Internet DRAFT - draft-martinsen-ice-tls-candidates
draft-martinsen-ice-tls-candidates
ICE P. Martinsen
Internet-Draft N. Buckles
Intended status: Standards Track Cisco
Expires: July 24, 2017 January 20, 2017
TLS Candidates for ICE
draft-martinsen-ice-tls-candidates-00
Abstract
This document introduces TLS candidates to ICE.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on July 24, 2017.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Notational Conventions . . . . . . . . . . . . . . . . . . . 2
3. Overview of Operations . . . . . . . . . . . . . . . . . . . 2
4. ICE-TLS-Candidates . . . . . . . . . . . . . . . . . . . . . 3
5. Sending Packets . . . . . . . . . . . . . . . . . . . . . . . 3
6. HTTP Proxy . . . . . . . . . . . . . . . . . . . . . . . . . 4
7. RTCP Multiplexing . . . . . . . . . . . . . . . . . . . . . . 5
8. Compatibility . . . . . . . . . . . . . . . . . . . . . . . . 5
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
10. Security Considerations . . . . . . . . . . . . . . . . . . . 5
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
12. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
In use-cases where media is terminated by a public reachable server
it is desirable to be able to negotiate a TLS connection in addition
to UDP as described in ICEbis [I-D.ietf-ice-rfc5245bis] and TCP as
described in ICE-TCP [RFC6544]. This will increase the chances of
successfully traversing any firewall between the client and the
public server.
Due to the problems associated with p2p connections and TCP
(Synchronously opening up the two necessary pinholes at two different
NAT/FWs), this specification focuses on the use case where one side
is publicly reachable and runs ICE-lite.
2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
This specification uses terminology defined in ICEbis
[I-D.ietf-ice-rfc5245bis].
3. Overview of Operations
ICE performs connectivity checks between clients and servers. ICE
candidates are usually exchanged via SDP and connectivity checks are
performed on each candidate pair. In the scenario where the client
implements a full ICE stack and the server implements a ICE lite
stack. The client is in the ICE controlling role, so the client has
ultimate control over which candidate pair is selected.
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4. ICE-TLS-Candidates
The grammar for ICE candidates in SDP is described in ICEbis and ICE-
TCP. For TLS candidates, we update the grammar as follows:
transport = "UDP" / "TCP" / "TLS" / transport-extension
Candidate priority is calculated using the standard formula with UDP
having higher priority than TCP or TLS, and TCP having higher
priority than TLS.
Example ICE candidates from a client:
a=candidate:1 1 UDP 2113933823 10.19.1.236 20124 typ HOST
a=candidate:2 1 TCP 2113933567 10.19.1.236 20000 typ HOST
a=candidate:3 1 TLS 2113933322 10.19.1.236 20000 typ HOST \
fingerprint sha-1;XX:YY:ZZ
52:A7:60:90:B2:3E:79:43:08:77:F0:80:C6:14:E2:1B:87:16:B3:B1
Example ICE candidates from a server:
a=candidate:0 1 UDP 2130706431 23.253.251.168 33434 typ host
a=candidate:8 1 TCP 1962934271 23.253.251.168 33434 typ host tcptype
passive a=candidate:16 1 TLS 1459376510 23.253.251.168 443 typ host
\ tcptype passive fingerprint sha-1;XX:YY:ZZ
Note that the server TCP and TLS candidates are always marked as
passive indicating that the client always initiates the TCP
connection. For TLS candidates both the client and server MUST
include the fingerprint attribute that has the following syntax
largely borrowed from Comedia over TLS in SDP [RFC4572].
extension-att-name = "fingerprint"
extension-att-value = hash-func ";" fingerprint
hash-func = "sha-1" / "sha-224" / "sha-256" / token
fingerprint = 2UHEX *(":" 2UHEX)
The certificates exchanged as part of the TLS handshake should be
validated against the given fingerprint as a means of identifying the
remote TLS participant.
5. Sending Packets
Various types of packets (RTP, RTCP, SRTP, SRTCP, STUN, DTLS, BFCP)
are sent over the different transport types in different ways.
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When using UDP transport all packets except BFCP are sent directly
over UDP as individual UDP datagrams. BFCP packets are sent directly
over UDP when the BFCP m-line is not DTLS enabled. BFCP packets are
sent as DTLS payload when the m-line is DTLS enabled.
When using TCP transport all packets except BFCP are sent directly
over the TCP connection using RTP and RTCP over Connection-Oriented
Transport [RFC4571] framing. BFCP packets are sent using this
framing when the BFCP m-line is not DTLS enabled. BFCP packets are
sent as DTLS payload when the m-line is DTLS enabled.
When using TLS transport all packets except BFCP are sent as TLS
payload using rfc4571 framing. BFCP packets are sent using rfc4571
framing when the BFCP m-line is not DTLS enabled. BFCP packets are
sent as DTLS payload when the m-line is DTLS enabled.
In the case of SRTP/SRTCP and TLS, each packet will be double
encrypted. On the encryption side the SRTP/SRTCP encryption and
authentication is done first and the TLS encryption is done second.
On the decryption side, the TLS decryption is done first and the
SRTP/SRTCP decryption is done second.
When a media or application m-line is negotiated (in SDP) as using
DTLS, a DTLS handshake will be performed regardless of the chosen
transport type. In the case of a TLS transport, the DTLS packets
will be sent as TLS payload. This creates a slightly strange end
result of DTLS over TLS but this allows the system as a whole to
operate in the same manner regardless of the chosen transport type.
6. HTTP Proxy
Some firewalls will block arbitrary UDP, TCP, or TLS traffic, but
will allow TLS traffic via an HTTP proxy. When an HTTP proxy is
configured on the client (or host operating system) and TLS ICE
candidates have been exchanged between the client and server, then
the client should initiate an HTTP CONNECT to the proxy server before
sending TLS traffic.
The client provides the IP and TLS port of the server to the HTTP
proxy (in the form of a generated HTTP URL). It is quite likely that
the TLS port of the server must be 443 (standard HTTPS port) for this
operation to work. After the proxy server returns 200 the client may
send the TLS along the established TCP connection with the proxy
server and the TLS will be forwarded (intact) to the server. (There
is a wiki page at https://en.wikipedia.org/wiki/HTTP_tunnel, but no
real standards to point to).
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The use of an HTTP proxy is largely invisible to the server. The
server will see the IP address port used by the HTTP proxy instead of
the client, but this will be handled normally as part of ICE
processing.
7. RTCP Multiplexing
It is desirable (and in some cases required) that RTCP and RTP be
transmitted over the same port. This behavior is negotiated in SDP
as described in Multiplexing RTP and RTCP [RFC5761]. It is highly
recommended that all clients support rtcp-mux. Clients that do not
support rtcp-mux may not be able to use TLS and HTTP proxies for
connectivity.
8. Compatibility
TODO: How will this affect old clients?
9. IANA Considerations
SDP?
10. Security Considerations
The security considerations described in [I-D.ietf-ice-rfc5245bis]
are still valid. TODO: ANY TLS attacs we should care about? TODO:
SRTP? Do we need it even if we use TLS, yes probably. (Changing
paths and so on?)
11. Acknowledgements
12. Normative References
[I-D.ietf-ice-rfc5245bis]
Keranen, A., Holmberg, C., and J. Rosenberg, "Interactive
Connectivity Establishment (ICE): A Protocol for Network
Address Translator (NAT) Traversal", draft-ietf-ice-
rfc5245bis-08 (work in progress), December 2016.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC4571] Lazzaro, J., "Framing Real-time Transport Protocol (RTP)
and RTP Control Protocol (RTCP) Packets over Connection-
Oriented Transport", RFC 4571, DOI 10.17487/RFC4571, July
2006, <http://www.rfc-editor.org/info/rfc4571>.
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[RFC4572] Lennox, J., "Connection-Oriented Media Transport over the
Transport Layer Security (TLS) Protocol in the Session
Description Protocol (SDP)", RFC 4572, DOI 10.17487/
RFC4572, July 2006,
<http://www.rfc-editor.org/info/rfc4572>.
[RFC5761] Perkins, C. and M. Westerlund, "Multiplexing RTP Data and
Control Packets on a Single Port", RFC 5761, DOI 10.17487/
RFC5761, April 2010,
<http://www.rfc-editor.org/info/rfc5761>.
[RFC6544] Rosenberg, J., Keranen, A., Lowekamp, B., and A. Roach,
"TCP Candidates with Interactive Connectivity
Establishment (ICE)", RFC 6544, DOI 10.17487/RFC6544,
March 2012, <http://www.rfc-editor.org/info/rfc6544>.
Authors' Addresses
Paal-Erik Martinsen
Cisco Systems, Inc.
Philip Pedersens Vei 22
Lysaker, Akershus 1325
Norway
Email: palmarti@cisco.com
Nathan Buckles
Cisco Systems, Inc.
2250 East President George Bush Highway
Richardson, Texas 75082-3550
USA
Email: nbuckles@cisco.com
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