token using the Device
	Authorization Grant as defined by [RFC8628] after the user has		Authorization Grant as defined by [RFC8628] after the user has
	authorized the client on a separate device, the client makes the		authorized the client on a separate device, the client makes the
	following HTTP request using TLS (with extra line breaks for display		following HTTP request using TLS (with extra line breaks for display
	purposes only):		purposes only):
	POST /token HTTP/1.1		POST /token HTTP/1.1
	Host: server.example.com		Host: server.example.com
	skipping to change at page 41, line 24 ¶		skipping to change at page 40, line 38 ¶
	authorization server. For example, when the resource server and		authorization server. For example, when the resource server and
	authorization server are colocated or are part of the same system,		authorization server are colocated or are part of the same system,
	they may share a database or other storage; when the two components		they may share a database or other storage; when the two components
	are operated independently, they may use Token Introspection		are operated independently, they may use Token Introspection
	[RFC7662] or a structured access token format such as a JWT		[RFC7662] or a structured access token format such as a JWT
	[I-D.ietf-oauth-access-token-jwt].		[I-D.ietf-oauth-access-token-jwt].
	The method in which the client utilizes the access token to access		The method in which the client utilizes the access token to access
	protected resources at the resource server depends on the type of		protected resources at the resource server depends on the type of
	access token issued by the authorization server. Typically, it		access token issued by the authorization server. Typically, it
	involves using the HTTP "Authorization" request header field		involves using the HTTP Authorization request header field [RFC7235]
	[RFC7235] with an authentication scheme defined by the specification		with an authentication scheme defined by the specification of the
	of the access token type used, such as "Bearer", defined below.		access token type used, such as Bearer, defined below.
	5.1. Access Token Types		5.1. Access Token Types
	The access token type provides the client with the information		The access token type provides the client with the information
	required to successfully utilize the access token to make a protected		required to successfully utilize the access token to make a protected
	resource request (along with type-specific attributes). The client		resource request (along with type-specific attributes). The client
	MUST NOT use an access token if it does not understand the token		MUST NOT use an access token if it does not understand the token
	type.		type.
	For example, the "Bearer" token type defined in this specification is		For example, the Bearer token type defined in this specification is
	utilized by simply including the access token string in the request:		utilized by simply including the access token string in the request:
	GET /resource/1 HTTP/1.1		GET /resource/1 HTTP/1.1
	Host: example.com		Host: example.com
	Authorization: Bearer mF_9.B5f-4.1JqM		Authorization: Bearer mF_9.B5f-4.1JqM
	The above example is provided for illustration purposes only.		The above example is provided for illustration purposes only.
	Each access token type definition specifies the additional attributes		Each access token type definition specifies the additional attributes
	(if any) sent to the client together with the "access_token" response		(if any) sent to the client together with the access_token response
	parameter. It also defines the HTTP authentication method used to		parameter. It also defines the HTTP authentication method used to
	include the access token when making a protected resource request.		include the access token when making a protected resource request.
	5.2. Bearer Tokens		5.2. Bearer Tokens
	A Bearer Token is a security token with the property that any party		A Bearer Token is a security token with the property that any party
	in possession of the token (a "bearer") can use the token in any way		in possession of the token (a "bearer") can use the token in any way
	that any other party in possession of it can. Using a bearer token		that any other party in possession of it can. Using a bearer token
	does not require a bearer to prove possession of cryptographic key		does not require a bearer to prove possession of cryptographic key
	material (proof-of-possession).		material (proof-of-possession).
	Bearer tokens may be extended to include proof-of-possession		Bearer tokens may be enhanced with proof-of-possession specifications
	techniques by other specifications.		such as mTLS [RFC8705] to provide proof-of-possession
			characteristics.
	5.2.1. Authenticated Requests		5.2.1. Authenticated Requests
	This section defines two methods of sending Bearer tokens in resource		This section defines two methods of sending Bearer tokens in resource
	requests to resource servers. Clients MUST NOT use more than one		requests to resource servers. Clients MUST use one of the two
	method to transmit the token in each request.		methods defined below, and MUST NOT use more than one method to
			transmit the token in each request.
			In particular, clients MUST NOT send the access token in a URI query
			parameter, and resource servers MUST ignore access tokens in a URI
			query parameter.
	5.2.1.1. Authorization Request Header Field		5.2.1.1. Authorization Request Header Field
	When sending the access token in the "Authorization" request header		When sending the access token in the Authorization request header
	field defined by HTTP/1.1 [RFC7235], the client uses the "Bearer"		field defined by HTTP/1.1 [RFC7235], the client uses the Bearer
	authentication scheme to transmit the access token.		authentication scheme to transmit the access token.
	For example:		For example:
	GET /resource HTTP/1.1		GET /resource HTTP/1.1
	Host: server.example.com		Host: server.example.com
	Authorization: Bearer mF_9.B5f-4.1JqM		Authorization: Bearer mF_9.B5f-4.1JqM
	The syntax of the "Authorization" header field for this scheme		The syntax of the Authorization header field for this scheme follows
	follows the usage of the Basic scheme defined in Section 2 of		the usage of the Basic scheme defined in Section 2 of [RFC2617].
	[RFC2617]. Note that, as with Basic, it does not conform to the		Note that, as with Basic, it does not conform to the generic syntax
	generic syntax defined in Section 1.2 of [RFC2617] but is compatible		defined in Section 1.2 of [RFC2617] but is compatible with the
	with the general authentication framework in HTTP 1.1 Authentication		general authentication framework in HTTP 1.1 Authentication
	[RFC7235], although it does not follow the preferred practice		[RFC7235], although it does not follow the preferred practice
	outlined therein in order to reflect existing deployments. The		outlined therein in order to reflect existing deployments. The
	syntax for Bearer credentials is as follows:		syntax for Bearer credentials is as follows:
	b64token = 1*( ALPHA / DIGIT /		b64token = 1*( ALPHA / DIGIT /
	"-" / "." / "_" / "~" / "+" / "/" ) *"="		"-" / "." / "_" / "~" / "+" / "/" ) *"="
	credentials = "Bearer" 1*SP b64token		credentials = "Bearer" 1*SP b64token
	Clients SHOULD make authenticated requests with a bearer token using		Clients SHOULD make authenticated requests with a bearer token using
	the "Authorization" request header field with the "Bearer" HTTP		the Authorization request header field with the Bearer HTTP
	authorization scheme. Resource servers MUST support this method.		authorization scheme. Resource servers MUST support this method.
	5.2.1.2. Form-Encoded Body Parameter		5.2.1.2. Form-Encoded Body Parameter
	When sending the access token in the HTTP request payload, the client		When sending the access token in the HTTP request payload, the client
	adds the access token to the request-body using the "access_token"		adds the access token to the request-body using the access_token
	parameter. The client MUST NOT use this method unless all of the		parameter. The client MUST NOT use this method unless all of the
	following conditions are met:		following conditions are met:
	* The HTTP request entity-header includes the "Content-Type" header		* The HTTP request entity-header includes the Content-Type header
	field set to "application/x-www-form-urlencoded".		field set to application/x-www-form-urlencoded.
	* The payload follows the encoding requirements of the "application/		* The payload follows the encoding requirements of the application/
	x-www-form-urlencoded" content-type as defined by HTML 4.01		x-www-form-urlencoded content-type as defined by HTML 4.01
	[W3C.REC-html401-19991224].		[W3C.REC-html401-19991224].
	* The HTTP request payload is single-part.		* The HTTP request payload is single-part.
	* The content to be encoded in the payload MUST consist entirely of		* The content to be encoded in the payload MUST consist entirely of
	ASCII [USASCII] characters.		ASCII [USASCII] characters.
	* The HTTP request method is one for which the request-body has		* The HTTP request method is one for which the request-body has
	defined semantics. In particular, this means that the "GET"		defined semantics. In particular, this means that the GET method
	method MUST NOT be used.		MUST NOT be used.
	The payload MAY include other request-specific parameters, in which		The payload MAY include other request-specific parameters, in which
	case the "access_token" parameter MUST be properly separated from the		case the access_token parameter MUST be properly separated from the
	request-specific parameters using "&" character(s) (ASCII code 38).		request-specific parameters using & character(s) (ASCII code 38).
	For example, the client makes the following HTTP request using		For example, the client makes the following HTTP request using
	transport-layer security:		transport-layer security:
	POST /resource HTTP/1.1		POST /resource HTTP/1.1
	Host: server.example.com		Host: server.example.com
	Content-Type: application/x-www-form-urlencoded		Content-Type: application/x-www-form-urlencoded
	access_token=mF_9.B5f-4.1JqM		access_token=mF_9.B5f-4.1JqM
	The "application/x-www-form-urlencoded" method SHOULD NOT be used		The application/x-www-form-urlencoded method SHOULD NOT be used
	except in application contexts where participating clients do not		except in application contexts where participating clients do not
	have access to the "Authorization" request header field. Resource		have access to the Authorization request header field. Resource
	servers MAY support this method.		servers MAY support this method.
	5.2.2. The WWW-Authenticate Response Header Field		5.2.2. The WWW-Authenticate Response Header Field
	If the protected resource request does not include authentication		If the protected resource request does not include authentication
	credentials or does not contain an access token that enables access		credentials or does not contain an access token that enables access
	to the protected resource, the resource server MUST include the HTTP		to the protected resource, the resource server MUST include the HTTP
	"WWW-Authenticate" response header field; it MAY include it in		WWW-Authenticate response header field; it MAY include it in response
	response to other conditions as well. The "WWW-Authenticate" header		to other conditions as well. The WWW-Authenticate header field uses
	field uses the framework defined by HTTP/1.1 [RFC7235].		the framework defined by HTTP/1.1 [RFC7235].
	All challenges for this token type MUST use the auth-scheme value		All challenges for this token type MUST use the auth-scheme value
	"Bearer". This scheme MUST be followed by one or more auth-param		Bearer. This scheme MUST be followed by one or more auth-param
	values. The auth-param attributes used or defined by this		values. The auth-param attributes used or defined by this
	specification for this token type are as follows. Other auth-param		specification for this token type are as follows. Other auth-param
	attributes MAY be used as well.		attributes MAY be used as well.
	A "realm" attribute MAY be included to indicate the scope of		A realm attribute MAY be included to indicate the scope of protection
	protection in the manner described in HTTP/1.1 [RFC7235]. The		in the manner described in HTTP/1.1 [RFC7235]. The realm attribute
	"realm" attribute MUST NOT appear more than once.		MUST NOT appear more than once.
	The "scope" attribute is defined in Section 3.2.2.1. The "scope"		The scope attribute is defined in Section 3.2.2.1. The scope
	attribute is a space-delimited list of case-sensitive scope values		attribute is a space-delimited list of case-sensitive scope values
	indicating the required scope of the access token for accessing the		indicating the required scope of the access token for accessing the
	requested resource. "scope" values are implementation defined; there		requested resource. scope values are implementation defined; there is
	is no centralized registry for them; allowed values are defined by		no centralized registry for them; allowed values are defined by the
	the authorization server. The order of "scope" values is not		authorization server. The order of scope values is not significant.
	significant. In some cases, the "scope" value will be used when		In some cases, the scope value will be used when requesting a new
	requesting a new access token with sufficient scope of access to		access token with sufficient scope of access to utilize the protected
	utilize the protected resource. Use of the "scope" attribute is		resource. Use of the scope attribute is OPTIONAL. The scope
	OPTIONAL. The "scope" attribute MUST NOT appear more than once. The		attribute MUST NOT appear more than once. The scope value is
	"scope" value is intended for programmatic use and is not meant to be		intended for programmatic use and is not meant to be displayed to
	displayed to end-users.		end-users.
	Two example scope values follow; these are taken from the OpenID		Two example scope values follow; these are taken from the OpenID
	Connect [OpenID.Messages] and the Open Authentication Technology		Connect [OpenID.Messages] and the Open Authentication Technology
	Committee (OATC) Online Multimedia Authorization Protocol [OMAP]		Committee (OATC) Online Multimedia Authorization Protocol [OMAP]
	OAuth 2.0 use cases, respectively:		OAuth 2.0 use cases, respectively:
	scope="openid profile email"		scope="openid profile email"
	scope="urn:example:channel=HBO&urn:example:rating=G,PG-13"		scope="urn:example:channel=HBO&urn:example:rating=G,PG-13"
	If the protected resource request included an access token and failed		If the protected resource request included an access token and failed
	authentication, the resource server SHOULD include the "error"		authentication, the resource server SHOULD include the error
	attribute to provide the client with the reason why the access		attribute to provide the client with the reason why the access
	request was declined. The parameter value is described in		request was declined. The parameter value is described in
	Section 5.2.3. In addition, the resource server MAY include the		Section 5.2.3. In addition, the resource server MAY include the
	"error_description" attribute to provide developers a human-readable		error_description attribute to provide developers a human-readable
	explanation that is not meant to be displayed to end-users. It also		explanation that is not meant to be displayed to end-users. It also
	MAY include the "error_uri" attribute with an absolute URI		MAY include the error_uri attribute with an absolute URI identifying
	identifying a human-readable web page explaining the error. The		a human-readable web page explaining the error. The error,
	"error", "error_description", and "error_uri" attributes MUST NOT		error_description, and error_uri attributes MUST NOT appear more than
	appear more than once.		once.
	Values for the "scope" attribute (specified in Appendix A.4) MUST NOT		Values for the scope attribute (specified in Appendix A.4) MUST NOT
	include characters outside the set %x21 / %x23-5B / %x5D-7E for		include characters outside the set %x21 / %x23-5B / %x5D-7E for
	representing scope values and %x20 for delimiters between scope		representing scope values and %x20 for delimiters between scope
	values. Values for the "error" and "error_description" attributes		values. Values for the error and error_description attributes
	(specified in Appendixes A.7 and A.8) MUST NOT include characters		(specified in Appendixes A.7 and A.8) MUST NOT include characters
	outside the set %x20-21 / %x23-5B / %x5D-7E. Values for the		outside the set %x20-21 / %x23-5B / %x5D-7E. Values for the
	"error_uri" attribute (specified in Appendix A.9 of) MUST conform to		error_uri attribute (specified in Appendix A.9 of) MUST conform to
	the URI-reference syntax and thus MUST NOT include characters outside		the URI-reference syntax and thus MUST NOT include characters outside
	the set %x21 / %x23-5B / %x5D-7E.		the set %x21 / %x23-5B / %x5D-7E.
	For example, in response to a protected resource request without		For example, in response to a protected resource request without
	authentication:		authentication:
	HTTP/1.1 401 Unauthorized		HTTP/1.1 401 Unauthorized
	WWW-Authenticate: Bearer realm="example"		WWW-Authenticate: Bearer realm="example"
	And in response to a protected resource request with an		And in response to a protected resource request with an
	skipping to change at page 45, line 50 ¶		skipping to change at page 45, line 15 ¶
	same parameter, uses more than one method for including an access		same parameter, uses more than one method for including an access
	token, or is otherwise malformed. The resource server SHOULD		token, or is otherwise malformed. The resource server SHOULD
	respond with the HTTP 400 (Bad Request) status code.		respond with the HTTP 400 (Bad Request) status code.
	"invalid_token": The access token provided is expired, revoked,		"invalid_token": The access token provided is expired, revoked,
	malformed, or invalid for other reasons. The resource SHOULD		malformed, or invalid for other reasons. The resource SHOULD
	respond with the HTTP 401 (Unauthorized) status code. The client		respond with the HTTP 401 (Unauthorized) status code. The client
	MAY request a new access token and retry the protected resource		MAY request a new access token and retry the protected resource
	request.		request.
	"insufficient_scope": The request requires higher privileges than		"insufficient_scope": The request requires higher privileges
	provided by the access token. The resource server SHOULD respond		(scopes) than provided by the scopes granted to the client and
	with the HTTP 403 (Forbidden) status code and MAY include the		represented by the access token.
	"scope" attribute with the scope necessary to access the protected
	resource.		The resource server SHOULD respond with the HTTP 403 (Forbidden)
			status code and MAY include the scope attribute with the scope
			necessary to access the protected resource.
	If the request lacks any authentication information (e.g., the client		If the request lacks any authentication information (e.g., the client
	was unaware that authentication is necessary or attempted using an		was unaware that authentication is necessary or attempted using an
	unsupported authentication method), the resource server SHOULD NOT		unsupported authentication method), the resource server SHOULD NOT
	include an error code or other error information.		include an error code or other error information.
	For example:		For example:
	HTTP/1.1 401 Unauthorized		HTTP/1.1 401 Unauthorized
	WWW-Authenticate: Bearer realm="example"		WWW-Authenticate: Bearer realm="example"
	skipping to change at page 46, line 39 ¶		skipping to change at page 46, line 7 ¶
	(https://tools.ietf.org/html/rfc6749#section-11.4) for error values		(https://tools.ietf.org/html/rfc6749#section-11.4) for error values
	to be shared among OAuth token authentication schemes.		to be shared among OAuth token authentication schemes.
	New authentication schemes designed primarily for OAuth token		New authentication schemes designed primarily for OAuth token
	authentication SHOULD define a mechanism for providing an error		authentication SHOULD define a mechanism for providing an error
	status code to the client, in which the error values allowed are		status code to the client, in which the error values allowed are
	registered in the error registry established by this specification.		registered in the error registry established by this specification.
	Such schemes MAY limit the set of valid error codes to a subset of		Such schemes MAY limit the set of valid error codes to a subset of
	the registered values. If the error code is returned using a named		the registered values. If the error code is returned using a named
	parameter, the parameter name SHOULD be "error".		parameter, the parameter name SHOULD be error.
	Other schemes capable of being used for OAuth token authentication,		Other schemes capable of being used for OAuth token authentication,
	but not primarily designed for that purpose, MAY bind their error		but not primarily designed for that purpose, MAY bind their error
	values to the registry in the same manner.		values to the registry in the same manner.
	New authentication schemes MAY choose to also specify the use of the		New authentication schemes MAY choose to also specify the use of the
	"error_description" and "error_uri" parameters to return error		error_description and error_uri parameters to return error
	information in a manner parallel to their usage in this		information in a manner parallel to their usage in this
	specification.		specification.
	6. Extensibility		6. Extensibility
	6.1. Defining Access Token Types		6.1. Defining Access Token Types
	Access token types can be defined in one of two ways: registered in		Access token types can be defined in one of two ways: registered in
	the Access Token Types registry (following the procedures in		the Access Token Types registry (following the procedures in
	Section 11.1 of [RFC6749]), or by using a unique absolute URI as its		Section 11.1 of [RFC6749]), or by using a unique absolute URI as its
	name.		name.
	Types utilizing a URI name SHOULD be limited to vendor-specific		Types utilizing a URI name SHOULD be limited to vendor-specific
	implementations that are not commonly applicable, and are specific to		implementations that are not commonly applicable, and are specific to
	the implementation details of the resource server where they are		the implementation details of the resource server where they are
	used.		used.
	All other types MUST be registered. Type names MUST conform to the		All other types MUST be registered. Type names MUST conform to the
	type-name ABNF. If the type definition includes a new HTTP		type-name ABNF. If the type definition includes a new HTTP
	authentication scheme, the type name SHOULD be identical to the HTTP		authentication scheme, the type name SHOULD be identical to the HTTP
	authentication scheme name (as defined by [RFC2617]). The token type		authentication scheme name (as defined by [RFC2617]). The token type
	"example" is reserved for use in examples.		example is reserved for use in examples.
	type-name = 1*name-char		type-name = 1*name-char
	name-char = "-" / "." / "_" / DIGIT / ALPHA		name-char = "-" / "." / "_" / DIGIT / ALPHA
	6.2. Defining New Endpoint Parameters		6.2. Defining New Endpoint Parameters
	New request or response parameters for use with the authorization		New request or response parameters for use with the authorization
	endpoint or the token endpoint are defined and registered in the		endpoint or the token endpoint are defined and registered in the
	OAuth Parameters registry following the procedure in Section 11.2 of		OAuth Parameters registry following the procedure in Section 11.2 of
	[RFC6749].		[RFC6749].
	skipping to change at page 47, line 48 ¶		skipping to change at page 47, line 17 ¶
	Unregistered vendor-specific parameter extensions that are not		Unregistered vendor-specific parameter extensions that are not
	commonly applicable and that are specific to the implementation		commonly applicable and that are specific to the implementation
	details of the authorization server where they are used SHOULD		details of the authorization server where they are used SHOULD
	utilize a vendor-specific prefix that is not likely to conflict with		utilize a vendor-specific prefix that is not likely to conflict with
	other registered values (e.g., begin with 'companyname_').		other registered values (e.g., begin with 'companyname_').
	6.3. Defining New Authorization Grant Types		6.3. Defining New Authorization Grant Types
	New authorization grant types can be defined by assigning them a		New authorization grant types can be defined by assigning them a
	unique absolute URI for use with the "grant_type" parameter. If the		unique absolute URI for use with the grant_type parameter. If the
	extension grant type requires additional token endpoint parameters,		extension grant type requires additional token endpoint parameters,
	they MUST be registered in the OAuth Parameters registry as described		they MUST be registered in the OAuth Parameters registry as described
	by Section 11.2 of [RFC6749].		by Section 11.2 of [RFC6749].
	6.4. Defining New Authorization Endpoint Response Types		6.4. Defining New Authorization Endpoint Response Types
	New response types for use with the authorization endpoint are		New response types for use with the authorization endpoint are
	defined and registered in the Authorization Endpoint Response Types		defined and registered in the Authorization Endpoint Response Types
	registry following the procedure in Section 11.3 of [RFC6749].		registry following the procedure in Section 11.3 of [RFC6749].
	Response type names MUST conform to the response-type ABNF.		Response type names MUST conform to the response-type ABNF.
	response-type = response-name *( SP response-name )		response-type = response-name *( SP response-name )
	response-name = 1*response-char		response-name = 1*response-char
	response-char = "_" / DIGIT / ALPHA		response-char = "_" / DIGIT / ALPHA
	If a response type contains one or more space characters (%x20), it		If a response type contains one or more space characters (%x20), it
	is compared as a space-delimited list of values in which the order of		is compared as a space-delimited list of values in which the order of
	values does not matter. Only one order of values can be registered,		values does not matter. Only one order of values can be registered,
	which covers all other arrangements of the same set of values.		which covers all other arrangements of the same set of values.
	For example, an extension can define and register the "code		For example, an extension can define and register the code
	other_token" response type. Once registered, the same combination		other_token response type. Once registered, the same combination
	cannot be registered as "other_token code", but both values can be		cannot be registered as other_token code, but both values can be used
	used to denote the same response type.		to denote the same response type.
	6.5. Defining Additional Error Codes		6.5. Defining Additional Error Codes
	In cases where protocol extensions (i.e., access token types,		In cases where protocol extensions (i.e., access token types,
	extension parameters, or extension grant types) require additional		extension parameters, or extension grant types) require additional
	error codes to be used with the authorization code grant error		error codes to be used with the authorization code grant error
	response (Section 4.1.2.1), the token error response		response (Section 4.1.2.1), the token error response
	(Section 3.2.3.1), or the resource access error response		(Section 3.2.3.1), or the resource access error response
	(Section 5.3), such error codes MAY be defined.		(Section 5.3), such error codes MAY be defined.
	Extension error codes MUST be registered (following the procedures in		Extension error codes MUST be registered (following the procedures in
	Section 11.4 of [RFC6749]) if the extension they are used in		Section 11.4 of [RFC6749]) if the extension they are used in
	conjunction with is a registered access token type, a registered		conjunction with is a registered access token type, a registered
	endpoint parameter, or an extension grant type. Error codes used		endpoint parameter, or an extension grant type. Error codes used
	with unregistered extensions MAY be registered.		with unregistered extensions MAY be registered.
	Error codes MUST conform to the error ABNF and SHOULD be prefixed by		Error codes MUST conform to the error ABNF and SHOULD be prefixed by
	an identifying name when possible. For example, an error identifying		an identifying name when possible. For example, an error identifying
	an invalid value set to the extension parameter "example" SHOULD be		an invalid value set to the extension parameter example SHOULD be
	named "example_invalid".		named example_invalid.
	error = 1*error-char		error = 1*error-char
	error-char = %x20-21 / %x23-5B / %x5D-7E		error-char = %x20-21 / %x23-5B / %x5D-7E
	7. Security Considerations		7. Security Considerations
	As a flexible and extensible framework, OAuth's security		As a flexible and extensible framework, OAuth's security
	considerations depend on many factors. The following sections		considerations depend on many factors. The following sections
	provide implementers with security guidelines focused on the three		provide implementers with security guidelines focused on the three
	client profiles described in Section 2.1: web application, browser-		client profiles described in Section 2.1: web application, browser-
	skipping to change at page 54, line 22 ¶		skipping to change at page 52, line 50 ¶
	restrictions also help to reduce the impact of access token leakage.		restrictions also help to reduce the impact of access token leakage.
	In particular, access tokens SHOULD be restricted to certain resource		In particular, access tokens SHOULD be restricted to certain resource
	servers (audience restriction), preferably to a single resource		servers (audience restriction), preferably to a single resource
	server. To put this into effect, the authorization server associates		server. To put this into effect, the authorization server associates
	the access token with certain resource servers and every resource		the access token with certain resource servers and every resource
	server is obliged to verify, for every request, whether the access		server is obliged to verify, for every request, whether the access
	token sent with that request was meant to be used for that particular		token sent with that request was meant to be used for that particular
	resource server. If not, the resource server MUST refuse to serve		resource server. If not, the resource server MUST refuse to serve
	the respective request. Clients and authorization servers MAY		the respective request. Clients and authorization servers MAY
	utilize the parameters "scope" or "resource" as specified in this		utilize the parameters scope or resource as specified in this
	document and [RFC8707], respectively, to determine the resource		document and [RFC8707], respectively, to determine the resource
	server they want to access.		server they want to access.
	Additionally, access tokens SHOULD be restricted to certain resources		Additionally, access tokens SHOULD be restricted to certain resources
	and actions on resource servers or resources. To put this into		and actions on resource servers or resources. To put this into
	effect, the authorization server associates the access token with the		effect, the authorization server associates the access token with the
	respective resource and actions and every resource server is obliged		respective resource and actions and every resource server is obliged
	to verify, for every request, whether the access token sent with that		to verify, for every request, whether the access token sent with that
	request was meant to be used for that particular action on the		request was meant to be used for that particular action on the
	particular resource. If not, the resource server must refuse to		particular resource. If not, the resource server must refuse to
	serve the respective request. Clients and authorization servers MAY		serve the respective request. Clients and authorization servers MAY
	utilize the parameter "scope" and "authorization_details" as		utilize the parameter scope and authorization_details as specified in
	specified in [I-D.ietf-oauth-rar] to determine those resources and/or		[I-D.ietf-oauth-rar] to determine those resources and/or actions.
	actions.
	7.2. Client Authentication		7.2. Client Authentication
	The authorization server MUST only rely on client authentication if		The authorization server MUST only rely on client authentication if
	the process of issuance/registration and distribution of the		the process of issuance/registration and distribution of the
	underlying credentials ensures their confidentiality.		underlying credentials ensures their confidentiality.
	When client authentication is not possible, the authorization server		When client authentication is not possible, the authorization server
	SHOULD employ other means to validate the client's identity - for		SHOULD employ other means to validate the client's identity - for
	example, by requiring the registration of the client redirect URI or		example, by requiring the registration of the client redirect URI or
	skipping to change at page 55, line 29 ¶		skipping to change at page 54, line 13 ¶
	services or to use the client credentials grant type.		services or to use the client credentials grant type.
	7.2.1. Client Authentication of Native Apps		7.2.1. Client Authentication of Native Apps
	Secrets that are statically included as part of an app distributed to		Secrets that are statically included as part of an app distributed to
	multiple users should not be treated as confidential secrets, as one		multiple users should not be treated as confidential secrets, as one
	user may inspect their copy and learn the shared secret. For this		user may inspect their copy and learn the shared secret. For this
	reason, it is NOT RECOMMENDED for authorization servers to require		reason, it is NOT RECOMMENDED for authorization servers to require
	client authentication of public native apps clients using a shared		client authentication of public native apps clients using a shared
	secret, as this serves little value beyond client identification		secret, as this serves little value beyond client identification
	which is already provided by the "client_id" request parameter.		which is already provided by the client_id request parameter.
	Authorization servers that still require a statically included shared		Authorization servers that still require a statically included shared
	secret for native app clients MUST treat the client as a public		secret for native app clients MUST treat the client as a public
	client (as defined in Section 2.1), and not accept the secret as		client (as defined in Section 2.1), and not accept the secret as
	proof of the client's identity. Without additional measures, such		proof of the client's identity. Without additional measures, such
	clients are subject to client impersonation (see Section 7.4.1).		clients are subject to client impersonation (see Section 7.4.1).
	7.3. Registration of Native App Clients		7.3. Registration of Native App Clients
	Except when using a mechanism like Dynamic Client Registration		Except when using a mechanism like Dynamic Client Registration
	skipping to change at page 56, line 11 ¶		skipping to change at page 54, line 41 ¶
	specific information, such as the app package or bundle name, or		specific information, such as the app package or bundle name, or
	other information that may be useful for verifying the calling app's		other information that may be useful for verifying the calling app's
	identity on operating systems that support such functions.		identity on operating systems that support such functions.
	For private-use URI scheme-based redirect URIs, authorization servers		For private-use URI scheme-based redirect URIs, authorization servers
	SHOULD require that the URI scheme be based on a domain name that is		SHOULD require that the URI scheme be based on a domain name that is
	under the control of the app. In addition to the collision-resistant		under the control of the app. In addition to the collision-resistant
	properties, this can help to prove ownership in the event of a		properties, this can help to prove ownership in the event of a
	dispute where two apps claim the same private-use URI scheme (where		dispute where two apps claim the same private-use URI scheme (where
	one app is acting maliciously). For example, if two apps claimed		one app is acting maliciously). For example, if two apps claimed
	"com.example.app", the owner of "example.com" could petition the app		com.example.app, the owner of example.com could petition the app
	store operator to remove the counterfeit app. Such a petition is		store operator to remove the counterfeit app. Such a petition is
	harder to prove if a generic URI scheme was used.		harder to prove if a generic URI scheme was used.
	7.4. Client Impersonation		7.4. Client Impersonation
	A malicious client can impersonate another client and obtain access		A malicious client can impersonate another client and obtain access
	to protected resources if the impersonated client fails to, or is		to protected resources if the impersonated client fails to, or is
	unable to, keep its client credentials confidential.		unable to, keep its client credentials confidential.
	The authorization server SHOULD enforce explicit resource owner		The authorization server SHOULD enforce explicit resource owner
	skipping to change at page 56, line 43 ¶		skipping to change at page 55, line 27 ¶
	7.4.1. Impersonation of Native Apps		7.4.1. Impersonation of Native Apps
	As stated above, the authorization server SHOULD NOT process		As stated above, the authorization server SHOULD NOT process
	authorization requests automatically without user consent or		authorization requests automatically without user consent or
	interaction, except when the identity of the client can be assured.		interaction, except when the identity of the client can be assured.
	This includes the case where the user has previously approved an		This includes the case where the user has previously approved an
	authorization request for a given client ID - unless the identity of		authorization request for a given client ID - unless the identity of
	the client can be proven, the request SHOULD be processed as if no		the client can be proven, the request SHOULD be processed as if no
	previous request had been approved.		previous request had been approved.
	Measures such as claimed "https" scheme redirects MAY be accepted by		Measures such as claimed https scheme redirects MAY be accepted by
	authorization servers as identity proof. Some operating systems may		authorization servers as identity proof. Some operating systems may
	offer alternative platform-specific identity features that MAY be		offer alternative platform-specific identity features that MAY be
	accepted, as appropriate.		accepted, as appropriate.
	7.4.2. Access Token Privilege Restriction		7.4.2. Access Token Privilege Restriction
	The client SHOULD request access tokens with the minimal scope		The client SHOULD request access tokens with the minimal scope
	necessary. The authorization server SHOULD take the client identity		necessary. The authorization server SHOULD take the client identity
	into account when choosing how to honor the requested scope and MAY		into account when choosing how to honor the requested scope and MAY
	issue an access token with less rights than requested.		issue an access token with less rights than requested.
	skipping to change at page 57, line 27 ¶		skipping to change at page 56, line 5 ¶
	restrictions also help to reduce the impact of access token leakage.		restrictions also help to reduce the impact of access token leakage.
	In particular, access tokens SHOULD be restricted to certain resource		In particular, access tokens SHOULD be restricted to certain resource
	servers (audience restriction), preferably to a single resource		servers (audience restriction), preferably to a single resource
	server. To put this into effect, the authorization server associates		server. To put this into effect, the authorization server associates
	the access token with certain resource servers and every resource		the access token with certain resource servers and every resource
	server is obliged to verify, for every request, whether the access		server is obliged to verify, for every request, whether the access
	token sent with that request was meant to be used for that particular		token sent with that request was meant to be used for that particular
	resource server. If not, the resource server MUST refuse to serve		resource server. If not, the resource server MUST refuse to serve
	the respective request. Clients and authorization servers MAY		the respective request. Clients and authorization servers MAY
	utilize the parameters "scope" or "resource" as specified in		utilize the parameters scope or resource as specified in [RFC8707],
	[RFC8707], respectively, to determine the resource server they want		respectively, to determine the resource server they want to access.
	to access.
	7.4.3. Access Token Replay Prevention		7.4.3. Access Token Replay Prevention
	Additionally, access tokens SHOULD be restricted to certain resources		Additionally, access tokens SHOULD be restricted to certain resources
	and actions on resource servers or resources. To put this into		and actions on resource servers or resources. To put this into
	effect, the authorization server associates the access token with the		effect, the authorization server associates the access token with the
	respective resource and actions and every resource server is obliged		respective resource and actions and every resource server is obliged
	to verify, for every request, whether the access token sent with that		to verify, for every request, whether the access token sent with that
	request was meant to be used for that particular action on the		request was meant to be used for that particular action on the
	particular resource. If not, the resource server must refuse to		particular resource. If not, the resource server must refuse to
	serve the respective request. Clients and authorization servers MAY		serve the respective request. Clients and authorization servers MAY
	utilize the parameter "scope" and "authorization_details" as		utilize the parameter scope and authorization_details as specified in
	specified in [I-D.ietf-oauth-rar] to determine those resources and/or		[I-D.ietf-oauth-rar] to determine those resources and/or actions.
	actions.
	Authorization and resource servers SHOULD use mechanisms for sender-		Authorization and resource servers SHOULD use mechanisms for sender-
	constrained access tokens to prevent token replay as described in		constrained access tokens to prevent token replay as described in
	(#pop_tokens). A sender-constrained access token scopes the		(#pop_tokens). A sender-constrained access token scopes the
	applicability of an access token to a certain sender. This sender is		applicability of an access token to a certain sender. This sender is
	obliged to demonstrate knowledge of a certain secret as prerequisite		obliged to demonstrate knowledge of a certain secret as prerequisite
	for the acceptance of that access token at the recipient (e.g., a		for the acceptance of that access token at the recipient (e.g., a
	resource server). The use of Mutual TLS for OAuth 2.0 [RFC8705] is		resource server). The use of Mutual TLS for OAuth 2.0 [RFC8705] is
	RECOMMENDED.		RECOMMENDED.
	skipping to change at page 58, line 31 ¶		skipping to change at page 57, line 8 ¶
	or use refresh token rotation as described in (#refreshing-an-access-		or use refresh token rotation as described in (#refreshing-an-access-
	token).		token).
	The authorization server MUST ensure that refresh tokens cannot be		The authorization server MUST ensure that refresh tokens cannot be
	generated, modified, or guessed to produce valid refresh tokens by		generated, modified, or guessed to produce valid refresh tokens by
	unauthorized parties.		unauthorized parties.
	7.6. Client Impersonating Resource Owner		7.6. Client Impersonating Resource Owner
	Resource servers may make access control decisions based on the		Resource servers may make access control decisions based on the
	identity of the resource owner as communicated in the "sub" claim		identity of the resource owner as communicated in the sub claim
	returned by the authorization server in a token introspection		returned by the authorization server in a token introspection
	response [RFC7662] or other mechanisms. If a client is able to		response [RFC7662] or other mechanisms. If a client is able to
	choose its own "client_id" during registration with the authorization		choose its own client_id during registration with the authorization
	server, then there is a risk that it can register with the same "sub"		server, then there is a risk that it can register with the same sub
	value as a privileged user. A subsequent access token obtained under		value as a privileged user. A subsequent access token obtained under
	the client credentials grant may be mistaken for an access token		the client credentials grant may be mistaken for an access token
	authorized by the privileged user if the resource server does not		authorized by the privileged user if the resource server does not
	perform additional checks.		perform additional checks.
	Authorization servers SHOULD NOT allow clients to influence their		Authorization servers SHOULD NOT allow clients to influence their
	"client_id" or "sub" value or any other claim if that can cause		client_id or sub value or any other claim if that can cause confusion
	confusion with a genuine resource owner. Where this cannot be		with a genuine resource owner. Where this cannot be avoided,
	avoided, authorization servers MUST provide other means for the		authorization servers MUST provide other means for the resource
	resource server to distinguish between access tokens authorized by a		server to distinguish between access tokens authorized by a resource
	resource owner from access tokens authorized by the client itself.		owner from access tokens authorized by the client itself.
	7.7. Protecting the Authorization Code Flow		7.7. Protecting the Authorization Code Flow
	When comparing client redirect URIs against pre-registered URIs,		When comparing client redirect URIs against pre-registered URIs,
	authorization servers MUST utilize exact string matching. This		authorization servers MUST utilize exact string matching. This
	measure contributes to the prevention of leakage of authorization		measure contributes to the prevention of leakage of authorization
	codes and access tokens (see (#insufficient_uri_validation)). It can		codes and access tokens (see (#insufficient_uri_validation)). It can
	also help to detect mix-up attacks (see (#mix_up)).		also help to detect mix-up attacks (see (#mix_up)).
	Clients MUST NOT expose URLs that forward the user's browser to		Clients MUST NOT expose URLs that forward the user's browser to
	arbitrary URIs obtained from a query parameter ("open redirector").		arbitrary URIs obtained from a query parameter ("open redirector").
	Open redirectors can enable exfiltration of authorization codes and		Open redirectors can enable exfiltration of authorization codes and
	access tokens, see (#open_redirector_on_client).		access tokens, see (#open_redirector_on_client).
	Clients MUST prevent Cross-Site Request Forgery (CSRF). In this		Clients MUST prevent Cross-Site Request Forgery (CSRF). In this
	context, CSRF refers to requests to the redirection endpoint that do		context, CSRF refers to requests to the redirection endpoint that do
	not originate at the authorization server, but a malicious third		not originate at the authorization server, but a malicious third
	party (see Section 4.4.1.8. of [RFC6819] for details). Clients that		party (see Section 4.4.1.8. of [RFC6819] for details). Clients that
	have ensured that the authorization server supports the		have ensured that the authorization server supports the
	"code_challenge" parameter MAY rely the CSRF protection provided by		code_challenge parameter MAY rely the CSRF protection provided by
	that mechanism. In OpenID Connect flows, the "nonce" parameter		that mechanism. In OpenID Connect flows, the nonce parameter
	provides CSRF protection. Otherwise, one-time use CSRF tokens		provides CSRF protection. Otherwise, one-time use CSRF tokens
	carried in the "state" parameter that are securely bound to the user		carried in the state parameter that are securely bound to the user
	agent MUST be used for CSRF protection (see (#csrf_countermeasures)).		agent MUST be used for CSRF protection (see (#csrf_countermeasures)).
	In order to prevent mix-up attacks (see (#mix_up)), clients MUST only		In order to prevent mix-up attacks (see (#mix_up)), clients MUST only
	process redirect responses of the authorization server they sent the		process redirect responses of the authorization server they sent the
	respective request to and from the same user agent this authorization		respective request to and from the same user agent this authorization
	request was initiated with. Clients MUST store the authorization		request was initiated with. Clients MUST store the authorization
	server they sent an authorization request to and bind this		server they sent an authorization request to and bind this
	information to the user agent and check that the authorization		information to the user agent and check that the authorization
	response was received from the correct authorization server. Clients		response was received from the correct authorization server. Clients
	MUST ensure that the subsequent access token request, if applicable,		MUST ensure that the subsequent access token request, if applicable,
	is sent to the same authorization server. Clients SHOULD use		is sent to the same authorization server. Clients SHOULD use
	distinct redirect URIs for each authorization server as a means to		distinct redirect URIs for each authorization server as a means to
	identify the authorization server a particular response came from.		identify the authorization server a particular response came from.
	An AS that redirects a request potentially containing user		An AS that redirects a request potentially containing user
	credentials MUST avoid forwarding these user credentials accidentally		credentials MUST avoid forwarding these user credentials accidentally
	(see Section 7.7.2 for details).		(see Section 7.7.2 for details).
	7.7.1. Loopback Redirect Considerations in Native Apps		7.7.1. Loopback Redirect Considerations in Native Apps
	Loopback interface redirect URIs use the "http" scheme (i.e., without		Loopback interface redirect URIs use the http scheme (i.e., without
	Transport Layer Security (TLS)). This is acceptable for loopback		Transport Layer Security (TLS)). This is acceptable for loopback
	interface redirect URIs as the HTTP request never leaves the device.		interface redirect URIs as the HTTP request never leaves the device.
	Clients should open the network port only when starting the		Clients should open the network port only when starting the
	authorization request and close it once the response is returned.		authorization request and close it once the response is returned.
	Clients should listen on the loopback network interface only, in		Clients should listen on the loopback network interface only, in
	order to avoid interference by other network actors.		order to avoid interference by other network actors.
	While redirect URIs using localhost (i.e.,		Clients should use loopback IP literals rather than the string
	"http://localhost:{port}/{path}") function similarly to loopback IP		localhost as described in Section 8.3.3.
	redirects described in Section 8.3.3, the use of "localhost" is NOT
	RECOMMENDED. Specifying a redirect URI with the loopback IP literal
	rather than "localhost" avoids inadvertently listening on network
	interfaces other than the loopback interface. It is also less
	susceptible to client-side firewalls and misconfigured host name
	resolution on the user's device.
	7.7.2. HTTP 307 Redirect		7.7.2. HTTP 307 Redirect
	An AS which redirects a request that potentially contains user		An AS which redirects a request that potentially contains user
	credentials MUST NOT use the HTTP 307 status code for redirection.		credentials MUST NOT use the HTTP 307 status code for redirection.
	If an HTTP redirection (and not, for example, JavaScript) is used for		If an HTTP redirection (and not, for example, JavaScript) is used for
	such a request, AS SHOULD use HTTP status code 303 "See Other".		such a request, AS SHOULD use HTTP status code 303 "See Other".
	At the authorization endpoint, a typical protocol flow is that the AS		At the authorization endpoint, a typical protocol flow is that the AS
	prompts the user to enter their credentials in a form that is then		prompts the user to enter their credentials in a form that is then
	skipping to change at page 61, line 19 ¶		skipping to change at page 59, line 33 ¶
	authorization code for an access token, the authorization server		authorization code for an access token, the authorization server
	SHOULD attempt to revoke all refresh and access tokens already		SHOULD attempt to revoke all refresh and access tokens already
	granted based on the compromised authorization code.		granted based on the compromised authorization code.
	If the client can be authenticated, the authorization servers MUST		If the client can be authenticated, the authorization servers MUST
	authenticate the client and ensure that the authorization code was		authenticate the client and ensure that the authorization code was
	issued to the same client.		issued to the same client.
	Clients MUST prevent injection (replay) of authorization codes into		Clients MUST prevent injection (replay) of authorization codes into
	the authorization response by attackers. To this end, using		the authorization response by attackers. To this end, using
	"code_challenge" and "code_verifier" is REQUIRED for clients and		code_challenge and code_verifier is REQUIRED for clients and
	authorization servers MUST enforce their use, unless both of the		authorization servers MUST enforce their use, unless both of the
	following criteria are met:		following criteria are met:
	* The client is a confidential client.		* The client is a confidential client.
	* In the specific deployment and the specific request, there is		* In the specific deployment and the specific request, there is
	reasonable assurance for authorization server that the client		reasonable assurance for authorization server that the client
	implements the OpenID Connect "nonce" mechanism properly.		implements the OpenID Connect nonce mechanism properly.
	In this case, using and enforcing "code_challenge" and		In this case, using and enforcing code_challenge and code_verifier is
	"code_verifier" is still RECOMMENDED.		still RECOMMENDED.
	The "code_challenge" or OpenID Connect "nonce" value MUST be		The code_challenge or OpenID Connect nonce value MUST be transaction-
	transaction-specific and securely bound to the client and the user		specific and securely bound to the client and the user agent in which
	agent in which the transaction was started. If a transaction leads		the transaction was started. If a transaction leads to an error,
	to an error, fresh values for "code_challenge" or "nonce" MUST be		fresh values for code_challenge or nonce MUST be chosen.
	chosen.
	Historic note: Although PKCE [RFC7636] was originally designed as a		Historic note: Although PKCE [RFC7636] was originally designed as a
	mechanism to protect native apps, this advice applies to all kinds of		mechanism to protect native apps, this advice applies to all kinds of
	OAuth clients, including web applications and other confidential		OAuth clients, including web applications and other confidential
	clients.		clients.
	Clients SHOULD use code challenge methods that do not expose the		Clients SHOULD use code challenge methods that do not expose the
	"code_verifier" in the authorization request. Otherwise, attackers		code_verifier in the authorization request. Otherwise, attackers
	that can read the authorization request (cf. Attacker A4 in		that can read the authorization request (cf. Attacker A4 in
	(#secmodel)) can break the security provided by this mechanism.		(#secmodel)) can break the security provided by this mechanism.
	Currently, "S256" is the only such method.		Currently, S256 is the only such method.
	When an authorization code arrives at the token endpoint, the		When an authorization code arrives at the token endpoint, the
	authorization server MUST do the following check:		authorization server MUST do the following check:
	1. If there was a "code_challenge" in the authorization request for		1. If there was a code_challenge in the authorization request for
	which this code was issued, there must be a "code_verifier" in		which this code was issued, there must be a code_verifier in the
	the token request, and it MUST be verified according to the steps		token request, and it MUST be verified according to the steps in
	in Section 3.2.2. (This is no change from the current behavior		Section 3.2.2. (This is no change from the current behavior in
	in [RFC7636].)		[RFC7636].)
	2. If there was no "code_challenge" in the authorization request,		2. If there was no code_challenge in the authorization request, any
	any request to the token endpoint containing a "code_verifier"		request to the token endpoint containing a code_verifier MUST be
	MUST be rejected.		rejected.
	Authorization servers MUST support the "code_challenge" and		Authorization servers MUST support the code_challenge and
	"code_verifier" parameters.		code_verifier parameters.
	Authorization servers MUST provide a way to detect their support for		Authorization servers MUST provide a way to detect their support for
	the "code_challenge" mechanism. To this end, they MUST either (a)		the code_challenge mechanism. To this end, they MUST either (a)
	publish the element "code_challenge_methods_supported" in their AS		publish the element code_challenge_methods_supported in their AS
	metadata ([RFC8414]) containing the supported		metadata ([RFC8414]) containing the supported code_challenge_methods
	"code_challenge_method"s (which can be used by the client to detect		(which can be used by the client to detect support) or (b) provide a
	support) or (b) provide a deployment-specific way to ensure or		deployment-specific way to ensure or determine support by the AS.
	determine support by the AS.
	7.9. Request Confidentiality		7.9. Request Confidentiality
	Access tokens, refresh tokens, authorization codes, and client		Access tokens, refresh tokens, authorization codes, and client
	credentials MUST NOT be transmitted in the clear.		credentials MUST NOT be transmitted in the clear.
	The "state" and "scope" parameters SHOULD NOT include sensitive		The state and scope parameters SHOULD NOT include sensitive client or
	client or resource owner information in plain text, as they can be		resource owner information in plain text, as they can be transmitted
	transmitted over insecure channels or stored insecurely.		over insecure channels or stored insecurely.
	7.10. Ensuring Endpoint Authenticity		7.10. Ensuring Endpoint Authenticity
	In order to prevent man-in-the-middle attacks, the authorization		In order to prevent man-in-the-middle attacks, the authorization
	server MUST require the use of TLS with server authentication as		server MUST require the use of TLS with server authentication as
	defined by [RFC2818] for any request sent to the authorization and		defined by [RFC2818] for any request sent to the authorization and
	token endpoints. The client MUST validate the authorization server's		token endpoints. The client MUST validate the authorization server's
	TLS certificate as defined by [RFC6125] and in accordance with its		TLS certificate as defined by [RFC6125] and in accordance with its
	requirements for server identity authentication.		requirements for server identity authentication.
	skipping to change at page 64, line 14 ¶		skipping to change at page 62, line 36 ¶
	Users who are particularly concerned about their security when using		Users who are particularly concerned about their security when using
	in-app browser tabs may also take the additional step of opening the		in-app browser tabs may also take the additional step of opening the
	request in the full browser from the in-app browser tab and complete		request in the full browser from the in-app browser tab and complete
	the authorization there, as most implementations of the in-app		the authorization there, as most implementations of the in-app
	browser tab pattern offer such functionality.		browser tab pattern offer such functionality.
	7.14. Malicious External User-Agents in Native Apps		7.14. Malicious External User-Agents in Native Apps
	If a malicious app is able to configure itself as the default handler		If a malicious app is able to configure itself as the default handler
	for "https" scheme URIs in the operating system, it will be able to		for https scheme URIs in the operating system, it will be able to
	intercept authorization requests that use the default browser and		intercept authorization requests that use the default browser and
	abuse this position of trust for malicious ends such as phishing the		abuse this position of trust for malicious ends such as phishing the
	user.		user.
	This attack is not confined to OAuth; a malicious app configured in		This attack is not confined to OAuth; a malicious app configured in
	this way would present a general and ongoing risk to the user beyond		this way would present a general and ongoing risk to the user beyond
	OAuth usage by native apps. Many operating systems mitigate this		OAuth usage by native apps. Many operating systems mitigate this
	issue by requiring an explicit user action to change the default		issue by requiring an explicit user action to change the default
	handler for "http" and "https" scheme URIs.		handler for http and https scheme URIs.
	7.15. Cross-Site Request Forgery		7.15. Cross-Site Request Forgery
	An attacker might attempt to inject a request to the redirect URI of		An attacker might attempt to inject a request to the redirect URI of
	the legitimate client on the victim's device, e.g., to cause the		the legitimate client on the victim's device, e.g., to cause the
	client to access resources under the attacker's control. This is a		client to access resources under the attacker's control. This is a
	variant of an attack known as Cross-Site Request Forgery (CSRF).		variant of an attack known as Cross-Site Request Forgery (CSRF).
	The traditional countermeasure are CSRF tokens that are bound to the		The traditional countermeasure are CSRF tokens that are bound to the
	user agent and passed in the "state" parameter to the authorization		user agent and passed in the state parameter to the authorization
	server as described in [RFC6819]. The same protection is provided by		server as described in [RFC6819]. The same protection is provided by
	the "code_verifier" parameter or the OpenID Connect "nonce" value.		the code_verifier parameter or the OpenID Connect nonce value.
	When using "code_verifier" instead of "state" or "nonce" for CSRF		When using code_verifier instead of state or nonce for CSRF
	protection, it is important to note that:		protection, it is important to note that:
	* Clients MUST ensure that the AS supports the		* Clients MUST ensure that the AS supports the code_challenge_method
	"code_challenge_method" intended to be used by the client. If an		intended to be used by the client. If an authorization server
	authorization server does not support the requested method,		does not support the requested method, state or nonce MUST be used
	"state" or "nonce" MUST be used for CSRF protection instead.		for CSRF protection instead.
	* If "state" is used for carrying application state, and integrity		* If state is used for carrying application state, and integrity of
	of its contents is a concern, clients MUST protect "state" against		its contents is a concern, clients MUST protect state against
	tampering and swapping. This can be achieved by binding the		tampering and swapping. This can be achieved by binding the
	contents of state to the browser session and/or signed/encrypted		contents of state to the browser session and/or signed/encrypted
	state values [I-D.bradley-oauth-jwt-encoded-state].		state values [I-D.bradley-oauth-jwt-encoded-state].
	AS therefore MUST provide a way to detect their supported code		AS therefore MUST provide a way to detect their supported code
	challenge methods either via AS metadata according to [RFC8414] or		challenge methods either via AS metadata according to [RFC8414] or
	provide a deployment-specific way to ensure or determine support.		provide a deployment-specific way to ensure or determine support.
	7.16. Clickjacking		7.16. Clickjacking
	skipping to change at page 65, line 37 ¶		skipping to change at page 64, line 9 ¶
	origins in user agents that support CSP. The client MAY permit being		origins in user agents that support CSP. The client MAY permit being
	framed by some other origin than the one used in its redirection		framed by some other origin than the one used in its redirection
	endpoint. For this reason, authorization servers SHOULD allow		endpoint. For this reason, authorization servers SHOULD allow
	administrators to configure allowed origins for particular clients		administrators to configure allowed origins for particular clients
	and/or for clients to register these dynamically.		and/or for clients to register these dynamically.
	Using CSP allows authorization servers to specify multiple origins in		Using CSP allows authorization servers to specify multiple origins in
	a single response header field and to constrain these using flexible		a single response header field and to constrain these using flexible
	patterns (see [CSP-2] for details). Level 2 of this standard		patterns (see [CSP-2] for details). Level 2 of this standard
	provides a robust mechanism for protecting against clickjacking by		provides a robust mechanism for protecting against clickjacking by
	using policies that restrict the origin of frames (using "frame-		using policies that restrict the origin of frames (using frame-
	ancestors") together with those that restrict the sources of scripts		ancestors) together with those that restrict the sources of scripts
	allowed to execute on an HTML page (by using "script-src"). A non-		allowed to execute on an HTML page (by using script-src). A non-
	normative example of such a policy is shown in the following listing:		normative example of such a policy is shown in the following listing:
	"HTTP/1.1 200 OK Content-Security-Policy: frame-ancestors		HTTP/1.1 200 OK Content-Security-Policy: frame-ancestors
	https://ext.example.org:8000 Content-Security-Policy: script-src		https://ext.example.org:8000 Content-Security-Policy: script-src
	'self' X-Frame-Options: ALLOW-FROM https://ext.example.org:8000 ..."		'self' X-Frame-Options: ALLOW-FROM https://ext.example.org:8000 ...
	Because some user agents do not support [CSP-2], this technique		Because some user agents do not support [CSP-2], this technique
	SHOULD be combined with others, including those described in		SHOULD be combined with others, including those described in
	[RFC6819], unless such legacy user agents are explicitly unsupported		[RFC6819], unless such legacy user agents are explicitly unsupported
	by the authorization server. Even in such cases, additional		by the authorization server. Even in such cases, additional
	countermeasures SHOULD still be employed.		countermeasures SHOULD still be employed.
	7.17. Code Injection and Input Validation		7.17. Code Injection and Input Validation
	A code injection attack occurs when an input or otherwise external		A code injection attack occurs when an input or otherwise external
	variable is used by an application unsanitized and causes		variable is used by an application unsanitized and causes
	modification to the application logic. This may allow an attacker to		modification to the application logic. This may allow an attacker to
	gain access to the application device or its data, cause denial of		gain access to the application device or its data, cause denial of
	service, or introduce a wide range of malicious side-effects.		service, or introduce a wide range of malicious side-effects.
	The authorization server and client MUST sanitize (and validate when		The authorization server and client MUST sanitize (and validate when
	possible) any value received - in particular, the value of the		possible) any value received - in particular, the value of the state
	"state" and "redirect_uri" parameters.		and redirect_uri parameters.
	7.18. Open Redirectors		7.18. Open Redirectors
	The following attacks can occur when an AS or client has an open		The following attacks can occur when an AS or client has an open
	redirector. An open redirector is an endpoint that forwards a user's		redirector. An open redirector is an endpoint that forwards a user's
	browser to an arbitrary URI obtained from a query parameter.		browser to an arbitrary URI obtained from a query parameter.
	7.18.1. Client as Open Redirector		7.18.1. Client as Open Redirector
	Clients MUST NOT expose open redirectors. Attackers may use open		Clients MUST NOT expose open redirectors. Attackers may use open
	skipping to change at page 66, line 48 ¶		skipping to change at page 65, line 20 ¶
	7.18.2. Authorization Server as Open Redirector		7.18.2. Authorization Server as Open Redirector
	Just as with clients, attackers could try to utilize a user's trust		Just as with clients, attackers could try to utilize a user's trust
	in the authorization server (and its URL in particular) for		in the authorization server (and its URL in particular) for
	performing phishing attacks. OAuth authorization servers regularly		performing phishing attacks. OAuth authorization servers regularly
	redirect users to other web sites (the clients), but must do so in a		redirect users to other web sites (the clients), but must do so in a
	safe way.		safe way.
	Section 4.1.2.1 already prevents open redirects by stating that the		Section 4.1.2.1 already prevents open redirects by stating that the
	AS MUST NOT automatically redirect the user agent in case of an		AS MUST NOT automatically redirect the user agent in case of an
	invalid combination of "client_id" and "redirect_uri".		invalid combination of client_id and redirect_uri.
	However, an attacker could also utilize a correctly registered		However, an attacker could also utilize a correctly registered
	redirect URI to perform phishing attacks. The attacker could, for		redirect URI to perform phishing attacks. The attacker could, for
	example, register a client via dynamic client registration [RFC7591]		example, register a client via dynamic client registration [RFC7591]
	and intentionally send an erroneous authorization request, e.g., by		and intentionally send an erroneous authorization request, e.g., by
	using an invalid scope value, thus instructing the AS to redirect the		using an invalid scope value, thus instructing the AS to redirect the
	user agent to its phishing site.		user agent to its phishing site.
	The AS MUST take precautions to prevent this threat. Based on its		The AS MUST take precautions to prevent this threat. Based on its
	risk assessment, the AS needs to decide whether it can trust the		risk assessment, the AS needs to decide whether it can trust the
	skipping to change at page 67, line 28 ¶		skipping to change at page 65, line 49 ¶
	To protect against a compromised or malicious authorization server		To protect against a compromised or malicious authorization server
	attacking another authorization server used by the same app, it is		attacking another authorization server used by the same app, it is
	REQUIRED that a unique redirect URI is used for each authorization		REQUIRED that a unique redirect URI is used for each authorization
	server used by the app (for example, by varying the path component),		server used by the app (for example, by varying the path component),
	and that authorization responses are rejected if the redirect URI		and that authorization responses are rejected if the redirect URI
	they were received on doesn't match the redirect URI in an outgoing		they were received on doesn't match the redirect URI in an outgoing
	authorization request.		authorization request.
	The native app MUST store the redirect URI used in the authorization		The native app MUST store the redirect URI used in the authorization
	request with the authorization session data (i.e., along with "state"		request with the authorization session data (i.e., along with state
	and other related data) and MUST verify that the URI on which the		and other related data) and MUST verify that the URI on which the
	authorization response was received exactly matches it.		authorization response was received exactly matches it.
	The requirement of Section 7.3, specifically that authorization		The requirement of Section 7.3, specifically that authorization
	servers reject requests with URIs that don't match what was		servers reject requests with URIs that don't match what was
	registered, is also required to prevent such attacks.		registered, is also required to prevent such attacks.
	7.20. Embedded User Agents in Native Apps		7.20. Embedded User Agents in Native Apps
	Embedded user agents are a technically possible method for		Embedded user agents are a technically possible method for
	skipping to change at page 68, line 25 ¶		skipping to change at page 66, line 44 ¶
	site first.		site first.
	Aside from the security concerns, embedded user agents do not share		Aside from the security concerns, embedded user agents do not share
	the authentication state with other apps or the browser, requiring		the authentication state with other apps or the browser, requiring
	the user to log in for every authorization request, which is often		the user to log in for every authorization request, which is often
	considered an inferior user experience.		considered an inferior user experience.
	7.21. Other Recommendations		7.21. Other Recommendations
	Authorization servers SHOULD NOT allow clients to influence their		Authorization servers SHOULD NOT allow clients to influence their
	"client_id" or "sub" value or any other claim if that can cause		client_id or sub value or any other claim if that can cause confusion
	confusion with a genuine resource owner (see		with a genuine resource owner (see (#client_impersonating)).
	(#client_impersonating)).
	8. Native Applications		8. Native Applications
	Native applications are clients installed and executed on the device		Native applications are clients installed and executed on the device
	used by the resource owner (i.e., desktop application, native mobile		used by the resource owner (i.e., desktop application, native mobile
	application). Native applications require special consideration		application). Native applications require special consideration
	related to security, platform capabilities, and overall end-user		related to security, platform capabilities, and overall end-user
	experience.		experience.
	The authorization endpoint requires interaction between the client		The authorization endpoint requires interaction between the client
	skipping to change at page 70, line 24 ¶		skipping to change at page 68, line 46 ¶
	client's server, the redirect URI used by a native app returns the		client's server, the redirect URI used by a native app returns the
	response to the app. Several options for a redirect URI that will		response to the app. Several options for a redirect URI that will
	return the authorization response to the native app in different		return the authorization response to the native app in different
	platforms are documented in Section 8.3. Any redirect URI that		platforms are documented in Section 8.3. Any redirect URI that
	allows the app to receive the URI and inspect its parameters is		allows the app to receive the URI and inspect its parameters is
	viable.		viable.
	After constructing the authorization request URI, the app uses		After constructing the authorization request URI, the app uses
	platform-specific APIs to open the URI in an external user agent.		platform-specific APIs to open the URI in an external user agent.
	Typically, the external user agent used is the default browser, that		Typically, the external user agent used is the default browser, that
	is, the application configured for handling "http" and "https" scheme		is, the application configured for handling http and https scheme
	URIs on the system; however, different browser selection criteria and		URIs on the system; however, different browser selection criteria and
	other categories of external user agents MAY be used.		other categories of external user agents MAY be used.
	This best practice focuses on the browser as the RECOMMENDED external		This best practice focuses on the browser as the RECOMMENDED external
	user agent for native apps. An external user agent designed		user agent for native apps. An external user agent designed
	specifically for user authorization and capable of processing		specifically for user authorization and capable of processing
	authorization requests and responses like a browser MAY also be used.		authorization requests and responses like a browser MAY also be used.
	Other external user agents, such as a native app provided by the		Other external user agents, such as a native app provided by the
	authorization server may meet the criteria set out in this best		authorization server may meet the criteria set out in this best
	practice, including using the same redirect URI properties, but their		practice, including using the same redirect URI properties, but their
	skipping to change at page 71, line 16 ¶		skipping to change at page 69, line 35 ¶
	least the three redirect URI options described in the following		least the three redirect URI options described in the following
	subsections to native apps. Native apps MAY use whichever redirect		subsections to native apps. Native apps MAY use whichever redirect
	option suits their needs best, taking into account platform-specific		option suits their needs best, taking into account platform-specific
	implementation details.		implementation details.
	8.3.1. Private-Use URI Scheme Redirection		8.3.1. Private-Use URI Scheme Redirection
	Many mobile and desktop computing platforms support inter-app		Many mobile and desktop computing platforms support inter-app
	communication via URIs by allowing apps to register private-use URI		communication via URIs by allowing apps to register private-use URI
	schemes (sometimes colloquially referred to as "custom URL schemes")		schemes (sometimes colloquially referred to as "custom URL schemes")
	like "com.example.app". When the browser or another app attempts to		like com.example.app. When the browser or another app attempts to
	load a URI with a private-use URI scheme, the app that registered it		load a URI with a private-use URI scheme, the app that registered it
	is launched to handle the request.		is launched to handle the request.
	To perform an authorization request with a private-use URI scheme		To perform an authorization request with a private-use URI scheme
	redirect, the native app launches the browser with a standard		redirect, the native app launches the browser with a standard
	authorization request, but one where the redirect URI utilizes a		authorization request, but one where the redirect URI utilizes a
	private-use URI scheme it registered with the operating system.		private-use URI scheme it registered with the operating system.
	When choosing a URI scheme to associate with the app, apps MUST use a		When choosing a URI scheme to associate with the app, apps MUST use a
	URI scheme based on a domain name under their control, expressed in		URI scheme based on a domain name under their control, expressed in
	reverse order, as recommended by Section 3.8 of [RFC7595] for		reverse order, as recommended by Section 3.8 of [RFC7595] for
	private-use URI schemes.		private-use URI schemes.
	For example, an app that controls the domain name "app.example.com"		For example, an app that controls the domain name app.example.com can
	can use "com.example.app" as their scheme. Some authorization		use com.example.app as their scheme. Some authorization servers
	servers assign client identifiers based on domain names, for example,		assign client identifiers based on domain names, for example,
	"client1234.usercontent.example.net", which can also be used as the		client1234.usercontent.example.net, which can also be used as the
	domain name for the scheme when reversed in the same manner. A		domain name for the scheme when reversed in the same manner. A
	scheme such as "myapp", however, would not meet this requirement, as		scheme such as myapp, however, would not meet this requirement, as it
	it is not based on a domain name.		is not based on a domain name.
	When there are multiple apps by the same publisher, care must be		When there are multiple apps by the same publisher, care must be
	taken so that each scheme is unique within that group. On platforms		taken so that each scheme is unique within that group. On platforms
	that use app identifiers based on reverse-order domain names, those		that use app identifiers based on reverse-order domain names, those
	identifiers can be reused as the private-use URI scheme for the OAuth		identifiers can be reused as the private-use URI scheme for the OAuth
	redirect to help avoid this problem.		redirect to help avoid this problem.
	Following the requirements of Section 3.2 of [RFC3986], as there is		Following the requirements of Section 3.2 of [RFC3986], as there is
	no naming authority for private-use URI scheme redirects, only a		no naming authority for private-use URI scheme redirects, only a
	single slash ("/") appears after the scheme component. A complete		single slash (/) appears after the scheme component. A complete
	example of a redirect URI utilizing a private-use URI scheme is:		example of a redirect URI utilizing a private-use URI scheme is:
	com.example.app:/oauth2redirect/example-provider		com.example.app:/oauth2redirect/example-provider
	When the authorization server completes the request, it redirects to		When the authorization server completes the request, it redirects to
	the client's redirect URI as it would normally. As the redirect URI		the client's redirect URI as it would normally. As the redirect URI
	uses a private-use URI scheme, it results in the operating system		uses a private-use URI scheme, it results in the operating system
	launching the native app, passing in the URI as a launch parameter.		launching the native app, passing in the URI as a launch parameter.
	Then, the native app uses normal processing for the authorization		Then, the native app uses normal processing for the authorization
	response.		response.
	8.3.2. Claimed "https" Scheme URI Redirection		8.3.2. Claimed "https" Scheme URI Redirection
	Some operating systems allow apps to claim "https" scheme [RFC7230]		Some operating systems allow apps to claim https scheme [RFC7230]
	URIs in the domains they control. When the browser encounters a		URIs in the domains they control. When the browser encounters a
	claimed URI, instead of the page being loaded in the browser, the		claimed URI, instead of the page being loaded in the browser, the
	native app is launched with the URI supplied as a launch parameter.		native app is launched with the URI supplied as a launch parameter.
	Such URIs can be used as redirect URIs by native apps. They are		Such URIs can be used as redirect URIs by native apps. They are
	indistinguishable to the authorization server from a regular web-		indistinguishable to the authorization server from a regular web-
	based client redirect URI. An example is:		based client redirect URI. An example is:
	https://app.example.com/oauth2redirect/example-provider		https://app.example.com/oauth2redirect/example-provider
	As the redirect URI alone is not enough to distinguish public native		As the redirect URI alone is not enough to distinguish public native
	app clients from confidential web clients, it is REQUIRED in		app clients from confidential web clients, it is REQUIRED in
	Section 7.3 that the client type be recorded during client		Section 7.3 that the client type be recorded during client
	registration to enable the server to determine the client type and		registration to enable the server to determine the client type and
	act accordingly.		act accordingly.
	App-claimed "https" scheme redirect URIs have some advantages		App-claimed https scheme redirect URIs have some advantages compared
	compared to other native app redirect options in that the identity of		to other native app redirect options in that the identity of the
	the destination app is guaranteed to the authorization server by the		destination app is guaranteed to the authorization server by the
	operating system. For this reason, native apps SHOULD use them over		operating system. For this reason, native apps SHOULD use them over
	the other options where possible.		the other options where possible.
	8.3.3. Loopback Interface Redirection		8.3.3. Loopback Interface Redirection
	Native apps that are able to open a port on the loopback network		Native apps that are able to open a port on the loopback network
	interface without needing special permissions (typically, those on		interface without needing special permissions (typically, those on
	desktop operating systems) can use the loopback interface to receive		desktop operating systems) can use the loopback interface to receive
	the OAuth redirect.		the OAuth redirect.
	Loopback redirect URIs use the "http" scheme and are constructed with		Loopback redirect URIs use the http scheme and are constructed with
	the loopback IP literal and whatever port the client is listening on.		the loopback IP literal and whatever port the client is listening on.
	That is, "http://127.0.0.1:{port}/{path}" for IPv4, and		That is, http://127.0.0.1:{port}/{path} for IPv4, and
	"http://[::1]:{port}/{path}" for IPv6. An example redirect using the		http://[::1]:{port}/{path} for IPv6. An example redirect using the
	IPv4 loopback interface with a randomly assigned port:		IPv4 loopback interface with a randomly assigned port:
	http://127.0.0.1:51004/oauth2redirect/example-provider		http://127.0.0.1:51004/oauth2redirect/example-provider
	An example redirect using the IPv6 loopback interface with a randomly		An example redirect using the IPv6 loopback interface with a randomly
	assigned port:		assigned port:
	http://[::1]:61023/oauth2redirect/example-provider		http://[::1]:61023/oauth2redirect/example-provider
			While redirect URIs using the name localhost (i.e.,
			http://localhost:{port}/{path}) function similarly to loopback IP
			redirects, the use of localhost is NOT RECOMMENDED. Specifying a
			redirect URI with the loopback IP literal rather than localhost
			avoids inadvertently listening on network interfaces other than the
			loopback interface. It is also less susceptible to client-side
			firewalls and misconfigured host name resolution on the user's
			device.
	The authorization server MUST allow any port to be specified at the		The authorization server MUST allow any port to be specified at the
	time of the request for loopback IP redirect URIs, to accommodate		time of the request for loopback IP redirect URIs, to accommodate
	clients that obtain an available ephemeral port from the operating		clients that obtain an available ephemeral port from the operating
	system at the time of the request.		system at the time of the request.
	Clients SHOULD NOT assume that the device supports a particular		Clients SHOULD NOT assume that the device supports a particular
	version of the Internet Protocol. It is RECOMMENDED that clients		version of the Internet Protocol. It is RECOMMENDED that clients
	attempt to bind to the loopback interface using both IPv4 and IPv6		attempt to bind to the loopback interface using both IPv4 and IPv6
	and use whichever is available.		and use whichever is available.
	skipping to change at page 74, line 5 ¶		skipping to change at page 72, line 39 ¶
	A non-normative list of changes from OAuth 2.0 is listed below:		A non-normative list of changes from OAuth 2.0 is listed below:
	* The authorization code grant is extended with the functionality		* The authorization code grant is extended with the functionality
	from PKCE ([RFC7636]) such that the default method of using the		from PKCE ([RFC7636]) such that the default method of using the
	authorization code grant according to this specification requires		authorization code grant according to this specification requires
	the addition of the PKCE parameters		the addition of the PKCE parameters
	* Redirect URIs must be compared using exact string matching as per		* Redirect URIs must be compared using exact string matching as per
	Section 4.1.3 of [I-D.ietf-oauth-security-topics]		Section 4.1.3 of [I-D.ietf-oauth-security-topics]
	* The Implicit grant ("response_type=token") is omitted from this		* The Implicit grant (response_type=token) is omitted from this
	specification as per Section 2.1.2 of		specification as per Section 2.1.2 of
	[I-D.ietf-oauth-security-topics]		[I-D.ietf-oauth-security-topics]
	* The Resource Owner Password Credentials grant is omitted from this		* The Resource Owner Password Credentials grant is omitted from this
	specification as per Section 2.4 of		specification as per Section 2.4 of
	[I-D.ietf-oauth-security-topics]		[I-D.ietf-oauth-security-topics]
	* Bearer token usage omits the use of bearer tokens in the query		* Bearer token usage omits the use of bearer tokens in the query
	string of URIs as per Section 4.3.2 of		string of URIs as per Section 4.3.2 of
	[I-D.ietf-oauth-security-topics]		[I-D.ietf-oauth-security-topics]
	skipping to change at page 78, line 8 ¶		skipping to change at page 76, line 48 ¶
	[I-D.ietf-oauth-par]		[I-D.ietf-oauth-par]
	Lodderstedt, T., Campbell, B., Sakimura, N., Tonge, D.,		Lodderstedt, T., Campbell, B., Sakimura, N., Tonge, D.,
	and F. Skokan, "OAuth 2.0 Pushed Authorization Requests",		and F. Skokan, "OAuth 2.0 Pushed Authorization Requests",
	Work in Progress, Internet-Draft, draft-ietf-oauth-par-10,		Work in Progress, Internet-Draft, draft-ietf-oauth-par-10,
	29 July 2021, <https://www.ietf.org/archive/id/draft-ietf-		29 July 2021, <https://www.ietf.org/archive/id/draft-ietf-
	oauth-par-10.txt>.		oauth-par-10.txt>.
	[I-D.ietf-oauth-rar]		[I-D.ietf-oauth-rar]
	Lodderstedt, T., Richer, J., and B. Campbell, "OAuth 2.0		Lodderstedt, T., Richer, J., and B. Campbell, "OAuth 2.0
	Rich Authorization Requests", Work in Progress, Internet-		Rich Authorization Requests", Work in Progress, Internet-
	Draft, draft-ietf-oauth-rar-05, 15 May 2021,		Draft, draft-ietf-oauth-rar-07, 12 September 2021,
	<https://www.ietf.org/archive/id/draft-ietf-oauth-rar-		<https://www.ietf.org/archive/id/draft-ietf-oauth-rar-
	05.txt>.		07.txt>.
	[I-D.ietf-oauth-token-binding]		[I-D.ietf-oauth-token-binding]
	Jones, M. B., Campbell, B., Bradley, J., and W. Denniss,		Jones, M. B., Campbell, B., Bradley, J., and W. Denniss,
	"OAuth 2.0 Token Binding", Work in Progress, Internet-		"OAuth 2.0 Token Binding", Work in Progress, Internet-
	Draft, draft-ietf-oauth-token-binding-08, 19 October 2018,		Draft, draft-ietf-oauth-token-binding-08, 19 October 2018,
	<https://www.ietf.org/archive/id/draft-ietf-oauth-token-		<https://www.ietf.org/archive/id/draft-ietf-oauth-token-
	binding-08.txt>.		binding-08.txt>.
	[NIST800-63]		[NIST800-63]
	Burr, W., Dodson, D., Newton, E., Perlner, R., Polk, T.,		Burr, W., Dodson, D., Newton, E., Perlner, R., Polk, T.,
	skipping to change at page 80, line 34 ¶		skipping to change at page 79, line 30 ¶
	NQSCHAR = %x20-21 / %x23-5B / %x5D-7E		NQSCHAR = %x20-21 / %x23-5B / %x5D-7E
	UNICODECHARNOCRLF = %x09 /%x20-7E / %x80-D7FF /		UNICODECHARNOCRLF = %x09 /%x20-7E / %x80-D7FF /
	%xE000-FFFD / %x10000-10FFFF		%xE000-FFFD / %x10000-10FFFF
	(The UNICODECHARNOCRLF definition is based upon the Char definition		(The UNICODECHARNOCRLF definition is based upon the Char definition
	in Section 2.2 of [W3C.REC-xml-20081126], but omitting the Carriage		in Section 2.2 of [W3C.REC-xml-20081126], but omitting the Carriage
	Return and Linefeed characters.)		Return and Linefeed characters.)
	A.1. "client_id" Syntax		A.1. "client_id" Syntax
	The "client_id" element is defined in Section 2.4.1:		The client_id element is defined in Section 2.4.1:
	client-id = *VSCHAR		client-id = *VSCHAR
	A.2. "client_secret" Syntax		A.2. "client_secret" Syntax
	The "client_secret" element is defined in Section 2.4.1:		The client_secret element is defined in Section 2.4.1:
	client-secret = *VSCHAR		client-secret = *VSCHAR
	A.3. "response_type" Syntax		A.3. "response_type" Syntax
	The "response_type" element is defined in Section 4.1.1 and		The response_type element is defined in Section 4.1.1 and
	Section 6.4:		Section 6.4:
	response-type = response-name *( SP response-name )		response-type = response-name *( SP response-name )
	response-name = 1*response-char		response-name = 1*response-char
	response-char = "_" / DIGIT / ALPHA		response-char = "_" / DIGIT / ALPHA
	A.4. "scope" Syntax		A.4. "scope" Syntax
	The "scope" element is defined in Section 3.2.2.1:		The scope element is defined in Section 3.2.2.1:
	scope = scope-token *( SP scope-token )		scope = scope-token *( SP scope-token )
	scope-token = 1*NQCHAR		scope-token = 1*NQCHAR
	A.5. "state" Syntax		A.5. "state" Syntax
	The "state" element is defined in Section 4.1.1, Section 4.1.2, and		The state element is defined in Section 4.1.1, Section 4.1.2, and
	Section 4.1.2.1:		Section 4.1.2.1:
	state = 1*VSCHAR		state = 1*VSCHAR
	A.6. "redirect_uri" Syntax		A.6. "redirect_uri" Syntax
	The "redirect_uri" element is defined in Section 4.1.1, and		The redirect_uri element is defined in Section 4.1.1, and
	Section 4.1.3:		Section 4.1.3:
	redirect-uri = URI-reference		redirect-uri = URI-reference
	A.7. "error" Syntax		A.7. "error" Syntax
	The "error" element is defined in Sections Section 4.1.2.1,		The error element is defined in Sections Section 4.1.2.1,
	Section 3.2.3.1, 7.2, and 8.5:		Section 3.2.3.1, 7.2, and 8.5:
	error = 1*NQSCHAR		error = 1*NQSCHAR
	A.8. "error_description" Syntax		A.8. "error_description" Syntax
	The "error_description" element is defined in Sections		The error_description element is defined in Sections Section 4.1.2.1,
	Section 4.1.2.1, Section 3.2.3.1, and Section 5.3:		Section 3.2.3.1, and Section 5.3:
	error-description = 1*NQSCHAR		error-description = 1*NQSCHAR
	A.9. "error_uri" Syntax		A.9. "error_uri" Syntax
	The "error_uri" element is defined in Sections Section 4.1.2.1,		The error_uri element is defined in Sections Section 4.1.2.1,
	Section 3.2.3.1, and 7.2:		Section 3.2.3.1, and 7.2:
	error-uri = URI-reference		error-uri = URI-reference
	A.10. "grant_type" Syntax		A.10. "grant_type" Syntax
	The "grant_type" element is defined in Section Section 3.2.2:		The grant_type element is defined in Section Section 3.2.2:
	grant-type = grant-name / URI-reference		grant-type = grant-name / URI-reference
	grant-name = 1*name-char		grant-name = 1*name-char
	name-char = "-" / "." / "_" / DIGIT / ALPHA		name-char = "-" / "." / "_" / DIGIT / ALPHA
	A.11. "code" Syntax		A.11. "code" Syntax
	The "code" element is defined in Section 4.1.3:		The code element is defined in Section 4.1.3:
	code = 1*VSCHAR		code = 1*VSCHAR
	A.12. "access_token" Syntax		A.12. "access_token" Syntax
	The "access_token" element is defined in Section 3.2.3:		The access_token element is defined in Section 3.2.3:
	access-token = 1*VSCHAR		access-token = 1*VSCHAR
	A.13. "token_type" Syntax		A.13. "token_type" Syntax
	The "token_type" element is defined in Section 3.2.3, and		The token_type element is defined in Section 3.2.3, and Section 6.1:
	Section 6.1:
	token-type = type-name / URI-reference		token-type = type-name / URI-reference
	type-name = 1*name-char		type-name = 1*name-char
	name-char = "-" / "." / "_" / DIGIT / ALPHA		name-char = "-" / "." / "_" / DIGIT / ALPHA
	A.14. "expires_in" Syntax		A.14. "expires_in" Syntax
	The "expires_in" element is defined in Section 3.2.3:		The expires_in element is defined in Section 3.2.3:
	expires-in = 1*DIGIT		expires-in = 1*DIGIT
	A.15. "refresh_token" Syntax		A.15. "refresh_token" Syntax
	The "refresh_token" element is defined in Section 3.2.3 and		The refresh_token element is defined in Section 3.2.3 and
	Section 4.3:		Section 4.3:
	refresh-token = 1*VSCHAR		refresh-token = 1*VSCHAR
	A.16. Endpoint Parameter Syntax		A.16. Endpoint Parameter Syntax
	The syntax for new endpoint parameters is defined in Section 6.2:		The syntax for new endpoint parameters is defined in Section 6.2:
	param-name = 1*name-char		param-name = 1*name-char
	name-char = "-" / "." / "_" / DIGIT / ALPHA		name-char = "-" / "." / "_" / DIGIT / ALPHA
	A.17. "code_verifier" Syntax		A.17. "code_verifier" Syntax
	ABNF for "code_verifier" is as follows.		ABNF for code_verifier is as follows.
	code-verifier = 43*128unreserved		code-verifier = 43*128unreserved
	unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"		unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
	ALPHA = %x41-5A / %x61-7A		ALPHA = %x41-5A / %x61-7A
	DIGIT = %x30-39		DIGIT = %x30-39
	A.18. "code_challenge" Syntax		A.18. "code_challenge" Syntax
	ABNF for "code_challenge" is as follows.		ABNF for code_challenge is as follows.
	code-challenge = 43*128unreserved		code-challenge = 43*128unreserved
	unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"		unreserved = ALPHA / DIGIT / "-" / "." / "_" / "~"
	ALPHA = %x41-5A / %x61-7A		ALPHA = %x41-5A / %x61-7A
	DIGIT = %x30-39		DIGIT = %x30-39
	Appendix B. Use of application/x-www-form-urlencoded Media Type		Appendix B. Use of application/x-www-form-urlencoded Media Type
	At the time of publication of this specification, the "application/x-		At the time of publication of this specification, the application/x-
	www-form-urlencoded" media type was defined in Section 17.13.4 of		www-form-urlencoded media type was defined in Section 17.13.4 of
	[W3C.REC-html401-19991224] but not registered in the IANA MIME Media		[W3C.REC-html401-19991224] but not registered in the IANA MIME Media
	Types registry (http://www.iana.org/assignments/media-types		Types registry (http://www.iana.org/assignments/media-types
	(http://www.iana.org/assignments/media-types)). Furthermore, that		(http://www.iana.org/assignments/media-types)). Furthermore, that
	definition is incomplete, as it does not consider non-US-ASCII		definition is incomplete, as it does not consider non-US-ASCII
	characters.		characters.
	To address this shortcoming when generating payloads using this media		To address this shortcoming when generating payloads using this media
	type, names and values MUST be encoded using the UTF-8 character		type, names and values MUST be encoded using the UTF-8 character
	encoding scheme [RFC3629] first; the resulting octet sequence then		encoding scheme [RFC3629] first; the resulting octet sequence then
	needs to be further encoded using the escaping rules defined in		needs to be further encoded using the escaping rules defined in
	skipping to change at page 85, line 30 ¶		skipping to change at page 84, line 21 ¶
	* [I-D.ietf-oauth-par]: Pushed Authorization Requests		* [I-D.ietf-oauth-par]: Pushed Authorization Requests
	- The Pushed Authorization Requests extension describes a		- The Pushed Authorization Requests extension describes a
	technique of initiating an OAuth flow from the back channel,		technique of initiating an OAuth flow from the back channel,
	providing better security and more flexibility for building		providing better security and more flexibility for building
	complex authorization requests.		complex authorization requests.
	* [I-D.ietf-oauth-rar]: Rich Authorization Requests		* [I-D.ietf-oauth-rar]: Rich Authorization Requests
	- Rich Authorization Requests specifies a new parameter		- Rich Authorization Requests specifies a new parameter
	"authorization_details" that is used to carry fine-grained		authorization_details that is used to carry fine-grained
	authorization data in the OAuth authorization request.		authorization data in the OAuth authorization request.
	Appendix D. Acknowledgements		Appendix D. Acknowledgements
	TBD		TBD
	Appendix E. Document History		Appendix E. Document History
	[[ To be removed from the final specification ]]		[[ To be removed from the final specification ]]
			-04
			* Added explicit mention of not sending access tokens in URI query strings
			* Clarifications on definition of client types
			* Consolidated text around loopback vs localhost
			* Editorial clarifications throughout the document
	-03		-03
	* refactored structure		* refactoring to collect all the grant types under the same top-level header in section 4
			* Better split normative and security consideration text into the appropriate places, both moving text that was really security considerations out of the main part of the document, as well as pulling normative requirements from the security considerations sections into the appropriate part of the main document
			* Incorporated many of the published errata on RFC6749
			* Updated references to various RFCs
			* Editorial clarifications throughout the document
	-02		-02
	-01		-01
	-00		-00
	* initial revision		* initial revision
	Authors' Addresses		Authors' Addresses
	Dick Hardt		Dick Hardt
	SignIn.Org		Hellō
	Email: dick.hardt@gmail.com		Email: dick.hardt@gmail.com
	Aaron Parecki		Aaron Parecki
	Okta		Okta
	Email: aaron@parecki.com		Email: aaron@parecki.com
	URI: https://aaronparecki.com		URI: https://aaronparecki.com
	Torsten Lodderstedt		Torsten Lodderstedt
End of changes. 195 change blocks.
	436 lines changed or deleted		454 lines changed or added
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