< draft-ietf-geopriv-policy-uri-04.txt   draft-ietf-geopriv-policy-uri-05.txt >
GEOPRIV R. Barnes GEOPRIV R. Barnes
Internet-Draft BBN Technologies Internet-Draft BBN Technologies
Intended status: Standards Track M. Thomson Intended status: Standards Track M. Thomson
Expires: May 31, 2012 J. Winterbottom Expires: March 24, 2013 Microsoft
J. Winterbottom
Andrew Corporation Andrew Corporation
H. Tschofenig H. Tschofenig
Nokia Siemens Networks Nokia Siemens Networks
November 28, 2011 September 20, 2012
Location Configuration Extensions for Policy Management Location Configuration Extensions for Policy Management
draft-ietf-geopriv-policy-uri-04.txt draft-ietf-geopriv-policy-uri-05.txt
Abstract Abstract
Current location configuration protocols are capable of provisioning Current location configuration protocols are capable of provisioning
an Internet host with a location URI that refers to the host's an Internet host with a location URI that refers to the host's
location. These protocols lack a mechanism for the target host to location. These protocols lack a mechanism for the target host to
inspect or set the privacy rules that are applied to the URIs they inspect or set the privacy rules that are applied to the URIs they
distribute. This document extends the current location configuration distribute. This document extends the current location configuration
protocols to provide hosts with a reference to the rules that are protocols to provide hosts with a reference to the rules that are
applied to a URI, so that the host can view or set these rules. applied to a URI, so that the host can view or set these rules.
skipping to change at page 1, line 40 skipping to change at page 1, line 41
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
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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 May 31, 2012. This Internet-Draft will expire on March 24, 2013.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Policy URIs . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Policy URIs . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Policy URI Usage . . . . . . . . . . . . . . . . . . . . . 5 3.1. Policy URI Usage . . . . . . . . . . . . . . . . . . . . . 5
3.2. Policy URI Allocation . . . . . . . . . . . . . . . . . . 6 3.2. Policy URI Allocation . . . . . . . . . . . . . . . . . . 6
4. Location Configuration Extensions . . . . . . . . . . . . . . 7 3.3. Policy Defaults . . . . . . . . . . . . . . . . . . . . . 7
4.1. HELD . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Location Configuration Extensions . . . . . . . . . . . . . . 8
4.2. DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.3. Client Processing . . . . . . . . . . . . . . . . . . . . 8 5.1. HELD . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 5.2. Basic Access Control Policy . . . . . . . . . . . . . . . 9
5.1. HELD . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
5.2. DHCP . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5.3. Basic Access Control Policy . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
6.1. URN Sub-Namespace Registration for 6.1. URN Sub-Namespace Registration for
urn:ietf:params:xml:ns:geopriv:held:policy . . . . . . . . 12 urn:ietf:params:xml:ns:geopriv:held:policy . . . . . . . . 12
6.2. XML Schema Registration . . . . . . . . . . . . . . . . . 12 6.2. XML Schema Registration . . . . . . . . . . . . . . . . . 12
6.3. DHCP LuriType Registration . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7.1. Integrity and Confidentiality for Authorization Policy 7.1. Integrity and Confidentiality for Authorization Policy
Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7.2. Access Control for Authorization Policy . . . . . . . . . 14 7.2. Access Control for Authorization Policy . . . . . . . . . 13
7.3. Location URI Allocation . . . . . . . . . . . . . . . . . 14 7.3. Location URI Allocation . . . . . . . . . . . . . . . . . 15
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 7.4. Policy URI Handling . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
9.1. Normative References . . . . . . . . . . . . . . . . . . . 15 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.2. Informative References . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 9.2. Informative References . . . . . . . . . . . . . . . . . . 17
Appendix A. Example Policy URI Generation Algorithm . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction 1. Introduction
A critical step in enabling Internet hosts to access location-based A critical step in enabling Internet hosts to access location-based
services is to provision those hosts with information about their own services is to provision those hosts with information about their own
location. This is accomplished via a Location Configuration Protocol location. This is accomplished via a Location Configuration Protocol
(LCP) [RFC5687], which allows a location provider (e.g., a local (LCP) [RFC5687], which allows a location provider (e.g., a local
access network) to inform a host about its location. access network) to inform a host about its location.
There are two basic patterns for location configuration, namely There are two basic patterns for location configuration, namely
configuration "by value" and "by reference" [RFC5808]. Configuration configuration "by value" and "by reference" [RFC5808]. Configuration
by value provisions a host directly with its location, by providing by value provisions a host directly with its location, by providing
it location information that is directly usable (e.g., coordinates or it location information that is directly usable (e.g., coordinates or
a civic address). Configuration by reference provides a host with a a civic address). Configuration by reference provides a host with a
URI that references the host's location, i.e., one that can be URI that references the host's location, i.e., one that can be
dereferenced to obtain the location (by value) of the host. dereferenced to obtain the location (by value) of the host.
In some cases, location by reference offers a few benefits over In some cases, location by reference offers a few benefits over
location by value. From a privacy perspective, the required location by value. From a privacy perspective, the required
dereference transaction provides a policy enforcement point, so that dereference transaction provides a policy enforcement point, so that
the opaque URI itself can be safely conveyed over untrusted media if suitable privacy policies have been provisioned, the opaque
(e.g., SIP through untrusted proxies [RFC5606]). If the target host location URI can be safely conveyed over untrusted media. (If the
is mobile, an application provider can use a single reference to location URI is not subject to privacy rules, then conveying the
obtain the location of the host multiple times, saving bandwidth to location URI may pose even greater risk than sending location by
the host. For some configuration protocols, the location object value [RFC5606]) If the target host is mobile, an application
referenced by a location URI provides a much more expressive syntax provider can use a single reference to obtain the location of the
for location values than the configuration protocol itself (e.g., host multiple times, saving bandwidth to the host. For some
DHCP geodetic location [RFC6225] versus GML in a PIDF-LO [RFC4119]). configuration protocols, the location object referenced by a location
URI provides a much more expressive syntax for location values than
the configuration protocol itself (e.g., DHCP geodetic location
[RFC6225] versus GML in a PIDF-LO [RFC4119]).
From a privacy perspective, however, current LCPs are limited in From a privacy perspective, however, current LCPs are limited in
their flexibility, in that they do not provide hosts (the clients in their flexibility, in that they do not provide hosts (the clients in
an LCP) with a way to inform the Location Server with policy for how an LCP) with a way to inform the Location Server with policy for how
his location information should be handled. This document addresses his location information should be handled. This document addresses
this gap by defining a simple mechanism for referring to and this gap by defining a simple mechanism for referring to and
manipulating policy, and by extending current LCPs to carry policy manipulating policy, and by extending current LCPs to carry policy
references. Using the mechanisms defined in this document, an LCP references. Using the mechanisms defined in this document, an LCP
server (acting for the Location Server (LS) or Location Information server (acting for the Location Server (LS) or Location Information
Server (LIS)) can inform a host as to which policy document controls Server (LIS)) can inform a host as to which policy document controls
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| | | | | |
+------+----+----+----+ | +------+----+----+----+ |
| Rule | Target/ | | | Rule | Target/ | |
| Maker | Host +---------------------+ | Maker | Host +---------------------+
| | | | | |
+-----------+---------+ +-----------+---------+
The remainder of this document is structured as follows: After The remainder of this document is structured as follows: After
introducing a few relevant terms, we define policy URIs as a channel introducing a few relevant terms, we define policy URIs as a channel
for referencing, inspecting, and updating policy documents. We then for referencing, inspecting, and updating policy documents. We then
define extensions to the HELD protocol and the DHCP option for define an extension to the HELD protocol to carry policy URIs.
location by reference to allow these protocols to carry policy URIs.
Examples are given that demonstrate how policy URIs are carried in Examples are given that demonstrate how policy URIs are carried in
these protocols and how they can be used by clients. these protocols and how they can be used by clients.
2. Definitions 2. Definitions
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].
3. Policy URIs 3. Policy URIs
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GET, PUT, and DELETE requests to these URIs, in order to allow GET, PUT, and DELETE requests to these URIs, in order to allow
clients to inspect, replace, and delete policy documents. Clients clients to inspect, replace, and delete policy documents. Clients
support the three request methods as they desire to perform these support the three request methods as they desire to perform these
operations. operations.
Knowledge of the policy URI can be considered adequate evidence of Knowledge of the policy URI can be considered adequate evidence of
authorization; a policy URI functions as a shared secret between the authorization; a policy URI functions as a shared secret between the
client and the server (see Section 7). A Location Server SHOULD client and the server (see Section 7). A Location Server SHOULD
allow all requests, but it MAY deny certain requests based on local allow all requests, but it MAY deny certain requests based on local
policy. For instance, a Location Server might allow clients to policy. For instance, a Location Server might allow clients to
inspect policy (GET), but not to update it (PUT). inspect policy (GET), but not to update it (PUT). Or a Location
Server might require clients to authenticate using HTTP or TLS client
authentication. Clients implementing this specification SHOULD
support HTTP client authentication [RFC2617] and MAY support TLS
client certificates.
A GET request to a policy URI is a request for the referenced policy A GET request to a policy URI is a request for the referenced policy
information. If the request is authorized, then the Location Server information. If the request is authorized, then the Location Server
sends an HTTP 200 response containing the complete policy identified sends an HTTP 200 response containing the complete policy identified
by the URI. by the URI.
A PUT request to a policy URI is a request to replace the current A PUT request to a policy URI is a request to replace the current
policy. The entity-body of a PUT request includes a complete policy policy. The entity-body of a PUT request includes a complete policy
document. When a Location Server receives a PUT request, it MUST document. When a Location Server receives a PUT request, it MUST
validate the policy document included in the body of the request. If validate the policy document included in the body of the request. If
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A DELETE request to a policy URI is a request to delete the A DELETE request to a policy URI is a request to delete the
referenced policy document. If the request is authorized, then the referenced policy document. If the request is authorized, then the
Location Server MUST delete the policy referenced by the URI and Location Server MUST delete the policy referenced by the URI and
disallow access to the location URIs it governs until a new policy disallow access to the location URIs it governs until a new policy
document has been put in place via a PUT request. document has been put in place via a PUT request.
A policy URI is only valid while the corresponding location URI set A policy URI is only valid while the corresponding location URI set
is valid. A location server MUST NOT respond to any requests to a is valid. A location server MUST NOT respond to any requests to a
policy URIs once the corresponding location URI set has expired. policy URIs once the corresponding location URI set has expired.
This expiry time is specified by the 'expires' attribute in the HELD This expiry time is specified by the 'expires' attribute in the HELD
locationResponse or the 'Valid-For' LuriType in DHCP. locationResponse.
A location URI can thus become invalid in three ways: By the A location URI can thus become invalid in three ways: By the
expiration of a validity interval in policy, by the removal of a expiration of a validity interval in policy, by the removal of a
policy document with a DELETE request, or by the expiry of the policy document with a DELETE request, or by the expiry of the
LCP-specified validity interval. The former two are temporary, LCP-specified validity interval. The former two are temporary,
since the policy URI can be used to update the policy. The latter since the policy URI can be used to update the policy. The latter
one is permanent, since the expiry causes the policy URI to be one is permanent, since the expiry causes the policy URI to be
invalidated as well. invalidated as well.
The Location Server MUST support policy documents in the common- The Location Server MUST support policy documents in the common-
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configuration, for example, in responses to dereferencing requests configuration, for example, in responses to dereferencing requests
[I-D.ietf-geopriv-deref-protocol] or requests from third parties [I-D.ietf-geopriv-deref-protocol] or requests from third parties
[RFC6155]. [RFC6155].
Each location URI has either one policy URI or no policy URI. The Each location URI has either one policy URI or no policy URI. The
initial policy that is referenced by a policy URI MUST be identical initial policy that is referenced by a policy URI MUST be identical
to the policy that would be applied in the absence of a policy URI. to the policy that would be applied in the absence of a policy URI.
A client that does not support policy URIs can continue to use the A client that does not support policy URIs can continue to use the
location URI as they would have if no policy URI were provided. location URI as they would have if no policy URI were provided.
For DHCP and HELD, the client assumes that the default policy For HELD, the client assumes that the default policy grants any
grants any requester access to location information, as long as requester access to location information, as long as the requestor
the request possesses the location URI. To ensure that the possesses the location URI. To ensure that the authorization
authorization policy is less permissive, a client updates the policy is less permissive, a client updates the policy prior to
policy prior to distributing the location URI. distributing the location URI.
A Location Server chooses whether or not to provide a policy URI A Location Server chooses whether or not to provide a policy URI
based on local policy. A HELD-specific extension also allows a based on local policy. A HELD-specific extension also allows a
requester to specifically ask for a policy URI. requester to specifically ask for a policy URI.
A policy URI is effectively a shared secret between Location Server A policy URI is effectively a shared secret between Location Server
and its clients. Knowledge of a policy URI is all that is required and its clients. Knowledge of a policy URI is all that is required
to perform any operations allowed on the policy. Thus, a policy URI to perform any operations allowed on the policy. Thus, a policy URI
should be constructed so that it is hard to predict and should be constructed so that it is hard to predict and
confidentiality-protected when transmitted (see Section 7). To avoid confidentiality-protected when transmitted (see Section 7). To avoid
re-using these shared secrets, the Location Server MUST generate a re-using these shared secrets, the Location Server MUST generate a
new policy URI whenever it generates a new location URI set. new policy URI whenever it generates a new location URI set.
3.3. Policy Defaults
Client implementors should keep in mind that setting no policy (never
performing an HTTP request to a policy URI) is very different from
setting an empty policy (performing a PUT with the empty policy). By
"the empty policy", we mean a policy containing no rules, which would
be represented by the following policy document:
<?xml version="1.0" encoding="UTF-8"?>
<ruleset xmlns="urn:ietf:params:xml:ns:common-policy">
</ruleset>
Figure 1: The empty policy
If no policy is set, then the client tacitly accepts whatever policy
the server applies to location URIs, including a policy that provides
location to anyone that makes a dereference request. If the empty
policy is set, then the opposite is true; the client directs the
server to never provide access to location. (Since there are no
rules to allow access, and the policy language is default-deny.)
Implementors should thus consider carefully how to handle the case
where the user provides no privacy policy input. On the one hand, an
implementation might treat this case as if the user had no privacy
preferences, and thus set no policy. On the other hand, another
implementation might decide that if a user provides no positive
authorization, then the empty policy should be installed.
The same reasoning could also be applied to servers, with the caveat
that servers do not know whether a given HELD client supports the use
of policy URIs. A client that does not understand policy URIs will
not be able to set its own policy, and so the server must choose a
default that is open enough that clients will find it useful. On the
other hand, once a client indicates that it understands policy URIs
(e.g., by sending an HTTP request to a policy URI), the server may
change its default policy to something more restrictive -- even the
empty, default-deny policy -- since the client can specify something
more permissive if desired.
4. Location Configuration Extensions 4. Location Configuration Extensions
Location configuration protocols can provision hosts with location Location configuration protocols can provision hosts with location
URIs that refer to the host's location. If the target host is to URIs that refer to the host's location. If the target host is to
control policy on these URIs, it needs a way to access the policy control policy on these URIs, it needs a way to access the policy
that the Location Server uses to guide how it serves location URIs. that the Location Server uses to guide how it serves location URIs.
This section defines extensions to LCPs to carry policy URIs that the This section defines extensions to the HELD LCP to carry policy URIs
target can use to control access to location resources. that the target can use to control access to location resources.
4.1. HELD
The HELD protocol [RFC5985] defines a "locationUriSet" element, which The HELD protocol [RFC5985] defines a "locationUriSet" element, which
contain a set of one or more location URIs that reference the same contain a set of one or more location URIs that reference the same
resource and share a common access control policy. The schema in resource and share a common access control policy. The schema in
Figure 1 defines two extension elements for HELD: an empty Figure 2 defines two extension elements for HELD: an empty
"requestPolicyUri" element that is added to a location request to "requestPolicyUri" element that is added to a location request to
indicate that a Device desires that a policy URI be allocated; and a indicate that a Device desires that a policy URI be allocated; and a
"policyUri" element that is included in the location response. "policyUri" element that is included in the location response.
<?xml version="1.0" encoding="UTF-8"?> <?xml version="1.0" encoding="UTF-8"?>
<xs:schema <xs:schema
targetNamespace="urn:ietf:params:xml:ns:geopriv:held:policy" targetNamespace="urn:ietf:params:xml:ns:geopriv:held:policy"
xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:hp="urn:ietf:params:xml:ns:geopriv:held:policy" xmlns:hp="urn:ietf:params:xml:ns:geopriv:held:policy"
elementFormDefault="qualified" attributeFormDefault="unqualified"> elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:element name="requestPolicyUri"> <xs:element name="requestPolicyUri">
<xs:complexType name="empty"/> <xs:complexType name="empty"/>
</xs:element> </xs:element>
<xs:element name="policyUri" type="xs:anyURI"/> <xs:element name="policyUri" type="xs:anyURI"/>
</xs:schema> </xs:schema>
Figure 1 Figure 2: XML Schema for the policy URI extension
The URI carried in a "policyUri" element refers to the common access The URI carried in a "policyUri" element refers to the common access
control policy for location URIs in the location response. The URI control policy for location URIs in the location response. The URI
MUST be a policy URI as described in Section 3. A policy URI MUST MUST be a policy URI as described in Section 3. A policy URI MUST
use the "http:" or "https:" scheme, and the Location Server MUST use the "http:" or "https:" scheme, and the Location Server MUST
support the specified operations on the URI. support the specified operations on the URI.
A HELD request MAY contain an explicit request for a policy URI. The A HELD request MAY contain an explicit request for a policy URI. The
presence of the "requestPolicyUri" element in a location request presence of the "requestPolicyUri" element in a location request
indicates that a policy URI is desired. indicates that a policy URI is desired.
4.2. DHCP
The DHCP location by reference option
[I-D.ietf-geopriv-dhcp-lbyr-uri-option] provides location URIs in
sub-options called LuriElements. This document defines a new
LuriElement type for policy URIs.
LuriType=TBD Policy-URI - This is a policy URI that refers to the
access control policy for the location URIs.
[NOTE TO IANA/RFC-EDITOR: Please replace TBD above with the assigned
LuriType value and remove this note]
A Policy-URI LuriElement uses a UTF-8 character encoding.
A Policy-URI LuriElement identifies the policy resource for all
location URIs included in the location URI option. The URI MUST be a
policy URI as described in Section 3: It MUST use either the "http:"
or "https:" scheme, and the Location Server MUST support the
specified operations on the URI.
4.3. Client Processing
It is possible that this document will be updated to allow the use of It is possible that this document will be updated to allow the use of
policy URIs that use protocols other than the HTTP-based protocol policy URIs that use policy-management protocols other than the HTTP-
described above. To ensure that they fail safely when presented with based protocol described above. To ensure that they fail safely when
such a URI, clients implementing this specification MUST verify that presented with such a URI, clients implementing this specification
a policy URI received from either HELD or DHCP uses either the MUST verify that a policy URI received from an LCP uses either the
"http:" or "https:" scheme. If the URI does not match those schemes, "http:" or "https:" scheme. If the URI does not match those schemes,
then the client MUST discard the URI and behave as if no policy URI then the client MUST discard the URI and behave as if no policy URI
was provided. was provided.
5. Examples 5. Examples
In this section, we provide some brief illustrations of how policy In this section, we provide some brief illustrations of how policy
URIs are delivered to target hosts and used by those hosts to manage URIs are delivered to target hosts and used by those hosts to manage
policy. policy.
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</locationURI> </locationURI>
<locationURI> <locationURI>
sip:9769+357yc6s64ceyoiuy5ax3o@ls.example.com: sip:9769+357yc6s64ceyoiuy5ax3o@ls.example.com:
</locationURI> </locationURI>
</locationUriSet> </locationUriSet>
<policyUri xmlns="urn:ietf:params:xml:ns:geopriv:held:policy"> <policyUri xmlns="urn:ietf:params:xml:ns:geopriv:held:policy">
https://ls.example.com:9768/policy/357lp6f64prlbvhl5nk3b https://ls.example.com:9768/policy/357lp6f64prlbvhl5nk3b
</policyUri> </policyUri>
</locationResponse> </locationResponse>
5.2. DHCP 5.2. Basic Access Control Policy
A DHCP option providing one of the location URIs and the
corresponding policy URI from the previous example would have the
following form:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| option-code | 110 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 1 | 0 | 1 | 49 | 'h' |
+---------------+---------------+---------------+---------------|
| 't' | 't' | 'p' | 's' |
+---------------+---------------+---------------+---------------|
| ':' | '/' | '/' | 'l' |
+---------------+---------------+---------------+---------------|
| 's' | '.' | ... |
+---------------+---------------+---------------+---------------|
| TBD | 56 | 'h' 't' |
+---------------+---------------+---------------+---------------|
| 't' | 'p' | 's' | ':' |
+---------------+---------------+---------------+---------------|
| '/' | '/' | ... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
[NOTE TO IANA/RFC-EDITOR: Please replace TBD above with the assigned
LuriType value and remove this note]
5.3. Basic Access Control Policy
Consider a client that gets the policy URI Consider a client that gets the policy URI
<https://ls.example.com:9768/policy/357lp6f64prlbvhl5nk3b>, as in the <https://ls.example.com:9768/policy/357lp6f64prlbvhl5nk3b>, as in the
above LCP example. The first thing this allows the client to do is above LCP example. The first thing this allows the client to do is
inspect the default policy that the LS has assigned to this URI: inspect the default policy that the LS has assigned to this URI:
GET /policy/357lp6f64prlbvhl5nk3b HTTP/1.1 GET /policy/357lp6f64prlbvhl5nk3b HTTP/1.1
Host: ls.example.com:9768 Host: ls.example.com:9768
HTTP/1.1 200 OK HTTP/1.1 200 OK
skipping to change at page 12, line 47 skipping to change at page 12, line 47
6.2. XML Schema Registration 6.2. XML Schema Registration
This section registers an XML schema as per the guidelines in This section registers an XML schema as per the guidelines in
[RFC3688]. [RFC3688].
URI: urn:ietf:params:xml:schema:geopriv:held:policy URI: urn:ietf:params:xml:schema:geopriv:held:policy
Registrant Contact: IETF, GEOPRIV working group (geopriv@ietf.org), Registrant Contact: IETF, GEOPRIV working group (geopriv@ietf.org),
Richard Barnes (rbarnes@bbn.com) Richard Barnes (rbarnes@bbn.com)
Schema: The XML for this schema can be found in Section Section 4.1. Schema: The XML for this schema can be found in Section Section 4.
6.3. DHCP LuriType Registration
IANA is requested to add a value to the LuriTypes registry, as
follows:
+------------+----------------------------------------+-----------+
| LuriType | Name | Reference |
+------------+----------------------------------------+-----------+
| TBD* | Policy-URI | RFC XXXX**|
+------------+----------------------------------------+-----------+
* TBD is to be replaced with the assigned value
** RFC XXXX is to be replaced with this document's RFC number.
7. Security Considerations 7. Security Considerations
There are two main classes of risks associated with access control There are two main classes of risks associated with access control
policy management: The risk of unauthorized grants or denial of policy management: The risk of unauthorized grants or denial of
access to the protected resource via manipulation of the policy access to the protected resource via manipulation of the policy
management process, and the risk of disclosure of policy information management process, and the risk of disclosure of policy information
itself. itself.
Protecting the policy management process from manipulation entails Protecting the policy management process from manipulation entails
two primary requirements: First, the policy URI has to be faithfully two primary requirements: First, the policy URI has to be faithfully
and confidentially transmitted to the client, and second, the policy and confidentially transmitted to the client, and second, the policy
document has to be faithfully and confidentially transmitted to the document has to be faithfully and confidentially transmitted to the
Location Server. The mechanism also needs to ensure that only Location Server. The mechanism also needs to ensure that only
authorized entities are able to acquire or alter policy. authorized entities are able to acquire or alter policy.
7.1. Integrity and Confidentiality for Authorization Policy Data 7.1. Integrity and Confidentiality for Authorization Policy Data
Each LCP ensures integrity and confidentiality through different Each LCP ensures integrity and confidentiality through different
means (see [RFC5985] and [I-D.ietf-geopriv-dhcp-lbyr-uri-option]). means (see, for example, [RFC5985]). These measures ensure that a
These measures ensure that a policy URI is conveyed to the client policy URI is conveyed to the client without modification or
without modification or interception. interception.
To protect the integrity and confidentiality of policy data during In general, the requirements for transport-layer security on policy
management, the Location Server SHOULD provide policy URIs with the transactions are the same as for the dereference transactions they
"https:" scheme and require the use of HTTP over TLS [RFC2818]. The set policy for [I-D.ietf-geopriv-deref-protocol]. To protect the
cipher suites required by TLS [RFC5246] provide both integrity integrity and confidentiality of policy data during management, the
protection and confidentiality. If other means of protection are Location Server SHOULD provide policy URIs with the "https:" scheme
available, an "http:" URI MAY be used, but location servers SHOULD and require the use of HTTP over TLS [RFC2818]. The cipher suites
reject PUT and DELETE requests for policy URIs that use the "http:" required by TLS [RFC5246] provide both integrity protection and
URI scheme. confidentiality. If other means of protection are available, an
"http:" URI MAY be used, but location servers SHOULD reject PUT and
DELETE requests for policy URIs that use the "http:" URI scheme.
7.2. Access Control for Authorization Policy 7.2. Access Control for Authorization Policy
Access control for the policy resource is based on knowledge of its Access control for the policy resource is based on knowledge of its
URI. The URI of a policy resource operates under the same URI. The URI of a policy resource operates under the same
constraints as a possession model location URI [RFC5808] and is constraints as a possession model location URI [RFC5808] and is
subject to the same constraints: subject to the same constraints:
o Knowledge of a policy URI MUST be restricted to authorized Rule o Knowledge of a policy URI MUST be restricted to authorized Rule
Makers. ConfideConfidentiality and integrity protections SHOULD Makers. Confidentiality and integrity protections SHOULD be used
be used when policy URIs are conveyed in a location configuration when policy URIs are conveyed in a location configuration
protocol, and in the requests that are used to inspect, change or protocol, and in the requests that are used to inspect, change or
delete the policy resource. Note that in some protocols (such as delete the policy resource. Note that in some protocols (such as
DHCP), these protections may arise from limiting the use of the DHCP), these protections may arise from limiting the use of the
protocol to the local network, thus relying on lower-layer protocol to the local network, thus relying on lower-layer
security mechanisms. When neither application-layer or network- security mechanisms. When neither application-layer or network-
layer security is provided, location servers MUST reject requests layer security is provided, location servers MUST reject requests
using the PUT and DELETE methods. using the PUT and DELETE methods.
o The Location Server MUST ensure that the URI cannot be easily o The Location Server MUST ensure that it is not practical for an
predicted. The policy URI MUST NOT be derived solely from attacker to guess a policy URI value, even if the attacker has
information that might be public, including the Target identity or requested many policy URIs from the Location Server over time.
any location URI. The addition of 32 bits or more of random The policy URI MUST NOT be derived solely from information that
entropy is RECOMMENDED to make it infeasible for a third party to might be public, including the Target identity or any location
guess a policy URI. URI. The addition of 128 bits or more of random entropy is
RECOMMENDED to make it infeasible for a third party to guess a
policy URI.
o Servers SHOULD apply rate limits in order to make brute-force o Servers SHOULD apply rate limits in order to make brute-force
guessing infeasible. If a server allocates policy URIs that guessing infeasible. If a server allocates location URIs that
include N bits of entropy with a default lifetime of T seconds, include N bits of entropy with a lifetime of T seconds, then the
then the server should limit clients to 2^(N/2)/T queries per server should limit clients to (2^(N/2))/T queries per second.
second. (The lifetime T of a location URI set is specified by the
"expires" attribute in HELD.)
One possible algorithm for generating appropriately unpredictable
policy URIs for a location URI set is described in Appendix A.
The goal of the above recommendation on rate limiting is to bound the
probability that an attacker can guess a policy URI during its
lifetime. If an attacker is limited to (2^(N/2))/T queries per
second, then he will be able to make at most 2^(N/2) guesses over the
lifetime of the URI. Assuming these guesses are distinct, the
probability of the attacker guessing any given URI is
(2^(N/2))/(2^N), so the probability of compromise over the T-second
lifetime of the URI is at most 2^(-N/2). (Of course, if the attacker
guesses the URI after the policy URI has expired, then there is no
risk.) With N=128, the probability of compromise is 5.4e-20 under
this rate-limiting scheme. Operators should choose values for N so
that the corresponding risk of compromise presents an acceptable
level of risk.
If M distinct URIs are issued within the same namespace, then the
probability of any of the M URIs being compromised is M*2^(N/2). The
example algorithm for generating policy URIs (see Appendix A) places
them in independent namespaces (i.e., below the corresponding
location URIs), so this compounding does not occur.
Note that the chosen entropy level will also affect how quickly
legitimate clients can query a given URI, especially for very long-
lived URIs. If the default lifetime T is greater than 2^(N/2), then
clients will have to wait multiple seconds between queries.
Operators should choose entropy and lifetime values that result in
acceptable high maximum query rates and acceptably low probability of
compromise. For example, with 32 bits of entropy (much less than
recommended above), the one-query-per-second policy URI lifetime is
around 18 hours.
7.3. Location URI Allocation 7.3. Location URI Allocation
A policy URI enables the authorization by access control lists model A policy URI enables the authorization by access control lists model
[RFC5808] for associated location URIs. Under this model, it might [RFC5808] for associated location URIs. Under this model, it might
be possible to more widely distribute a location URI, relying on the be possible to more widely distribute a location URI, relying on the
authorization policy to constrain access to location information. authorization policy to constrain access to location information.
To allow for wider distribution, authorization by access control To allow for wider distribution, authorization by access control
lists places additional constraints on the construction of location lists places additional constraints on the construction of location
skipping to change at page 15, line 19 skipping to change at page 15, line 39
the same location URI or the same policy URI. the same location URI or the same policy URI.
In some deployments, it is not always apparent to a LCP server that In some deployments, it is not always apparent to a LCP server that
two clients are different. In particular, where a middlebox two clients are different. In particular, where a middlebox
[RFC3234] exists two or more clients might appear as a single client. [RFC3234] exists two or more clients might appear as a single client.
An example of a deployment scenario of this nature is described in An example of a deployment scenario of this nature is described in
[RFC5687]. An LCP server MUST create a different location URI and [RFC5687]. An LCP server MUST create a different location URI and
policy URI for every request, unless the requests can be reliably policy URI for every request, unless the requests can be reliably
identified as being from the same client. identified as being from the same client.
7.4. Policy URI Handling
Although servers may choose to implement access controls on policy
URIs, by default, any holder of a policy URI is authorized to access
and modify the referenced policy document, and thus, to control
access to the associated location resources. Because policy URIs
function as shared secrets, clients SHOULD protect them as they would
passwords. For example, policy URIs SHOULD NOT be transmitted to
other hosts or stored in plaintext.
It should be noted that one of the benefits of the policy URI
construct is that in most cases, there is not a policy URI to leave
the client device to which it is provided. Without policy URIs,
location URIs are subject to the "authorization by possession model",
and location URIs must be conveyed to another entity in order to be
useful. With policy URIs, location URIs can have more nuanced access
controls, and the shared secret used to authenticate the client
(i.e., the policy URI) can simply be stored on the client and used to
set the access control policy on the location URI. So while policy
URIs do use a default model of authorization by possession, they
reduce the overall risk to location privacy posed by leakage of
shared secret URIs.
8. Acknowledgements 8. Acknowledgements
Thanks to Mary Barnes and Alissa Cooper for providing critical Thanks to Mary Barnes and Alissa Cooper for providing critical
commentary and input on the ideas described in this document, and to commentary and input on the ideas described in this document, and to
Ted Hardie and Adam Roach for helping clarify the relationships Ted Hardie and Adam Roach for helping clarify the relationships
between policy URIs, policy documents, and location resources. between policy URIs, policy documents, and location resources.
Thanks to Stephen Farrell for a helpful discussion on security and
privacy challenges.
9. References 9. References
9.1. Normative References 9.1. Normative References
[I-D.ietf-geopriv-dhcp-lbyr-uri-option]
Polk, J., "Dynamic Host Configuration Protocol (DHCP) IPv4
and IPv6 Option for a Location Uniform Resource Identifier
(URI)", draft-ietf-geopriv-dhcp-lbyr-uri-option-12 (work
in progress), October 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., [RFC2616] Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. 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.
[RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [RFC2818] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
January 2004. January 2004.
[RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J., [RFC4745] Schulzrinne, H., Tschofenig, H., Morris, J., Cuellar, J.,
Polk, J., and J. Rosenberg, "Common Policy: A Document Polk, J., and J. Rosenberg, "Common Policy: A Document
Format for Expressing Privacy Preferences", RFC 4745, Format for Expressing Privacy Preferences", RFC 4745,
February 2007. February 2007.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008. (TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5985] Barnes, M., "HTTP-Enabled Location Delivery (HELD)", [RFC5985] Barnes, M., "HTTP-Enabled Location Delivery (HELD)",
RFC 5985, September 2010. RFC 5985, September 2010.
9.2. Informative References 9.2. Informative References
[I-D.ietf-geopriv-deref-protocol] [I-D.ietf-geopriv-deref-protocol]
Winterbottom, J., Tschofenig, H., Schulzrinne, H., Winterbottom, J., Tschofenig, H., Schulzrinne, H., and M.
Thomson, M., and M. Dawson, "A Location Dereferencing Thomson, "A Location Dereferencing Protocol Using HELD",
Protocol Using HELD", draft-ietf-geopriv-deref-protocol-04 draft-ietf-geopriv-deref-protocol-07 (work in progress),
(work in progress), October 2011. July 2012.
[I-D.ietf-geopriv-policy] [I-D.ietf-geopriv-policy]
Schulzrinne, H., Tschofenig, H., Cuellar, J., Polk, J., Schulzrinne, H., Tschofenig, H., Cuellar, J., Polk, J.,
Morris, J., and M. Thomson, "Geolocation Policy: A Morris, J., and M. Thomson, "Geolocation Policy: A
Document Format for Expressing Privacy Preferences for Document Format for Expressing Privacy Preferences for
Location Information", draft-ietf-geopriv-policy-25 (work Location Information", draft-ietf-geopriv-policy-27 (work
in progress), October 2011. in progress), August 2012.
[RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and [RFC3234] Carpenter, B. and S. Brim, "Middleboxes: Taxonomy and
Issues", RFC 3234, February 2002. Issues", RFC 3234, February 2002.
[RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and
J. Polk, "Geopriv Requirements", RFC 3693, February 2004. J. Polk, "Geopriv Requirements", RFC 3693, February 2004.
[RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object [RFC4119] Peterson, J., "A Presence-based GEOPRIV Location Object
Format", RFC 4119, December 2005. Format", RFC 4119, December 2005.
[RFC4648] Josefsson, S., "The Base16, Base32, and Base64 Data
Encodings", RFC 4648, October 2006.
[RFC4825] Rosenberg, J., "The Extensible Markup Language (XML) [RFC4825] Rosenberg, J., "The Extensible Markup Language (XML)
Configuration Access Protocol (XCAP)", RFC 4825, May 2007. Configuration Access Protocol (XCAP)", RFC 4825, May 2007.
[RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed [RFC4918] Dusseault, L., "HTTP Extensions for Web Distributed
Authoring and Versioning (WebDAV)", RFC 4918, June 2007. Authoring and Versioning (WebDAV)", RFC 4918, June 2007.
[RFC5606] Peterson, J., Hardie, T., and J. Morris, "Implications of [RFC5606] Peterson, J., Hardie, T., and J. Morris, "Implications of
'retransmission-allowed' for SIP Location Conveyance", 'retransmission-allowed' for SIP Location Conveyance",
RFC 5606, August 2009. RFC 5606, August 2009.
skipping to change at page 17, line 13 skipping to change at page 18, line 13
Mechanism", RFC 5808, May 2010. Mechanism", RFC 5808, May 2010.
[RFC6155] Winterbottom, J., Thomson, M., Tschofenig, H., and R. [RFC6155] Winterbottom, J., Thomson, M., Tschofenig, H., and R.
Barnes, "Use of Device Identity in HTTP-Enabled Location Barnes, "Use of Device Identity in HTTP-Enabled Location
Delivery (HELD)", RFC 6155, March 2011. Delivery (HELD)", RFC 6155, March 2011.
[RFC6225] Polk, J., Linsner, M., Thomson, M., and B. Aboba, "Dynamic [RFC6225] Polk, J., Linsner, M., Thomson, M., and B. Aboba, "Dynamic
Host Configuration Protocol Options for Coordinate-Based Host Configuration Protocol Options for Coordinate-Based
Location Configuration Information", RFC 6225, July 2011. Location Configuration Information", RFC 6225, July 2011.
Appendix A. Example Policy URI Generation Algorithm
One possible algorithm for generating appropriately unpredictable
policy URIs for a location URI set is as follows:
1. Choose parameters:
* A cryptographic hash function H, e.g., SHA256
* A number N of bits of entropy to add, such that N is no more
than the length of the output of the hash function
2. On allocation of a location URI, generate a policy URI in the
following way:
1. Generate a random value NONCE at least N/8 bytes long
2. Compute hash = H( Location-URI-Set || NONCE ) using some
cryptographic hash function H and some serialization of the
location URI set (e.g., the XML from a HELD response)
3. Form the policy URI by appending the base64url-encoded form
of the hash [RFC4648] to one of the location URIs, e.g., as a
query parameter: "http://example.com/loc/
foo?policy=j3WTGUb3smxcZA6eKIqmqdV3ALE"
Authors' Addresses Authors' Addresses
Richard Barnes Richard Barnes
BBN Technologies BBN Technologies
9861 Broken Land Parkway 9861 Broken Land Parkway
Columbia, MD 21046 Columbia, MD 21046
US US
Phone: +1 410 290 6169 Phone: +1 410 290 6169
Email: rbarnes@bbn.com Email: rbarnes@bbn.com
skipping to change at page 17, line 23 skipping to change at page 19, line 4
Authors' Addresses Authors' Addresses
Richard Barnes Richard Barnes
BBN Technologies BBN Technologies
9861 Broken Land Parkway 9861 Broken Land Parkway
Columbia, MD 21046 Columbia, MD 21046
US US
Phone: +1 410 290 6169 Phone: +1 410 290 6169
Email: rbarnes@bbn.com Email: rbarnes@bbn.com
Martin Thomson Martin Thomson
Andrew Corporation Microsoft
Andrew Building (39) 3210 Porter Drive
Wollongong University Campus Palo Alto, CA 94304
Northfields Avenue US
Wollongong, NSW 2522
AU
Phone: +61 2 4221 2915 Phone: +1 650-353-1925
Email: martin.thomson@andrew.com Email: martin.thomson@outlook.com
James Winterbottom James Winterbottom
Andrew Corporation Andrew Corporation
Andrew Building (39) Andrew Building (39)
Wollongong University Campus Wollongong University Campus
Northfields Avenue Northfields Avenue
Wollongong, NSW 2522 Wollongong, NSW 2522
AU AU
Phone: +61 242 212938 Phone: +61 242 212938
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