draft-ietf-httpbis-tunnel-protocol-04.txt   draft-ietf-httpbis-tunnel-protocol-05.txt 
HTTP Working Group A. Hutton HTTP Working Group A. Hutton
Internet-Draft Unify Internet-Draft Unify
Intended status: Standards Track J. Uberti Intended status: Standards Track J. Uberti
Expires: November 21, 2015 Google Expires: December 13, 2015 Google
M. Thomson M. Thomson
Mozilla Mozilla
May 20, 2015 June 11, 2015
The ALPN HTTP Header Field The ALPN HTTP Header Field
draft-ietf-httpbis-tunnel-protocol-04 draft-ietf-httpbis-tunnel-protocol-05
Abstract Abstract
This specification allows HTTP CONNECT requests to indicate what This specification allows HTTP CONNECT requests to indicate what
protocol will be used within the tunnel once established, using the protocol is intended to be used within the tunnel once established,
ALPN header field. using the ALPN header field.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on November 21, 2015. This Internet-Draft will expire on December 13, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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
skipping to change at page 2, line 16 skipping to change at page 2, line 16
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. The ALPN HTTP Header Field . . . . . . . . . . . . . . . . . 3 2. The ALPN HTTP Header Field . . . . . . . . . . . . . . . . . 3
2.1. Header Field Values . . . . . . . . . . . . . . . . . . . 3 2.1. Header Field Values . . . . . . . . . . . . . . . . . . . 3
2.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Syntax . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.3. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Normative References . . . . . . . . . . . . . . . . . . 5 5.1. Normative References . . . . . . . . . . . . . . . . . . 6
5.2. Informative References . . . . . . . . . . . . . . . . . 6 5.2. Informative References . . . . . . . . . . . . . . . . . 6
5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.3. URIs . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction 1. Introduction
The HTTP CONNECT method (Section 4.3.6 of [RFC7231]) requests that The HTTP CONNECT method (Section 4.3.6 of [RFC7231]) requests that
the recipient establish a tunnel to the identified origin server and the recipient establish a tunnel to the identified origin server and
thereafter forward packets, in both directions, until the tunnel is thereafter forward packets, in both directions, until the tunnel is
closed. Such tunnels are commonly used to create end-to-end virtual closed. Such tunnels are commonly used to create end-to-end virtual
connections, through one or more proxies. connections, through one or more proxies.
The HTTP ALPN header field identifies the protocol that will be used The HTTP ALPN header field identifies the protocol or protocols that
within the tunnel, using the Application Layer Protocol Negotiation the client intends to use within a tunnel that is established using
CONNECT. This uses the Application Layer Protocol Negotiation
identifier (ALPN, [RFC7301]). identifier (ALPN, [RFC7301]).
When the CONNECT method is used to establish a tunnel, the ALPN For a tunnel that is then secured using TLS [RFC5246], the header
header field can be used to identify the protocol that the client field carries the same application protocol label as will be carried
intends to use with that tunnel. For a tunnel that is then secured within the TLS handshake [RFC7301]. If there are multiple possible
using TLS [RFC5246], the header field carries the same application application protocols, all of those application protocols are
protocol label as will be carried within the TLS handshake. If there indicated.
are multiple possible application protocols, all of those application
protocols are indicated.
The ALPN header field carries an indication of client intent only. The ALPN header field carries an indication of client intent only.
An ALPN identifier is used here only to identify the application An ALPN identifier is used here only to identify the application
protocol or suite of protocols that the client intends to use in the protocol or suite of protocols that the client intends to use in the
tunnel. No negotiation takes place using this header field. In TLS, tunnel. No negotiation takes place using this header field. In TLS,
the final choice of application protocol is made by the server from the final choice of application protocol is made by the server from
the set of choices presented by the client. Other substrates could the set of choices presented by the client. Other substrates could
negotiate the application protocol differently. negotiate the application protocol differently.
Proxies do not implement the tunneled protocol, though they might Proxies do not implement the tunneled protocol, though they might
skipping to change at page 3, line 16 skipping to change at page 3, line 16
1.1. Requirements Language 1.1. Requirements Language
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 RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
2. The ALPN HTTP Header Field 2. The ALPN HTTP Header Field
Clients include the ALPN header field in an HTTP CONNECT request to Clients include the ALPN header field in an HTTP CONNECT request to
indicate the application layer protocol that will be used within the indicate the application layer protocol that a client intends to use
tunnel, or the set of protocols that might be used within the tunnel. within the tunnel, or a set of protocols that might be used within
the tunnel.
2.1. Header Field Values 2.1. Header Field Values
Valid values for the protocol field are taken from the "Application- Valid values for the protocol field are taken from the "Application-
Layer Protocol Negotiation (ALPN) Protocol ID" registry ([1]) Layer Protocol Negotiation (ALPN) Protocol ID" registry ([1])
established by [RFC7301]. established by [RFC7301].
2.2. Syntax 2.2. Syntax
The ABNF (Augmented Backus-Naur Form) syntax for the ALPN header The ABNF (Augmented Backus-Naur Form) syntax for the ALPN header
field is given below. It is based on the Generic Grammar defined in field value is given below. It uses the syntax defined in
Section 2 of [RFC7230]. Section 1.2 of [RFC7230].
ALPN = "ALPN":" 1#protocol-id ALPN = 1#protocol-id
protocol-id = token ; percent-encoded ALPN protocol identifier protocol-id = token ; percent-encoded ALPN protocol identifier
ALPN protocol names are octet sequences with no additional ALPN protocol names are octet sequences with no additional
constraints on format. Octets not allowed in tokens ([RFC7230], constraints on format. Octets not allowed in tokens ([RFC7230],
Section 3.2.6) MUST be percent-encoded as per Section 2.1 of Section 3.2.6) MUST be percent-encoded as per Section 2.1 of
[RFC3986]. Consequently, the octet representing the percent [RFC3986]. Consequently, the octet representing the percent
character "%" (hex 25) MUST be percent-encoded as well. character "%" (hex 25) MUST be percent-encoded as well.
In order to have precisely one way to represent any ALPN protocol In order to have precisely one way to represent any ALPN protocol
name, the following additional constraints apply: name, the following additional constraints apply:
skipping to change at page 4, line 13 skipping to change at page 4, line 13
to match protocol identifiers. to match protocol identifiers.
For example: For example:
CONNECT www.example.com HTTP/1.1 CONNECT www.example.com HTTP/1.1
Host: www.example.com Host: www.example.com
ALPN: h2, http%2F1.1 ALPN: h2, http%2F1.1
2.3. Usage 2.3. Usage
For a CONNECT tunnel that conveys a TLS session that in turn When used in the ALPN header field, an ALPN identifier is used to
encapsulates another protocol, the value of the ALPN header field identify an entire application protocol stack, not a single protocol
contains the same list of ALPN identifiers that will be sent in the layer or component.
TLS ClientHello message [RFC7301].
For a CONNECT tunnel that conveys a protocol secured with TLS, the
value of the ALPN header field contains the same list of ALPN
identifiers that will be sent in the TLS ClientHello message
[RFC7301].
Where no protocol negotiation is expected to occur, such as in Where no protocol negotiation is expected to occur, such as in
protocols that do not use TLS, the ALPN header field contains a protocols that do not use TLS, the ALPN header field contains a
single ALPN Protocol Identifier corresponding to the application single ALPN Protocol Identifier corresponding to the application
protocol that is intended to be used. If an alternative form of protocol that is intended to be used. If an alternative form of
protocol negotiation is possible, the ALPN header field contains the protocol negotiation is possible, the ALPN header field contains the
set of protocols that might be negotiated. set of protocols that might be negotiated.
When used in the ALPN header field, the ALPN identifier and registry A proxy can use the value of the ALPN header field to more cleanly
are used to identify an entire application protocol stack, not a and efficiently reject requests for a CONNECT tunnel. Exposing
single protocol layer or component. protocol information at the HTTP layer allows a proxy to deny
requests earlier, with better error reporting (such as a 403 status
code). The ALPN header field can be falsified and is therefore not
sufficient basis for authorizing a request.
A proxy could attempt to inspect packets to determine the protocol in
use. This requires that the proxy understand each ALPN identifier.
Protocols like TLS could hide negotiated protocols, or protocol
negotiation details could change over time. Proxies SHOULD NOT break
a CONNECT tunnel solely on the basis of a failure to recognize the
protocol.
A proxy can use the ALPN header field value to change how it manages
or prioritizes connections.
3. IANA Considerations 3. IANA Considerations
HTTP header fields are registered within the "Permanent Message HTTP header fields are registered within the "Permanent Message
Header Field Names" registry maintained at [2]. This document Header Field Names" registry maintained at [2]. This document
defines and registers the ALPN header field, according to [RFC3864] defines and registers the ALPN header field, according to [RFC3864]
as follows: as follows:
Header Field Name: ALPN Header Field Name: ALPN
skipping to change at page 5, line 10 skipping to change at page 5, line 27
In case of using HTTP CONNECT to a TURN server ("Traversal Using In case of using HTTP CONNECT to a TURN server ("Traversal Using
Relays around NAT", [RFC5766]) the security considerations of Relays around NAT", [RFC5766]) the security considerations of
Section 4.3.6 of [RFC7231] apply. It states that there "are Section 4.3.6 of [RFC7231] apply. It states that there "are
significant risks in establishing a tunnel to arbitrary servers, significant risks in establishing a tunnel to arbitrary servers,
particularly when the destination is a well-known or reserved TCP particularly when the destination is a well-known or reserved TCP
port that is not intended for Web traffic. Proxies that support port that is not intended for Web traffic. Proxies that support
CONNECT SHOULD restrict its use to a limited set of known ports or a CONNECT SHOULD restrict its use to a limited set of known ports or a
configurable whitelist of safe request targets." configurable whitelist of safe request targets."
The ALPN header field described in this document is an OPTIONAL The ALPN header field described in this document is OPTIONAL.
header field. Clients and HTTP proxies could choose to not support Clients and HTTP proxies could choose to not support it and therefore
the header and therefore fail to provide it, or ignore it when either fail to provide it, or ignore it when present. If the header
present. If the header is not available or ignored, a proxy cannot field is not available or ignored, a proxy cannot identify the
identify the purpose of the tunnel and use this as input to any purpose of the tunnel and use this as input to any authorization
authorization decision regarding the tunnel. This is decision regarding the tunnel. This is indistinguishable from the
indistinguishable from the case where either client or proxy does not case where either client or proxy does not support the ALPN header
support the ALPN header field. field.
There is no confidentiality protection for the ALPN header field.
ALPN identifiers that might expose confidential or sensitive
information SHOULD NOT be sent, as described in Section 5 of
[RFC7301].
The value of the ALPN header field could be falsified by a client. The value of the ALPN header field could be falsified by a client.
If the data being sent through the tunnel is encrypted (for example, If the data being sent through the tunnel is encrypted (for example,
with TLS [RFC5246]), then the proxy might not be able to directly with TLS [RFC5246]), then the proxy might not be able to directly
inspect the data to verify that the claimed protocol is the one which inspect the data to verify that the claimed protocol is the one which
is actually being used, though a proxy might be able to perform is actually being used, though a proxy might be able to perform
traffic analysis [TRAFFIC]. A proxy therefore cannot rely on the traffic analysis [TRAFFIC]. A proxy therefore cannot rely on the
value of the ALPN header field as a policy input in all cases. value of the ALPN header field as a policy input in all cases.
5. References 5. References
5.1. Normative References 5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997, Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration [RFC3864] Klyne, G., Nottingham, M., and J. Mogul, "Registration
Procedures for Message Header Fields", BCP 90, RFC 3864, Procedures for Message Header Fields", BCP 90, RFC 3864,
September 2004, <http://www.rfc-editor.org/info/rfc3864>. DOI 10.17487/RFC3864, September 2004,
<http://www.rfc-editor.org/info/rfc3864>.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66, RFC Resource Identifier (URI): Generic Syntax", STD 66, RFC
3986, January 2005, 3986, DOI 10.17487/RFC3986, January 2005,
<http://www.rfc-editor.org/info/rfc3986>. <http://www.rfc-editor.org/info/rfc3986>.
[RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol [RFC7230] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Message Syntax and Routing", RFC 7230, June (HTTP/1.1): Message Syntax and Routing", RFC 7230, DOI
2014, <http://www.rfc-editor.org/info/rfc7230>. 10.17487/RFC7230, June 2014,
<http://www.rfc-editor.org/info/rfc7230>.
[RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol [RFC7231] Fielding, R. and J. Reschke, "Hypertext Transfer Protocol
(HTTP/1.1): Semantics and Content", RFC 7231, June 2014, (HTTP/1.1): Semantics and Content", RFC 7231, DOI
10.17487/RFC7231, June 2014,
<http://www.rfc-editor.org/info/rfc7231>. <http://www.rfc-editor.org/info/rfc7231>.
[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan, [RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol "Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, July 2014, Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
<http://www.rfc-editor.org/info/rfc7301>. July 2014, <http://www.rfc-editor.org/info/rfc7301>.
5.2. Informative References 5.2. Informative References
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008, (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>. <http://www.rfc-editor.org/info/rfc5246>.
[RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using [RFC5766] Mahy, R., Matthews, P., and J. Rosenberg, "Traversal Using
Relays around NAT (TURN): Relay Extensions to Session Relays around NAT (TURN): Relay Extensions to Session
Traversal Utilities for NAT (STUN)", RFC 5766, April 2010, Traversal Utilities for NAT (STUN)", RFC 5766, DOI
10.17487/RFC5766, April 2010,
<http://www.rfc-editor.org/info/rfc5766>. <http://www.rfc-editor.org/info/rfc5766>.
[TRAFFIC] Pironti, A., Strub, P-Y., and K. Bhargavan, "Website Users [TRAFFIC] Pironti, A., Strub, P-Y., and K. Bhargavan, "Website Users
by TLS Traffic Analysis: New Attacks and Effective by TLS Traffic Analysis: New Attacks and Effective
Countermeasures, Revision 1", 2012, Countermeasures, Revision 1", 2012,
<https://alfredo.pironti.eu/research/publications/full/ <https://alfredo.pironti.eu/research/publications/full/
identifying-website-users-tls-traffic-analysis-new- identifying-website-users-tls-traffic-analysis-new-
attacks-and-effective-counterme>. attacks-and-effective-counterme>.
5.3. URIs 5.3. URIs
 End of changes. 23 change blocks. 
49 lines changed or deleted 78 lines changed or added

This html diff was produced by rfcdiff 1.42. The latest version is available from http://tools.ietf.org/tools/rfcdiff/