< draft-ekwk-capport-rfc7710bis-01.txt   draft-ekwk-capport-rfc7710bis-02.txt >
Network Working Group W. Kumari Network Working Group W. Kumari
Internet-Draft Google Internet-Draft Google
Updates: 7710 (if approved) E. Kline Updates: 7710 (if approved) E. Kline
Intended status: Standards Track Loon Intended status: Standards Track Loon
Expires: July 19, 2019 January 15, 2019 Expires: September 12, 2019 March 11, 2019
Captive-Portal Identification in DHCP / RA Captive-Portal Identification in DHCP / RA
draft-ekwk-capport-rfc7710bis-01 draft-ekwk-capport-rfc7710bis-02
Abstract Abstract
In many environments offering short-term or temporary Internet access In many environments offering short-term or temporary Internet access
(such as coffee shops), it is common to start new connections in a (such as coffee shops), it is common to start new connections in a
captive portal mode. This highly restricts what the customer can do captive portal mode. This highly restricts what the customer can do
until the customer has authenticated. until the customer has authenticated.
This document describes a DHCP option (and a Router Advertisement This document describes a DHCP option (and a Router Advertisement
(RA) extension) to inform clients that they are behind some sort of (RA) extension) to inform clients that they are behind some sort of
skipping to change at page 1, line 48 skipping to change at page 1, line 48
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 July 19, 2019. This Internet-Draft will expire on September 12, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2019 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 29 skipping to change at page 2, line 29
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Notation . . . . . . . . . . . . . . . . . . 3
2. The Captive-Portal Option . . . . . . . . . . . . . . . . . . 3 2. The Captive-Portal Option . . . . . . . . . . . . . . . . . . 3
2.1. IPv4 DHCP Option . . . . . . . . . . . . . . . . . . . . 4 2.1. IPv4 DHCP Option . . . . . . . . . . . . . . . . . . . . 4
2.2. IPv6 DHCP Option . . . . . . . . . . . . . . . . . . . . 4 2.2. IPv6 DHCP Option . . . . . . . . . . . . . . . . . . . . 4
2.3. The Captive-Portal IPv6 RA Option . . . . . . . . . . . . 5 2.3. The Captive-Portal IPv6 RA Option . . . . . . . . . . . . 5
3. The Captive-Portal Link Relation Type . . . . . . . . . . . . 5 3. The Captive-Portal Link Relation Type . . . . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 4. Precedence of API URIs . . . . . . . . . . . . . . . . . . . 6
4.1. IETF params Registration . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
4.1.1. Registry name: Captive Portal Unrestricted Identifier 6 5.1. IETF params Registration . . . . . . . . . . . . . . . . 6
4.1.2. Registry name: Captive Portal API Link Relation Type 6 5.1.1. Registry name: Captive Portal Unrestricted Identifier 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 5.1.2. Registry name: Captive Portal API Link Relation Type 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7
7. Normative References . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 8 8. Normative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 Appendix A. Changes / Author Notes. . . . . . . . . . . . . . . 9
Appendix B. Differences from RFC 7710 . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
In many environments, users need to connect to a captive-portal In many environments, users need to connect to a captive-portal
device and agree to an Acceptable Use Policy (AUP) and / or provide device and agree to an Acceptable Use Policy (AUP) and / or provide
billing information before they can access the Internet. It is billing information before they can access the Internet. It is
anticipated that the IETF will work on a more fully featured protocol anticipated that the IETF will work on a more fully featured protocol
at some point, to ease interaction with Captive Portals. Regardless at some point, to ease interaction with Captive Portals. Regardless
of how that protocol operates, it is expected that this document will of how that protocol operates, it is expected that this document will
provide needed functionality because the client will need to know provide needed functionality because the client will need to know
skipping to change at page 3, line 43 skipping to change at page 3, line 47
DHCP, IPv6 RA). The captive portal operator should ensure that the DHCP, IPv6 RA). The captive portal operator should ensure that the
URIs handed out are equivalent to reduce the chance of operational URIs handed out are equivalent to reduce the chance of operational
problems. The maximum length of the URI that can be carried in IPv4 problems. The maximum length of the URI that can be carried in IPv4
DHCP is 255 bytes, so URIs longer than 255 bytes should not be used DHCP is 255 bytes, so URIs longer than 255 bytes should not be used
in IPv6 DHCP or IPv6 RA. in IPv6 DHCP or IPv6 RA.
In all variants of this option, the URI SHOULD be that of the captive In all variants of this option, the URI SHOULD be that of the captive
portal API endpoint, conforming to the recommendations for such URIs portal API endpoint, conforming to the recommendations for such URIs
[cite:API] (i.e. the URI SHOULD contain a DNS name and SHOULD [cite:API] (i.e. the URI SHOULD contain a DNS name and SHOULD
reference a secure transport, e.g. https). A captive portal MAY do reference a secure transport, e.g. https). A captive portal MAY do
content negotiation [citation?] and attempt to redirect clients content negotiation ([RFC7231] section 3.4) and attempt to redirect
querying without an explicit indication of support for the captive clients querying without an explicit indication of support for the
portal API content type (i.e. without application/capport+json listed captive portal API content type (i.e. without application/
explicitly anywhere within an Accepts header [citation]). In so capport+json listed explicitly anywhere within an Accept header vis.
doing, the captive portal SHOULD redirect the client to the value [RFC7231] section 5.3). In so doing, the captive portal SHOULD
associated with the "user-portal-url" API key. redirect the client to the value associated with the "user-portal-
url" API key.
The URI SHOULD NOT contain an IP address literal. The URI SHOULD NOT contain an IP address literal.
The URI parameter is not null terminated. The URI parameter is not null terminated.
Networks with no captive portals MAY explicitly indicate this Networks with no captive portals MAY explicitly indicate this
condition by using this option with the IANA-assigned URI for this condition by using this option with the IANA-assigned URI for this
purpose (see Section 4.1.1). Clients observing the URI value purpose (see Section 5.1.1). Clients observing the URI value
"urn:ietf:params:capport-unrestricted" MAY forego time-consuming "urn:ietf:params:capport-unrestricted" MAY forego time-consuming
forms of captive portal detection. forms of captive portal detection.
2.1. IPv4 DHCP Option 2.1. IPv4 DHCP Option
The format of the IPv4 Captive-Portal DHCP option is shown below. The format of the IPv4 Captive-Portal DHCP option is shown below.
Code Len Data Code Len Data
+------+------+------+------+------+-- --+-----+ +------+------+------+------+------+-- --+-----+
| code | len | URI ... | | code | len | URI ... |
skipping to change at page 5, line 46 skipping to change at page 6, line 5
HTTP intercept and redirection are used, a Link relation header HTTP intercept and redirection are used, a Link relation header
([RFC8288], Section 3.3) MAY be inserted to convey to a HTTP client ([RFC8288], Section 3.3) MAY be inserted to convey to a HTTP client
(user agent) the associated Captive Portal API URI. (user agent) the associated Captive Portal API URI.
HTTP user agents MUST ignore this link relation in any context other HTTP user agents MUST ignore this link relation in any context other
than when explicitly probing to detect the presence of a captive than when explicitly probing to detect the presence of a captive
portal. Failure to do so could allow an attacker to inject a Captive portal. Failure to do so could allow an attacker to inject a Captive
Portal API URI other than the correct URI for a given network or for Portal API URI other than the correct URI for a given network or for
networks where there is no captive portal present at all. networks where there is no captive portal present at all.
4. IANA Considerations 4. Precedence of API URIs
A device may learn about Captive Portal API URIs through more than
one of (or indeed all of) the above options. It is a network
configuration error if the learned URIs are not all identical.
However, if the URIs learned are not in fact all identical the
captive device MUST prioritize URIs learned from network provisioning
or configuration mechanisms before all other URIs. Specifically,
URIs learned via any of the options in Section 2 should take
precedence over any URI learned via a mechanism like the one
described in Section 3.
If the URIs learned via more than one option described in Section 2
are not all identical, this condition should be logged for the device
owner or administrator. URI precedence in this situation is not
specified by this document.
5. IANA Considerations
This document requests two new IETF URN protocol parameter This document requests two new IETF URN protocol parameter
([RFC3553]) entries. ([RFC3553]) entries.
Thanks IANA! Thanks IANA!
4.1. IETF params Registration 5.1. IETF params Registration
4.1.1. Registry name: Captive Portal Unrestricted Identifier 5.1.1. Registry name: Captive Portal Unrestricted Identifier
Registry name: Captive Portal Unrestricted Identifier Registry name: Captive Portal Unrestricted Identifier
URN: urn:ietf:params:capport-unrestricted URN: urn:ietf:params:capport-unrestricted
Specification: RFC TBD (this document) Specification: RFC TBD (this document)
Repository: RFC TBD (this document) Repository: RFC TBD (this document)
Index value: Only one value is defined (see URN above). No hierarchy Index value: Only one value is defined (see URN above). No hierarchy
is defined and therefore no sub-namespace registrations are possible. is defined and therefore no sub-namespace registrations are possible.
4.1.2. Registry name: Captive Portal API Link Relation Type 5.1.2. Registry name: Captive Portal API Link Relation Type
Registry name: Captive Portal API Link Relation Type Registry name: Captive Portal API Link Relation Type
URN: urn:ietf:params:capport-api URN: urn:ietf:params:capport-api
Specification: RFC TBD (this document) Specification: RFC TBD (this document)
Repository: RFC TBD (this document) Repository: RFC TBD (this document)
Index value: Only one value is defined (see URN above). No hierarchy Index value: Only one value is defined (see URN above). No hierarchy
is defined and therefore no sub-namespace registrations are possible. is defined and therefore no sub-namespace registrations are possible.
5. Security Considerations 6. Security Considerations
An attacker with the ability to inject DHCP messages could include An attacker with the ability to inject DHCP messages, RAs, or HTTP
this option and so force users to contact an address of his choosing. headers into cleartext HTTP communications could include an option or
As an attacker with this capability could simply list himself as the link relation from this document and so force users to contact an
default gateway (and so intercept all the victim's traffic); this address of his choosing. As an attacker with this capability could
does not provide them with significantly more capabilities, but simply list himself as the default gateway (and so intercept all the
because this document removes the need for interception, the attacker victim's traffic); this does not provide them with significantly more
may have an easier time performing the attack. As the operating capabilities, but because this document removes the need for
systems and application that make use of this information know that interception, the attacker may have an easier time performing the
they are connecting to a captive-portal device (as opposed to attack. As the operating systems and application that make use of
intercepted connections) they can render the page in a sandboxed this information know that they are connecting to a captive-portal
environment and take other precautions, such as clearly labeling the device (as opposed to intercepted connections) they can render the
page as untrusted. The means of sandboxing and user interface page in a sandboxed environment and take other precautions, such as
presenting this information is not covered in this document - by its clearly labeling the page as untrusted. The means of sandboxing and
nature it is implementation specific and best left to the application user interface presenting this information is not covered in this
and user interface designers. document - by its nature it is implementation specific and best left
to the application and user interface designers.
Devices and systems that automatically connect to an open network Devices and systems that automatically connect to an open network
could potentially be tracked using the techniques described in this could potentially be tracked using the techniques described in this
document (forcing the user to continually authenticate, or exposing document (forcing the user to continually authenticate, or exposing
their browser fingerprint). However, similar tracking can already be their browser fingerprint). However, similar tracking can already be
performed with the standard captive portal mechanisms, so this performed with the standard captive portal mechanisms, so this
technique does not give the attackers more capabilities. technique does not give the attackers more capabilities.
Captive portals are increasingly hijacking TLS connections to force Captive portals are increasingly hijacking TLS connections to force
browsers to talk to the portal. Providing the portal's URI via a browsers to talk to the portal. Providing the portal's URI via a
skipping to change at page 7, line 25 skipping to change at page 8, line 5
By simplifying the interaction with the captive portal systems, and By simplifying the interaction with the captive portal systems, and
doing away with the need for interception, we think that users will doing away with the need for interception, we think that users will
be less likely to disable useful security safeguards like DNSSEC be less likely to disable useful security safeguards like DNSSEC
validation, VPNs, etc. In addition, because the system knows that it validation, VPNs, etc. In addition, because the system knows that it
is behind a captive portal, it can know not to send cookies, is behind a captive portal, it can know not to send cookies,
credentials, etc. By handing out a URI using which is protected with credentials, etc. By handing out a URI using which is protected with
TLS, the captive portal operator can attempt to reassure the user TLS, the captive portal operator can attempt to reassure the user
that the captive portal is not malicious. that the captive portal is not malicious.
6. Acknowledgements 7. Acknowledgements
This document is a -bis of RFC7710. Thanks to all of the original This document is a -bis of RFC7710. Thanks to all of the original
authors (Warren Kumari, Olafur Gudmundsson, Paul Ebersman, Steve authors (Warren Kumari, Olafur Gudmundsson, Paul Ebersman, Steve
Sheng), and original contributors. Sheng), and original contributors.
Also thanks to the CAPPORT WG for all of the discussion and Also thanks to the CAPPORT WG for all of the discussion and
improvements. improvements.
7. Normative References 8. 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, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc- DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>. editor.org/info/rfc2119>.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol", [RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, DOI 10.17487/RFC2131, March 1997, RFC 2131, DOI 10.17487/RFC2131, March 1997,
<https://www.rfc-editor.org/info/rfc2131>. <https://www.rfc-editor.org/info/rfc2131>.
skipping to change at page 8, line 30 skipping to change at page 9, line 10
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
DOI 10.17487/RFC4861, September 2007, <https://www.rfc- DOI 10.17487/RFC4861, September 2007, <https://www.rfc-
editor.org/info/rfc4861>. editor.org/info/rfc4861>.
[RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and
S. Krishnan, "Guidelines for Creating New DHCPv6 Options", S. Krishnan, "Guidelines for Creating New DHCPv6 Options",
BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014,
<https://www.rfc-editor.org/info/rfc7227>. <https://www.rfc-editor.org/info/rfc7227>.
[RFC7231] Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
Protocol (HTTP/1.1): Semantics and Content", RFC 7231,
DOI 10.17487/RFC7231, June 2014, <https://www.rfc-
editor.org/info/rfc7231>.
[RFC7710] Kumari, W., Gudmundsson, O., Ebersman, P., and S. Sheng,
"Captive-Portal Identification Using DHCP or Router
Advertisements (RAs)", RFC 7710, DOI 10.17487/RFC7710,
December 2015, <https://www.rfc-editor.org/info/rfc7710>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288, [RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017, <https://www.rfc- DOI 10.17487/RFC8288, October 2017, <https://www.rfc-
editor.org/info/rfc8288>. editor.org/info/rfc8288>.
Appendix A. Changes / Author Notes. Appendix A. Changes / Author Notes.
[RFC Editor: Please remove this section before publication ] [RFC Editor: Please remove this section before publication ]
From initial to -00. From initial to -00.
o Import of RFC7710. o Import of RFC7710.
Appendix B. Differences from RFC 7710
This document incorporates the following differences from [RFC7710].
o Clarify that IP string literals are NOT RECOMMENDED.
o Clarify that the option URI SHOULD be that of the captive portal
API endpoint.
o Clarify that captive portals MAY do content negotiation.
o Added text about Captive Portal API URI precedence in the event of
a network configuration error.
o Added urn:ietf:params:capport-unrestricted URN.
o Added urn:ietf:params:capport-api URN.
Authors' Addresses Authors' Addresses
Warren Kumari Warren Kumari
Google Google
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
US US
Email: warren@kumari.net Email: warren@kumari.net
Erik Kline Erik Kline
Loon Loon
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
Mountain View, CA 94043 Mountain View, CA 94043
US US
Email: ek@google.com Email: ek@google.com
 End of changes. 18 change blocks. 
42 lines changed or deleted 92 lines changed or added

This html diff was produced by rfcdiff 1.48. The latest version is available from http://tools.ietf.org/tools/rfcdiff/