SIPPING J. Rosenberg
Internet-Draft Cisco Systems
Expires: August 21, 2005 G. Camarillo
Ericsson
D. Willis
Cisco Systems
February 20, 2005
A Framework for Consent-Based Communications in the Session
Initiation Protocol (SIP)
draft-ietf-sipping-consent-framework-01.txt
Status of this Memo
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Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
The Session Initiation Protocol (SIP) supports communications across
many media types, including real-time audio, video, text, instant
messaging, and presence. In its current form, it allows session
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invitations, instant messages, and other requests to be delivered
from one party to another without requiring explicit consent of the
recipient. Without such consent, it is possible for SIP to be used
for malicious purposes, including spam and denial-of-service attacks.
This document identifies a framework for consent-based communications
in SIP.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Relays . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Reference Architecture . . . . . . . . . . . . . . . . . . . . 4
5. Structure of a Permission . . . . . . . . . . . . . . . . . . 5
6. Single-Relay Scenario . . . . . . . . . . . . . . . . . . . . 6
6.1 Attempting Communication . . . . . . . . . . . . . . . . . 6
6.2 Requesting a Permission . . . . . . . . . . . . . . . . . 8
6.3 Waiting for Permissions . . . . . . . . . . . . . . . . . 9
6.4 Granting a Permission . . . . . . . . . . . . . . . . . . 9
6.5 Retrying the Original Request . . . . . . . . . . . . . . 10
6.6 Permission Revocation . . . . . . . . . . . . . . . . . . 10
7. Permission Servers . . . . . . . . . . . . . . . . . . . . . . 11
8. Multiple-Relay Scenario . . . . . . . . . . . . . . . . . . . 12
8.1 Initial Steps . . . . . . . . . . . . . . . . . . . . . . 12
8.2 Waiting for Permissions . . . . . . . . . . . . . . . . . 15
8.3 Intermediate Relays . . . . . . . . . . . . . . . . . . . 15
9. Installing Permissions in Advance . . . . . . . . . . . . . . 16
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . 16
11. Security Considerations . . . . . . . . . . . . . . . . . . 16
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
12.1 Normative References . . . . . . . . . . . . . . . . . . . . 16
12.2 Informative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . 18
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1. Introduction
The Session Initiation Protocol (SIP) [1] supports communications
across many media types, including real-time audio, video, text,
instant messaging and presence. This communication is established by
the transmission of various SIP requests (such as INVITE and MESSAGE
[2]) from an initiator to the recipient, with whom communication is
desired. Although a recipient of such a SIP request can reject the
request, and therefore decline the session, a SIP network will
deliver a SIP request to the recipient without their explicit
consent.
Receipt of these requests without explicit consent can cause a number
of problems in SIP networks. These include spam and DoS (Denial of
Service) attacks. These problems are described in more detail in a
companion requirements document [5].
This specification defines a basic framework for adding consent-based
communication to SIP.
2. Definitions
Recipient URI: The request-URI of an outgoing request sent by an
entity (e.g., a proxy) that has performed a translation operation.
Target URI: The request-URI of an incoming request that arrives to an
entity (e.g., a proxy) that will perform a translation operation.
Translation operation: Operation by which an entity (e.g., a proxy)
translates the request URI of an incoming request (i.e., the
target URI) into one or more URIs (i.e., recipient URIs) which are
used as the request URIs of one or more outgoing requests.
3. Relays
A central concept in this framework is that of a relay. A relay is
defined as any SIP server, be it a proxy, B2BUA (Back-to-Back User
Agent), or some hybrid, which receives a request and translates the
request URI into one or more next hop URIs to which it then delivers
a request. The request URI of the incoming request is referred to as
'target URI' and the destination URI of the outgoing requests is
referred to as 'recipient URIs', as shown in Figure 1.
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+---------------+
| | recipient URI
| |---------------->
target URI | Translation |
-------------->| Operation | recipient URI
| |---------------->
| |
+---------------+
Figure 1: Translation operation
Thus, an essential aspect of a relay is that of translation. When a
relay receives a request, it translates the request URI into one or
more additional URIs. Or, more generally, it can create outgoing
requests to one or more additional URIs. The translation operation
is what creates the consent problem.
Additionally, since the translation operation can result in more than
one URI, it is also the source of amplification. Servers that do not
perform translations, such as outbound proxy servers, do not cause
amplification.
Since the translation operation is based on local policy or local
data (such as registrations), it is the vehicle by which a request is
delivered directly to an endpoint, when it would not otherwise be
possible to. In other words, if a spammer has the address of a user,
'sip:user@example.com', it cannot deliver a MESSAGE request to the UA
(User Agent) of that user without having access to the registration
data that maps 'sip:user@example.com' to the UA on which that user is
present. Thus, it is the usage of this registration data, and more
generally, the translation logic, which must be authorized in order
to prevent undesired communications.
4. Reference Architecture
The reference architecture is shown in Figure 2. In this
architecture, a UAC wishes to send a message to a request URI
representing a resource in domain A (sip:resource@A). This request
may pass through a local outbound proxy (not shown), but eventually
arrives at a server authoritative for domain A. This server, which
acts as a relay, performs a translation operation, translating the
target URI into one or more recipient URIs, which may or may not
belong to domain A. This relay may be, for instance, a proxy server
or a URI-list service [7].
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+-------+
| |
>| UAS |
+-------+ / | |
| Rules | / +-------+
| DB | /
+-------+ /
| /
V /
+-----+ +-------+ / +-------+
| | | |/ | |
| UAC |------>| Relay |-------->| Proxy |
| | | |\ | |
+-----+ +-------+ \ +-------+
\
\ [...]
\
\
\ +-------+
\ | |
>| B2BUA |
| |
+-------+
Figure 2: Relay performing a translation
5. Structure of a Permission
This framework centers on the idea that a relay will only perform a
translation if a permission is in place authorizing that translation.
As such, the notion of a permission is another key part of this
framework. A permission is an object, represented in XML, that
contains several pieces of data:
Identity of the Sender: A URI representing the identity of the sender
for whom permissions are granted.
Identity of the Original Recipient: A URI representing the identity
of the original recipient, which is used as the input for the
translation operation. This is also called the target URI.
Identity of the Final Recipient: A URI representing the result of the
translation. The permission grants ability for the sender to send
requests to the target URI, and for a relay receiving those
requests to forward them to this URI. This is also called the
recipient URI.
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Operations Permitted: A set of specific methods or qualifiers for
which the permission applies. For example, the permission may
only grant relaying for INVITE or MESSAGE, or for MESSAGE with
specific MIME types.
Signature: A digital signature over the rest of the permission,
signed by an entity that can identify itself as the recipient URI.
The signature is not always present.
Permissions are installed on a resource by resource basis. That is,
for each target URI to which a request is sent, there is a set of
permissions installed for that URI. Each permission has the content
described above.
A natural format for representing permissions appears to be the
common policy format [3]. This format is also used for presence
permissions.
6. Single-Relay Scenario
This section describes the fundamental operations of this framework
in a single-relay scenario. The descriptions are illustrated with an
example (see Figure 3).
6.1 Attempting Communication
When a UA sends a request to a target resource (message 1 in Figure
3), the request eventually arrives at a server that is authoritative
for the domain in the request URI. The server may require, as part
of its processing logic, the relaying of the request to one or more
next hops. If such relaying is required, the server first
authenticates the sender of the request. Such authentication can be
done using the SIP identity mechanism [4]. Once the sender is
authenticated, the server checks its permission database for that
target resource. It looks for permissions containing senders whose
URI matches the identity of the sender of the request. Of those that
are found, the server checks to see if the permitted translated URI
matches the URIs to which the server wishes to relay the request.
If at least one of the next hops to which the server wishes to relay
have not been permitted, the server includes a Permission-Needed
header field in the response to the request (message 2 in Figure 3).
This Permission-Needed header field contains a list of URIs, each of
which identify a translation for which permissions are needed.
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Note that each of the URIs identify a translation at the server
(i.e., at the relay). That is, the domain part of the URI will
identify the server and the user part will be meaningful only to
the server.
A Relay B
|(1) REQUEST school-friends@relay |
|-------------------------->| |
|(2) 470 Consent Needed | |
|Call-Info: 123@relay; | |
|purpose=wait-permission | |
|Permission-Needed: xyz@relay |
|<--------------------------| |
|(3) CONSENT school-friends@relay |
|Permission-From: xyz@relay | |
|-------------------------->| |
| |(4) CONSENT B |
| |Permission-Requested: uri-req
| |-------------------------->|
| |(5) 202 Accepted |
| |<--------------------------|
|(6) 202 Accepted | |
|<--------------------------| |
|(7) SUBSCRIBE 123@relay | |
|-------------------------->| |
|(8) 200 OK | |
|<--------------------------| |
|(9) NOTIFY (no permission) | |
|<--------------------------| |
|(10) 200 OK | |
|-------------------------->| |
| |(11) HTTP uri-req |
| |Get Requested Permission |
| |<--------------------------|
| |(12) 200 OK |
| |Permission Document |
| |URI to Upload: uri-up |
| |-------------------------->|
| |(13) PUBLISH uri-up |
| |Permission Document |
| |<--------------------------|
| |(14) 200 OK |
| |-------------------------->|
|(15) NOTIFY (permission) | |
|<--------------------------| |
|(16) 200 OK | |
|-------------------------->| |
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|(17) REQUEST school-friends@relay |
|-------------------------->| |
| |(18) REQUEST B |
| |Permission-Used: uri-perm |
| |-------------------------->|
Figure 3: Basic call flow
The status code the server uses in its response depends on the
service the translation is part of. For example, a URI-list service
which receives a request with a list of recipient URIs may already
have permissions for some of them. The URI-list service may choose
to perform the translations which it has permissions for and return a
200 (OK) response with a list of URIs in a Permission-Needed header
field for the translations for which permissions have not yet been
obtained. Alternatively, the URI-list service may choose not to
perform any translation and to return a 470 (Consent Needed) response
with a list of URIs in a Permission-Needed header field for the
translations for which permissions have not yet been obtained.
The response from the server may carry a URI in a Call-Info header
field (wait-permission purpose) where the client can SUBSCRIBE to
using the wait-permission event package. This event package models
the state of the permission granted to the client for communicating
with the target URIs. When a permission is granted, the state
changes, and the client receives a NOTIFY. This NOTIFY contains the
permission(s) that have been granted for the sender.
OPEN ISSUE: in which response does the server include the
call-info header? Proposal: it can include it in any response
(i.e., responses to the original request and responses to the
CONSENTs, but it should include always the same URI.
Usage of an event package has the benefit that the client can come
back at any time and do a query SUBSCRIBE to see if permissions were
granted, or it can wait for them to be granted, and find out when.
There is no requirement that the client use this event package to
wait. For some requests, it may not be important for the sender to
find out when permission is granted (e.g., a presence subscription).
6.2 Requesting a Permission
If a server returns a response with a Permission-Needed header field,
the client knows that it needs to obtain some number of permissions.
The response will include a list of URIs in a Permission-Needed
header field for which permission must be obtained. To obtain
permission, the client generates as many CONSENT request as entries
the Permission-Needed header field contained.
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Each CONSENT request (message 3 in Figure 3) is sent to the same URI
as the original request and carries, in a Permission-From header
field, one of the URIs received in the Permission-Needed header
field. The server will forward these CONSENT requests on to the
destinations whose permissions have not been obtained yet.
OPEN ISSUE: it was proposed having clients send CONSENTs to the
URIs received in the Permission-Needed header field (i.e., using
them in the Request-URI instead of in a Request-From header
field). This would require the server to store more state
information and come up with a number of URIs in multiple-relay
scenarios.
When the CONSENT request arrives at the server, the relay adds a
Permission-Requested header field which contains a URI (e.g., an HTTP
URI) that the receiver can use to download a description of the
permission being requested (e.g., an XML-based permission document).
Then, the server forwards the request towards its destination
(message 4 in Figure 3).
If there are several relays between the sender and the final
destination, those CONSENT requests may also fail if permissions have
not yet been obtained, in which case the process recurses, as
described in Section Section 8. Eventually, the client will have
sent a request to all of the relays at the leaves of the translation
tree between the sender and the final destinations.
6.3 Waiting for Permissions
A CONSENT request is responded with a 202 (Accepted) response
(message 5 in Figure 3). As stated earlier, if the client is
interested in the status of the permissions, it can SUBSCRIBE
(message 7 in Figure 3) to the the wait-permission event package
using the URI received in the Call-Info header field (wait-permission
purpose) of the response to the original request (responses to
CONSENT requests may also carry a Call-Info header field with such a
URI).
6.4 Granting a Permission
On reception of a CONSENT request, the user fetches the permission
being requested from the URI in the Permission-Requested header field
(message 11 in Figure 3). This permission document includes the URI
that the user needs to use to upload the permissions that the user
chooses to grant. So, if the user wishes to grant a permission, it
may use a SIP PUBLISH request (message 13 in Figure 3) to upload a
permission document into that URI. This PUBLISH request is
authenticated using the SIP identity mechanism.
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OPEN ISSUE: XCAP could be useful for endpoints that support it.
Do we want to allow XCAP to be used? If XCAP was allowed, how do
we permorm authentication? Do endpoings using XCAP need to sign
their permissions? Relaying on the routing architecture and SIPS
to deliver a randomly-looking http URI to the proper endpoint does
not seem to be secure enough.
OPEN ISSUE: Using XCAP to grant permissions would require the
definition of a new application usage. We note that this usage
appears to be a generalization of the presence rules usage
currently defined [6].
The owner of the target resource may choose to grant the permissions
requested or a superset of them. For example, a CONSENT request may
request permission to perform a given translation on MESSAGE
requests, and the target resource owner may grant permission to
perform the translation on any request (not only on MESSAGE
requests).
6.5 Retrying the Original Request
The sender learns about permissions through the wait-permission event
package. Once it has obtained permissions for all of the resources
that were identified in the Permission-Needed header field, the
client can retry the original request (message 17 in Figure 3).
When the server performs the translation, it adds a Permission-Used
header field with a URI (e.g., an HTTP URI) where the permission
document that authorizes the translation can be downloaded from.
6.6 Permission Revocation
At any time, if a client wants to revoke any permission, it uses the
same URI as before to upload a new permission document. If a client
loses this URI for some reason, it needs to wait until it receives a
new request, which will contain a Permission-Used header field.
The permission documents that can be downloaded from the URIs in the
Permission-Used header field contain a URI where the client can
upload a new permission document (e.g., a permission document that
does not allow a particular translation any longer).
OPEN ISSUE: is it OK to force clients to download the permission
document in order to obtain the SIP URI to send their PUBLISH
requests to or we want to already include such a URI in the
Permission-Used header field.
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7. Permission Servers
We described in Section 6.4 how a user agent that receives a CONSENT
request can use a PUBLISH request to grant certain permissions.
Nevertheless, users are not on-line all the time and, so, sometimes
are not able to receive CONSENT requests.
This issue is also found in presence, where a user's status is
reported by a presence server instead of by the user's user agents,
which can go on and off-line. Similarly, we define permission
servers. Permission servers are network elements that act as SIP UAs
and handle CONSENT requests for a user.
Permission servers inform users about new CONSENT requests using the
"grant-permission" event package. The user associated with the
target URI SUBSCRIBEs (message 1 in Figure 4) to the
"grant-permission" event package at the permission server. This
event package models the state of all pending CONSENT requests for a
particular resource, for which permissions do not yet exist. When a
new CONSENT request (message 3 in Figure 4) arrives for which
permissions have not been granted, a NOTIFY (message 5 in Figure 4)
is sent to the user. This informs them that permission is needed for
a particular sender. The NOTIFY contains information on the
operation which was requested.
There is a strong similarity between the watcherinfo event package
and the grant-permission event package. Indeed, the
grant-permission package is effectively a superset of watcherinfo.
Once in place, presentities could use the grant-permission event
package for presence in addition to all other services for which
opt-in is being provided.
When a user is notified of a new pending CONSENT request, the user
follows regular procedures to upload the permissions that were
requested (messages 9 to 11 in Figure 4).
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Relay B's Permission B
Server
| |(1) SUBSCRIBE |
| |grant-permission |
| |<------------------|
| |(2) 200 OK |
| |------------------>|
|(3) CONSENT B | |
|Permission-Requested: uri-req |
|------------------>| |
|(4) 202 Accepted | |
|<------------------| |
| |(5) NOTIFY |
| |Permission Requested: uri-req
| |------------------>|
| |(6) 200 OK |
| |<------------------|
|(7) HTTP uri-req | |
|Get Requested Permission |
|<--------------------------------------|
|(8) 200 OK | |
|Permission Document| |
|URI to Upload: uri-up |
|------------------>| |
|(9) PUBLISH uri-up | |
|Permission Document| |
|<--------------------------------------|
|(10) 200 OK | |
|-------------------------------------->|
Figure 4: Permission server operation
8. Multiple-Relay Scenario
One of the results of a translation (i.e., a recipient URI) at a
relay can route to another relay. In this case, there will be
multiple relays between the UA generating a request and the
destination UA or UAs.
8.1 Initial Steps
The way UAs are informed that they need to request permissions for a
translation and the way they request those permissions (i.e., using
CONSENT requests) are identical to the single-relay case.
In the example of Figure 5, Relay 1 handles the URI 'friends@relay1',
which translates to a set of URIs. Relay 1 already has permissions
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to perform all the translations but one. Relay 1 needs to obtain
permission to perform the translation to 'school-friends@relay2'.
Relay 1 returns a 470 (Consent Needed) response (message 2 in Figure
5) with a Permission-Needed header field. The UA generates a CONSENT
request (message 2 in Figure 5) placing the URI received in that
header field in a Request-From header field.
The CONSENT request is forwarded by Relay 1 to Relay 2 (message 4 in
Figure 5). The URI 'school-friends@relay2' translates to a set of
URIs. Relay 1 already has permissions to perform all the
translations but one. Relay 1 needs to obtain permission to perform
the translation to B.
Relay 2 returns a 470 (Consent Needed) response (message 5 in Figure
5) with a Permission-Needed header field. On reception of this
response, Relay 1 adds the URI identifying the first translation to
this header field (message 6 in Figure 5).
The UA inserts the two URIs received in the Permission-Needed header
field into the Permission-From header field of a new CONSENT request
(message 7 in Figure 5). Relay 1 consumes the URI it added when it
relays the CONSENT request to Relay 2 (message 8 in Figure 5). Relay
2 consumes the URI it added when it relays the CONSENT request to B
(message 9 in Figure 5).
A Relay1 Relay2 B
|(1) REQUEST friends@relay1 | |
|---------------->| | |
|(2) 470 Consent Needed | |
|Call-Info: 123@relay1; | |
|purpose=wait-permission | |
|Permission-Needed: xyz@relay1 | |
|<----------------| | |
|(3) CONSENT friends@relay1 | |
|Permission-From: xyz@relay1 | |
|---------------->| | |
| |(4) CONSENT school-friends@relay2 |
| |Permission-Requested: uri-req1 |
| |---------------->| |
| |(5) 470 Consent Needed |
| |Call-Info:456@relay2; |
| |purpose=wait-permission |
| |Permission-Needed: abc@relay2 |
| |<----------------| |
|(6) 470 Consent Needed | |
|Permission-Needed: xyz@relay1;abc@relay2 |
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|<----------------| | |
|(7) CONSENT friends@relay1 | |
|Permission-From: xyz@relay1;abc@relay2 |
|---------------->| | |
| |(8) CONSENT school-friends@relay2 |
| |Permission-Requested:uri-req1 |
| |Permission-From: abc@relay2 |
| |---------------->| |
| | |(9) CONSENT B |
| | |Permission-Requested: uri-req2
| | |---------------->|
| | |(10) 202 Accepted|
| | |<----------------|
| |(11) 202 Accepted| |
| |<----------------| |
|(12) 202 Accepted| | |
|<----------------| | |
|(13) SUBSCRIBE 123@relay1 | |
|---------------->| | |
|(14) 200 OK | | |
|<----------------| | |
|(15) NOTIFY (no permission) | |
|<----------------| | |
|(16) 200 OK | | |
|---------------->| | |
| | |(17) HTTP uri-req|
| | |Get Requested Permission
| | |<----------------|
| | |(18) 200 OK |
| | |Permission Document
| | |URI to Upload: uri-up2
| | |---------------->|
| | |(19) PUBLISH uri-up2
| | |Permission Document
| | |<----------------|
| | |(20) 200 OK |
| | |---------------->|
| |(21) HTTP uri-req1 |
| |Get Requested Permission |
| |<----------------| |
| |(22) 200 OK | |
| |Permission Document |
| |URI to Upload: uri-up1 |
| |---------------->| |
| |(23) PUBLISH uri-up1 |
| |Permission Document |
| |<----------------| |
| |(24) 200 OK | |
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| |---------------->| |
|(25) NOTIFY (permission) | |
|<----------------| | |
|(26) 200 OK | | |
|---------------->| | |
|(27) REQUEST friends@relay1 | |
|---------------->| | |
| |(28) REQUEST school-friends@relay2 |
| |Permission-Used: uri-perm1 |
| |---------------->| |
| | |(29) REQUEST B |
| | |Permission-Used: uri-perm1
| | |Permission-Used: uri-perm2
| | |---------------->|
Figure 5: Multiple-relay scenario
8.2 Waiting for Permissions
In order to be informed of the status of the permissions, A
subscribes (message 13 in Figure 5) to the URI it received from Relay
1 in a Call-Info header field (message 2 in Figure 5).
Although Figure 5 does not show it, Relay 1 could subscribe to the
status of the permissions at Relay 2 using the URI it received in a
Call-Info header field (message 5 in Figure 5).
8.3 Intermediate Relays
At this point, A needs to upload permissions to Relay 2 and Relay 2
needs to upload permissions to Relay 1. Therefore, Relay 2 acts as
an intermediate relay between B and Relay 1.
The policy followed by Relay 2 in Figure 5 is not to give permissions
to Relay 1 to perform the translation from friends@relay1 to
school-friends@relay2 until B gives Relay 2 permissions to perform
the translation school-friends@relay2 to B. However, this is not the
only possible policy. Relay 2 may choose to give permissions to
Relay 1 before B gave Relay 2 permissions. This would probably be
the case if Relay 2 was a forking proxy trying to locate a user
registered at several UAs, one of which had not given permissions to
the forking proxy yet.
Therefore, how a relay decides when to give certain permissions to
other relays is based on the local policy of the relay, which will
generally depend on the type of service provided by the relay.
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9. Installing Permissions in Advance
The previous sections described how a relay can request a target
resource owner to authorize a communication attempt. However, target
resource owners may want to authorize a particular translation in
advance. That is, before any communication attempt is performed.
To do so, the target resource owner sends a CONSENT request to the
target URI of the translation. This CONSENT request will trigger the
mechanisms described in the previous sections. The result is that
the target resource owner(s) will obtain a URI to upload a permission
document.
10. IANA Considerations
TBD.
11. Security Considerations
TBD.
Editor's note: we have to avoid that attackers provide permissions
for translations that apply to other users (e.g., allow everyone to
send traffic to a victim) and that attackers provide permissions for
a translation that apply to them but routes to a victim (e.g., 3rd
party registration that binds attacker@relay to victim@somewhere).
For the former we need authentication (e.g., SIP identity) and for
the latter we relay on the routing infrastructure to route CONSENTs
to the same place the traffic will be sent to once permissions are
obtained (i.e., a return routability test).
12. References
12.1 Normative References
[1] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A.,
Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP:
Session Initiation Protocol", RFC 3261, June 2002.
[2] Campbell, B., Rosenberg, J., Schulzrinne, H., Huitema, C. and D.
Gurle, "Session Initiation Protocol (SIP) Extension for Instant
Messaging", RFC 3428, December 2002.
12.2 Informative References
[3] Schulzrinne, H., "A Document Format for Expressing Privacy
Preferences", draft-ietf-geopriv-common-policy-03 (work in
progress), October 2004.
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[4] Peterson, J., "Enhancements for Authenticated Identity
Management in the Session Initiation Protocol (SIP)",
draft-ietf-sip-identity-03 (work in progress), September 2004.
[5] Rosenberg, J., "Requirements for Consent-Based Communications in
the Session Initiation Protocol (SIP)",
draft-ietf-sipping-consent-reqs-00 (work in progress), October
2004.
[6] Rosenberg, J., "Presence Authorization Rules",
draft-ietf-simple-presence-rules-01 (work in progress), October
2004.
[7] Camarillo, G., "Requirements and Framework for Session
Initiation Protocol (SIP)Uniform Resource Identifier (URI)-List
Services", draft-ietf-sipping-uri-services-01 (work in
progress), October 2004.
Authors' Addresses
Jonathan Rosenberg
Cisco Systems
600 Lanidex Plaza
Parsippany, NJ 07054
US
Phone: +1 973 952-5000
EMail: jdrosen@cisco.com
URI: http://www.jdrosen.net
Gonzalo Camarillo
Ericsson
Hirsalantie 11
Jorvas 02420
Finland
EMail: Gonzalo.Camarillo@ericsson.com
Dean Willis
Cisco Systems
2200 E. Pres. George Bush Turnpike
Richardson, TX 75082
USA
EMail: dean.willis@softarmor.com
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