draft-ietf-rtcweb-security-arch-10.txt   draft-ietf-rtcweb-security-arch-11.txt 
RTCWEB E. Rescorla RTCWEB E. Rescorla
Internet-Draft RTFM, Inc. Internet-Draft RTFM, Inc.
Intended status: Standards Track July 4, 2014 Intended status: Standards Track March 7, 2015
Expires: January 5, 2015 Expires: September 8, 2015
WebRTC Security Architecture WebRTC Security Architecture
draft-ietf-rtcweb-security-arch-10 draft-ietf-rtcweb-security-arch-11
Abstract Abstract
The Real-Time Communications on the Web (RTCWEB) working group is The Real-Time Communications on the Web (RTCWEB) working group is
tasked with standardizing protocols for enabling real-time tasked with standardizing protocols for enabling real-time
communications within user-agents using web technologies (commonly communications within user-agents using web technologies (commonly
called "WebRTC"). This document defines the security architecture called "WebRTC"). This document defines the security architecture
for WebRTC. for WebRTC.
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 January 5, 2015. This Internet-Draft will expire on September 8, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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modifications of such material outside the IETF Standards Process. modifications of such material outside the IETF Standards Process.
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than English. than English.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Trust Model . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Trust Model . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.1. Authenticated Entities . . . . . . . . . . . . . . . . . . 6 3.1. Authenticated Entities . . . . . . . . . . . . . . . . . 5
3.2. Unauthenticated Entities . . . . . . . . . . . . . . . . . 6 3.2. Unauthenticated Entities . . . . . . . . . . . . . . . . 6
4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.1. Initial Signaling . . . . . . . . . . . . . . . . . . . . 9 4.1. Initial Signaling . . . . . . . . . . . . . . . . . . . . 8
4.2. Media Consent Verification . . . . . . . . . . . . . . . . 11 4.2. Media Consent Verification . . . . . . . . . . . . . . . 10
4.3. DTLS Handshake . . . . . . . . . . . . . . . . . . . . . . 12 4.3. DTLS Handshake . . . . . . . . . . . . . . . . . . . . . 11
4.4. Communications and Consent Freshness . . . . . . . . . . . 12 4.4. Communications and Consent Freshness . . . . . . . . . . 11
5. Detailed Technical Description . . . . . . . . . . . . . . . . 13 5. Detailed Technical Description . . . . . . . . . . . . . . . 12
5.1. Origin and Web Security Issues . . . . . . . . . . . . . . 13 5.1. Origin and Web Security Issues . . . . . . . . . . . . . 12
5.2. Device Permissions Model . . . . . . . . . . . . . . . . . 13 5.2. Device Permissions Model . . . . . . . . . . . . . . . . 12
5.3. Communications Consent . . . . . . . . . . . . . . . . . . 15 5.3. Communications Consent . . . . . . . . . . . . . . . . . 15
5.4. IP Location Privacy . . . . . . . . . . . . . . . . . . . 16 5.4. IP Location Privacy . . . . . . . . . . . . . . . . . . . 15
5.5. Communications Security . . . . . . . . . . . . . . . . . 17 5.5. Communications Security . . . . . . . . . . . . . . . . . 16
5.6. Web-Based Peer Authentication . . . . . . . . . . . . . . 18 5.6. Web-Based Peer Authentication . . . . . . . . . . . . . . 18
5.6.1. Trust Relationships: IdPs, APs, and RPs . . . . . . . 19 5.6.1. Trust Relationships: IdPs, APs, and RPs . . . . . . . 19
5.6.2. Overview of Operation . . . . . . . . . . . . . . . . 21 5.6.2. Overview of Operation . . . . . . . . . . . . . . . . 20
5.6.3. Items for Standardization . . . . . . . . . . . . . . 22 5.6.3. Items for Standardization . . . . . . . . . . . . . . 22
5.6.4. Binding Identity Assertions to JSEP Offer/Answer 5.6.4. Binding Identity Assertions to JSEP Offer/Answer
Transactions . . . . . . . . . . . . . . . . . . . . . 22 Transactions . . . . . . . . . . . . . . . . . . . . 22
5.6.4.1. Input to Assertion Generation Process . . . . . . 22 5.6.4.1. Carrying Identity Assertions . . . . . . . . . . 23
5.6.4.2. Carrying Identity Assertions . . . . . . . . . . . 23 5.6.4.2. a=identity Attribute . . . . . . . . . . . . . . 23
5.6.4.3. a=identity Attribute . . . . . . . . . . . . . . . 24 5.6.5. Determining the IdP URI . . . . . . . . . . . . . . . 24
5.6.5. IdP Interaction Details . . . . . . . . . . . . . . . 24 5.6.5.1. Authenticating Party . . . . . . . . . . . . . . 25
5.6.5.1. General Message Structure . . . . . . . . . . . . 24 5.6.5.2. Relying Party . . . . . . . . . . . . . . . . . . 25
5.6.5.2. Errors . . . . . . . . . . . . . . . . . . . . . . 25 5.6.6. Requesting Assertions . . . . . . . . . . . . . . . . 25
5.6.5.3. IdP Proxy Setup . . . . . . . . . . . . . . . . . 26 5.6.7. Managing User Login . . . . . . . . . . . . . . . . . 27
5.6.5.4. Verifying Assertions . . . . . . . . . . . . . . . 30 5.7. Verifying Assertions . . . . . . . . . . . . . . . . . . 27
6. Security Considerations . . . . . . . . . . . . . . . . . . . 31 5.7.1. Identity Formats . . . . . . . . . . . . . . . . . . 28
6.1. Communications Security . . . . . . . . . . . . . . . . . 31 6. Security Considerations . . . . . . . . . . . . . . . . . . . 28
6.2. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 32 6.1. Communications Security . . . . . . . . . . . . . . . . . 29
6.3. Denial of Service . . . . . . . . . . . . . . . . . . . . 33 6.2. Privacy . . . . . . . . . . . . . . . . . . . . . . . . . 30
6.4. IdP Authentication Mechanism . . . . . . . . . . . . . . . 34 6.3. Denial of Service . . . . . . . . . . . . . . . . . . . . 30
6.4.1. PeerConnection Origin Check . . . . . . . . . . . . . 34 6.4. IdP Authentication Mechanism . . . . . . . . . . . . . . 31
6.4.2. IdP Well-known URI . . . . . . . . . . . . . . . . . . 35 6.4.1. PeerConnection Origin Check . . . . . . . . . . . . . 32
6.4.3. Privacy of IdP-generated identities and the 6.4.2. IdP Well-known URI . . . . . . . . . . . . . . . . . 32
hosting site . . . . . . . . . . . . . . . . . . . . . 35 6.4.3. Privacy of IdP-generated identities and the hosting
6.4.4. Security of Third-Party IdPs . . . . . . . . . . . . . 36 site . . . . . . . . . . . . . . . . . . . . . . . . 32
6.4.5. Web Security Feature Interactions . . . . . . . . . . 36 6.4.4. Security of Third-Party IdPs . . . . . . . . . . . . 33
6.4.5.1. Popup Blocking . . . . . . . . . . . . . . . . . . 36 6.4.5. Web Security Feature Interactions . . . . . . . . . . 33
6.4.5.2. Third Party Cookies . . . . . . . . . . . . . . . 36 6.4.5.1. Popup Blocking . . . . . . . . . . . . . . . . . 33
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 6.4.5.2. Third Party Cookies . . . . . . . . . . . . . . . 33
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 37 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 34
9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 34
9.1. Changes since -06 . . . . . . . . . . . . . . . . . . . . 37 9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
9.2. Changes since -05 . . . . . . . . . . . . . . . . . . . . 37 9.1. Changes since -10 . . . . . . . . . . . . . . . . . . . . 34
9.3. Changes since -03 . . . . . . . . . . . . . . . . . . . . 37 9.2. Changes since -06 . . . . . . . . . . . . . . . . . . . . 34
9.4. Changes since -03 . . . . . . . . . . . . . . . . . . . . 38 9.3. Changes since -05 . . . . . . . . . . . . . . . . . . . . 35
9.5. Changes since -02 . . . . . . . . . . . . . . . . . . . . 38 9.4. Changes since -03 . . . . . . . . . . . . . . . . . . . . 35
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 38 9.5. Changes since -03 . . . . . . . . . . . . . . . . . . . . 35
10.1. Normative References . . . . . . . . . . . . . . . . . . . 38 9.6. Changes since -02 . . . . . . . . . . . . . . . . . . . . 35
10.2. Informative References . . . . . . . . . . . . . . . . . . 40 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 36
Appendix A. Example IdP Bindings to Specific Protocols . . . . . 41 10.1. Normative References . . . . . . . . . . . . . . . . . . 36
A.1. BrowserID . . . . . . . . . . . . . . . . . . . . . . . . 41 10.2. Informative References . . . . . . . . . . . . . . . . . 38
A.2. OAuth . . . . . . . . . . . . . . . . . . . . . . . . . . 44 Appendix A. Example IdP Bindings to Specific Protocols . . . . . 38
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 45 A.1. BrowserID . . . . . . . . . . . . . . . . . . . . . . . . 39
A.2. OAuth . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 43
1. Introduction 1. Introduction
The Real-Time Communications on the Web (WebRTC) working group is The Real-Time Communications on the Web (WebRTC) working group is
tasked with standardizing protocols for real-time communications tasked with standardizing protocols for real-time communications
between Web browsers. The major use cases for WebRTC technology are between Web browsers. The major use cases for WebRTC technology are
real-time audio and/or video calls, Web conferencing, and direct data real-time audio and/or video calls, Web conferencing, and direct data
transfer. Unlike most conventional real-time systems, (e.g., SIP- transfer. Unlike most conventional real-time systems, (e.g., SIP-
based[RFC3261] soft phones) WebRTC communications are directly based[RFC3261] soft phones) WebRTC communications are directly
controlled by some Web server, via a JavaScript (JS) API as shown in controlled by some Web server, via a JavaScript (JS) API as shown in
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browser (or transitively by some property the browser verifies). browser (or transitively by some property the browser verifies).
Conversely, if the browser is compromised, then no security Conversely, if the browser is compromised, then no security
guarantees are possible. Note that there are cases (e.g., Internet guarantees are possible. Note that there are cases (e.g., Internet
kiosks) where the user can't really trust the browser that much. In kiosks) where the user can't really trust the browser that much. In
these cases, the level of security provided is limited by how much these cases, the level of security provided is limited by how much
they trust the browser. they trust the browser.
Optimally, we would not rely on trust in any entities other than the Optimally, we would not rely on trust in any entities other than the
browser. However, this is unfortunately not possible if we wish to browser. However, this is unfortunately not possible if we wish to
have a functional system. Other network elements fall into two have a functional system. Other network elements fall into two
categories: those which can be authenticated by the browser and thus categories: those which can be authenticated by the browser and thus
are partly trusted--though to the minimum extent necessary--and those are partly trusted--though to the minimum extent necessary--and those
which cannot be authenticated and thus are untrusted. which cannot be authenticated and thus are untrusted.
3.1. Authenticated Entities 3.1. Authenticated Entities
There are two major classes of authenticated entities in the system: There are two major classes of authenticated entities in the system:
o Calling services: Web sites whose origin we can verify (optimally o Calling services: Web sites whose origin we can verify (optimally
via HTTPS, but in some cases because we are on a topologically via HTTPS, but in some cases because we are on a topologically
restricted network, such as behind a firewall, and can infer restricted network, such as behind a firewall, and can infer
authentication from firewall behavior). authentication from firewall behavior).
o Other users: WebRTC peers whose origin we can verify
o Other users: WebRTC peers whose origin we can verify
cryptographically (optimally via DTLS-SRTP). cryptographically (optimally via DTLS-SRTP).
Note that merely being authenticated does not make these entities Note that merely being authenticated does not make these entities
trusted. For instance, just because we can verify that trusted. For instance, just because we can verify that
https://www.evil.org/ is owned by Dr. Evil does not mean that we can https://www.evil.org/ is owned by Dr. Evil does not mean that we can
trust Dr. Evil to access our camera and microphone. However, it trust Dr. Evil to access our camera and microphone. However, it
gives the user an opportunity to determine whether he wishes to trust gives the user an opportunity to determine whether he wishes to trust
Dr. Evil or not; after all, if he desires to contact Dr. Evil Dr. Evil or not; after all, if he desires to contact Dr. Evil
(perhaps to arrange for ransom payment), it's safe to temporarily (perhaps to arrange for ransom payment), it's safe to temporarily
give him access to the camera and microphone for the purpose of the give him access to the camera and microphone for the purpose of the
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3.2. Unauthenticated Entities 3.2. Unauthenticated Entities
Other than the above entities, we are not generally able to identify Other than the above entities, we are not generally able to identify
other network elements, thus we cannot trust them. This does not other network elements, thus we cannot trust them. This does not
mean that it is not possible to have any interaction with them, but mean that it is not possible to have any interaction with them, but
it means that we must assume that they will behave maliciously and it means that we must assume that they will behave maliciously and
design a system which is secure even if they do so. design a system which is secure even if they do so.
4. Overview 4. Overview
This section describes a typical RTCWeb session and shows how the This section describes a typical WebRTC session and shows how the
various security elements interact and what guarantees are provided various security elements interact and what guarantees are provided
to the user. The example in this section is a "best case" scenario to the user. The example in this section is a "best case" scenario
in which we provide the maximal amount of user authentication and in which we provide the maximal amount of user authentication and
media privacy with the minimal level of trust in the calling service. media privacy with the minimal level of trust in the calling service.
Simpler versions with lower levels of security are also possible and Simpler versions with lower levels of security are also possible and
are noted in the text where applicable. It's also important to are noted in the text where applicable. It's also important to
recognize the tension between security (or performance) and privacy. recognize the tension between security (or performance) and privacy.
The example shown here is aimed towards settings where we are more The example shown here is aimed towards settings where we are more
concerned about secure calling than about privacy, but as we shall concerned about secure calling than about privacy, but as we shall
see, there are settings where one might wish to make different see, there are settings where one might wish to make different
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4.1. Initial Signaling 4.1. Initial Signaling
For simplicity, assume the topology in Figure 3. Alice and Bob are For simplicity, assume the topology in Figure 3. Alice and Bob are
both users of a common calling service; they both have approved the both users of a common calling service; they both have approved the
calling service to make calls (we defer the discussion of device calling service to make calls (we defer the discussion of device
access permissions till later). They are both connected to the access permissions till later). They are both connected to the
calling service via HTTPS and so know the origin with some level of calling service via HTTPS and so know the origin with some level of
confidence. They also have accounts with some identity provider. confidence. They also have accounts with some identity provider.
This sort of identity service is becoming increasingly common in the This sort of identity service is becoming increasingly common in the
Web environment in technologies such (BrowserID, Federated Google Web environment (with technologies such as BrowserID, Federated
Login, Facebook Connect, OAuth, OpenID, WebFinger), and is often Google Login, Facebook Connect, OAuth, OpenID, WebFinger), and is
provided as a side effect service of a user's ordinary accounts with often provided as a side effect service of a user's ordinary accounts
some service. In this example, we show Alice and Bob using a with some service. In this example, we show Alice and Bob using a
separate identity service, though the identity service may be the separate identity service, though the identity service may be the
same entity as the calling service or there may be no identity same entity as the calling service or there may be no identity
service at all. service at all.
Alice is logged onto the calling service and decides to call Bob. She Alice is logged onto the calling service and decides to call Bob.
can see from the calling service that he is online and the calling She can see from the calling service that he is online and the
service presents a JS UI in the form of a button next to Bob's name calling service presents a JS UI in the form of a button next to
which says "Call". Alice clicks the button, which initiates a JS Bob's name which says "Call". Alice clicks the button, which
callback that instantiates a PeerConnection object. This does not initiates a JS callback that instantiates a PeerConnection object.
require a security check: JS from any origin is allowed to get this This does not require a security check: JS from any origin is allowed
far. to get this far.
Once the PeerConnection is created, the calling service JS needs to Once the PeerConnection is created, the calling service JS needs to
set up some media. Because this is an audio/video call, it creates a set up some media. Because this is an audio/video call, it creates a
MediaStream with two MediaStreamTracks, one connected to an audio MediaStream with two MediaStreamTracks, one connected to an audio
input and one connected to a video input. At this point the first input and one connected to a video input. At this point the first
security check is required: untrusted origins are not allowed to security check is required: untrusted origins are not allowed to
access the camera and microphone, so the browser prompts Alice for access the camera and microphone, so the browser prompts Alice for
permission. permission.
In the current W3C API, once some streams have been added, Alice's In the current W3C API, once some streams have been added, Alice's
browser + JS generates a signaling message [I-D.ietf-rtcweb-jsep] browser + JS generates a signaling message [I-D.ietf-rtcweb-jsep]
containing: containing:
o Media channel information o Media channel information
o Interactive Connectivity Establishment (ICE) [RFC5245] candidates o Interactive Connectivity Establishment (ICE) [RFC5245] candidates
o A fingerprint attribute binding the communication to a key pair o A fingerprint attribute binding the communication to a key pair
[RFC5763]. Note that this key may simply be ephemerally generated [RFC5763]. Note that this key may simply be ephemerally generated
for this call or specific to this domain, and Alice may have a for this call or specific to this domain, and Alice may have a
large number of such keys. large number of such keys.
Prior to sending out the signaling message, the PeerConnection code Prior to sending out the signaling message, the PeerConnection code
contacts the identity service and obtains an assertion binding contacts the identity service and obtains an assertion binding
Alice's identity to her fingerprint. The exact details depend on the Alice's identity to her fingerprint. The exact details depend on the
identity service (though as discussed in Section 5.6 PeerConnection identity service (though as discussed in Section 5.6 PeerConnection
can be agnostic to them), but for now it's easiest to think of as a can be agnostic to them), but for now it's easiest to think of as a
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Prior to sending out the signaling message, the PeerConnection code Prior to sending out the signaling message, the PeerConnection code
contacts the identity service and obtains an assertion binding contacts the identity service and obtains an assertion binding
Alice's identity to her fingerprint. The exact details depend on the Alice's identity to her fingerprint. The exact details depend on the
identity service (though as discussed in Section 5.6 PeerConnection identity service (though as discussed in Section 5.6 PeerConnection
can be agnostic to them), but for now it's easiest to think of as a can be agnostic to them), but for now it's easiest to think of as a
BrowserID assertion. The assertion may bind other information to the BrowserID assertion. The assertion may bind other information to the
identity besides the fingerprint, but at minimum it needs to bind the identity besides the fingerprint, but at minimum it needs to bind the
fingerprint. fingerprint.
This message is sent to the signaling server, e.g., by XMLHttpRequest This message is sent to the signaling server, e.g., by XMLHttpRequest
[XmlHttpRequest] or by WebSockets [RFC6455]. preferably over TLS [XmlHttpRequest] or by WebSockets [RFC6455]. preferably over TLS
[RFC5246]. The signaling server processes the message from Alice's [RFC5246]. The signaling server processes the message from Alice's
browser, determines that this is a call to Bob and sends a signaling browser, determines that this is a call to Bob and sends a signaling
message to Bob's browser (again, the format is currently undefined). message to Bob's browser (again, the format is currently undefined).
The JS on Bob's browser processes it, and alerts Bob to the incoming The JS on Bob's browser processes it, and alerts Bob to the incoming
call and to Alice's identity. In this case, Alice has provided an call and to Alice's identity. In this case, Alice has provided an
identity assertion and so Bob's browser contacts Alice's identity identity assertion and so Bob's browser contacts Alice's identity
provider (again, this is done in a generic way so the browser has no provider (again, this is done in a generic way so the browser has no
specific knowledge of the IdP) to verify the assertion. This allows specific knowledge of the IdP) to verify the assertion. This allows
the browser to display a trusted element in the browser chrome the browser to display a trusted element in the browser chrome
indicating that a call is coming in from Alice. If Alice is in Bob's indicating that a call is coming in from Alice. If Alice is in Bob's
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in-the-middle attack on their traffic. Even if they do not use an in-the-middle attack on their traffic. Even if they do not use an
IdP, as long as they have minimal trust in the signaling service not IdP, as long as they have minimal trust in the signaling service not
to perform a man-in-the-middle attack, they know that their to perform a man-in-the-middle attack, they know that their
communications are secure against the signaling service as well communications are secure against the signaling service as well
(i.e., that the signaling service cannot mount a passive attack on (i.e., that the signaling service cannot mount a passive attack on
the communications). the communications).
4.4. Communications and Consent Freshness 4.4. Communications and Consent Freshness
From a security perspective, everything from here on in is a little From a security perspective, everything from here on in is a little
anticlimactic: Alice and Bob exchange data protected by the keys anticlimactic: Alice and Bob exchange data protected by the keys
negotiated by DTLS. Because of the security guarantees discussed in negotiated by DTLS. Because of the security guarantees discussed in
the previous sections, they know that the communications are the previous sections, they know that the communications are
encrypted and authenticated. encrypted and authenticated.
The one remaining security property we need to establish is "consent The one remaining security property we need to establish is "consent
freshness", i.e., allowing Alice to verify that Bob is still prepared freshness", i.e., allowing Alice to verify that Bob is still prepared
to receive her communications so that Alice does not continue to send to receive her communications so that Alice does not continue to send
large traffic volumes to entities which went abruptly offline. ICE large traffic volumes to entities which went abruptly offline. ICE
specifies periodic STUN keepalizes but only if media is not flowing. specifies periodic STUN keepalives but only if media is not flowing.
Because the consent issue is more difficult here, we require RTCWeb Because the consent issue is more difficult here, we require WebRTC
implementations to periodically send keepalives. As described in implementations to periodically send keepalives. As described in
Section 5.3, these keepalives MUST be based on the consent freshness Section 5.3, these keepalives MUST be based on the consent freshness
mechanism specified in [I-D.muthu-behave-consent-freshness]. If a mechanism specified in [I-D.muthu-behave-consent-freshness]. If a
keepalive fails and no new ICE channels can be established, then the keepalive fails and no new ICE channels can be established, then the
session is terminated. session is terminated.
5. Detailed Technical Description 5. Detailed Technical Description
5.1. Origin and Web Security Issues 5.1. Origin and Web Security Issues
The basic unit of permissions for WebRTC is the origin [RFC6454]. The basic unit of permissions for WebRTC is the origin [RFC6454].
Because the security of the origin depends on being able to Because the security of the origin depends on being able to
authenticate content from that origin, the origin can only be authenticate content from that origin, the origin can only be
securely established if data is transferred over HTTPS [RFC2818]. securely established if data is transferred over HTTPS [RFC2818].
Thus, clients MUST treat HTTP and HTTPS origins as different Thus, clients MUST treat HTTP and HTTPS origins as different
permissions domains. [Note: this follows directly from the origin permissions domains. [Note: this follows directly from the origin
security model and is stated here merely for clarity.] security model and is stated here merely for clarity.]
Many web browsers currently forbid by default any active mixed Many web browsers currently forbid by default any active mixed
content on HTTPS pages. That is, when JavaScript is loaded from an content on HTTPS pages. That is, when JavaScript is loaded from an
HTTP origin onto an HTTPS page, an error is displayed and the HTTP HTTP origin onto an HTTPS page, an error is displayed and the HTTP
content is not executed unless the user overrides the error. Any content is not executed unless the user overrides the error. Any
browser which enforces such a policy will also not permit access to browser which enforces such a policy will also not permit access to
WebRTC functionality from mixed content pages (because they never WebRTC functionality from mixed content pages (because they never
display mixed content). Browsers which allow active mixed content display mixed content). Browsers which allow active mixed content
MUST nevertheless disable WebRTC functionality in mixed content MUST nevertheless disable WebRTC functionality in mixed content
skipping to change at page 14, line 47 skipping to change at page 14, line 4
and microphone are in use. This indication MUST NOT be and microphone are in use. This indication MUST NOT be
suppressable by the JS and MUST clearly indicate how to terminate suppressable by the JS and MUST clearly indicate how to terminate
device access, and provide a UI means to immediately stop camera/ device access, and provide a UI means to immediately stop camera/
microphone input without the JS being able to prevent it. microphone input without the JS being able to prevent it.
UI Requirement: If the UI indication of camera/microphone use are UI Requirement: If the UI indication of camera/microphone use are
displayed in the browser such that minimizing the browser window displayed in the browser such that minimizing the browser window
would hide the indication, or the JS creating an overlapping would hide the indication, or the JS creating an overlapping
window would hide the indication, then the browser SHOULD stop window would hide the indication, then the browser SHOULD stop
camera and microphone input when the indication is hidden. [Note: camera and microphone input when the indication is hidden. [Note:
this may not be necessary in systems that are non-windows-based this may not be necessary in systems that are non-windows-based
but that have good notifications support, such as phones.] but that have good notifications support, such as phones.]
[[OPEN ISSUE: This section does not have WG consensus. Because [[OPEN ISSUE: This section does not have WG consensus. Because
screen/application sharing presents a more significant risk than screen/application sharing presents a more significant risk than
camera and microphone access (see the discussion in camera and microphone access (see the discussion in
[I-D.ietf-rtcweb-security] S 4.1.1), we require a higher level of [I-D.ietf-rtcweb-security] S 4.1.1), we require a higher level of
user consent. user consent.
o Browsers MUST not permit permanent screen or application sharing o Browsers MUST not permit permanent screen or application sharing
permissions to be installed as a response to a JS request for permissions to be installed as a response to a JS request for
permissions. Instead, they must require some other user action permissions. Instead, they must require some other user action
such as a permissions setting or an application install experience such as a permissions setting or an application install experience
to grant permission to a site. to grant permission to a site.
skipping to change at page 15, line 26 skipping to change at page 14, line 34
o The browser MUST indicate any windows which are currently being o The browser MUST indicate any windows which are currently being
shared in some unambiguous way. Windows which are not visible shared in some unambiguous way. Windows which are not visible
MUST not be shared even if the application is being shared. If MUST not be shared even if the application is being shared. If
the screen is being shared, then that MUST be indicated. the screen is being shared, then that MUST be indicated.
-- END OF OPEN ISSUE]] -- END OF OPEN ISSUE]]
Clients MAY permit the formation of data channels without any direct Clients MAY permit the formation of data channels without any direct
user approval. Because sites can always tunnel data through the user approval. Because sites can always tunnel data through the
server, further restrictions on the data channel do not provide any server, further restrictions on the data channel do not provide any
additional security. (though see Section 5.3 for a related issue). additional security. (though see Section 5.3 for a related issue).
Implementations which support some form of direct user authentication Implementations which support some form of direct user authentication
SHOULD also provide a policy by which a user can authorize calls only SHOULD also provide a policy by which a user can authorize calls only
to specific communicating peers. Specifically, the implementation to specific communicating peers. Specifically, the implementation
SHOULD provide the following interfaces/controls: SHOULD provide the following interfaces/controls:
o Allow future calls to this verified user. o Allow future calls to this verified user.
o Allow future calls to any verified user who is in my system o Allow future calls to any verified user who is in my system
address book (this only works with address book integration, of address book (this only works with address book integration, of
course). course).
Implementations SHOULD also provide a different user interface Implementations SHOULD also provide a different user interface
indication when calls are in progress to users whose identities are indication when calls are in progress to users whose identities are
directly verifiable. Section 5.5 provides more on this. directly verifiable. Section 5.5 provides more on this.
5.3. Communications Consent 5.3. Communications Consent
skipping to change at page 16, line 8 skipping to change at page 15, line 19
MUST implement either full ICE or ICE-Lite [RFC5245]. MUST implement either full ICE or ICE-Lite [RFC5245].
Browser implementations MUST verify reachability via ICE prior to Browser implementations MUST verify reachability via ICE prior to
sending any non-ICE packets to a given destination. Implementations sending any non-ICE packets to a given destination. Implementations
MUST NOT provide the ICE transaction ID to JavaScript during the MUST NOT provide the ICE transaction ID to JavaScript during the
lifetime of the transaction (i.e., during the period when the ICE lifetime of the transaction (i.e., during the period when the ICE
stack would accept a new response for that transaction). The JS MUST stack would accept a new response for that transaction). The JS MUST
NOT be permitted to control the local ufrag and password, though it NOT be permitted to control the local ufrag and password, though it
of course knows it. of course knows it.
While continuing consent is required, that ICE [RFC5245]; Section 10 While continuing consent is required, the ICE [RFC5245]; Section 10
keepalives STUN Binding Indications are one-way and therefore not keepalives use STUN Binding Indications which are one-way and
sufficient. The current WG consensus is to use ICE Binding Requests therefore not sufficient. The current WG consensus is to use ICE
for continuing consent freshness. ICE already requires that Binding Requests for continuing consent freshness. ICE already
implementations respond to such requests, so this approach is requires that implementations respond to such requests, so this
maximally compatible. A separate document will profile the ICE approach is maximally compatible. A separate document will profile
timers to be used; see [I-D.muthu-behave-consent-freshness]. the ICE timers to be used; see [I-D.muthu-behave-consent-freshness].
5.4. IP Location Privacy 5.4. IP Location Privacy
A side effect of the default ICE behavior is that the peer learns A side effect of the default ICE behavior is that the peer learns
one's IP address, which leaks large amounts of location information. one's IP address, which leaks large amounts of location information.
This has negative privacy consequences in some circumstances. The This has negative privacy consequences in some circumstances. The
API requirements in this section are intended to mitigate this issue. API requirements in this section are intended to mitigate this issue.
Note that these requirements are NOT intended to protect the user's Note that these requirements are NOT intended to protect the user's
IP address from a malicious site. In general, the site will learn at IP address from a malicious site. In general, the site will learn at
least a user's server reflexive address from any HTTP transaction. least a user's server reflexive address from any HTTP transaction.
skipping to change at page 17, line 32 skipping to change at page 16, line 42
[I-D.ietf-tsvwg-sctp-dtls-encaps]. [I-D.ietf-tsvwg-sctp-dtls-encaps].
All media channels MUST be secured via SRTP. Media traffic MUST NOT All media channels MUST be secured via SRTP. Media traffic MUST NOT
be sent over plain (unencrypted) RTP; that is, implementations MUST be sent over plain (unencrypted) RTP; that is, implementations MUST
NOT negotiate cipher suites with NULL encryption modes. DTLS-SRTP NOT negotiate cipher suites with NULL encryption modes. DTLS-SRTP
MUST be offered for every media channel. WebRTC implementations MUST MUST be offered for every media channel. WebRTC implementations MUST
NOT offer SDES or select it if offered. NOT offer SDES or select it if offered.
All data channels MUST be secured via DTLS. All data channels MUST be secured via DTLS.
All implementations MUST implement both DTLS 1.2 and DTLS 1.0, with All implementations MUST implement DTLS 1.0, with the cipher suite
the cipher suites TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 and TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA and the DTLS-SRTP protection
TLS_DHE_RSA_WITH_AES_128_CBC_SHA and the DTLS-SRTP protection profile profile SRTP_AES128_CM_HMAC_SHA1_80. Implementations SHOULD
SRTP_AES128_CM_HMAC_SHA1_80. Implementations SHOULD favor cipher implement DTLS 1.2 with the TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256
suites which support PFS over non-PFS cipher suites and GCM over CBC cipher suite. Implementations SHOULD favor cipher suites which
cipher suites. [[OPEN ISSUE: Should we require ECDHE? Waiting for support PFS over non-PFS cipher suites and GCM over CBC cipher
TLS WG Consensus.]] suites. [[OPEN ISSUE: Should we require ECDSA? Waiting for WG
Consensus.]]
API Requirement: The API MUST provide a mechanism to indicate that a API Requirement: The API MUST provide a mechanism to indicate that a
fresh DTLS key pair is to be generated for a specific call. This fresh DTLS key pair is to be generated for a specific call. This
is intended to allow for unlinkability. Note that there are also is intended to allow for unlinkability. Note that there are also
settings where it is attractive to use the same keying material settings where it is attractive to use the same keying material
repeatedly, especially those with key continuity-based repeatedly, especially those with key continuity-based
authentication. Unless the user specifically configures an authentication. Unless the user specifically configures an
external key pair, different key pairs MUST be used for each external key pair, different key pairs MUST be used for each
origin. (This avoids creating a super-cookie.) origin. (This avoids creating a super-cookie.)
API Requirement: When DTLS-SRTP is used, the API MUST NOT permit the API Requirement: When DTLS-SRTP is used, the API MUST NOT permit the
JS to obtain the negotiated keying material. This requirement JS to obtain the negotiated keying material. This requirement
preserves the end-to-end security of the media. preserves the end-to-end security of the media.
UI Requirements: A user-oriented client MUST provide an UI Requirements: A user-oriented client MUST provide an "inspector"
"inspector" interface which allows the user to determine the interface which allows the user to determine the security
security characteristics of the media. characteristics of the media.
The following properties SHOULD be displayed "up-front" in the The following properties SHOULD be displayed "up-front" in the
browser chrome, i.e., without requiring the user to ask for them: browser chrome, i.e., without requiring the user to ask for them:
* A client MUST provide a user interface through which a user may * A client MUST provide a user interface through which a user may
determine the security characteristics for currently-displayed determine the security characteristics for currently-displayed
audio and video stream(s) audio and video stream(s)
* A client MUST provide a user interface through which a user may * A client MUST provide a user interface through which a user may
determine the security characteristics for transmissions of determine the security characteristics for transmissions of
their microphone audio and camera video. their microphone audio and camera video.
* The "security characteristics" MUST include an indication as to * The "security characteristics" MUST include an indication as to
whether the cryptographic keys were delivered out-of-band (from whether the cryptographic keys were delivered out-of-band (from
a server) or were generated as a result of a pairwise a server) or were generated as a result of a pairwise
negotiation. negotiation.
* If the far endpoint was directly verified, either via a third- * If the far endpoint was directly verified, either via a third-
party verifiable X.509 certificate or via a Web IdP mechanism party verifiable X.509 certificate or via a Web IdP mechanism
(see Section 5.6) the "security characteristics" MUST include (see Section 5.6) the "security characteristics" MUST include
the verified information. X.509 identities and Web IdP the verified information. X.509 identities and Web IdP
identities have similar semantics and should be displayed in a identities have similar semantics and should be displayed in a
similar way. similar way.
The following properties are more likely to require some "drill- The following properties are more likely to require some "drill-
down" from the user: down" from the user:
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party verifiable X.509 certificate or via a Web IdP mechanism party verifiable X.509 certificate or via a Web IdP mechanism
(see Section 5.6) the "security characteristics" MUST include (see Section 5.6) the "security characteristics" MUST include
the verified information. X.509 identities and Web IdP the verified information. X.509 identities and Web IdP
identities have similar semantics and should be displayed in a identities have similar semantics and should be displayed in a
similar way. similar way.
The following properties are more likely to require some "drill- The following properties are more likely to require some "drill-
down" from the user: down" from the user:
* The "security characteristics" MUST indicate the cryptographic * The "security characteristics" MUST indicate the cryptographic
algorithms in use (For example: "AES-CBC" or "Null Cipher".) algorithms in use (For example: "AES-CBC" or "Null Cipher".)
However, if Null ciphers are used, that MUST be presented to However, if Null ciphers are used, that MUST be presented to
the user at the top-level UI. the user at the top-level UI.
* The "security characteristics" MUST indicate whether PFS is * The "security characteristics" MUST indicate whether PFS is
provided. provided.
* The "security characteristics" MUST include some mechanism to * The "security characteristics" MUST include some mechanism to
allow an out-of-band verification of the peer, such as a allow an out-of-band verification of the peer, such as a
certificate fingerprint or an SAS. certificate fingerprint or an SAS.
5.6. Web-Based Peer Authentication 5.6. Web-Based Peer Authentication
In a number of cases, it is desirable for the endpoint (i.e., the In a number of cases, it is desirable for the endpoint (i.e., the
browser) to be able to directly identity the endpoint on the other browser) to be able to directly identify the endpoint on the other
side without trusting only the signaling service to which they are side without trusting the signaling service to which they are
connected. For instance, users may be making a call via a federated connected. For instance, users may be making a call via a federated
system where they wish to get direct authentication of the other system where they wish to get direct authentication of the other
side. Alternately, they may be making a call on a site which they side. Alternately, they may be making a call on a site which they
minimally trust (such as a poker site) but to someone who has an minimally trust (such as a poker site) but to someone who has an
identity on a site they do trust (such as a social network.) identity on a site they do trust (such as a social network.)
Recently, a number of Web-based identity technologies (OAuth, Recently, a number of Web-based identity technologies (OAuth,
BrowserID, Facebook Connect), etc. have been developed. While the BrowserID, Facebook Connect etc.) have been developed. While the
details vary, what these technologies share is that they have a Web- details vary, what these technologies share is that they have a Web-
based (i.e., HTTP/HTTPS) identity provider which attests to your based (i.e., HTTP/HTTPS) identity provider which attests to your
identity. For instance, if I have an account at example.org, I could identity. For instance, if I have an account at example.org, I could
use the example.org identity provider to prove to others that I was use the example.org identity provider to prove to others that I was
alice@example.org. The development of these technologies allows us alice@example.org. The development of these technologies allows us
to separate calling from identity provision: I could call you on to separate calling from identity provision: I could call you on
Poker Galaxy but identify myself as alice@example.org. Poker Galaxy but identify myself as alice@example.org.
Whatever the underlying technology, the general principle is that the Whatever the underlying technology, the general principle is that the
party which is being authenticated is NOT the signaling site but party which is being authenticated is NOT the signaling site but
rather the user (and their browser). Similarly, the relying party is rather the user (and their browser). Similarly, the relying party is
the browser and not the signaling site. Thus, the browser MUST the browser and not the signaling site. Thus, the browser MUST
securely generate the input to the IdP assertion process and MUST securely generate the input to the IdP assertion process and MUST
securely display the results of the verification process to the user securely display the results of the verification process to the user
in a way which cannot be imitated by the calling site. in a way which cannot be imitated by the calling site.
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Authenticating Party (AP): The entity which is trying to establish Authenticating Party (AP): The entity which is trying to establish
its identity. its identity.
Identity Provider (IdP): The entity which is vouching for the AP's Identity Provider (IdP): The entity which is vouching for the AP's
identity. identity.
Relying Party (RP): The entity which is trying to verify the AP's Relying Party (RP): The entity which is trying to verify the AP's
identity. identity.
The AP and the IdP have an account relationship of some kind: the AP The AP and the IdP have an account relationship of some kind: the AP
registers with the IdP and is able to subsequently authenticate registers with the IdP and is able to subsequently authenticate
directly to the IdP (e.g., with a password). This means that the directly to the IdP (e.g., with a password). This means that the
browser must somehow know which IdP(s) the user has an account browser must somehow know which IdP(s) the user has an account
relationship with. This can either be something that the user relationship with. This can either be something that the user
configures into the browser or that is configured at the calling site configures into the browser or that is configured at the calling site
and then provided to the PeerConnection by the Web application at the and then provided to the PeerConnection by the Web application at the
calling site. The use case for having this information configured calling site. The use case for having this information configured
into the browser is that the user may "log into" the browser to bind into the browser is that the user may "log into" the browser to bind
it to some identity. This is becoming common in new browsers. it to some identity. This is becoming common in new browsers.
However, it should also be possible for the IdP information to simply However, it should also be possible for the IdP information to simply
be provided by the calling application. be provided by the calling application.
At a high level there are two kinds of IdPs: At a high level there are two kinds of IdPs:
Authoritative: IdPs which have verifiable control of some section Authoritative: IdPs which have verifiable control of some section
of the identity space. For instance, in the realm of e-mail, the of the identity space. For instance, in the realm of e-mail, the
operator of "example.com" has complete control of the namespace operator of "example.com" has complete control of the namespace
ending in "@example.com". Thus, "alice@example.com" is whoever ending in "@example.com". Thus, "alice@example.com" is whoever
the operator says it is. Examples of systems with authoritative the operator says it is. Examples of systems with authoritative
identity providers include DNSSEC, RFC 4474, and Facebook Connect identity providers include DNSSEC, RFC 4474, and Facebook Connect
(Facebook identities only make sense within the context of the (Facebook identities only make sense within the context of the
Facebook system). Facebook system).
Third-Party: IdPs which don't have control of their section of the Third-Party: IdPs which don't have control of their section of the
identity space but instead verify user's identities via some identity space but instead verify user's identities via some
unspecified mechanism and then attest to it. Because the IdP unspecified mechanism and then attest to it. Because the IdP
doesn't actually control the namespace, RPs need to trust that the doesn't actually control the namespace, RPs need to trust that the
IdP is correctly verifying AP identities, and there can IdP is correctly verifying AP identities, and there can
potentially be multiple IdPs attesting to the same section of the potentially be multiple IdPs attesting to the same section of the
identity space. Probably the best-known example of a third-party identity space. Probably the best-known example of a third-party
identity provider is SSL certificates, where there are a large identity provider is SSL certificates, where there are a large
number of CAs all of whom can attest to any domain name. number of CAs all of whom can attest to any domain name.
If an AP is authenticating via an authoritative IdP, then the RP does If an AP is authenticating via an authoritative IdP, then the RP does
skipping to change at page 21, line 37 skipping to change at page 21, line 18
| +----------------------------------+ | | +----------------------------------+ |
| | https://calling-site.example.com | | | | https://calling-site.example.com | |
| | | | | | | |
| | Calling JS Code | | | | Calling JS Code | |
| | ^ | | | | ^ | |
| +---------------|------------------+ | | +---------------|------------------+ |
| | API Calls | | | API Calls |
| v | | v |
| PeerConnection | | PeerConnection |
| ^ | | ^ |
| | MessageChannel | | | API Calls |
| +-----------|-------------+ | +---------------+ | +-----------|-------------+ | +---------------+
| | v | | | | | | v | | | |
| | IdP Proxy |<-------->| Identity | | | IdP Proxy |<-------->| Identity |
| | | | | Provider | | | | | | Provider |
| | https://idp.example.org | | | | | | https://idp.example.org | | | |
| +-------------------------+ | +---------------+ | +-------------------------+ | +---------------+
| | | |
+--------------------------------------+ +--------------------------------------+
When the PeerConnection object wants to interact with the IdP, the When the PeerConnection object wants to interact with the IdP, the
skipping to change at page 21, line 49 skipping to change at page 21, line 30
| | v | | | | | | v | | | |
| | IdP Proxy |<-------->| Identity | | | IdP Proxy |<-------->| Identity |
| | | | | Provider | | | | | | Provider |
| | https://idp.example.org | | | | | | https://idp.example.org | | | |
| +-------------------------+ | +---------------+ | +-------------------------+ | +---------------+
| | | |
+--------------------------------------+ +--------------------------------------+
When the PeerConnection object wants to interact with the IdP, the When the PeerConnection object wants to interact with the IdP, the
sequence of events is as follows: sequence of events is as follows:
1. The browser (the PeerConnection component) instantiates an IdP 1. The browser (the PeerConnection component) instantiates an IdP
proxy with its source at the IdP. This allows the IdP to load proxy. This allows the IdP to load whatever JS is necessary into
whatever JS is necessary into the proxy, which runs in the IdP's the proxy. The resulting code runs in the IdP's security
security context. The browser uses a MessageChannel context.
[WebMessaging] to interact with the IdP proxy. 2. The IdP registers an object with the browser that conforms to the
2. Once the IdP is ready, the IdP proxy uses the MessageChannel to API defined in [webrtc-api].
notify the browser that it is ready.
3. The browser and IdP proxy communicate using the MessageChannel 3. The browser invokes methods on the object registered by the IdP
using a standardized message exchange to create or verify proxy to create or verify identity assertions.
identity assertions.
This approach allows us to decouple the browser from any particular This approach allows us to decouple the browser from any particular
identity provider; the browser need only know how to load the IdP's identity provider; the browser need only know how to load the IdP's
JavaScript--which is deterministic from the IdP's identity--and the JavaScript--the location of which is determined based on the IdP's
generic protocol for requesting and verifying assertions. The IdP identity--and to call the generic API for requesting and verifying
provides whatever logic is necessary to bridge the generic protocol identity assertions. The IdP provides whatever logic is necessary to
to the IdP's specific requirements. Thus, a single browser can bridge the generic protocol to the IdP's specific requirements.
support any number of identity protocols, including being forward Thus, a single browser can support any number of identity protocols,
compatible with IdPs which did not exist at the time the browser was including being forward compatible with IdPs which did not exist at
written. the time the browser was written.
5.6.3. Items for Standardization 5.6.3. Items for Standardization
In order to make this work, we must standardize the following items: There are two parts to this work:
o The precise information from the signaling message that must be o The precise information from the signaling message that must be
cryptographically bound to the user's identity and a mechanism for cryptographically bound to the user's identity and a mechanism for
carrying assertions in JSEP messages. Section 5.6.4 carrying assertions in JSEP messages. This is specified in
o The interface to the IdP. Section 5.6.5 specifies a specific Section 5.6.4.
protocol mechanism which allows the use of any identity protocol
without requiring specific further protocol support in the browser
o The JavaScript interfaces which the calling application can use to
specify the IdP to use to generate assertions and to discover what
assertions were received.
The first two items are defined in this document. The final one is o The interface to the IdP, which is defined in the companion W3C
defined in the companion W3C WebRTC API specification [webrtc-api]. WebRTC API specification [webrtc-api].
5.6.4. Binding Identity Assertions to JSEP Offer/Answer Transactions The WebRTC API specification also defines JavaScript interfaces that
the calling application can use to specify which IdP to use. That
API also provides access to the assertion-generation capability and
the status of the validation process.
5.6.4.1. Input to Assertion Generation Process 5.6.4. Binding Identity Assertions to JSEP Offer/Answer Transactions
An identity assertion binds the user's identity (as asserted by the An identity assertion binds the user's identity (as asserted by the
IdP) to the SDP offer/exchange transaction and specifically to the IdP) to the SDP offer/exchange transaction and specifically to the
media. In order to achieve this, the PeerConnection must provide the media. In order to achieve this, the PeerConnection must provide the
DTLS-SRTP fingerprint to be bound to the identity. This is provided DTLS-SRTP fingerprint to be bound to the identity. This is provided
as a JavaScript object (also known as a dictionary or hash) with a as a JavaScript object (also known as a dictionary or hash) with a
single "fingerprint" key, as shown below: single "fingerprint" key, as shown below:
{ {
"fingerprint": [ { "fingerprint": [ {
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"algorithm": "sha-1", "algorithm": "sha-1",
"digest": "74:E9:76:C8:19:...:F4:45:6B" "digest": "74:E9:76:C8:19:...:F4:45:6B"
} ] } ]
} }
The "fingerprint" value is an array of objects. Each object in the The "fingerprint" value is an array of objects. Each object in the
array contains "algorithm" and "digest" values, which correspond array contains "algorithm" and "digest" values, which correspond
directly to the algorithm and digest values in the "a=fingerprint" directly to the algorithm and digest values in the "a=fingerprint"
line of the SDP [RFC4572]. line of the SDP [RFC4572].
Note: this structure does not need to be interpreted by the IdP or
the IdP proxy. It is consumed solely by the RP's browser. The IdP
merely treats it as an opaque value to be attested to. Thus, new
parameters can be added to the assertion without modifying the IdP.
This object is encoded in a JSON [RFC4627] string for passing to the This object is encoded in a JSON [RFC4627] string for passing to the
IdP. IdP.
5.6.4.2. Carrying Identity Assertions This structure does not need to be interpreted by the IdP or the IdP
proxy. It is consumed solely by the RP's browser. The IdP merely
treats it as an opaque value to be attested to. Thus, new parameters
can be added to the assertion without modifying the IdP.
5.6.4.1. Carrying Identity Assertions
Once an IdP has generated an assertion, it is attached to the SDP Once an IdP has generated an assertion, it is attached to the SDP
message. This is done by adding a new a-line to the SDP, of the form message. This is done by adding a new identity attribute to the SDP.
a=identity. The sole contents of this value are a base-64 encoded The sole contents of this value are a base-64 encoded [RFC4648]
[RFC4648] identity assertion. For example: identity assertion. For example:
v=0 v=0
o=- 1181923068 1181923196 IN IP4 ua1.example.com o=- 1181923068 1181923196 IN IP4 ua1.example.com
s=example1 s=example1
c=IN IP4 ua1.example.com c=IN IP4 ua1.example.com
a=fingerprint:sha-1 \ a=fingerprint:sha-1 \
4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB 4A:AD:B9:B1:3F:82:18:3B:54:02:12:DF:3E:5D:49:6B:19:E5:7C:AB
a=identity:\ a=identity:\
eyJpZHAiOnsiZG9tYWluIjoiZXhhbXBsZS5vcmciLCJwcm90b2NvbCI6ImJvZ3Vz\ eyJpZHAiOnsiZG9tYWluIjoiZXhhbXBsZS5vcmciLCJwcm90b2NvbCI6ImJvZ3Vz\
In0sImFzc2VydGlvbiI6IntcImlkZW50aXR5XCI6XCJib2JAZXhhbXBsZS5vcmdc\ In0sImFzc2VydGlvbiI6IntcImlkZW50aXR5XCI6XCJib2JAZXhhbXBsZS5vcmdc\
IixcImNvbnRlbnRzXCI6XCJhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3l6XCIsXCJz\ IixcImNvbnRlbnRzXCI6XCJhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3l6XCIsXCJz\
aWduYXR1cmVcIjpcIjAxMDIwMzA0MDUwNlwifSJ9 aWduYXR1cmVcIjpcIjAxMDIwMzA0MDUwNlwifSJ9
a=... a=...
t=0 0 t=0 0
m=audio 6056 RTP/SAVP 0 m=audio 6056 RTP/SAVP 0
a=sendrecv a=sendrecv
... ...
Each identity attribute should be paired (and attests to) with an The identity attribute attests to all "a=fingerprint" attributes in
"a=fingerprint" attribute and therefore can exist either at the the session description. It is therefore a session-level attribute.
session or media level. Multiple identity attributes may appear at
either level, though it is RECOMMENDED that implementations not do
this, because it becomes very unclear what security claim that they
are making and the UI guidelines above become unclear. Browsers MAY
choose refuse to display any identity indicators in the face of
multiple identity attributes with different identities but SHOULD
process multiple attributes with the same identity as described
above.
Multiple "a=fingerprint" values can be used to offer alternative Multiple "a=fingerprint" values can be used to offer alternative
certificates for a peer. The "a=identity" attribute MUST include all certificates for a peer. The "a=identity" attribute MUST include all
fingerprint values that are included in "a=fingerprint" lines. This fingerprint values that are included in "a=fingerprint" lines.
ensures that the in-use certificate for a DTLS connection is in the
set of fingerprints returned from the IdP when verifying an
assertion. This MUST be enforced by an RP by ensuring that all
"a=fingerprint" attributes for a given media section are present in
the "VERIFY" response (see Section 5.6.5.4).
5.6.4.3. a=identity Attribute The RP browser MUST verify that the in-use certificate for a DTLS
connection is in the set of fingerprints returned from the IdP when
verifying an assertion.
5.6.4.2. a=identity Attribute
The identity attribute is session level only. It contains an The identity attribute is session level only. It contains an
identity assertion, encoded as a base-64 string [RFC4648]. identity assertion, encoded as a base-64 string [RFC4648].
The syntax of this SDP attribute is defined using Augmented BNF The syntax of this SDP attribute is defined using Augmented BNF
[RFC5234]: [RFC5234]:
identity-attribute = "identity:" identity-assertion identity-attribute = "identity:" identity-assertion
[ SP identity-extension [ SP identity-extension
*(";" [ SP ] identity-extension) ] *(";" [ SP ] identity-extension) ]
identity-assertion = base64 identity-assertion = base64
base64 = 1*(ALPHA / DIGIT / "+" / "/" / "=" ) base64 = 1*(ALPHA / DIGIT / "+" / "/" / "=" )
identity-extension = extension-att-name [ "=" extension-att-value ] identity-extension = extension-att-name [ "=" extension-att-value ]
extension-att-name = token extension-att-name = token
extension-att-value = 1*(%x01-09 / %x0b-0c / %x0e-3a / %x3c-ff) extension-att-value = 1*(%x01-09 / %x0b-0c / %x0e-3a / %x3c-ff)
; byte-string from [RFC4566] omitting ";" ; byte-string from [RFC4566] omitting ";"
No extensions are defined for this attribute. No extensions are defined for this attribute.
5.6.5. IdP Interaction Details The identity assertion is a JSON [RFC4627] encoded dictionary that
contains two values. The "assertion" attribute contains an opaque
5.6.5.1. General Message Structure string that is consumed by the IdP. The "idp" attribute is a
dictionary with one or two further values that identify the IdP, as
Messages between the PeerConnection object and the IdP proxy are described in Section 5.6.5.
JavaScript objects, shown in examples using JSON [RFC4627]. For
instance, the PeerConnection would request a signature with the
following "SIGN" message:
{
"type": "SIGN",
"id": "1",
"origin": "https://calling-site.example.com",
"message": "012345678abcdefghijkl"
}
All messages MUST contain a "type" field which indicates the general
meaning of the message.
All requests from the PeerConnection object MUST contain an "id"
field which MUST be unique within the scope of the interaction
between the browser and the IdP instance. Responses from the IdP
proxy MUST contain the same "id" in response, which allows the
PeerConnection to correlate requests and responses, in case there are
multiple requests/responses outstanding to the same proxy.
All requests from the PeerConnection object MUST contain an "origin"
field containing the origin of the JS which initiated the PC (i.e.,
the URL of the calling site). This origin value can be used by the
IdP to make access control decisions. For instance, an IdP might
only issue identity assertions for certain calling services in the
same way that some IdPs require that relying Web sites have an API
key before learning user identity.
Any message-specific data is carried in a "message" field. Depending
on the message type, this may either be a string or any JavaScript
object that can be conveyed in a message channel. This includes any
object that is able to be serialized to JSON.
5.6.5.2. Errors
If an error occurs, the IdP sends a message of type "ERROR". The
message MAY have an "error" field containing freeform text data which
containing additional information about what happened. For instance:
{
"type": "ERROR",
"id": "1",
"error": "Signature verification failed"
}
Figure 5: Example error
5.6.5.3. IdP Proxy Setup
In order to perform an identity transaction, the PeerConnection must
first create an IdP proxy. While the details of this are specified
in the W3C API document, from the perspective of this specification,
however, the relevant facts are:
o The JS runs in the IdP's security context with the base page
retrieved from the URL specified in Section 5.6.5.3.1.
o The usual browser sandbox isolation mechanisms MUST be enforced
with respect to the IdP proxy. The IdP cannot be provided with
escalated privileges.
o JS running in the IdP proxy MUST be able to send and receive
messages to the PeerConnection and the PC and IdP proxy are able
to verify the source and destination of these messages.
o The IdP proxy is unable to interact with the user. This includes
the creation of popup windows and dialogs.
Initially the IdP proxy is in an unready state; the IdP JS must be
loaded and there may be several round trips to the IdP server to load
and prepare necessary resources.
When the IdP proxy is ready to receive commands, it delivers a
"READY" message. As this message is unsolicited, it contains only
the "type":
{ "type":"READY" }
Once the PeerConnection object receives the ready message, it can
send commands to the IdP proxy.
5.6.5.3.1. Determining the IdP URI 5.6.5. Determining the IdP URI
In order to ensure that the IdP is under control of the domain owner In order to ensure that the IdP is under control of the domain owner
rather than someone who merely has an account on the domain owner's rather than someone who merely has an account on the domain owner's
server (e.g., in shared hosting scenarios), the IdP JavaScript is server (e.g., in shared hosting scenarios), the IdP JavaScript is
hosted at a deterministic location based on the IdP's domain name. hosted at a deterministic location based on the IdP's domain name.
Each IdP proxy instance is associated with two values: Each IdP proxy instance is associated with two values:
domain name: The IdP's domain name domain name: The IdP's domain name
protocol: The specific IdP protocol which the IdP is using. This is protocol: The specific IdP protocol which the IdP is using. This is
a completely opaque IdP-specific string, but allows an IdP to a completely opaque IdP-specific string, but allows an IdP to
implement two protocols in parallel. This value may be the empty implement two protocols in parallel. This value may be the empty
string. string. If no value for protocol is provided, a value of
"default" is used.
Each IdP MUST serve its initial entry page (i.e., the one loaded by Each IdP MUST serve its initial entry page (i.e., the one loaded by
the IdP proxy) from a well-known URI [RFC5785]. The well-known URI the IdP proxy) from a well-known URI [RFC5785]. The well-known URI
for an IdP proxy is formed from the following URI components: for an IdP proxy is formed from the following URI components:
1. The scheme, "https:". An IdP MUST be loaded using HTTPS 1. The scheme, "https:". An IdP MUST be loaded using HTTPS
[RFC2818]. [RFC2818].
2. The authority, which is the IdP domain name. The authority MAY 2. The authority, which is the IdP domain name. The authority MAY
contain a non-default port number. Any port number is removed contain a non-default port number. Any port number is removed
when determining if an asserted identity matches the name of the when determining if an asserted identity matches the name of the
IdP. The authority MUST NOT include a userinfo sub-component. IdP. The authority MUST NOT include a userinfo sub-component.
3. The path, starting with "/.well-known/idp-proxy/" and appended 3. The path, starting with "/.well-known/idp-proxy/" and appended
with the IdP protocol. Note that the separator characters '/' with the IdP protocol. Note that the separator characters '/'
(%2F) and '\' (%5C) MUST NOT be permitted in the protocol field, (%2F) and '\' (%5C) MUST NOT be permitted in the protocol field,
lest an attacker be able to direct requests outside of the lest an attacker be able to direct requests outside of the
controlled "/.well-known/" prefix. Query and fragment values MAY controlled "/.well-known/" prefix. Query and fragment values MAY
be used by including '?' or '#' characters. be used by including '?' or '#' characters.
For example, for the IdP "identity.example.com" and the protocol For example, for the IdP "identity.example.com" and the protocol
"example", the URL would be: "example", the URL would be:
https://example.com/.well-known/idp-proxy/example https://example.com/.well-known/idp-proxy/example
5.6.5.3.1.1. Authenticating Party The IdP MAY redirect requests to this URL, but they MUST retain the
"https" scheme. This changes the effective origin of the IdP, but
not the domain of the identities that the IdP is permitted to assert
and validate. I.e., the IdP is still regarded as authoritative for
the original domain.
5.6.5.1. Authenticating Party
How an AP determines the appropriate IdP domain is out of scope of How an AP determines the appropriate IdP domain is out of scope of
this specification. In general, however, the AP has some actual this specification. In general, however, the AP has some actual
account relationship with the IdP, as this identity is what the IdP account relationship with the IdP, as this identity is what the IdP
is attesting to. Thus, the AP somehow supplies the IdP information is attesting to. Thus, the AP somehow supplies the IdP information
to the browser. Some potential mechanisms include: to the browser. Some potential mechanisms include:
o Provided by the user directly. o Provided by the user directly.
o Selected from some set of IdPs known to the calling site. E.g., a o Selected from some set of IdPs known to the calling site. E.g., a
button that shows "Authenticate via Facebook Connect" button that shows "Authenticate via Facebook Connect"
5.6.5.3.1.2. Relying Party 5.6.5.2. Relying Party
Unlike the AP, the RP need not have any particular relationship with Unlike the AP, the RP need not have any particular relationship with
the IdP. Rather, it needs to be able to process whatever assertion the IdP. Rather, it needs to be able to process whatever assertion
is provided by the AP. As the assertion contains the IdP's identity, is provided by the AP. As the assertion contains the IdP's identity,
the URI can be constructed directly from the assertion, and thus the the URI can be constructed directly from the assertion, and thus the
RP can directly verify the technical validity of the assertion with RP can directly verify the technical validity of the assertion with
no user interaction. Authoritative assertions need only be no user interaction. Authoritative assertions need only be
verifiable. Third-party assertions also MUST be verified against verifiable. Third-party assertions also MUST be verified against
local policy, as described in Section 5.6.5.4.1. local policy, as described in Section 5.7.1.
5.6.5.3.2. Requesting Assertions 5.6.6. Requesting Assertions
In order to request an assertion, the PeerConnection sends a "SIGN" The input to identity assertion is the JSON-encoded object described
message. Aside from the mandatory fields, this message has a in Section 5.6.4 that contains the set of certificate fingerprints
"message" field containing a string. The string contains a JSON- the browser intends to use. This string is treated as opaque from
encoded object containing certificate fingerprints but are treated as the perspective of the IdP.
opaque from the perspective of the IdP.
An application can optionally provide a user identifier when The browser also identifies the origin that the PeerConnection is run
in, which allows the IdP to make decisions based on who is requesting
the assertion.
An application can optionally provide a user identifier hint when
specifying an IdP. This value is a hint that the IdP can use to specifying an IdP. This value is a hint that the IdP can use to
select amongst multiple identities, or to avoid providing assertions select amongst multiple identities, or to avoid providing assertions
for unwanted identities. The user identifier hint is passed to the for unwanted identities. The "username" is a string that has no
IdP in a "username" field alongside the "message". The "username" is meaning to any entity other than the IdP, it can contain any data the
a string that has no meaning to any entity other than the IdP, it can IdP needs in order to correctly generate an assertion.
contain any data the IdP needs in order to correctly generate an
assertion.
A successful response to a "SIGN" message contains a "message" field An identity assertion that is successfully provided by the IdP
which is a JavaScript dictionary consisting of two fields: consists of the following information:
idp: The domain name of an IdP and the protocol string. This MAY
identify a different IdP or protocol from the one that generated
the assertion.
idp: A dictionary containing the domain name of the provider and the
protocol string.
assertion: An opaque value containing the assertion itself. This is assertion: An opaque value containing the assertion itself. This is
only interpretable by the IdP or its proxy. only interpretable by the identified IdP or the IdP code running
in the client.
Figure 6 shows an example transaction, with the message "abcde..." Figure 5 shows an example assertion formatted as JSON. In this case,
(remember, the messages are opaque at this layer) being signed and the message has presumably been digitally signed/MACed in some way
bound to identity "ekr@example.org". In this case, the message has that the IdP can later verify it, but this is an implementation
presumably been digitally signed/MACed in some way that the IdP can detail and out of scope of this document. Line breaks are inserted
later verify it, but this is an implementation detail and out of solely for readability.
scope of this document. Line breaks are inserted solely for
readability.
PeerConnection -> IdP proxy: {
{ "idp":{
"type": "SIGN", "domain": "example.org",
"id": "1", "protocol": "bogus"
"origin": "https://calling-service.example.com/", },
"message": "abcdefghijklmnopqrstuvwyz", "assertion": "{\"identity\":\"bob@example.org\",
"username": "bob" \"contents\":\"abcdefghijklmnopqrstuvwyz\",
} \"signature\":\"010203040506\"}"
}
IdPProxy -> PeerConnection: Figure 5: Example assertion
{
"type": "SUCCESS",
"id": "1",
"message": {
"idp":{
"domain": "example.org",
"protocol": "bogus"
},
"assertion": "{\"identity\":\"bob@example.org\",
\"contents\":\"abcdefghijklmnopqrstuvwyz\",
\"signature\":\"010203040506\"}"
}
}
Figure 6: Example assertion request
The "message" structure is serialized into JSON, base64-encoded For use in signaling, the assertion is serialized into JSON,
[RFC4648], and placed in an "a=identity" attribute. base64-encoded [RFC4648], and used as the value of the "a=identity"
attribute.
5.6.5.3.3. Managing User Login 5.6.7. Managing User Login
In order to generate an identity assertion, the IdP needs proof of In order to generate an identity assertion, the IdP needs proof of
the user's identity. It is common practice to authenticate users the user's identity. It is common practice to authenticate users
(using passwords or multi-factor authentication), then use Cookies (using passwords or multi-factor authentication), then use Cookies
[RFC6265] or HTTP authentication [RFC2617] for subsequent exchanges. [RFC6265] or HTTP authentication [RFC2617] for subsequent exchanges.
The IdP proxy is able to access cookies, HTTP authentication or other The IdP proxy is able to access cookies, HTTP authentication or other
persistent session data because it operates in the security context persistent session data because it operates in the security context
of the IdP origin. Therefore, if a user is logged in, the IdP could of the IdP origin. Therefore, if a user is logged in, the IdP could
have all the information needed to generate an assertion. have all the information needed to generate an assertion.
An IdP proxy is unable to generate an assertion if the user is not An IdP proxy is unable to generate an assertion if the user is not
logged in, or the IdP wants to interact with the user to acquire more logged in, or the IdP wants to interact with the user to acquire more
information before generating the assertion. If the IdP wants to information before generating the assertion. If the IdP wants to
interact with the user before generating an assertion, the IdP proxy interact with the user before generating an assertion, the IdP proxy
can respond with a "LOGINNEEDED" message. can fail to generate an assertion and instead indicate a URL where
login should proceed.
IdPProxy -> PeerConnection:
{
"type": "LOGINNEEDED",
"id": "1",
"error": "...a message explaining the reason for failure...",
"loginUrl": "https://example.org/login?context=e982606f4fd5"
}
Figure 7: User interaction needed response
The "loginUrl" field of the "LOGINNEEDED" response contains a URL.
The PeerConnection provides an error event (or similar) to the
calling site that includes this URL.
A calling site is then able to load the provided URL in an IFRAME in
order to trigger the required user interactions. Once any user
interactions are complete, the IFRAME MUST send a postMessage
[WebMessaging] to its containing window indicating completion. Any
message is sufficient for this purpose, the "source" parameter
identifies the originating IFRAME.
In all other respects, "LOGINNEEDED" can be treated as an "ERROR" The application can then load the provided URL to enable the user to
message. enter credentials. The communication between the application and the
IdP is described in [webrtc-api].
5.6.5.4. Verifying Assertions 5.7. Verifying Assertions
In order to verify an assertion, an RP sends a "VERIFY" message to The input to identity validation is the assertion string taken from a
the IdP proxy containing the assertion supplied by the AP in the decoded a=identity attribute.
"message" field.
The IdP proxy verifies the assertion. Depending on the identity The IdP proxy verifies the assertion. Depending on the identity
protocol, the proxy might contact the IdP server or other servers. protocol, the proxy might contact the IdP server or other servers.
For instance, an OAuth-based protocol will likely require using the For instance, an OAuth-based protocol will likely require using the
IdP as an oracle, whereas with BrowserID the IdP proxy can likely IdP as an oracle, whereas with a signature-based scheme might be able
verify the signature on the assertion without contacting the IdP, to verify the assertion without contacting the IdP, provided that it
provided that it has cached the IdP's public key. has cached the relevant public key.
Regardless of the mechanism, if verification succeeds, a successful Regardless of the mechanism, if verification succeeds, a successful
response from the IdP proxy MUST contain a message field consisting response from the IdP proxy consists of the following information:
of a object with the following fields:
identity: The identity of the AP from the IdP's perspective. identity: The identity of the AP from the IdP's perspective.
Details of this are provided in Section 5.6.5.4.1. Details of this are provided in Section 5.7.1.
contents: The original unmodified string provided by the AP in the
original SIGN request.
Figure 8 shows an example transaction. Line breaks are inserted contents: The original unmodified string provided by the AP as input
solely for readability. to the assertion generation process.
PeerConnection -> IdP Proxy: Figure 6 shows an example response formatted as JSON for illustrative
{ purposes.
"type": "VERIFY",
"id": 2,
"origin": "https://calling-service.example.com/",
"message": "{\"identity\":\"bob@example.org\",
\"contents\":\"abcdefghijklmnopqrstuvwyz\",
\"signature\":\"010203040506\"}"
}
IdP Proxy -> PeerConnection: {
{ "identity": "bob@example.org",
"type": "SUCCESS", "contents": "{\"fingerprint\":[ ... ]}"
"id": 2, }
"message": {
"identity": "bob@example.org",
"contents": "abcdefghijklmnopqrstuvwyz"
}
}
Figure 8: Example verification request Figure 6: Example verification result
5.6.5.4.1. Identity Formats 5.7.1. Identity Formats
Identities passed from the IdP proxy to the PeerConnection are passed The identity provided from the IdP to the RP browser MUST consist of
in the "identity" field. This field MUST consist of a string a string representing the user's identity. This string is in the
representing the user's identity. This string is in the form form "<user>@<domain>", where "user" consists of any character except
"<user>@<domain>", where "user" consists of any character except '@', '@', and domain is an internationalized domain name [RFC5890].
and domain is an internationalized domain name [RFC5890].
The PeerConnection API MUST check this string as follows: The PeerConnection API MUST check this string as follows:
1. If the domain portion of the string is equal to the domain name 1. If the domain portion of the string is equal to the domain name
of the IdP proxy, then the assertion is valid, as the IdP is of the IdP proxy, then the assertion is valid, as the IdP is
authoritative for this domain. Comparison of domain names is authoritative for this domain. Comparison of domain names is
done using the label equivalence rule defined in Section 2.3.2.4 done using the label equivalence rule defined in Section 2.3.2.4
of [RFC5890]. of [RFC5890].
2. If the domain portion of the string is not equal to the domain 2. If the domain portion of the string is not equal to the domain
name of the IdP proxy, then the PeerConnection object MUST reject name of the IdP proxy, then the PeerConnection object MUST reject
the assertion unless: the assertion unless:
1. the IdP domain is trusted as an acceptable third-party IdP; 1. the IdP domain is trusted as an acceptable third-party IdP;
and and
2. local policy is configured to trust this IdP domain for the 2. local policy is configured to trust this IdP domain for the
RHS of the identity string. domain portion of the identity string.
Sites which have identities that do not fit into the RFC822 style Sites that have identities that do not fit into the RFC822 style (for
(for instance, identifiers that are simple numeric values, or values instance, identifiers that are simple numeric values, or values that
that contain '@' characters) SHOULD convert them to this form by contain '@' characters) SHOULD convert them to this form by escaping
escaping illegal characters and appending their IdP domain (e.g., illegal characters and appending their IdP domain (e.g.,
user%40133@identity.example.com), thus ensuring that they are user%40133@identity.example.com), thus ensuring that they are
authoritative for the identity. authoritative for the identity.
6. Security Considerations 6. Security Considerations
Much of the security analysis of this problem is contained in Much of the security analysis of this problem is contained in
[I-D.ietf-rtcweb-security] or in the discussion of the particular [I-D.ietf-rtcweb-security] or in the discussion of the particular
issues above. In order to avoid repetition, this section focuses on issues above. In order to avoid repetition, this section focuses on
(a) residual threats that are not addressed by this document and (b) (a) residual threats that are not addressed by this document and (b)
threats produced by failure/misbehavior of one of the components in threats produced by failure/misbehavior of one of the components in
skipping to change at page 32, line 36 skipping to change at page 29, line 46
In order to protect against malicious content JavaScript, that In order to protect against malicious content JavaScript, that
JavaScript MUST NOT be allowed to have direct access to---or perform JavaScript MUST NOT be allowed to have direct access to---or perform
computations with---DTLS keys. For instance, if content JS were able computations with---DTLS keys. For instance, if content JS were able
to compute digital signatures, then it would be possible for content to compute digital signatures, then it would be possible for content
JS to get an identity assertion for a browser's generated key and JS to get an identity assertion for a browser's generated key and
then use that assertion plus a signature by the key to authenticate a then use that assertion plus a signature by the key to authenticate a
call protected under an ephemeral DH key controlled by the content call protected under an ephemeral DH key controlled by the content
JS, thus violating the security guarantees otherwise provided by the JS, thus violating the security guarantees otherwise provided by the
IdP mechanism. Note that it is not sufficient merely to deny the IdP mechanism. Note that it is not sufficient merely to deny the
content JS direct access to the keys, as some have suggested doing content JS direct access to the keys, as some have suggested doing
with the WebCrypto API. [webcrypto]. The JS must also not be allowed with the WebCrypto API. [webcrypto]. The JS must also not be
to perform operations that would be valid for a DTLS endpoint. By allowed to perform operations that would be valid for a DTLS
far the safest approach is simply to deny the ability to perform any endpoint. By far the safest approach is simply to deny the ability
operations that depend on secret information associated with the key. to perform any operations that depend on secret information
Operations that depend on public information, such as exporting the associated with the key. Operations that depend on public
public key are of course safe. information, such as exporting the public key are of course safe.
6.2. Privacy 6.2. Privacy
The requirements in this document are intended to allow: The requirements in this document are intended to allow:
o Users to participate in calls without revealing their location. o Users to participate in calls without revealing their location.
o Potential callees to avoid revealing their location and even o Potential callees to avoid revealing their location and even
presence status prior to agreeing to answer a call. presence status prior to agreeing to answer a call.
However, these privacy protections come at a performance cost in However, these privacy protections come at a performance cost in
terms of using TURN relays and, in the latter case, delaying ICE. terms of using TURN relays and, in the latter case, delaying ICE.
Sites SHOULD make users aware of these tradeoffs. Sites SHOULD make users aware of these tradeoffs.
Note that the protections provided here assume a non-malicious Note that the protections provided here assume a non-malicious
calling service. As the calling service always knows the users calling service. As the calling service always knows the users
status and (absent the use of a technology like Tor) their IP status and (absent the use of a technology like Tor) their IP
skipping to change at page 33, line 34 skipping to change at page 30, line 45
6.3. Denial of Service 6.3. Denial of Service
The consent mechanisms described in this document are intended to The consent mechanisms described in this document are intended to
mitigate denial of service attacks in which an attacker uses clients mitigate denial of service attacks in which an attacker uses clients
to send large amounts of traffic to a victim without the consent of to send large amounts of traffic to a victim without the consent of
the victim. While these mechanisms are sufficient to protect victims the victim. While these mechanisms are sufficient to protect victims
who have not implemented WebRTC at all, WebRTC implementations need who have not implemented WebRTC at all, WebRTC implementations need
to be more careful. to be more careful.
Consider the case of a call center which accepts calls via RTCWeb. Consider the case of a call center which accepts calls via WebRTC.
An attacker proxies the call center's front-end and arranges for An attacker proxies the call center's front-end and arranges for
multiple clients to initiate calls to the call center. Note that multiple clients to initiate calls to the call center. Note that
this requires user consent in many cases but because the data channel this requires user consent in many cases but because the data channel
does not need consent, he can use that directly. Since ICE will does not need consent, he can use that directly. Since ICE will
complete, browsers can then be induced to send large amounts of data complete, browsers can then be induced to send large amounts of data
to the victim call center if it supports the data channel at all. to the victim call center if it supports the data channel at all.
Preventing this attack requires that automated WebRTC implementations Preventing this attack requires that automated WebRTC implementations
implement sensible flow control and have the ability to triage out implement sensible flow control and have the ability to triage out
(i.e., stop responding to ICE probes on) calls which are behaving (i.e., stop responding to ICE probes on) calls which are behaving
badly, and especially to be prepared to remotely throttle the data badly, and especially to be prepared to remotely throttle the data
skipping to change at page 34, line 45 skipping to change at page 32, line 8
PeerConnection correctly enforcing the security invariants described PeerConnection correctly enforcing the security invariants described
above. At a high level, the IdP is attesting that the user above. At a high level, the IdP is attesting that the user
identified in the assertion wishes to be associated with the identified in the assertion wishes to be associated with the
assertion. Thus, it must not be possible for arbitrary third parties assertion. Thus, it must not be possible for arbitrary third parties
to get assertions tied to a user or to produce assertions that RPs to get assertions tied to a user or to produce assertions that RPs
will accept. will accept.
6.4.1. PeerConnection Origin Check 6.4.1. PeerConnection Origin Check
Fundamentally, the IdP proxy is just a piece of HTML and JS loaded by Fundamentally, the IdP proxy is just a piece of HTML and JS loaded by
the browser, so nothing stops a Web attacker o from creating their the browser, so nothing stops a Web attacker from creating their own
own IFRAME, loading the IdP proxy HTML/JS, and requesting a IFRAME, loading the IdP proxy HTML/JS, and requesting a signature.
signature. In order to prevent this attack, we require that all In order to prevent this attack, we require that all signatures be
signatures be tied to a specific origin ("rtcweb://...") which cannot tied to a specific origin ("rtcweb://...") which cannot be produced
be produced by content JavaScript. Thus, while an attacker can by content JavaScript. Thus, while an attacker can instantiate the
instantiate the IdP proxy, they cannot send messages from an IdP proxy, they cannot send messages from an appropriate origin and
appropriate origin and so cannot create acceptable assertions. I.e., so cannot create acceptable assertions. I.e., the assertion request
the assertion request must have come from the browser. This origin must have come from the browser. This origin check is enforced on
check is enforced on the relying party side, not on the the relying party side, not on the authenticating party side. The
authenticating party side. The reason for this is to take the burden reason for this is to take the burden of knowing which origins are
of knowing which origins are valid off of the IdP, thus making this valid off of the IdP, thus making this mechanism extensible to other
mechanism extensible to other applications besides WebRTC. The IdP applications besides WebRTC. The IdP simply needs to gather the
simply needs to gather the origin information (from the posted origin information (from the posted message) and attach it to the
message) and attach it to the assertion. assertion.
Note that although this origin check is enforced on the RP side and Note that although this origin check is enforced on the RP side and
not at the IdP, it is absolutely imperative that it be done. The not at the IdP, it is absolutely imperative that it be done. The
mechanisms in this document rely on the browser enforcing access mechanisms in this document rely on the browser enforcing access
restrictions on the DTLS keys and assertion requests which do not restrictions on the DTLS keys and assertion requests which do not
come with the right origin may be from content JS rather than from come with the right origin may be from content JS rather than from
browsers, and therefore those access restrictions cannot be assumed. browsers, and therefore those access restrictions cannot be assumed.
Note that this check only asserts that the browser (or some other Note that this check only asserts that the browser (or some other
entity with access to the user's authentication data) attests to the entity with access to the user's authentication data) attests to the
request and hence to the fingerprint. It does not demonstrate that request and hence to the fingerprint. It does not demonstrate that
the browser has access to the associated private key. However, the browser has access to the associated private key. However,
attaching one's identity to a key that the user does not control does attaching one's identity to a key that the user does not control does
not appear to provide substantial leverage to an attacker, so a proof not appear to provide substantial leverage to an attacker, so a proof
of possession is omitted for simplicity. of possession is omitted for simplicity.
6.4.2. IdP Well-known URI 6.4.2. IdP Well-known URI
As described in Section 5.6.5.3.1 the IdP proxy HTML/JS landing page As described in Section 5.6.5 the IdP proxy HTML/JS landing page is
is located at a well-known URI based on the IdP's domain name. This located at a well-known URI based on the IdP's domain name. This
requirement prevents an attacker who can write some resources at the requirement prevents an attacker who can write some resources at the
IdP (e.g., on one's Facebook wall) from being able to impersonate the IdP (e.g., on one's Facebook wall) from being able to impersonate the
IdP. IdP.
6.4.3. Privacy of IdP-generated identities and the hosting site 6.4.3. Privacy of IdP-generated identities and the hosting site
Depending on the structure of the IdP's assertions, the calling site Depending on the structure of the IdP's assertions, the calling site
may learn the user's identity from the perspective of the IdP. In may learn the user's identity from the perspective of the IdP. In
many cases this is not an issue because the user is authenticating to many cases this is not an issue because the user is authenticating to
the site via the IdP in any case, for instance when the user has the site via the IdP in any case, for instance when the user has
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reasons. Any IdP which uses cookies to persist logins will be broken reasons. Any IdP which uses cookies to persist logins will be broken
by third-party cookie blocking. One option is to accept this as a by third-party cookie blocking. One option is to accept this as a
limitation; another is to have the PeerConnection object disable limitation; another is to have the PeerConnection object disable
third-party cookie blocking for the IdP proxy. third-party cookie blocking for the IdP proxy.
7. IANA Considerations 7. IANA Considerations
This specification defines the "identity" SDP attribute per the This specification defines the "identity" SDP attribute per the
procedures of Section 8.2.4 of [RFC4566]. The required information procedures of Section 8.2.4 of [RFC4566]. The required information
for the registration is included here: for the registration is included here:
Contact Name: Eric Rescorla (ekr@rftm.com) Contact Name: Eric Rescorla (ekr@rftm.com)
Attribute Name: identity Attribute Name: identity
Long Form: identity Long Form: identity
Type of Attribute: session-level Type of Attribute: session-level
Charset Considerations: This attribute is not subject to the charset Charset Considerations: This attribute is not subject to the charset
attribute. attribute.
Purpose: This attribute carries an identity assertion, binding an Purpose: This attribute carries an identity assertion, binding an
identity to the transport-level security session. identity to the transport-level security session.
Appropriate Values: See Section 5.6.4.3 of RFCXXXX [[Editor Note:
Appropriate Values: See Section 5.6.4.2 of RFCXXXX [[Editor Note:
This document. This document.
8. Acknowledgements 8. Acknowledgements
Bernard Aboba, Harald Alvestrand, Richard Barnes, Dan Druta, Cullen Bernard Aboba, Harald Alvestrand, Richard Barnes, Dan Druta, Cullen
Jennings, Hadriel Kaplan, Matthew Kaufman, Jim McEachern, Martin Jennings, Hadriel Kaplan, Matthew Kaufman, Jim McEachern, Martin
Thomson, Magnus Westerland. Matthew Kaufman provided the UI material Thomson, Magnus Westerland. Matthew Kaufman provided the UI material
in Section 5.5. in Section 5.5.
9. Changes 9. Changes
9.1. Changes since -06 9.1. Changes since -10
Update cipher suite profiles.
Rework IdP interaction based on implementation experience in Firefox.
9.2. Changes since -06
Replaced RTCWEB and RTC-Web with WebRTC, except when referring to the Replaced RTCWEB and RTC-Web with WebRTC, except when referring to the
IETF WG IETF WG
Forbade use in mixed content as discussed in Orlando. Forbade use in mixed content as discussed in Orlando.
Added a requirement to surface NULL ciphers to the top-level. Added a requirement to surface NULL ciphers to the top-level.
Tried to clarify SRTP versus DTLS-SRTP. Tried to clarify SRTP versus DTLS-SRTP.
Added a section on screen sharing permissions. Added a section on screen sharing permissions.
Assorted editorial work. Assorted editorial work.
9.2. Changes since -05 9.3. Changes since -05
The following changes have been made since the -05 draft. The following changes have been made since the -05 draft.
o Response to comments from Richard Barnes o Response to comments from Richard Barnes
o More explanation of the IdP security properties and the federation o More explanation of the IdP security properties and the federation
use case. use case.
o Editorial cleanup. o Editorial cleanup.
9.3. Changes since -03 9.4. Changes since -03
Version -04 was a version control mistake. Please ignore. Version -04 was a version control mistake. Please ignore.
The following changes have been made since the -04 draft. The following changes have been made since the -04 draft.
o Move origin check from IdP to RP per discussion in YVR. o Move origin check from IdP to RP per discussion in YVR.
o Clarified treatment of X.509-level identities. o Clarified treatment of X.509-level identities.
o Editorial cleanup. o Editorial cleanup.
9.4. Changes since -03 9.5. Changes since -03
9.5. Changes since -02 9.6. Changes since -02
The following changes have been made since the -02 draft. The following changes have been made since the -02 draft.
o Forbid persistent HTTP permissions. o Forbid persistent HTTP permissions.
o Clarified the text in S 5.4 to clearly refer to requirements on o Clarified the text in S 5.4 to clearly refer to requirements on
the API to provide functionality to the site. the API to provide functionality to the site.
o Fold in the IETF portion of draft-rescorla-rtcweb-generic-idp o Fold in the IETF portion of draft-rescorla-rtcweb-generic-idp
o Retarget the continuing consent section to assume Binding Requests o Retarget the continuing consent section to assume Binding Requests
o Added some more privacy and linkage text in various places. o Added some more privacy and linkage text in various places.
o Editorial improvements o Editorial improvements
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-avtcore-6222bis] [I-D.ietf-avtcore-6222bis]
Begen, A., Perkins, C., Wing, D., and E. Rescorla, Begen, A., Perkins, C., Wing, D., and E. Rescorla,
"Guidelines for Choosing RTP Control Protocol (RTCP) "Guidelines for Choosing RTP Control Protocol (RTCP)
Canonical Names (CNAMEs)", draft-ietf-avtcore-6222bis-06 Canonical Names (CNAMEs)", draft-ietf-avtcore-6222bis-06
skipping to change at page 38, line 38 skipping to change at page 36, line 18
[I-D.ietf-avtcore-6222bis] [I-D.ietf-avtcore-6222bis]
Begen, A., Perkins, C., Wing, D., and E. Rescorla, Begen, A., Perkins, C., Wing, D., and E. Rescorla,
"Guidelines for Choosing RTP Control Protocol (RTCP) "Guidelines for Choosing RTP Control Protocol (RTCP)
Canonical Names (CNAMEs)", draft-ietf-avtcore-6222bis-06 Canonical Names (CNAMEs)", draft-ietf-avtcore-6222bis-06
(work in progress), July 2013. (work in progress), July 2013.
[I-D.ietf-rtcweb-rtp-usage] [I-D.ietf-rtcweb-rtp-usage]
Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time Perkins, C., Westerlund, M., and J. Ott, "Web Real-Time
Communication (WebRTC): Media Transport and Use of RTP", Communication (WebRTC): Media Transport and Use of RTP",
draft-ietf-rtcweb-rtp-usage-15 (work in progress), draft-ietf-rtcweb-rtp-usage-22 (work in progress),
May 2014. February 2015.
[I-D.ietf-rtcweb-security] [I-D.ietf-rtcweb-security]
Rescorla, E., "Security Considerations for WebRTC", Rescorla, E., "Security Considerations for WebRTC", draft-
draft-ietf-rtcweb-security-06 (work in progress), ietf-rtcweb-security-08 (work in progress), February 2015.
January 2014.
[I-D.ietf-tsvwg-sctp-dtls-encaps] [I-D.ietf-tsvwg-sctp-dtls-encaps]
Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS Tuexen, M., Stewart, R., Jesup, R., and S. Loreto, "DTLS
Encapsulation of SCTP Packets", Encapsulation of SCTP Packets", draft-ietf-tsvwg-sctp-
draft-ietf-tsvwg-sctp-dtls-encaps-04 (work in progress), dtls-encaps-09 (work in progress), January 2015.
May 2014.
[I-D.muthu-behave-consent-freshness] [I-D.muthu-behave-consent-freshness]
Perumal, M., Wing, D., R, R., and T. Reddy, "STUN Usage Perumal, M., Wing, D., R, R., and T. Reddy, "STUN Usage
for Consent Freshness", for Consent Freshness", draft-muthu-behave-consent-
draft-muthu-behave-consent-freshness-04 (work in freshness-04 (work in progress), July 2013.
progress), July 2013.
[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, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. [RFC3711] Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K.
Norrman, "The Secure Real-time Transport Protocol (SRTP)", Norrman, "The Secure Real-time Transport Protocol (SRTP)",
RFC 3711, March 2004. RFC 3711, March 2004.
skipping to change at page 39, line 41 skipping to change at page 37, line 16
JavaScript Object Notation (JSON)", RFC 4627, July 2006. JavaScript Object Notation (JSON)", RFC 4627, July 2006.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006. Encodings", RFC 4648, October 2006.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax [RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008. Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5245] Rosenberg, J., "Interactive Connectivity Establishment [RFC5245] Rosenberg, J., "Interactive Connectivity Establishment
(ICE): A Protocol for Network Address Translator (NAT) (ICE): A Protocol for Network Address Translator (NAT)
Traversal for Offer/Answer Protocols", RFC 5245, Traversal for Offer/Answer Protocols", RFC 5245, April
April 2010. 2010.
[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, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework [RFC5763] Fischl, J., Tschofenig, H., and E. Rescorla, "Framework
for Establishing a Secure Real-time Transport Protocol for Establishing a Secure Real-time Transport Protocol
(SRTP) Security Context Using Datagram Transport Layer (SRTP) Security Context Using Datagram Transport Layer
Security (DTLS)", RFC 5763, May 2010. Security (DTLS)", RFC 5763, May 2010.
[RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer [RFC5764] McGrew, D. and E. Rescorla, "Datagram Transport Layer
Security (DTLS) Extension to Establish Keys for the Secure Security (DTLS) Extension to Establish Keys for the Secure
Real-time Transport Protocol (SRTP)", RFC 5764, May 2010. Real-time Transport Protocol (SRTP)", RFC 5764, May 2010.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785, Uniform Resource Identifiers (URIs)", RFC 5785, April
April 2010. 2010.
[RFC5890] Klensin, J., "Internationalized Domain Names for [RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework", Applications (IDNA): Definitions and Document Framework",
RFC 5890, August 2010. RFC 5890, August 2010.
[RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, [RFC6454] Barth, A., "The Web Origin Concept", RFC 6454, December
December 2011. 2011.
[WebMessaging] [WebMessaging]
Hickson, "HTML5 Web Messaging", May 2012, Hickson, , "HTML5 Web Messaging", May 2012,
<http://www.w3.org/TR/2012/CR-webmessaging-20120501/>. <http://www.w3.org/TR/2012/CR-webmessaging-20120501/>.
[webcrypto] [webcrypto]
Dahl, Sleevi, "Web Cryptography API", June 2013. Dahl, Sleevi, , "Web Cryptography API", June 2013.
Available at http://www.w3.org/TR/WebCryptoAPI/ Available at http://www.w3.org/TR/WebCryptoAPI/
[webrtc-api] [webrtc-api]
Bergkvist, Burnett, Jennings, Narayanan, "WebRTC 1.0: Bergkvist, Burnett, Jennings, Narayanan, , "WebRTC 1.0:
Real-time Communication Between Browsers", October 2011. Real-time Communication Between Browsers", October 2011.
Available at Available at http://dev.w3.org/2011/webrtc/editor/
http://dev.w3.org/2011/webrtc/editor/webrtc.html webrtc.html
10.2. Informative References 10.2. Informative References
[I-D.ietf-rtcweb-jsep] [I-D.ietf-rtcweb-jsep]
Uberti, J. and C. Jennings, "Javascript Session Uberti, J., Jennings, C., and E. Rescorla, "Javascript
Establishment Protocol", draft-ietf-rtcweb-jsep-06 (work Session Establishment Protocol", draft-ietf-rtcweb-jsep-08
in progress), February 2014. (work in progress), October 2014.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S., [RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication", Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999. RFC 2617, June 1999.
[RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston,
A., Peterson, J., Sparks, R., Handley, M., and E. A., Peterson, J., Sparks, R., Handley, M., and E.
Schooler, "SIP: Session Initiation Protocol", RFC 3261, Schooler, "SIP: Session Initiation Protocol", RFC 3261,
June 2002. June 2002.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport [RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, March 2010. Layer Security (TLS)", RFC 5705, March 2010.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
April 2011. April 2011.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC
RFC 6455, December 2011. 6455, December 2011.
[XmlHttpRequest] [XmlHttpRequest]
van Kesteren, A., "XMLHttpRequest Level 2", January 2012. van Kesteren, A., "XMLHttpRequest Level 2", January 2012.
Appendix A. Example IdP Bindings to Specific Protocols Appendix A. Example IdP Bindings to Specific Protocols
[[TODO: These still need some cleanup.]] [[TODO: These still need some cleanup.]]
This section provides some examples of how the mechanisms described This section provides some examples of how the mechanisms described
in this document could be used with existing authentication protocols in this document could be used with existing authentication protocols
such as BrowserID or OAuth. Note that this does not require browser- such as BrowserID or OAuth. Note that this does not require browser-
level support for either protocol. Rather, the protocols can be fit level support for either protocol. Rather, the protocols can be fit
into the generic framework. (Though BrowserID in particular works into the generic framework. (Though BrowserID in particular works
better with some client side support). better with some client side support).
A.1. BrowserID A.1. BrowserID
skipping to change at page 45, line 35 skipping to change at page 43, line 35
IdP. IdP.
Author's Address Author's Address
Eric Rescorla Eric Rescorla
RTFM, Inc. RTFM, Inc.
2064 Edgewood Drive 2064 Edgewood Drive
Palo Alto, CA 94303 Palo Alto, CA 94303
USA USA
Phone: +1 650 678 2350 Phone: +1 650 678 2350
Email: ekr@rtfm.com Email: ekr@rtfm.com
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