draft-ietf-tokbind-https-03.txt   draft-ietf-tokbind-https-04.txt 
Internet Engineering Task Force A. Popov Internet Engineering Task Force A. Popov
Internet-Draft M. Nystroem Internet-Draft M. Nystroem
Intended status: Standards Track Microsoft Corp. Intended status: Standards Track Microsoft Corp.
Expires: September 22, 2016 D. Balfanz, Ed. Expires: January 8, 2017 D. Balfanz, Ed.
A. Langley A. Langley
Google Inc. Google Inc.
J. Hodges J. Hodges
Paypal Paypal
March 21, 2016 July 7, 2016
Token Binding over HTTP Token Binding over HTTP
draft-ietf-tokbind-https-03 draft-ietf-tokbind-https-04
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 authentication tokens (such as servers to cryptographically bind authentication tokens (such as
cookies and OAuth tokens) to a TLS [RFC5246] connection. cookies and OAuth tokens) to TLS [RFC5246] connections.
We describe both _first-party_ as well as _federated_ scenarios. In We describe both _first-party_ and _federated_ scenarios. In a
a first-party scenario, an HTTP server issues a security token (such first-party scenario, an HTTP server is able to cryptographically
as a cookie) to a client, and expects the client to send the security bind the security tokens it issues to a client, and which the client
token back to the server at a later time in order to authenticate. subsequently returns to the server, to the TLS connection between the
Binding the token to the TLS connection between client and server client and server. Such bound security tokens are protected from
protects the security token from theft, and ensures that the security misuse since the server can generally detect if they are replayed
token can only be used by the client that it was issued to. 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 [RFC5246] connection cryptographically bind security tokens to a TLS connection that the
that the client has with a _different_ server than the one issuing client has with a _different_ server than the one issuing the token.
the token.
This Internet-Draft is a companion document to The Token Binding This Internet-Draft is a companion document to The Token Binding
Protocol [TBPROTO] Protocol [I-D.ietf-tokbind-protocol]
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 22, 2016. This Internet-Draft will expire on January 8, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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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 Header . . . . . . . . . . . . . . . . 4 2. The Sec-Token-Binding Header Field . . . . . . . . . . . . . 4
3. Federation Use Cases . . . . . . . . . . . . . . . . . . . . 4 2.1. HTTPS Token Binding Key Pair Scoping . . . . . . . . . . 4
3.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 4 3. First-party Use Cases . . . . . . . . . . . . . . . . . . . . 5
3.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Federation Use Cases . . . . . . . . . . . . . . . . . . . . 5
3.3. HTTP Redirects . . . . . . . . . . . . . . . . . . . . . 6 4.1. Introduction . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Negotiated Key Parameters . . . . . . . . . . . . . . . . 7 4.2. Overview . . . . . . . . . . . . . . . . . . . . . . . . 6
3.5. Federation Example . . . . . . . . . . . . . . . . . . . 7 4.3. HTTP Redirects . . . . . . . . . . . . . . . . . . . . . 7
4. Security Considerations . . . . . . . . . . . . . . . . . . . 10 4.4. Negotiated Key Parameters . . . . . . . . . . . . . . . . 9
4.1. Security Token Replay . . . . . . . . . . . . . . . . . . 10 4.5. Federation Example . . . . . . . . . . . . . . . . . . . 9
4.2. Triple Handshake Vulnerability in TLS . . . . . . . . . . 10 5. Security Considerations . . . . . . . . . . . . . . . . . . . 12
4.3. Sensitivity of the Sec-Token-Binding Header . . . . . . . 10 5.1. Security Token Replay . . . . . . . . . . . . . . . . . . 12
4.4. Securing Federated Sign-On Protocols . . . . . . . . . . 11 5.2. Triple Handshake Vulnerability in TLS 1.2 and Older TLS
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 13 Versions . . . . . . . . . . . . . . . . . . . . . . . . 12
5.1. Scoping of Token Binding Keys . . . . . . . . . . . . . . 13 5.3. Sensitivity of the Sec-Token-Binding Header . . . . . . . 12
5.2. Life Time of Token Binding Keys . . . . . . . . . . . . . 14 5.4. Securing Federated Sign-On Protocols . . . . . . . . . . 13
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 6. Privacy Considerations . . . . . . . . . . . . . . . . . . . 15
6.1. Normative References . . . . . . . . . . . . . . . . . . 14 6.1. Scoping of Token Binding Keys . . . . . . . . . . . . . . 15
6.2. Informative References . . . . . . . . . . . . . . . . . 15 6.2. Life Time of Token Binding Keys . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction 1. Introduction
The Token Binding Protocol [TBPROTO] defines a Token Binding ID for a The Token Binding Protocol [I-D.ietf-tokbind-protocol] defines a
TLS connection between a client and a server. The Token Binding ID Token Binding ID for a TLS connection between a client and a server.
of a TLS connection is related to a private key that the client The Token Binding ID of a TLS connection is related to a private key,
proves possession of to the server, and is long-lived (i.e., that the client proves possession of to the server, and is long-lived
subsequent TLS connections between the same client and server have (i.e., subsequent TLS connections between the same client and server
the same Token Binding ID). When issuing a security token (e.g. an have the same Token Binding ID). When issuing a security token (e.g.
HTTP cookie or an OAuth token) to a client, the server can include an HTTP cookie or an OAuth token) to a client, the server can include
the Token Binding ID in the token, thus cryptographically binding the the Token Binding ID in the token, thus cryptographically binding the
token to TLS connections between that particular client and server, token to TLS connections between that particular client and server,
and inoculating the token against theft by attackers. and inoculating the token against abuse (re-use, attempted
impersonation, etc.) by attackers.
While the Token Binding Protocol [TBPROTO] defines a message format While the Token Binding Protocol [I-D.ietf-tokbind-protocol] defines
for establishing a Token Binding ID, it doesn't specify how this a message format for establishing a Token Binding ID, it does not
message is embedded in higher-level protocols. The purpose of this specify how this message is embedded in higher-level protocols. The
specification is to define how TokenBindingMessages are embedded in purpose of this specification is to define how TokenBindingMessages
HTTP (both versions 1.1 [RFC2616] and 2 [I-D.ietf-httpbis-http2]). are embedded in HTTP (both versions 1.1 [RFC7230] and 2 [RFC7540]).
Note that TokenBindingMessages are only defined if the underlying Note that TokenBindingMessages are only defined if the underlying
transport uses TLS. This means that Token Binding over HTTP is only transport uses TLS. This means that Token Binding over HTTP is only
defined when the HTTP protocol is layered on top of TLS (commonly defined when the HTTP protocol is layered on top of TLS (commonly
referred to as HTTPS). referred to as HTTPS).
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 in HTTP requests. The HTTP header value is a a special HTTP header field in HTTP requests. The HTTP header field
TokenBindingMessage. value is a base64url-encoded TokenBindingMessage.
TokenBindingMessages allow clients to establish multiple Token TokenBindingMessages allow clients 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 in the TokenBindingMessage. By default, a client will
establish a _provided_ Token Binding ID with the server, indicating a establish a _provided_ Token Binding ID with the server, indicating a
Token Binding ID that the client will persistently use with the Token Binding ID that the client will persistently use with the
server. Under certain conditions, the client can also include a server. Under certain conditions, the client can also include a
_referred_ Token Binding ID in the TokenBindingMessage, indicating a _referred_ Token Binding ID in the TokenBindingMessage, indicating a
Token Binding ID that the client is using with a _different_ server Token Binding ID that the client is using with a _different_ server
than the one that the TokenBindingMessage is sent to. This is useful than the one that the TokenBindingMessage is sent to. This is useful
in federation scenarios. in federation 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", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. The Sec-Token-Binding Header 2. The Sec-Token-Binding 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 The Token Binding Protocol [TBPROTO]), with HTTP/1.1 or HTTP/2 (see [I-D.ietf-tokbind-protocol] and
clients MUST include the Sec-Token-Binding header in their HTTP [I-D.ietf-tokbind-negotiation]), clients MUST include the Sec-Token-
requests. The ABNF of the Sec-Token-Binding header is: Binding header field in their HTTP requests. The ABNF of the Sec-
Token-Binding header field is (in [RFC7230] style, see also [RFC7231]
Section 8.3):
Sec-Token-Binding = "Sec-Token-Binding" ":" [CFWS] EncodedTokenBindingMessage Sec-Token-Binding = EncodedTokenBindingMessage
The EncodedTokenBindingMessage is a web-safe Base64-encoding of the The header field name is "Sec-Token-Binding", and
TokenBindingMessage as defined in the TokenBindingProtocol [TBPROTO]. EncodedTokenBindingMessage is a base64url encoding (see [RFC4648]
Section 5) of the TokenBindingMessage as defined in
[I-D.ietf-tokbind-protocol].
The TokenBindingMessage MUST contain a TokenBinding with For example:
TokenBindingType provided_token_binding, which MUST be signed with
the Token Binding key used by the client for connections between
itself and the server that the HTTP request is sent to (clients use
different Token Binding keys for different servers). The Token
Binding ID established by this TokenBinding is called a _Provided
Token Binding ID_
In HTTP/2, the client SHOULD use Header Compression Sec-Token-Binding: <base64url-encoded TokenBindingMessage>
[I-D.ietf-httpbis-header-compression] to avoid the overhead of
repeating the same header in subsequent HTTP requests.
3. Federation Use Cases The TokenBindingMessage MUST contain one TokenBinding structure with
TokenBindingType of provided_token_binding, which MUST be signed with
the Token Binding private key used by the client for connections
between itself and the server that the HTTP request is sent to
(clients use different Token Binding keys for different servers, see
Section 2.1 below). The Token Binding ID established by this
TokenBinding is called a _Provided Token Binding ID_.
3.1. Introduction The TokenBindingMessage MAY also contain one TokenBinding structure
with TokenBindingType of referred_token_binding, as specified in
Section 4.3. In addition to the latter, or rather than the latter,
the TokenBindingMessage MAY contain other TokenBinding structures.
This is use case-specific, and such use cases are outside the scope
of this specification.
In HTTP/2, the client SHOULD use Header Compression [RFC7541] to
avoid the overhead of repeating the same header field in subsequent
HTTP requests.
2.1. HTTPS Token Binding Key Pair Scoping
HTTPS is used in conjunction with various application protocols, and
application contexts, in various ways. For example, general purpose
Web browsing is one such HTTP-based application context. Within the
latter context, HTTP cookies [RFC6265] are typically utilized for
state management, including client authentication. A related, though
distinct, example of other HTTP-based application contexts is where
OAuth tokens [RFC6749] are utilized to manage authorization for
third-party application access to resources. The token scoping rules
of these two examples can differ: the scoping rules for cookies are
concisely specified in [RFC6265], whereas OAuth is a framework and
defines various token types with various scopings, some of which are
determined by the encompassing application.
The Token Binding key pair scoping for those key pairs generated in
the context of the first-party and federation use cases defined in
this specification (below), and to be used for binding HTTP cookies
MUST be at the granularity of "effective top-level domain (public
suffix) + 1" (eTLD+1), i.e., at the same granularity at which cookies
can be set (see [RFC6265]). Key pairs used to bind other application
tokens, such as OAuth tokens, SHOULD adhere to the above eTLD+1
scoping requirement for those tokens being employed in first-party or
federation scenarios as described below, e.g., OAuth refresh tokens
or Open ID Connect "ID Tokens". See also Section 6.1, below.
Scoping rules for other HTTP-based application contexts are outside
the scope of this specification.
3. First-party Use Cases
In a first-party use case, an 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 later time, e.g., in order to
authenticate. Binding the security token to the TLS connection
between client and server protects the security token from misuse
since the server can detect if the security token is replayed
inappropriately, e.g., over other TLS connections.
See [I-D.ietf-tokbind-protocol] Section 6 for general guidance
regarding binding of security tokens and their subsequent validation.
4. Federation Use Cases
4.1. Introduction
For privacy reasons, clients use different private keys to establish For privacy reasons, clients use different private keys to establish
Provided Token Binding IDs with different servers. As a result, a Provided Token Binding IDs with different servers. As a result, a
server cannot bind a security token (such as an OAuth token or an server cannot bind a security token (such as an OAuth token or an
OpenID Connect identity token) to a TLS connection that the client OpenID Connect identity token) to a TLS connection that the client
has with a different server. This is, however, a common requirement has with a different server. This is, however, a common requirement
in federation scenarios: For example, an Identity Provider may wish in federation scenarios: For example, an Identity Provider may wish
to issue an identity token to a client and cryptographically bind to issue an identity token to a client and cryptographically bind
that token to the TLS connection between the client and a Relying that token to the TLS connection between the client and a Relying
Party. 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) gives the client permission to reveal the Consumer_ in this document) signals to the client that it should
Provided Token Binding ID that is used between the client and itself, reveal the Provided Token Binding ID that is used between the client
to another server (called the _Token Provider_ in this document). and itself, to another server (called the _Token Provider_ in this
Also common across the mechanisms is how the Token Binding ID is document). Also common across the mechanisms is how the Token
revealed to the Token Provider: The client uses the Token Binding Binding ID is revealed to the Token Provider: The client uses the
Protocol [TBPROTO], and includes a TokenBinding structure in the Sec- Token Binding Protocol [I-D.ietf-tokbind-protocol], and includes a
Token-Binding HTTP header defined above. What differs between the TokenBinding structure in the Sec-Token-Binding HTTP header field
various mechanisms is _how_ the Token Consumer grants the permission defined above. What differs between the various mechanisms is _how_
to reveal the Token Binding ID to the Token Provider. Below we the Token Consumer signals to the client that it should reveal the
specify one such mechanism, which is suitable for redirect-based Token Binding ID to the Token Provider. Below we specify one such
interactions between Token Consumers and Token Providers. mechanism, which is suitable for redirect-based interactions between
Token Consumers and Token Providers.
3.2. Overview 4.2. 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 (where the identity token is called "ID Token") and OpenID Connect (where the identity token is called "ID Token") and
SAML (where the identity token is a SAML assertion). SAML (where 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 in the identity token with the Token compare the Token Binding ID in the identity token with the Token
Binding ID of the TLS connection between it an the client. Binding ID of the TLS connection between it 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
be described as follows: be described as follows:
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.
skipping to change at page 5, line 45 skipping to change at page 7, line 7
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 public key that the client include in the token the Token-Binding public key that the client
uses when communicating with the Token Consumer, thus _binding_ uses when communicating with the Token Consumer, thus _binding_
the token to client's Token-Binding keypair. The client proves the token to client's Token-Binding keypair. The client proves
possession of the private key when communicating with the Token possession of the private key when communicating with the Token
Consumer through the Token Binding Protocol [TBPROTO], and reveals Consumer through the Token Binding Protocol
the corresponding public key of this keypair as part of the Token [I-D.ietf-tokbind-protocol], and reveals the corresponding public
Binding ID. Comparing the public key from the token with the key of this keypair as part of the Token Binding ID. Comparing
public key from the Token Binding ID allows the Token Consumer to the public key from the token with the public key from the Token
verify that the token was sent to it by the legitimate client. Binding ID allows the Token Consumer to verify that the token was
sent to it by the legitimate client.
o To allow the Token Provider to include the Token-Binding public o To allow the Token Provider to include the Token-Binding public
key in the token, the Token Binding ID (between client and Token key in the token, the Token Binding ID (between client and Token
Consumer) must therefore be communicated to the Token Provider Consumer) must therefore be communicated to the Token Provider
along with the token request. Communicating a Token Binding ID along with the token request. Communicating a Token Binding ID
involves proving possession of a private key and is described in involves proving possession of a private key and is described in
the Token Binding Protocol [TBPROTO]. the Token Binding Protocol [I-D.ietf-tokbind-protocol].
The client will perform this last operation (proving possession of a The client will perform this last operation (proving possession of a
private key that corresponds to a Token Binding ID between the client private key that corresponds to a Token Binding ID between the client
and the Token Consumer while delivering the token request to the and the Token Consumer while delivering the token request to the
Token Provider) only if the Token Consumer permits the client to do Token Provider) only if the Token Consumer requests the client to do
so. so.
Below, we specify how Token Consumers can grant this permission. Below, we specify how Token Consumers can signal this request in
during redirect-based federation protocols. redirect-based federation protocols. Note that this assumes that the
federated sign-on flow starts at the Token Consumer, or at the very
least include a redirect from Token Consumer to Token Provider. It
is outside the scope of this document to specify similar mechanisms
for flows that do not include such redirects.
3.3. HTTP Redirects 4.3. 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 a Include- means to deliver the token request, it SHOULD include a Include-
Referer-Token-Binding-ID HTTP response header in its HTTP response. Referred-Token-Binding-ID HTTP response header field in its HTTP
The ABNF of the Include-Referer-Token-Binding-ID header is: response. The ABNF of the Include-Referred-Token-Binding-ID header
is (in [RFC7230] style, see also [RFC7231] Section 8.3):
Include-Referer-Token-Binding-ID = "Include-Referer-Token-Binding-ID" ":" Include-Referred-Token-Binding-ID = "true"
[CFWS] %x74.72.75.65 ; "true", case-sensitive
Including this response header signals to the client that it should Where the header field name is "Include-Referred-Token-Binding-ID",
reveal, to the Token Provider, the Token Binding ID used between and the field-value of "true" is case-insensitive. For example:
itself and the Token Consumer. In the absence of this response
header, the client will not disclose any information about the Token
Binding used between the client and the Token Consumer to the Token
Provider.
When a client receives this header, it should take the TokenBindingID Include-Referred-Token-Binding-ID: true
of the provided TokenBinding from the referrer and create a referred
TokenBinding with it to include in the TokenBindingMessage on the
redirect request. In other words, the Token Binding message in the
redirect request to the Token Provider includes one provided binding
and one referred binding, the latter constructed from the binding
between the client and the Token Consumer.
If the Include-Referer-Token-Binding-ID header is received in Including this response header field signals to the client that it
response to a request that did not include the Token-Binding header, should reveal, to the Token Provider, the Token Binding ID used
the client MUST ignore the Include-Referer-Token-Binding-ID header. between itself and the Token Consumer. In the absence of this
response header field, the client will not disclose any information
about the Token Binding used between the client and the Token
Consumer to the Token Provider.
This header has only meaning if the HTTP status code is 301, 302, As illustrated in Section 4.5, when a client receives this header
303, 307 or 308, and MUST be ignored by the client for any other field, it should take the TokenBindingID of the provided TokenBinding
from the referrer and create a referred TokenBinding with it to
include in the TokenBindingMessage on the redirect request. In other
words, the Token Binding message in the redirect request to the Token
Provider now includes one provided binding and one referred binding,
the latter constructed from the binding between the client and the
Token Consumer. Note that that the referred token binding is sent
only on the request resulting from the redirect and not on any
subsequent requests to the Token Provider
If the Include-Referred-Token-Binding-ID header field is received in
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 301,
302, 303, 307 or 308, and MUST be ignored by the client for any other
status codes. If the client supports the Token Binding Protocol, and status codes. If the client supports the Token Binding Protocol, and
has negotiated the Token Binding Protocol with both the Token has negotiated the Token Binding Protocol with both the Token
Consumer and the Token Provider, it already sends the following Consumer and the Token Provider, it already sends the Sec-Token-
header to the Token Provider with each HTTP request (see above): Binding header field to the Token Provider with each HTTP request
(see above).
Sec-Token-Binding: EncodedTokenBindingMessage
The TokenBindingMessage SHOULD contain a TokenBinding with The TokenBindingMessage SHOULD contain a TokenBinding with
TokenBindingType referred_token_binding. If included, this TokenBindingType referred_token_binding. If included, this
TokenBinding MUST be signed with the Token Binding key used by the TokenBinding MUST be signed with the Token Binding key used by the
client for connections between itself and the Token Consumer (more client for connections between itself and the Token Consumer (more
specifically, the web origin that issued the Include-Referer-Token- specifically, the web origin that issued the Include-Referred-Token-
Binding-ID response header). The Token Binding ID established by Binding-ID response header field). The Token Binding ID established
this TokenBinding is called a _Referred Token Binding ID_. by this TokenBinding 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
TokenBindingType provided_token_binding, which MUST be signed with TokenBindingType provided_token_binding, which MUST be signed with
the Token Binding key used by the client for connections between the Token Binding key used by the client for connections between
itself and the Token Privider (more specifically, the web origin that itself and the Token Provider (more specifically, the web origin that
the token request sent to). the token request is being sent to).
3.4. Negotiated Key Parameters If for some deployment-specific reason the initial Token Provider
("TP1") needs to redirect the client to another Token Provider
("TP2"), rather than directly back to the Token Consumer, it can be
accomodated using the header fields defined in this specification in
the following fashion ("the redirect-chain approach"):
The Token Binding Protocol [TBPROTO] allows the server and client to Initially, the client is redirected to TP1 by the Token Consumer
negotiate a signature algorithm used in the TokenBindingMessage. It ("TC"), as described above. Upon receiving the client's request,
is possible that the Token Binding ID used between the client and the containing a TokenBindingMessage which contains both provided and
Token Consumer, and the Token Binding ID used between the client and referred TokenBindings (for TP1 and TC, respectively), TP1
Token Provider, use different signature algorithms. The client MUST responds to the client with a redirect response containing the
use the signature algorithm negotiated with the Token Consumer in the Include-Referred-Token-Binding-ID header field and directing the
referred_token_binding TokenBinding of the TokenBindingMessage, even client to send a request to TP2. This causes the client to follow
if that signature algorithm is different from the one negotiated with the same pattern and send a request containing a
the origin that the header is sent to. TokenBindingMessage which contains both provided and referred
TokenBindings (for TP2 and TP1, respectively) to TP2. Note that
this pattern can continue to further Token Providers. In this
case, TP2 issues a security token, bound to the client's
TokenBinding with TP1, and sends a redirect response to the client
pointing to TP1. TP1 in turn constructs a security token for the
Token Consumer, bound to the TC's referred TokenBinding which had
been conveyed earlier, and sends a redirect response pointing to
the TC, containing the bound security token, to the client.
Token Providers SHOULD support all the SignatureAndHashAlgorithms The above is intended as only a non-normative example. Details are
specified in the Token Binding Protocol [TBPROTO]. If a token specific to deployment contexts. Other approaches are possible, but
provider does not support the SignatureAndHashAlgorithm specified in are outside the scope of this specification.
the referred_token_binding TokenBinding in the TokenBindingMessage,
it MUST issue an unbound token.
3.5. Federation Example 4.4. Negotiated Key Parameters
The TLS Extension for Token Binding Protocol Negotiation
[I-D.ietf-tokbind-negotiation] allows the server and client to
negotiate the parameters (signature algorithm, length) of the Token
Binding key. It is possible that the Token Binding ID used between
the client and the Token Consumer, and the Token Binding ID used
between the client and Token Provider, use different key parameters.
The client MUST use the key parameters negotiated with the Token
Consumer in the referred_token_binding TokenBinding of the
TokenBindingMessage, even if those key parameters are different from
the ones negotiated with the origin that the header field is sent to.
Token Providers SHOULD support all the Token Binding key parameters
specified in the [I-D.ietf-tokbind-negotiation]. If a token provider
does not support the key parameters specified in the
referred_token_binding TokenBinding in the TokenBindingMessage, it
MUST issue an unbound token.
4.5. 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 SSO
Profile (no artifact, no callbacks), featuring binding of, e.g., a Profile (no artifact, no callbacks), featuring binding of, e.g., a
TLS Token Binding ID into an OpenID Connect "ID Token". 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 | | {EKMn}Ksm: | EKM for server "n", signed by private key of TBID |
skipping to change at page 9, line 6 skipping to change at page 11, line 6
| 0. Client interacts w/TC | | | 0. Client interacts w/TC | |
| over HTTPS, establishes Ks1 & 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 |
| HTTP response header field of: | | HTTP response header field of: |
| Include-Referer-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 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) |
skipping to change at page 10, line 5 skipping to change at page 12, line 5
| 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 are set SHOULD contain TBID1 | | that are set SHOULD contain TBID1 |
|<------------------------------| | |<------------------------------| |
| | | | | |
| | | | | |
4. Security Considerations 5. Security Considerations
4.1. Security Token Replay 5.1. 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 Token Consumer, thereby impersonating
legitimate users and gaining access to protected resources. Bound legitimate users and gaining access to protected resources. Bound
tokens can still be replayed by malware present in the client. In tokens can still be replayed by malware present in the client. In
order to export the token to another machine and successfully replay order to export the token to another machine and successfully replay
it, the attacker also needs to export the corresponding private key. it, the attacker also needs to export the corresponding private key.
The Token Binding private key is therefore a high-value asset and The Token Binding private key is therefore a high-value asset and
MUST be strongly protected, ideally by generating it in a hardware MUST be strongly protected, ideally by generating it in a hardware
security module that prevents key export. security module that prevents key export.
4.2. Triple Handshake Vulnerability in TLS 5.2. Triple Handshake Vulnerability in TLS 1.2 and Older TLS Versions
The Token Binding protocol relies on the exported key material (EKM) The Token Binding protocol relies on the exported key material (EKM)
value [RFC5705] to associate a TLS connection with a TLS Token value [RFC5705] to associate a TLS connection with a TLS Token
Binding. The triple handshake attack [TRIPLE-HS] is a known TLS Binding. The triple handshake attack [TRIPLE-HS] is a known
protocol vulnerability allowing the attacker to synchronize keying vulnerability in TLS 1.2 and older TLS versions, allowing the
manterial between TLS connections. The attacker can then attacker to synchronize keying material between TLS connections. The
successfully replay bound tokens. For this reason, the Token Binding attacker can then successfully replay bound tokens. For this reason,
protocol MUST NOT be negotiated unless the Extended Master Secret TLS the Token Binding protocol MUST NOT be negotiated with these TLS
extension [I-D.ietf-tls-session-hash] has also been negotiated. versions, unless the Extended Master Secret [RFC7627] and
Renegotiation Indication [RFC5746] TLS extensions have also been
negotiated.
4.3. Sensitivity of the Sec-Token-Binding Header 5.3. 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, 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 private Token Binding key must be kept For example, the client's private Token Binding key must be kept
secret by the client. If the private key is not secret, then another secret by the client. If the private key is not secret, then another
actor in the system could create a valid Token Binding header, actor in the system could create a valid Token Binding header field,
impersonating the client. This can render the main purpose of the impersonating the client. This can render the main purpose of the
protocol - to bind bearer tokens to certain clients - moot: Consider, protocol - to bind bearer tokens to certain clients - moot: Consider,
for example, an attacker who obtained (perhaps through a network for example, an attacker who obtained (perhaps through a network
intrusion) an authentication cookie that a client uses with a certain intrusion) an authentication cookie that a client uses with a certain
server. Consider further that the server bound that cookie to the server. Consider further that the server bound that cookie to the
client's Token Binding ID precisely to thwart cookie theft. If the client's Token Binding ID precisely to thwart misuse of the cookie.
attacker were to come into possession of the client's private key, he If the attacker were to come into possession of the client's private
could then establish a TLS connection with the server and craft a key, he could then establish a TLS connection with the server and
Sec-Token-Binding header that matches the binding present in the craft a Sec-Token-Binding header field that matches the binding
cookie, thus successfully authenticating as the client, and gaining present in the cookie, thus successfully authenticating as the
access to the client's data at the server. The Token Binding client, and gaining access to the client's data at the server. The
protocol, in this case, didn't successfully bind the cookie to the Token Binding protocol, in this case, did not successfully bind the
client. 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: A client shouldn't be tricked into sending a Sec-Token- header field: A client should not be tricked into sending a Sec-
Binding header to a server that contains Token Binding messages about Token-Binding header field to a server that contains Token Binding
key pairs that the client doesn't control. Consider an attacker A messages about key pairs that the client does not control. Consider
that somehow has knowledge of the exported keying material (EKM) for an attacker A that somehow has knowledge of the exported keying
a TLS connection between a client C and a server S. (While that is material (EKM) for a TLS connection between a client C and a server
somewhat unlikely, it's also not entirely out of the question, since S. (While that is somewhat unlikely, it is also not entirely out of
the client might not treat the EKM as a secret - after all, a pre- the question, since the client might not treat the EKM as a secret -
image-resistant hash function has been applied to the TLS master after all, a pre-image-resistant hash function has been applied to
secret, making it impossible for someone knowing the EKM to recover the TLS master secret, making it impossible for someone knowing the
the TLS master secret. Such considerations might lead some clients EKM to recover the TLS master secret. Such considerations might lead
to not treat the EKM as a secret.) Such an attacker A could craft a some clients to not treat the EKM as a secret.) Such an attacker A
Sec-Token-Binding header with A's key pair over C's EKM. If the could craft a Sec-Token-Binding header field with A's key pair over
attacker could now trick C to send such a header to S, it would C's EKM. If the attacker could now trick C to send such a header
appear to S as if C controls a certain key pair when in fact it field to S, it would appear to S as if C controls a certain key pair
doesn't (the attacker A controls the 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 If A has a pre-existing relationship with S (perhaps has an account
on S), it now appears to the server S as if A is connecting to it, 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 doesn't simply use even though it is really C. (If the server S does not simply use
Token Binding keys to identify clients, but also uses bound Token Binding keys 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, A tricked C
into logging into A's account on S. This could lead to a loss of into logging into A's account on S. This could lead to a loss of
privacy for C, since A presumably has some other way to also access privacy for C, since A presumably has some other way to also access
the account, and can thus indirectly observe A's behavior (for the account, and can thus indirectly observe A's behavior (for
example, if S has a feature that lets account holders see their example, if S has a feature that lets account holders see their
activity history on S). 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. One origin should not be able to set the Sec-Token-Binding header field. One origin should not be able to set the Sec-Token-
header (through a DOM API or otherwise) that the User Agent uses with Binding header field (through a DOM API or otherwise) that the User
another origin. Agent uses with another origin. Employing the "Sec-" header field
prefix helps to meet this requirement by denoting the header field
name to be a "forbidden header name", see [fetch-spec].
4.4. Securing Federated Sign-On Protocols 5.4. Securing Federated Sign-On Protocols
As explained above, in a federated sign-in scenario a client will As explained above, in a federated sign-in scenario a client will
prove possession of two different key pairs to a Token Provider: One prove possession of two different key pairs to a Token Provider: One
key pair is the "provided" Token Binding key pair (which the client key pair is the "provided" Token Binding key pair (which the client
normally uses with the Token Provider), and the other is the normally uses with the Token Provider), and the other is the
"referred" Token Binding key pair (which the client normally uses "referred" Token Binding key pair (which the client normally uses
with the Token Consumer). The Token Provider is expected to issue a with the Token Consumer). The Token Provider is expected to issue a
token that is bound to the referred Token Binding key. token that is bound to the referred Token Binding key.
Both proofs (that of the provided Token Binding key and that of the Both proofs (that of the provided Token Binding key and that of the
referred Token Binding key) are necessary. To show this, consider referred Token Binding key) are necessary. To show this, consider
the following scenario: 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 key. that is bound to the client's Token Binding key.
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 hasn't middle) authenticated session with the Token Consumer, but has not
done so yet (in other words, we're about to run the federated done so yet (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 client and Token Consumer or between Client and Token Provider (or
both). 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 man-
in-the-middle can intercept and modify any message sent by the client in-the-middle can intercept and modify any message sent by the client
to the Token Provider, and any message sent by the Token Provider to to the Token Provider, and any message sent by the Token Provider to
the client. (This means, among other things, that the man-in-the- the client. (This means, among other things, that the man-in-the-
middle controls the Javascript running at the client in the origin of middle controls the Javascript running at the client in the origin of
the Token Provider.) It is not, however, in possession of the the Token Provider.) It is not, however, in possession of the
client's Token Binding key. Therefore, it can either choose to client's Token Binding key. Therefore, it can either choose to
replace the Token Binding key in requests from the client to the replace the Token Binding key in requests from the client to the
Token Provider, and create a Sec-Token-Binding header that matches Token Provider, and create a Sec-Token-Binding header field that
the TLS connection between the man-in-the-middle and the Token matches the TLS connection between the man-in-the-middle and the
Provider; or it can choose to leave the Sec-Token-Binding header Token Provider; or it can choose to leave the Sec-Token-Binding
unchanged. If it chooses the latter, the signature in the Token header field unchanged. If it chooses the latter, the signature in
Binding message (created by the original client on the exported the Token Binding message (created by the original client on the
keying material (EKM) for the connection between client and man-in- exported keying material (EKM) for the connection between client and
the-middle) will not match the EKM between man-in-the-middle and the man-in-the-middle) will not match the EKM between man-in-the-middle
Token Provider. If it chooses the former (and creates its own and the Token Provider. If it chooses the former (and creates its
signature, with its own Token Binding key, over the EKM for the own signature, with its own Token Binding key, over the EKM for the
connection between man-in-the-middle and Token Provider), then the connection between man-in-the-middle and Token Provider), then the
Token Binding message will match the connection between man-in-the- Token Binding message will match the connection between man-in-the-
middle and Token Provider, but the Token Binding key in the message middle and Token Provider, but the Token Binding key in the message
will not match the Token Binding key that the client's authentication will not match the Token Binding key that the client's authentication
token is bound to. Either way, the man-in-the-middle is detected by token is bound to. Either way, the man-in-the-middle is detected by
the Token Provider, but only if the proof of key possession of the the Token Provider, but only if the proof of key possession of the
provided Token Binding key is required in the protocol (as we do provided Token Binding key is required in the protocol (as we do
above). 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 client and
skipping to change at page 13, line 20 skipping to change at page 15, line 23
the man-in-the-middle controls the redirect URL, and can tamper with the man-in-the-middle controls the redirect URL, and can tamper with
any redirect URL issued by the Token Consumer (as well as with any any redirect URL issued by the Token Consumer (as well as with any
Javascript running in the origin of the Token Consumer). The goal of Javascript running in the origin of the Token Consumer). The goal of
the man-in-the-middle is to trick the Token Issuer to issue a token the man-in-the-middle is to trick the Token Issuer to issue a token
bound to _its_ Token Binding key, not to the Token Binding key of the bound to _its_ Token Binding key, not to the Token Binding key of the
legitimate client. To thwart this goal of the man-in-the-middle, the legitimate client. To thwart this goal of the man-in-the-middle, the
client's referred Token Binding key must be communicated to the Token client's referred Token Binding key must be communicated to the Token
Producer in a manner that can not be affected by the man-in-the- Producer in a manner that can not be affected by the man-in-the-
middle (who, as we recall, can modify redirect URLs and Javascript at middle (who, as we recall, can modify redirect URLs and Javascript at
the client). Including the referred Token Binding message in the the client). Including the referred Token Binding message in the
Sec-Token-Binding header (as opposed to, say, including the referred Sec-Token-Binding header field (as opposed to, say, including the
Token Binding key in an application-level message as part of the referred Token Binding key in an application-level message as part of
redirect URL) is one way to assure that the man-in-the-middle between the redirect URL) is one way to assure that the man-in-the-middle
client and Token Consumer cannot affect the communication of the between client and Token Consumer cannot affect the communication of
referred Token Binding key to the Token Provider. the referred Token Binding key to the Token Provider.
Therefore, the Sec-Token-Binding header in the federated sign-on use Therefore, the Sec-Token-Binding header field in the federated sign-
case contains both, a proof of possession of the provided Token on use case contains both, a proof of possession of the provided
Binding key, as well as a proof of possession of the referred Token Token Binding key, as well as a proof of possession of the referred
Binding key. Token Binding key.
5. Privacy Considerations 6. Privacy Considerations
5.1. Scoping of Token Binding Keys 6.1. Scoping of Token Binding Keys
Clients must use different Token Binding keys 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. When Token Binding is used over HTTPS, this key different servers. However, the scoping of the Token Binding key
scoping should in particular happen at the granularity of "effective pairs to servers varies according to the scoping rules of the
top-level domain (public suffix) + 1", i.e., at the same granularity application protocol ([I-D.ietf-tokbind-protocol] section 4.1).
at which cookies can be set.
The reason for this is that 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 sub-domain of
public suffixes, and clients therefore should use the same Token effective top-level domains, and clients therefore should use the
Binding key across such subdomains. This will ensure that any server same Token Binding key across such subdomains. This will ensure that
capable of receiving the cookie will see the same Token Binding ID any server capable of receiving the cookie will see the same Token
from the client, and thus be able to verify the token binding of the Binding ID from the client, and thus be able to verify the token
cookie. binding of the cookie. See Section 2.1, above.
5.2. Life Time of Token Binding Keys 6.2. Life Time of Token Binding Keys
Token Binding keys don't have an expiration time. This means that Token Binding keys do not have an expiration time. This means that
they can potentially be used by a server to track a user across an they can potentially be used by a server to track a user across 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 keys (similar to the interface for discarding Token Binding keys (similar to the
affordances provided to delete cookies). affordances provided to delete 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 should also discarded after the session is over, the user agent should also
discard Token Binding keys from such modes after the session is over. discard Token Binding keys 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 life time of Token Binding keys as they have over cookies or over life time of Token Binding keys as they have over cookies or
other potential tracking mechanisms. other potential tracking mechanisms.
6. References 7. IANA Considerations
6.1. Normative References Below are the Internet Assigned Numbers Authority (IANA) Permanent
Message Header Field registration information per [RFC3864].
[I-D.ietf-httpbis-header-compression] Header field name: Sec-Token-Binding
Peon, R. and H. Ruellan, "HPACK - Header Compression for Applicable protocol: HTTP
HTTP/2", draft-ietf-httpbis-header-compression-12 (work in Status: standard
progress), February 2015. 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
[[TODO: possibly add further considerations wrt the behavior of the
above header fields, per <https://tools.ietf.org/html/
rfc7231#section-8.3>]]
8. Acknowledgements
This document incorporates comments and suggestions offered by Eric
Rescorla, Gabriel Montenegro, Martin Thomson, Vinod Anupam, Bill Cox,
Nick Harper, Brian Campbell and others.
9. References
9.1. Normative References
[fetch-spec]
WhatWG, "Fetch", Living Standard ,
<https://fetch.spec.whatwg.org/>.
[I-D.ietf-tokbind-negotiation]
Popov, A., Nystrom, M., Balfanz, D., and A. Langley,
"Transport Layer Security (TLS) Extension for Token
Binding Protocol Negotiation", draft-ietf-tokbind-
negotiation-02 (work in progress), January 2016.
[I-D.ietf-tokbind-protocol]
Popov, A., Nystrom, M., Balfanz, D., Langley, A., and J.
Hodges, "The Token Binding Protocol Version 1.0", draft-
ietf-tokbind-protocol-06 (work in progress), May 2016.
[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,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Procedures for Message Header Fields", BCP 90, RFC 3864,
Transfer Protocol -- HTTP/1.1", RFC 2616, DOI 10.17487/RFC3864, September 2004,
DOI 10.17487/RFC2616, June 1999, <http://www.rfc-editor.org/info/rfc3864>.
<http://www.rfc-editor.org/info/rfc2616>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<http://www.rfc-editor.org/info/rfc4648>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport [RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705, Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <http://www.rfc-editor.org/info/rfc5705>. March 2010, <http://www.rfc-editor.org/info/rfc5705>.
[TBPROTO] Popov, A., "The Token Binding Protocol Version 1.0", 2014. [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011,
<http://www.rfc-editor.org/info/rfc6265>.
6.2. Informative References [RFC7230] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Message Syntax and Routing",
RFC 7230, DOI 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.
[I-D.ietf-httpbis-http2] [RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Belshe, M., Peon, R., and M. Thomson, "Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
Protocol version 2", draft-ietf-httpbis-http2-17 (work in DOI 10.17487/RFC7231, June 2014,
progress), February 2015. <http://www.rfc-editor.org/info/rfc7231>.
[I-D.ietf-tls-session-hash] [RFC7541] Peon, R. and H. Ruellan, "HPACK: Header Compression for
Bhargavan, K., Delignat-Lavaud, A., Pironti, A., Langley, HTTP/2", RFC 7541, DOI 10.17487/RFC7541, May 2015,
A., and M. Ray, "Transport Layer Security (TLS) Session <http://www.rfc-editor.org/info/rfc7541>.
Hash and Extended Master Secret Extension", draft-ietf-
tls-session-hash-06 (work in progress), July 2015. 9.2. Informative References
[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,
<http://www.rfc-editor.org/info/rfc5746>.
[RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
[RFC6750] Jones, M. and D. Hardt, "The OAuth 2.0 Authorization
Framework: Bearer Token Usage", RFC 6750,
DOI 10.17487/RFC6750, October 2012,
<http://www.rfc-editor.org/info/rfc6750>.
[RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext
Transfer Protocol Version 2 (HTTP/2)", RFC 7540,
DOI 10.17487/RFC7540, May 2015,
<http://www.rfc-editor.org/info/rfc7540>.
[RFC7627] Bhargavan, K., Ed., Delignat-Lavaud, A., Pironti, A.,
Langley, A., and M. Ray, "Transport Layer Security (TLS)
Session Hash and Extended Master Secret Extension",
RFC 7627, DOI 10.17487/RFC7627, September 2015,
<http://www.rfc-editor.org/info/rfc7627>.
[TRIPLE-HS] [TRIPLE-HS]
Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti, Bhargavan, K., Delignat-Lavaud, A., Fournet, C., Pironti,
A., and P. Strub, "Triple Handshakes and Cookie Cutters: A., and P. Strub, "Triple Handshakes and Cookie Cutters:
Breaking and Fixing Authentication over TLS. IEEE Breaking and Fixing Authentication over TLS. IEEE
Symposium on Security and Privacy", 2014. Symposium on Security and Privacy", 2014.
Authors' Addresses Authors' Addresses
Andrei Popov Andrei Popov
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