Network Working Group A. Barbir
Internet-Draft Nortel Networks
Expires: March 4, 2003 H. Orman
Purple Streak Development
A. Terzis
Individual Consultant
O. Batuner
attbi
B. Srinivas
T. Chan
Nokia
September 3, 2002
Requirements for Policy, Authorization and Enforcement of OPES
Services
draft-ietf-opes-authorization-00
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on March 4, 2003.
Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This document describes policy, authorization and enforcement
requirements for the selection of the services to be applied to a
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given OPES flow.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Policy Architecture . . . . . . . . . . . . . . . . . . . . 4
2.1 Policy Components and Functions . . . . . . . . . . . . . . 4
2.2 Requirements For Policy Decision Point . . . . . . . . . . . 6
2.3 Requirements for Policy Enforcement Points . . . . . . . . . 6
3. Requirements for Interfaces . . . . . . . . . . . . . . . . 8
3.1 Service Bindings Requirements . . . . . . . . . . . . . . . 8
3.1.1 Environment Variables . . . . . . . . . . . . . . . . . . . 8
3.1.2 Requirements for Using State Information . . . . . . . . . . 9
3.1.3 Requirements for Passing Information Between Services . . . 9
3.2 Requirements for Rule and Rules Management . . . . . . . . . 9
3.2.1 Requirements for Rule Providers . . . . . . . . . . . . . . 9
3.2.2 Requirements for Rule Formats and Protocols . . . . . . . . 10
3.2.3 Requirements for Rule Conditions . . . . . . . . . . . . . . 10
3.2.4 Requirements for Rule Actions . . . . . . . . . . . . . . . 10
4. Authentication of Principals and Authorization of
Services . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1 End users, Publishers and Other Considerations . . . . . . . 12
4.1.1 Considerations for end users . . . . . . . . . . . . . . . . 12
4.1.2 Considerations for publishing sites . . . . . . . . . . . . 13
4.1.3 Other considerations . . . . . . . . . . . . . . . . . . . . 13
4.2 Authentication . . . . . . . . . . . . . . . . . . . . . . . 13
4.3 Authorization . . . . . . . . . . . . . . . . . . . . . . . 14
4.4 Integrity and Encryption . . . . . . . . . . . . . . . . . . 15
4.4.1 Integrity and confidentiality of authentication and
requests/responses for service . . . . . . . . . . . . . . . 15
4.4.2 Integrity and confidentiality of application content . . . . 15
4.5 Privacy . . . . . . . . . . . . . . . . . . . . . . . . . . 16
References . . . . . . . . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 17
A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 19
Full Copyright Statement . . . . . . . . . . . . . . . . . . 20
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1. Introduction
The Open Pluggable Edge Services (OPES) [1] architecture enables
cooperative application services (OPES services) between a data
provider, a data consumer, and zero or more OPES processors. The
application services under consideration analyze and possibly
transform application-level messages exchanged between the data
provider and the data consumer. The OPES processor can distribute
the responsibility of service execution by communicating and
collaborating with one or more remote callout servers.
The execution of such services is governed by a set of rules
installed on OPES processor. The rule enforcement can trigger the
execution of service applications local to the OPES processor or on a
remote callout server.
Policies express the goals of an OPES processor as a set of rules
used to administer, manage and control access to resources. The
requirements in this document govern the behavior of OPES entities in
determining which, if any, of available services are to be applied to
a given message.
The scope of OPES policies described in this document are limited to
those that describe which services to call and, if appropriate, with
what parameters. These policies do not include those that prescribe
the behavior of the called services. It is desirable to enable a
common management framework for specifying policies for both the
calling of and the behavior of a service. The integration of such
function is the domain of policy administration user interaction
applications.
The document is organized as follows:Section 2 considers policy
framework. Section 3 discusses requirements for interfaces, while
section 4 examines authentication of principals and authorization of
services.
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2. Policy Architecture
This section describes the architectural policy decomposition
requirements. It also describes the requirements for the interfaces
between the policy components.
2.1 Policy Components and Functions
The policy functions are decomposed into three components: a Rule
Author, a Policy Decision Point (PDP) and Policy Enforcement Point
(PEP). The Rule Author provides the rules to be used by an OPES
entity. These rules control the invocation of services on behalf of
the rule author. The PDP and the PEP interpret the collected rules
and appropriately enforce them. The decomposition is illustrated in
Figure 1.
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---------------------------------------------------------------------
+--------+ +--------+
| Rule | | Rule |
| Author | ... | Author |
+--------+ +--------+
| |
| |
| +----------+ |
| | Policy | | <- PDP Interface
+--------->| Decision |<----------+
| Point |
+----------+
| ^
| |
| | <- PEP Interface
| |
V |
+--------------+ ...
---> | Policy | --->
| Enforcement | Data Traffic
<--- | Point | <---
+--------------+
Figure 1: Policy Components
---------------------------------------------------------------------
The decomposition of policy control into a PDP and a PEP permit the
offloading of some tasks to an administrative service that may be
located on a separate server from the real-time enforcement services
of the PEP that reside on the OPES processor.
The PDP provides for the authentication and authorization of rule
authors and the validation and compilation of rules.
The PEP resides in the data filter where the data from an OPES flow
is evaluated against the compiled rules and appropriate calls to the
requested services are performed.
Interfaces between these architectural components are points of
interoperability. The interface between rule authors and the policy
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decision points (PDP Interface) must use the standard format that may
result from the requirements as described in this document.
The interface between the policy decision points and the policy
enforcement points (PEP Interface) can be internal to a specific
vendor implementation of an OPES processor. Implementations must use
standard interface only if the PDP and the PEP reside on different
OPES processor.
2.2 Requirements For Policy Decision Point
The Policy Decision Point is essentially a policy compiler. The PDP
must be a service that provides administrative support to the
enforcement points. The PDP service must authenticate the rule
authors.
The PDP must verify that the specified rules are within the scope of
the rule authors authority. The PDP must be a component of the OPES
Administration Authority.
2.3 Requirements for Policy Enforcement Points
In the OPES architecture, the data filter represents a Policy
Enforcement point (PEP). At this point, data from an OPES flow is
evaluated against the compiled rules and appropriate calls to the
requested services are performed.
In the PEP rules may chain actions together, where, a series of
services to be called are specified. Implementation must ensure the
passing of information from one called service to another.
Implementation must not prohibit the re-evaluation of a message to
determine if another service or set of services should be called.
The execution of an action (i.e., the triggering of a rule) may lead
to the modification of a message property values. For example, an
OPES service that under some circumstances converts JPEG images to
GIF images modifies the content type of the requested web object.
Such modification of message property values may change the behavior
of subsequently performed OPES actions. The data filter should act
on matched rules before it evaluates subsequent rules. Multiple
matched rules can be triggered simultaneously if the data filter can
determine in advance that there are no side effects from the
execution of any specific rule.
A data filter may evaluate messages several times in the course of
handling an OPES flow. The rule processing points may be defined by
administratively defined names. The definition of such names can
serve as a selector for policy rules to determine the applicability
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of a rule or a set of rules at each processing point. The scope of
policy control of policy roles as defined RFC 3060 should be used
where it aids in the development of the OPES policy model.
In Figure 2 a typical message data flow between a data consumer
application, an OPES processor and a data provider application.
There are four commonly used processing points identified by the
numbers 1 through 4.
---------------------------------------------------------------------
+--------+ +-----------+ +---------+
| |<------|4 3|<------| |
| Data | | OPES | | Data |
|Consumer| | Processor | |Provider |
| Appl. |------>|1 2|------>| Appl. |
+--------+ +-----------+ +---------+
Figure 2: Processing Execution Points
---------------------------------------------------------------------
Any data filter (PEP) or any administrative (PDP) implementation must
support the four rule processing points.
o Data Consumer Request Handling Role : This involves request
processing when received from a Data Consumer Application.
o OPES Processor Request handling role: This involves request
processing before forwarding to Data Provider Application.
o Data Provider Response handling role: This involves response
processing when forwarding to Data Consumer Application.
o OPES Processor Response handling role:This involves response
processing when forwarding to Data Consumer Application.
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3. Requirements for Interfaces
The interface between the policy system and OPES services needs to
include the ability to pass system state information as well as the
subject message.
3.1 Service Bindings Requirements
The invoked OPES services must be able to be specified in a location
independent fashion. That is, the rule authors need not know and
need not specify the instance of an OPES service in the rules.
The rule author should be able to identify the required service at
the detail level that is appropriate for his or her needs. The rule
author should be able to specify a type of service or be able to
specify any service that fits a general category of service to be
applied its traffic.
The binding of OPES service names to specific service may be
distributed between the PDP and the PEP. As rules are compiled and
validated by the PDP, they must be resolved to a specific
installations' set of homogeneous OPES service.
The selection of a specific instance may be postponed and left to PEP
to select at either rule installation time or at run time. To
achieve interoperability, PEP must support resolving a generic name
to a specific instance. It is possible to use services such as SLP
or UDDI to resolve generic service names to specific OPES service
instances.
The policy system may support dynamic discovery of service bindings.
The rule author may, not know specific service bindings such as
protocol and parameters, when a rule (as specified on the PDP
Interface) is general in nature. The required binding information
must be provided by the PDP and conveyed on the PEP Interface. A
service description methodology such as WSDL must be present in the
policy system. It is to be determined whether an OPES standard is
required.
3.1.1 Environment Variables
There may be a need to define and support means for maintaining state
information that can be used in both condition evaluation and action
execution. Depending on the execution environment, OPES services may
have the freedom to define variables that are needed and use these
variables to further define their service behavior without the data
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filter support.
3.1.2 Requirements for Using State Information
Policy rules may specify that state information be used as part of
the evaluation of the rules against a given message in an OPES flow.
Thus, the policy system should support the maintenance of groups that
can be used in evaluating rule conditions. Membership in such groups
can be used as action triggers.
For example, an authorized site blocking service might conclude that
a particular user shouldn't be permitted access to a certain web
site. Rather than calling the service for each request sent by such
a user, a rule might be created that determine if user is a member of
blocked users and requested site is a member of blocked-sites then
invoke a local blocking service to return and return an appropriate
message to the user.
3.1.3 Requirements for Passing Information Between Services
Environment variables can be used to pass state information between.
For example, analysis of the request or modifications to the request
may need to be captured as state information that can be passed to
other services on the request path or to services on the response(s)
associated with that request.
In the PEP, there should be provisions to enable setting up variables
when returning from a service call and passing variables to other
called services based on policy.
3.2 Requirements for Rule and Rules Management
This section provides the requirements for rule management. The
rules are divided into two groups. Some rules are provided by the
data consumer application and other rules are provided by the data
provider application.
3.2.1 Requirements for Rule Providers
The requirements for rule providers are:
o Rule providers must be authenticated and authorized for rules that
apply to their network role.
o Rule providers must not be able to specify rules that are not
within their scope of authority.
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o Rule providers should be able to only what is needed for their
services.
o Compilation of rules from different sources must not lead to
execution of conflicting rules.
o The resolution of such rule conflicts is out of scope
o Rules are assumed to be static and applied to current network
state.
3.2.2 Requirements for Rule Formats and Protocols
It is desirable to choose standard technologies like XML to specify
the rule language format.
Rules need to be sent form the rule authors to the OPES
administrative server for service authorization, rule validation and
compilation. The mechanisms for doing that are out of scope of the
current work.
Once the rules are authorized, validated and compiled by the
administrative server, the rules need to be sent to the OPES
processor. The mechanisms for doing that are out of scope of the
current work.
3.2.3 Requirements for Rule Conditions
Rule conditions must be matched against attribute values of the
encapsulated protocol as well as environment variable values.
Attribute values of the encapsulated protocol include protocol header
values and possibly also protocol body values.
Some OPES services may need to be invoked for all users requests or
server responses, services with logging functionality, as an example.
The rule system should allow unconditional rules rather than
requiring rule authors to specify rule conditions that are always
true.
3.2.4 Requirements for Rule Actions
The rule system must allow for the specification of rule actions that
are triggered if the conditions of a rule are met. Matched rules
typically lead to the invocation of local or remote services. Rule
actions must identify the OPES service that is to be executed for the
current message request or response.
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Rule actions may contain run-time parameters which can be used to
control the behavior of an OPES service. If specified, these
parameters must be passed to the executed OPES service.
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4. Authentication of Principals and Authorization of Services
This section considers the authorization and authentication of OPES
services.
4.1 End users, Publishers and Other Considerations
4.1.1 Considerations for end users
An OPES rule determines which attributes of traffic will trigger the
application of an OPES services. The author of the service can
supply rules, but the author cannot supply the necessary part of the
rule precondition that determines which network users will have the
OPES services applied for them. This section discusses how users are
identified in the rule preconditions, and how users can select and
deselect OPES services for their traffic, how an OPES service
provider should identify the users, and how they determine whether or
not to add their service selection to an OPES enforcement point.
An OPES service provider must satisfy these major requirements:
o Allow all users to request addition, deletion, or blocking of OPES
services for their traffic (blocking means "do not use this
service for my traffic").
o Prevent untrusted users from causing OPES services to interfere
with the traffic of other users.
o Allow users to see their OPES service profiles and notify them of
changes.
o Keep a log of all profile activity for audit purposes.
o Adhere to a privacy policy guarding users' profiles.
The administrator of the PDP is a trusted party and can set policy
for individuals or groups using out-of-band communication and
configuration files. However, users must always be able to query the
PDP in order to learn what rules apply to their traffic.
Rules can be deposited in the PDP with no precondition relating to
network users. This is the way rules are packaged with an OPES
service when it is delivered for installation. The PDP is
responsible for binding identities to the rules and transmitting them
to the PEP. The identity used by the PDP for policy decisions must
be strictly mapped to the identity used by the PEP. Thus, if a user
goes through and identification and authentication procedure with the
PDP and is known by identity "A", and if the PEP uses IP addresses
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for identities, then the PDP must provide the PEP with a binding
between "A" and A's current IP address.
4.1.2 Considerations for publishing sites
An OPES service provider acting on behalf of different publishing
sites should keep all the above considerations in mind when
implementing an OPES site. Because each publishing site may be
represented by only a single identity, the authentication and
authorization databases may be easier for the PEP to handle.
4.1.3 Other considerations
Authentication may be necessary between PDP's and PEP's, PEP's and
callout servers, PEP's and other PEP's, callout servers and other
callout servers, for purposes of validating privacy policies. In any
case where user data or traffic crosses trust domain boundaries, the
originating trust domain should have a policy describing which other
domains are trusted, and it should authenticate the domains and their
policies before forwarding information.
4.2 Authentication
When an individual selects (or deselects) an OPES service, the
individual must be authenticated by the OPES service provider. This
means that a binding between the user's communication channel and an
identity known to the service provider is made in a secure manner.
This SHOULD be done using a strong authentication method with a
public key certificate for the user; this will be helpful in
resolving later disputes. The service provider MUST keep a log of
all requests for OPES services. The service provider SHOULD use
public key certficates to authenticate responses to requests.
The service provider may have trusted users who through explicit or
implicit contract can assign, remove, or block OPES services for
particular users. The trusted users must be authenticated before
being allowed to take actions which will modify the policy base, and
thus, the actions of the PEP's.
The PEP's should be authenticated before they receive policy rules
that reflect the profiles of users. The PEP's must adhere to the
privacy preferences of the users.
When an OPES service provider accepts an OPES service, there must be
a unique name for the service provided by the entity publishing the
service. Users may refer to the unique name when requesting a
service. The unique name must be when notifying users about their
service profiles. PEP's must be aware of the unique name for each
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service that can be accessed from their domain. There MUST be a
cryptographic binding between the unique name and the entity
responsible for the functional behavior of the service; i.e., if it
is a human language translating service then the name of company that
wrote the software should be bound to the unique name.
4.3 Authorization
In addition to requesting or terminating specific services, users may
block particular services, indicating that the services should not be
applied to their traffic. The "block all OPES" directive must be
supported on a per user basis.
A response to a request for an OPES service can be positive or
negative. Reasons for a negative response include "service unknown"
or "service denied by PDP policy". Positive responses should include
the identity of the requestor and the service and the type of
request.
As described in the OPES Architecture [1], requests for OPES services
originate in either the enduser or the publisher domain. The PDP
bases its authorization decision on the requestor and the domain.
There are some cases where the decision may be complicated.
o The end user has blocked a service, but a trusted user of the PDP
wants it applied anyway. In this case, the end user SHOULD
prevail, unless their are security or legal reasons to leave it in
place.
o The publisher and the enduser are in the same domain. If the
publisher and enduser are both clients of a PDP, can they make
requests that effect each other's processing? In this case, the
PDP must have policy rules naming the identities that are allowed
to set such rules.
o The publisher requests a service for an enduser. In this case, in
which the PDP and PEP are in the publisher's administrative
domain, the publisher has some way of identifying the end user and
his traffic, and the PDP must enable the PEP to enforce the
policy. This is allowed, but the PDP MUST use strong methods to
identify the user and his traffic. The user must be able to
request and receive information about the service profile that a
publisher site keeps about him.
o The enduser requests a service specific to a publisher identity
(e.g., nfl.com), but the publisher prohibits the service (e.g.,
through a "NO OPES" application header). As in the case above,
the publisher must be able to request and receive profile
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information that a user keeps about a publisher.
In general, the PDP should keep its policy base in a manner that
makes the decision procedure for all cases easy to understand.
4.4 Integrity and Encryption
4.4.1 Integrity and confidentiality of authentication and requests/
responses for service
The requests and responses should be cryptographically tied to the
identities of the requestor and responder, and the messages should
not alterable without detection. A certificate-based digital
signature is strongly recommended as part of the authentication
process. A binding between the request and response should be
established using well-founded cryptographic means, to show that the
response is made in reply to a specific request.
4.4.2 Integrity and confidentiality of application content
As directed by the PEP, content will be transformed in whole or in
part by OPES services. This means that end-to-end cryptographic
protections cannot be used. This is probably acceptable for the vast
majority of traffic, but in cases where a lesser form of content
protection is desirable, hop-by-hop protections can be used instead.
The requirements for such protections are:
o Integrity using shared secrets MUST be used between all processing
points, end-to-end (i.e., the two ends a "hop" must share a
secret, but the secret can be different between "hops"). The
processing points include the callout servers.
o Encryption can be requested separately, with the same secret
sharing requirement between "hops". When requested, encryption
applies to all processing points, including callout servers.
o The signal for integrity (and optionally encryption) must
originate from either the requestor (in which case it is applied
to the response as well) or the responder (in which case it covers
only the response).
o The shared secrets must be unique for each requestor/responder
pair.
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4.5 Privacy
The PDP must have a privacy policy regarding OPES data such as user
profiles for services. User must be able to limit the promulgation
of their profile data and their identities.
Supported limitations MUST include:
o Identity may not be given to callout servers.
o Profile information may not be shared.
o Traffic data may not be sent to callout servers run by third
parties.
o Traffic from particular sites should not be given to OPES callout
servers.
When an OPES service is provided by a third-party, it must have a
privacy policy and identify itself to upstream and downstream
parties, telling them how to access its privacy policy.
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References
[1] A. Barbir et. al, "An Architecture for Open Pluggable Edge
Services (OPES)", Internet-Draft: http://www.ietf.org/internet-
drafts/draft-ietf-opes-architecture-03.txt, June 2002.
[2] Floyd, S. and L. Daigle, "IAB Architectural and Policy
Considerations for Open Pluggable Edge Services", RFC 3238,
January 2002.
[3] Westerinen, A., Schnizlein, J., Strassner, J., Scherling, M.,
Quinn, B., Herzog, S., Huynh, A., Carlson, M., Perry, J. and S.
Waldbusser, "Terminology for Policy-Based Management", RFC 3198,
November 2001.
[4] Fielding, R., Gettys, J., Mogul, J., Nielsen, H., Masinter, L.,
Leach, P. and T. Berners-Lee, "Hypertext Transfer Protocol --
HTTP/1.1", RFC 2616, June 1999.
Authors' Addresses
Abbie Barbir
Nortel Networks
3500 Carling Avenue
Nepean, Ontario K2H 8E9
Canada
Phone: +1 613 763 5229
EMail: abbieb@nortelnetworks.com
Hilarie Orman
Purple Streak Development
Phone:
EMail: ho@alum.mit.edu
Andreas Terzis
Individual Consultant
150 Golf Course Dr.
Rohnert Park, CA 94928
USA
EMail: aterzis@sbcglobal.net
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Oskar Batuner
attbi
EMail: batuner@attbi.com
Bindignavile Srinivas
Nokia
5 Wayside Road
Burlington, MA 01803
USA
EMail: bindignavile.srinivas@nokia.com
Tat Chan
Nokia
5 Wayside Road
Burlington, MA 01803
USA
EMail: Tat.Chan@nokia.com
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Appendix A. Acknowledgements
TBD
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Full Copyright Statement
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