draft-ietf-rtcweb-stun-consent-freshness-02.txt   draft-ietf-rtcweb-stun-consent-freshness-03.txt 
RTCWEB M. Perumal RTCWEB M. Perumal
Internet-Draft D. Wing Internet-Draft D. Wing
Intended status: Standards Track R. Ravindranath Intended status: Standards Track R. Ravindranath
Expires: October 13, 2014 T. Reddy Expires: November 20, 2014 T. Reddy
Cisco Systems Cisco Systems
M. Thomson M. Thomson
Mozilla Mozilla
April 11, 2014 May 19, 2014
STUN Usage for Consent Freshness STUN Usage for Consent Freshness
draft-ietf-rtcweb-stun-consent-freshness-02 draft-ietf-rtcweb-stun-consent-freshness-03
Abstract Abstract
To prevent sending excessive traffic to an endpoint, periodic consent To prevent sending excessive traffic to an endpoint, periodic consent
needs to be obtained from that remote endpoint. needs to be obtained from that remote endpoint.
This document describes a consent mechanism using a new STUN usage. This document describes a consent mechanism using a new STUN usage.
This same mechanism can also determine connection loss ("liveness") This same mechanism can also determine connection loss ("liveness")
with a remote peer. with a remote peer.
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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 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 October 13, 2014. This Internet-Draft will expire on November 20, 2014.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 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
(http://trustee.ietf.org/license-info) in effect on the date of (http://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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include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Design Considerations . . . . . . . . . . . . . . . . . . . . 3 3. Design Considerations . . . . . . . . . . . . . . . . . . . . 3
4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 3 4. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 3
5. Connection Liveness . . . . . . . . . . . . . . . . . . . . . 4 4.1. Expiration of Consent . . . . . . . . . . . . . . . . . . 3
4.2. Immediate Revocation of Consent . . . . . . . . . . . . . 4
5. Connection Liveness . . . . . . . . . . . . . . . . . . . . . 5
6. DiffServ Treatment for Consent packets . . . . . . . . . . . 5 6. DiffServ Treatment for Consent packets . . . . . . . . . . . 5
7. W3C API Implications . . . . . . . . . . . . . . . . . . . . 5 7. W3C API Implications . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Security Considerations . . . . . . . . . . . . . . . . . . . 6
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 6
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
11.1. Normative References . . . . . . . . . . . . . . . . . . 6 11.1. Normative References . . . . . . . . . . . . . . . . . . 6
11.2. Informative References . . . . . . . . . . . . . . . . . 6 11.2. Informative References . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 Appendix A. Example Implementation . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8
1. Introduction 1. Introduction
To prevent attacks on peers, RTP endpoints have to ensure the remote To prevent attacks on peers, RTP endpoints have to ensure the remote
peer wants to receive traffic. This is performed both when the peer wants to receive traffic. This is performed both when the
session is first established to the remote peer using ICE session is first established to the remote peer using ICE
connectivity checks, and periodically for the duration of the session connectivity checks, and periodically for the duration of the session
using the procedures defined in this document. using the procedures defined in this document.
When a session is first established, WebRTC implementations are When a session is first established, WebRTC implementations are
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messages which verifies the remote peer's consent to receive traffic, messages which verifies the remote peer's consent to receive traffic,
and can also detect loss of liveness. and can also detect loss of liveness.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Consent: It is the mechanism of obtaining permission to send traffic Consent: It is the mechanism of obtaining permission to send traffic
to a certain transport address. This is usually obtained via ICE. to a certain transport address. This is the initial consent to
send traffic, which is obtained by ICE or a TCP handshake.
Consent Freshness: Permission to continue sending traffic to a Consent Freshness: Permission to continue sending traffic to a
certain transport address. This is performed by the procedure certain transport address. This is performed by the procedure
described in this document. described in this document.
Session Liveness: Detecting loss of connectivity to a certain Session Liveness: Detecting loss of connectivity to a certain
transport address. This is performed by the procedure described transport address. This is performed by the procedure described
in this document. in this document.
Transport Address: The remote peer's IP address and (UDP or TCP) Transport Address: The remote peer's IP address and (UDP or TCP)
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as STUN Indications which are send-and-forget, and do not evoke a as STUN Indications which are send-and-forget, and do not evoke a
response. A response is necessary both for consent to continue response. A response is necessary both for consent to continue
sending traffic, as well as to verify session liveness. Thus, we sending traffic, as well as to verify session liveness. Thus, we
need a request/response mechanism for consent freshness. ICE can be need a request/response mechanism for consent freshness. ICE can be
used for that mechanism because ICE already requires ICE agents used for that mechanism because ICE already requires ICE agents
continue listening for ICE messages, as described in section 10 of continue listening for ICE messages, as described in section 10 of
[RFC5245]. [RFC5245].
4. Solution Overview 4. Solution Overview
There are two ways consent to send traffic is revoked: expiration of
consent and immediate revocation of consent, which are discussed in
the following sections.
4.1. Expiration of Consent
A WebRTC browser performs a combined consent freshness and session A WebRTC browser performs a combined consent freshness and session
liveness test using STUN request/response as described below: liveness test using STUN request/response as described below:
An endpoint MUST NOT send application data (in WebRTC this means RTP An endpoint MUST NOT send application data (e.g., RTP, RTCP, SCTP,
or SCTP data) on an ICE-initiated connection unless the receiving DTLS) on an ICE-initiated connection unless the receiving endpoint
endpoint consents to receive the data. After a successful ICE consents to receive the data. After a successful ICE connectivity
connectivity check on a particular transport address, subsequent check on a particular transport address, subsequent consent MUST be
consent MUST be obtained following the procedure described in this obtained following the procedure described in this document. The
document. The consent expires after a fixed amount of time. consent expires after a fixed amount of time.
Explicit consent to send is indicated by:
1. Sending an ICE binding request to the remote peer's Transport Explicit consent to send is indicated by sending an ICE binding
Address and receiving a matching and authenticated ICE binding request to the remote peer's Transport Address and receiving a
response from the inverted remote peer's Transport Address. matching and authenticated ICE binding response from the inverted
remote peer's Transport Address. These ICE binding requests and
responses are authenticated using the same short-term credentials as
the initial ICE exchange, but using a new (fresh) transaction-id each
time consent needs to be refreshed. Implementations MUST obtain
fresh consent before their existing consent expires. If an ICE
binding response is not received within 1.5 times the previous round
trip time, another ICE binding request is sent using the a new
(fresh) transaction-id (so that round-trip time can be calculated),
and re-transmissions MUST NOT be sent more frequently than every
500ms or the smoothed round-trip time (from previous consent
freshness checks or RTP round-trip time), whichever is less. For the
purposes of this document, receipt of an ICE response with the
matching transaction-id of its request with a valid MESSAGE-INTEGRITY
is considered a consent response.
These ICE binding request/response are authenticated using the The initial Consent to send traffic is obtained by ICE. Consent
same short- term credentials as the initial ICE exchange, but expires after 30 seconds. That is, if a valid STUN binding response
using a new (fresh) transaction-id each time consent needs to be corresponding to one of the STUN requests sent in the last 30 seconds
refresh. Implementations MUST obtain fresh consent before their has not been received from the inverted 5-tuple, the endpoint MUST
existing consent expires. When obtaining fresh consent a STUN cease transmission on that 5-tuple.
connectivity check (or response) could be lost, and re-
transmissions MUST use the same STUN transaction-id, and re-
transmissions MUST NOT be sent more frequently than every 500ms
or the smoothed round-trip time (from previous consent freshness
checks or RTP round-trip time), whichever is less. For the
purposes of this document, receipt of an ICE response with the
matching transaction-id of its request with a valid MESSAGE-
INTEGRITY is considered an authenticated packet.
Consent expires after 15 seconds. That is, if an authenticated To meet the security needs of consent, an untrusted application
packet (e.g., DTLS, SRTP, ICE) has not been received from the (e.g., JavaScript) MUST NOT be able to obtain or control the ICE
inverted 5-tuple after 15 seconds, the application MUST cease transaction-id, because that enables spoofing STUN responses,
transmission on that 5-tuple. falsifying consent
Consent is ended immediately by receipt of a an authenticated message An endpoint that is only receiving application traffic (recvonly)
that closes the connection (for instance, a TLS fatal alert). does not need to obtain consent which can slightly conserve its
resources. However, the endpoint needs to ensure its NAT or firewall
mappings persist which can be done using keepalive or other
techniques (see Section 10 of [RFC5245] and see [RFC6263]). If the
endpoint wants send application traffic, it needs to first obtain
consent if its consent expired.
Receipt of an unauthenticated end-of-session message (e.g., TCP FIN) 4.2. Immediate Revocation of Consent
does not indicate loss of consent. Thus, an endpoint receiving an
unauthenticated end-of-session message SHOULD continue sending media
(over connectionless transport) or attempt to re-establish the
connection (over connection-oriented transport) until consent expires
or it receives an authenticated message revoking consent.
Although receiving authenticated packets is sufficient for consent, The previous section explained how consent expires due to a timeout.
it is still RECOMMENDED to send messages to keep NAT or firewall In some cases it is useful to signal a connection is terminated,
bindings alive (see Section 10 of [RFC5245] and [RFC6263]). rather than relying on a timeout. This is done by immediately
revoking consent.
To meet the security needs of consent, an implementation MUST ensure Consent for sending traffic on the media or data channel is revoked
that an application (e.g., Javascript application) is not able to by receipt of a an authenticated message that closes the connection
obtain or control STUN information relevant to consent, specifically (for instance, a TLS fatal alert).
the ICE transaction-id MUST NOT be accessible to upper-level
applications. Receipt of an unauthenticated message that closes a connection (e.g.,
TCP FIN) does not indicate revocation of consent. Thus, an endpoint
receiving an unauthenticated end-of-session message SHOULD continue
sending media (over connectionless transport) or attempt to re-
establish the connection (over connection-oriented transport) until
consent expires or it receives an authenticated message revoking
consent.
5. Connection Liveness 5. Connection Liveness
A connection is considered "live" if packets are received from a A connection is considered "live" if packets are received from a
remote endpoint within an application-dependent period. An remote endpoint within an application-dependent period. An
application can request a notification when there are no packets application can request a notification when there are no packets
received for a certain period (configurable). received for a certain period (configurable).
Similarly, if packets haven't been received within a certain period, Similarly, if packets haven't been received within a certain period,
an application can request a consent check (heartbeat) be generated. an application can request a consent check (heartbeat) be generated.
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rtcweb-qos-00 (work in progress), April 2014. rtcweb-qos-00 (work in progress), April 2014.
[RFC3830] Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K. [RFC3830] Arkko, J., Carrara, E., Lindholm, F., Naslund, M., and K.
Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830, Norrman, "MIKEY: Multimedia Internet KEYing", RFC 3830,
August 2004. August 2004.
[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, July 2006. Streams", RFC 4568, July 2006.
Appendix A. Example Implementation
This section describes one possible implementation algorithm of
consent. This section is non-normative and provided for reference
only.
The solution uses three values:
1. A consent timer, Tc, whose value is set to 30 seconds.
2. A packet receipt timer, Tr, whose value is determined by the
application. Tr can be greater than 1 but less than 30 seconds
and has a default value of 5 seconds.
3. A consent timeout, Tf, which is how many seconds elapse without a
consent response before the browser ceases transmission of media.
Its value is be 30 seconds or less.
4. A retransmission Timer, Tret, whose value is determined by the
RTT of a given path. The duration of this timer is set to 1.5
times of (500 ms or the smoothened round-trip time (from previous
consent freshness checks or RTP round-trip time)), whichever is
less.
A WebRTC browser performs a combined consent freshness and session
liveness test using STUN request/response as described below:
Every Tc seconds, the WebRTC browser sends a STUN Binding Request to
the peer. The difference from ICE connectivity check is that there
is no exponential back off for retransmissions.
If a valid STUN Binding Response is received, the consent timer is
reset to the time of receiving the response and fires again Tc
seconds later.
If a valid STUN Binding Response is not received after Tret
milliseconds, the STUN Binding Request is retransmitted (with a new
Transaction ID). As long as a valid STUN Binding Response is not
received, this retransmission is repeated every Tret milliseconds
until Tf seconds have elapsed or a valid response is received. If no
valid response is received after Tf seconds, the WebRTC browser quits
transmitting traffic to this remote peer. The streams that are being
sent on a flow(5-tuple) for which a consent has failed will be
stopped. If the default value of Tf is 30 seconds then media
transmission will stop Consent (Tf) expires.
Authors' Addresses Authors' Addresses
Muthu Arul Mozhi Perumal Muthu Arul Mozhi Perumal
Cisco Systems Cisco Systems
Cessna Business Park Cessna Business Park
Sarjapur-Marathahalli Outer Ring Road Sarjapur-Marathahalli Outer Ring Road
Bangalore, Karnataka 560103 Bangalore, Karnataka 560103
India India
Email: mperumal@cisco.com Email: mperumal@cisco.com
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