draft-ietf-ecrit-data-only-ea-00.txt   draft-ietf-ecrit-data-only-ea-01.txt 
ECRIT B. Rosen ECRIT B. Rosen
Internet-Draft NeuStar, Inc. Internet-Draft NeuStar, Inc.
Intended status: Experimental H. Schulzrinne Intended status: Experimental H. Schulzrinne
Expires: March 25, 2011 Columbia U. Expires: April 28, 2011 Columbia U.
H. Tschofenig H. Tschofenig
Nokia Siemens Networks Nokia Siemens Networks
September 21, 2010 October 25, 2010
Common Alerting Protocol (CAP) based Data-Only Emergency Alerts using Common Alerting Protocol (CAP) based Data-Only Emergency Alerts using
the Session Initiation Protocol (SIP) the Session Initiation Protocol (SIP)
draft-ietf-ecrit-data-only-ea-00.txt draft-ietf-ecrit-data-only-ea-01.txt
Abstract Abstract
The Common Alerting Protocol (CAP) is an XML document format for The Common Alerting Protocol (CAP) is a document format for
exchanging emergency alerts and public warnings. CAP is mainly used exchanging emergency alerts and public warnings. CAP is mainly used
for conveying alerts and warnings between authorities and from for conveying alerts and warnings between authorities and from
authorities to citizen/individuals. This document describes how authorities to citizen/individuals. This document describes how
data-only emergency alerts allow to utilize the same CAP document data-only emergency alerts allow devices to issue alerts using the
format. CAP document format.
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 25, 2011. This Internet-Draft will expire on April 28, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 19 skipping to change at page 2, line 19
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Architectural Overview . . . . . . . . . . . . . . . . . . . . 5 3. Architectural Overview . . . . . . . . . . . . . . . . . . . . 5
4. Protocol Specification . . . . . . . . . . . . . . . . . . . . 7 4. Protocol Specification . . . . . . . . . . . . . . . . . . . . 7
4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 7 4.1. CAP Transport . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Profiling of the CAP Document Content . . . . . . . . . . 7 4.2. Profiling of the CAP Document Content . . . . . . . . . . 7
5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 10
6.1. Forgery . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Forgery . . . . . . . . . . . . . . . . . . . . . . . . . 10
6.2. Replay Attack . . . . . . . . . . . . . . . . . . . . . . 9 6.2. Replay Attack . . . . . . . . . . . . . . . . . . . . . . 10
6.3. Injecting False Alerts . . . . . . . . . . . . . . . . . . 9 6.3. Injecting False Alerts . . . . . . . . . . . . . . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. Registration of the 7.1. Registration of the
'application/common-alerting-protocol+xml' MIME type . . . 11 'application/common-alerting-protocol+xml' MIME type . . . 12
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 14
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction 1. Introduction
The Common Alerting Protocol (CAP) [cap] is an XML document format The Common Alerting Protocol (CAP) [cap] is an XML document format
for exchanging emergency alerts and public warnings. CAP is mainly for exchanging emergency alerts and public warnings. CAP is mainly
used for conveying alerts and warnings between authorities and from used for conveying alerts and warnings between authorities and from
authorities to citizen/individuals. This document describes how authorities to citizen/individuals. This document describes how
data-only emergency calls are able to utilize the same CAP document data-only emergency calls are able to utilize the same CAP document
format. Data-only emergency alerts may be similar to regular format.
emergency calls in the sense that they have the same emergency call
routing and location requirements; they do, however, not lead to the Data-only emergency alerts are similar to regular emergency calls in
establishment of a voice channel. There are, however, data-only the sense that they require emergency call routing functionality and
emergency alerts that are targeted directly to a dedicated entity may even have the same location requirements. On the other hand, the
initial communication interaction will not lead to the establishment
of a voice or video channel.
Based on the deployment experience with non-IP based systems we
distinguish between two types of environments, namely (1) data-only
emergency alerts that are targeted directly to a recipient
responsible for evaluating the alerts and for taking the necessary responsible for evaluating the alerts and for taking the necessary
steps, including triggering an emergency call towards a Public Safety steps, including triggering an emergency call towards a Public Safety
Answering Point (PSAP). Answering Point (PSAP) and (2) alerts that are targeted to a Service
URN as used for regular IP-based emergency calls where the recipient
is not known to the originator. We describe these two cases in more
detail in Section 3.
2. Terminology 2. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
This document utilizes terminology introduced in
[I-D.ietf-atoca-requirements].
3. Architectural Overview 3. Architectural Overview
This section illustrates two envisioned usage modes; targeted and This section illustrates two envisioned usage modes; targeted and
location-based emergency alert routing. Figure 1 shows a deployment location-based emergency alert routing. Figure 1 shows a deployment
variant where a device is pre-configured (using techniques outside variant where a sensor, as the author and originator of the alert, is
the scope of this document) to issue an alert to an aggregator that pre-configured (using techniques outside the scope of this document)
processes these messages and performs whatever steps are necessary to to issue an alert to a receiver or an aggregator, a special form of
appropriately react on the alert. In many cases the device has the mediator, that processes these messages and performs whatever steps
address of the aggregator pre-configured and corresponding security are necessary to appropriately react on the alert. For example, a
mechanisms are in place to ensure that only alert from authorized security firm may use different sensor inputs to dispatch their
devices are processed. security staff to a building they protect.
+--------+ +------------+ +------------+ +------------+
| Device | | Aggregator | | Sensor | | Aggregator |
+---+----+ +------+-----+ | | | |
+---+--------+ +------+-----+
| | | |
Sensors | Sensors |
trigger | trigger |
emergency | emergency |
alert | alert |
| MESSAGE with CAP | | MESSAGE with CAP |
|----------------------------->| |----------------------------->|
| | | |
| Aggregator | Aggregator
| processes | processes
| emergency | emergency
| alert | alert
| 200 (OK) | | 200 (OK) |
|<-----------------------------| |<-----------------------------|
| | | |
| | | |
Figure 1: Targeted Emergency Alert Routing Figure 1: Targeted Emergency Alert Routing
In Figure 2 a scenario is shown whereby the alert is routed using In Figure 2 a scenario is shown whereby the alert is routed using
location information and the Service URN. In this case the device location information and the Service URN. In case the LoST
issuing the alert may not know the message recipient (in case the resolution is done at an emergency services routing proxy rather than
LoST resolution is done at an emergency services routing proxy rather at the entity issuing the alert since it may not know the address of
than at the end host). In any case, a trust relationship between the the receiver. A possible receiver is a PSAP and the recipient of the
alert-issuing device and the PSAP cannot be assumed, i.e., the PSAP alert may be call taker. In the generic case, there is very likely
is likely to receive alerts from entities it cannot authorize. This no prior relationship between the originator and the receiver, e.g.
scenario corresponds more to the classical emergency services PSAP. A PSAP, for example, is likely to receive and accept alerts
classical and the description in [I-D.ietf-ecrit-phonebcp] is from entities it cannot authorize. This scenario corresponds more to
applicable. the classical emergency services use case and the description in
[I-D.ietf-ecrit-phonebcp] is applicable.
+-------+ +-----------+ +----------+
+--------+ | SIP | +------+ +--------+ | SIP Proxy | | PSAP as |
| Device | | Proxy | | PSAP | | Sensor | | as Relay | | Receiver |
+---+----+ +---+---+ +---+--+ +---+----+ +---+-------+ +---+------+
| | | | | |
Sensors | | Sensors | |
trigger | | trigger | |
emergency | | emergency | |
alert | | alert | |
| | | | | |
| | | | | |
| MESSAGE with CAP | | | MESSAGE with CAP | |
| (including Service URN, | | (including Service URN, |
| such as urn:service:sos) | | such as urn:service:sos) |
skipping to change at page 7, line 30 skipping to change at page 7, line 30
[cap]. For the usage with SIP the following additional requirements [cap]. For the usage with SIP the following additional requirements
are imposed: are imposed:
sender: When the CAP was created by a SIP-based entity then the sender: When the CAP was created by a SIP-based entity then the
element MUST be populated with the SIP URI of that entity. element MUST be populated with the SIP URI of that entity.
incidents: The <incidents> element MUST be present whenever there is incidents: The <incidents> element MUST be present whenever there is
a possibility that alert information needs to be updated. The a possibility that alert information needs to be updated. The
initial message will then contain an incident identifier carried initial message will then contain an incident identifier carried
in the <incidents> element. This incident identifier MUST be in the <incidents> element. This incident identifier MUST be
chosen in such a way that it is unique for a given sender / chosen in such a way that it is unique for a given <sender,
expires combination. expires, incidents> combination. Note that the <expires> element
is optional and may not be present.
scope: The value of the <scope> element MUST be set to "private" as scope: The value of the <scope> element MUST be set to "private" as
the alert is not meant for public consumption. The <addresses> the alert is not meant for public consumption. The <addresses>
element is, however, not used by this specification since the element is, however, not used by this specification since the
message routing is performed by SIP and the respective address message routing is performed by SIP and the respective address
information is already available there. Populating address information is already available in the geolocation header.
information twice into different parts of the message can quickly Populating location information twice into different parts of the
lead to inconsistency. message can quickly lead to inconsistency.
parameter: The <parameter> element MAY contain additional parameter: The <parameter> element MAY contain additional
information specific to the sensor. information specific to the sensor.
area: For geodetic information the polygon and circle location area: It is RECOMMENDED to omit this element when constructing a
shapes are available. The ability to conveying a structured message. In case that the CAP message already contained an <area>
format of civic location information is missing and hence civic element then the specified location information MUST be copied
information is encoded as a text string in the <areaDesc> element. into the PIDF-LO structure of the geolocation header element.
5. Example 5. Example
Figure 3 shows a CAP document indicating a BURLARY alert issued by Figure 3 shows a CAP document indicating a BURLARY alert issued by a
sensor1@example.com indicating that the alert was issued from the sensor with the identity 'sensor1@domain.com'. The location of the
civic address NATURAL HISTORY MUSEUM, BURGRING 7, 1010 VIENNA, sensor can be obtained from the attached geolocation information
AUSTRIA. Additionally, the sensor provided some additional data long provided via the geolocation header contained in the SIP MESSAGE
with the alert message using non-standardized information elements. structure. Additionally, the sensor provided some data long with the
alert message using proprietary information elements only to be
processed by the receiver, a SIP entity acting as an aggregator.
This example reflects the description in Figure 1.
<?xml version="1.0" encoding="UTF-8"?> MESSAGE sip:aggregator@domain.com SIP/2.0
Via: SIP/2.0/TCP sensor1.domain.com;branch=z9hG4bK776sgdkse
Max-Forwards: 70
From: sip:sensor1@domain.com;tag=49583
To: sip:aggregator@domain.com
Call-ID: asd88asd77a@1.2.3.4
Geolocation: <cid:abcdef@domain.com>
;routing-allowed=yes
Supported: geolocation
Accept: application/pidf+xml, application/common-alerting-protocol+xml
CSeq: 1 MESSAGE
Content-Type: multipart/mixed; boundary=boundary1
Content-Length: ...
<alert xmlns="urn:oasis:names:tc:emergency:cap:1.1"> --boundary1
<identifier>S-1</identifier>
<sender>sensor1@example.com</sender> Content-Type: common-alerting-protocol+xml
<sent>2008-11-19T14:57:00-07:00</sent> Content-ID: <abcdef2@domain.com>
<status>Actual</status> <?xml version="1.0" encoding="UTF-8"?>
<msgType>Alert</msgType>
<scope>Private</scope> <alert xmlns="urn:oasis:names:tc:emergency:cap:1.1">
<incidents>abc1234</incidents> <identifier>S-1</identifier>
<info> <sender>sip:sensor1@domain.com</sender>
<category>Security</category> <sent>2008-11-19T14:57:00-07:00</sent>
<event>BURGLARY</event> <status>Actual</status>
<urgency>Expected</urgency> <msgType>Alert</msgType>
<certainty>Likely</certainty> <scope>Private</scope>
<severity>Moderate</severity> <incidents>abc1234</incidents>
<senderName>SENSOR 1</senderName> <info>
<area> <category>Security</category>
<areaDesc>NATURAL HISTORY MUSEUM, <event>BURGLARY</event>
BURGRING 7, 1010 VIENNA, AUSTRIA <urgency>Expected</urgency>
</areaDesc> <certainty>Likely</certainty>
</area> <severity>Moderate</severity>
<parameter> <senderName>SENSOR 1</senderName>
<valueName>SENSOR-DATA-NAMESPACE1</valueName> <parameter>
<value>123</value> <valueName>SENSOR-DATA-NAMESPACE1</valueName>
</parameter> <value>123</value>
<parameter> </parameter>
<valueName>SENSOR-DATA-NAMESPACE2</valueName> <parameter>
<value>TRUE</value> <valueName>SENSOR-DATA-NAMESPACE2</valueName>
</parameter> <value>TRUE</value>
</info> </parameter>
</info>
</alert> </alert>
Figure 3: Example for an alert triggered by a sensor --boundary1
Content-Type: application/pidf+xml
Content-ID: <abcdef2@domain.com>
<?xml version="1.0" encoding="UTF-8"?>
<presence xmlns="urn:ietf:params:xml:ns:pidf"
xmlns:gp="urn:ietf:params:xml:ns:pidf:geopriv10"
xmlns:cl="urn:ietf:params:xml:ns:pidf:geopriv10:civicAddr"
xmlns:gml="http://www.opengis.net/gml"
entity="pres:sensor1@domain.com">
<tuple id="12345">
<dm:device id="sensor1">
<gp:geopriv>
<gp:location-info>
<gml:location>
<gml:Point srsName="urn:ogc:def:crs:EPSG::4326">
<gml:pos>32.86726 -97.16054</gml:pos>
</gml:Point>
</gml:location>
</gp:location-info>
<gp:usage-rules>
<gp:retransmission-allowed>yes
</gp:retransmission-allowed>
<gp:retention-expiry>2010-07-30T20:00:00Z
</gp:retention-expiry>
</gp:usage-rules>
<gp:method>802.11</gp:method>
</gp:geopriv>
<dm:deviceID>mac:1234567890ab</dm:deviceID>
<dm:timestamp>2010-07-28T20:57:29Z</dm:timestamp>
</dm:device>
</tuple>
</presence>
--boundary1--
Figure 3: Example Message conveying an Alert
6. Security Considerations 6. Security Considerations
This section discusses security considerations when using SIP to make This section discusses security considerations when using SIP to make
data-only emergency alerts utilizing CAP. data-only emergency alerts utilizing CAP. Location specific threats
are not unique to this document and the discussion in
[I-D.ietf-ecrit-trustworthy-location].
6.1. Forgery 6.1. Forgery
Threat: Threat:
An adversary could forge or alter a CAP document to report false An adversary could forge or alter a CAP document to report false
emergency alarms. emergency alarms.
Countermeasures: Countermeasures:
skipping to change at page 9, line 30 skipping to change at page 10, line 32
mechanisms for protecting the CAP documents are employed, e.g., mechanisms for protecting the CAP documents are employed, e.g.,
signing the CAP document itself. Section 3.3.2.1 of [cap] signing the CAP document itself. Section 3.3.2.1 of [cap]
specifies the signing of CAP documents. This does not protect specifies the signing of CAP documents. This does not protect
against a legitimate sensor sending phrank alerts after being against a legitimate sensor sending phrank alerts after being
compromised. compromised.
6.2. Replay Attack 6.2. Replay Attack
Threat: Threat:
Theft of CAP documents described in this document and replay of it An adversary could eavesdrop alerts and reply them at a later
at a later time. time.
Countermeasures: Countermeasures:
A CAP document contains the mandatory <identifier>, <sender>, A CAP document contains the mandatory <identifier>, <sender>,
<sent> elements and an optional <expire> element. These <sent> elements and an optional <expire> element. These
attributes make the CAP document unique for a specific sender and attributes make the CAP document unique for a specific sender and
provide time restrictions. An entity that has received a CAP provide time restrictions. An entity that has received a CAP
message already within the indicated timeframe is able to detect a message already within the indicated timeframe is able to detect a
replayed message and, if the content of that message is unchanged, replayed message and, if the content of that message is unchanged,
then no additional security vulnerability is created. then no additional security vulnerability is created.
Additionally, it is RECOMMENDED to make use of SIP security Additionally, it is RECOMMENDED to make use of SIP security
mechanisms, such as SIP Identity, to tie the CAP message to the mechanisms, such as SIP Identity [RFC4474], to tie the CAP message
SIP message. to the SIP message.
6.3. Injecting False Alerts 6.3. Injecting False Alerts
Threat: Threat:
When an entity receives a CAP message it has to determine whether When an entity receives a CAP message it has to determine whether
the entity distributing the CAP messages is genuine to avoid the entity distributing the CAP messages is genuine to avoid
accepting messages that are injected by adversaries. accepting messages that are injected by adversaries. In scenario
Countermeasures: Countermeasures:
For some types of data-only emergency calls the entity issuing the For some types of data-only emergency calls author/originator and
alert and the entity consuming the alert have a relationship with the receiver/recipient have a relationship with each other and
each other and hence it is possible (using cryptographic hence it is possible (using cryptographic techniques) to verify
authentication ) to verify whether a message was indeed issued by whether a message was indeed issued by an authorized entity.
an authorized entity. There are, however, other types of data- Figure 1 is such an environment. Standard SIP security mechanisms
only emergency calls where there is no such relationship between can be re-used for this purpose. For example, identity based
the sender and the consumer. In that case incoming alerts need to access control is a viable approach utilizing the asserted
be treated more carefully, as the possibilities to place phrank identity of the alert originator using P-Asserted-Identity
calls are higher than with regular emergency calls that at least [RFC3325] or SIP Identity [RFC4474].
setup an audio channel.
There are, however, other types of data-only emergency calls where
there is no such relationship between the author/originator and
the receiver/recipient. Incoming alerts need to be treated more
carefully than multi-media emergency calls that contain additional
information, such as audio, to allow a call taker to sort out
phrank calls.
7. IANA Considerations 7. IANA Considerations
7.1. Registration of the 'application/common-alerting-protocol+xml' 7.1. Registration of the 'application/common-alerting-protocol+xml'
MIME type MIME type
To: ietf-types@iana.org To: ietf-types@iana.org
Subject: Registration of MIME media type application/ common- Subject: Registration of MIME media type application/ common-
alerting-protocol+xml alerting-protocol+xml
skipping to change at page 14, line 27 skipping to change at page 15, line 27
[RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension [RFC3903] Niemi, A., "Session Initiation Protocol (SIP) Extension
for Event State Publication", RFC 3903, October 2004. for Event State Publication", RFC 3903, October 2004.
[RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media [RFC3023] Murata, M., St. Laurent, S., and D. Kohn, "XML Media
Types", RFC 3023, January 2001. Types", RFC 3023, January 2001.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
[I-D.ietf-ecrit-trustworthy-location]
Tschofenig, H., Schulzrinne, H., and B. Aboba,
"Trustworthy Location Information",
draft-ietf-ecrit-trustworthy-location-01 (work in
progress), October 2010.
9.2. Informative References 9.2. Informative References
[I-D.ietf-ecrit-phonebcp] [I-D.ietf-ecrit-phonebcp]
Rosen, B. and J. Polk, "Best Current Practice for Rosen, B. and J. Polk, "Best Current Practice for
Communications Services in support of Emergency Calling", Communications Services in support of Emergency Calling",
draft-ietf-ecrit-phonebcp-15 (work in progress), draft-ietf-ecrit-phonebcp-15 (work in progress),
July 2010. July 2010.
[I-D.ietf-atoca-requirements]
Schulzrinne, H., Norreys, S., Rosen, B., and H.
Tschofenig, "Requirements, Terminology and Framework for
Exigent Communications", draft-ietf-atoca-requirements-00
(work in progress), September 2010.
[RFC4474] Peterson, J. and C. Jennings, "Enhancements for
Authenticated Identity Management in the Session
Initiation Protocol (SIP)", RFC 4474, August 2006.
[RFC3325] Jennings, C., Peterson, J., and M. Watson, "Private
Extensions to the Session Initiation Protocol (SIP) for
Asserted Identity within Trusted Networks", RFC 3325,
November 2002.
Authors' Addresses Authors' Addresses
Brian Rosen Brian Rosen
NeuStar, Inc. NeuStar, Inc.
470 Conrad Dr 470 Conrad Dr
Mars, PA 16046 Mars, PA 16046
US US
Phone: Phone:
Email: br@brianrosen.net Email: br@brianrosen.net
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