draft-ietf-tokbind-https-18.txt   rfc8473.txt 
Internet Engineering Task Force A. Popov Internet Engineering Task Force (IETF) A. Popov
Internet-Draft M. Nystroem Request for Comments: 8473 M. Nystroem
Intended status: Standards Track Microsoft Corp. Category: Standards Track Microsoft Corp.
Expires: December 28, 2018 D. Balfanz, Ed. ISSN: 2070-1721 D. Balfanz, Ed.
A. Langley
N. Harper N. Harper
Google Inc. Google Inc.
J. Hodges J. Hodges
PayPal Kings Mountain Systems
June 26, 2018 October 2018
Token Binding over HTTP Token Binding over HTTP
draft-ietf-tokbind-https-18
Abstract Abstract
This document describes a collection of mechanisms that allow HTTP This document describes a collection of mechanisms that allow HTTP
servers to cryptographically bind security tokens (such as cookies servers to cryptographically bind security tokens (such as cookies
and OAuth tokens) to TLS connections. and OAuth tokens) to TLS connections.
We describe both first-party and federated scenarios. In a first- We describe both first-party and federated scenarios. In a first-
party scenario, an HTTP server is able to cryptographically bind the party scenario, an HTTP server is able to cryptographically bind the
security tokens it issues to a client, and which the client security tokens that it issues to a client -- and that the client
subsequently returns to the server, to the TLS connection between the subsequently returns to the server -- to the TLS connection between
client and server. Such bound security tokens are protected from the client and the server. Such bound security tokens are protected
misuse since the server can generally detect if they are replayed from misuse, since the server can generally detect if they are
inappropriately, e.g., over other TLS connections. replayed inappropriately, e.g., over other TLS connections.
Federated token bindings, on the other hand, allow servers to Federated Token Bindings, on the other hand, allow servers to
cryptographically bind security tokens to a TLS connection that the cryptographically bind security tokens to a TLS connection that the
client has with a different server than the one issuing the token. client has with a different server than the one issuing the token.
This document is a companion document to The Token Binding Protocol. This document is a companion document to "The Token Binding Protocol
Version 1.0" (RFC 8471).
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on December 28, 2018. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8473.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 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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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The Sec-Token-Binding HTTP Request Header Field . . . . . . . 4 2. The Sec-Token-Binding HTTP Request Header Field . . . . . . . 4
2.1. HTTPS Token Binding Key Pair Scoping . . . . . . . . . . 5 2.1. HTTPS Token Binding Key-Pair Scoping . . . . . . . . . . 5
3. TLS Renegotiation . . . . . . . . . . . . . . . . . . . . . . 6 3. TLS Renegotiation . . . . . . . . . . . . . . . . . . . . . . 6
4. First-Party Use Cases . . . . . . . . . . . . . . . . . . . . 6 4. First-Party Use Cases . . . . . . . . . . . . . . . . . . . . 7
5. Federation Use Cases . . . . . . . . . . . . . . . . . . . . 7 5. Federation Use Cases . . . . . . . . . . . . . . . . . . . . 7
5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 7 5.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 8
5.3. HTTP Redirects . . . . . . . . . . . . . . . . . . . . . 10 5.3. HTTP Redirects . . . . . . . . . . . . . . . . . . . . . 10
5.4. Negotiated Key Parameters . . . . . . . . . . . . . . . . 12 5.4. Negotiated Key Parameters . . . . . . . . . . . . . . . . 12
5.5. Federation Example . . . . . . . . . . . . . . . . . . . 12 5.5. Federation Example . . . . . . . . . . . . . . . . . . . 13
6. Implementation Considerations . . . . . . . . . . . . . . . . 15 6. Implementation Considerations . . . . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15 7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7.1. Security Token Replay . . . . . . . . . . . . . . . . . . 15 7.1. Security Token Replay . . . . . . . . . . . . . . . . . . 16
7.2. Sensitivity of the Sec-Token-Binding Header . . . . . . . 15 7.2. Sensitivity of the Sec-Token-Binding Header . . . . . . . 16
7.3. Securing Federated Sign-On Protocols . . . . . . . . . . 17 7.3. Securing Federated Sign-On Protocols . . . . . . . . . . 17
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19 8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 20
8.1. Scoping of Token Binding Key Pairs . . . . . . . . . . . 19 8.1. Scoping of Token Binding Key Pairs . . . . . . . . . . . 20
8.2. Lifetime of Token Binding Key Pairs . . . . . . . . . . . 20 8.2. Lifetime of Token Binding Key Pairs . . . . . . . . . . . 20
8.3. Correlation . . . . . . . . . . . . . . . . . . . . . . . 20 8.3. Correlation . . . . . . . . . . . . . . . . . . . . . . . 21
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 10.1. Normative References . . . . . . . . . . . . . . . . . . 22
11.1. Normative References . . . . . . . . . . . . . . . . . . 21 10.2. Informative References . . . . . . . . . . . . . . . . . 23
11.2. Informative References . . . . . . . . . . . . . . . . . 23 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24
1. Introduction 1. Introduction
The Token Binding Protocol [I-D.ietf-tokbind-protocol] defines a The Token Binding protocol [RFC8471] defines a Token Binding ID for a
Token Binding ID for a TLS connection between a client and a server. TLS connection between a client and a server. The Token Binding ID
The Token Binding ID of a TLS connection is constructed using the of a TLS connection is constructed using the public key of a
public key of a private-public key pair. The client proves private-public key pair. The client proves possession of the
possession of the corresponding private key. This Token Binding key corresponding private key. This Token Binding key pair is
pair is long-lived. I.e., subsequent TLS connections between the long-lived. That is, subsequent TLS connections between the same
same client and server have the same Token Binding ID, unless client and server have the same Token Binding ID, unless specifically
specifically reset, e.g., by the user. When issuing a security token reset, e.g., by the user. When issuing a security token (e.g., an
(e.g., an HTTP cookie or an OAuth token [RFC6749]) to a client, the HTTP cookie or an OAuth token [RFC6749]) to a client, the server can
server can include the Token Binding ID in the token, thus include the Token Binding ID in the token, thus cryptographically
cryptographically binding the token to TLS connections between that binding the token to TLS connections between that particular client
particular client and server, and inoculating the token against abuse and server, and inoculating the token against abuse (reuse, attempted
(re-use, attempted impersonation, etc.) by attackers. impersonation, etc.) by attackers.
While the Token Binding Protocol [I-D.ietf-tokbind-protocol] defines While the Token Binding protocol [RFC8471] defines a message format
a message format for establishing a Token Binding ID, it does not for establishing a Token Binding ID, it does not specify how this
specify how this message is embedded in higher-level protocols. The message is embedded in higher-level protocols. The purpose of this
purpose of this specification is to define how TokenBindingMessages specification is to define how TokenBindingMessages are embedded in
are embedded in HTTP (both versions 1.1 [RFC7230] and 2 [RFC7540]). HTTP (both versions 1.1 [RFC7230] and 2 [RFC7540]). Note that
Note that TokenBindingMessages are only defined if the underlying TokenBindingMessages are only defined if the underlying transport
transport uses TLS. This means that Token Binding over HTTP is only uses TLS. This means that Token Binding over HTTP is only defined
defined when the HTTP protocol is layered on top of TLS (commonly when HTTP is layered on top of TLS (commonly referred to as HTTPS
referred to as HTTPS [RFC2818]). [RFC2818]).
HTTP clients establish a Token Binding ID with a server by including HTTP clients establish a Token Binding ID with a server by including
a special HTTP header field in HTTP requests. The HTTP header field a special HTTP header field in HTTP requests. The HTTP header field
value is a base64url-encoded TokenBindingMessage. value is a base64url-encoded TokenBindingMessage.
TokenBindingMessages allow clients to establish multiple Token A TokenBindingMessage allows a client to establish multiple Token
Binding IDs with the server, by including multiple TokenBinding Binding IDs with the server by including multiple TokenBinding
structures in the TokenBindingMessage. By default, a client will structures. By default, a client will establish a Provided Token
establish a provided Token Binding ID with the server, indicating a Binding ID with the server, indicating a Token Binding ID that the
Token Binding ID that the client will persistently use with the client will persistently use with the server. Under certain
server. Under certain conditions, the client can also include a conditions, the client can also include a Referred Token Binding ID
referred Token Binding ID in the TokenBindingMessage, indicating a in the TokenBindingMessage, indicating a Token Binding ID that the
Token Binding ID that the client is using with a different server client is using with a different server than the one that the
than the one that the TokenBindingMessage is sent to. This is useful TokenBindingMessage is sent to. This is useful in federation
in federation scenarios. scenarios.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP "OPTIONAL" in this document are to be interpreted as described in
14 [RFC2119] [RFC8174] when, and only when, they appear in all BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. capitals, as shown here.
2. The Sec-Token-Binding HTTP Request Header Field 2. The Sec-Token-Binding HTTP Request Header Field
Once a client and server have negotiated the Token Binding Protocol Once a client and server have negotiated the Token Binding protocol
with HTTP/1.1 or HTTP/2 (see [I-D.ietf-tokbind-protocol] and with HTTP/1.1 or HTTP/2 (see [RFC8471] and [RFC8472]), clients MUST
[I-D.ietf-tokbind-negotiation]), clients MUST include a Sec-Token- include a Sec-Token-Binding header field in their HTTP requests and
Binding header field in their HTTP requests, and MUST include only MUST include only one such header field per HTTP request. Also, the
one such header field per HTTP request. Also, The Sec-Token-Binding Sec-Token-Binding header field MUST NOT be included in HTTP
header field MUST NOT be included in HTTP responses. The ABNF of the responses. The ABNF of the Sec-Token-Binding header field is (per
Sec-Token-Binding header field is (in [RFC7230] style, see also the style of [RFC7230]; see also Section 8.3 of [RFC7231]):
Section 8.3 of [RFC7231]):
Sec-Token-Binding = EncodedTokenBindingMessage Sec-Token-Binding = EncodedTokenBindingMessage
The header field name is Sec-Token-Binding and its single value, The header field name is Sec-Token-Binding, and its single value,
EncodedTokenBindingMessage, is a base64url encoding of a single EncodedTokenBindingMessage, is a base64url encoding of a single
TokenBindingMessage, as defined in [I-D.ietf-tokbind-protocol]. The TokenBindingMessage, as defined in [RFC8471]. The base64url encoding
base64url encoding uses the URL- and filename-safe character set uses the URL and filename safe character set described in Section 5
described in Section 5 of [RFC4648], with all trailing padding of [RFC4648], with all trailing padding characters (i.e., "=")
characters '=' omitted and without the inclusion of any line breaks, omitted and without the inclusion of any line breaks, whitespace, or
whitespace, or other additional characters. other additional characters.
For example: For example:
Sec-Token-Binding: AIkAAgBBQFzK4_bhAqLDwRQxqJWte33d7hZ0hZWHwk-miKPg4E\ Sec-Token-Binding: AIkAAgBBQFzK4_bhAqLDwRQxqJWte33d7hZ0hZWHwk-miKPg4E\
9fcgs7gBPoz-9RfuDfN9WCw6keHEw1ZPQMGs9CxpuHm-YAQM_j\ 9fcgs7gBPoz-9RfuDfN9WCw6keHEw1ZPQMGs9CxpuHm-YAQM_j\
aOwwej6a-cQBGU7CJpUHOvXG4VvjNq8jDsvta9Y8_bPEPj25Gg\ aOwwej6a-cQBGU7CJpUHOvXG4VvjNq8jDsvta9Y8_bPEPj25Gg\
mKiPjhJEtZA6mJ_9SNifLvVBTi7fR9wSAAAA mKiPjhJEtZA6mJ_9SNifLvVBTi7fR9wSAAAA
(Note that the backslashes and line breaks are provided to ease (Note that the backslashes and line breaks are provided to ease
readability, they are not part of the actual encoded message.) readability; they are not part of the actual encoded message.)
If the server receives more than one Sec-Token-Binding header field If the server receives more than one Sec-Token-Binding header field
in an HTTP request, then the server MUST reject the message with a in an HTTP request, then the server MUST reject the message with a
400 (Bad Request) HTTP status code. Additionally, the Sec-Token- 400 (Bad Request) HTTP status code. Additionally, the
Binding header field: Sec-Token-Binding header field:
SHOULD NOT be stored by origin servers on PUT requests, o SHOULD NOT be stored by origin servers on PUT requests,
MAY be listed by a server in a Vary response header field, and, o MAY be listed by a server in a Vary response header field, and
MUST NOT be used in HTTP trailers. o MUST NOT be used in HTTP trailers.
The TokenBindingMessage MUST contain exactly one TokenBinding The TokenBindingMessage MUST contain exactly one TokenBinding
structure with TokenBindingType of provided_token_binding, which MUST structure with a TokenBindingType value of provided_token_binding,
be signed with the Token Binding private key used by the client for which MUST be signed with the Token Binding private key used by the
connections between itself and the server that the HTTP request is client for connections between itself and the server that the HTTP
sent to (clients use different Token Binding key pairs for different request is sent to (clients use different Token Binding key pairs for
servers, see Section 2.1 below). The Token Binding ID established by different servers; see Section 2.1 below). The Token Binding ID
this TokenBinding is called a Provided Token Binding ID. established by this TokenBinding is called a "Provided Token
Binding ID".
The TokenBindingMessage MAY also contain exactly one TokenBinding The TokenBindingMessage MAY also contain exactly one TokenBinding
structure with TokenBindingType of referred_token_binding, as structure with a TokenBindingType value of referred_token_binding, as
specified in Section 5.3. In addition to the latter, or rather than specified in Section 5.3. In addition to the latter, or rather than
the latter, the TokenBindingMessage MAY contain other TokenBinding the latter, the TokenBindingMessage MAY contain other TokenBinding
structures. This is use case-specific, and such use cases are structures. This is specific to the use case in question; such use
outside the scope of this specification. cases are outside the scope of this specification.
A TokenBindingMessage is validated by the server as described in A TokenBindingMessage is validated by the server as described in
Section 4.2 ("Server Processing Rules") of Section 4.2 ("Server Processing Rules") of [RFC8471]. If validation
[I-D.ietf-tokbind-protocol]. If validation fails and a Token Binding fails and a Token Binding is rejected, any associated bound tokens
is rejected, any associated bound tokens MUST also be rejected by the MUST also be rejected by the server. HTTP requests containing
server. HTTP requests containing invalid tokens MUST be rejected. invalid tokens MUST be rejected. In this case, the server
In this case, the server application MAY return HTTP status code 400 application MAY return HTTP status code 400 (Bad Request) or proceed
(Bad Request) or proceed with an application-specific invalid token with an application-specific "invalid token" response (e.g.,
response (e.g., directing the client to re-authenticate and present a directing the client to re-authenticate and present a different
different token), or terminate the connection. token), or terminate the connection.
In HTTP/2, the client SHOULD use Header Compression [RFC7541] to In HTTP/2, the client SHOULD use header compression [RFC7541] to
avoid the overhead of repeating the same header field in subsequent avoid the overhead of repeating the same header field in subsequent
HTTP requests. HTTP requests.
2.1. HTTPS Token Binding Key Pair Scoping 2.1. HTTPS Token Binding Key-Pair Scoping
HTTPS is used in conjunction with various application protocols and HTTPS is used in conjunction with various application protocols and
application contexts, in various ways. For example, general-purpose application contexts, in various ways. For example, general-purpose
Web browsing is one such HTTP-based application context. Within that web browsing is one such HTTP-based application context. Within that
context, HTTP cookies [RFC6265] are typically utilized for state context, HTTP cookies [RFC6265] are typically utilized for state
management, including client authentication. A related, though management, including client authentication. A related, though
distinct, example of other HTTP-based application contexts is where distinct, example of other HTTP-based application contexts is where
OAuth tokens [RFC6749] are utilized to manage authorization for OAuth tokens [RFC6749] are utilized to manage authorization for
third-party application access to resources. The token scoping rules third-party application access to resources. The token-scoping rules
of these two examples can differ: the scoping rules for cookies are of these two examples can differ: the scoping rules for cookies are
concisely specified in [RFC6265], whereas OAuth is a framework and concisely specified in [RFC6265], whereas OAuth is a framework and
defines various token types with various scopings, some of which are defines various token types with various scopings, some of which are
determined by the encompassing application. determined by the encompassing application.
The scoping of Token Binding key pairs generated by Web browsers for The scoping of Token Binding key pairs generated by web browsers for
the purpose of binding HTTP cookies MUST be no wider than the the purpose of binding HTTP cookies MUST be no wider than the
granularity of a "registered domain" (also known as "effective top- granularity of a "registered domain" (also known as "effective
level domain + 1", or "eTLD+1"). An origin's "registered domain" is top-level domain + 1", or "eTLD+1"). An origin's "registered domain"
the origin's host's public suffix plus the label to its left, with is the origin's host's public suffix plus the label to its left
the term "public suffix" being defined in a note in Section 5.3 of (where the term "public suffix" is defined in the "NOTE:" paragraph
[RFC6265] as "a domain that is controlled by a public registry". For in Section 5.3 of [RFC6265] as "a domain that is controlled by a
example, for "https://www.example.com", the public suffix (eTLD) is public registry"). For example, for "https://www.example.com", the
"com", and the registered domain (eTLD+1) is "example.com". User public suffix (eTLD) is "com", and the registered domain (eTLD+1) is
agents SHOULD use an up-to-date public suffix list, such as the one "example.com". User Agents SHOULD use an up-to-date public suffix
maintained by Mozilla [PSL]. list, such as the one maintained by Mozilla [PSL].
This means that in practice the scope of a Token Binding key pair is This means that in practice the scope of a Token Binding key pair is
no larger than the scope of a cookie allowed by a Web browser. If a no larger than the scope of a cookie allowed by a web browser. If a
Web browser restricts cookies to a narrower scope than registered web browser restricts cookies to a narrower scope than registered
domains, the scope of Token Binding key pairs MAY also be more domains, the scope of Token Binding key pairs MAY also be narrower.
narrow. This applies to the use of Token Binding key pairs in first- This applies to the use of Token Binding key pairs in first-party use
party use cases, as well as in federation use cases defined in this cases, as well as in federation use cases defined in this
specification (Section 5). specification (Section 5).
Key pairs used to bind other application tokens, such as OAuth tokens Key pairs used to bind other application tokens, such as OAuth tokens
or OpenID Connect ID Tokens, SHOULD adhere to the above eTLD+1 or "OpenID Connect" ID Tokens [OpenID.Core], SHOULD adhere to the
scoping requirement for those tokens being employed in first-party or above eTLD+1 scoping requirement for those tokens being employed in
federation scenarios. Applications other than Web browsers MAY use first-party or federation scenarios. Applications other than web
different key pair scoping rules. See also Section 8.1, below. browsers MAY use different key-pair scoping rules. See also
Section 8.1 below.
Scoping rules for other HTTP-based application contexts are outside Scoping rules for other HTTP-based application contexts are outside
the scope of this specification. the scope of this specification.
3. TLS Renegotiation 3. TLS Renegotiation
Token Binding over HTTP/1.1 [RFC7230] can be performed in combination Token Binding over HTTP/1.1 [RFC7230] can be performed in combination
with TLS renegotiation. In this case, renegotiation MUST only occur with TLS renegotiation. In this case, renegotiation MUST only occur
between a client's HTTP request and the server's response, the client between a client's HTTP request and the server's response, the client
MUST NOT send any pipelined requests, and the client MUST NOT MUST NOT send any pipelined requests, and the client MUST NOT
initiate renegotiation. (I.e., the client may only send a initiate renegotiation. (That is, the client may only send a
renegotiation ClientHello in response to the server's HelloRequest.) renegotiation ClientHello in response to the server's HelloRequest.)
These conditions ensure that both the client and the server can These conditions ensure that both the client and the server can
clearly identify which TLS Exported Keying Material value [RFC5705] clearly identify which TLS Exported Keying Material value [RFC5705]
to use when generating or verifying the TokenBindingMessage. This to use when generating or verifying the TokenBindingMessage. This
also prevents a TokenBindingMessage from being split across TLS also prevents a TokenBindingMessage from being split across TLS
renegotiation boundaries. (I.e., due to TLS message fragmentation - renegotiation boundaries due to TLS message fragmentation; see
see Section 6.2.1 of [RFC5246].) Section 6.2.1 of [RFC5246].
(Note: This document deals with TLS 1.2 and therefore refers to
RFC 5246 (which has been obsoleted by RFC 8446); [TOKENBIND-TLS13]
addresses Token Binding in TLS 1.3.)
4. First-Party Use Cases 4. First-Party Use Cases
In a first-party use case (also known as a "same-site" use case), an In a first-party use case (also known as a "same-site" use case), an
HTTP server issues a security token such as a cookie (or similar) to HTTP server issues a security token such as a cookie (or similar) to
a client, and expects the client to return the security token at a a client and expects the client to return the security token at a
later time, e.g., in order to authenticate. Binding the security later time, e.g., in order to authenticate. Binding the security
token to the TLS connection between client and server protects the token to the TLS connection between the client and the server
security token from misuse, since the server can detect if the protects the security token from misuse, since the server can detect
security token is replayed inappropriately, e.g., over other TLS if the security token is replayed inappropriately, e.g., over other
connections. TLS connections.
See Section 5 of [I-D.ietf-tokbind-protocol] for general guidance See Section 5 of [RFC8471] for general guidance regarding the binding
regarding binding of security tokens and their subsequent validation. of security tokens and their subsequent validation.
5. Federation Use Cases 5. Federation Use Cases
5.1. Introduction 5.1. Introduction
For privacy reasons, clients use different Token Binding key pairs to For privacy reasons, clients use different Token Binding key pairs to
establish Provided Token Binding IDs with different servers. As a establish Provided Token Binding IDs with different servers. As a
result, a server cannot bind a security token (such as an OAuth token result, a server cannot bind a security token (such as an OAuth token
or an OpenID Connect ID Token [OpenID.Core]) to a TLS connection that or an OpenID Connect ID Token [OpenID.Core]) to a TLS connection that
the client has with a different server. This is, however, a common the client has with a different server. This is, however, a common
requirement in federation scenarios: For example, an Identity requirement in federation scenarios: for example, an Identity
Provider may wish to issue an identity token to a client and Provider may wish to issue an identity token to a client and
cryptographically bind that token to the TLS connection between the cryptographically bind that token to the TLS connection between the
client and a Relying Party. client and a Relying Party.
In this section, we describe mechanisms to achieve this. The common In this section, we describe mechanisms to achieve this. The common
idea among these mechanisms is that a server (called the Token idea among these mechanisms is that a server (called the "Token
Consumer in this document) signals to the client that it should Consumer" in this document) signals to the client that it should
reveal the Provided Token Binding ID that is used between the client reveal the Provided Token Binding ID that is used between the client
and itself to another server (called the Token Provider in this and itself to another server (called the "Token Provider" in this
document). Also common across the mechanisms is how the Token document). Also common across the mechanisms is how the Token
Binding ID is revealed to the Token Provider: The client uses the Binding ID is revealed to the Token Provider: the client uses the
Token Binding Protocol [I-D.ietf-tokbind-protocol], and includes a Token Binding protocol [RFC8471] and includes a TokenBinding
TokenBinding structure in the Sec-Token-Binding HTTP header field structure in the Sec-Token-Binding HTTP header field defined above.
defined above. What differs between the various mechanisms is how What differs between the various mechanisms is how the Token Consumer
the Token Consumer signals to the client that it should reveal the signals to the client that it should reveal the Token Binding ID to
Token Binding ID to the Token Provider. Below, we specify one such the Token Provider. Below, we specify one such mechanism, which is
mechanism, which is suitable for redirect-based interactions between suitable for redirect-based interactions between Token Consumers and
Token Consumers and Token Providers. Token Providers.
Client Token Consumer Token Provider Client Token Consumer Token Provider
+--------+ +----+ +-----+ +--------+ +----+ +-----+
| Client | | TC | | TP | | Client | | TC | | TP |
+--------+ +----+ +-----+ +--------+ +----+ +-----+
| | | | | |
| | | | | |
| | | | | |
| Client interacts w/TC | | | Client interacts w/TC | |
| using TokenBindingID TBID1: | | | using TokenBindingID TBID1: | |
| TBMSG[[provided_token_binding,| | | TBMSG[[provided_token_binding,| |
| TBID1, signature]] | | | TBID1, signature]] | |
|------------------------------>| | |------------------------------>| |
| | | | | |
| Client interacts w/TP | | Client interacts w/TP |
| using TokenBindingID TBID2: | | using TokenBindingID TBID2: |
| TBMSG[[provided_token_binding, | | TBMSG[[provided_token_binding, |
| TBID2, signature]] | | TBID2, signature]] |
|----------------------------------------------------->| |----------------------------------------------------->|
| | | |
| | | | | |
| TC signals permission to | | | TC signals permission to | |
| reveal TBID1 to TP | | | reveal TBID1 to TP | |
|<------------------------------| | |<------------------------------| |
| | | | | |
| | | |
| Client interacts w/TP | | Client interacts w/TP |
| using TokenBindingID TBID1 and TBID2: | | using TokenBindingID TBID1 and TBID2: |
| TBMSG[[provided_token_binding, | | TBMSG[[provided_token_binding, |
| TBID2, signature], | | TBID2, signature], |
| [referred_token_binding, | | [referred_token_binding, |
| TBID1, signature]] | | TBID1, signature]] |
|----------------------------------------------------->| |----------------------------------------------------->|
| | | |
| | | | | |
| | | | | |
5.2. Overview 5.2. Overview
In a Federated Sign-On protocol, an Identity Provider issues an In a federated sign-on protocol, an Identity Provider issues an
identity token to a client, which sends the identity token to a identity token to a client, which sends the identity token to a
Relying Party to authenticate itself. Examples of this include Relying Party to authenticate itself. Examples of this include
OpenID Connect (in which the identity token is called an "ID Token") OpenID Connect (in which the identity token is called an "ID Token")
and SAML [OASIS.saml-core-2.0-os] (in which the identity token is a and the Security Assertion Markup Language (SAML)
SAML assertion). [OASIS.saml-core-2.0-os] (in which the identity token is a SAML
assertion).
To better protect the security of the identity token, the Identity To better protect the security of the identity token, the Identity
Provider may wish to bind the identity token to the TLS connection Provider may wish to bind the identity token to the TLS connection
between the client and the Relying Party, thus ensuring that only between the client and the Relying Party, thus ensuring that only
said client can use the identity token. The Relying Party will said client can use the identity token. The Relying Party will
compare the Token Binding ID (or a cryptographic hash of it) in the compare the Token Binding ID (or a cryptographic hash of it) in the
identity token with the Token Binding ID (or a hash thereof) of the identity token with the Token Binding ID (or a hash thereof) of the
TLS connection between this Relying Party and the client. TLS connection between this Relying Party and the client.
This is an example of a federation scenario, which more generally can This is an example of a federation scenario, which more generally can
skipping to change at page 9, line 22 skipping to change at page 9, line 26
o A Token Consumer causes the client to issue a token request to the o A Token Consumer causes the client to issue a token request to the
Token Provider. The goal is for the client to obtain a token and Token Provider. The goal is for the client to obtain a token and
then use it with the Token Consumer. then use it with the Token Consumer.
o The client delivers the token request to the Token Provider. o The client delivers the token request to the Token Provider.
o The Token Provider issues the token. The token is issued for the o The Token Provider issues the token. The token is issued for the
specific Token Consumer who requested it (thus preventing specific Token Consumer who requested it (thus preventing
malicious Token Consumers from using tokens with other Token malicious Token Consumers from using tokens with other Token
Consumers). The token is, however, typically a bearer token, Consumers). The token is, however, typically a bearer token,
meaning that any client can use it with the Token Consumer, not meaning that any client can use it with the Token Consumer -- not
just the client to which it was issued. just the client to which it was issued.
o Therefore, in the previous step, the Token Provider may want to o Therefore, in the previous step, the Token Provider may want to
include in the token the Token Binding ID (or a cryptographic hash include in the token the Token Binding ID (or a cryptographic hash
of it) that the client uses when communicating with the Token of it) that the client uses when communicating with the Token
Consumer, thus binding the token to the client's Token Binding key Consumer, thus binding the token to the client's Token Binding key
pair. The client proves possession of the private key when pair. The client proves possession of the private key when
communicating with the Token Consumer through the Token Binding communicating with the Token Consumer through the Token Binding
Protocol [I-D.ietf-tokbind-protocol], and uses the corresponding protocol [RFC8471] and uses the corresponding public key of this
public key of this key pair as a component of the Token Binding key pair as a component of the Token Binding ID. Comparing the
ID. Comparing the Token Binding ID from the token to the Token Token Binding ID from the token to the Token Binding ID
Binding ID established with the client allows the Token Consumer established with the client allows the Token Consumer to verify
to verify that the token was sent to it by the legitimate client. that the token was sent to it by the legitimate client.
o To allow the Token Provider to include the Token Binding ID in the o To allow the Token Provider to include the Token Binding ID in the
token, the Token Binding ID between client and Token Consumer must token, the Token Binding ID between the client and the Token
therefore be communicated to the Token Provider along with the Consumer must therefore be communicated to the Token Provider
token request. Communicating a Token Binding ID involves proving along with the token request. Communicating a Token Binding ID
possession of a private key and is described in the Token Binding involves proving possession of a private key and is described in
Protocol [I-D.ietf-tokbind-protocol]. the Token Binding protocol [RFC8471].
The client will perform this last operation only if the Token The client will perform this last operation only if the Token
Consumer requests the client to do so. Consumer requests the client to do so.
Below, we specify how Token Consumers can signal this request in Below, we specify how Token Consumers can signal this request in
redirect-based federation protocols. Note that this assumes that the redirect-based federation protocols. Note that this assumes that the
federated sign-on flow starts at the Token Consumer, or at the very federated sign-on flow starts at the Token Consumer or, at the very
least, includes a redirect from the Token Consumer to the Token least, includes a redirect from the Token Consumer to the Token
Provider. It is outside the scope of this document to specify Provider. It is outside the scope of this document to specify
similar mechanisms for flows that do not include such redirects. similar mechanisms for flows that do not include such redirects.
5.3. HTTP Redirects 5.3. HTTP Redirects
When a Token Consumer redirects the client to a Token Provider as a When a Token Consumer redirects the client to a Token Provider as a
means to deliver the token request, it SHOULD include an Include- means to deliver the token request, it SHOULD include an
Referred-Token-Binding-ID HTTP response header field in its HTTP Include-Referred-Token-Binding-ID HTTP response header field in its
response. The ABNF of the Include-Referred-Token-Binding-ID header HTTP response. The ABNF of the Include-Referred-Token-Binding-ID
is (in [RFC7230] style, see also Section 8.3 of [RFC7231]): header is (per the style of [RFC7230]; see also Section 8.3 of
[RFC7231]):
Include-Referred-Token-Binding-ID = "true" Include-Referred-Token-Binding-ID = "true"
Where the header field name is "Include-Referred-Token-Binding-ID", Where the header field name is "Include-Referred-Token-Binding-ID"
and the field-value of "true" is case-insensitive. For example: and the field value of "true" is case insensitive. For example:
Include-Referred-Token-Binding-ID: true Include-Referred-Token-Binding-ID: true
Including this response header field signals to the client that it Including this response header field signals to the client that it
should reveal, to the Token Provider, the Token Binding ID used should reveal, to the Token Provider, the Token Binding ID used
between itself and the Token Consumer. In the absence of this between itself and the Token Consumer. In the absence of this
response header field, the client will not disclose any information response header field, the client will not disclose any information
about the Token Binding used between the client and the Token about the Token Binding used between the client and the Token
Consumer to the Token Provider. Consumer to the Token Provider.
As illustrated in Section 5.5, when a client receives this header As illustrated in Section 5.5, when a client receives this header
field, it should take the TokenBindingID of the provided TokenBinding field, it should take the TokenBindingID [RFC8471] of the provided
from the referrer and create a referred TokenBinding with it to TokenBinding from the referrer and create a referred TokenBinding
include in the TokenBindingMessage on the redirect request. In other with it to include in the TokenBindingMessage in the redirect
words, the Token Binding message in the redirect request to the Token request. In other words, the Token Binding message in the redirect
Provider now includes one provided binding and one referred binding, request to the Token Provider now includes one provided binding and
the latter constructed from the binding between the client and the one referred binding, the latter constructed from the binding between
Token Consumer. the client and the Token Consumer.
When a client receives the Include-Referred-Token-Binding-ID header, When a client receives the Include-Referred-Token-Binding-ID header,
it includes the referred token binding even if both the Token it includes the referred Token Binding even if both the Token
Provider and the Token Consumer fall under the same eTLD+1 and the Provider and the Token Consumer fall under the same eTLD+1 and the
provided and referred token binding IDs are the same. provided and Referred Token Binding IDs are the same.
The referred token binding is sent only on the initial request The referred Token Binding is sent only in the initial request
resulting from the HTTP response that included the Include-Referred- resulting from the HTTP response that included the
Token-Binding-ID header. Should the response to that initial request Include-Referred-Token-Binding-ID header. Should the response to
be a further redirect, the original referred token binding is no that initial request be a further redirect, the original referred
longer included in subsequent requests. (A new referred token Token Binding is no longer included in subsequent requests. (A new
binding may be included if the redirecting endpoint itself responded referred Token Binding may be included if the redirecting endpoint
with a Include-Referred-Token-Binding-ID response header.) itself responded with an Include-Referred-Token-Binding-ID response
If the Include-Referred-Token-Binding-ID header field is received in header.)
response to a request that did not include the Token-Binding header
field, the client MUST ignore the Include-Referred-Token-Binding-ID
header field.
This header field has only meaning if the HTTP status code is a If the Include-Referred-Token-Binding-ID header field is
redirection code (300-399), and MUST be ignored by the client for any received in response to a request that did not include the
other status codes. If the client supports the Token Binding Sec-Token-Binding header field, the client MUST ignore the
Protocol, and has negotiated the Token Binding Protocol with both the Include-Referred-Token-Binding-ID header field.
Token Consumer and the Token Provider, it already sends the Sec-
Token-Binding header field to the Token Provider with each HTTP This header field only has meaning if the HTTP status code is a
request (as described in Section 2 above). redirection code (300-399) and MUST be ignored by the client for any
other status codes. As described in Section 2, if the client
supports the Token Binding protocol and has negotiated the Token
Binding protocol with both the Token Consumer and the Token Provider,
it sends the Sec-Token-Binding header field to the Token Provider
with each HTTP request.
The TokenBindingMessage included in the redirect request to the Token The TokenBindingMessage included in the redirect request to the Token
Provider SHOULD contain a TokenBinding with TokenBindingType Provider SHOULD contain a TokenBinding with a TokenBindingType value
referred_token_binding. If included, this TokenBinding MUST be of referred_token_binding. If included, this TokenBinding MUST be
signed with the Token Binding private key used by the client for signed with the Token Binding private key used by the client for
connections between itself and the Token Consumer (more specifically, connections between itself and the Token Consumer (more specifically,
the server that issued the Include-Referred-Token-Binding-ID response the server that issued the Include-Referred-Token-Binding-ID response
header field). The Token Binding ID established by this TokenBinding header field). The Token Binding ID established by this TokenBinding
is called a Referred Token Binding ID. is called a "Referred Token Binding ID".
As described above, the TokenBindingMessage MUST additionally contain As described above, the TokenBindingMessage MUST additionally contain
a Provided Token Binding ID, i.e., a TokenBinding structure with a Provided Token Binding ID, i.e., a TokenBinding structure with a
TokenBindingType of provided_token_binding, which MUST be signed with TokenBindingType value of provided_token_binding, which MUST be
the Token Binding private key used by the client for connections signed with the Token Binding private key used by the client for
between itself and the Token Provider (more specifically, the server connections between itself and the Token Provider (more specifically,
that the token request is being sent to). the server that the token request is being sent to).
If, for some deployment-specific reason, the initial Token Provider If, for some deployment-specific reason, the initial Token Provider
("TP1") needs to redirect the client to another Token Provider ("TP1") needs to redirect the client to another Token Provider
("TP2"), rather than directly back to the Token Consumer, it can be ("TP2") rather than directly back to the Token Consumer, it can be
accommodated using the header fields defined in this specification in accommodated using the header fields defined in this specification in
the following fashion ("the redirect-chain approach"): the following fashion ("the redirect-chain approach"):
Initially, the client is redirected to TP1 by the Token Consumer Initially, the client is redirected to TP1 by the Token Consumer
("TC"), as described above. Upon receiving the client's request, ("TC"), as described above. Upon receiving a client's request
containing a TokenBindingMessage which contains both provided and that contains a TokenBindingMessage that in turn contains both
referred TokenBindings (for TP1 and TC, respectively), TP1 provided and referred TokenBindings (for TP1 and TC,
responds to the client with a redirect response containing the respectively), TP1 responds to the client with a redirect response
Include-Referred-Token-Binding-ID header field and directing the that (1) contains the Include-Referred-Token-Binding-ID header
client to send a request to TP2. This causes the client to follow field and (2) directs the client to send a request to TP2. This
the same pattern and send a request containing a causes the client to follow the same pattern and send a request
TokenBindingMessage which contains both provided and referred containing a TokenBindingMessage that contains both provided and
TokenBindings (for TP2 and TP1, respectively) to TP2. Note that referred TokenBindings (for TP2 and TP1, respectively) to TP2.
this pattern can continue to further Token Providers. In this Note that this pattern can continue to additional Token Providers.
case, TP2 issues a security token, bound to the client's In this case, TP2 issues a security token, bound to the client's
TokenBinding with TP1, and sends a redirect response to the client TokenBinding with TP1, and sends a redirect response to the client
pointing to TP1. TP1 in turn constructs a security token for the pointing to TP1. TP1 in turn constructs a security token for the
Token Consumer, bound to the TC's referred TokenBinding which had Token Consumer, bound to the TC's referred TokenBinding that had
been conveyed earlier, and sends a redirect response pointing to been conveyed earlier, and sends a redirect response pointing to
the TC, containing the bound security token, to the client. the TC, containing the bound security token, to the client.
The above is intended as only a non-normative example. Details are The above is intended as only a non-normative example. Details are
specific to deployment contexts. Other approaches are possible, but specific to deployment contexts. Other approaches are possible but
are outside the scope of this specification. are outside the scope of this specification.
5.4. Negotiated Key Parameters 5.4. Negotiated Key Parameters
The TLS Extension for Token Binding Protocol Negotiation The TLS extension for Token Binding protocol negotiation [RFC8472]
[I-D.ietf-tokbind-negotiation] allows the server and client to allows the server and client to negotiate the parameters (signature
negotiate the parameters (signature algorithm, length) of the Token algorithm, length) of the Token Binding key pair. It is possible
Binding key pair. It is possible that the Token Binding ID used that the Token Binding ID used between the client and the Token
between the client and the Token Consumer, and the Token Binding ID Consumer, and the Token Binding ID used between the client and the
used between the client and Token Provider, use different key Token Provider, use different key parameters. The client MUST use
parameters. The client MUST use the key parameters negotiated with the key parameters negotiated with the Token Consumer in the
the Token Consumer in the referred_token_binding TokenBinding of the referred_token_binding TokenBinding of the TokenBindingMessage, even
TokenBindingMessage, even if those key parameters are different from if those key parameters are different from the ones negotiated with
the ones negotiated with the server that the header field is sent to. the server that the header field is sent to.
Token Providers SHOULD support all the Token Binding key parameters Token Providers SHOULD support all the Token Binding key parameters
specified in [I-D.ietf-tokbind-protocol]. If a token provider does specified in [RFC8471]. If a Token Provider does not support the key
not support the key parameters specified in the parameters specified in the referred_token_binding TokenBinding in
referred_token_binding TokenBinding in the TokenBindingMessage, it the TokenBindingMessage, it MUST NOT issue a bound token.
MUST NOT issue a bound token.
5.5. Federation Example 5.5. Federation Example
The diagram below shows a typical HTTP Redirect-based Web Browser SSO The diagram below shows a typical HTTP redirect-based web browser
Profile (no artifact, no callbacks), featuring binding of, e.g., a single sign-on (SSO) profile (Section 4.1 of
TLS Token Binding ID into an OpenID Connect ID Token. [OASIS.saml-prof-2.0-os]) (no artifact, no callbacks), featuring the
binding of, for example, a TLS Token Binding ID into an OpenID
Connect ID Token.
Legend: Legend:
+------------+------------------------------------------------------+ +------------+------------------------------------------------------+
| EKM: | TLS Exported Keying Material [RFC5705] | | EKM: | TLS Exported Keying Material [RFC5705] |
| {EKMn}Ksm: | EKM for server "n", signed by private key of TBID | | | |
| | "m", where "n" must represent server receiving the | | {EKMn}Ksm: | EKM for server "n", signed by the private key of |
| | ETBMSG. If a conveyed TB's type is | | | TBID "m", where "n" must represent the server |
| | receiving the ETBMSG. If a conveyed TB's type is |
| | provided_token_binding, then m = n, else if TB's | | | provided_token_binding, then m = n, else if TB's |
| | type is referred_token_binding, then m != n. E.g., | | | type is referred_token_binding, then m != n. For |
| | see step 1b in diagram below. | | | example, see step 1b in the diagram below. |
| | |
| ETBMSG: | "Sec-Token-Binding" HTTP header field conveying an | | ETBMSG: | "Sec-Token-Binding" HTTP header field conveying an |
| | EncodedTokenBindingMessage, in turn conveying | | | EncodedTokenBindingMessage, in turn conveying |
| | TokenBinding (TB)struct(s), e.g.: ETBMSG[[TB]] or | | | TokenBinding (TB)struct(s), e.g., ETBMSG[[TB]] or |
| | ETBMSG[[TB1],[TB2]] | | | ETBMSG[[TB1],[TB2]] |
| ID Token: | the ID Token in OpenID Connect, it is the semantic | | | |
| | equivalent of a SAML "authentication assertion". "ID | | ID Token: | the ID Token in OpenID Connect. It is the semantic |
| | Token w/TBIDn" denotes a "token bound" ID Token | | | equivalent of a SAML "authentication assertion". |
| | "ID Token w/TBIDn" denotes a "token bound" ID Token |
| | containing TBIDn. | | | containing TBIDn. |
| Ks & Kp: | private (aka secret) key, and public key, | | | |
| | respectively, of client-side Token Binding key pair | | Ks and Kp: | private (aka secret) key and public key, |
| | respectively, of the client-side Token Binding key |
| | pair |
| | |
| OIDC: | OpenID Connect | | OIDC: | OpenID Connect |
| TB: | TokenBinding struct containing signed EKM, TBID, and | | | |
| | TB type, e.g.: | | TB: | TokenBinding struct containing a signed EKM, TBID, |
| | and TB type, e.g., |
| | [{EKM1}Ks1,TBID1,provided_token_binding] | | | [{EKM1}Ks1,TBID1,provided_token_binding] |
| | |
| TBIDn: | Token Binding ID for client and server n's token- | | TBIDn: | Token Binding ID for client and server n's token- |
| | bound TLS association. TBIDn contains Kpn. | | | bound TLS association. TBIDn contains Kpn. |
+------------+------------------------------------------------------+ +------------+------------------------------------------------------+
Client, Token Consumer, Token Provider, Client, aka Token Consumer, aka Token Provider, aka
aka: aka: aka: User Agent OpenID Client, OpenID Provider,
User Agent OpenID Client, OpenID Provider, OIDC Relying Party, OIDC Provider,
OIDC Relying Party, OIDC Provider, SAML Relying Party SAML Identity Provider
SAML Relying Party SAML Identity Provider [ server "1" ] [ server "2" ]
[ server "1" ] [ server "2" ] +--------+ +----+ +-----+
+--------+ +----+ +-----+ | Client | | TC | | TP |
| Client | | TC | | TP | +--------+ +----+ +-----+
+--------+ +----+ +-----+ | | |
| | | | | |
| | | | | |
| | | | 0. Client interacts w/TC | |
| 0. Client interacts w/TC | | | over HTTPS, establishes Ks1 and Kp1, TBID1 |
| over HTTPS, establishes Ks1 & Kp1, TBID1 | | ETBMSG[[{EKM1}Ks1,TBID1,provided_token_binding]] |
| ETBMSG[[{EKM1}Ks1,TBID1,provided_token_binding]] | |------------------------------>| |
|------------------------------>| | | | |
| | | | | |
| | | | | |
| | | | 1a. OIDC ID Token request, aka| |
| 1a. OIDC ID Token request, aka| | | "Authentication Request", conveyed with |
| "Authentication Request", conveyed with | | an HTTP response header field of |
| HTTP response header field of: | | Include-Referred-Token-Binding-ID:true. |
| Include-Referred-Token-Binding-ID:true | | Any security-relevant cookies | |
| any security-relevant cookies | | | should contain TBID1. | |
| should contain TBID1 | | +<- - - - - - - - - - - - - - - - | |
+<- - - - - - - - - - - - - - - - | | . | (redirect to TP via 301, 302, | |
. | (redirect to TP via 301, 302, | | . | 303, 307, or 308) | |
. | 303, 307, or 308) | | . | | |
. | | | +------------------------------------------------------->|
+------------------------------------------------------->| | 1b. opens HTTPS w/TP, |
| 1b. opens HTTPS w/TP, | | establishes Ks2, Kp2, TBID2; |
| establishes Ks2, Kp2, TBID2; | | sends a GET or POST with |
| sends GET or POST with | | ETBMSG[[{EKM2}Ks2,TBID2,provided_token_binding], |
| ETBMSG[[{EKM2}Ks2,TBID2,provided_token_binding], | | [{EKM2}Ks1,TBID1,referred_token_binding]] |
| [{EKM2}Ks1,TBID1,referred_token_binding]] | | as well as the ID Token request |
| as well as the ID Token request | | | |
| | | | | |
| | | | | |
| | | | 2. user authentication (if applicable; |
| 2. user authentication (if applicable, | | methods vary; particulars are out of scope) |
| methods vary, particulars are out of scope) | |<====================================================>|
|<====================================================>| | (TP generates ID Token for TC containing TBID1; may |
| (TP generates ID Token for TC containing TBID1, may | | also set cookie(s) containing TBID2 and/or TBID1; |
| also set cookie(s) containing TBID2 and/or TBID1, | | details vary; particulars are out of scope) |
| details vary, particulars are out of scope) | | | |
| | | | | |
| | | | | |
| | | | 3a. ID Token containing Kp1, issued for TC, |
| 3a. ID Token containing Kp1, issued for TC, | | conveyed via OIDC "Authentication Response" |
| conveyed via OIDC "Authentication Response" | +<- - - - - - - - - - - - - - - - - - - - - - - - - - - -|
+<- - - - - - - - - - - - - - - - - - - - - - - - - - - -| . | (redirect to TC) | |
. | (redirect to TC) | | . | | |
. | | | . | | |
. | | | +-------------------------------->| |
+-------------------------------->| | | 3b. HTTPS GET or POST with |
| 3b. HTTPS GET or POST with | | ETBMSG[[{EKM1}Ks1,TBID1,provided_token_binding]] |
| ETBMSG[[{EKM1}Ks1,TBID1,provided_token_binding]] | | conveying an Authentication Response containing |
| conveying Authn Response containing | | an ID Token w/TBID1, issued for TC |
| ID Token w/TBID1, issued for TC | | | |
| | | | | |
| | | | | |
| | | | 4. user is signed on; any security-relevant cookie(s)|
| 4. user is signed-on, any security-relevant cookie(s)| | that is set SHOULD contain TBID1 |
| that are set SHOULD contain TBID1 | |<------------------------------| |
|<------------------------------| | | | |
| | | | | |
| | |
6. Implementation Considerations 6. Implementation Considerations
HTTPS-based applications may have multi-party use cases other than, HTTPS-based applications may have multi-party use cases other than,
or in addition to, the HTTP redirect-based signaling-and-conveyance or in addition to, the HTTP redirect-based signaling and conveyance
of referred token bindings, as presented above in Section 5.3. of referred Token Bindings, as presented above in Section 5.3.
Thus, Token Binding implementations should provide APIs for such Thus, Token Binding implementations should provide APIs for such
applications to generate Token Binding messages containing Token applications to generate Token Binding messages containing Token
Binding IDs of various application-specified Token Binding types, to Binding IDs of various application-specified Token Binding types, to
be conveyed by the Sec-Token-Binding header field. be conveyed by the Sec-Token-Binding header field.
However, Token Binding implementations MUST only convey Token Binding However, Token Binding implementations MUST only convey Token Binding
IDs to servers if signaled to do so by an application. For example, IDs to servers if signaled to do so by an application. Signaling
a server can return an Include-Referred-Token-Binding-ID HTTP mechanisms other than the Include-Referred-Token-Binding-ID HTTP
response header field to an application, which then signals to the response header field are possible, but these mechanisms are outside
Token Binding implementation that it intends to convey the Token the scope of this specification.
Binding ID used with this server to another server. Other signaling
mechanisms are possible, and are specific to the application layer
protocol, but are outside the scope of this specification.
NOTE: See Section 8 ("Privacy Considerations"), for privacy guidance NOTE: See Section 8 ("Privacy Considerations") for privacy guidance
regarding the use of this functionality. regarding the use of this functionality.
7. Security Considerations 7. Security Considerations
7.1. Security Token Replay 7.1. Security Token Replay
The goal of the Federated Token Binding mechanisms is to prevent The goal of the federated Token Binding mechanisms is to prevent
attackers from exporting and replaying tokens used in protocols attackers from exporting and replaying tokens used in protocols
between the client and Token Consumer, thereby impersonating between the client and the Token Consumer, thereby impersonating
legitimate users and gaining access to protected resources. Although legitimate users and gaining access to protected resources. Although
bound tokens can still be replayed by any malware present in clients bound tokens can still be replayed by any malware present in clients
(which may be undetectable by a server), in order to export bound (which may be undetectable to a server), in order to export bound
tokens to other machines and successfully replay them, attackers also tokens to other machines and successfully replay them, attackers also
need to export the corresponding Token Binding private keys. Token need to export the corresponding Token Binding private keys. Token
Binding private keys are therefore high-value assets and SHOULD be Binding private keys are therefore high-value assets and SHOULD be
strongly protected, ideally by generating them in a hardware security strongly protected, ideally by generating them in a hardware security
module that prevents key export. module that prevents key export.
This consideration is a special case of the Security Token Replay This consideration is a special case of the scenario described in
security consideration laid out in the The Token Binding Protocol Section 7.1 ("Security Token Replay") of [RFC8471].
[I-D.ietf-tokbind-protocol] specification.
7.2. Sensitivity of the Sec-Token-Binding Header 7.2. Sensitivity of the Sec-Token-Binding Header
The purpose of the Token Binding protocol is to convince the server The purpose of the Token Binding protocol is to convince the server
that the client that initiated the TLS connection controls a certain that the client that initiated the TLS connection controls a certain
key pair. For the server to correctly draw this conclusion after key pair. For the server to correctly draw this conclusion after
processing the Sec-Token-Binding header field, certain secrecy and processing the Sec-Token-Binding header field, certain secrecy and
integrity requirements must be met. integrity requirements must be met.
For example, the client's Token Binding private key must be kept For example, the client must keep its Token Binding private key
secret by the client. If the private key is not secret, then another secret. If the private key is not secret, then another actor in the
actor in the system could create a valid Token Binding header field, system could create a valid Token Binding header field and thereby
impersonating the client. This can render the main purpose of the impersonate the client. This can render the main purpose of the
protocol - to bind bearer tokens to certain clients - moot. protocol -- to bind bearer tokens to certain clients -- moot.
Consider, for example, an attacker who obtained (perhaps through a Consider, for example, an attacker who obtained (perhaps through a
network intrusion) an authentication cookie that a client uses with a network intrusion) an authentication cookie that a client uses with a
certain server. Consider further that the server bound that cookie certain server. Consider further that the server bound that cookie
to the client's Token Binding ID precisely to thwart misuse of the to the client's Token Binding ID precisely to thwart misuse of the
cookie. If the attacker were to come into possession of the client's cookie. If the attacker were to come into possession of the client's
private key, he could then establish a TLS connection with the server private key, they could then establish a TLS connection with the
and craft a Sec-Token-Binding header field that matches the binding server and craft a Sec-Token-Binding header field that matches the
present in the cookie, thus successfully authenticating as the binding present in the cookie, thus successfully authenticating as
client, and gaining access to the client's data at the server. The the client and gaining access to the client's data at the server.
Token Binding protocol, in this case, did not successfully bind the The Token Binding protocol, in this case, did not successfully bind
cookie to the client. the cookie to the client.
Likewise, we need integrity protection of the Sec-Token-Binding Likewise, we need integrity protection of the Sec-Token-Binding
header field. A client should not be tricked into sending a Sec- header field. A client should not be tricked into sending to a
Token-Binding header field to a server that contains Token Binding server a Sec-Token-Binding header field that contains Token Bindings
messages about key pairs that the client does not control. Consider signed with any Token Binding keys that the client does not control.
an attacker A that somehow has knowledge of the exported keying
material (EKM) for a TLS connection between a client C and a server
S. (While that is somewhat unlikely, it is also not entirely out of
the question, since the client might not treat the EKM as a secret -
after all, a pre-image-resistant hash function has been applied to
the TLS master secret, making it impossible for someone knowing the
EKM to recover the TLS master secret. Such considerations might lead
some clients to not treat the EKM as a secret.) Such an attacker A
could craft a Sec-Token-Binding header field with A's key pair over
C's EKM. If the attacker could now trick C into sending such a
header field to S, it would appear to S as if C controls a certain
key pair, when in fact it does not (the attacker A controls the key
pair).
If A has a pre-existing relationship with S (perhaps has an account Consider an attacker A that somehow has knowledge of the Exported
on S), it now appears to the server S as if A is connecting to it, Keying Material (EKM) for a TLS connection between a client C and a
even though it is really C. (If the server S does not simply use server S. (While that is somewhat unlikely, it is also not entirely
Token Binding IDs to identify clients, but also uses bound out of the question, since the client might not treat the EKM as a
secret -- after all, a pre-image-resistant hash function has been
applied to the TLS master secret, making it impossible for someone
knowing the EKM to recover the TLS master secret. Such
considerations might lead some clients to not treat the EKM as a
secret.) Such an attacker A could craft a Sec-Token-Binding header
field with A's key pair over C's EKM. If the attacker could now
trick C into sending such a header field to S, it would appear to S
as if C controls a certain key pair, when in fact it does not (the
attacker A controls the key pair).
If A has a pre-existing relationship with S (e.g., perhaps has an
account on S), it now appears to the server S as if A is connecting
to it, even though it is really C. (If the server S does not simply
use Token Binding IDs to identify clients but also uses bound
authentication cookies, then A would also have to trick C into authentication cookies, then A would also have to trick C into
sending one of A's cookies to S, which it can do through a variety of sending one of A's cookies to S, which it can do through a variety of
means - inserting cookies through Javascript APIs, setting cookies means -- inserting cookies through JavaScript APIs, setting cookies
through related-domain attacks, etc.) In other words, A tricked C through related-domain attacks, etc.) In other words, in this
into logging into A's account on S. This could lead to a loss of scenario, A can trick C into logging into A's account on S. This
privacy for C, since A presumably has some other way to also access could lead to a loss of privacy for C, since A presumably has some
the account, and can thus indirectly observe C's behavior (for other way to also access the account and can thus indirectly observe
example, if S has a feature that lets account holders see their C's behavior (for example, if S has a feature that lets account
activity history on S). holders see their activity history on S).
Therefore, we need to protect the integrity of the Sec-Token-Binding Therefore, we need to protect the integrity of the Sec-Token-Binding
header field. One eTLD+1 should not be able to set the Sec-Token- header field. One eTLD+1 should not be able to set the
Binding header field (through a DOM API or otherwise) that the User Sec-Token-Binding header field (through a Document Object Model (DOM)
API [W3C.REC-DOM-Level-3-Core-20040407] or otherwise) that the User
Agent uses with another eTLD+1. Employing the "Sec-" header field Agent uses with another eTLD+1. Employing the "Sec-" header field
prefix helps to meet this requirement by denoting the header field prefix helps to meet this requirement by denoting the header field
name to be a "forbidden header name", see [fetch-spec]. name as a "forbidden header name"; see [fetch-spec].
7.3. Securing Federated Sign-On Protocols 7.3. Securing Federated Sign-On Protocols
As explained above, in a federated sign-in scenario, a client will As explained above, in a federated sign-on scenario, a client will
prove possession of two different Token Binding private keys to a prove possession of two different Token Binding private keys to a
Token Provider: One private key corresponds to the "provided" Token Token Provider: one private key corresponds to the "provided" Token
Binding ID (which the client normally uses with the Token Provider), Binding ID (which the client normally uses with the Token Provider),
and the other is the Token Binding private key corresponding to the and the other is the Token Binding private key corresponding to the
"referred" Token Binding ID (which the client normally uses with the "referred" Token Binding ID (which the client normally uses with the
Token Consumer). The Token Provider is expected to issue a token Token Consumer). The Token Provider is expected to issue a token
that is bound to the referred Token Binding ID. that is bound to the Referred Token Binding ID.
Both proofs (that of the provided Token Binding private key and that Both proofs (that of the provided Token Binding private key and that
of the referred Token Binding private key) are necessary. To show of the referred Token Binding private key) are necessary. To show
this, consider the following scenario: this, consider the following scenario:
o The client has an authentication token with the Token Provider o The client has an authentication token with the Token Provider
that is bound to the client's Token Binding ID used with that that is bound to the client's Token Binding ID used with that
Token Provider. Token Provider.
o The client wants to establish a secure (i.e., free of men-in-the- o The client wants to establish a secure (i.e., free of men-in-the-
middle) authenticated session with the Token Consumer, but has not middle) authenticated session with the Token Consumer but has not
done so yet (in other words, we are about to run the federated yet done so (in other words, we are about to run the federated
sign-on protocol). sign-on protocol).
o A man-in-the-middle is allowed to intercept the connection between o A man-in-the-middle is allowed to intercept the connection between
client and Token Consumer or between Client and Token Provider (or the client and the Token Consumer or between the client and the
both). Token Provider (or both).
The goal is to detect the presence of the man-in-the-middle in these The goal is to detect the presence of the man-in-the-middle in these
scenarios. scenarios.
First, consider a man-in-the-middle between the client and the Token First, consider a man-in-the-middle between the client and the Token
Provider. Recall that we assume that the client possesses a bound Provider. Recall that we assume that the client possesses a bound
authentication token (e.g., cookie) for the Token Provider. The man- authentication token (e.g., cookie) for the Token Provider. The
in-the-middle can intercept and modify any message sent by the client man-in-the-middle can intercept and modify any message sent by the
to the Token Provider, and any message sent by the Token Provider to client to the Token Provider and any message sent by the Token
the client. (This means, among other things, that the man-in-the- Provider to the client. (This means, among other things, that the
middle controls the Javascript running at the client in the origin of man-in-the-middle controls the JavaScript running at the client in
the Token Provider.) It is not, however, in possession of the the origin of the Token Provider.) It is not, however, in possession
client's Token Binding private key. Therefore, it can either choose of the client's Token Binding private key. Therefore, it can choose
to replace the Token Binding ID in requests from the client to the to either (1) replace the Token Binding ID in requests from the
Token Provider, and create a Sec-Token-Binding header field that client to the Token Provider and create a Sec-Token-Binding header
matches the TLS connection between the man-in-the-middle and the field that matches the TLS connection between the man-in-the-middle
Token Provider, or it can choose to leave the Sec-Token-Binding and the Token Provider or (2) leave the Sec-Token-Binding header
header field unchanged. If it chooses the latter, the signature in field unchanged. If it chooses the latter, the signature in the
the Token Binding message (created by the original client on the Token Binding message (created by the original client on the EKM for
exported keying material (EKM) for the connection between client and the connection between the client and the man-in-the-middle) will not
man-in-the-middle) will not match a signature on the EKM between man- match a signature on the EKM between the man-in-the-middle and the
in-the-middle and the Token Provider. If it chooses the former (and Token Provider. If it chooses the former (and creates its own
creates its own signature, using its own Token Binding private key, signature, using its own Token Binding private key, over the EKM for
over the EKM for the connection between itself, the man-in-the- the connection between itself, the man-in-the-middle, and the Token
middle, and Token Provider), then the Token Binding message will Provider), then the Token Binding message will match the connection
match the connection between man-in-the-middle and Token Provider, between the man-in-the-middle and the Token Provider, but the Token
but the Token Binding ID in the message will not match the Token Binding ID in the message will not match the Token Binding ID that
Binding ID that the client's authentication token is bound to. the client's authentication token is bound to. Either way, the
Either way, the man-in-the-middle is detected by the Token Provider, man-in-the-middle is detected by the Token Provider, but only if the
but only if the proof of possession of the provided Token Binding proof of possession of the provided Token Binding private key is
private key is required in the protocol (as is done above). required in the protocol (as is done above).
Next, consider the presence of a man-in-the-middle between client and Next, consider the presence of a man-in-the-middle between the client
Token Consumer. That man-in-the-middle can intercept and modify any and the Token Consumer. That man-in-the-middle can intercept and
message sent by the client to the Token Consumer and any message sent modify any message sent by the client to the Token Consumer and any
by the Token Consumer to the client. The Token Consumer is the party message sent by the Token Consumer to the client. The Token Consumer
that redirects the client to the Token Provider. In this case, the is the party that redirects the client to the Token Provider. In
man-in-the-middle controls the redirect URL and can tamper with any this case, the man-in-the-middle controls the redirect URL and can
redirect URL issued by the Token Consumer (as well as with any tamper with any redirect URL issued by the Token Consumer (as well as
Javascript running in the origin of the Token Consumer). The goal of with any JavaScript running in the origin of the Token Consumer).
the man-in-the-middle is to trick the Token Provider into issuing a The goal of the man-in-the-middle is to trick the Token Provider into
token bound to its Token Binding ID, not to the Token Binding ID of issuing a token bound to its Token Binding ID and not to the Token
the legitimate client. To thwart this goal of the man-in-the-middle, Binding ID of the legitimate client. To thwart this goal of the
the client's referred Token Binding ID must be communicated to the man-in-the-middle, the client's Referred Token Binding ID must be
Token Producer in a manner that cannot be affected by the man-in-the- communicated to the Token Provider in a manner that cannot be
middle (who, as we recall, can modify redirect URLs and Javascript at affected by the man-in-the-middle (who, as mentioned above, can
the client). Including the referred Token Binding structure in the modify redirect URLs and JavaScript at the client). Including the
Sec-Token-Binding header field (as opposed to, say, including the referred TokenBinding structure in the Sec-Token-Binding header field
referred Token Binding ID in an application-level message as part of (as opposed to, say, including the Referred Token Binding ID in an
the redirect URL) is one way to assure that the man-in-the-middle application-level message as part of the redirect URL) is one way to
between client and Token Consumer cannot affect the communication of assure that the man-in-the-middle between the client and the Token
the referred Token Binding ID to the Token Provider. Consumer cannot affect the communication of the Referred Token
Binding ID to the Token Provider.
Therefore, the Sec-Token-Binding header field in the federated sign- Therefore, the Sec-Token-Binding header field in the federated
on use case contains both: a proof of possession of the provided sign-on use case contains both a proof of possession of the provided
Token Binding key, as well as a proof of possession of the referred Token Binding key and a proof of possession of the referred Token
Token Binding key. Binding key.
Note that the presence of Token Binding does not relieve the Token Note that the presence of Token Binding does not relieve the Token
Provider and Token Consumer from performing various checks to ensure Provider and Token Consumer from performing various checks to ensure
the security of clients during federated sign-on protocols. These the security of clients during the use of federated sign-on
include the following: protocols. These include the following:
o The Token Provider should not issue tokens to Token Consumers that o The Token Provider should not issue tokens to Token Consumers that
have been shown to act maliciously. To aid in this, the have been shown to act maliciously. To aid in this, the
federation protocol should identify the Token Consumer to the federation protocol should identify the Token Consumer to the
Token Provider (e.g., through OAuth client IDs or similar Token Provider (e.g., through OAuth client IDs or similar
mechanisms), and the Token Provider should ensure that tokens are mechanisms), and the Token Provider should ensure that tokens are
indeed issued to the Token Consumer identified in the token indeed issued to the Token Consumer identified in the token
request (e.g., by verifying that the redirect URI is associated request (e.g., by verifying that the redirect URI is associated
with the OAuth client ID.) with the OAuth client ID).
o The Token Consumer should verify that the tokens were issued for o The Token Consumer should verify that the tokens were issued for
it, and not some other token consumer. To aid in this, the it and not for some other Token Consumer. To aid in this, the
federation protocol should include an audience parameter in the federation protocol should include an audience parameter in the
token response, or apply equivalent mechanisms (the implicit OAuth token response or apply equivalent mechanisms (the implicit OAuth
flow requires Token Consumers to identify themselves when they flow requires Token Consumers to identify themselves when they
exchange OAuth authorization codes for OAuth refresh tokens, exchange OAuth authorization codes for OAuth refresh tokens,
leaving it up to the Token Provider to verify that the OAuth leaving it up to the Token Provider to verify that the OAuth
authorization was delivered to the correct Token Consumer). authorization was delivered to the correct Token Consumer).
8. Privacy Considerations 8. Privacy Considerations
8.1. Scoping of Token Binding Key Pairs 8.1. Scoping of Token Binding Key Pairs
Clients use different Token Binding key pairs for different servers, Clients use different Token Binding key pairs for different servers,
so as to not allow Token Binding to become a tracking tool across so as to not allow Token Binding to become a tracking tool across
different servers. However, the scoping of the Token Binding key different servers. However, the scoping of the Token Binding key
pairs to servers varies according to the scoping rules of the pairs to servers varies according to the scoping rules of the
application protocol (Section 4.1 of [I-D.ietf-tokbind-protocol]). application protocol (Section 4.1 of [RFC8471]).
In the case of HTTP cookies, servers may use Token Binding to secure In the case of HTTP cookies, servers may use Token Binding to secure
their cookies. These cookies can be attached to any sub-domain of their cookies. These cookies can be attached to any subdomain of
effective top-level domains (eTLDs), and clients therefore should use effective top-level domains (eTLDs), and clients therefore should use
the same Token Binding key pair across such subdomains. This will the same Token Binding key pair across such subdomains. This will
ensure that any server capable of receiving the cookie will see the ensure that any server capable of receiving the cookie will see the
same Token Binding ID from the client, and thus be able to verify the same Token Binding ID from the client and thus be able to verify the
token binding of the cookie. See Section 2.1, above. Token Binding of the cookie. See Section 2.1 above.
If the client application is not a Web browser, it may have If the client application is not a web browser, it may have
additional knowledge about the relationship between different additional knowledge about the relationship between different
servers. For example, the client application might be aware of the servers. For example, the client application might be aware of the
fact that two servers play the role of Relying Party and Identity fact that two servers play the roles of Relying Party and Identity
Provider in a federated sign-on protocol, and that they therefore Provider, respectively, in a federated sign-on protocol and that they
share the identity of the user. In such cases, it is permissible to therefore share the identity of the user. In such cases, it is
use different Token Binding key pair scoping rules, such as using the permissible to use different Token Binding key-pair scoping rules,
same Token Binding key pair for both the Relying Party and the such as using the same Token Binding key pair for both the Relying
Identity Provider. Absent such special knowledge, conservative key- Party and the Identity Provider. Absent such special knowledge,
scoping rules should be used, assuring that clients use different conservative key-pair scoping rules should be used, assuring that
Token Binding key pairs with different servers. clients use different Token Binding key pairs with different servers.
8.2. Lifetime of Token Binding Key Pairs 8.2. Lifetime of Token Binding Key Pairs
Token Binding key pairs do not have an expiration time. This means Token Binding key pairs do not have an expiration time. This means
that they can potentially be used by a server to track a user for an that they can potentially be used by a server to track a user for an
extended period of time (similar to a long-lived cookie). HTTPS extended period of time (similar to a long-lived cookie). HTTPS
clients such as Web user agents SHOULD therefore provide a user clients such as web User Agents SHOULD therefore provide a user
interface for discarding Token Binding key pairs (similar to the interface for discarding Token Binding key pairs (similar to the
affordances provided to delete cookies). controls provided for deleting cookies).
If a user agent provides modes such as private browsing mode in which If a User Agent provides modes such as private browsing mode in which
the user is promised that browsing state such as cookies are the user is promised that browsing state such as cookies are
discarded after the session is over, the user agent MUST also discard discarded after the session is over, the User Agent MUST also discard
Token Binding key pairs from such modes after the session is over. Token Binding key pairs from such modes after the session is over.
Generally speaking, users should be given the same level of control Generally speaking, users should be given the same level of control
over lifetime of Token Binding key pairs as they have over cookies or over the lifetime of Token Binding key pairs as they have over
other potential tracking mechanisms. cookies or other potential tracking mechanisms.
8.3. Correlation 8.3. Correlation
An application's various communicating endpoints that receive Token An application's various communicating endpoints that receive Token
Binding IDs for TLS connections other than their own obtain Binding IDs for TLS connections other than their own obtain
information about the application's other TLS connections. (In this information about the application's other TLS connections. (In this
context, "an application" is a combination of client-side and server- context, "an application" is a combination of client-side and
side components, communicating over HTTPS, where the client side may server-side components, communicating over HTTPS, where the client
be either or both Web browser-based or native application-based.) side may be web-browser-based, native-application-based, or both.)
These other Token Binding IDs can serve as correlation handles for These other Token Binding IDs can serve as correlation handles for
the endpoints of the other connections. If the receiving endpoints the endpoints of the other connections. If the receiving endpoints
are otherwise aware of these other connections, then no additional are otherwise aware of these other connections, then no additional
information is being exposed. For instance, if in a redirect-based information is being exposed. For instance, if in a redirect-based
federation protocol, the Identity Provider and Relying Party already federation protocol the Identity Provider and Relying Party already
possess URLs for one another, also having Token Binding IDs for these possess URLs for one another, then also having Token Binding IDs for
connections does not provide additional correlation information. If these connections does not provide additional correlation
not, then, by providing the other Token Binding IDs, additional information. If not, by providing the other Token Binding IDs,
information is exposed that can be used to correlate the other additional information is then exposed that can be used to correlate
endpoints. In such cases, a privacy analysis of enabled correlations the other endpoints. In such cases, a privacy analysis of enabled
and their potential privacy impacts should be performed as part of correlations and their potential privacy impacts should be performed
the application design decisions of how, and whether, to utilize as part of the application design decisions of how, and whether, to
Token Binding. utilize Token Binding.
Also, Token Binding implementations must take care to only reveal Also, Token Binding implementations must take care to only reveal
Token Binding IDs to other endpoints if the application associated Token Binding IDs to other endpoints if signaled to do so by the
with a Token Binding ID signals to do so, see Section 6 application associated with a Token Binding ID; see Section 6
("Implementation Considerations"). ("Implementation Considerations").
Finally, care should be taken to ensure that unrelated applications Finally, care should be taken to ensure that unrelated applications
do not obtain information about each other's Token Bindings. For do not obtain information about each other's Token Bindings. For
instance, a Token Binding implementation shared between multiple instance, a Token Binding implementation shared between multiple
applications on a given system should prevent unrelated applications applications on a given system should prevent unrelated applications
from obtaining each other's Token Binding information. This may be from obtaining each other's Token Binding information. This may be
accomplished by using techniques such as application isolation and accomplished by using techniques such as application isolation and
key segregation, depending upon system capabilities. key segregation, depending upon system capabilities.
9. IANA Considerations 9. IANA Considerations
Below are the Internet Assigned Numbers Authority (IANA) Permanent Below is the Internet Assigned Numbers Authority (IANA) "Permanent
Message Header Field registration information per [RFC3864]. Message Header Field Names" registration information per [RFC3864].
Header field name: Sec-Token-Binding
Applicable protocol: HTTP
Status: standard
Author/Change controller: IETF
Specification document(s): this one
Header field name: Include-Referred-Token-Binding-ID
Applicable protocol: HTTP
Status: standard
Author/Change controller: IETF
Specification document(s): this one
10. Acknowledgements
This document incorporates comments and suggestions offered by Eric
Rescorla, Gabriel Montenegro, Martin Thomson, Vinod Anupam, Anthony
Nadalin, Michael B. Jones, Bill Cox, Brian Campbell, and others.
This document was produced under the chairmanship of John Bradley and
Leif Johansson. The area directors included Eric Rescorla, Kathleen
Moriarty and Stephen Farrell.
11. References Header Field name: Sec-Token-Binding
Protocol: HTTP
Status: standard
Reference: This document
11.1. Normative References Header Field name: Include-Referred-Token-Binding-ID
Protocol: HTTP
Status: standard
Reference: This document
[I-D.ietf-tokbind-negotiation] 10. References
Popov, A., Nystrom, M., Balfanz, D., and A. Langley,
"Transport Layer Security (TLS) Extension for Token
Binding Protocol Negotiation", draft-ietf-tokbind-
negotiation-14 (work in progress), May 2018.
[I-D.ietf-tokbind-protocol] 10.1. Normative References
Popov, A., Nystrom, M., Balfanz, D., Langley, A., and J.
Hodges, "The Token Binding Protocol Version 1.0", draft-
ietf-tokbind-protocol-19 (work in progress), May 2018.
[PSL] Mozilla, "Public Suffix List, https://publicsuffix.org/", [PSL] Mozilla, "Public Suffix List",
<https://publicsuffix.org/>. <https://publicsuffix.org/>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>. <https://www.rfc-editor.org/info/rfc2818>.
skipping to change at page 23, line 13 skipping to change at page 23, line 27
<https://www.rfc-editor.org/info/rfc7231>. <https://www.rfc-editor.org/info/rfc7231>.
[RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for [RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015, HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
<https://www.rfc-editor.org/info/rfc7541>. <https://www.rfc-editor.org/info/rfc7541>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
11.2. Informative References [RFC8471] Popov, A., Ed., Nystroem, M., Balfanz, D., and J. Hodges,
"The Token Binding Protocol Version 1.0", RFC 8471,
DOI 10.17487/RFC8471, October 2018,
<https://www.rfc-editor.org/info/rfc8471>.
[RFC8472] Popov, A., Ed., Nystroem, M., and D. Balfanz, "Transport
Layer Security (TLS) Extension for Token Binding Protocol
Negotiation", RFC 8472, DOI 10.17487/RFC8472, October
2018, <https://www.rfc-editor.org/info/rfc8472>.
10.2. Informative References
[fetch-spec] [fetch-spec]
WhatWG, "Fetch", Living Standard , WhatWG, "Fetch", Living Standard,
<https://fetch.spec.whatwg.org/>. <https://fetch.spec.whatwg.org/>.
[I-D.ietf-tokbind-tls13]
Harper, N., "Token Binding for Transport Layer Security
(TLS) Version 1.3 Connections", draft-ietf-tokbind-
tls13-01 (work in progress), May 2018.
[OASIS.saml-core-2.0-os] [OASIS.saml-core-2.0-os]
Cantor, S., Kemp, J., Philpott, R., and E. Maler, Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocol for the OASIS Security Assertion "Assertions and Protocols for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core- Markup Language (SAML) V2.0", OASIS Standard
2.0-os, March 2005, <http://docs.oasis- saml-core-2.0-os, March 2005, <http://docs.oasis-open.org/
open.org/security/saml/v2.0/saml-core-2.0-os.pdf>. security/saml/v2.0/saml-core-2.0-os.pdf>.
[OASIS.saml-prof-2.0-os]
Hughes, J., Ed., Cantor, S., Ed., Hodges, J., Ed., Hirsch,
F., Ed., Mishra, P., Ed., Philpott, R., Ed., and E. Maler,
Ed., "Profiles for the OASIS Security Assertion Markup
Language (SAML) V2.0", OASIS Standard
OASIS.saml-profiles-2.0-os, March 2005,
<http://docs.oasis-open.org/security/
saml/v2.0/saml-profiles-2.0-os.pdf>.
[OpenID.Core] [OpenID.Core]
Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and Sakimura, N., Bradley, J., Jones, M., de Medeiros, B., and
C. Mortimore, "OpenID Connect Core 1.0", August 2015, C. Mortimore, "OpenID Connect Core 1.0 incorporating
errata set 1", November 2014,
<http://openid.net/specs/openid-connect-core-1_0.html>. <http://openid.net/specs/openid-connect-core-1_0.html>.
[RFC5746] Rescorla, E., Ray, M., Dispensa, S., and N. Oskov,
"Transport Layer Security (TLS) Renegotiation Indication
Extension", RFC 5746, DOI 10.17487/RFC5746, February 2010,
<https://www.rfc-editor.org/info/rfc5746>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework", [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012, RFC 6749, DOI 10.17487/RFC6749, October 2012,
<https://www.rfc-editor.org/info/rfc6749>. <https://www.rfc-editor.org/info/rfc6749>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540, Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015, DOI 10.17487/RFC7540, May 2015,
<https://www.rfc-editor.org/info/rfc7540>. <https://www.rfc-editor.org/info/rfc7540>.
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A., [TOKENBIND-TLS13]
Langley, A., and M. Ray, "Transport Layer Security (TLS) Harper, N., "Token Binding for Transport Layer Security
Session Hash and Extended Master Secret Extension", (TLS) Version 1.3 Connections", Work in Progress,
RFC 7627, DOI 10.17487/RFC7627, September 2015, draft-ietf-tokbind-tls13-01, May 2018.
<https://www.rfc-editor.org/info/rfc7627>.
[TRIPLE-HS] [W3C.REC-DOM-Level-3-Core-20040407]
Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti, Le Hors, A., Ed., Le Hegaret, P., Ed., Wood, L., Ed.,
A., and P. Strub, "Triple Handshakes and Cookie Cutters: Nicol, G., Ed., Robie, J., Ed., Champion, M., Ed., and S.
Breaking and Fixing Authentication over TLS. IEEE Byrne, Ed., "Document Object Model (DOM) Level 3 Core
Symposium on Security and Privacy", 2014. Specification", World Wide Web Consortium Recommendation
REC-DOM-Level-3-Core-20040407, April 2004,
<https://www.w3.org/TR/2004/
REC-DOM-Level-3-Core-20040407>.
Acknowledgements
This document incorporates comments and suggestions offered by Eric
Rescorla, Gabriel Montenegro, Martin Thomson, Vinod Anupam, Anthony
Nadalin, Michael B. Jones, Bill Cox, Brian Campbell, and others.
This document was produced under the chairmanship of John Bradley and
Leif Johansson. The area directors included Eric Rescorla, Kathleen
Moriarty, and Stephen Farrell.
Authors' Addresses Authors' Addresses
Andrei Popov Andrei Popov
Microsoft Corp. Microsoft Corp.
USA United States of America
Email: andreipo@microsoft.com Email: andreipo@microsoft.com
Magnus Nystroem Magnus Nystroem
Microsoft Corp. Microsoft Corp.
USA United States of America
Email: mnystrom@microsoft.com Email: mnystrom@microsoft.com
Dirk Balfanz (editor) Dirk Balfanz (editor)
Google Inc. Google Inc.
USA United States of America
Email: balfanz@google.com Email: balfanz@google.com
Adam Langley
Google Inc.
USA
Email: agl@google.com
Nick Harper Nick Harper
Google Inc. Google Inc.
USA United States of America
Email: nharper@google.com Email: nharper@google.com
Jeff Hodges Jeff Hodges
PayPal Kings Mountain Systems
USA United States of America
Email: Jeff.Hodges@paypal.com Email: Jeff.Hodges@KingsMountain.com
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