draft-ietf-httpbis-http2-encryption-10.txt   draft-ietf-httpbis-http2-encryption-11.txt 
HTTP Working Group M. Nottingham HTTP Working Group M. Nottingham
Internet-Draft Internet-Draft
Intended status: Experimental M. Thomson Intended status: Experimental M. Thomson
Expires: August 4, 2017 Mozilla Expires: September 18, 2017 Mozilla
January 31, 2017 March 17, 2017
Opportunistic Security for HTTP Opportunistic Security for HTTP/2
draft-ietf-httpbis-http2-encryption-10 draft-ietf-httpbis-http2-encryption-11
Abstract Abstract
This document describes how "http" URIs can be accessed using This document describes how "http" URIs can be accessed using
Transport Layer Security (TLS) to mitigate pervasive monitoring Transport Layer Security (TLS) and HTTP/2 to mitigate pervasive
attacks. monitoring attacks. This mechanism not a replacement for "https"
URIs; it is vulnerable to active attacks.
Note to Readers
Discussion of this draft takes place on the HTTP working group
mailing list (ietf-http-wg@w3.org), which is archived at
https://lists.w3.org/Archives/Public/ietf-http-wg/ .
Working Group information can be found at http://httpwg.github.io/ ;
source code and issues list for this draft can be found at
https://github.com/httpwg/http-extensions/labels/opp-sec .
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 August 4, 2017. This Internet-Draft will expire on September 18, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 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
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publication of this document. Please review these documents publication of this document. Please review these documents
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to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
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
1.1. Goals and Non-Goals . . . . . . . . . . . . . . . . . . . 3 1.1. Goals and Non-Goals . . . . . . . . . . . . . . . . . . . 2
1.2. Notational Conventions . . . . . . . . . . . . . . . . . 3 1.2. Notational Conventions . . . . . . . . . . . . . . . . . 3
2. Using HTTP URIs over TLS . . . . . . . . . . . . . . . . . . 3 2. Using HTTP URIs over TLS . . . . . . . . . . . . . . . . . . 3
2.1. Alternative Server Opt-In . . . . . . . . . . . . . . . . 4 2.1. Alternative Server Opt-In . . . . . . . . . . . . . . . . 4
2.2. Interaction with "https" URIs . . . . . . . . . . . . . . 5 2.2. Interaction with "https" URIs . . . . . . . . . . . . . . 5
2.3. The "http-opportunistic" well-known URI . . . . . . . . . 5 2.3. The "http-opportunistic" well-known URI . . . . . . . . . 5
3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6
4.1. Security Indicators . . . . . . . . . . . . . . . . . . . 6 4.1. Security Indicators . . . . . . . . . . . . . . . . . . . 6
4.2. Downgrade Attacks . . . . . . . . . . . . . . . . . . . . 7 4.2. Downgrade Attacks . . . . . . . . . . . . . . . . . . . . 6
4.3. Privacy Considerations . . . . . . . . . . . . . . . . . 7 4.3. Privacy Considerations . . . . . . . . . . . . . . . . . 6
4.4. Confusion Regarding Request Scheme . . . . . . . . . . . 7 4.4. Confusion Regarding Request Scheme . . . . . . . . . . . 7
4.5. Server Controls . . . . . . . . . . . . . . . . . . . . . 7 4.5. Server Controls . . . . . . . . . . . . . . . . . . . . . 7
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.1. Normative References . . . . . . . . . . . . . . . . . . 8 5.1. Normative References . . . . . . . . . . . . . . . . . . 7
5.2. Informative References . . . . . . . . . . . . . . . . . 9 5.2. Informative References . . . . . . . . . . . . . . . . . 8
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction 1. Introduction
This document describes a use of HTTP Alternative Services [RFC7838] This document describes a use of HTTP Alternative Services [RFC7838]
to decouple the URI scheme from the use and configuration of to decouple the URI scheme from the use and configuration of
underlying encryption, allowing a "http" URI [RFC7230] to be accessed underlying encryption. It allows an "http" URI to be accessed using
using Transport Layer Security (TLS) [RFC5246] opportunistically. HTTP/2 [RFC7230] and Transport Layer Security (TLS) [RFC5246] with
Opportunistic Security [RFC7435].
Serving "https" URIs requires avoiding Mixed Content This document describes a usage model whereby sites can serve "http"
[W3C.CR-mixed-content-20160802], which is problematic in many URIs over TLS, thereby avoiding the problem of serving Mixed Content
deployments. This document describes a usage model whereby sites can (described in [W3C.CR-mixed-content-20160802]) while still providing
serve "http" URIs over TLS, thereby avoiding these issues, while protection against passive attacks.
still providing protection against passive attacks.
Opportunistic Security [RFC7435] does not provide the same guarantees Opportunistic Security does not provide the same guarantees as using
as using TLS with "https" URIs; it is vulnerable to active attacks, TLS with "https" URIs, because it is vulnerable to active attacks,
and does not change the security context of the connection. and does not change the security context of the connection.
Normally, users will not be able to tell that it is in use (i.e., Normally, users will not be able to tell that it is in use (i.e.,
there will be no "lock icon"). there will be no "lock icon").
1.1. Goals and Non-Goals 1.1. Goals and Non-Goals
The immediate goal is to make the use of HTTP more robust in the face The immediate goal is to make the use of HTTP more robust in the face
of pervasive passive monitoring [RFC7258]. of pervasive passive monitoring [RFC7258].
A secondary (but significant) goal is to provide for ease of A secondary (but significant) goal is to provide for ease of
implementation, deployment and operation. This mechanism is expected implementation, deployment and operation. This mechanism is expected
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The immediate goal is to make the use of HTTP more robust in the face The immediate goal is to make the use of HTTP more robust in the face
of pervasive passive monitoring [RFC7258]. of pervasive passive monitoring [RFC7258].
A secondary (but significant) goal is to provide for ease of A secondary (but significant) goal is to provide for ease of
implementation, deployment and operation. This mechanism is expected implementation, deployment and operation. This mechanism is expected
to have a minimal impact upon performance, and require a trivial to have a minimal impact upon performance, and require a trivial
administrative effort to configure. administrative effort to configure.
Preventing active attacks (such as a Man-in-the-Middle) is a non-goal Preventing active attacks (such as a Man-in-the-Middle) is a non-goal
for this specification. Furthermore, this specification is not for this specification. Furthermore, this specification is not
intended to replace or offer an alternative to "https", since it both intended to replace or offer an alternative to "https", since "https"
prevents active attacks and invokes a more stringent security model both prevents active attacks and invokes a more stringent security
in most clients. model in most clients.
1.2. Notational Conventions 1.2. Notational Conventions
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].
2. Using HTTP URIs over TLS 2. Using HTTP URIs over TLS
An origin server that supports the resolution of "http" URIs can An origin server that supports the resolution of "http" URIs can
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It is possible that the server might become confused about whether It is possible that the server might become confused about whether
requests' URLs have a "http" or "https" scheme, for various reasons; requests' URLs have a "http" or "https" scheme, for various reasons;
see Section 4.4. To ensure that the alternative service has opted see Section 4.4. To ensure that the alternative service has opted
into serving "http" URLs over TLS, clients are required to perform into serving "http" URLs over TLS, clients are required to perform
additional checks before directing "http" requests to it. additional checks before directing "http" requests to it.
Clients MUST NOT send "http" requests over a secured connection, Clients MUST NOT send "http" requests over a secured connection,
unless the chosen alternative service presents a certificate that is unless the chosen alternative service presents a certificate that is
valid for the origin as defined in [RFC2818]. Using an authenticated valid for the origin as defined in [RFC2818]. Using an authenticated
alternative service establishes "reasonable assurances" for the alternative service establishes "reasonable assurances" for the
purposes of {RFC7838}}. In addition to authenticating the server, purposes of [RFC7838]. In addition to authenticating the server, the
the client MUST have obtained a valid http-opportunistic response for client MUST have obtained a valid http-opportunistic response for an
an origin (as per Section 2.3) using the authenticated connection. origin (as per Section 2.3) using the authenticated connection. An
An exception to the latter restriction is made for requests for the exception to the latter restriction is made for requests for the
"http-opportunistic" well-known URI. "http-opportunistic" well-known URI.
For example, assuming the following request is made over a TLS For example, assuming the following request is made over a TLS
connection that is successfully authenticated for those origins, the connection that is successfully authenticated for those origins, the
following request/response pair would allow requests for the origins following request/response pair would allow requests for the origins
"http://www.example.com" or "http://example.com" to be sent using a "http://www.example.com" or "http://example.com" to be sent using a
secured connection: secured connection:
HEADERS HEADERS
+ END_STREAM + END_STREAM
+ END_HEADERS + END_HEADERS
:method = GET :method = GET
:scheme = http :scheme = http
:authority = example.com
:path = /.well-known/http-opportunistic :path = /.well-known/http-opportunistic
host: example.com
HEADERS HEADERS
:status = 200 :status = 200
content-type = application/json content-type = application/json
DATA DATA
+ END_STREAM + END_STREAM
[ "http://www.example.com", "http://example.com" ] [ "http://www.example.com", "http://example.com" ]
Though this document describes multiple origins, this is only for Though this document describes multiple origins, this is only for
operational convenience. Only a request made to an origin (over an operational convenience. Only a request made to an origin (over an
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o Change Controller: IETF o Change Controller: IETF
o Specification Document(s): Section 2.3 of [this specification] o Specification Document(s): Section 2.3 of [this specification]
o Related Information: o Related Information:
4. Security Considerations 4. Security Considerations
4.1. Security Indicators 4.1. Security Indicators
User Agents MUST NOT provide any special security indicia when an User Agents MUST NOT provide any special security indicators when an
"http" resource is acquired using TLS. In particular, indicators "http" resource is acquired using TLS. In particular, indicators
that might suggest the same level of security as "https" MUST NOT be that might suggest the same level of security as "https" MUST NOT be
used (e.g., a "lock device"). used (e.g., a "lock device").
4.2. Downgrade Attacks 4.2. Downgrade Attacks
A downgrade attack against the negotiation for TLS is possible. A downgrade attack against the negotiation for TLS is possible.
For example, because the "Alt-Svc" header field [RFC7838] likely For example, because the "Alt-Svc" header field [RFC7838] likely
appears in an unauthenticated and unencrypted channel, it is subject appears in an unauthenticated and unencrypted channel, it is subject
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HTTP/1.1), or it may be because how the server and application are HTTP/1.1), or it may be because how the server and application are
implemented (often, they are two separate entities, with a variety of implemented (often, they are two separate entities, with a variety of
possible interfaces between them). possible interfaces between them).
Any security decisions based upon this information could be misled by Any security decisions based upon this information could be misled by
the deployment of this specification, because it violates the the deployment of this specification, because it violates the
assumption that the use of TLS (or port 443) means that the client is assumption that the use of TLS (or port 443) means that the client is
accessing a HTTPS URI, and operating in the security context implied accessing a HTTPS URI, and operating in the security context implied
by HTTPS. by HTTPS.
Therefore, servers need to carefully examine the use of such signals Therefore, server implementers and administrators need to carefully
before deploying this specification. examine the use of such signals before deploying this specification.
4.5. Server Controls 4.5. Server Controls
This specification requires that a server send both an Alternative This specification requires that a server send both an Alternative
Service advertisement and host content in a well-known location to Service advertisement and host content in a well-known location to
send HTTP requests over TLS. Servers SHOULD take suitable measures send HTTP requests over TLS. Servers SHOULD take suitable measures
to ensure that the content of the well-known resource remains under to ensure that the content of the well-known resource remains under
their control. Likewise, because the Alt-Svc header field is used to their control. Likewise, because the Alt-Svc header field is used to
describe policies across an entire origin, servers SHOULD NOT permit describe policies across an entire origin, servers SHOULD NOT permit
user content to set or modify the value of this header. user content to set or modify the value of this header.
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