Calendaring and Scheduling D. Royer
Internet-Draft INET-Consulting
Expires: March 31, 2004 October 1, 2003
How to create dynamic UPNs for invited ATTENDEEs.
draft-royer-calsch-dynamic-upn-02
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Copyright Notice
Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract
This is an extension to the [iCAL] protocol and can be used within
[iTIP] objects. A CU may wish to invite a UPN to an event where the
UPN does not have a account on the CU's CS. This memo describes two
methods to dynamically create UPNs in order for those UPNs to gain
access to the "Organizers" CS.
This memo also includes a description of how to include an [OTP]
challenge in an object directed to a CU. The CUA must compute the
password in order to respond to the object. This challenge and its
response can be sent in the clear as the values are computed using a
secret that would not be known to anyone snooping the line.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. INVITATION Component . . . . . . . . . . . . . . . . . . . . . 4
3. Using the UPN . . . . . . . . . . . . . . . . . . . . . . . . 5
4. OTPKEY Property . . . . . . . . . . . . . . . . . . . . . . . 5
5. INVITE Parameter . . . . . . . . . . . . . . . . . . . . . . . 6
6. EXAMPLES . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1 INVITING URL only . . . . . . . . . . . . . . . . . . . . . . 7
6.2 INVITING CAP . . . . . . . . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9
A. Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . 9
Intellectual Property and Copyright Statements . . . . . . . . 11
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1. Introduction
This memo specifies a variation of the one time password (OTP)
described in [OTP] and a method used to direct an "Attendee" to a web
page to sign up in order to get a UPN and account to a CS.
The OTP method requires that the initial "INVITATION" component be
sent over a secure transmission method. It can be an SSL/TLS
connection such as [CAP] or encrypted [S/MIME] email or other method.
The "Attendee" is sent a key that is an md5, md4, or sha1 hash as
defined in [OTP]. This resulting key is the user's secret key that
gives them access to the CS that is named in the "TARGET" property in
the "INVITATION" component.
The "Attendee"s UPN is then the value of the "ATTENDEE" property for
that attendee as supplied in the "INVITATION" component. The UPN can
be a mailto URL, CAP URL, or any UPN string recognized by the CS. And
their password is computed as described in [OTP].
In this memo the term 'CS' means calendar store and may or might not
mean a [CAP] only CS.
The CS can then send them [iCAL] objects that contain an OTP
challenge. The password the "Attendee" uses is computed using the
user's secret key, the challenge, and the methods described in [OTP].
To gain access to the CS the attendee provides the UPN and computed
password to the CS.
The CS can refresh the key as often as desired with the only
restriction is that the "INVITATION" component be sent encrypted to
the "Attendee".
The CS may if it wishes delete or modify the access rights of dynamic
UPNs when the "Attendee" has no more invitations to reply to, when
there are not any current or future objects for which the "Attendee"
is attending, remove them according to site policy, or it may keep
those UPNs indefinitely.
The web page method includes a URL for the "Attendee" to visit in
order to get a UPN account on the system. The "INVITATION" "text/
calendar" component MUST BE sent as part of a [MIME] multipart/
alternate object that contains at least a text/plain and text/
calendar MIME objects where text or optional HTML describe how to
connect and get an account for those CUAs that do not conform to this
specification.
A CUA requests that a supporting CS send the invitations by including
the new "INVITE" parameter on the "ATTENDEE" property to "Attendees"
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not known to the CUA. If that "ATTENDEE" property value is already
known to the CS it has no effect.
[CAP] Implementation that support this protocol extensions must
supply the "INVITATION" value in the "COMPONENT" property value in
their "GET-CAPABILITY" reply.
2. INVITATION Component
Component Name: INVITATION
Purpose: To invite a new UPN to have access on a CS. The "INVITATION"
component allows an "Organizer" to invite UPNs to use a CS. It can
include an OTP key and a web page to be visited that will initialize
the users CUA.
Formal Definition: A "INVITATION" component is defined by the
following notation:
invitecomp = "BEGIN" ":" "INVITATION" CRLF
inviteprops
"END" ":" "INVITATION" CRLF
; TARGET used only if access to a CS is supplied.
;
inviteprops target ; As defined in [CAP]
; As defined here, [iCAL], and [CAP]
; In addition the "ATTENDEE" and "ORGANIZER" values
; may be multivalued in order to allow for more than
; one kind of CAL-ADDRESS. At least one
; CAL-ADDRESS must be supplied.
;
organizer attendee
; Each may be included once.
;
*otpkey *url
; Optional and may occur more than once.
;
*other-props ; As definded in [CAP].
*x-comp ; As defined in [CAP].
The following is an invitation by the "Organizer" to an "Attendee"
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requesting they sign-up so they can process [iCAL] objects on
"TARGET". It includes both an "URL" and "OTPKEY" properties so the
CUA may use the web, [iTIP], or CAP to initialize the account.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//some prodid
BEGIN:INVITATION
TARGET:CAP:cal.example.com
OTPKEY:md5-cdb5bf5ef5427e1512c29bfd8dff2dc0
URL:https://cal.example.com/otp?key=cdb5bf5ef5427e1512c29bfd8dff2dc0
ORGANIZER:doug@example.com
ATTENDEE:cap:guest@remote.example.com
,mailto:username@site.example.com
END:INVITATION
END:VCALENDAR
3. Using the UPN
There is no reply to a "INVITATION" other than to connect using the
supplied "UPN" property value or use any supplied "OTPKEY" property
value to calculate the password to sign onto the CS, or send an
[iMIP] message signed as defined in [iMIP] using an "ATTENDEE"
property value that matches the original "ATTENDEE" value sent to the
"Attendee".
If a "INVITATION" component contained a "URL" property and the
"Attendee" elected to use the URL to sign up, then the "Attendee"
would after successful registration on the web page have been
provided a UPN and password that would be valid to use.
If a "INVITATION" component contained an "OTPKEY" property and value
and the "Attendee" elected to sign up using CAP, then the "Attendee"
would connect to a CS matching the "TARGET" property value and login
using the "ATTENDEE" property value supplied as the "Attendee"s UPN
and the computed [OTP] password to access the CS. A successful [BEEP]
authentication confirms the account for both the CUA and the CS.
4. OTPKEY Property
Property Name: OTPKEY
Purpose: The "OTPKEY" property is used to supply the "Attendee" with
an original or updated key to be used in computing the [OTP]
response. This value MUST NOT be sent in the clear.
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Value Type: TEXT
Property Parameters: Non-standard property parameters can be
specified on this property.
Formal Definition: The property is defined by the following notation:
otpkey = "OTPKEY" other-params ":" otpvalue
otpvalue ; As defined in [OTP].
Example: The following are examples of this property:
OTPKEY:md4-cf6864ea860e56ba5a3a015f23ebccbd
OTPKEY:md5-45548dc24cb481be7ebb31653d18acc8
OTPKEY:sha1-f8cb62bfa2f962a06588c8129f81547fba434d13
5. INVITE Parameter
Parameter Name: INVITE
Purpose: The "INVITE" boolean parameter is added by a supporting CUA
to the "ATTENDEE" property and sent to a supporting CS to ask the CS
to invite an "Attendee" unknown to the CUA or CS. The "INVITE"
parameter is only sent to a CS from a CUA.
Value Type: BOOLEAN
Conformance: This parameter can be specified in the "ATTENDEE"
properties in a component that has the "METHOD" value set to
"REQUEST" or when the storing an object in the "BOOKED" (as defined
in [CAP]) state. This can only be done to CSs that have set the
"INVITATION" value in their "COMPONENT" property value in their
"GET-CAPABILITY" reply.
Description: A CUA may add the "INVITE" parameter to the "ATTENDEE"
property. If the "INVITE" parameter is set to "TRUE", then the CUA is
informing the CS that the CUA does not know if the UPN has an account
on the CS. If the CS does not have any such UPN as a valid account
the CS must send an "INVITATION" to the UPN.
Formal Definition: The property is defined by the following notation:
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inviteparam = "INVITE" "=" boolean
Example: The following is an example of this parameter:
An example usage is:
ATTENDEE;INVITE=true;guest@remote.example.com
6. EXAMPLES
This section contains various examples
6.1 INVITING URL only
When inviting an "Attendee" using an URL, the URL must be sent over a
secure connection such as S/MIME, 'https', or [CAP]. The following
example is an "INVITATION" component that is inviting the "Attendee"
to have a [CAP] account on 'cal.example.com' and the "Attendee" can
only sign up by URL in this example:
Content-Type: multipart/alternative; boundary=boundary42
--boundary42
Content-Type: text/plain; charset=us-ascii
...plain text version of message goes here....
An organizer of an event: doug@example.com
wishes to invite you to participate in a meeting that
will be ...
If you wish to participate please go to the following
URL and sign up for site access:
https://cal.example.com/otp?key=cdb5bf5ef5427e1512c29bfd8dff2dc0
and follow the instructions in order to be invited.
--boundary42
Content-Type: text/html
.... HTML version of same message goes here ...
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--boundary42
Content-Type: text/calendar
BEGIN:INVITATION
TARGET:CAP:cal.example.com
URL:https://cal.example.com/otp?key=cdb5bf5ef5427e1512c29bfd8dff2dc0
ORGANIZER:cap:doug@example.com,mailto:doug@example.com
ATTENDEE:cap:guest@remote.example.com
END:INVITATION
--boundary42--
Following a successful web registration then "Attendee" will have a
UPN of "guest@remote.example.com" and will use the password as
instructed on the web page.
6.2 INVITING CAP
The following example is an "INVITATION" component that is inviting
the "Attendee" by CAP. No URL is provided so the first connection or
[iTIP] object that uses the correct computed [OTP] password validates
the account.
Content-Type: multipart/alternative; boundary=boundary42
--boundary42
Content-Type: text/plain; charset=us-ascii
...plain text version of message goes here....
An organizer of an event: doug@example.com
wishes to invite you to participate in a meeting that
will be ...
--boundary42
Content-Type: text/html
.... HTML version of same message goes here ...
--boundary42
Content-Type: text/calendar
BEGIN:INVITATION
TARGET:CAP:cal.example.com
ORGANIZER:cap:doug@example.com,mailto:doug@example.com
ATTENDEE:cap:guest@remote.example.com
OTPKEY:md5-cdb5bf5ef5427e1512c29bfd8dff2dc0
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END:INVITATION
--boundary42--
Following a successful first sign on then "Attendee" will have a UPN
of "guest@remote.example.com" and will use the password computed from
the "OTPKEY" value and the SASL challenge.
Author's Address
Doug Royer
INET-Consulting.com
1795 W. Broadway #266
Idaho Falls, Idaho 83402
US
Phone: 208-520-4044
Fax: 866-594-8574
EMail: Doug@Royer.com
URI: http://Royer.com/People/Doug
Appendix A. Bibliography
[BEEP] Rose, M., "The Block Extensible Exchange Protocol Core",
RFC 3080, March 2001
ftp://ftp.isi.edu/in-notes/rfc3080.txt
[BEEPTCP] Rose, M., "Mapping the BEEP Core onto TCP", RFC 3081, March 2001
ftp://ftp.isi.edu/in-notes/rfc3081.txt
[iCAL] Dawson, F. and Stenerson, D., "Internet Calendaring and
Scheduling Core Object Specification (iCalendar)", RFC 2445,
November 1998 ftp://ftp.isi.edu/in-notes/rfc2445.txt
[iTIP] Silverberg, S., Mansour, S., Dawson, F. and Hopson, R.,
"iCalendar Transport-Independent Interoperability Protocol
(iTIP) Events, BusyTime, To-dos and Journal Entries",
RFC 2446, November 1998 ftp://ftp.isi.edu/in-notes/rfc2446.txt
[iMIP] Dawson, F., Mansour, S. and Silverberg, "iCalendar
Message-Based Interoperability Protocol (iMIP)", RFC 2447,
November 1998 ftp://ftp.isi.edu/in-notes/rfc2447.txt
[CAP] Royer, D., Babics, G., Hill, P. Mansour, S. "Calendar
Access Protocol (CAP)", work in progress,
draft-ietf-calsch-cap-12.txt.
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[OTP] Haller, N. and C. Metz, "A One-Time Password System,"
RFC 1938, May 1996.
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