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Calendar Server Extension C. Daboo
Apple Computer
May 3, 2007
Calendar User Proxy Functionality in CalDAV
caldav-cu-proxy-02
Abstract
This specification defines an extension to CalDAV that makes it easy
for clients to setup and manage calendar user proxies, using the
WebDAV Access Control List extension as a basis.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.1. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3.2. Client . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. New features in CalDAV . . . . . . . . . . . . . . . . . . . . 4
5.1. Proxy Principal Resource . . . . . . . . . . . . . . . . . 4
5.2. Privilege Provisioning . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 9
Appendix B. Change History . . . . . . . . . . . . . . . . . . . 10
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
Daboo [Page 1]
CalDAV Proxy May 2007
1. Introduction
CalDAV [RFC4791] provides a way for calendar users to store calendar
data and exchange this data via scheduling operations. Based on the
WebDAV protocol [RFC2518], it also includes the ability to manage
access to calendar data via the WebDAV ACL extension [RFC3744].
It is often common for a calendar user to delegate some form of
responsibility for their calendar and schedules to another calendar
user (e.g., a boss allows an assistant to check a calendar or to send
and accept scheduling invites on his behalf). The user handling the
calendar data on behalf of someone else is often referred to as a
"calendar user proxy".
Whilst CalDAV does have fine-grained access control features that can
be used to setup complex sharing and management of calendars, often
the proxy behavior required is an "all-or-nothing" approach - i.e.
the proxy has access to all the calendars or to no calendars (in
which case they are of course not a proxy). So a simple way to
manage access to an entire set of calendars and scheduling ability
would be handy.
In addition, calendar user agents will often want to display to a
user who has proxy access to their calendars, or to whom they are
acting as a proxy. Again, CalDAV's access control discovery and
report features can be used to do that, but with fine-grained control
that exists, it can be hard to tell who is a "real" proxy as opposed
to someone just granted rights to some subset of calendars. Again, a
simple way to discover proxy information would be handy.
2. Conventions Used in This Document
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].
When XML element types in the namespace "DAV:" are referenced in this
document outside of the context of an XML fragment, the string "DAV:"
will be prefixed to the element type names.
When XML element types in the namespaces "DAV:" and
"urn:ietf:params:xml:ns:caldav" are referenced in this document
outside of the context of an XML fragment, the string "DAV:" and
"CALDAV:" will be prefixed to the element type names respectively.
The namespace "http://calendarserver.org/ns/" is used for XML
elements defined in this specification. When XML element types in
Daboo [Page 2]
CalDAV Proxy May 2007
this namespace are referenced in this document outside of the context
of an XML fragment, the string "CS:" will be prefixed to the element
type names respectively.
3. Overview
3.1. Server
For each calendar user principal on the server, the server will
generate two group principals - "proxy groups". One is used to hold
the list of principals who have read-only proxy access to the main
principal's calendars, the other holds the list of principals who
have read-write and scheduling proxy access. NB these new group
principals would have no equivalent in Open Directory.
Privileges on each "proxy group" principal will be set so that the
"owner" has the ability to change property values.
The "proxy group" principals will be child resources of the user
principal resource with specific resource types and thus are easy to
discover. As a result the user principal resources will also be
collection resources.
When provisioning the calendar user home collection, the server will:
a. Add an ACE to the calendar home collection giving the read-only
"proxy group" inheritable read access.
b. Add an ACE to the calendar home collection giving the read-write
"proxy group" inheritable read-write access.
c. Add an ACE to each of the calendar Inbox and Outbox collections
giving the CALDAV:schedule privilege
[I-D.desruisseaux-caldav-sched] to the read-write "proxy group".
3.2. Client
A client can see who the proxies are for the current principal by
examining the principal resource for the two "proxy group" properties
and then looking at the DAV:group-member-set property of each.
The client can edit the list of proxies for the current principal by
editing the DAV:group-member-set property on the relevant "proxy
group" principal resource.
The client can find out who the current principal is a proxy for by
running a DAV:principal-match REPORT on the principal collection.
Daboo [Page 3]
CalDAV Proxy May 2007
Alternatively, the client can find out who the current principal is a
proxy for by examining the DAV:group-membership property on the
current principal resource looking for membership in other users'
"proxy groups".
4. Open Issues
1. Do we want to separate read-write access to calendars vs the
ability to schedule as a proxy?
2. We may want to restrict changing properties on the proxy group
collections to just the DAV:group-member-set property?
3. There is no way for a proxy to be able to manage the list of
proxies. We could allow the main calendar user DAV:write-acl on
their "proxy group" principals, in which case they could grant
others the right to modify the group membership.
4. Should the "proxy group" principals also be collections given
that the regular principal resources will be?
5. New features in CalDAV
5.1. Proxy Principal Resource
Each "regular" principal resource that needs to allow calendar user
proxy support MUST be a collection resource. i.e. in addition to
including the DAV:principal XML element in the DAV:resourcetype
property on the resource, it MUST also include the DAV:collection XML
element.
Each "regular" principal resource MUST contain two child resources
with names "calendar-proxy-read" and "calendar-proxy-write" (note
that these are only suggested names - the server could choose any
unique name for these). These resources are themselves principal
resources that are groups contain the list of principals for calendar
users who can act as a read-only or read-write proxy respectively.
The server MUST include the CS:calendar-proxy-read or CS:calendar-
proxy-write XML elements in the DAV:resourcetype property of the
child resources, respectively. This allows clients to discover the
"proxy group" principals by using a PROPFIND, Depth:1 request on the
current user's principal resource and requesting the DAV:resourcetype
property be returned. The element type declarations are:
Daboo [Page 4]
CalDAV Proxy May 2007
<!ELEMENT calendar-proxy-read EMPTY>
<!ELEMENT calendar-proxy-write EMPTY>
The server MUST allow the "parent" principal to change the DAV:group-
member-set property on each of the "child" "proxy group" principal
resources. When a principal is listed as a member of the "child"
resource, the server MUST include the "child" resource URI in the
DAV:group-membership property on the included principal resource.
Note that this is just "normal" behavior for a group principal.
An example principal resource layout might be:
+ /
+ principals/
+ users/
+ cyrus/
calendar-proxy-read
calendar-proxy-write
+ red/
calendar-proxy-read
calendar-proxy-write
+ wilfredo/
calendar-proxy-read
calendar-proxy-write
If the principal "cyrus" wishes to have the principal "red" act as a
calendar user proxy on his behalf and have the ability to change
items on his calendar or schedule meetings on his behalf, then he
would add the principal resource URI for "red" to the DAV:group-
member-set property of the principal resource /principals/users/
cyrus/calendar-proxy-write, giving:
<DAV:group-member-set>
<DAV:href>/principals/users/red/</DAV:href>
</DAV:group-member-set>
The DAV:group-membership property on the resource /principals/users/
red/ would be:
<DAV:group-membership>
<DAV:href>/principals/users/cyrus/calendar-proxy-write</DAV:href>
</DAV:group-membership>
If the principal "red" was also a read-only proxy for the principal
"wilfredo", then the DA:group-membership property on the resource
/principals/users/red/ would be:
Daboo [Page 5]
CalDAV Proxy May 2007
<DAV:group-membership>
<DAV:href>/principals/users/cyrus/calendar-proxy-write</DAV:href>
<DAV:href>/principals/users/wilfredo/calendar-proxy-read</DAV:href>
</DAV:group-membership>
Thus a client can discover to which principals a particular principal
is acting as a calendar user proxy for by examining the DAV:group-
membership property.
An alternative to discovering which principals a user can proxy as is
to use the WebDAV ACL principal-match report, targeted at the
principal collections available on the server.
Example:
>> Request <<
REPORT /principals/ HTTP/1.1
Host: cal.example.com
Depth: 0
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
Authorization: Digest username="red",
realm="cal.example.com", nonce="...",
uri="/principals/", response="...", opaque="..."
<?xml version="1.0" encoding="utf-8" ?>
<D:principal-match xmlns:D="DAV:">
<D:self/>
<D:prop>
<D:resourcetype/>
</D:prop>
</D:principal-match>
Daboo [Page 6]
CalDAV Proxy May 2007
>> Response <<
HTTP/1.1 207 Multi-Status
Date: Fri, 10 Nov 2006 09:32:12 GMT
Content-Type: application/xml; charset="utf-8"
Content-Length: xxxx
<?xml version="1.0" encoding="utf-8" ?>
<D:multistatus xmlns:D="DAV:"
xmlns:A="http://calendarserver.org/ns/">
<D:response>
<D:href>/principals/users/red/</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:principal/>
<D:collection/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/principals/users/cyrus/calendar-proxy-write</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:principal/>
<A:calendar-proxy-write/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
<D:response>
<D:href>/principals/users/wilfredo/calendar-proxy-read</D:href>
<D:propstat>
<D:prop>
<D:resourcetype>
<D:principal/>
<A:calendar-proxy-read/>
</D:resourcetype>
</D:prop>
<D:status>HTTP/1.1 200 OK</D:status>
</D:propstat>
</D:response>
</D:multistatus>
Daboo [Page 7]
CalDAV Proxy May 2007
5.2. Privilege Provisioning
In order for a calendar user proxy to be able to access the calendars
of the user they are proxying for the server MUST ensure that the
privileges on the relevant calendars are setup accordingly:
The DAV:read privilege MUST be granted for read-only and read-
write calendar user proxy principals
The DAV:write privilege MUST be granted for read-write calendar
user proxy principals.
Additionally, the CalDAV scheduling Inbox and Outbox calendar
collections for the user allowing proxy access, MUST have the CALDAV:
schedule privilege [I-D.desruisseaux-caldav-sched] granted for read-
write calendar user proxy principals.
Note that with a suitable repository layout, a server may be able to
grant the appropriate privileges on a parent collection and ensure
that all the contained collections and resources inherit that. For
example, given the following repository layout:
+ /
+ calendars/
+ users/
+ cyrus/
inbox
outbox
home
work
+ red/
inbox
outbox
work
soccer
+ wilfredo/
inbox
outbox
home
work
flying
In order for the principal "red" to act as a read-write proxy for the
principal "cyrus", the following WebDAV ACE will need to be granted
on the resource /calendars/users/cyrus/ and all children of that
resource:
Daboo [Page 8]
CalDAV Proxy May 2007
<DAV:ace>
<DAV:principal>
<DAV:href>/principals/users/cyrus/calendar-proxy-write</DAV:href>
</DAV:principal>
<DAV:privileges>
<DAV:grant><DAV:read/><DAV:write/></DAV:grant>
</DAV:privileges>
</DAV:ace>
6. Security Considerations
TBD
7. IANA Considerations
This document does not require any actions on the part of IANA.
8. Normative References
[I-D.desruisseaux-caldav-sched]
Desruisseaux, B., "Scheduling Extensions to CalDAV",
draft-desruisseaux-caldav-sched-03 (work in progress),
January 2007.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D.
Jensen, "HTTP Extensions for Distributed Authoring --
WEBDAV", RFC 2518, February 1999.
[RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
Distributed Authoring and Versioning (WebDAV) Access
Control Protocol", RFC 3744, May 2004.
[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
"Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
March 2007.
Appendix A. Acknowledgments
This specification is the result of discussions between the Apple
calendar server and client teams.
Daboo [Page 9]
CalDAV Proxy May 2007
Appendix B. Change History
Changes from -00:
1. Updated to RFC 4791 reference.
Changes from -00:
1. Added more details on actual CalDAV protocol changes.
2. Changed namespace from http://apple.com/ns/calendarserver/ to
http://calendarserver.org/ns/.
3. Made "proxy group" principals child resources of their "owner"
principals.
4. The "proxy group" principals now have their own resourcetype.
Author's Address
Cyrus Daboo
Apple Computer, Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
Email: cyrus@daboo.name
URI: http://www.apple.com/
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Network Working Group W. Sanchez
Request for Comments: 5397 C. Daboo
Category: Standards Track Apple Inc.
December 2008
WebDAV Current Principal Extension
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (c) 2008 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
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document.
Abstract
This specification defines a new WebDAV property that allows clients
to quickly determine the principal corresponding to the current
authenticated user.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions Used in This Document . . . . . . . . . . . . . . . 2
3. DAV:current-user-principal . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Normative References . . . . . . . . . . . . . . . . . . . . . 4
Sanchez & Daboo Standards Track [Page 1]
RFC 5397 WebDAV Current Principal December 2008
1. Introduction
WebDAV [RFC4918] is an extension to HTTP [RFC2616] to support
improved document authoring capabilities. The WebDAV Access Control
Protocol ("WebDAV ACL") [RFC3744] extension adds access control
capabilities to WebDAV. It introduces the concept of a "principal"
resource, which is used to represent information about authenticated
entities on the system.
Some clients have a need to determine which [RFC3744] principal a
server is associating with the currently authenticated HTTP user.
While [RFC3744] defines a DAV:current-user-privilege-set property for
retrieving the privileges granted to that principal, there is no
recommended way to identify the principal in question, which is
necessary to perform other useful operations. For example, a client
may wish to determine which groups the current user is a member of,
or modify a property of the principal resource associated with the
current user.
The DAV:principal-match REPORT provides some useful functionality,
but there are common situations where the results from that query can
be ambiguous. For example, not only is an individual user principal
returned, but also every group principal that the user is a member
of, and there is no clear way to distinguish which is which.
This specification proposes an extension to WebDAV ACL that adds a
DAV:current-user-principal property to resources under access control
on the server. This property provides a URL to a principal resource
corresponding to the currently authenticated user. This allows a
client to "bootstrap" itself by performing additional queries on the
principal resource to obtain additional information from that
resource, which is the purpose of this extension. Note that while it
is possible for multiple URLs to refer to the same principal
resource, or for multiple principal resources to correspond to a
single principal, this specification only allows for a single http(s)
URL in the DAV:current-user-principal property. If a client wishes
to obtain alternate URLs for the principal, it can query the
principal resource for this information; it is not the purpose of
this extension to provide a complete list of such URLs, but simply to
provide a means to locate a resource which contains that (and other)
information.
2. Conventions Used in This Document
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].
Sanchez & Daboo Standards Track [Page 2]
RFC 5397 WebDAV Current Principal December 2008
When XML element types in the namespace "DAV:" are referenced in this
document outside of the context of an XML fragment, the string "DAV:"
will be prefixed to the element type names.
Processing of XML by clients and servers MUST follow the rules
defined in Section 17 of WebDAV [RFC4918].
Some of the declarations refer to XML elements defined by WebDAV
[RFC4918].
3. DAV:current-user-principal
Name: current-user-principal
Namespace: DAV:
Purpose: Indicates a URL for the currently authenticated user's
principal resource on the server.
Value: A single DAV:href or DAV:unauthenticated element.
Protected: This property is computed on a per-request basis, and
therefore is protected.
Description: The DAV:current-user-principal property contains either
a DAV:href or DAV:unauthenticated XML element. The DAV:href
element contains a URL to a principal resource corresponding to
the currently authenticated user. That URL MUST be one of the
URLs in the DAV:principal-URL or DAV:alternate-URI-set properties
defined on the principal resource and MUST be an http(s) scheme
URL. When authentication has not been done or has failed, this
property MUST contain the DAV:unauthenticated pseudo-principal.
In some cases, there may be multiple principal resources
corresponding to the same authenticated principal. In that case,
the server is free to choose any one of the principal resource
URIs for the value of the DAV:current-user-principal property.
However, servers SHOULD be consistent and use the same principal
resource URI for each authenticated principal.
COPY/MOVE behavior: This property is computed on a per-request
basis, and is thus never copied or moved.
Definition:
<!ELEMENT current-user-principal (unauthenticated | href)>
<!-- href value: a URL to a principal resource -->
Sanchez & Daboo Standards Track [Page 3]
RFC 5397 WebDAV Current Principal December 2008
Example:
<D:current-user-principal xmlns:D="DAV:">
<D:href>/principals/users/cdaboo</D:href>
</D:current-user-principal>
4. Security Considerations
This specification does not introduce any additional security issues
beyond those defined for HTTP [RFC2616], WebDAV [RFC4918], and WebDAV
ACL [RFC3744].
5. Acknowledgments
This specification is based on discussions that took place within the
Calendaring and Scheduling Consortium's CalDAV Technical Committee.
The authors thank the participants of that group for their input.
The authors thank Julian Reschke for his valuable input via the
WebDAV working group mailing list.
6. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
Distributed Authoring and Versioning (WebDAV)
Access Control Protocol", RFC 3744, May 2004.
[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
Authors' Addresses
Wilfredo Sanchez
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
EMail: wsanchez@wsanchez.net
URI: http://www.apple.com/
Sanchez & Daboo Standards Track [Page 4]
RFC 5397 WebDAV Current Principal December 2008
Cyrus Daboo
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
EMail: cyrus@daboo.name
URI: http://www.apple.com/
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Internet Engineering Task Force (IETF) M. Nottingham
Request for Comments: 5785 E. Hammer-Lahav
Updates: 2616, 2818 April 2010
Category: Standards Track
ISSN: 2070-1721
Defining Well-Known Uniform Resource Identifiers (URIs)
Abstract
This memo defines a path prefix for "well-known locations",
"/.well-known/", in selected Uniform Resource Identifier (URI)
schemes.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5785.
Copyright Notice
Copyright (c) 2010 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
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.
Nottingham & Hammer-Lahav Standards Track [Page 1]
RFC 5785 Defining Well-Known URIs April 2010
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Appropriate Use of Well-Known URIs . . . . . . . . . . . . 3
2. Notational Conventions . . . . . . . . . . . . . . . . . . . . 3
3. Well-Known URIs . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
5.1. The Well-Known URI Registry . . . . . . . . . . . . . . . . 4
5.1.1. Registration Template . . . . . . . . . . . . . . . . . 5
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
6.1. Normative References . . . . . . . . . . . . . . . . . . . 5
6.2. Informative References . . . . . . . . . . . . . . . . . . 5
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . . 7
Appendix B. Frequently Asked Questions . . . . . . . . . . . . . . 7
1. Introduction
It is increasingly common for Web-based protocols to require the
discovery of policy or other information about a host ("site-wide
metadata") before making a request. For example, the Robots
Exclusion Protocol <http://www.robotstxt.org/> specifies a way for
automated processes to obtain permission to access resources;
likewise, the Platform for Privacy Preferences [W3C.REC-P3P-20020416]
tells user-agents how to discover privacy policy beforehand.
While there are several ways to access per-resource metadata (e.g.,
HTTP headers, WebDAV's PROPFIND [RFC4918]), the perceived overhead
(either in terms of client-perceived latency and/or deployment
difficulties) associated with them often precludes their use in these
scenarios.
When this happens, it is common to designate a "well-known location"
for such data, so that it can be easily located. However, this
approach has the drawback of risking collisions, both with other such
designated "well-known locations" and with pre-existing resources.
To address this, this memo defines a path prefix in HTTP(S) URIs for
these "well-known locations", "/.well-known/". Future specifications
that need to define a resource for such site-wide metadata can
register their use to avoid collisions and minimise impingement upon
sites' URI space.
Nottingham & Hammer-Lahav Standards Track [Page 2]
RFC 5785 Defining Well-Known URIs April 2010
1.1. Appropriate Use of Well-Known URIs
There are a number of possible ways that applications could use Well-
known URIs. However, in keeping with the Architecture of the World-
Wide Web [W3C.REC-webarch-20041215], well-known URIs are not intended
for general information retrieval or establishment of large URI
namespaces on the Web. Rather, they are designed to facilitate
discovery of information on a site when it isn't practical to use
other mechanisms; for example, when discovering policy that needs to
be evaluated before a resource is accessed, or when using multiple
round-trips is judged detrimental to performance.
As such, the well-known URI space was created with the expectation
that it will be used to make site-wide policy information and other
metadata available directly (if sufficiently concise), or provide
references to other URIs that provide such metadata.
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 RFC 2119 [RFC2119].
3. Well-Known URIs
A well-known URI is a URI [RFC3986] whose path component begins with
the characters "/.well-known/", and whose scheme is "HTTP", "HTTPS",
or another scheme that has explicitly been specified to use well-
known URIs.
Applications that wish to mint new well-known URIs MUST register
them, following the procedures in Section 5.1.
For example, if an application registers the name 'example', the
corresponding well-known URI on 'http://www.example.com/' would be
'http://www.example.com/.well-known/example'.
Registered names MUST conform to the segment-nz production in
[RFC3986].
Note that this specification defines neither how to determine the
authority to use for a particular context, nor the scope of the
metadata discovered by dereferencing the well-known URI; both should
be defined by the application itself.
Typically, a registration will reference a specification that defines
the format and associated media type to be obtained by dereferencing
the well-known URI.
Nottingham & Hammer-Lahav Standards Track [Page 3]
RFC 5785 Defining Well-Known URIs April 2010
It MAY also contain additional information, such as the syntax of
additional path components, query strings and/or fragment identifiers
to be appended to the well-known URI, or protocol-specific details
(e.g., HTTP [RFC2616] method handling).
Note that this specification does not define a format or media-type
for the resource located at "/.well-known/" and clients should not
expect a resource to exist at that location.
4. Security Considerations
This memo does not specify the scope of applicability of metadata or
policy obtained from a well-known URI, and does not specify how to
discover a well-known URI for a particular application. Individual
applications using this mechanism must define both aspects.
Applications minting new well-known URIs, as well as administrators
deploying them, will need to consider several security-related
issues, including (but not limited to) exposure of sensitive data,
denial-of-service attacks (in addition to normal load issues), server
and client authentication, vulnerability to DNS rebinding attacks,
and attacks where limited access to a server grants the ability to
affect how well-known URIs are served.
5. IANA Considerations
5.1. The Well-Known URI Registry
This document establishes the well-known URI registry.
Well-known URIs are registered on the advice of one or more
Designated Experts (appointed by the IESG or their delegate), with a
Specification Required (using terminology from [RFC5226]). However,
to allow for the allocation of values prior to publication, the
Designated Expert(s) may approve registration once they are satisfied
that such a specification will be published.
Registration requests should be sent to the
wellknown-uri-review@ietf.org mailing list for review and comment,
with an appropriate subject (e.g., "Request for well-known URI:
example").
Before a period of 14 days has passed, the Designated Expert(s) will
either approve or deny the registration request, communicating this
decision both to the review list and to IANA. Denials should include
an explanation and, if applicable, suggestions as to how to make the
Nottingham & Hammer-Lahav Standards Track [Page 4]
RFC 5785 Defining Well-Known URIs April 2010
request successful. Registration requests that are undetermined for
a period longer than 21 days can be brought to the IESG's attention
(using the iesg@iesg.org mailing list) for resolution.
5.1.1. Registration Template
URI suffix: The name requested for the well-known URI, relative to
"/.well-known/"; e.g., "example".
Change controller: For Standards-Track RFCs, state "IETF". For
others, give the name of the responsible party. Other details
(e.g., postal address, e-mail address, home page URI) may also be
included.
Specification document(s): Reference to the document that specifies
the field, preferably including a URI that can be used to retrieve
a copy of the document. An indication of the relevant sections
may also be included, but is not required.
Related information: Optionally, citations to additional documents
containing further relevant information.
6. References
6.1. 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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008.
6.2. Informative References
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter,
L., Leach, P., and T. Berners-Lee, "Hypertext Transfer
Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
Nottingham & Hammer-Lahav Standards Track [Page 5]
RFC 5785 Defining Well-Known URIs April 2010
[W3C.REC-P3P-20020416]
Marchiori, M., "The Platform for Privacy Preferences 1.0
(P3P1.0) Specification", World Wide Web Consortium
Recommendation REC-P3P-20020416, April 2002,
<http://www.w3.org/TR/2002/ REC-P3P-20020416>.
[W3C.REC-webarch-20041215]
Jacobs, I. and N. Walsh, "Architecture of the World Wide
Web, Volume One", World Wide Web Consortium
Recommendation REC- webarch-20041215, December 2004,
<http:// www.w3.org/TR/2004/REC-webarch-20041215>.
Nottingham & Hammer-Lahav Standards Track [Page 6]
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Appendix A. Acknowledgements
We would like to acknowledge the contributions of everyone who
provided feedback and use cases for this document; in particular,
Phil Archer, Dirk Balfanz, Adam Barth, Tim Bray, Brian Eaton, Brad
Fitzpatrick, Joe Gregorio, Paul Hoffman, Barry Leiba, Ashok Malhotra,
Breno de Medeiros, John Panzer, and Drummond Reed. However, they are
not responsible for errors and omissions.
Appendix B. Frequently Asked Questions
1. Aren't well-known locations bad for the Web?
They are, but for various reasons -- both technical and social --
they are commonly used and their use is increasing. This memo
defines a "sandbox" for them, to reduce the risks of collision and
to minimise the impact upon pre-existing URIs on sites.
2. Why /.well-known?
It's short, descriptive, and according to search indices, not
widely used.
3. What impact does this have on existing mechanisms, such as P3P and
robots.txt?
None, until they choose to use this mechanism.
4. Why aren't per-directory well-known locations defined?
Allowing every URI path segment to have a well-known location
(e.g., "/images/.well-known/") would increase the risks of
colliding with a pre-existing URI on a site, and generally these
solutions are found not to scale well, because they're too
"chatty".
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Authors' Addresses
Mark Nottingham
EMail: mnot@mnot.net
URI: http://www.mnot.net/
Eran Hammer-Lahav
EMail: eran@hueniverse.com
URI: http://hueniverse.com/
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Internet Engineering Task Force (IETF) C. Daboo
Request for Comments: 6764 Apple Inc.
Updates: 4791, 6352 February 2013
Category: Standards Track
ISSN: 2070-1721
Locating Services for Calendaring Extensions to
WebDAV (CalDAV) and vCard Extensions to WebDAV (CardDAV)
Abstract
This specification describes how DNS SRV records, DNS TXT records,
and well-known URIs can be used together or separately to locate
CalDAV (Calendaring Extensions to Web Distributed Authoring and
Versioning (WebDAV)) or CardDAV (vCard Extensions to WebDAV)
services.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc6764.
Copyright Notice
Copyright (c) 2013 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
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.
Daboo Standards Track [Page 1]
RFC 6764 SRV for CalDAV & CardDAV February 2013
Table of Contents
1. Introduction ....................................................2
2. Conventions Used in This Document ...............................3
3. CalDAV SRV Service Labels .......................................3
4. CalDAV and CardDAV Service TXT Records ..........................4
5. CalDAV and CardDAV Service Well-Known URI .......................4
5.1. Example: Well-Known URI Redirects to Actual
"Context Path" .............................................5
6. Client "Bootstrapping" Procedures ...............................5
7. Guidance for Service Providers ..................................8
8. Security Considerations .........................................9
9. IANA Considerations .............................................9
9.1. Well-Known URI Registrations ...............................9
9.1.1. caldav Well-Known URI Registration .................10
9.1.2. carddav Well-Known URI Registration ................10
9.2. Service Name Registrations ................................10
9.2.1. caldav Service Name Registration ...................10
9.2.2. caldavs Service Name Registration ..................11
9.2.3. carddav Service Name Registration ..................11
9.2.4. carddavs Service Name Registration .................12
10. Acknowledgments ...............................................12
11. References ....................................................12
11.1. Normative References .....................................12
11.2. Informative References ...................................14
1. Introduction
[RFC4791] defines the CalDAV calendar access protocol, based on HTTP
[RFC2616], for accessing calendar data stored on a server. CalDAV
clients need to be able to discover appropriate CalDAV servers within
their local area network and at other domains, e.g., to minimize the
need for end users to know specific details such as the fully
qualified domain name (FQDN) and port number for their servers.
[RFC6352] defines the CardDAV address book access protocol based on
HTTP [RFC2616], for accessing contact data stored on a server. As
with CalDAV, clients also need to be able to discover CardDAV
servers.
[RFC2782] defines a DNS-based service discovery protocol that has
been widely adopted as a means of locating particular services within
a local area network and beyond, using DNS SRV Resource Records
(RRs). This has been enhanced to provide additional service meta-
data by use of DNS TXT RRs as per [RFC6763].
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RFC 6764 SRV for CalDAV & CardDAV February 2013
This specification defines new SRV service types for the CalDAV
protocol and gives an example of how clients can use this together
with other protocol features to enable simple client configuration.
SRV service types for CardDAV are already defined in Section 11 of
[RFC6352].
Another issue with CalDAV or CardDAV service discovery is that the
service might not be located at the "root" URI of the HTTP server
hosting it. Thus, a client needs to be able to determine the
complete path component of the Request-URI to use in HTTP requests:
the "context path". For example, if CalDAV is implemented as a
"servlet" in a web server "container", the servlet "context path"
might be "/caldav/". So the URI for the CalDAV service would be,
e.g., "http://caldav.example.com/caldav/" rather than
"http://caldav.example.com/". SRV RRs by themselves only provide an
FQDN and port number for the service, not a path. Since the client
"bootstrapping" process requires initial access to the "context path"
of the service, there needs to be a simple way for clients to also
discover what that path is.
This specification makes use of the "well-known URI" feature
[RFC5785] of HTTP servers to provide a well-known URI for CalDAV or
CardDAV services that clients can use. The well-known URI will point
to a resource on the server that is simply a "stub" resource that
provides a redirect to the actual "context path" resource
representing the service endpoint.
2. Conventions Used in This Document
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].
3. CalDAV SRV Service Labels
This specification adds two SRV service labels for use with CalDAV:
_caldav: Identifies a CalDAV server that uses HTTP without
Transport Layer Security (TLS) [RFC2818].
_caldavs: Identifies a CalDAV server that uses HTTP with TLS
[RFC2818].
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Clients MUST honor Priority and Weight values in the SRV RRs, as
described by [RFC2782].
Example: service record for server without TLS
_caldav._tcp SRV 0 1 80 calendar.example.com.
Example: service record for server with TLS
_caldavs._tcp SRV 0 1 443 calendar.example.com.
4. CalDAV and CardDAV Service TXT Records
When SRV RRs are used to advertise CalDAV and CardDAV services, it is
also convenient to be able to specify a "context path" in the DNS to
be retrieved at the same time. To enable that, this specification
uses a TXT RR that follows the syntax defined in Section 6 of
[RFC6763] and defines a "path" key for use in that record. The value
of the key MUST be the actual "context path" to the corresponding
service on the server.
A site might provide TXT records in addition to SRV records for each
service. When present, clients MUST use the "path" value as the
"context path" for the service in HTTP requests. When not present,
clients use the ".well-known" URI approach described next.
Example: text record for service with TLS
_caldavs._tcp TXT path=/caldav
5. CalDAV and CardDAV Service Well-Known URI
Two ".well-known" URIs are registered by this specification for
CalDAV and CardDAV services, "caldav" and "carddav" respectively (see
Section 9). These URIs point to a resource that the client can use
as the initial "context path" for the service they are trying to
connect to. The server MUST redirect HTTP requests for that resource
to the actual "context path" using one of the available mechanisms
provided by HTTP (e.g., using a 301, 303, or 307 response). Clients
MUST handle HTTP redirects on the ".well-known" URI. Servers MUST
NOT locate the actual CalDAV or CardDAV service endpoint at the
".well-known" URI as per Section 1.1 of [RFC5785].
Servers SHOULD set an appropriate Cache-Control header value (as per
Section 14.9 of [RFC2616]) in the redirect response to ensure caching
occurs or does not occur as needed or as required by the type of
response generated. For example, if it is anticipated that the
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RFC 6764 SRV for CalDAV & CardDAV February 2013
location of the redirect might change over time, then a "no-cache"
value would be used.
To facilitate "context paths" that might differ from user to user,
the server MAY require authentication when a client tries to access
the ".well-known" URI (i.e., the server would return a 401 status
response to the unauthenticated request from the client, then return
the redirect response only after a successful authentication by the
client).
5.1. Example: Well-Known URI Redirects to Actual "Context Path"
A CalDAV server has a "context path" that is "/servlet/caldav". The
client will use "/.well-known/caldav" as the path for its
"bootstrapping" process after it has first found the FQDN and port
number via an SRV lookup or via manual entry of information by the
user, from which the client can parse suitable information. When the
client makes an HTTP request against "/.well-known/caldav", the
server would issue an HTTP redirect response with a Location response
header using the path "/servlet/caldav". The client would then
"follow" this redirect to the new resource and continue making HTTP
requests there to complete its "bootstrapping" process.
6. Client "Bootstrapping" Procedures
This section describes a procedure that CalDAV or CardDAV clients
SHOULD use to do their initial configuration based on minimal user
input. The goal is to determine an http: or https: URI that
describes the full path to the user's principal-URL [RFC3744].
1. Processing user input:
* For a CalDAV server:
+ Minimal input from a user would consist of a calendar user
address and a password. A calendar user address is defined
by iCalendar [RFC5545] to be a URI [RFC3986]. Provided a
user identifier and a domain name can be extracted from the
URI, this simple "bootstrapping" configuration can be done.
+ If the calendar user address is a "mailto:" [RFC6068] URI,
the "mailbox" portion of the URI is examined, and the
"local-part" and "domain" portions are extracted.
+ If the calendar user address is an "http:" [RFC2616] or
"https:" [RFC2818] URI, the "userinfo" and "host" portion
of the URI [RFC3986] is extracted.
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RFC 6764 SRV for CalDAV & CardDAV February 2013
* For a CardDAV server:
+ Minimal input from a user would consist of their email
address [RFC5322] for the domain where the CardDAV service
is hosted, and a password. The "mailbox" portion of the
email address is examined, and the "local-part" and
"domain" portions are extracted.
2. Determination of service FQDN and port number:
* An SRV lookup for _caldavs._tcp (for CalDAV) or _carddavs._tcp
(for CardDAV) is done with the extracted "domain" as the
service domain.
* If no result is found, the client can try _caldav._tcp (for
CalDAV) or _carddav._tcp (for CardDAV) provided non-TLS
connections are appropriate.
* If an SRV record is returned, the client extracts the target
FQDN and port number. If multiple SRV records are returned,
the client MUST use the Priority and Weight fields in the
record to determine which one to pick (as per [RFC2782]).
* If an SRV record is not found, the client will need to prompt
the user to enter the FQDN and port number information
directly or use some other heuristic, for example, using the
extracted "domain" as the FQDN and default HTTPS or HTTP port
numbers. In this situation, clients MUST first attempt an
HTTP connection with TLS.
3. Determination of initial "context path":
* When an SRV lookup is done and a valid SRV record returned,
the client MUST also query for a corresponding TXT record and
check for the presence of a "path" key in its response. If
present, the value of the "path" key is used for the initial
"context path".
* When an initial "context path" has not been determined from a
TXT record, the initial "context path" is taken to be
"/.well-known/caldav" (for CalDAV) or "/.well-known/carddav"
(for CardDAV).
* If the initial "context path" derived from a TXT record
generates HTTP errors when targeted by requests, the client
SHOULD repeat its "bootstrapping" procedure using the
appropriate ".well-known" URI instead.
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RFC 6764 SRV for CalDAV & CardDAV February 2013
4. Determination of user identifier:
* The client will need to make authenticated HTTP requests to
the service. Typically, a "user identifier" is required for
some form of user/password authentication. When a user
identifier is required, clients MUST first use the "mailbox"
portion of the calendar user address provided by the user in
the case of a "mailto:" address and, if that results in an
authentication failure, SHOULD fall back to using the "local-
part" extracted from the "mailto:" address. For an "http:" or
"https:" calendar user address, the "userinfo" portion is used
as the user identifier for authentication. This is in line
with the guidance outlined in Section 7. If these user
identifiers result in authentication failure, the client
SHOULD prompt the user for a valid identifier.
5. Connecting to the service:
* Subsequent to configuration, the client will make HTTP
requests to the service. When using "_caldavs" or "_carddavs"
services, a TLS negotiation is done immediately upon
connection. The client MUST do certificate verification using
the procedure outlined in Section 6 of [RFC6125] in regard to
verification with an SRV RR as the starting point.
* The client does a "PROPFIND" [RFC4918] request with the
request URI set to the initial "context path". The body of
the request SHOULD include the DAV:current-user-principal
[RFC5397] property as one of the properties to return. Note
that clients MUST properly handle HTTP redirect responses for
the request. The server will use the HTTP authentication
procedure outlined in [RFC2617] or use some other appropriate
authentication schemes to authenticate the user.
* If the server returns a 404 ("Not Found") HTTP status response
to the request on the initial "context path", clients MAY try
repeating the request on the "root" URI "/" or prompt the user
for a suitable path.
* If the DAV:current-user-principal property is returned on the
request, the client uses that value for the principal-URL of
the authenticated user. With that, it can execute a
"PROPFIND" request on the principal-URL and discover
additional properties for configuration (e.g., calendar or
address book "home" collections).
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RFC 6764 SRV for CalDAV & CardDAV February 2013
* If the DAV:current-user-principal property is not returned,
then the client will need to request the principal-URL path
from the user in order to continue with configuration.
Once a successful account discovery step has been done, clients
SHOULD cache the service details that were successfully used (user
identity, principal-URL with full scheme/host/port details) and reuse
those when connecting again at a later time.
If a subsequent connection attempt fails, or authentication fails
persistently, clients SHOULD retry the SRV lookup and account
discovery to "refresh" the cached data.
7. Guidance for Service Providers
Service providers wanting to offer CalDAV or CardDAV services that
can be configured by clients using SRV records need to follow certain
procedures to ensure proper operation.
o CalDAV or CardDAV servers SHOULD be configured to allow
authentication with calendar user addresses (just taking the
"mailbox" portion of any "mailto:" URI) or email addresses
respectively, or with "user identifiers" extracted from them. In
the former case, the addresses MUST NOT conflict with other forms
of a permitted user login name. In the latter case, the extracted
"user identifiers" need to be unique across the server and MUST
NOT conflict with any login name on the server.
o Servers MUST force authentication for "PROPFIND" requests that
retrieve the DAV:current-user-principal property to ensure that
the value of the DAV:current-user-principal property returned
corresponds to the principal-URL of the user making the request.
o If the service provider uses TLS, the service provider MUST ensure
a certificate is installed that can be verified by clients using
the procedure outlined in Section 6 of [RFC6125] in regard to
verification with an SRV RR as the starting point. In particular,
certificates SHOULD include SRV-ID and DNS-ID identifiers as
appropriate, as described in Section 8.
o Service providers should install the appropriate SRV records for
the offered services and optionally include TXT records.
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RFC 6764 SRV for CalDAV & CardDAV February 2013
8. Security Considerations
Clients that support TLS as defined by [RFC2818] SHOULD try the
"_caldavs" or "_carddavs" services first before trying the "_caldav"
or "_carddav" services respectively. If a user has explicitly
requested a connection with TLS, the client MUST NOT use any service
information returned for the "_caldav" or "_carddav" services.
Clients MUST follow the certificate-verification process specified in
[RFC6125].
A malicious attacker with access to the DNS server data, or that is
able to get spoofed answers cached in a recursive resolver, can
potentially cause clients to connect to any server chosen by the
attacker. In the absence of a secure DNS option, clients SHOULD
check that the target FQDN returned in the SRV record matches the
original service domain that was queried. If the target FQDN is not
in the queried domain, clients SHOULD verify with the user that the
SRV target FQDN is suitable for use before executing any connections
to the host. Alternatively, if TLS is being used for the service,
clients MUST use the procedure outlined in Section 6 of [RFC6125] to
verify the service. When the target FQDN does not match the original
service domain that was queried, clients MUST check the SRV-ID
identifier in the server's certificate. If the FQDN does match,
clients MUST check any SRV-ID identifiers in the server's certificate
or, if no SRV-ID identifiers are present, MUST check the DNS-ID
identifiers in the server's certificate.
Implementations of TLS [RFC5246], used as the basis for TLS
([RFC2818]), typically support multiple versions of the protocol as
well as the older SSL (Secure Sockets Layer) protocol. Because of
known security vulnerabilities, clients and servers MUST NOT request,
offer, or use SSL 2.0. See Appendix E.2 of [RFC5246] for further
details.
9. IANA Considerations
9.1. Well-Known URI Registrations
This document defines two ".well-known" URIs using the registration
procedure and template from Section 5.1 of [RFC5785].
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RFC 6764 SRV for CalDAV & CardDAV February 2013
9.1.1. caldav Well-Known URI Registration
URI suffix: caldav
Change controller: IETF
Specification document(s): This RFC
Related information: See also [RFC4791].
9.1.2. carddav Well-Known URI Registration
URI suffix: carddav
Change controller: IETF
Specification document(s): This RFC
Related information: See also [RFC6352].
9.2. Service Name Registrations
This document registers four new service names as per [RFC6335]. Two
are defined in this document, and two are defined in [RFC6352],
Section 11.
9.2.1. caldav Service Name Registration
Service Name: caldav
Transport Protocol(s): TCP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: Calendaring Extensions to WebDAV (CalDAV) - non-TLS
Reference: [RFC6764]
Assignment Note: This is an extension of the http service. Defined
TXT keys: path=<context path>
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9.2.2. caldavs Service Name Registration
Service Name: caldavs
Transport Protocol(s): TCP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: Calendaring Extensions to WebDAV (CalDAV) - over TLS
Reference: [RFC6764]
Assignment Note: This is an extension of the https service. Defined
TXT keys: path=<context path>
9.2.3. carddav Service Name Registration
Service Name: carddav
Transport Protocol(s): TCP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: vCard Extensions to WebDAV (CardDAV) - non-TLS
Reference: [RFC6352]
Assignment Note: This is an extension of the http service. Defined
TXT keys: path=<context path>
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9.2.4. carddavs Service Name Registration
Service Name: carddavs
Transport Protocol(s): TCP
Assignee: IESG <iesg@ietf.org>
Contact: IETF Chair <chair@ietf.org>
Description: vCard Extensions to WebDAV (CardDAV) - over TLS
Reference: [RFC6352]
Assignment Note: This is an extension of the https service. Defined
TXT keys: path=<context path>
10. Acknowledgments
This specification was suggested by discussion that took place within
the Calendaring and Scheduling Consortium's CalDAV Technical
Committee. The author thanks the following for their contributions:
Stuart Cheshire, Bernard Desruisseaux, Eran Hammer-Lahav, Helge Hess,
Arnaud Quillaud, Wilfredo Sanchez, and Joe Touch.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.
[RFC2617] Franks, J., Hallam-Baker, P., Hostetler, J., Lawrence, S.,
Leach, P., Luotonen, A., and L. Stewart, "HTTP
Authentication: Basic and Digest Access Authentication",
RFC 2617, June 1999.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
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[RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
Distributed Authoring and Versioning (WebDAV)
Access Control Protocol", RFC 3744, May 2004.
[RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
Resource Identifier (URI): Generic Syntax", STD 66,
RFC 3986, January 2005.
[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
"Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
March 2007.
[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5322] Resnick, P., Ed., "Internet Message Format", RFC 5322,
October 2008.
[RFC5397] Sanchez, W. and C. Daboo, "WebDAV Current Principal
Extension", RFC 5397, December 2008.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785,
April 2010.
[RFC6068] Duerst, M., Masinter, L., and J. Zawinski, "The 'mailto'
URI Scheme", RFC 6068, October 2010.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011.
[RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S.
Cheshire, "Internet Assigned Numbers Authority (IANA)
Procedures for the Management of the Service Name and
Transport Protocol Port Number Registry", BCP 165,
RFC 6335, August 2011.
[RFC6352] Daboo, C., "CardDAV: vCard Extensions to Web Distributed
Authoring and Versioning (WebDAV)", RFC 6352, August 2011.
[RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service
Discovery", RFC 6763, February 2013.
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11.2. Informative References
[RFC5545] Desruisseaux, B., "Internet Calendaring and Scheduling
Core Object Specification (iCalendar)", RFC 5545,
September 2009.
Author's Address
Cyrus Daboo
Apple Inc.
1 Infinite Loop
Cupertino, CA 95014
USA
EMail: cyrus@daboo.name
URI: http://www.apple.com/
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