< draft-ietf-rtcweb-security-arch-18.txt   draft-ietf-rtcweb-security-arch-19.txt >
RTCWEB E. Rescorla RTCWEB E. Rescorla
Internet-Draft RTFM, Inc. Internet-Draft RTFM, Inc.
Intended status: Standards Track February 1, 2019 Intended status: Standards Track July 7, 2019
Expires: August 5, 2019 Expires: January 8, 2020
WebRTC Security Architecture WebRTC Security Architecture
draft-ietf-rtcweb-security-arch-18 draft-ietf-rtcweb-security-arch-19
Abstract Abstract
This document defines the security architecture for WebRTC, a This document defines the security architecture for WebRTC, a
protocol suite intended for use with real-time applications that can protocol suite intended for use with real-time applications that can
be deployed in browsers - "real time communication on the Web". be deployed in browsers - "real time communication on the Web".
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
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 5, 2019. This Internet-Draft will expire on January 8, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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12.2. Changes since -11 . . . . . . . . . . . . . . . . . . . 37 12.2. Changes since -11 . . . . . . . . . . . . . . . . . . . 37
12.3. Changes since -10 . . . . . . . . . . . . . . . . . . . 37 12.3. Changes since -10 . . . . . . . . . . . . . . . . . . . 37
12.4. Changes since -06 . . . . . . . . . . . . . . . . . . . 37 12.4. Changes since -06 . . . . . . . . . . . . . . . . . . . 37
12.5. Changes since -05 . . . . . . . . . . . . . . . . . . . 38 12.5. Changes since -05 . . . . . . . . . . . . . . . . . . . 38
12.6. Changes since -03 . . . . . . . . . . . . . . . . . . . 38 12.6. Changes since -03 . . . . . . . . . . . . . . . . . . . 38
12.7. Changes since -03 . . . . . . . . . . . . . . . . . . . 38 12.7. Changes since -03 . . . . . . . . . . . . . . . . . . . 38
12.8. Changes since -02 . . . . . . . . . . . . . . . . . . . 38 12.8. Changes since -02 . . . . . . . . . . . . . . . . . . . 38
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 39 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 39
13.1. Normative References . . . . . . . . . . . . . . . . . . 39 13.1. Normative References . . . . . . . . . . . . . . . . . . 39
13.2. Informative References . . . . . . . . . . . . . . . . . 42 13.2. Informative References . . . . . . . . . . . . . . . . . 42
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 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 (RTCWEB) working group
tasked with standardizing protocols for real-time communications standardized protocols for real-time communications between Web
between Web browsers. The major use cases for WebRTC technology are browsers, generally called "WebRTC" [I-D.ietf-rtcweb-overview]. The
real-time audio and/or video calls, Web conferencing, and direct data major use cases for WebRTC technology are real-time audio and/or
transfer. Unlike most conventional real-time systems, (e.g., SIP- video calls, Web conferencing, and direct data transfer. Unlike most
based [RFC3261] soft phones) WebRTC communications are directly conventional real-time systems, (e.g., SIP-based [RFC3261] soft
controlled by some Web server, via a JavaScript (JS) API as shown in phones) WebRTC communications are directly controlled by some Web
Figure 1. server, via a JavaScript (JS) API as shown in Figure 1.
+----------------+ +----------------+
| | | |
| Web Server | | Web Server |
| | | |
+----------------+ +----------------+
^ ^ ^ ^
/ \ / \
HTTP / \ HTTP HTTP / \ HTTP
/ \ / \
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| | Media | | | | Media | |
| Browser |<---------->| Browser | | Browser |<---------->| Browser |
| | | | | | | |
+-----------+ +-----------+ +-----------+ +-----------+
Figure 1: A simple WebRTC system Figure 1: A simple WebRTC system
A more complicated system might allow for interdomain calling, as A more complicated system might allow for interdomain calling, as
shown in Figure 2. The protocol to be used between the domains is shown in Figure 2. The protocol to be used between the domains is
not standardized by WebRTC, but given the installed base and the form not standardized by WebRTC, but given the installed base and the form
of the WebRTC API is likely to be something SDP-based like SIP. of the WebRTC API is likely to be something SDP-based like SIP or
something like Extensible Messaging and Presence Protocol (XMPP)
[RFC6120].
+--------------+ +--------------+ +--------------+ +--------------+
| | SIP,XMPP,...| | | | SIP,XMPP,...| |
| Web Server |<----------->| Web Server | | Web Server |<----------->| Web Server |
| | | | | | | |
+--------------+ +--------------+ +--------------+ +--------------+
^ ^ ^ ^
| | | |
HTTP | | HTTP HTTP | | HTTP
| | | |
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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.example.org/ is owned by Dr. Evil does not mean that we
trust Dr. Evil to access our camera and microphone. However, it can 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
call, but he doesn't want Dr. Evil to be able to access his camera call, but he doesn't want Dr. Evil to be able to access his camera
and microphone other than during the call. The point here is that we and microphone other than during the call. The point here is that we
must first identify other elements before we can determine whether must first identify other elements before we can determine whether
and how much to trust them. Additionally, sometimes we need to and how much to trust them. Additionally, sometimes we need to
identify the communicating peer before we know what policies to identify the communicating peer before we know what policies to
apply. apply.
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| | +------------------------>| | | | +------------------------>| |
+-----------+ +-----------+ +-----------+ +-----------+
Figure 4: A federated call with IdP-based identity Figure 4: A federated call with IdP-based identity
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 until 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 (with technologies such as Federated Google Login, Web environment (with technologies such as Federated Google Login,
Facebook Connect, OAuth, OpenID, WebFinger), and is often provided as Facebook Connect, OAuth, OpenID, WebFinger), and is often provided as
a side effect service of a user's ordinary accounts with some a side effect service of a user's ordinary accounts with some
service. In this example, we show Alice and Bob using a separate service. In this example, we show Alice and Bob using a separate
identity service, though the identity service may be the same entity identity service, though the identity service may be the same entity
as the calling service or there may be no identity service at all. as the calling service or there may be no identity service at all.
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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 7 PeerConnection can identity service (though as discussed in Section 7 PeerConnection can
be agnostic to them), but for now it's easiest to think of as an be agnostic to them), but for now it's easiest to think of as an
OAuth token. The assertion may bind other information to the OAuth token. 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], over TLS [RFC5246]. The
[RFC5246]. The signaling server processes the message from Alice's signaling server processes the message from Alice's browser,
browser, determines that this is a call to Bob and sends a signaling determines that this is a call to Bob and sends a signaling message
message to Bob's browser (again, the format is currently undefined). to Bob's browser (again, the format is currently undefined). The JS
The JS on Bob's browser processes it, and alerts Bob to the incoming on Bob's browser processes it, and alerts Bob to the incoming call
call and to Alice's identity. In this case, Alice has provided an 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. It is also
the browser to display a trusted element in the browser chrome possible to have IdPs with which the browser has a specific
indicating that a call is coming in from Alice. If Alice is in Bob's trustrelationship, as described in Section 7.1. This allows the
address book, then this interface might also include her real name, a 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 address
book, then this interface might also include her real name, a
picture, etc. The calling site will also provide some user interface picture, etc. The calling site will also provide some user interface
element (e.g., a button) to allow Bob to answer the call, though this element (e.g., a button) to allow Bob to answer the call, though this
is most likely not part of the trusted UI. is most likely not part of the trusted UI.
If Bob agrees a PeerConnection is instantiated with the message from If Bob agrees a PeerConnection is instantiated with the message from
Alice's side. Then, a similar process occurs as on Alice's browser: Alice's side. Then, a similar process occurs as on Alice's browser:
Bob's browser prompts him for device permission, the media streams Bob's browser prompts him for device permission, the media streams
are created, and a return signaling message containing media are created, and a return signaling message containing media
information, ICE candidates, and a fingerprint is sent back to Alice information, ICE candidates, and a fingerprint is sent back to Alice
via the signaling service. If Bob has a relationship with an IdP, via the signaling service. If Bob has a relationship with an IdP,
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is willing to exchange traffic with her and (b) that either Bob is at is willing to exchange traffic with her and (b) that either Bob is at
the IP address which she has verified via ICE or there is an attacker the IP address which she has verified via ICE or there is an attacker
who is on-path to that IP address detouring the traffic. Note that who is on-path to that IP address detouring the traffic. Note that
it is not possible for an attacker who is on-path between Alice and it is not possible for an attacker who is on-path between Alice and
Bob but not attached to the signaling service to spoof these checks Bob but not attached to the signaling service to spoof these checks
because they do not have the ICE credentials. Bob has the same because they do not have the ICE credentials. Bob has the same
security guarantees with respect to Alice. security guarantees with respect to Alice.
4.3. DTLS Handshake 4.3. DTLS Handshake
Once the ICE checks have completed [more specifically, once some ICE Once the requisite ICE checks have completed, Alice and Bob can set
checks have completed], Alice and Bob can set up a secure channel or up a secure channel or channels. This is performed via DTLS
channels. This is performed via DTLS [RFC6347] and DTLS-SRTP [RFC6347] and DTLS-SRTP [RFC5763] keying for SRTP [RFC3711] for the
[RFC5763] keying for SRTP [RFC3711] for the media channel and SCTP media channel and SCTP over DTLS [RFC8261] for data channels.
over DTLS [RFC8261] for data channels. Specifically, Alice and Bob Specifically, Alice and Bob perform a DTLS handshake on every
perform a DTLS handshake on every component which has been component which has been established by ICE. The total number of
established by ICE. The total number of channels depends on the channels depends on the amount of muxing; in the most likely case we
amount of muxing; in the most likely case we are using both RTP/RTCP are using both RTP/RTCP mux and muxing multiple media streams on the
mux and muxing multiple media streams on the same channel, in which same channel, in which case there is only one DTLS handshake. Once
case there is only one DTLS handshake. Once the DTLS handshake has the DTLS handshake has completed, the keys are exported [RFC5705] and
completed, the keys are exported [RFC5705] and used to key SRTP for used to key SRTP for the media channels.
the media channels.
At this point, Alice and Bob know that they share a set of secure At this point, Alice and Bob know that they share a set of secure
data and/or media channels with keys which are not known to any data and/or media channels with keys which are not known to any
third-party attacker. If Alice and Bob authenticated via their IdPs, third-party attacker. If Alice and Bob authenticated via their IdPs,
then they also know that the signaling service is not mounting a man- then they also know that the signaling service is not mounting a man-
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
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Value: identity-assertion Value: identity-assertion
Usage Level: session Usage Level: session
Charset Dependent: no Charset Dependent: no
Default Value: N/A Default Value: N/A
Name: identity Name: identity
Syntax: Syntax:
identity-assertion = identity-assertion-value identity-assertion = identity-assertion-value
*(SP identity-extension) *(SP identity-extension)
identity-assertion-value = base64 identity-assertion-value = base64
identity-extension = extension-name [ "=" extension-value ] identity-extension = extension-name [ "=" extension-value ]
extension-name = token extension-name = token
extension-value = 1*(%x01-09 / %x0b-0c / %x0e-3a / %x3c-ff) extension-value = 1*(%x01-09 / %x0b-0c / %x0e-3a / %x3c-ff)
; byte-string from [RFC4566] ; byte-string from [RFC4566]
<ALPHA and DIGIT as defined in [RFC4566]> <ALPHA and DIGIT as defined in [RFC4566]>
<base64 as defined in [RFC4566]> <base64 as defined in [RFC4566]>
Example: Example:
a=identity:\ a=identity:\
eyJpZHAiOnsiZG9tYWluIjoiZXhhbXBsZS5vcmciLCJwcm90b2NvbCI6ImJvZ3Vz\ eyJpZHAiOnsiZG9tYWluIjoiZXhhbXBsZS5vcmciLCJwcm90b2NvbCI6ImJvZ3Vz\
In0sImFzc2VydGlvbiI6IntcImlkZW50aXR5XCI6XCJib2JAZXhhbXBsZS5vcmdc\ In0sImFzc2VydGlvbiI6IntcImlkZW50aXR5XCI6XCJib2JAZXhhbXBsZS5vcmdc\
IixcImNvbnRlbnRzXCI6XCJhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3l6XCIsXCJz\ IixcImNvbnRlbnRzXCI6XCJhYmNkZWZnaGlqa2xtbm9wcXJzdHV2d3l6XCIsXCJz\
aWduYXR1cmVcIjpcIjAxMDIwMzA0MDUwNlwifSJ9 aWduYXR1cmVcIjpcIjAxMDIwMzA0MDUwNlwifSJ9
Note that long lines in the example are folded to meet the column Note that long lines in the example are folded to meet the column
width constraints of this document; the backslash ("\") at the end of width constraints of this document; the backslash ("\") at the end of
a line and the carriage return that follows shall be ignored. a line, the carriage return that follows, and whitespace shall be ignored.
This specification does not define any extensions for the attribute. This specification does not define any extensions for the attribute.
The identity-assertion value is a JSON [RFC8259] encoded string. The The identity-assertion value is a JSON [RFC8259] encoded string. The
JSON object contains two keys: "assertion" and "idp". The JSON object contains two keys: "assertion" and "idp". The
"assertion" key value contains an opaque string that is consumed by "assertion" key value contains an opaque string that is consumed by
the IdP. The "idp" key value contains a dictionary with one or two the IdP. The "idp" key value contains a dictionary with one or two
further values that identify the IdP. See Section 7.6 for more further values that identify the IdP. See Section 7.6 for more
details. details.
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If the answerer elects to include an 'identity' attribute, it follows If the answerer elects to include an 'identity' attribute, it follows
the same steps as those in Section 5.1.1. The answerer can choose to the same steps as those in Section 5.1.1. The answerer can choose to
include or omit an 'identity' attribute independently, regardless of include or omit an 'identity' attribute independently, regardless of
whether the offerer did so. whether the offerer did so.
5.1.3. Processing an SDP Offer or Answer 5.1.3. Processing an SDP Offer or Answer
When an endpoint receives an offer or answer that contains an When an endpoint receives an offer or answer that contains an
'identity' attribute, the answerer can use the the attribute 'identity' attribute, the answerer can use the the attribute
information to contact the IdP, and verify the identity of the peer. information to contact the IdP and verify the identity of the peer.
If the identity verification fails, the answerer MUST discard the If the identity requires a third-party IdP as described in
offer or answer as malformed. Section 7.1 then that IdP will need to have been specifically
configured. If the identity verification fails, the answerer MUST
discard the offer or answer as malformed.
5.1.4. Modifying the Session 5.1.4. Modifying the Session
When modifying a session, if the set of fingerprints is unchanged, When modifying a session, if the set of fingerprints is unchanged,
then the sender MAY send the same 'identity' attribute. In this then the sender MAY send the same 'identity' attribute. In this
case, the established identity SHOULD be applied to existing DTLS case, the established identity MUST be applied to existing DTLS
connections as well as new connections established using one of those connections as well as new connections established using one of those
fingerprints. Note that [I-D.ietf-rtcweb-jsep], Section 5.2.1 fingerprints. Note that [I-D.ietf-rtcweb-jsep], Section 5.2.1
requires that each media section use the same set of fingerprints for requires that each media section use the same set of fingerprints for
every media section. every media section. If a new identity attribute is received, then
the receiver MUST apply that identity to all existing connections.
If the set of fingerprints changes, then the sender MUST either send If the set of fingerprints changes, then the sender MUST either send
a new 'identity' attribute or none at all. Because a change in a new 'identity' attribute or none at all. Because a change in
fingerprints also causes a new DTLS connection to be established, the fingerprints also causes a new DTLS connection to be established, the
receiver MUST discard all previously established identities. receiver MUST discard all previously established identities.
6. Detailed Technical Description 6. Detailed Technical Description
6.1. Origin and Web Security Issues 6.1. 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
settings. settings.
skipping to change at page 15, line 34 skipping to change at page 15, line 38
Implementations MUST obtain explicit user consent prior to providing Implementations MUST obtain explicit user consent prior to providing
access to the camera and/or microphone. Implementations MUST at access to the camera and/or microphone. Implementations MUST at
minimum support the following two permissions models for HTTPS minimum support the following two permissions models for HTTPS
origins. origins.
o Requests for one-time camera/microphone access. o Requests for one-time camera/microphone access.
o Requests for permanent access. o Requests for permanent access.
Because HTTP origins cannot be securely established against network Because HTTP origins cannot be securely established against network
attackers, implementations MUST NOT allow the setting of permanent attackers, implementations MUST refuse all permissions grants for
access permissions for HTTP origins. Implementations MUST refuse all HTTP origins.
permissions grants for HTTP origins.
In addition, they SHOULD support requests for access that promise In addition, they SHOULD support requests for access that promise
that media from this grant will be sent to a single communicating that media from this grant will be sent to a single communicating
peer (obviously there could be other requests for other peers). peer (obviously there could be other requests for other peers),
E.g., "Call customerservice@ford.com". The semantics of this request eE.g., "Call customerservice@example.org". The semantics of this
are that the media stream from the camera and microphone will only be request are that the media stream from the camera and microphone will
routed through a connection which has been cryptographically verified only be routed through a connection which has been cryptographically
(through the IdP mechanism or an X.509 certificate in the DTLS-SRTP verified (through the IdP mechanism or an X.509 certificate in the
handshake) as being associated with the stated identity. Note that DTLS-SRTP handshake) as being associated with the stated identity.
it is unlikely that browsers would have an X.509 certificate, but Note that it is unlikely that browsers would have X.509 certificates,
servers might. Browsers servicing such requests SHOULD clearly but servers might. Browsers servicing such requests SHOULD clearly
indicate that identity to the user when asking for permission. The indicate that identity to the user when asking for permission. The
idea behind this type of permissions is that a user might have a idea behind this type of permissions is that a user might have a
fairly narrow list of peers he is willing to communicate with, e.g., fairly narrow list of peers he is willing to communicate with, e.g.,
"my mother" rather than "anyone on Facebook". Narrow permissions "my mother" rather than "anyone on Facebook". Narrow permissions
grants allow the browser to do that enforcement. grants allow the browser to do that enforcement.
API Requirement: The API MUST provide a mechanism for the requesting API Requirement: The API MUST provide a mechanism for the requesting
JS to relinquish the ability to see or modify the media (e.g., via JS to relinquish the ability to see or modify the media (e.g., via
MediaStream.record()). Combined with secure authentication of the MediaStream.record()). Combined with secure authentication of the
communicating peer, this allows a user to be sure that the calling communicating peer, this allows a user to be sure that the calling
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o Browsers MUST provide a separate dialog request for screen/ o Browsers MUST provide a separate dialog request for screen/
application sharing permissions even if the media request is made application sharing permissions even if the media request is made
at the same time as camera and microphone. at the same time as camera and microphone.
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.
Clients MAY permit the formation of data channels without any direct Browsers 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 6.3 for a related issue). additional security. (See Section 6.3 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
skipping to change at page 17, line 43 skipping to change at page 17, line 43
requires that implementations respond to such requests, so this requires that implementations respond to such requests, so this
approach is maximally compatible. A separate document will profile approach is maximally compatible. A separate document will profile
the ICE timers to be used; see [RFC7675]. the ICE timers to be used; see [RFC7675].
6.4. IP Location Privacy 6.4. 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.
Rather, these requirements are intended to allow a site to cooperate Rather, these requirements are intended to allow a site to cooperate
with the user to hide the user's IP address from the other side of with the user to hide the user's IP address from the other side of
the call. Hiding the user's IP address from the server requires some the call. Hiding the user's IP address from the server requires some
sort of explicit privacy preserving mechanism on the client (e.g., sort of explicit privacy preserving mechanism on the client (e.g.,
Tor Browser [https://www.torproject.org/projects/torbrowser.html.en]) Tor Browser [https://www.torproject.org/projects/torbrowser.html.en])
and is out of scope for this specification. and is out of scope for this specification.
API Requirement: The API MUST provide a mechanism to allow the JS to API Requirement: The API MUST provide a mechanism to allow the JS to
skipping to change at page 18, line 28 skipping to change at page 18, line 28
API Requirement: The API MUST provide a mechanism for the calling API Requirement: The API MUST provide a mechanism for the calling
application to reconfigure an existing call to add non-TURN application to reconfigure an existing call to add non-TURN
candidates. Taken together, this and the previous requirement candidates. Taken together, this and the previous requirement
allow ICE negotiation to start immediately on incoming call allow ICE negotiation to start immediately on incoming call
notification, thus reducing post-dial delay, but also to avoid notification, thus reducing post-dial delay, but also to avoid
disclosing the user's IP address until they have decided to disclosing the user's IP address until they have decided to
answer. They also allow users to completely hide their IP address answer. They also allow users to completely hide their IP address
for the duration of the call. Finally, they allow a mechanism for for the duration of the call. Finally, they allow a mechanism for
the user to optimize performance by reconfiguring to allow non- the user to optimize performance by reconfiguring to allow non-
turn candidates during an active call if the user decides they no TURN candidates during an active call if the user decides they no
longer need to hide their IP address longer need to hide their IP address
Note that some enterprises may operate proxies and/or NATs designed Note that some enterprises may operate proxies and/or NATs designed
to hide internal IP addresses from the outside world. WebRTC to hide internal IP addresses from the outside world. WebRTC
provides no explicit mechanism to allow this function. Either such provides no explicit mechanism to allow this function. Either such
enterprises need to proxy the HTTP/HTTPS and modify the SDP and/or enterprises need to proxy the HTTP/HTTPS and modify the SDP and/or
the JS, or there needs to be browser support to set the "TURN-only" the JS, or there needs to be browser support to set the "TURN-only"
policy regardless of the site's preferences. policy regardless of the site's preferences.
6.5. Communications Security 6.5. Communications Security
Implementations MUST implement SRTP [RFC3711]. Implementations MUST Implementations MUST support SRTP [RFC3711]. Implementations MUST
implement DTLS [RFC6347] and DTLS-SRTP [RFC5763][RFC5764] for SRTP support DTLS [RFC6347] and DTLS-SRTP [RFC5763][RFC5764] for SRTP
keying. Implementations MUST implement [RFC8261]. keying. Implementations MUST support SCTP over DTLS [RFC8261].
All media channels MUST be secured via SRTP and SRTCP. Media traffic All media channels MUST be secured via SRTP and SRTCP. Media traffic
MUST NOT be sent over plain (unencrypted) RTP or RTCP; that is, MUST NOT be sent over plain (unencrypted) RTP or RTCP; that is,
implementations MUST NOT negotiate cipher suites with NULL encryption implementations MUST NOT negotiate cipher suites with NULL encryption
modes. DTLS-SRTP MUST be offered for every media channel. WebRTC modes. DTLS-SRTP MUST be offered for every media channel. WebRTC
implementations MUST NOT offer SDP Security Descriptions [RFC4568] or implementations MUST NOT offer SDP Security Descriptions [RFC4568] or
select it if offered. A SRTP MKI MUST NOT be used. select it if offered. A SRTP MKI MUST NOT be used.
All data channels MUST be secured via DTLS. All data channels MUST be secured via DTLS.
All Implementations MUST implement DTLS 1.2 with the All Implementations MUST support DTLS 1.2 with the
TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher suite and the P-256 TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 cipher suite and the P-256
curve [FIPS186]. Earlier drafts of this specification required DTLS curve [FIPS186]. Earlier drafts of this specification required DTLS
1.0 with the cipher suite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, and 1.0 with the cipher suite TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, and
at the time of this writing some implementations do not support DTLS at the time of this writing some implementations do not support DTLS
1.2; endpoints which support only DTLS 1.2 might encounter 1.2; endpoints which support only DTLS 1.2 might encounter
interoperability issues. The DTLS-SRTP protection profile interoperability issues. The DTLS-SRTP protection profile
SRTP_AES128_CM_HMAC_SHA1_80 MUST be supported for SRTP. SRTP_AES128_CM_HMAC_SHA1_80 MUST be supported for SRTP.
Implementations MUST favor cipher suites which support (Perfect Implementations MUST favor cipher suites which support (Perfect
Forward Secrecy) PFS over non-PFS cipher suites and SHOULD favor AEAD Forward Secrecy) PFS over non-PFS cipher suites and SHOULD favor AEAD
over non-AEAD cipher suites. over non-AEAD cipher suites.
skipping to change at page 20, line 20 skipping to change at page 20, line 20
party verifiable X.509 certificate or via a Web IdP mechanism party verifiable X.509 certificate or via a Web IdP mechanism
(see Section 7) the "security characteristics" MUST include the (see Section 7) the "security characteristics" MUST include the
verified information. X.509 identities and Web IdP identities verified information. X.509 identities and Web IdP identities
have similar semantics and should be displayed in a similar have similar semantics and should be displayed in a similar
way. 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".) However, if Null algorithms in use (For example: "AES-CBC".)
ciphers are used, that MUST be presented to 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 a Short Authentication String (SAS). certificate fingerprint or a Short Authentication String (SAS).
These are compared by the peers to authenticate one another.
7. Web-Based Peer Authentication 7. 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 identify the endpoint on the other browser) to be able to directly identify the endpoint on the other
side without trusting 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,
Facebook Connect etc.) have been developed. While the details vary, Facebook Connect etc.) have been developed. While the details vary,
what these technologies share is that they have a Web-based (i.e., what these technologies share is that they have a Web-based (i.e.,
HTTP/HTTPS) identity provider which attests to your identity. For HTTP/HTTPS) identity provider which attests to Alice's identity. For
instance, if I have an account at example.org, I could use the instance, if Alice has an account at example.org, Alice could use the
example.org identity provider to prove to others that I was example.org identity provider to prove to others that Alice is
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: Alice could call you on
Poker Galaxy but identify myself as alice@example.org. a poker site but identify herself 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
generate the input to the IdP assertion process and display the generate the input to the IdP assertion process and display the
results of the verification process to the user in a way which cannot results of the verification process to the user in a way which cannot
be imitated by the calling site. be imitated by the calling site.
The mechanisms defined in this document do not require the browser to The mechanisms defined in this document do not require the browser to
skipping to change at page 25, line 6 skipping to change at page 25, line 6
7.4. Binding Identity Assertions to JSEP Offer/Answer Transactions 7.4. 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/answer exchange and specifically to the media. IdP) to the SDP offer/answer exchange and specifically to the media.
In order to achieve this, the PeerConnection must provide the DTLS- In order to achieve this, the PeerConnection must provide the DTLS-
SRTP fingerprint to be bound to the identity. This is provided as a SRTP fingerprint to be bound to the identity. This is provided as a
JavaScript object (also known as a dictionary or hash) with a single JavaScript object (also known as a dictionary or hash) with a single
"fingerprint" key, as shown below: "fingerprint" key, as shown below:
{ {
"fingerprint": [ { "fingerprint":
"algorithm": "sha-256", [
"digest": "4A:AD:B9:B1:3F:...:E5:7C:AB" { "algorithm": "sha-256",
}, { "digest": "4A:AD:B9:B1:3F:...:E5:7C:AB" },
"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 "fingerprint" directly to the algorithm and digest values in the "fingerprint"
attribute of the SDP [RFC8122]. attribute of the SDP [RFC8122].
This object is encoded in a JSON [RFC8259] string for passing to the This object is encoded in a JSON [RFC8259] string for passing to the
IdP. The identity assertion returned by the IdP, which is encoded in IdP. The identity assertion returned by the IdP, which is encoded in
the "identity" attribute, is a JSON object that is encoded as the "identity" attribute, is a JSON object that is encoded as
skipping to change at page 26, line 5 skipping to change at page 26, line 5
7.4.1. Carrying Identity Assertions 7.4.1. Carrying Identity Assertions
Once an IdP has generated an assertion (see Section 7.6), it is Once an IdP has generated an assertion (see Section 7.6), it is
attached to the SDP offer/answer message. This is done by adding a attached to the SDP offer/answer message. This is done by adding a
new 'identity' attribute to the SDP. The sole contents of this value new 'identity' attribute to the SDP. The sole contents of this value
is the identity assertion. The identity assertion produced by the is the identity assertion. The identity assertion produced by the
IdP is encoded into a UTF-8 JSON text, then Base64-encoded [RFC4648] IdP is encoded into a UTF-8 JSON text, then Base64-encoded [RFC4648]
to produce this string. For example: to produce this string. 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
... ...
Note that long lines in the example are folded to meet the column Note that long lines in the example are folded to meet the column
width constraints of this document; the backslash ("\") at the end of width constraints of this document; the backslash ("\") at the end of
a line and the carriage return that follows shall be ignored. a line, the carriage return that follows, and whitespace shall be ignored.
The 'identity' attribute attests to all "fingerprint" attributes in The 'identity' attribute attests to all "fingerprint" attributes in
the session description. It is therefore a session-level attribute. the session description. It is therefore a session-level attribute.
Multiple "fingerprint" values can be used to offer alternative Multiple "fingerprint" values can be used to offer alternative
certificates for a peer. The "identity" attribute MUST include all certificates for a peer. The "identity" attribute MUST include all
fingerprint values that are included in "fingerprint" attributes of fingerprint values that are included in "fingerprint" attributes of
the session description. the session description.
The RP browser MUST verify that the in-use certificate for a DTLS The RP browser MUST verify that the in-use certificate for a DTLS
skipping to change at page 26, line 47 skipping to change at page 26, line 47
7.5. Determining the IdP URI 7.5. 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:
Authority: The authority [RFC3986] at which the IdP's service is Authority: The authority [RFC3986] at which the IdP's service is
hosted. Note that this may include a non-default port or a hosted.
userinfo component, but neither will be available in a certificate
verifying the site.
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. If no value for protocol is provided, a value of string. If no value for protocol is provided, a value of
"default" is used. "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:
skipping to change at page 28, line 49 skipping to change at page 28, line 49
identify a different IdP or protocol from the one that generated identify a different IdP or protocol from the one that generated
the assertion. the assertion.
assertion: An opaque value containing the assertion itself. This is assertion: An opaque value containing the assertion itself. This is
only interpretable by the identified IdP or the IdP code running only interpretable by the identified IdP or the IdP code running
in the client. in the client.
Figure 5 shows an example assertion formatted as JSON. In this case, Figure 5 shows an example assertion formatted as JSON. In this case,
the message has presumably been digitally signed/MACed in some way the message has presumably been digitally signed/MACed in some way
that the IdP can later verify it, but this is an implementation that the IdP can later verify it, but this is an implementation
detail and out of scope of this document. Line breaks are inserted detail and out of scope of this document.
solely for readability.
{ {
"idp":{ "idp":{
"domain": "example.org", "domain": "example.org",
"protocol": "bogus" "protocol": "bogus"
}, },
"assertion": "{\"identity\":\"bob@example.org\", "assertion": "{\"identity\":\"bob@example.org\",
\"contents\":\"abcdefghijklmnopqrstuvwyz\", \"contents\":\"abcdefghijklmnopqrstuvwyz\",
\"signature\":\"010203040506\"}" \"signature\":\"010203040506\"}"
} }
Figure 5: Example assertion Figure 5: Example assertion
For use in signaling, the assertion is serialized into JSON, For use in signaling, the assertion is serialized into JSON,
Base64-encoded [RFC4648], and used as the value of the "identity" Base64-encoded [RFC4648], and used as the value of the "identity"
attribute. attribute. IdPs SHOULD ensure that any assertions they generate
cannot be interpreted in a different context. E.g., they should use
a distinct format or have separate cryptographic keys for assertion
generation and other purposes. Line breaks are inserted solely for
readability.
7.7. Managing User Login 7.7. 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 [RFC7617] for subsequent exchanges. [RFC6265] or HTTP authentication [RFC7617] 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
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Regardless of the mechanism, if verification succeeds, a successful Regardless of the mechanism, if verification succeeds, a successful
response from the IdP proxy consists of the following information: response from the IdP proxy consists of the following information:
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 8.1. Details of this are provided in Section 8.1.
contents: The original unmodified string provided by the AP as input contents: The original unmodified string provided by the AP as input
to the assertion generation process. to the assertion generation process.
Figure 6 shows an example response formatted as JSON for illustrative Figure 6 shows an example response, which is JSON-formatted.
purposes.
{ {
"identity": "bob@example.org", "identity": "bob@example.org",
"contents": "{\"fingerprint\":[ ... ]}" "contents": "{\"fingerprint\":[ ... ]}"
} }
Figure 6: Example verification result Figure 6: Example verification result
8.1. Identity Formats 8.1. Identity Formats
The identity provided from the IdP to the RP browser MUST consist of The identity provided from the IdP to the RP browser MUST consist of
a string representing the user's identity. This string is in the a string representing the user's identity. This string is in the
form "<user>@<domain>", where "user" consists of any character except form "<user>@<domain>", where "user" consists of any character, and
'@', and domain is an internationalized domain name [RFC5890] encoded domain is aninternationalized domain name [RFC5890] encoded as a
as a sequence of U-labels. sequence of U-labels.
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 both:
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
domain portion of the identity string. domain portion of the identity string.
Any "@" or "%" characters in the "user" portion of the identity MUST Any "@" or "%" characters in the "user" portion of the identity MUST
be escaped according to the "Percent-Encoding" rules defined in be escaped according to the "Percent-Encoding" rules defined in
Section 2.1 of [RFC3986]. Characters other than "@" and "%" MUST NOT Section 2.1 of [RFC3986]. Characters other than "@" and "%" MUST NOT
be percent-encoded. For example, with a user of "user@133" and a be percent-encoded. For example, with a "user" of "user@133" and a
domain of "identity.example.com", the resulting string will be "domain" of "identity.example.com", the resulting string will be
encoded as "user%40133@identity.example.com". encoded as "user%40133@identity.example.com".
Implementations are cautioned to take care when displaying user Implementations are cautioned to take care when displaying user
identities containing escaped "@" characters. If such characters are identities containing escaped "@" characters. If such characters are
unescaped prior to display, implementations MUST distinguish between unescaped prior to display, implementations MUST distinguish between
the domain of the IdP proxy and any domain that might be implied by the domain of the IdP proxy and any domain that might be implied by
the portion of the <user> portion that appears after the escaped "@" the portion of the "<user>" portion that appears after the escaped
sign. "@" sign.
9. Security Considerations 9. 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
the system. the system.
skipping to change at page 31, line 46 skipping to change at page 31, line 49
Even if HTTPS is used, the signaling server can potentially mount a Even if HTTPS is used, the signaling server can potentially mount a
man-in-the-middle attack unless implementations have some mechanism man-in-the-middle attack unless implementations have some mechanism
for independently verifying keys. The UI requirements in Section 6.5 for independently verifying keys. The UI requirements in Section 6.5
are designed to provide such a mechanism for motivated/security are designed to provide such a mechanism for motivated/security
conscious users, but are not suitable for general use. The identity conscious users, but are not suitable for general use. The identity
service mechanisms in Section 7 are more suitable for general use. service mechanisms in Section 7 are more suitable for general use.
Note, however, that a malicious signaling service can strip off any Note, however, that a malicious signaling service can strip off any
such identity assertions, though it cannot forge new ones. Note that such identity assertions, though it cannot forge new ones. Note that
all of the third-party security mechanisms available (whether X.509 all of the third-party security mechanisms available (whether X.509
certificates or a third-party IdP) rely on the security of the third certificates or a third-party IdP) rely on the security of the third
party--this is of course also true of your connection to the Web site party--this is of course also true of the user's connection to the
itself. Users who wish to assure themselves of security against a Web site itself. Users who wish to assure themselves of security
malicious identity provider can only do so by verifying peer against a malicious identity provider can only do so by verifying
credentials directly, e.g., by checking the peer's fingerprint peer credentials directly, e.g., by checking the peer's fingerprint
against a value delivered out of band. against a value delivered out of band.
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 Diffie-Hellman (DH) key controlled call protected under an ephemeral Diffie-Hellman (DH) key controlled
by the content JS, thus violating the security guarantees otherwise by the content JS, thus violating the security guarantees otherwise
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privacy against the calling sites they are using must use separate privacy against the calling sites they are using must use separate
privacy enhancing technologies such as Tor. Combined WebRTC/Tor privacy enhancing technologies such as Tor. Combined WebRTC/Tor
implementations SHOULD arrange to route the media as well as the implementations SHOULD arrange to route the media as well as the
signaling through Tor. Currently this will produce very suboptimal signaling through Tor. Currently this will produce very suboptimal
performance. performance.
Additionally, any identifier which persists across multiple calls is Additionally, any identifier which persists across multiple calls is
potentially a problem for privacy, especially for anonymous calling potentially a problem for privacy, especially for anonymous calling
services. Such services SHOULD instruct the browser to use separate services. Such services SHOULD instruct the browser to use separate
DTLS keys for each call and also to use TURN throughout the call. DTLS keys for each call and also to use TURN throughout the call.
Otherwise, the other side will learn linkable information. Otherwise, the other side will learn linkable information that would
allow them to correlate the browser across multiple calls.
Additionally, browsers SHOULD implement the privacy-preserving CNAME Additionally, browsers SHOULD implement the privacy-preserving CNAME
generation mode of [RFC7022]. generation mode of [RFC7022].
9.3. Denial of Service 9.3. 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
skipping to change at page 35, line 18 skipping to change at page 35, line 18
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
logged in with Facebook Connect and is then authenticating their call logged in with Facebook Connect and is then authenticating their call
with a Facebook identity. However, in other case, the user may not with a Facebook identity. However, in other case, the user may not
have already revealed their identity to the site. In general, IdPs have already revealed their identity to the site. In general, IdPs
SHOULD either verify that the user is willing to have their identity SHOULD either verify that the user is willing to have their identity
revealed to the site (e.g., through the usual IdP permissions dialog) revealed to the site (e.g., through the usual IdP permissions dialog)
or arrange that the identity information is only available to known or arrange that the identity information is only available to known
RPs (e.g., social graph adjacencies) but not to the calling site. RPs (e.g., social graph adjacencies) but not to the calling site.
The "origin" field of the signature request can be used to check that The "domain" field of the assertion request can be used to check that
the user has agreed to disclose their identity to the calling site; the user has agreed to disclose their identity to the calling site;
because it is supplied by the PeerConnection it can be trusted to be because it is supplied by the PeerConnection it can be trusted to be
correct. correct.
9.4.4. Security of Third-Party IdPs 9.4.4. Security of Third-Party IdPs
As discussed above, each third-party IdP represents a new universal As discussed above, each third-party IdP represents a new universal
trust point and therefore the number of these IdPs needs to be quite trust point and therefore the number of these IdPs needs to be quite
limited. Most IdPs, even those which issue unqualified identities limited. Most IdPs, even those which issue unqualified identities
such as Facebook, can be recast as authoritative IdPs (e.g., such as Facebook, can be recast as authoritative IdPs (e.g.,
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mixed script usage (see [RFC5890], section 4.4). Other best mixed script usage (see [RFC5890], section 4.4). Other best
practices are still in development. practices are still in development.
9.4.5. Web Security Feature Interactions 9.4.5. Web Security Feature Interactions
A number of optional Web security features have the potential to A number of optional Web security features have the potential to
cause issues for this mechanism, as discussed below. cause issues for this mechanism, as discussed below.
9.4.5.1. Popup Blocking 9.4.5.1. Popup Blocking
The IdP proxy is unable to generate popup windows, dialogs or any When popup blocking is in use, the IdP proxy is unable to generate
other form of user interactions. This prevents the IdP proxy from popup windows, dialogs or any other form of user interactions. This
being used to circumvent user interaction. The "LOGINNEEDED" message prevents the IdP proxy from being used to circumvent user
allows the IdP proxy to inform the calling site of a need for user interaction. The "LOGINNEEDED" message allows the IdP proxy to
login, providing the information necessary to satisfy this inform the calling site of a need for user login, providing the
requirement without resorting to direct user interaction from the IdP information necessary to satisfy this requirement without resorting
proxy itself. to direct user interaction from the IdP proxy itself.
9.4.5.2. Third Party Cookies 9.4.5.2. Third Party Cookies
Some browsers allow users to block third party cookies (cookies Some browsers allow users to block third party cookies (cookies
associated with origins other than the top level page) for privacy associated with origins other than the top level page) for privacy
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.
10. IANA Considerations 10. 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: IESG (iesg@ietf.org)
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 of RFCXXXX [[Editor Note: This Appropriate Values: See Section 5 of RFCXXXX [[Editor Note: This
document.]] document.]]
Mux Category: NORMAL. Mux Category: NORMAL.
This section reqisters the "idp-proxy" well-known URI from [RFC5785].
URI suffix: idp-proxy
Change controller: IETF
11. Acknowledgements 11. 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 6.5. Christer Holmberg provided the initial version of in Section 6.5. Christer Holmberg provided the initial version of
Section 5.1. Section 5.1.
12. Changes 12. Changes
skipping to change at page 39, line 16 skipping to change at page 39, line 18
13.1. Normative References 13.1. Normative References
[FIPS186] National Institute of Standards and Technology (NIST), [FIPS186] National Institute of Standards and Technology (NIST),
"Digital Signature Standard (DSS)", NIST PUB 186-4 , July "Digital Signature Standard (DSS)", NIST PUB 186-4 , July
2013. 2013.
[I-D.ietf-mmusic-sdp-uks] [I-D.ietf-mmusic-sdp-uks]
Thomson, M. and E. Rescorla, "Unknown Key Share Attacks on Thomson, M. and E. Rescorla, "Unknown Key Share Attacks on
uses of TLS with the Session Description Protocol (SDP)", uses of TLS with the Session Description Protocol (SDP)",
draft-ietf-mmusic-sdp-uks-03 (work in progress), January draft-ietf-mmusic-sdp-uks-05 (work in progress), June
2019. 2019.
[I-D.ietf-rtcweb-jsep]
Uberti, J., Jennings, C., and E. Rescorla, "JavaScript
Session Establishment Protocol", draft-ietf-rtcweb-jsep-26
(work in progress), February 2019.
[I-D.ietf-rtcweb-overview]
Alvestrand, H., "Overview: Real Time Protocols for
Browser-based Applications", draft-ietf-rtcweb-overview-19
(work in progress), November 2017.
[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-26 (work in progress), March draft-ietf-rtcweb-rtp-usage-26 (work in progress), March
2016. 2016.
[I-D.ietf-rtcweb-security] [I-D.ietf-rtcweb-security]
Rescorla, E., "Security Considerations for WebRTC", draft- Rescorla, E., "Security Considerations for WebRTC", draft-
ietf-rtcweb-security-10 (work in progress), January 2018. ietf-rtcweb-security-12 (work in progress), July 2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818,
DOI 10.17487/RFC2818, May 2000, DOI 10.17487/RFC2818, May 2000,
<https://www.rfc-editor.org/info/rfc2818>. <https://www.rfc-editor.org/info/rfc2818>.
skipping to change at page 40, line 14 skipping to change at page 40, line 28
[RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session [RFC4568] Andreasen, F., Baugher, M., and D. Wing, "Session
Description Protocol (SDP) Security Descriptions for Media Description Protocol (SDP) Security Descriptions for Media
Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006, Streams", RFC 4568, DOI 10.17487/RFC4568, July 2006,
<https://www.rfc-editor.org/info/rfc4568>. <https://www.rfc-editor.org/info/rfc4568>.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data [RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006, Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
<https://www.rfc-editor.org/info/rfc4648>. <https://www.rfc-editor.org/info/rfc4648>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, (TLS) Protocol Version 1.2", RFC 5246,
DOI 10.17487/RFC5246, August 2008, DOI 10.17487/RFC5246, August 2008,
<https://www.rfc-editor.org/info/rfc5246>. <https://www.rfc-editor.org/info/rfc5246>.
[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, DOI 10.17487/RFC5763, May Security (DTLS)", RFC 5763, DOI 10.17487/RFC5763, May
2010, <https://www.rfc-editor.org/info/rfc5763>. 2010, <https://www.rfc-editor.org/info/rfc5763>.
skipping to change at page 41, line 47 skipping to change at page 42, line 12
SCTP Packets", RFC 8261, DOI 10.17487/RFC8261, November SCTP Packets", RFC 8261, DOI 10.17487/RFC8261, November
2017, <https://www.rfc-editor.org/info/rfc8261>. 2017, <https://www.rfc-editor.org/info/rfc8261>.
[RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive [RFC8445] Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", RFC 8445, Address Translator (NAT) Traversal", RFC 8445,
DOI 10.17487/RFC8445, July 2018, DOI 10.17487/RFC8445, July 2018,
<https://www.rfc-editor.org/info/rfc8445>. <https://www.rfc-editor.org/info/rfc8445>.
[webcrypto] [webcrypto]
Dahl, Sleevi, "Web Cryptography API", June 2013. editors, W., "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: editors, W., "WebRTC 1.0: Real-time Communication Between
Real-time Communication Between Browsers", October 2011. Browsers", October 2011.
Available at http://dev.w3.org/2011/webrtc/editor/ Available at http://dev.w3.org/2011/webrtc/editor/
webrtc.html webrtc.html
13.2. Informative References 13.2. Informative References
[I-D.ietf-rtcweb-jsep]
Uberti, J., Jennings, C., and E. Rescorla, "JavaScript
Session Establishment Protocol", draft-ietf-rtcweb-jsep-25
(work in progress), October 2018.
[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,
DOI 10.17487/RFC3261, June 2002, DOI 10.17487/RFC3261, June 2002,
<https://www.rfc-editor.org/info/rfc3261>. <https://www.rfc-editor.org/info/rfc3261>.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport [RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705, Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <https://www.rfc-editor.org/info/rfc5705>. March 2010, <https://www.rfc-editor.org/info/rfc5705>.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
March 2011, <https://www.rfc-editor.org/info/rfc6120>.
[RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265, [RFC6265] Barth, A., "HTTP State Management Mechanism", RFC 6265,
DOI 10.17487/RFC6265, April 2011, DOI 10.17487/RFC6265, April 2011,
<https://www.rfc-editor.org/info/rfc6265>. <https://www.rfc-editor.org/info/rfc6265>.
[RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol", [RFC6455] Fette, I. and A. Melnikov, "The WebSocket Protocol",
RFC 6455, DOI 10.17487/RFC6455, December 2011, RFC 6455, DOI 10.17487/RFC6455, December 2011,
<https://www.rfc-editor.org/info/rfc6455>. <https://www.rfc-editor.org/info/rfc6455>.
[RFC6943] Thaler, D., Ed., "Issues in Identifier Comparison for [RFC6943] Thaler, D., Ed., "Issues in Identifier Comparison for
Security Purposes", RFC 6943, DOI 10.17487/RFC6943, May Security Purposes", RFC 6943, DOI 10.17487/RFC6943, May
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