draft-ietf-sipping-content-indirect-02.txt   draft-ietf-sipping-content-indirect-03.txt 
SIPPING S. Olson SIPPING S. Olson
Internet-Draft Microsoft Internet-Draft Microsoft
Expires: March 24, 2003 September 23, 2002 Expires: August 28, 2003 February 27, 2003
Requirements for Content Indirection in Session Initiation Protocol Requirements for Content Indirection in Session Initiation Protocol
(SIP) Messages (SIP) Messages
draft-ietf-sipping-content-indirect-02 draft-ietf-sipping-content-indirect-03
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
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This Internet-Draft will expire on March 24, 2003. This Internet-Draft will expire on August 28, 2003.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved. Copyright (C) The Internet Society (2003). All Rights Reserved.
Abstract Abstract
This specification defines requirements for a mechanism to indirectly This specification defines requirements for a mechanism to indirectly
specify the content of a SIP message for the purpose of transferring specify the content of a SIP message for the purpose of transferring
the content via a non-SIP channel. the content via a non-SIP channel.
1. Terminology 1. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
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stored on her web server with another user she has a IM conversation stored on her web server with another user she has a IM conversation
with. The JPEG is intended to be rendered inline in the IM with. The JPEG is intended to be rendered inline in the IM
conversation. The recepient of the MESSAGE request launches a HTTP conversation. The recepient of the MESSAGE request launches a HTTP
GET request to the web server to retrieve the JPEG image. GET request to the web server to retrieve the JPEG image.
4. Requirements 4. Requirements
It MUST be possible to specify the location of content via a URI It MUST be possible to specify the location of content via a URI
[3]. [3].
It MUST be possible to specify the length of the indirect content.
It MUST be possible to specify the type of the indirect content.
It MUST be possible to specify the disposition of each URI It MUST be possible to specify the disposition of each URI
independently. independently.
It MUST be possible to label each URI to identify if and when the It MUST be possible to label each URI to identify if and when the
content referred to by that URI has changed. Applications of this content referred to by that URI has changed. Applications of this
mechanism may send the same URI more than once. The intention of mechanism may send the same URI more than once. The intention of
this requirement is to allow the receiving party to determine if this requirement is to allow the receiving party to determine if
the content referenced by the URI has changed without having to the content referenced by the URI has changed without having to
actually retrieve that content. Example ways the URI could be actually retrieve that content. Example ways the URI could be
labelled include a sequence number, timestamp, version number, labelled include a sequence number, timestamp, version number,
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be specified in the event that one of the parties is unable to be specified in the event that one of the parties is unable to
support content indirection. support content indirection.
It MUST be possible for the UAC and UAS to negotiate the type of It MUST be possible for the UAC and UAS to negotiate the type of
the indirect content when using the content indirection mechanism. the indirect content when using the content indirection mechanism.
It MUST be possible for the UAC and UAS to negotiate support for It MUST be possible for the UAC and UAS to negotiate support for
URI scheme(s) to be used in the content indirection mechanism. URI scheme(s) to be used in the content indirection mechanism.
This is in addition to the ability to negotiate the content type. This is in addition to the ability to negotiate the content type.
It SHOULD be possible to ensure the integrity of the URI when it It SHOULD be possible to ensure the integrity and privacy of the
is received by the remote party. URI when it is received by the remote party.
It MUST be possible to process the content indirection without It MUST be possible to process the content indirection without
human intervention. human intervention.
It MUST allow for indirect transference of content in any SIP It MUST allow for indirect transference of content in any SIP
message which would otherwise carry that content as a body. message which would otherwise carry that content as a body.
5. Security Considerations 5. Security Considerations
Any content indirection mechanism introduces additional security Any content indirection mechanism introduces additional security
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pointing to an internal resource of the recipient. The response pointing to an internal resource of the recipient. The response
to the content indirection request could reveal information about to the content indirection request could reveal information about
open (and vulnerable) ports on these internal resources. open (and vulnerable) ports on these internal resources.
A content indirection URL can disclose sensitive information about A content indirection URL can disclose sensitive information about
the initiator such as an internal user name (as part of an HTTP the initiator such as an internal user name (as part of an HTTP
URL) or possibly geolocation information. URL) or possibly geolocation information.
Fortunately, all of these potential threats can be mitigated through Fortunately, all of these potential threats can be mitigated through
careful screening of both the indirect content URIs that are received careful screening of both the indirect content URIs that are received
as well as those that are sent. The clear requirement is that as well as those that are sent. Integrity and privacy protection of
integrity and potentially privacy protection SHOULD be applied to the the indirect content URI can prevent additional attacks as well.
content indirection URI(s) in a SIP message.
References References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", RFC 2119, March 1997. Levels", BCP 14, RFC 2119, March 1997.
[2] Rosenberg, J., Schulzrinne, Camarillo, Johnston, Peterson, [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Sparks, Handley and Schooler, "SIP: Session Initiation Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Protocol", RFC 3261, June 2002. Session Initiation Protocol", RFC 3261, June 2002.
[3] Berners-Lee, Fielding and Masinter, "Uniform Resource [3] Berners-Lee, T., Fielding, R. and L. Masinter, "Uniform Resource
Identifiers (URI): Generic Syntax", RFC 2396, August 1996. Identifiers (URI): Generic Syntax", RFC 2396, August 1998.
Author's Address Author's Address
Sean Olson Sean Olson
Microsoft Microsoft
One Microsoft Way One Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
US US
Phone: +1-425-707-2846 Phone: +1-425-707-2846
EMail: seanol@microsoft.com EMail: seanol@microsoft.com
URI: http://www.microsoft.com/rtc URI: http://www.microsoft.com/rtc
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