draft-ietf-oauth-dpop-02.txt   draft-ietf-oauth-dpop-03.txt 
Web Authorization Protocol D. Fett Web Authorization Protocol D. Fett
Internet-Draft yes.com Internet-Draft yes.com
Intended status: Standards Track B. Campbell Intended status: Standards Track B. Campbell
Expires: 22 May 2021 Ping Identity Expires: 9 October 2021 Ping Identity
J. Bradley J. Bradley
Yubico Yubico
T. Lodderstedt T. Lodderstedt
yes.com yes.com
M. Jones M. Jones
Microsoft Microsoft
D. Waite D. Waite
Ping Identity Ping Identity
18 November 2020 7 April 2021
OAuth 2.0 Demonstrating Proof-of-Possession at the Application Layer OAuth 2.0 Demonstrating Proof-of-Possession at the Application Layer
(DPoP) (DPoP)
draft-ietf-oauth-dpop-02 draft-ietf-oauth-dpop-03
Abstract Abstract
This document describes a mechanism for sender-constraining OAuth 2.0 This document describes a mechanism for sender-constraining OAuth 2.0
tokens via a proof-of-possession mechanism on the application level. tokens via a proof-of-possession mechanism on the application level.
This mechanism allows for the detection of replay attacks with access This mechanism allows for the detection of replay attacks with access
and refresh tokens. and refresh tokens.
Status of This Memo Status of This Memo
skipping to change at page 1, line 43 skipping to change at page 1, line 43
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on 22 May 2021. This Internet-Draft will expire on 9 October 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 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.
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Please review these documents carefully, as they describe your rights Please review these documents carefully, as they describe your rights
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions and Terminology . . . . . . . . . . . . . . . 3 1.1. Conventions and Terminology . . . . . . . . . . . . . . . 3
2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Objectives . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. DPoP Proof JWTs . . . . . . . . . . . . . . . . . . . . . . . 7 4. DPoP Proof JWTs . . . . . . . . . . . . . . . . . . . . . . . 7
4.1. The DPoP HTTP Header . . . . . . . . . . . . . . . . . . 7 4.1. The DPoP HTTP Header . . . . . . . . . . . . . . . . . . 7
4.2. DPoP Proof JWT Syntax . . . . . . . . . . . . . . . . . . 8 4.2. DPoP Proof JWT Syntax . . . . . . . . . . . . . . . . . . 8
4.3. Checking DPoP Proofs . . . . . . . . . . . . . . . . . . 9 4.3. Checking DPoP Proofs . . . . . . . . . . . . . . . . . . 10
5. DPoP Access Token Request . . . . . . . . . . . . . . . . . . 10 5. DPoP Access Token Request . . . . . . . . . . . . . . . . . . 10
5.1. Authorization Server Metadata . . . . . . . . . . . . . . 13 5.1. Authorization Server Metadata . . . . . . . . . . . . . . 13
6. Public Key Confirmation . . . . . . . . . . . . . . . . . . . 13 6. Public Key Confirmation . . . . . . . . . . . . . . . . . . . 13
6.1. JWK Thumbprint Confirmation Method . . . . . . . . . . . 14 6.1. JWK Thumbprint Confirmation Method . . . . . . . . . . . 14
6.2. JWK Thumbprint Confirmation Method in Token 6.2. JWK Thumbprint Confirmation Method in Token
Introspection . . . . . . . . . . . . . . . . . . . . . . 14 Introspection . . . . . . . . . . . . . . . . . . . . . . 14
7. Protected Resource Access . . . . . . . . . . . . . . . . . . 16 7. Protected Resource Access . . . . . . . . . . . . . . . . . . 16
7.1. The DPoP Authorization Request Header Scheme . . . . . . 16 7.1. The DPoP Authorization Request Header Scheme . . . . . . 16
7.2. The Bearer Authorization Request Header Scheme . . . . . 18 7.2. The Bearer Authorization Request Header Scheme . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8.1. DPoP Proof Replay . . . . . . . . . . . . . . . . . . . . 19 8.1. DPoP Proof Replay . . . . . . . . . . . . . . . . . . . . 19
8.2. Signed JWT Swapping . . . . . . . . . . . . . . . . . . . 19 8.2. Untrusted Code in the Client Context . . . . . . . . . . 20
8.3. Signature Algorithms . . . . . . . . . . . . . . . . . . 19 8.3. Signed JWT Swapping . . . . . . . . . . . . . . . . . . . 21
8.4. Message Integrity . . . . . . . . . . . . . . . . . . . . 20 8.4. Signature Algorithms . . . . . . . . . . . . . . . . . . 21
8.5. Public Key Binding . . . . . . . . . . . . . . . . . . . 20 8.5. Message Integrity . . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 8.6. Access Token and Public Key Binding . . . . . . . . . . . 22
9.1. OAuth Access Token Type Registration . . . . . . . . . . 20 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
9.2. HTTP Authentication Scheme Registration . . . . . . . . . 21 9.1. OAuth Access Token Type Registration . . . . . . . . . . 22
9.3. Media Type Registration . . . . . . . . . . . . . . . . . 21 9.2. HTTP Authentication Scheme Registration . . . . . . . . . 22
9.4. JWT Confirmation Methods Registration . . . . . . . . . . 21 9.3. Media Type Registration . . . . . . . . . . . . . . . . . 23
9.5. JSON Web Token Claims Registration . . . . . . . . . . . 22 9.4. JWT Confirmation Methods Registration . . . . . . . . . . 23
9.6. HTTP Message Header Field Names Registration . . . . . . 22 9.5. JSON Web Token Claims Registration . . . . . . . . . . . 23
9.7. Authorization Server Metadata Registration . . . . . . . 22 9.6. HTTP Message Header Field Names Registration . . . . . . 24
10. Normative References . . . . . . . . . . . . . . . . . . . . 23 9.7. Authorization Server Metadata Registration . . . . . . . 24
11. Informative References . . . . . . . . . . . . . . . . . . . 23 10. Normative References . . . . . . . . . . . . . . . . . . . . 25
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 26 11. Informative References . . . . . . . . . . . . . . . . . . . 25
Appendix B. Document History . . . . . . . . . . . . . . . . . . 27 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 Appendix B. Document History . . . . . . . . . . . . . . . . . . 29
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 31
1. Introduction 1. Introduction
DPoP, an abbreviation for Demonstrating Proof-of-Possession at the DPoP, an abbreviation for Demonstrating Proof-of-Possession at the
Application Layer, is an application-level mechanism for sender- Application Layer, is an application-level mechanism for sender-
constraining OAuth access and refresh tokens. It enables a client to constraining OAuth access and refresh tokens. It enables a client to
demonstrate proof-of-possession of a public/private key pair by demonstrate proof-of-possession of a public/private key pair by
including a "DPoP" header in an HTTP request. The value of the including a "DPoP" header in an HTTP request. The value of the
header is a JWT [RFC7519] that enables the authorization server to header is a JWT [RFC7519] that enables the authorization server to
bind issued tokens to the public part of the client's key pair. bind issued tokens to the public part of a client's key pair.
Recipients of such tokens are then able to verify the binding of the Recipients of such tokens are then able to verify the binding of the
token to the key pair that the client has demonstrated that it holds token to the key pair that the client has demonstrated that it holds
via the "DPoP" header, thereby providing some assurance that the via the "DPoP" header, thereby providing some assurance that the
client presenting the token also possesses the private key. In other client presenting the token also possesses the private key. In other
words, the legitimate presenter of the token is constrained to be the words, the legitimate presenter of the token is constrained to be the
sender that holds and can prove possession of the private part of the sender that holds and can prove possession of the private part of the
key pair. key pair.
The mechanism described herein can be used in cases where other The mechanism described herein can be used in cases where other
methods of sender-constraining tokens that utilize elements of the methods of sender-constraining tokens that utilize elements of the
underlying secure transport layer, such as [RFC8705] or underlying secure transport layer, such as [RFC8705] or
[I-D.ietf-oauth-token-binding], are not available or desirable. For [I-D.ietf-oauth-token-binding], are not available or desirable. For
example, due to a sub-par user experience of TLS client example, due to a sub-par user experience of TLS client
authentication in user agents and a lack of support for HTTP token authentication in user agents and a lack of support for HTTP token
binding, neither mechanism can be used if an OAuth client is a Single binding, neither mechanism can be used if an OAuth client is a Single
Page Application (SPA) running in a web browser. Native applications Page Application (SPA) running in a web browser. Native applications
installed and run on a user's device, which often have dedicated installed and run on a user's device, which often have dedicated
protected storage for cryptographic keys. are another example well protected storage for cryptographic keys are another example well
positioned to benefit from DPoP-bound tokens to guard against misuse positioned to benefit from DPoP-bound tokens to guard against misuse
of tokens by a compromised or malicious resource. of tokens by a compromised or malicious resource.
DPoP can be used to sender-constrain access tokens regardless of the DPoP can be used to sender-constrain access tokens regardless of the
client authentication method employed. Furthermore, DPoP can also be client authentication method employed. Furthermore, DPoP can also be
used to sender-constrain refresh tokens issued to public clients used to sender-constrain refresh tokens issued to public clients
(those without authentication credentials associated with the (those without authentication credentials associated with the
"client_id"). "client_id").
1.1. Conventions and Terminology 1.1. Conventions and Terminology
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protecting tokens. The most straightforward XSS-based attack is for protecting tokens. The most straightforward XSS-based attack is for
an attacker to exfiltrate a token and use it themselves completely an attacker to exfiltrate a token and use it themselves completely
independent from the legitimate client. A stolen access token is independent from the legitimate client. A stolen access token is
used for protected resource access and a stolen refresh token for used for protected resource access and a stolen refresh token for
obtaining new access tokens. If the private key is non-extractable obtaining new access tokens. If the private key is non-extractable
(as is possible with [W3C.WebCryptoAPI]), DPoP renders exfiltrated (as is possible with [W3C.WebCryptoAPI]), DPoP renders exfiltrated
tokens alone unusable. tokens alone unusable.
XXS vulnerabilities also allow an attacker to execute code in the XXS vulnerabilities also allow an attacker to execute code in the
context of the browser-based client application and maliciously use a context of the browser-based client application and maliciously use a
token indirectly through the the client. That execution context has token indirectly through the client. That execution context has
access to utilize the signing key and thus can produce DPoP proofs to access to utilize the signing key and thus can produce DPoP proofs to
use in conjunction with the token. At this application layer there use in conjunction with the token. At this application layer there
is most likely no feasible defense against this threat except is most likely no feasible defense against this threat except
generally preventing XSS, therefore it is considered out of scope for generally preventing XSS, therefore it is considered out of scope for
DPoP. DPoP.
Malicious XSS code executed in the context of the browser-based Malicious XSS code executed in the context of the browser-based
client application is also in a position to create DPoP proofs with client application is also in a position to create DPoP proofs with
timestamp values in the future and exfiltrate them in conjunction timestamp values in the future and exfiltrate them in conjunction
with a token. These stolen artifacts can later be used together with a token. These stolen artifacts can later be used together
independent of the client application to access protected resources. independent of the client application to access protected resources.
The impact of such precomputed DPoP proofs can be limited somewhat by The impact of such precomputed DPoP proofs is limited somewhat by the
a browser-based client generating and using a new DPoP key for each proof being bound to an access token on protected resource access.
new authorization code grant. Because a proof covering an access token that don't yet exist cannot
feasibly be created, access tokens obtained with an exfiltrated
refresh token and pre-computed proofs will be unusable.
Additional security considerations are discussed in Section 8. Additional security considerations are discussed in Section 8.
3. Concept 3. Concept
The main data structure introduced by this specification is a DPoP The main data structure introduced by this specification is a DPoP
proof JWT, described in detail below, which is sent as a header in an proof JWT, described in detail below, which is sent as a header in an
HTTP request. A client uses a DPoP proof JWT to prove the possession HTTP request. A client uses a DPoP proof JWT to prove the possession
of a private key corresponding to a certain public key. Roughly of a private key corresponding to a certain public key. Roughly
speaking, a DPoP proof is a signature over a timestamp and some data speaking, a DPoP proof is a signature over a timestamp and some data
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* (B) The authorization server binds (sender-constrains) the access * (B) The authorization server binds (sender-constrains) the access
token to the public key claimed by the client in the DPoP proof; token to the public key claimed by the client in the DPoP proof;
that is, the access token cannot be used without proving that is, the access token cannot be used without proving
possession of the respective private key. If a refresh token is possession of the respective private key. If a refresh token is
issued to a public client, it too is bound to the public key of issued to a public client, it too is bound to the public key of
the DPoP proof. the DPoP proof.
* (C) To use the access token the client has to prove possession of * (C) To use the access token the client has to prove possession of
the private key by, again, adding a header to the request that the private key by, again, adding a header to the request that
carries the DPoP proof. The resource server needs to receive carries a DPoP proof for that request. The resource server needs
information about the public key to which the access token is to receive information about the public key to which the access
bound. This information may be encoded directly into the access token is bound. This information may be encoded directly into the
token (for JWT structured access tokens) or provided via token access token (for JWT structured access tokens) or provided via
introspection endpoint (not shown). The resource server verifies token introspection endpoint (not shown). The resource server
that the public key to which the access token is bound matches the verifies that the public key to which the access token is bound
public key of the DPoP proof. matches the public key of the DPoP proof.
* (D) The resource server refuses to serve the request if the * (D) The resource server refuses to serve the request if the
signature check fails or the data in the DPoP proof is wrong, signature check fails or the data in the DPoP proof is wrong,
e.g., the request URI does not match the URI claim in the DPoP e.g., the request URI does not match the URI claim in the DPoP
proof JWT. The access token itself, of course, must also be valid proof JWT. The access token itself, of course, must also be valid
in all other respects. in all other respects.
The DPoP mechanism presented herein is not a client authentication The DPoP mechanism presented herein is not a client authentication
method. In fact, a primary use case of DPoP is for public clients method. In fact, a primary use case of DPoP is for public clients
(e.g., single page applications and native applications) that do not (e.g., single page applications and native applications) that do not
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it is compatible with "private_key_jwt" and all other client it is compatible with "private_key_jwt" and all other client
authentication methods. authentication methods.
DPoP does not directly ensure message integrity but relies on the TLS DPoP does not directly ensure message integrity but relies on the TLS
layer for that purpose. See Section 8 for details. layer for that purpose. See Section 8 for details.
4. DPoP Proof JWTs 4. DPoP Proof JWTs
DPoP introduces the concept of a DPoP proof, which is a JWT created DPoP introduces the concept of a DPoP proof, which is a JWT created
by the client and sent with an HTTP request using the "DPoP" header by the client and sent with an HTTP request using the "DPoP" header
field. A valid DPoP proof demonstrates to the server that the client field. Each HTTP request requires a unique DPoP proof. A valid DPoP
holds the private key that was used to sign the JWT. This enables proof demonstrates to the server that the client holds the private
key that was used to sign the DPoP proof JWT. This enables
authorization servers to bind issued tokens to the corresponding authorization servers to bind issued tokens to the corresponding
public key (as described in Section 5) and for resource servers to public key (as described in Section 5) and for resource servers to
verify the key-binding of tokens that it receives (see Section 7.1), verify the key-binding of tokens that it receives (see Section 7.1),
which prevents said tokens from being used by any entity that does which prevents said tokens from being used by any entity that does
not have access to the private key. not have access to the private key.
The DPoP proof demonstrates possession of a key and, by itself, is The DPoP proof demonstrates possession of a key and, by itself, is
not an authentication or access control mechanism. When presented in not an authentication or access control mechanism. When presented in
conjunction with a key-bound access token as described in conjunction with a key-bound access token as described in
Section 7.1, the DPoP proof provides additional assurance about the Section 7.1, the DPoP proof provides additional assurance about the
legitimacy of the client to present the access token. But a valid legitimacy of the client to present the access token. However, a
DPoP proof JWT is not sufficient alone to make access control valid DPoP proof JWT is not sufficient alone to make access control
decisions. decisions.
4.1. The DPoP HTTP Header 4.1. The DPoP HTTP Header
A DPoP proof is included in an HTTP request using the following A DPoP proof is included in an HTTP request using the following
message header field. message header field.
"DPoP" A JWT that adheres to the structure and syntax of "DPoP" A JWT that adheres to the structure and syntax of
Section 4.2. Section 4.2.
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[RFC7515]) with a private key chosen by the client (see below). The [RFC7515]) with a private key chosen by the client (see below). The
header of a DPoP JWT contains at least the following parameters: header of a DPoP JWT contains at least the following parameters:
* "typ": type header, value "dpop+jwt" (REQUIRED). * "typ": type header, value "dpop+jwt" (REQUIRED).
* "alg": a digital signature algorithm identifier as per [RFC7518] * "alg": a digital signature algorithm identifier as per [RFC7518]
(REQUIRED). MUST NOT be "none" or an identifier for a symmetric (REQUIRED). MUST NOT be "none" or an identifier for a symmetric
algorithm (MAC). algorithm (MAC).
* "jwk": representing the public key chosen by the client, in JWK * "jwk": representing the public key chosen by the client, in JWK
format, as defined in [RFC7515] (REQUIRED) format, as defined in Section 4.1.3 of [RFC7515] (REQUIRED). MUST
NOT contain the private key.
The body of a DPoP proof contains at least the following claims: The payload of a DPoP proof contains at least the following claims:
* "jti": Unique identifier for the DPoP proof JWT (REQUIRED). The * "jti": Unique identifier for the DPoP proof JWT (REQUIRED). The
value MUST be assigned such that there is a negligible probability value MUST be assigned such that there is a negligible probability
that the same value will be assigned to any other DPoP proof used that the same value will be assigned to any other DPoP proof used
in the same context during the time window of validity. Such in the same context during the time window of validity. Such
uniqueness can be accomplished by encoding (base64url or any other uniqueness can be accomplished by encoding (base64url or any other
suitable encoding) at least 96 bits of pseudorandom data or by suitable encoding) at least 96 bits of pseudorandom data or by
using a version 4 UUID string according to [RFC4122]. The "jti" using a version 4 UUID string according to [RFC4122]. The "jti"
can be used by the server for replay detection and prevention, see can be used by the server for replay detection and prevention, see
Section 8.1. Section 8.1.
* "htm": The HTTP method for the request to which the JWT is * "htm": The HTTP method for the request to which the JWT is
attached, as defined in [RFC7231] (REQUIRED). attached, as defined in [RFC7231] (REQUIRED).
* "htu": The HTTP URI used for the request, without query and * "htu": The HTTP URI used for the request, without query and
fragment parts (REQUIRED). fragment parts (REQUIRED).
* "iat": Time at which the JWT was created (REQUIRED). * "iat": Time at which the JWT was created (REQUIRED).
When the DPoP proof is used in conjunction with the presentation of
an access token, see Section 7, the DPoP proof also contains the
following claim:
* "ath": hash of the access token (REQUIRED). The value MUST be the
result of a base64url encoding (with no padding) the SHA-256 hash
of the ASCII encoding of the associated access token's value.
Figure 3 is a conceptual example showing the decoded content of the Figure 3 is a conceptual example showing the decoded content of the
DPoP proof in Figure 2. The JSON of the JOSE header and payload are DPoP proof in Figure 2. The JSON of the JOSE header and payload are
shown but the signature part is omitted. As usual, line breaks and shown but the signature part is omitted. As usual, line breaks and
extra whitespace are included for formatting and readability. extra whitespace are included for formatting and readability.
{ {
"typ":"dpop+jwt", "typ":"dpop+jwt",
"alg":"ES256", "alg":"ES256",
"jwk": { "jwk": {
"kty":"EC", "kty":"EC",
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Figure 3: Example JWT content of a "DPoP" proof Figure 3: Example JWT content of a "DPoP" proof
Of the HTTP content in the request, only the HTTP method and URI are Of the HTTP content in the request, only the HTTP method and URI are
included in the DPoP JWT, and therefore only these 2 headers of the included in the DPoP JWT, and therefore only these 2 headers of the
request are covered by the DPoP proof and its signature. The idea is request are covered by the DPoP proof and its signature. The idea is
sign just enough of the HTTP data to provide reasonable proof-of- sign just enough of the HTTP data to provide reasonable proof-of-
possession with respect to the HTTP request. But that it be a possession with respect to the HTTP request. But that it be a
minimal subset of the HTTP data so as to avoid the substantial minimal subset of the HTTP data so as to avoid the substantial
difficulties inherent in attempting to normalize HTTP messages. difficulties inherent in attempting to normalize HTTP messages.
Nonetheless, DPoP proofs can be extended to contain other information Nonetheless, DPoP proofs can be extended to contain other information
of the HTTP request (see also Section 8.4). of the HTTP request (see also Section 8.5).
4.3. Checking DPoP Proofs 4.3. Checking DPoP Proofs
To check if a string that was received as part of an HTTP Request is To check if a string that was received as part of an HTTP Request is
a valid DPoP proof, the receiving server MUST ensure that a valid DPoP proof, the receiving server MUST ensure that
1. the string value is a well-formed JWT, 1. the string value is a well-formed JWT,
2. all required claims are contained in the JWT, 2. all required claims per Section 4.2 are contained in the JWT,
3. the "typ" field in the header has the value "dpop+jwt", 3. the "typ" field in the header has the value "dpop+jwt",
4. the algorithm in the header of the JWT indicates an asymmetric 4. the algorithm in the header of the JWT indicates an asymmetric
digital signature algorithm, is not "none", is supported by the digital signature algorithm, is not "none", is supported by the
application, and is deemed secure, application, and is deemed secure,
5. that the JWT is signed using the public key contained in the 5. the JWT signature verifies with the public key contained in the
"jwk" header of the JWT, "jwk" header of the JWT,
6. the "htm" claim matches the HTTP method value of the HTTP request 6. the "htm" claim matches the HTTP method value of the HTTP request
in which the JWT was received, in which the JWT was received,
7. the "htu" claims matches the HTTPS URI value for the HTTP request 7. the "htu" claims matches the HTTPS URI value for the HTTP request
in which the JWT was received, ignoring any query and fragment in which the JWT was received, ignoring any query and fragment
parts, parts,
8. the token was issued within an acceptable timeframe (see 8. the token was issued within an acceptable timeframe and, within a
Section 8.1), and reasonable consideration of accuracy and resource utilization, a
proof JWT with the same "jti" value has not previously been
9. that, within a reasonable consideration of accuracy and resource received at the same resource during that time period (see
utilization, a JWT with the same "jti" value has not previously Section 8.1).
been received at the same URI (see Section 8.1).
Servers SHOULD employ Syntax-Based Normalization and Scheme-Based Servers SHOULD employ Syntax-Based Normalization and Scheme-Based
Normalization in accordance with Section 6.2.2. and Section 6.2.3. of Normalization in accordance with Section 6.2.2. and Section 6.2.3. of
[RFC3986] before comparing the "htu" claim. [RFC3986] before comparing the "htu" claim.
If presented with an access token to a protected resource, the server
MUST ensure that the value of the "ath" claim equals the hash of the
access token that has been presented along side the DPoP proof.
5. DPoP Access Token Request 5. DPoP Access Token Request
To request an access token that is bound to a public key using DPoP, To request an access token that is bound to a public key using DPoP,
the client MUST provide a valid DPoP proof JWT in a "DPoP" header the client MUST provide a valid DPoP proof JWT in a "DPoP" header
when making an access token request to the authorization server's when making an access token request to the authorization server's
token endpoint. This is applicable for all access token requests token endpoint. This is applicable for all access token requests
regardless of grant type (including, for example, the common regardless of grant type (including, for example, the common
"authorization_code" and "refresh_token" grant types but also "authorization_code" and "refresh_token" grant types but also
extension grants such as the JWT authorization grant [RFC7523]). The extension grants such as the JWT authorization grant [RFC7523]). The
HTTPS request shown in Figure 4 illustrates an such an access token HTTPS request shown in Figure 4 illustrates such an access token
request using an an authorization code grant with a DPoP proof JWT in request using an authorization code grant with a DPoP proof JWT in
the "DPoP" header (extra line breaks and whitespace for display the "DPoP" header (extra line breaks and whitespace for display
purposes only). purposes only).
POST /token HTTP/1.1 POST /token HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/x-www-form-urlencoded;charset=UTF-8 Content-Type: application/x-www-form-urlencoded;charset=UTF-8
DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik
VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR
nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE
QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj
skipping to change at page 11, line 22 skipping to change at page 11, line 43
To sender-constrain the access token, after checking the validity of To sender-constrain the access token, after checking the validity of
the DPoP proof, the authorization server associates the issued access the DPoP proof, the authorization server associates the issued access
token with the public key from the DPoP proof, which can be token with the public key from the DPoP proof, which can be
accomplished as described in Section 6. A "token_type" of "DPoP" in accomplished as described in Section 6. A "token_type" of "DPoP" in
the access token response signals to the client that the access token the access token response signals to the client that the access token
was bound to its DPoP key and can used as described in Section 7.1. was bound to its DPoP key and can used as described in Section 7.1.
The example response shown in Figure 5 illustrates such a response. The example response shown in Figure 5 illustrates such a response.
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Cache-Control: no-cache, no-store Cache-Control: no-store
{ {
"access_token": "Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU", "access_token": "Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU",
"token_type": "DPoP", "token_type": "DPoP",
"expires_in": 2677, "expires_in": 2677,
"refresh_token": "Q..Zkm29lexi8VnWg2zPW1x-tgGad0Ibc3s3EwM_Ni4-g" "refresh_token": "Q..Zkm29lexi8VnWg2zPW1x-tgGad0Ibc3s3EwM_Ni4-g"
} }
Figure 5: Access Token Response Figure 5: Access Token Response
The example response in Figure 5 included a refresh token, which the The example response in Figure 5 included a refresh token, which the
client can use to obtain a new access token when the the previous one client can use to obtain a new access token when the previous one
expires. Refreshing an access token is a token request using the expires. Refreshing an access token is a token request using the
"refresh_token" grant type made to the the authorization server's "refresh_token" grant type made to the authorization server's token
token endpoint. As with all access token requests, the client makes endpoint. As with all access token requests, the client makes it a
it a DPoP request by including a DPoP proof, which is shown in the DPoP request by including a DPoP proof, which is shown in the
Figure 6 example (extra line breaks and whitespace for display Figure 6 example (extra line breaks and whitespace for display
purposes only). purposes only).
POST /token HTTP/1.1 POST /token HTTP/1.1
Host: server.example.com Host: server.example.com
Content-Type: application/x-www-form-urlencoded;charset=UTF-8 Content-Type: application/x-www-form-urlencoded;charset=UTF-8
DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik
VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR
nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE
QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiItQndDM0VTYzZhY2MybFRjIiwiaHRtIj
skipping to change at page 13, line 5 skipping to change at page 13, line 5
of the binding. of the binding.
An authorization server MAY elect to issue access tokens which are An authorization server MAY elect to issue access tokens which are
not DPoP bound, which is signaled to the client with a value of not DPoP bound, which is signaled to the client with a value of
"Bearer" in the "token_type" parameter of the access token response "Bearer" in the "token_type" parameter of the access token response
per [RFC6750]. For a public client that is also issued a refresh per [RFC6750]. For a public client that is also issued a refresh
token, this has the effect of DPoP-binding the refresh token alone, token, this has the effect of DPoP-binding the refresh token alone,
which can improve the security posture even when protected resources which can improve the security posture even when protected resources
are not updated to support DPoP. are not updated to support DPoP.
A client expecting a DPoP-bound access token MAY discard the
response, if a "Bearer" token type is received.
Refresh tokens issued to confidential clients (those having Refresh tokens issued to confidential clients (those having
established authentication credentials with the authorization server) established authentication credentials with the authorization server)
are not bound to the DPoP proof public key because they are already are not bound to the DPoP proof public key because they are already
sender-constrained with a different existing mechanism. The OAuth sender-constrained with a different existing mechanism. The OAuth
2.0 Authorization Framework [RFC6749] already requires that an 2.0 Authorization Framework [RFC6749] already requires that an
authorization server bind refresh tokens to the client to which they authorization server bind refresh tokens to the client to which they
were issued and that confidential clients authenticate to the were issued and that confidential clients authenticate to the
authorization server when presenting a refresh token. As a result, authorization server when presenting a refresh token. As a result,
such refresh tokens are sender-constrained by way of the client ID such refresh tokens are sender-constrained by way of the client ID
and the associated authentication requirement. This existing sender- and the associated authentication requirement. This existing sender-
skipping to change at page 13, line 35 skipping to change at page 13, line 38
"dpop_signing_alg_values_supported" A JSON array containing a list "dpop_signing_alg_values_supported" A JSON array containing a list
of the JWS "alg" values supported by the authorization server for of the JWS "alg" values supported by the authorization server for
DPoP proof JWTs. DPoP proof JWTs.
6. Public Key Confirmation 6. Public Key Confirmation
Resource servers MUST be able to reliably identify whether an access Resource servers MUST be able to reliably identify whether an access
token is bound using DPoP and ascertain sufficient information about token is bound using DPoP and ascertain sufficient information about
the public key to which the token is bound in order to verify the the public key to which the token is bound in order to verify the
binding with respect to the the presented DPoP proof (see binding with respect to the presented DPoP proof (see Section 7.1).
Section 7.1). Such a binding is accomplished by associating the Such a binding is accomplished by associating the public key with the
public key with the token in a way that can be accessed by the token in a way that can be accessed by the protected resource, such
protected resource, such as embedding the JWK hash in the issued as embedding the JWK hash in the issued access token directly, using
access token directly, using the syntax described in Section 6.1, or the syntax described in Section 6.1, or through token introspection
through token introspection as described in Section 6.2. Other as described in Section 6.2. Other methods of associating a public
methods of associating a public key with an access token are key with an access token are possible, per agreement by the
possible, per agreement by the authorization server and the protected authorization server and the protected resource, but are beyond the
resource, but are beyond the scope of this specification. scope of this specification.
Resource servers supporting DPoP MUST ensure that the the public key Resource servers supporting DPoP MUST ensure that the public key from
from the DPoP proof matches the pubic key to which the access token the DPoP proof matches the public key to which the access token is
is bound. bound.
6.1. JWK Thumbprint Confirmation Method 6.1. JWK Thumbprint Confirmation Method
When access tokens are represented as JSON Web Tokens (JWT) When access tokens are represented as JSON Web Tokens (JWT)
[RFC7519], the public key information SHOULD be represented using the [RFC7519], the public key information SHOULD be represented using the
"jkt" confirmation method member defined herein. To convey the hash "jkt" confirmation method member defined herein. To convey the hash
of a public key in a JWT, this specification introduces the following of a public key in a JWT, this specification introduces the following
new JWT Confirmation Method [RFC7800] member for use under the "cnf" new JWT Confirmation Method [RFC7800] member for use under the "cnf"
claim. claim.
skipping to change at page 15, line 32 skipping to change at page 15, line 32
Host: server.example.com Host: server.example.com
Content-Type: application/x-www-form-urlencoded Content-Type: application/x-www-form-urlencoded
Authorization: Basic cnM6cnM6TWt1LTZnX2xDektJZHo0ZnNON2tZY3lhK1Rp Authorization: Basic cnM6cnM6TWt1LTZnX2xDektJZHo0ZnNON2tZY3lhK1Rp
token=Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU token=Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU
Figure 9: Example Introspection Request Figure 9: Example Introspection Request
HTTP/1.1 200 OK HTTP/1.1 200 OK
Content-Type: application/json Content-Type: application/json
Cache-Control: no-cache, no-store Cache-Control: no-store
{ {
"active": true, "active": true,
"sub": "someone@example.com", "sub": "someone@example.com",
"iss": "https://server.example.com", "iss": "https://server.example.com",
"nbf": 1562262611, "nbf": 1562262611,
"exp": 1562266216, "exp": 1562266216,
"cnf": {"jkt": "0ZcOCORZNYy-DWpqq30jZyJGHTN0d2HglBV3uiguA4I"} "cnf": {"jkt": "0ZcOCORZNYy-DWpqq30jZyJGHTN0d2HglBV3uiguA4I"}
} }
Figure 10: Example Introspection Response for a DPoP-Bound Access Figure 10: Example Introspection Response for a DPoP-Bound Access
Token Token
7. Protected Resource Access 7. Protected Resource Access
To make use of an access token that is bound to a public key using To make use of an access token that is bound to a public key using
DPoP, a client MUST prove possession of the corresponding private key DPoP, a client MUST prove possession of the corresponding private key
by providing a DPoP proof in the "DPoP" request header. As such, by providing a DPoP proof in the "DPoP" request header. As such,
protected resource requests with a DPoP-bound access token protected resource requests with a DPoP-bound access token
necessarily must include both a DPoP proof as per Section 4 and the necessarily must include both a DPoP proof as per Section 4 and the
access token as described in Section 7.1. access token as described in Section 7.1. The DPoP proof MUST
include the "ath" claim with a valid hash of the associated access
token.
7.1. The DPoP Authorization Request Header Scheme 7.1. The DPoP Authorization Request Header Scheme
A DPoP-bound access token is sent using the "Authorization" request A DPoP-bound access token is sent using the "Authorization" request
header field per Section 2 of [RFC7235] using an authentication header field per Section 2 of [RFC7235] using an authentication
scheme of "DPoP". The syntax of the "Authorization" header field for scheme of "DPoP". The syntax of the "Authorization" header field for
the "DPoP" scheme uses the "token68" syntax defined in Section 2.1 of the "DPoP" scheme uses the "token68" syntax defined in Section 2.1 of
[RFC7235] (repeated below for ease of reference) for credentials. [RFC7235] (repeated below for ease of reference) for credentials.
The Augmented Backus-Naur Form (ABNF) notation [RFC5234] syntax for The Augmented Backus-Naur Form (ABNF) notation [RFC5234] syntax for
DPoP Authorization scheme credentials is as follows: DPoP Authorization scheme credentials is as follows:
skipping to change at page 16, line 42 skipping to change at page 16, line 44
proof was also received in the "DPoP" header field of the HTTP proof was also received in the "DPoP" header field of the HTTP
request, check the DPoP proof according to the rules in Section 4.3, request, check the DPoP proof according to the rules in Section 4.3,
and check that the public key of the DPoP proof matches the public and check that the public key of the DPoP proof matches the public
key to which the access token is bound per Section 6. key to which the access token is bound per Section 6.
The resource server MUST NOT grant access to the resource unless all The resource server MUST NOT grant access to the resource unless all
checks are successful. checks are successful.
Figure 12 shows an example request to a protected resource with a Figure 12 shows an example request to a protected resource with a
DPoP-bound access token in the "Authorization" header and the DPoP DPoP-bound access token in the "Authorization" header and the DPoP
proof in the "DPoP" header (line breaks and extra whitespace for proof in the "DPoP" header. Following that is Figure 13, which shows
display purposes only). the decoded content of that DPoP proof. The JSON of the JOSE header
and payload are shown but the signature part is omitted. As usual,
line breaks and extra whitespace are included for formatting and
readability in both examples.
GET /protectedresource HTTP/1.1 GET /protectedresource HTTP/1.1
Host: resource.example.org Host: resource.example.org
Authorization: DPoP Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU Authorization: DPoP Kz~8mXK1EalYznwH-LC-1fBAo.4Ljp~zsPE_NeO.gxU
DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik DPoP: eyJ0eXAiOiJkcG9wK2p3dCIsImFsZyI6IkVTMjU2IiwiandrIjp7Imt0eSI6Ik
VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR VDIiwieCI6Imw4dEZyaHgtMzR0VjNoUklDUkRZOXpDa0RscEJoRjQyVVFVZldWQVdCR
nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE nMiLCJ5IjoiOVZFNGpmX09rX282NHpiVFRsY3VOSmFqSG10NnY5VERWclUwQ2R2R1JE
QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiJlMWozVl9iS2ljOC1MQUVCIiwiaHRtIj QSIsImNydiI6IlAtMjU2In19.eyJqdGkiOiJlMWozVl9iS2ljOC1MQUVCIiwiaHRtIj
oiR0VUIiwiaHR1IjoiaHR0cHM6Ly9yZXNvdXJjZS5leGFtcGxlLm9yZy9wcm90ZWN0Z oiR0VUIiwiaHR1IjoiaHR0cHM6Ly9yZXNvdXJjZS5leGFtcGxlLm9yZy9wcm90ZWN0Z
WRyZXNvdXJjZSIsImlhdCI6MTU2MjI2MjYxOH0.lNhmpAX1WwmpBvwhok4E74kWCiGB WRyZXNvdXJjZSIsImlhdCI6MTU2MjI2MjYxOCwiYXRoIjoiZlVIeU8ycjJaM0RaNTNF
NdavjLAeevGy32H3dbF0Jbri69Nm2ukkwb-uyUI4AUg1JSskfWIyo4UCbQ c05yV0JiMHhXWG9hTnk1OUlpS0NBcWtzbVFFbyJ9.2oW9RP35yRqzhrtNP86L-Ey71E
OptxRimPPToA1plemAgR6pxHF8y6-yqyVnmcw6Fy1dqd-jfxSYoMxhAJpLjA
Figure 12: DPoP Protected Resource Request Figure 12: DPoP Protected Resource Request
{
"typ":"dpop+jwt",
"alg":"ES256",
"jwk": {
"kty":"EC",
"x":"l8tFrhx-34tV3hRICRDY9zCkDlpBhF42UQUfWVAWBFs",
"y":"9VE4jf_Ok_o64zbTTlcuNJajHmt6v9TDVrU0CdvGRDA",
"crv":"P-256"
}
}
.
{
"jti":"e1j3V_bKic8-LAEB",
"htm":"GET",
"htu":"https://resource.example.org/protectedresource",
"iat":1562262618,
"ath":"fUHyO2r2Z3DZ53EsNrWBb0xWXoaNy59IiKCAqksmQEo"
}
Figure 13: Decoded Content of the "DPoP" proof JWT in Figure 12
Upon receipt of a request for a URI of a protected resource within Upon receipt of a request for a URI of a protected resource within
the protection space requiring DPoP authorization, if the request the protection space requiring DPoP authorization, if the request
does not include valid credentials or does not contain an access does not include valid credentials or does not contain an access
token sufficient for access to the protected resource, the server can token sufficient for access to the protected resource, the server can
reply with a challenge using the 401 (Unauthorized) status code reply with a challenge using the 401 (Unauthorized) status code
([RFC7235], Section 3.1) and the "WWW-Authenticate" header field ([RFC7235], Section 3.1) and the "WWW-Authenticate" header field
([RFC7235], Section 4.1). The server MAY include the "WWW- ([RFC7235], Section 4.1). The server MAY include the "WWW-
Authenticate" header in response to other conditions as well. Authenticate" header in response to other conditions as well.
In such challenges: In such challenges:
skipping to change at page 18, line 14 skipping to change at page 18, line 36
* Additional authentication parameters MAY be used and unknown * Additional authentication parameters MAY be used and unknown
parameters MUST be ignored by recipients parameters MUST be ignored by recipients
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: DPoP realm="WallyWorld", algs="ES256 PS256" WWW-Authenticate: DPoP realm="WallyWorld", algs="ES256 PS256"
Figure 13: HTTP 401 Response To A Protected Resource Request Without Figure 14: HTTP 401 Response To A Protected Resource Request Without
Authentication Authentication
And in response to a protected resource request that was rejected And in response to a protected resource request that was rejected
because the confirmation of the DPoP binding in the access token because the confirmation of the DPoP binding in the access token
failed: failed:
HTTP/1.1 401 Unauthorized HTTP/1.1 401 Unauthorized
WWW-Authenticate: DPoP realm="WallyWorld", error="invalid_token", WWW-Authenticate: DPoP realm="WallyWorld", error="invalid_token",
error_description="Invalid DPoP key binding", algs="ES256" error_description="Invalid DPoP key binding", algs="ES256"
Figure 14: HTTP 401 Response To A Protected Resource Request With Figure 15: HTTP 401 Response To A Protected Resource Request With
An Invalid Token An Invalid Token
7.2. The Bearer Authorization Request Header Scheme 7.2. The Bearer Authorization Request Header Scheme
Protected resources simultaneously supporting both the "DPoP" and Protected resources simultaneously supporting both the "DPoP" and
"Bearer" schemes need to update how evaluation of bearer tokens is "Bearer" schemes need to update how evaluation of bearer tokens is
performed to prevent downgraded usage of a DPoP-bound access tokens. performed to prevent downgraded usage of a DPoP-bound access tokens.
Specifically, such a protected resource MUST reject an access token Specifically, such a protected resource MUST reject an access token
received as a bearer token per [!@RFC6750], if that token is received as a bearer token per [!@RFC6750], if that token is
determined to be DPoP-bound. determined to be DPoP-bound.
skipping to change at page 19, line 12 skipping to change at page 19, line 36
prolonged deployments of protected resources with mixed token type prolonged deployments of protected resources with mixed token type
support. support.
8. Security Considerations 8. Security Considerations
In DPoP, the prevention of token replay at a different endpoint (see In DPoP, the prevention of token replay at a different endpoint (see
Section 2) is achieved through the binding of the DPoP proof to a Section 2) is achieved through the binding of the DPoP proof to a
certain URI and HTTP method. DPoP, however, has a somewhat different certain URI and HTTP method. DPoP, however, has a somewhat different
nature of protection than TLS-based methods such as OAuth Mutual TLS nature of protection than TLS-based methods such as OAuth Mutual TLS
[RFC8705] or OAuth Token Binding [I-D.ietf-oauth-token-binding] (see [RFC8705] or OAuth Token Binding [I-D.ietf-oauth-token-binding] (see
also Section 8.1 and Section 8.4). TLS-based mechanisms can leverage also Section 8.1 and Section 8.5). TLS-based mechanisms can leverage
a tight integration between the TLS layer and the application layer a tight integration between the TLS layer and the application layer
to achieve a very high level of message integrity with respect to the to achieve a very high level of message integrity with respect to the
transport layer to which the token is bound and replay protection in transport layer to which the token is bound and replay protection in
general. general.
8.1. DPoP Proof Replay 8.1. DPoP Proof Replay
If an adversary is able to get hold of a DPoP proof JWT, the If an adversary is able to get hold of a DPoP proof JWT, the
adversary could replay that token at the same endpoint (the HTTP adversary could replay that token at the same endpoint (the HTTP
endpoint and method are enforced via the respective claims in the endpoint and method are enforced via the respective claims in the
JWTs). To prevent this, servers MUST only accept DPoP proofs for a JWTs). To prevent this, servers MUST only accept DPoP proofs for a
limited time window after their "iat" time, preferably only for a limited time window after their "iat" time, preferably only for a
relatively brief period. Servers SHOULD store, in the context of the relatively brief period (on the order of a few seconds). Servers
request URI, the "jti" value of each DPoP proof for the time window SHOULD store, in the context of the request URI, the "jti" value of
in which the respective DPoP proof JWT would be accepted and decline each DPoP proof for the time window in which the respective DPoP
HTTP requests to the same URI for which the "jti" value has been seen proof JWT would be accepted and decline HTTP requests to the same URI
before. In order to guard against memory exhaustion attacks a server for which the "jti" value has been seen before. In order to guard
SHOULD reject DPoP proof JWTs with unnecessarily large "jti" values against memory exhaustion attacks a server SHOULD reject DPoP proof
or store only a hash thereof. JWTs with unnecessarily large "jti" values or store only a hash
thereof.
Note: To accommodate for clock offsets, the server MAY accept DPoP Note: To accommodate for clock offsets, the server MAY accept DPoP
proofs that carry an "iat" time in the reasonably near future (e.g., proofs that carry an "iat" time in the reasonably near future (e.g.,
a few seconds in the future). a few seconds in the future).
8.2. Signed JWT Swapping 8.2. Untrusted Code in the Client Context
If an adversary is able to run code in the client's execution
context, the security of DPoP is no longer guaranteed. Common issues
in web applications leading to the execution of untrusted code are
cross-site scripting and remote code inclusion attacks.
If the private key used for DPoP is stored in such a way that it
cannot be exported, e.g., in a hardware or software security module,
the adversary cannot exfiltrate the key and use it to create
arbitrary DPoP proofs. The adversary can, however, create new DPoP
proofs as long as the client is online, and use these proofs
(together with the respective tokens) either on the victim's device
or on a device under the attacker's control to send arbitrary
requests that will be accepted by servers.
To send requests even when the client is offline, an adversary can
try to pre-compute DPoP proofs using timestamps in the future and
exfiltrate these together with the access or refresh token.
An adversary might further try to associate tokens issued from the
token endpoint with a key pair under the adversary's control. One
way to achieve this is to modify existing code, e.g., by replacing
cryptographic APIs. Another way is to launch a new authorization
grant between the client and the authorization server in an iframe.
This grant needs to be "silent", i.e., not require interaction with
the user. With code running in the client's origin, the adversary
has access to the resulting authorization code and can use it to
associate their own DPoP keys with the tokens returned from the token
endpoint. The adversary is then able to use the resulting tokens on
their own device even if the client is offline.
Therefore, protecting clients against the execution of untrusted code
is extremely important even if DPoP is used. Besides secure coding
practices, Content Security Policy [W3C.CSP] can be used as a second
layer of defense against cross-site scripting.
8.3. Signed JWT Swapping
Servers accepting signed DPoP proof JWTs MUST check the "typ" field Servers accepting signed DPoP proof JWTs MUST check the "typ" field
in the headers of the JWTs to ensure that adversaries cannot use JWTs in the headers of the JWTs to ensure that adversaries cannot use JWTs
created for other purposes. created for other purposes.
8.3. Signature Algorithms 8.4. Signature Algorithms
Implementers MUST ensure that only asymmetric digital signature Implementers MUST ensure that only asymmetric digital signature
algorithms that are deemed secure can be used for signing DPoP algorithms that are deemed secure can be used for signing DPoP
proofs. In particular, the algorithm "none" MUST NOT be allowed. proofs. In particular, the algorithm "none" MUST NOT be allowed.
8.4. Message Integrity 8.5. Message Integrity
DPoP does not ensure the integrity of the payload or headers of DPoP does not ensure the integrity of the payload or headers of
requests. The DPoP proof only contains claims for the HTTP URI and requests. The DPoP proof only contains claims for the HTTP URI and
method, but not, for example, the message body or general request method, but not, for example, the message body or general request
headers. headers.
This is an intentional design decision intended to keep DPoP simple This is an intentional design decision intended to keep DPoP simple
to use, but as described, makes DPoP potentially susceptible to to use, but as described, makes DPoP potentially susceptible to
replay attacks where an attacker is able to modify message contents replay attacks where an attacker is able to modify message contents
and headers. In many setups, the message integrity and and headers. In many setups, the message integrity and
skipping to change at page 20, line 28 skipping to change at page 22, line 5
Implementers that have stronger requirements on the integrity of Implementers that have stronger requirements on the integrity of
messages are encouraged to either use TLS-based mechanisms or signed messages are encouraged to either use TLS-based mechanisms or signed
requests. TLS-based mechanisms are in particular OAuth Mutual TLS requests. TLS-based mechanisms are in particular OAuth Mutual TLS
[RFC8705] and OAuth Token Binding [I-D.ietf-oauth-token-binding]. [RFC8705] and OAuth Token Binding [I-D.ietf-oauth-token-binding].
Note: While signatures covering other parts of requests are out of Note: While signatures covering other parts of requests are out of
the scope of this specification, additional information to be signed the scope of this specification, additional information to be signed
can be added into DPoP proofs. can be added into DPoP proofs.
8.5. Public Key Binding 8.6. Access Token and Public Key Binding
The binding between the DPoP public key and the access token, which The binding of the access token to the DPoP public key, which is
is specified in Section 6, uses a cryptographic hash of the JWK specified in Section 6, uses a cryptographic hash of the JWK
representation of the public key. It relies on the hash function representation of the public key. It relies on the hash function
having sufficient second-preimage resistance so as to make it having sufficient second-preimage resistance so as to make it
computationally infeasible to find or create another key that computationally infeasible to find or create another key that
produces to the same hash output value. The SHA-256 hash function produces to the same hash output value. The SHA-256 hash function
was used because it meets the aforementioned requirement while being was used because it meets the aforementioned requirement while being
widely available. If, in the future, JWK thumbprints need to be widely available. If, in the future, JWK thumbprints need to be
computed using hash function(s) other than SHA-256, it is suggested computed using hash function(s) other than SHA-256, it is suggested
that, for additional related JWT confirmation methods, members be that an additional related JWT confirmation method member be defined
defined for that purpose and registered in the IANA "JWT Confirmation for that purpose, registered in the respective IANA registry, and
Methods" registry [IANA.JWT.Claims] for JWT "cnf" member values. used in place of the "jkt" confirmation method defined herein.
Similarly, the binding of the DPoP proof to the access token uses a
hash of that access token as the value of the "ath" claim in the DPoP
proof (see Section 4.2). This relies on the value of the hash being
sufficiently unique so as to reliably identify the access token. The
collision resistance of SHA-256 meets that requirement. If, in the
future, access token digests need be computed using hash function(s)
other than SHA-256, it is suggested that an additional related JWT
claim be defined for that purpose, registered in the respective IANA
registry, and used in place of the "ath" claim defined herein.
9. IANA Considerations 9. IANA Considerations
9.1. OAuth Access Token Type Registration 9.1. OAuth Access Token Type Registration
This specification requests registration of the following access This specification requests registration of the following access
token type in the "OAuth Access Token Types" registry token type in the "OAuth Access Token Types" registry
[IANA.OAuth.Params] established by [RFC6749]. [IANA.OAuth.Params] established by [RFC6749].
* Type name: "DPoP" * Type name: "DPoP"
skipping to change at page 22, line 32 skipping to change at page 24, line 17
* Claim Name: "htu" * Claim Name: "htu"
* Claim Description: The HTTP URI of the request (without query and * Claim Description: The HTTP URI of the request (without query and
fragment parts) fragment parts)
* Change Controller: IESG * Change Controller: IESG
* Specification Document(s): [[ Section 4.2 of this specification ]] * Specification Document(s): [[ Section 4.2 of this specification ]]
Access token hash:
* Claim Name: "ath"
* Claim Description: The base64url encoded SHA-256 hash of the ASCII
encoding of the associated access token's value
* Change Controller: IESG
* Specification Document(s): [[ Section 4.2 of this specification ]]
9.6. HTTP Message Header Field Names Registration 9.6. HTTP Message Header Field Names Registration
This document specifies the following new HTTP header fields, This document specifies the following new HTTP header fields,
registration of which is requested in the "Permanent Message Header registration of which is requested in the "Permanent Message Header
Field Names" registry [IANA.Headers] defined in [RFC3864]. Field Names" registry [IANA.Headers] defined in [RFC3864].
* Header Field Name: "DPoP" * Header Field Name: "DPoP"
* Applicable protocol: HTTP * Applicable protocol: HTTP
skipping to change at page 23, line 6 skipping to change at page 25, line 4
* Specification Document(s): [[ this specification ]] * Specification Document(s): [[ this specification ]]
9.7. Authorization Server Metadata Registration 9.7. Authorization Server Metadata Registration
This specification requests registration of the following values in This specification requests registration of the following values in
the IANA "OAuth Authorization Server Metadata" registry the IANA "OAuth Authorization Server Metadata" registry
[IANA.OAuth.Parameters] established by [RFC8414]. [IANA.OAuth.Parameters] established by [RFC8414].
* Metadata Name: "dpop_signing_alg_values_supported" * Metadata Name: "dpop_signing_alg_values_supported"
* Metadata Description: JSON array containing a list of the JWS * Metadata Description: JSON array containing a list of the JWS
algorithms supported for DPoP proof JWTs algorithms supported for DPoP proof JWTs
* Change Controller: IESG * Change Controller: IESG
* Specification Document(s): [[ Section 5.1 of this specification ]] * Specification Document(s): [[ Section 5.1 of this specification ]]
10. Normative References 10. Normative References
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May RFC 6749, DOI 10.17487/RFC6749, October 2012,
2015, <https://www.rfc-editor.org/info/rfc7515>. <https://www.rfc-editor.org/info/rfc6749>.
[RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
<https://www.rfc-editor.org/info/rfc7518>.
[RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
2015, <https://www.rfc-editor.org/info/rfc7638>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008, DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>. <https://www.rfc-editor.org/info/rfc5234>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
RFC 6749, DOI 10.17487/RFC6749, October 2012, Resource Identifier (URI): Generic Syntax", STD 66,
<https://www.rfc-editor.org/info/rfc6749>. RFC 3986, DOI 10.17487/RFC3986, January 2005,
<https://www.rfc-editor.org/info/rfc3986>.
[RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web
Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May
2015, <https://www.rfc-editor.org/info/rfc7515>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231, Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, DOI 10.17487/RFC7231, June 2014,
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK)
Resource Identifier (URI): Generic Syntax", STD 66, Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September
RFC 3986, DOI 10.17487/RFC3986, January 2005, 2015, <https://www.rfc-editor.org/info/rfc7638>.
<https://www.rfc-editor.org/info/rfc3986>.
[RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of- [RFC7800] Jones, M., Bradley, J., and H. Tschofenig, "Proof-of-
Possession Key Semantics for JSON Web Tokens (JWTs)", Possession Key Semantics for JSON Web Tokens (JWTs)",
RFC 7800, DOI 10.17487/RFC7800, April 2016, RFC 7800, DOI 10.17487/RFC7800, April 2016,
<https://www.rfc-editor.org/info/rfc7800>. <https://www.rfc-editor.org/info/rfc7800>.
11. Informative References [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518,
DOI 10.17487/RFC7518, May 2015,
[I-D.ietf-oauth-security-topics] <https://www.rfc-editor.org/info/rfc7518>.
Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
"OAuth 2.0 Security Best Current Practice", Work in
Progress, Internet-Draft, draft-ietf-oauth-security-
topics-16, 5 October 2020, <https://tools.ietf.org/html/
draft-ietf-oauth-security-topics-16>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[IANA.OAuth.Params]
IANA, "OAuth Parameters",
<https://www.iana.org/assignments/oauth-parameters>.
[RFC8725] Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/info/rfc8725>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/info/rfc8414>.
[I-D.ietf-oauth-access-token-jwt]
Bertocci, V., "JSON Web Token (JWT) Profile for OAuth 2.0
Access Tokens", Work in Progress, Internet-Draft, draft-
ietf-oauth-access-token-jwt-10, 23 September 2020,
<https://tools.ietf.org/html/draft-ietf-oauth-access-
token-jwt-10>.
[IANA.Headers]
IANA, "Message Headers",
<https://www.iana.org/assignments/message-headers>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token 11. Informative References
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8707] Campbell, B., Bradley, J., and H. Tschofenig, "Resource
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, Indicators for OAuth 2.0", RFC 8707, DOI 10.17487/RFC8707,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. February 2020, <https://www.rfc-editor.org/info/rfc8707>.
[W3C.WebCryptoAPI] [W3C.WebCryptoAPI]
Watson, M., "Web Cryptography API", 26 January 2017, Watson, M., "Web Cryptography API", 26 January 2017,
<https://www.w3.org/TR/2017/REC-WebCryptoAPI-20170126>. <https://www.w3.org/TR/2017/REC-WebCryptoAPI-20170126>.
[RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing", Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014, RFC 7230, DOI 10.17487/RFC7230, June 2014,
<https://www.rfc-editor.org/info/rfc7230>. <https://www.rfc-editor.org/info/rfc7230>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally [W3C.CSP] West, M., "Content Security Policy Level 3", 15 October
Unique IDentifier (UUID) URN Namespace", RFC 4122, 2018, <https://www.w3.org/TR/2018/WD-CSP3-20181015/>.
DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>. [IANA.HTTP.AuthSchemes]
IANA, "Hypertext Transfer Protocol (HTTP) Authentication
Scheme Registry",
<https://www.iana.org/assignments/http-authschemes>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864,
DOI 10.17487/RFC3864, September 2004,
<https://www.rfc-editor.org/info/rfc3864>.
[RFC8705] Campbell, B., Bradley, J., Sakimura, N., and T. [RFC8705] Campbell, B., Bradley, J., Sakimura, N., and T.
Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication Lodderstedt, "OAuth 2.0 Mutual-TLS Client Authentication
and Certificate-Bound Access Tokens", RFC 8705, and Certificate-Bound Access Tokens", RFC 8705,
DOI 10.17487/RFC8705, February 2020, DOI 10.17487/RFC8705, February 2020,
<https://www.rfc-editor.org/info/rfc8705>. <https://www.rfc-editor.org/info/rfc8705>.
[RFC8707] Campbell, B., Bradley, J., and H. Tschofenig, "Resource [RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Indicators for OAuth 2.0", RFC 8707, DOI 10.17487/RFC8707, Unique IDentifier (UUID) URN Namespace", RFC 4122,
February 2020, <https://www.rfc-editor.org/info/rfc8707>. DOI 10.17487/RFC4122, July 2005,
<https://www.rfc-editor.org/info/rfc4122>.
[RFC7523] Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token [IANA.MediaTypes]
(JWT) Profile for OAuth 2.0 Client Authentication and IANA, "Media Types",
Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May <https://www.iana.org/assignments/media-types>.
2015, <https://www.rfc-editor.org/info/rfc7523>.
[RFC8725] Sheffer, Y., Hardt, D., and M. Jones, "JSON Web Token Best
Current Practices", BCP 225, RFC 8725,
DOI 10.17487/RFC8725, February 2020,
<https://www.rfc-editor.org/info/rfc8725>.
[RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer [RFC7235] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Authentication", RFC 7235, Protocol (HTTP/1.1): Authentication", RFC 7235,
DOI 10.17487/RFC7235, June 2014, DOI 10.17487/RFC7235, June 2014,
<https://www.rfc-editor.org/info/rfc7235>. <https://www.rfc-editor.org/info/rfc7235>.
[IANA.JWT] IANA, "JSON Web Token Claims", [I-D.ietf-oauth-security-topics]
<http://www.iana.org/assignments/jwt>. Lodderstedt, T., Bradley, J., Labunets, A., and D. Fett,
"OAuth 2.0 Security Best Current Practice", Work in
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Progress, Internet-Draft, draft-ietf-oauth-security-
Requirement Levels", BCP 14, RFC 2119, topics-16, 5 October 2020, <https://tools.ietf.org/html/
DOI 10.17487/RFC2119, March 1997, draft-ietf-oauth-security-topics-16>.
<https://www.rfc-editor.org/info/rfc2119>.
[IANA.HTTP.AuthSchemes] [IANA.OAuth.Params]
IANA, "Hypertext Transfer Protocol (HTTP) Authentication IANA, "OAuth Parameters",
Scheme Registry", <https://www.iana.org/assignments/oauth-parameters>.
<https://www.iana.org/assignments/http-authschemes>.
[IANA.MediaType.StructuredSuffix] [IANA.MediaType.StructuredSuffix]
IANA, "Structured Syntax Suffix Registry", IANA, "Structured Syntax Suffix Registry",
<https://www.iana.org/assignments/media-type-structured- <https://www.iana.org/assignments/media-type-structured-
suffix>. suffix>.
[RFC8417] Hunt, P., Ed., Jones, M., Denniss, W., and M. Ansari,
"Security Event Token (SET)", RFC 8417,
DOI 10.17487/RFC8417, July 2018,
<https://www.rfc-editor.org/info/rfc8417>.
[I-D.ietf-oauth-token-binding]
Jones, M., Campbell, B., Bradley, J., and W. Denniss,
"OAuth 2.0 Token Binding", Work in Progress, Internet-
Draft, draft-ietf-oauth-token-binding-08, 19 October 2018,
<https://tools.ietf.org/html/draft-ietf-oauth-token-
binding-08>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization [RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750, Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012, DOI 10.17487/RFC6750, October 2012,
<https://www.rfc-editor.org/info/rfc6750>. <https://www.rfc-editor.org/info/rfc6750>.
[IANA.MediaTypes] [RFC8417] Hunt, P., Ed., Jones, M., Denniss, W., and M. Ansari,
IANA, "Media Types", "Security Event Token (SET)", RFC 8417,
<https://www.iana.org/assignments/media-types>. DOI 10.17487/RFC8417, July 2018,
<https://www.rfc-editor.org/info/rfc8417>.
[I-D.ietf-oauth-jwsreq] [I-D.ietf-oauth-jwsreq]
Sakimura, N., Bradley, J., and M. Jones, "The OAuth 2.0 Sakimura, N., Bradley, J., and M. Jones, "The OAuth 2.0
Authorization Framework: JWT Secured Authorization Request Authorization Framework: JWT Secured Authorization Request
(JAR)", Work in Progress, Internet-Draft, draft-ietf- (JAR)", Work in Progress, Internet-Draft, draft-ietf-
oauth-jwsreq-30, 10 September 2020, oauth-jwsreq-30, 10 September 2020,
<https://tools.ietf.org/html/draft-ietf-oauth-jwsreq-30>. <https://tools.ietf.org/html/draft-ietf-oauth-jwsreq-30>.
[IANA.JWT] IANA, "JSON Web Token Claims",
<http://www.iana.org/assignments/jwt>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC7523] Jones, M., Campbell, B., and C. Mortimore, "JSON Web Token
(JWT) Profile for OAuth 2.0 Client Authentication and
Authorization Grants", RFC 7523, DOI 10.17487/RFC7523, May
2015, <https://www.rfc-editor.org/info/rfc7523>.
[RFC8414] Jones, M., Sakimura, N., and J. Bradley, "OAuth 2.0
Authorization Server Metadata", RFC 8414,
DOI 10.17487/RFC8414, June 2018,
<https://www.rfc-editor.org/info/rfc8414>.
[RFC7662] Richer, J., Ed., "OAuth 2.0 Token Introspection",
RFC 7662, DOI 10.17487/RFC7662, October 2015,
<https://www.rfc-editor.org/info/rfc7662>.
[I-D.ietf-oauth-access-token-jwt]
Bertocci, V., "JSON Web Token (JWT) Profile for OAuth 2.0
Access Tokens", Work in Progress, Internet-Draft, draft-
ietf-oauth-access-token-jwt-11, 22 January 2021,
<https://tools.ietf.org/html/draft-ietf-oauth-access-
token-jwt-11>.
[IANA.Headers]
IANA, "Message Headers",
<https://www.iana.org/assignments/message-headers>.
[RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token
(JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015,
<https://www.rfc-editor.org/info/rfc7519>.
[I-D.ietf-oauth-token-binding]
Jones, M., Campbell, B., Bradley, J., and W. Denniss,
"OAuth 2.0 Token Binding", Work in Progress, Internet-
Draft, draft-ietf-oauth-token-binding-08, 19 October 2018,
<https://tools.ietf.org/html/draft-ietf-oauth-token-
binding-08>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
Appendix A. Acknowledgements Appendix A. Acknowledgements
We would like to thank Annabelle Backman, Dominick Baier, William We would like to thank Annabelle Backman, Dominick Baier, Andrii
Denniss, Vladimir Dzhuvinov, Mike Engan, Nikos Fotiou, Mark Haine, Deinega, William Denniss, Vladimir Dzhuvinov, Mike Engan, Nikos
Dick Hardt, Bjorn Hjelm, Jared Jennings, Steinar Noem, Neil Madden, Fotiou, Mark Haine, Dick Hardt, Bjorn Hjelm, Jared Jennings, Steinar
Rob Otto, Aaron Parecki, Michael Peck, Paul Querna, Justin Richer, Noem, Neil Madden, Rob Otto, Aaron Parecki, Michael Peck, Paul
Filip Skokan, Dave Tonge, Jim Willeke, and others (please let us Querna, Justin Richer, Filip Skokan, Dave Tonge, Jim Willeke,
know, if you've been mistakenly omitted) for their valuable input, Philippe De Ryck, and others (please let us know, if you've been
feedback and general support of this work. mistakenly omitted) for their valuable input, feedback and general
support of this work.
This document resulted from discussions at the 4th OAuth Security This document resulted from discussions at the 4th OAuth Security
Workshop in Stuttgart, Germany. We thank the organizers of this Workshop in Stuttgart, Germany. We thank the organizers of this
workshop (Ralf Kusters, Guido Schmitz). workshop (Ralf Kusters, Guido Schmitz).
Appendix B. Document History Appendix B. Document History
[[ To be removed from the final specification ]] [[ To be removed from the final specification ]]
-03
* Add an access token hash ("ath") claim to the DPoP proof when used
in conjunction with the presentation of an access token for
protected resource access
* add Untrusted Code in the Client Context section to security
considerations
* Editorial updates and fixes
-02 -02
* Lots of editorial updates and additions including expanding on the * Lots of editorial updates and additions including expanding on the
objectives, better defining the key confirmation representations, objectives, better defining the key confirmation representations,
example updates and additions, better describing mixed bearer/dpop example updates and additions, better describing mixed bearer/dpop
token type deployments, clarify RT binding only being done for token type deployments, clarify RT binding only being done for
public clients and why, more clearly allow for a bound RT but with public clients and why, more clearly allow for a bound RT but with
bearer AT, explain/justify the choice of SHA-256 for key binding, bearer AT, explain/justify the choice of SHA-256 for key binding,
and more and more
 End of changes. 64 change blocks. 
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