Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
draft-petithuguenin-behave-turn-uris-00
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7065.
|
|
|---|---|---|---|
| Authors | Marc Petit-Huguenin , Suhas Nandakumar , Gonzalo Salgueiro , Paul Jones | ||
| Last updated | 2012-02-02 | ||
| RFC stream | (None) | ||
| Formats | |||
| Reviews |
GENART Telechat review
(of
-07)
by Suresh Krishnan
Ready w/issues
GENART Last Call review
(of
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by Suresh Krishnan
Ready w/issues
|
||
| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
| RFC Editor Note | (None) | ||
| IESG | IESG state | Became RFC 7065 (Proposed Standard) | |
| Telechat date | (None) | ||
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| Send notices to | (None) |
draft-petithuguenin-behave-turn-uris-00
BEHAVE M. Petit-Huguenin
Internet-Draft Unaffiliated
Intended status: Standards Track S. Nandakumar
Expires: August 5, 2012 G. Salgueiro
P. Jones
Cisco Systems
February 2, 2012
Traversal Using Relays around NAT (TURN) Uniform Resource Identifiers
draft-petithuguenin-behave-turn-uris-00
Abstract
This document specifies the syntax of Uniform Resource Identifier
(URI) schemes for the Traversal Using Relays around NAT (TURN)
protocol. It defines two URI schemes that can be used to provision
the configuration values needed by the resolution mechanism defined
in [RFC5928].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. This document may not be modified,
and derivative works of it may not be created, except to format it
for publication as an RFC or to translate it into languages other
than English.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 5, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
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publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Syntax of a TURN or TURNS URI . . . . . . . . . . . . . . . . 4
3.1. URI Scheme Syntax . . . . . . . . . . . . . . . . . . . . 4
3.2. URI Scheme Semantics . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7
5.1. TURN URI Registration . . . . . . . . . . . . . . . . . . 7
5.2. TURNS URI Registration . . . . . . . . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . . 9
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 10
Appendix B. Release notes . . . . . . . . . . . . . . . . . . . . 11
B.1. Merge of draft-nandakumar-rtcweb-turn-uri-00 and
draft-petithuguenin-behave-turn-uri-bis-05 . . . . . . . . 11
B.2. Modifications between petithuguenin-05 and
petithuguenin-04 . . . . . . . . . . . . . . . . . . . . . 11
B.3. Modifications between petithuguenin-04 and
petithuguenin-03 . . . . . . . . . . . . . . . . . . . . . 12
B.4. Modifications between petithuguenin-03 and
petithuguenin-02 . . . . . . . . . . . . . . . . . . . . . 12
B.5. Modifications between petithuguenin-02 and
petithuguenin-01 . . . . . . . . . . . . . . . . . . . . . 12
B.6. Modifications between petithuguenin-01 and
petithuguenin-00 . . . . . . . . . . . . . . . . . . . . . 12
B.7. Design Notes . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12
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1. Introduction
This document specifies the syntax and semantics of the Uniform
Resource Identifier (URI) scheme for the Traversal Using Relays
around NAT (TURN) protocol.
The TURN protocol is a specification allowing hosts behind NAT to
control the operation of a relay server. The relay server allows
hosts to exchange packets with its peers. The peers themselves may
also be behind NATs. RFC 5766 [RFC5766] defines the specifics of the
TURN protocol.
The "turn/turns" URI scheme is used to designate a TURN server (also
known as a relay) on Internet hosts accessible using the TURN
protocol. With the advent of standards such as [WEBRTC], we
anticipate a plethora of endpoints and web applications to be able to
identify and communicate with such a TURN server to carry out the
TURN protocol. This also implies those endpoints and/or applications
to be provisioned with appropriate configuration required to identify
the TURN server. Having an inconsistent syntax has its drawbacks and
can result in non-interoperable solutions. It can result in
solutions that are ambiguous and have implementation limitations on
the different aspects of the syntax and alike. The "turn/turns" URI
scheme helps alleviate most of these issues by providing a consistent
way to describe, configure and exchange the information identifying a
TURN server. This would also prevent the shortcomings inherent with
encoding similar information in non-uniform syntaxes such as the ones
proposed in [WEBRTC], for example.
[RFC5928] defines a resolution mechanism to convert a secure flag, a
host name or IP address, an eventually empty port, and an eventually
empty transport to a list of IP address, port, and TURN transport
tuples.
To simplify the provisioning of TURN clients, this document defines a
TURN and a TURNS URI scheme that can carry the four components needed
for the resolution mechanism.
A reference implementation [REF-IMPL] is available.
2. Terminology
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].
"SHOULD", "SHOULD NOT", "RECOMMENDED", and "NOT RECOMMENDED" are
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appropriate when valid exceptions to a general requirement are known
to exist or appear to exist, and it is infeasible or impractical to
enumerate all of them. However, they should not be interpreted as
permitting implementors to fail to implement the general requirement
when such failure would result in interoperability failure.
3. Syntax of a TURN or TURNS URI
3.1. URI Scheme Syntax
The "turn" URI takes the following form (the syntax below is non-
normative):
turn:<userinfo>@<host>:<port>
turns:<userinfo>@<host>:<port>
Note that <userinfo> with the "@" (at) sign character, as well as the
<port> part and the preceding ":" (colon) character, is OPTIONAL.
A TURN/TURNS URI has the following formal ABNF syntax [RFC5234]:
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turnURI = scheme ":" [ userinfo "@" ] turn-host
[ ":" turn-port ] [ "?transport=" transport ]
scheme = "turn" / "turns"
userinfo = user [ ":" password ]
user = 1*(%x21-24 / %x26-39 / %x3B-3F / %x41-7F
/ escaped)
; The symbols "%", ":", "@", and symbols
; with a character value below 0x21 may
; be represented as escaped sequences.
password = 1*(%x21-24 / %x26-3F / %x41-7F / escaped)
; The symbols "%", "@", and symbols with
; a character value below 0x21 may be
; represented as escaped sequences.
transport = "udp" / "tcp" / transport-ext
transport-ext = 1*unreserved
turn-host = IP-literal / IPv4address / reg-name
turn-port = *DIGIT
IP-literal = "[" ( IPv6address / IPvFuture ) "]"
IPvFuture = "v" 1*HEXDIG "." 1*( unreserved / sub-delims / ":" )
IPv6address = 6( h16 ":" ) ls32
/ "::" 5( h16 ":" ) ls32
/ [ h16 ] "::" 4( h16 ":" ) ls32
/ [ *1( h16 ":" ) h16 ] "::" 3( h16 ":" ) ls32
/ [ *2( h16 ":" ) h16 ] "::" 2( h16 ":" ) ls32
/ [ *3( h16 ":" ) h16 ] "::" h16 ":" ls32
/ [ *4( h16 ":" ) h16 ] "::" ls32
/ [ *5( h16 ":" ) h16 ] "::" h16
/ [ *6( h16 ":" ) h16 ] "::"
h16 = 1*4HEXDIG
ls32 = ( h16 ":" h16 ) / IPv4address
IPv4address = dec-octet "." dec-octet "." dec-octet "." dec-octet
dec-octet = DIGIT ; 0-9
/ %x31-39 DIGIT ; 10-99
/ "1" 2DIGIT ; 100-199
/ "2" %x30-34 DIGIT ; 200-249
/ "25" %x30-35 ; 250-255
reg-name = *( unreserved / pct-encoded / sub-delims )
escaped = "%" HEXDIG HEXDIG
<unreserved>, <sub-delims>, and <pct-encoded> are specified in
[RFC3986].
The <host>, <port> and <transport> components are passed without
modification to the [RFC5928] algorithm. <secure> is set to false if
<scheme> is equal to "turn" and set to true if <scheme> is equal to
"turns" and passed to the [RFC5928] algorithm with the other
components. The core rules <ALPHA>, <DIGIT> and <HEXDIGIT> are used
as described in Appendix B of RFC 5234 [RFC5234].
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The eventual <user> and <password> components are used as input for
the TURN [RFC5766] protocol itself.
3.2. URI Scheme Semantics
The TURN protocol supports sending messages over UDP, TCP or TLS-
over-TCP. The "turns" URI scheme SHALL be used when TURN is run over
TLS-over-TCP (or in the future DTLS-over-UDP) and the "turn" scheme
SHALL be used otherwise.
The required <host> part of the "turn" URI denotes the TURN server
host.
The <userinfo> part identifies the credentials required for the long-
term credential mechanism as described in the section 10.2 of RFC
5389 [RFC5389].
The <port> part, if present, denotes the port on which the TURN
server is awaiting connection requests. If it is absent, the default
port SHALL be 3478 for both UDP and TCP. The default port for TURN
over TLS SHALL be 5349.
The <userinfo> part specifies the username and password. Both the
<user> and <password> values are UTF-8 encoded and escaped as per
section 2.5 of RFC 3986 [RFC3986].
4. Security Considerations
Security considerations for the resolution mechanism are discussed in
[RFC5928].
As described in Section 3.2.1 of STD 66 [RFC3986], having
authentication information (specifically passwords) in a URI means
that the URI must be handled carefully:
The passing of authentication information in clear text has proven
to be a security risk in almost every case where it has been used.
Section 3.2.1 contains advice on handling URI that contain passwords
in the userinfo portion. Implementations of this specification MUST
implement that advice.
Specifically if a URI that contains credentials leaks, then it would
allow an attacker to use the TURN server which is referenced by the
URI. Such an attack has two major impacts. First, it uses up the
operator's bandwidth. Second, if the operator bills the user for
TURN server usage, then it may expose the user to costs incurred by
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the attacker. However, the attacker never obtains the user's private
information, nor does this attack allow for traffic amplification.
The expected use environment mitigates to some degree concerns about
TURN URIs compared to other URIs, such as HTTPS. First, users do not
dereference TURN URIs directly. Instead, they are passed to the TURN
stack. Thus, concerns about confusion or leakage due to the URI
being displayed to the user are significantly reduced; indeed the URI
need never be available to the user at all.
One of the primary use cases for a TURN URI with credentials is
WebRTC. In this case, a web server will be offering a calling
service and may have an associated TURN server it can use. In this
case, the browser will need to use the TURN server and the browser
has no long term or preexisting relationship with the TURN server.
The web server needs to provide some credential to the client which
it can use to access the TURN server. Since TURN authentication is
via username and password, this implies that the credential is a
username/password pair. While this must be transmitted securely
(i.e., over HTTPS), the security properties are the same whether the
password is carried separately or is part of the URL. Moreover,
because the web server and TURN servers can cooperate, a new password
can be issued for every call, making short-term credentials feasible
and thus significantly mitigating the risk.
If a TURN URI is transferred between hosts, it MUST be done over a
protocol that provides confidentiality such as HTTPS [RFC2818]. It
is RECOMMENDED that the credential only be valid for a single call
and preferably for no more than one day. That "preferably" is bad.
5. IANA Considerations
This section contains the registration information for the "turn" and
"turns" URI Schemes (in accordance with [RFC4395]).
5.1. TURN URI Registration
URI scheme name: turn
Status: permanent
URI scheme syntax: See Section 3.
URI scheme semantics: See [RFC5928].
Encoding considerations: There are no encoding considerations beyond
those in [RFC3986].
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Applications/protocols that use this URI scheme name:
The "turn" URI scheme is intended to be used by applications that
might need access to a TURN server.
Interoperability considerations: N/A
Security considerations: See Section 4.
Contact: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
References: RFCXXXX
[[NOTE TO RFC EDITOR: Please change XXXX to the number assigned to
this specification, and remove this paragraph on publication.]]
5.2. TURNS URI Registration
URI scheme name: turns
Status: permanent
URI scheme syntax: See Section 3.
URI scheme semantics: See [RFC5928].
Encoding considerations: There are no encoding considerations beyond
those in [RFC3986].
Applications/protocols that use this URI scheme name:
The "turns" URI scheme is intended to be used by applications that
might need access to a TURN server over a secure connection.
Interoperability considerations: N/A
Security considerations: See Section 4.
Contact: Marc Petit-Huguenin <petithug@acm.org>
Author/Change controller: The IESG
References: RFCXXXX
[[NOTE TO RFC EDITOR: Please change XXXX to the number assigned to
this specification, and remove this paragraph on publication.]]
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6. Acknowledgements
Thanks to Margaret Wasserman, Magnus Westerlund, Juergen
Schoenwaelder, Sean Turner, Ted Hardie, Dave Thaler, Alfred E.
Heggestad, Eilon Yardeni, Dan Wing, Alfred Hoenes, and Jim Kleck for
their comments, suggestions and questions that helped to improve the
draft-petithuguenin-behave-turn-uri-bis document.
Many thanks to Cullen Jennings for his detailed review and thoughtful
comments on the draft-nandakumar-rtcweb-turn-uri document.
The <turn-port> and <turn-host> ABNF productions have been copied
from the <port> and <host> ABNF productions from [RFC3986].
This document was written with the xml2rfc tool described in
[RFC2629].
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC5234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234, January 2008.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, April 2010.
[RFC5928] Petit-Huguenin, M., "Traversal Using Relays around NAT
(TURN) Resolution Mechanism", RFC 5928, August 2010.
7.2. Informative References
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
June 1999.
[RFC4395] Hansen, T., Hardie, T., and L. Masinter, "Guidelines and
Registration Procedures for New URI Schemes", BCP 35,
RFC 4395, February 2006.
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[RFC5389] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing,
"Session Traversal Utilities for NAT (STUN)", RFC 5389,
October 2008.
[RFC5769] Denis-Courmont, R., "Test Vectors for Session Traversal
Utilities for NAT (STUN)", RFC 5769, April 2010.
[WEBRTC] W3C, "WebRTC 1.0: Real-time Communication Between
Browsers".
<http://dev.w3.org/2011/webrtc/editor/webrtc.html>.
[REF-IMPL]
Petit-Huguenin, MPH., "Reference Implementation of TURN
resolver and TURN URI parser".
<http://debian.implementers.org/stable/source/
turnuri.tar.gz>.
Appendix A. Examples
Table 1 shows how the <secure>, <port> and <transport> components are
populated from various URIs. For all these examples, the <host>
component is populated with "example.org".
+---------------------------------+----------+--------+-------------+
| URI | <secure> | <port> | <transport> |
+---------------------------------+----------+--------+-------------+
| turn:example.org | false | | |
| turn:user:pwd@example.org | false | | |
| turns:example.org | true | | |
| turns:user:pwd@example.org | true | | |
| turn:example.org:8000 | false | 8000 | |
| turn:example.org?transport=udp | false | | UDP |
| turn:example.org?transport=tcp | false | | TCP |
| turns:example.org?transport=tcp | true | | TLS |
+---------------------------------+----------+--------+-------------+
Table 1
Table 2 shows how the <username>, <password> and <host> components
are populated from various URIs. For all the examples, the secure
component is populated with false and the port and transport
components are empty.
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+---------------------------+------------+------------+-------------+
| URI | <username> | <password> | <host> |
+---------------------------+------------+------------+-------------+
| turn:example.org | | | example.org |
| turn:192.0.2.1 | | | 192.0.2.1 |
| turn:[2001:DB8::1] | | | 2001:DB8::1 |
| turn:user@example.org | user | | example.org |
| turn:user:pwd@example.org | user | pwd | example.org |
+---------------------------+------------+------------+-------------+
Table 2
The following example produces the username and password used as
example in section 2.4 of [RFC5769]:
turn:%E3%83%9E%E3%83%88%E3%83%AA%E3%83%83%E3%82%AF%E3%82%B9:The%C2%
ADM%C2%AAtr%E2%85%A8@example.org
Appendix B. Release notes
This section must be removed before publication as an RFC.
B.1. Merge of draft-nandakumar-rtcweb-turn-uri-00 and
draft-petithuguenin-behave-turn-uri-bis-05
o Changed author list.
o Draft is now standard track.
o Merged abstract, introduction, acknowledgement and security
sections.
o Added two introductory paragraphs to the beginning iof the
introduction.
o Took Section 3 and divided it into Section 3.1 URI Scheme Syntax
and Section 3.2 URI Scheme Semantics.
o Explained that most components are passed as is to RFC 5928.
o Added username and password in ABNF.
o Added RFC 5389 as reference.
o Added examples.
o Updated design notes.
o Various minor nits and grammatical issues fixed.
B.2. Modifications between petithuguenin-05 and petithuguenin-04
o Nits.
o Fixed schemes registration.
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B.3. Modifications between petithuguenin-04 and petithuguenin-03
o Fixed references code link.
B.4. Modifications between petithuguenin-03 and petithuguenin-02
o Updated RFC references.
B.5. Modifications between petithuguenin-02 and petithuguenin-01
o Nits.
B.6. Modifications between petithuguenin-01 and petithuguenin-00
o Shorten I-D references.
B.7. Design Notes
o As discussed in Dublin, there is no generic parameters in the URI
to prevent compatibity issues.
Authors' Addresses
Marc Petit-Huguenin
Unaffiliated
Email: petithug@acm.org
Suhas Nandakumar
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
US
Email: snandaku@cisco.com
Gonzalo Salgueiro
Cisco Systems
7200-12 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: gsalguei@cisco.com
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Paul E. Jones
Cisco Systems
7025 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: paulej@packetizer.com
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