Email Policy Service Trust Processing
draft-schaad-plasma-service-01
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
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|---|---|---|---|
| Author | Jim Schaad | ||
| Last updated | 2012-03-12 | ||
| Replaces | draft-schaad-eps-trust | ||
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| Additional resources | |||
| Stream | Stream state | (No stream defined) | |
| Consensus boilerplate | Unknown | ||
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draft-schaad-plasma-service-01
Network Working Group J. Schaad
Internet-Draft Soaring Hawk Consulting
Intended status: Standards Track March 12, 2012
Expires: September 13, 2012
Email Policy Service Trust Processing
draft-schaad-plasma-service-01
Abstract
Write Me
Status of this Memo
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This Internet-Draft will expire on September 13, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. XML Nomenclature and Name Spaces . . . . . . . . . . . . . 4
1.2. Requirements Terminology . . . . . . . . . . . . . . . . . 5
2. Components . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. WS-Trust 1.3 . . . . . . . . . . . . . . . . . . . . . . . 6
2.2. XACML 3.0 . . . . . . . . . . . . . . . . . . . . . . . . 6
2.3. SAML . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3. Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Sender Processing . . . . . . . . . . . . . . . . . . . . 7
3.2. Recieving Agent Processing . . . . . . . . . . . . . . . . 8
4. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 10
5. Plasma Request . . . . . . . . . . . . . . . . . . . . . . . . 11
5.1. Authentication Element . . . . . . . . . . . . . . . . . . 12
5.2. xacml:Request Element . . . . . . . . . . . . . . . . . . 13
6. Plasma Response Element . . . . . . . . . . . . . . . . . . . 14
6.1. xacml:Response Element . . . . . . . . . . . . . . . . . . 15
7. Authentication Element . . . . . . . . . . . . . . . . . . . . 17
7.1. SAML Collection Element . . . . . . . . . . . . . . . . . 18
7.2. WS Trust Tokens . . . . . . . . . . . . . . . . . . . . . 19
7.3. XML Signature Element . . . . . . . . . . . . . . . . . . 20
7.4. GSS-API Element . . . . . . . . . . . . . . . . . . . . . 22
8. Role Token and Policy Acquisition . . . . . . . . . . . . . . 23
8.1. Role Token Request . . . . . . . . . . . . . . . . . . . . 23
8.2. Request Role Token Response . . . . . . . . . . . . . . . 25
8.2.1. PlasmaTokens XML element . . . . . . . . . . . . . . . 26
9. Sending A Message . . . . . . . . . . . . . . . . . . . . . . 29
9.1. Send Message Request . . . . . . . . . . . . . . . . . . . 29
9.1.1. CMS Message Token Data Structure . . . . . . . . . . . 30
9.2. Send Message Response . . . . . . . . . . . . . . . . . . 32
10. Decoding A Message . . . . . . . . . . . . . . . . . . . . . . 33
10.1. Requesting Message Key . . . . . . . . . . . . . . . . . . 33
10.2. Requesting Message Key Response . . . . . . . . . . . . . 34
11. Plasma Attributes . . . . . . . . . . . . . . . . . . . . . . 36
11.1. Data Attributes . . . . . . . . . . . . . . . . . . . . . 36
11.1.1. Channel Binding Data Attribute . . . . . . . . . . . . 36
11.1.2. CMS Signer Info Data Attribute . . . . . . . . . . . . 37
11.1.3. S/MIME Capabilities Data Attribute . . . . . . . . . . 37
11.2. Obligations and Advice . . . . . . . . . . . . . . . . . . 38
11.2.1. Signature Required . . . . . . . . . . . . . . . . . . 38
11.2.2. Encryption Required . . . . . . . . . . . . . . . . . 38
12. Security Considerations . . . . . . . . . . . . . . . . . . . 40
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 41
14. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 43
15. References . . . . . . . . . . . . . . . . . . . . . . . . . . 44
15.1. Normative References . . . . . . . . . . . . . . . . . . . 44
15.2. Informative References . . . . . . . . . . . . . . . . . . 45
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Editorial Comments . . . . . . . . . . . . . . . . . . . . . . . .
Appendix A. XML Schema . . . . . . . . . . . . . . . . . . . . . 47
Appendix B. Example: Get Roles Request . . . . . . . . . . . . . 52
Appendix C. Example: Get Roles Response . . . . . . . . . . . . . 53
Appendix D. Example: Get CMS Token Request . . . . . . . . . . . 54
Appendix E. Example: Get CMS Token Response . . . . . . . . . . . 56
Appendix F. Example: Get CMS Key Request . . . . . . . . . . . . 57
Appendix G. Example: Get CMS KeyResponse . . . . . . . . . . . . 58
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 59
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1. Introduction
1.1. XML Nomenclature and Name Spaces
The following name spaces are used in this document:
+-----+--------------------------------------------+----------------+
| Pre | Namespace | Specification( |
| fix | | s) |
+-----+--------------------------------------------+----------------+
| eps | http://ietf.org/2011/plasma/ | This |
| | | Specification |
| | | |
| wst | http://docs.oasis-open.org/ws-sx/ws-trust/ | [WS-TRUST] |
| | 200512 | |
| | | |
| wsu | http://docs.oasis-open.org/wss/2004/01/oas | [WS-Security] |
| | is-200401-wss-wssecurity-utility-1.0.xsd | |
| | | |
| wss | http://docs.oasis-open.org/wss/2004/01/oas | [WS-Security] |
| e | is-200401-wss-wssecurity-secext-1.0.xsd | |
| | | |
| wss | http://docs.oasis-open.org/wss/oasis-wss-w | [WS-Security] |
| e11 | security-secext-1.1.xsd | |
| | | |
| xac | http://docs.oasis-open.org/xacml/3.0/xacml | [XACML] |
| ml | -3.0-core-spec-cs-01-en.html | |
| | | |
| ds | http://www.w3.org/2000/09/xmldsig# | [XML-Signature |
| | | ] |
| | | |
| xen | http://www.w3.org/2001/04/xmlenc# | [XML-Encrypt] |
| c | | |
| | | |
| wsp | http://schemas.xmlsoap.org/ws/2004/09/poli | [WS-Policy] |
| | cy | |
| | | |
| wsa | http://www.w3.org/2005/08/addressing | [WS-Addressing |
| | | ] |
| | | |
| xs | http://www.w3.org/2001/XMLSchema | [XML-Schema1][ |
| | | XML-Schema2] |
+-----+--------------------------------------------+----------------+
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1.2. Requirements Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
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2. Components
2.1. WS-Trust 1.3
We use WS-Trust as the basis for the protocol presented in this
document. WS-Trust is a secure messaging protocol used for security
token exchange to enable the issuance and dissemination of
credentials within different trust domains. WS-Trust 1.3 is
specified by OASIS in [WS-TRUST]. WS-Trust is built on SOAP (see
[SOAP12]) to provide a messaging structure.
2.2. XACML 3.0
The XACML specification (eXtensible Access Control Markup Language)
[XACML] provides a framework for writing access control policies and
for creating standardized access control queries and responses. For
creating the query/response messages, the specification is written
assuming that there is a high degree of trust in both the PEP and the
PDP. If one looks at Figure 2 in [Plasma], this corresponds to the
(a) case in the diagram. For this specification we are assuming that
the PEP is not a trusted entity leading to some additional message
wrapping and requirements.
2.3. SAML
We use the SAML specification.
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3. Model
To be supplied from the problem statement document. [anchor8]
(1)(3) +----------+
+----------->|Sending |<------------+
| |Agent | |
(2) v +----------+ v
+----------+ ^ +---------+
|Email | | |Mail |
|Policy |<----------+ |Transfer |
|Service | |Agent |
+----------+ +---------+
() ^ +----------+ ^
| |Receiving | |
+----------->|Agent |<------------+
()() +----------+
Figure 1: Message Access Control Actors
List the boxes above and give some info about them.
Email Policy Service is the gateway controller for accessing a
message. Although it is represented as a single box in the
diagram, there is no reason for it to be in practice. Each of the
three protocols could be talking to different instances of a
common system. This would allow for a server to operated by
Company A, but be placed in Company B's network thus reducing the
traffic sent between the two networks.
Mail Transfer Agent is the entity or set of entities that is used to
move the message from the sender to the receiver. Although this
document describes the process in terms of mail, any method can be
used to transfer the message.
Receiving Agent is the entity that consumes the message.
Sending Agent is the entity that originates the message.
3.1. Sender Processing
We layout the general steps that need to be taken by the sender of an
EPS message. The numbers in the steps below refer to the numbers in
the upper half of Figure 1. A more detailed description of the
processing is found in Section 8 for obtaining the security policies
that can be applied to a messages and Section 9 for sending a
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message.
1. The Sending Agent sends a message to one or more Email Policy
Services in order to obtain the set of policies that it can apply
to a message along with a security token to be used in proving
the authorization. Details of the message send can be found in
Section 8.1.
2. The Email Policy Service examines the set of policies that it
understands and checks to see if the requester is authorized to
send messages with the policy.
3. The Email Policy Service returns the set of policies and an
security token to the Sending Agent. Details of the message sent
can be found in Section 8.2.
4. The Sending Agent selects the Email Policy(s) to be applied to
the message, along with the set of recipients for the message.
5. The Sending Agent relays the selected information to the Email
Policy Service along with the security token. Details of this
message can be found in Section 9.1.
6. The Email Policy Service creates the recipient info attribute as
defined in [EPS-CMS].
7. The Email Policy Service returns the created attribute to the
Sending Agent. Details of this message can be found in
Section 9.2.
8. The Sending Agent composes the CMS EnvelopedData content type
placing the returned attribute into a KEKRecipientInfo structure
and then send the message to the Mail Transport Agent.
3.2. Recieving Agent Processing
We layout the general steps that need to be taken by the sender of an
EPS message. The numbers in the steps below refer to the numbers in
the lower half of Figure 1. A more detailed description of the
processing is found in Section 10.
1. The Receiving Agent obtains the message from the Mail Transport
Agent.
2. The Receiving Agent starts to decode the message and in that
process locates an EvelopedData content type which has a
KEKRecipientInfo structure with a XXXX attribute.
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3. The Receiving Agent processes the SignedData content of the XXXX
attribute to determine that communicating with it falls within
accepted policy.
4. The Receiving Agent transmits the content of the XXXX attribute
to the referenced Email Policy Service. The details of this
message can be found in Section 10.1.
5. The Email Policy Service decrypts the content of the message and
applies the policy to the credentials provided by the Receiving
Agent.
6. If the policy passes, the Email Policy Service returns the
appropriate key or RecipientInfo structure to the Receiving
Agent. Details of this message can be found in Section 10.2.
7. The Receiving Agent proceeds to decrypt the message and perform
normal processing.
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4. Protocol Overview
The protocol defined in this document is designed to take place
between a Plasma server and a Plasma client. The protocol takes
place in terms of a query/repsonse dialog from the client to the
server. A completed dialog can consist of one or more query/response
message pairs as the protocol allows for multiple round trips within
a single dialog so that a client can provide additional
authentication, authorization and attribute information to the
server.
The protocol MUST be run over a secure transport, while the protocol
allows for signature operations to occur on sections of the message
structure, the secure transport is responsible for providing the
confidentiality and integrity protection services over the entire
message.
Multiple dialogs may be run over a single secure transport. Before a
new dialog may be started, the previous dialog MUST have completed to
a state of success, failure or not applicable. A new dialog MUST NOT
be started after receiving a response with an indeterminate status.
This is an indicator that the dialog has not yet completed.
Plasma compliant implementations MUST support TLS 1.1 [RFC4346] and
above as secure transports. Implementations SHOULD NOT allow for the
use of TLS 1.0 or SSL. Other secure transports MAY be implemented.
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5. Plasma Request
The specification is written using XACML as the basic structure used
to frame a request for an operation to occur. The request for
operations to occur are written in terms of XACML action items. This
specification defines a number of actions specific to the use of this
document in a CMS environment. Other specifications may define
additional action items for other environments (for example the XML
encryption environment) or other purposes. (It has been suggested
that this basic structure could be used to standardize the dialogs
between PDPs and PAPs.)
In addition to the XACML action request there is a set of structures
to allow for a variety of authentication mechanisms to be used. By
allowing for the use of SAML and GSS-API as base authentication
mechanisms, the mechanism used is contained in a sub-system and thus
does not directly impact the protocol. Additionally the
authentication can be performed by the secure transport, for example
TLS with client authentication by X.509 certificates or a login
dialog box.
The request message uses a single XML structure. This structure is
the eps:PlasmaRequest object. The XML Schema used to describe this
structure is:
<xs:element name="PlasmaRequest" type="RequestType"/>
<xs:complexType name="RequestType">
<xs:sequence>
<xs:element ref="Authentication" minOccurs="0"/>
<xs:element ref="xacml:Request" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
A Plasma Request will have two elements in it:
Authentication is an optional element that contains the various
methods of authentication that are available for use. The
authentication element is also used to contain SAML assertions
containing attributes about the individual being authenticated.
xacml:Request is an optional element that contains the control
information for the action requested. The control information
takes the form of an action request plus additional data to be
used as part of the action request. The data and actions are to
be treated as self-asserted, this is they are deemed not to come
from a reliable source even in the event that an authentication is
successfully completed. Attributes for the policy enforcement
SHOULD NOT be self-asserted values. This element is taken from
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the XACML specification.
Clients sending a Plasma Request to a server MUST populate one or
both elements.
5.1. Authentication Element
NOTE: I think this section goes away as it is covered later.
The authentication type is used to carry information about the
different ways that the Plasma server will allow for authentication
to occur. More than one authentication field can be filled in when
sending message to the server. If more than one authentication field
is set, then the server can select which fields are to be used. More
than one field can be used.
Additionally, the authentication element can be used to transport
attributes about the entity being authenticated by including a SAML
assertion with the attribute values. The assertion of attributes is
treated as being separate from authentication, however a single SAML
assertion can contain both authentication and attribute information.
The XML Schema used for the Authentication element is:
<xs:element name="Authentication" type="AuthenticationType"/>
<xs:complexType name="AuthenticationType">
<xs:sequence>
<xs:element name="SAML_Collection" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element ref="saml:Assertion" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="GSS_API" type="xs:hexBinary" minOccurs="0"/>
<xs:element name="WS_Token" type="xs:hexBinary" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="ds:Signature" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
The fields of this element are:
SAML_Collection holds a sequence of one or more SAML assertions.
These assertions can contain statements about attributes or keys
for the requester.
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GSS_API holds a GSS-API message object. This message object will
normally be using the GSS-API/EAP method defined by [ABFAB].
WS_Token holds a WS-Token obtained from some source. The most
common source for a WS-Token to be obtained from will be from a
previous conversation with a Plasma server. For example, one or
more WS-Tokens will be returned from a Get Roles dialog.
ds:Signature
5.2. xacml:Request Element
We use the xacml:Request element for creating the access control
request of the Plasma Server. When the request element is present,
one will normally have an attribute from the
urn:oasis:names:tc:xacml:3.0:attribute-category. This document
defines a set of actions to be used with the server.
Additional attributes can be added to the request as well. These
attributes can help control what is happening to the message and
provide additional data to the request. When attributes are to be
provided in an authenticated manner, then they must be provided in a
different manner than being placed here. Unless self-assertion is
considered sufficient.
For convenience the schema for the xacml:Request element is
reproduced here:
<xs:element name="Request" type="xacml:RequestType"/>
<xs:complexType name="RequestType">
<xs:sequence>
<xs:element ref="xacml:RequestDefaults" minOccurs="0"/>
<xs:element ref="xacml:Attributes" maxOccurs="unbounded"/>
<xs:element ref="xacml:MultiRequests" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="ReturnPolicyIdList" type="xs:boolean" use="required"/>
<xs:attribute name="CombinedDecision" type="xs:boolean" use="required"/>
</xs:complexType>
The use of the RequestDefaults element is possible, but will
generally not be supported. The use of MultiRequest element is
strongly discouraged.
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6. Plasma Response Element
There is a single top level structure that is used by the server to
respond to a client request.
The XML Schema used to describe the top level response is as follows:
<xs:element name="PlasmaResponse" type="ResponseType"/>
<xs:complexType name="ResponseType">
<xs:sequence>
<xs:element ref="xacml:Response"/>
<xs:element name="PlasmaTokens" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element ref="PlasmaToken" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="CMSToken" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:hexBinary">
<xs:attribute name="TokenId" type="xs:string" use="optional"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element ref="CMSKey" minOccurs="0"/>
<xs:element ref="Authentication" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
A Plasma Response has three elements used:
xacml:Response is a mandatory element that returns the status of the
access request.
PlasmaTokens is an optional element that will return one or more
PlasmaToken elements.
CMSToken is an optional element that contains the CMS Token that is
included in a CMS message as part of a recipient info element.
CMSKey is an optional element that contains the key to be used in
decrypting a CMS message.
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Authentication return a GSS-API element as part of a GSS-API
authentication process. Also return a challenge. A full
discussion of the Authentication element can be found in
Section 7.
6.1. xacml:Response Element
The xacml:Response element has the ability to return both a decision,
but additionally information about why a decision was not made.
The schema for the xacml:Response element is reproduced here for
convenience:
<xs:element name="Response" type="xacml:ResponseType"/>
<xs:complexType name="ResponseType">
<xs:sequence>
<xs:element ref="xacml:Result" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<xs:element name="Result" type="xacml:ResultType"/>
<xs:complexType name="ResultType">
<xs:sequence>
<xs:element ref="xacml:Decision"/>
<xs:element ref="xacml:Status" minOccurs="0"/>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
<xs:element ref="xacml:AssociatedAdvice" minOccurs="0"/>
<xs:element ref="xacml:Attributes" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="xacml:PolicyIdentifierList" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
The xacml:Response element consists of one child the Result. While
the schema allows for multiple results to be returned, it is
constrained to be a single Result returned in this specification as
only a single request will ever be made at one time.
The xacml:Response element consists of the following elements:
xacml:Decision is a mandatory element that returns the possible
decisions of the access control decision. The set of permitted
values are Permit, Deny, Indeterminate and No Policy.
xacml:Status is an optional element returned for the Indeterminate
status which provides for the reason that a decision was not able
to be reached. Additionally it can contain hints for remedying
the situation. This document defines a new set of status values
to be returned. Formal declaration may be found in Section 13.
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* gss-api indicates that a gss-api message has been returned as
part of the authentication process.
xacml:Obligations is designed to force the PEP to perform specific
actions prior to allowing access to the resource. This element is
not used by Plasma and SHOULD be absent. If a response is
returned with this element present, the processing MUST fail
unless the PEP can perform the required action. A set of Plasma
specific obligations are found in Section 11.2.
xacml:AssocatedAdvice is designed to give suggestions to the PEP
about performing specific actions prior to allowing access to the
resource. This element is not used by Plasma and SHOULD be
absent. If the response is returned with this element present,
processing will succeed even if the PEP does not know how to
perform the required action. A set of Plasma specific advoice
elements are found in Section 11.2.
xacml:Attributes provides a location for the server to return
attributes used in the access control evaluation process. Only
those attributes requested in the Attributes section of the
request are to be returned. Since Plasma does not generally
supply attributes for the evaluation process, this field will
normally be absent.
xacml:PolicyIdentifierList provides a location to return the set of
policies used to grant access to the resource. This element is
expected to be absent for Plasma.
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7. Authentication Element
One of the major goals in the Plasma work is to attempt and detach
the process of authentication specifics from the Plasma protocol. In
order to accomplish this we are specifying the use of two general
mechanisms (SAML and GSS-API) which can be configured and expanded
without changing the core Plasma protocol itself. The authentication
element has two main purposes: 1) to process the authentication being
used by the client and 2) to carry authenticated attributes for use
in the policy evaluation.
When transporting the authentication information, one needs to
recognize that there may be a single or multiple messages in the
dialog in order to complete the authentication process. In
performing the process of authenticating, any or all of the elements
in this structure can be used. If there are multiple elements filled
out, the server can choose to process the elements in any order.
This means that the Plasma protocol itself does not favor any
specific mechanism. The current set of mechanisms that are built
into the Plasma specification are:
o SAML Assertions - many different types of SAML assertions are
supported. The specification allows for both bearer and holder of
key assertions.
o X.509 Certificates can be used for the purpose of authentication
by creating a signature with the XML Digital Signature standard.
o GSS-API - the specification allows for the use of GSS-API in
performing the authentication process. The ABFAB mechanism in
GSS-API is specifically designed for use in a federated community
and allows for both authentication and attribute information to be
queried from the identity server.
o WS-Trust tokens allow for much of the same type of information to
be passed as SAML assertions. The Plasma specification has been
designed mailing for the use of WS-Trust tokens to be used for
caching prior authentication sessions.
More than one authentication element may be present in any single
message. This is because a client may need to provide more than one
piece of data to a server in order to authenticate, for example a
holder of key SAML Assertion along with a signature created with that
key. Additionally a client may want to provide the server an option
of different ways of doing the authentication. In a federated
scenario, an X.509 certificate with a signature can be presented and
the server may not be able to build a trust path to it's set of trust
anchors. In this case the server may opt to use the GSS-API/EAP
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protocol for doing the authentication. Finally, the client may want
to provide the server with a SAML Assertion that binds a number of
attributes to it's identities so that the server does not need to ask
for those attributes at a later time.
When transporting the attribute information, one needs to recognize
that there may be single or multiple messages in the dialog in order
to complete the authorization process. The PDP will return a status
code of urn:oasis:names:xacml:1.0:status:missing-attribute in the
event that one or more attributes are needed in order to complete the
authorization process. The details on how XACML returns missing
attribute information is found in Section 7.17.3 of [XACML]. When
the list of attributes is returned, the client has two choices: 1) It
can close the dialog, look for a source of the missing attributes and
then start a new dialog, 2) it can just get an assertion for the
missing attributes and send the new assertion as in a new request
message within the same dialog. The decision of which process to use
will depend in part on how long it is expected to take to get the new
attribute assertion to be returned.
The schema for the Authentication element directly maps to the
ability to hold the above elements. The schema for the
Authentication element is:
<xs:element name="Authentication" type="AuthenticationType"/>
<xs:complexType name="AuthenticationType">
<xs:sequence>
<xs:element name="SAML_Collection" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element ref="saml:Assertion" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="GSS_API" type="xs:hexBinary" minOccurs="0"/>
<xs:element name="WS_Token" type="xs:hexBinary" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="ds:Signature" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
7.1. SAML Collection Element
The SAML collection element provides a holder to place one or more
SAML Assertions[anchor16]. SAML has defined three different types of
assertions in it's core specification [OASIS-CORE]:
o Authentication: The assertion subject was authenticated by a
particular means at a particular time.
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o Attribute: The assertion subject is associated with the supplied
attributes.
o Authorization Decision: A request to allow the assertion subject
to access the specified resource has been granted or denied.
While a PDP can use an Authorization Decision as input, this is
unexpected and MAY be supported. In addition there are three
different ways that the subject of a SAML statement can be
identified:
o A bearer statement: These statements are belong to anybody who
presents them. The owner is required to take the necessary
precautions to protect them.
o A holder of key statement: These statements belong to anybody who
can use the key associated with the statement.
o Subject name match: These statements can be associated to an
identity by matching the name of the entity.
When a holder of key identification is used, the XML Signature
element is used to provide the key usage element.
We cannot pass a SAML assertion with attributes as a single attribute
in the XACML request as XACML wants each of the different attributes
to be individually listed in the request. This greatly simplifies
the XACML code, but means that one needs to do a mapping process from
the SAML attributes to the XACML attributes. This process has been
discussed in Section 2 of [SAML-XACML]. This mapping process MUST be
done by a trusted agent, as there are a number of steps that need to
be done including the validation of the signature on the SAML
assertion. This process cannot be done by the PEP that is residing
on the Plasma client's system as this is considered to be an
untrusted entity by the Plasma system as a whole. One method for
this to be addressed is to treat the Plasma server as both a PDP (for
the Plasma client) and a PDP for the true XACML policy evaluator. In
this model, the Plasma server becomes the trusted PEP party and has
the ability to do the necessary signature validation and mapping
processes. A new XACML request is then created and either re-
submitted to itself for complete evaluation or to a third party which
does the actual XACML processing.
7.2. WS Trust Tokens
WS Trust tokens are used in two different ways by this specification.
They can be used as the primary introduction method of a client to
the server, or they can be used by the server to allow the client to
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be re-introduced to the server in such a way that the server can use
cached information.
WS Trust tokens come in two basic flavors: Bearer tokens and Holder
of Key tokens. With the first flavor, presentation of the token is
considered to be sufficient to allow the server to validate the
identity of the presenter and know the appropriate attributes to make
a policy decision. In the second flavor some type of cryptographic
operation is needed in addition to just presenting the token. The
Signature element Section 7.3 provides necessary infrastructure to
permit the cryptographic result to be passed to the server.
This document does not define the content or structure of any tokens
to be used. This is strictly an implementation issue for the servers
in question. This is because the client can treat the WS Token value
presented to it as an opaque blob. Only the servers need to
understand how to process the blob. However there are some
additional fields which can be returned in addition to the token that
need to be discussed:
wst:TokenType SHOULD be returned if more than one type of token is
used by the set of servers. If a token type is returned to the
client, the client MUST include the element when the token is
returned to the server.
wst:BinarySecret SHOULD be returned for moderate duration tokens.
If a binary secret is returned then the client MUST provide
protection for the secret value. When a binary secret has been
returned, then the client MUST create either a signature or MAC
value and place it into the Signature element Section 7.3.
[anchor18].
wst:Lifetime MUST be returned with the wsu:Expires element set. The
wsu:Created element MAY be included. The element provides the
client a way to know when a token is going to expire and obtain a
new one as needed.
7.3. XML Signature Element
When a holder of key credential is used to determine the attributes
associated with an entity, there is a requirement that the key be
used in a proof of possesion step so that the Plasma server can
validate that the entity does hold the key. The credentials can hold
either asymmetic keys (X.509 certificates and SAML Assertions) or
symmetic keys (WS Trust TOkens and SAML Assertions) which use Digital
Signatures or Message Authentication Codes (MACs) respectively to
create and validate a key usage statement. The XML signature
standard [XML-Signature] provides an infrastructure to for holding
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the proof of possession information.
When the XML Signature element is used in the first message of the
dialog, an XACML Request element be present in the document. In this
case the signature is to be computed over the XACML Request. After
the first message, the XACML Request element may be present, but
usually is not. When the XACML Request element is present in the
subsequent messages it may be signed, however the SignBody XML
element has been defined for use in subsequenct messages. The XML
schema for this element is:
<xs:element name="SignBody" type="SignBodyType"/>
<xs:complexType name="SignBodyType">
<xs:sequence>
<xs:element name="ChannelBinding" type="xs:base64Binary"/>
</xs:sequence>
</xs:complexType>
In the SignBodyType show above, the ChannelBinding element contains a
value derived from the TLS tunnel used to transport the protocol.
The details for the value derivation can be find in section
Section 11.1.1. By the use of a value which is derived from the
cryptographic keys used in for protecting the tunnel, it is possible
for the server to verify that the authentication values computed were
done specifically for this specific conversation and are not replayed
from previous conversations.
When creating either a signature or a MAC, the following statements
hold:
o The canonicalization algorithm Canonical XML 1.1 [XML-C14N11]
without comments MUST be supported and SHOULD be used in preparing
the XML node set for hashing. Other canonicalization algorithms
MAY be used.
o The Signature element SHOULD include an Enveloped Signature
Transformation (Section 6.6.4 of [XML-Signature] but MAY be the
root of the Plasm request. Both methods MUST be supported by
Plasma servers.
o The signature algorithms RSAwithSHA256 and ECDSAwithSHA256 MUST be
supported by both clients and servers. The MAC algorithm HMAC-
SHA256 MUST be supported by both clients and servers. Other
signature and MAC algorithms MAY be supported.
o Set the additional attributes that must be included in a signature
- what should they be?
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o If an xacml:Request element is referenced by an XML Signature
element, the xacml:Request element MUST include the ChannelBinding
token (Section 11.1.1) as one of the attributes.
o The keys used in computing the authentication value need to be
identified for the recipient. For X509 certificates, the full raw
certificate will normally be included as part of the signature,
but MAY be referenced instead. For SAML assertions, the specific
assertion carrying the asymmetric key can be identified by TBD
HERE. In the event that symmetric keys are used by holder of key
assertions, the specific assertion will be identified by TBD HERE.
In these cases the server is expected to be able to associated the
key with the assertion by some means (either locally or perhaps
encrypted into the assertion).
7.4. GSS-API Element
TBD - rules for using GSS-API in general and the EAP version from
ABFAB particularly.
o How to build the name.
o Must use a secure tunnel for the outer EAP method and an
appropriate inner EAP method(s) to accomplish the required level
of authentication.
o Server query of attributes and specification of LOA to the EAP
IdP.
o Any additional Trust model items.
o How round trips are accomplished - the only case that a server
will send back an Authentication element is on return processing
of GSS-API messages.
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8. Role Token and Policy Acquisition
In order to send a message using a Plasma server, the first step is
to obtain a role token that provides the description of the lables
that can be applied and the authorization to send a message using one
or more of the labels. The process of obtaining the role token is
designed to be a query/response round trip to the Plasma server. In
practice a number of round trips may be necessary in order to provide
all of the identity and attributes to the Plasma server that are
needed to evaluate the policies for the labels. An example of a
request token can be found in Appendix B.
When a Plasma server receives a role token request from a client, it
needs to perform a policy evaluation for all of the policies that it
arbitrates along with all of the options for those policies. In
general, the first time that a client requests a role token from the
server, it will not know the level of authentication that is needed
or the set of attributes that needs to be presented in order to get
the set of tokens. A server MUST NOT issue a role token without
first attempting to retrieve from an attribute source (either the
client or a back end server) all of the attributes required to check
all policies. Since the work load required on the server is expected
to be potentially extensive for creating the role token, it is
expected that the token returned will be valid for a period of time.
This will allow for the frequency of the operation to be reduced.
While the use of an extant role token can be used for identity proof,
it is not generally suggested that a new token be issued without
doing a full evaluation of the attributes of the client as either the
policy or the set of client attributes may have changed in the mean
time.
8.1. Role Token Request
The process starts by a client sending a server a role token request.
Generally, but not always, the request will include some type of
identity proof information and a set of generic attributes. It is
suggested that, after the first successful conversation, the client
cache hints about the identity and attributes needed for a server.
This allows for fewer round trips in later conversations.
The role token request, as with all requests, is always built using
the eps:PlasmaRequest XML structure. The xacml:Request element MUST
be included on the first message, but is omitted on subsequent
authentication round trips. The eps:Authentication MAY be included
on the first message (depending on how authentication is going to be
done) and MUST be included on subsequent authentication round trips.
When sending the role token there are a number of things that can be
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done. These include:
o The client can optionally include an attribute to specify the name
to be used for policy evaluation purposes. If this attribute is
absent, then the name is extracted from the identity proof
provided externally. This attribute allows for a client to get
delegated permissions for a third party. One case where this
would be used is for an executive assistant to be able to act as
the executive for reading certain types of messages. When this
behavior is desired, the following attribute is used:
Category="urn:oasis:names:tc:xacml:1.0:subject-category:access-
subject"
AttributeId="urn:oasis:names:tc:xacml:1.0:data-type:rfc822Name"
Plasma servers MUST implement the rfc822Name attribute id, other
name forms MAY be implemented as well.
o The client MUST include an action attribute. This document
defines the action attribute to be used for requesting role
tokens:
Category="urn:oasis:name:tc:xacml:3.0:attribute-category:action"
AttributeId="urn:ietf:plasma:action-id"
Attribute Value: GetRoleTokens
o If the client is using the XML Digital Signature element in this
message, then the client MUST include the cryptographic channel
binding token (Section 11.1.1) in the set of XACML attributes.
o The client can optionally include a SAML assertion in the
Authentication section of the message. See section Section 7.1
for more information on how to deal with SAML assertions carrying
attribute statements.
An example of a message requesting the set of policy information is:
<esp:PlasmaRequest>
<eps:Authentication>...</eps:Authentication>
<xacml:Request>
<xacml:Attributes Category="...:action">
<xacml:Attribute AttributeId="urn:plasma:action-id">
<xacml:AttributeValue
DataType="http://www.w3.org/2001/XMLSchema#string">
GetRoleToken</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
</xacml:Request>
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</esp:PlasmaRequest>
In this example the identity information of the requester is implicit
from the data in the Authentication element.
8.2. Request Role Token Response
In response to a role token request message, the Plasma server
returns a role token request message. The response message uses the
eps:PlasmaResponse XML structure. When a response message is create
the following should be noted:
o An xacml:Decision is always included in a response message. The
values permitted are:
Permit is used to signal success. In this case the response
message MUST include an eps:PlasmaTokens element.
Deny is used to signal failure. In this case the xacml:Status
element MUST be present an contain a failure reason.
Indeterminate is used to signal that a result cannot yet be
reached. In this case there must be a request for additional
attributes in the xacml:Result/Attributes element or additional
authentication information to be carried in TBD.
NotApplicable is returned if the Plasma server does not have the
capability to issue role tokens.
An example of a message returning the set of policy information is:
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<eps:PlasmaResponse>
<xacml:Response>
<xacml:Result>
<xacml:Decision>Permit</xacml:Decision>
</xacml:Result>
</xacml:Response>
<eps:PlasmaTokens>
<eps:PlasmaToken>
<eps:PolicyList>
<eps:Policy>
Details of a policy
</eps:Policy>
... More policies ...
<wst:RequestSecurityTokenResponse>
<wst:TokenType>urn:...:plasma:roleToken</wst:TokenType>
<wst:RequestedSecurityToken>...</wst:RequestedSecurityToken>
</wst:RequestSecurityTokenResponse>
</eps:PolicyList>
</eps:PlasmaToken>
</eps:PlasmaTokens>
</eps:PlasmaResponse>
In this example, the Email Policy Service is returning three
different policies that can be used along with a security token and a
key to be used with the token when sending a message.
8.2.1. PlasmaTokens XML element
The eps:PlasmaTokens element is used to return one or more tokens to
the client. Each token returned will contain one or more policies
that can be asserted with the token and the token itself.
Additionally the name of a Plasma server to be used with the token
can be included as well as cryptographic information to be used with
the token.
The schema used for the PlasmaTokens element is:
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<xs:element name="PlasmaToken" type="PlasmaTokenType"/>
<xs:complexType name="PlasmaTokenType">
<xs:sequence>
<xs:element name="PDP" type="xs:anyURI" maxOccurs="unbounded"/>
<xs:choice>
<xs:element name="PolicyList">
<xs:complexType>
<xs:sequence>
<xs:element name="Policy" type="PolicyType" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element ref="Label"/>
</xs:choice>
<xs:element ref="wst:RequestSecurityTokenResponse"/>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
<xs:element ref="xacml:AssociatedAdvice" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="PolicyType">
<xs:sequence>
<xs:element name="Name" type="xs:string"/>
<xs:element name="Identifier" type="xs:string"/>
<xs:element name="Options" type="xs:anyType"/>
</xs:sequence>
</xs:complexType>
The eps:PlasmaTokens field will contain one or more eps:PlasmaToken
elements.
The eps:PlasmaToken element contains the following items:
PDP is an optional element. If the element is present, it provides
one or more URLs to be used for containing a Plasma server for the
purpose of sending a message. This element allows for the use of
different Plasma servers for issuing role tokens and message
tokens. No ranking of the servers is implied by the order of the
URLs returned.
PolicyList contains the description of one or more policies that can
be asserted using the issued token. Any of the policies contained
in the list may be combined together using the policy logic in
constructing a label during the send message process.
Label contains a single specific label. This element is returned as
part of a read message token to allow for replies to be formulated
by an entity that cannot generally originate a message using the
policy.
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wst:RequestSecurityTokenResponse contains the actual token itself.
The eps:PolicyType type is used to represent the elements of a policy
to the client. The elements in this type are:
Name contains a display string that represents the policy. This
element is localized in response to the TBD attribute in the TBD
field.
Identifier contains a "unique" identifier for the policy. This is
the value that identifies the policy to the software. The type
for the value is defined as a string and is expected to be either
a URN, and Object Identifier or some equally unique identifier.
Options allows for a set of options to be specified for the policy.
The set of options is dependent on the policy and only those
clients which have pre-knowledge of a policy are expected to be
able to deal with them. The options can range from a simple
yes/no selection to a list of strings. An example of using
options is provided by the basic policies defined in [TBD] where a
set of RFC 822 names is provided.[anchor21]
When building the wst:RequestSecurityTokenResponse element, the
following should be noted:
A wst:RequestedSecruityToken element containing the security token
MUST be included. The format of the security token is not
specified and is implementation specific, it is not expected that
. Examples of items that could be used as security tokens are
SAML statements, encrypted record numbers in a server database.
A wst:Lifetime giving the life time of the token SHOULD be
included. It is not expected that this should be determinable
from the token itself and thus must be independently provided.
There is no guarantee that the token will be good during the
lifetime as it make get revoked due to changes in credentials,
however the client is permitted to act as if it were. The token
provided may be used for duration. If this element is absent, it
should be assumed that the token is either a one time token or of
limited duration.
Talk about cryptographic information
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9. Sending A Message
After having obtained a role token from a Plasma server, the client
can then prepare to send a message by requesting a message token from
the Plasma server. As part of the preparatory process, the client
will construct the label to be applied to the message from the set of
policies that it can assert, determine the optional elements for
those policies which have options, generate the random key encryption
key and possible create the key recipient structures for the message.
Although this section is written in terms of a CMS Encrypted message,
there is nothing to prevent the specification of different formats
and still use this same basic protocol. An example of a request
token exchange can be found in Appendix D.
9.1. Send Message Request
The send message request is built using the eps:PlasmaRequest XML
structure. When building the request, the following aplies:
o The eps:Authentication element MAY be included in the initial
message. The authorization is supplied by the role token which is
included in the data structure, however authentication may be
required as well. The authentication data is placed here.
o The xacml:Request element MUST be included in the initial message.
o The client MUST include an action attribute. This document
defines the action attribute to be used for purpose:
Category = "urn:oasis:name:tc:xacml:3.0:attribute-category:action"
AttributeId="urn:ietf:plasma:action-id"
Attribute Value= GetSendCMSToken
o The client MUST include a data attribute. This attribute contains
the information that is used to build the CMS Message token to be
returned. There MAY be more than one data attribute, but this
will not be a normal case. More details on this attribute are in
Section 9.1.1.
o If the client is using the XML Digital Signature element in this
message, then the client MUST include the cryptographic channel
binding token (xref target="ChannelBind"/>) in the set of XACML
attributes.
An example of a message returning the set of policy information is:
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<eps:PlasmaRequest>
<eps:Authentication>
<eps:WS_Token>
Role Token goes here
</eps:WS_Token>
<xacml:Request>
<xacml:Attributes Category="...:action">
<xacml:Attribute AttributeId="urn:plasma:action-id">
<xacml:AttributeValue>
GetSendCMSToken
</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
<xacml:Attributes Category="...:data">
<xcaml:Attribute AttributeId="urn:plasma:data-id">
<xacml:AttributeValue>
Label and keys
</xacml:AttributeValue>
</xcaml:Attribute>
</xacml:Attributes>
</xacml:Request>
</eps:Authentication>
</eps:PlasmaRequest>
9.1.1. CMS Message Token Data Structure
The message token data structure is used as an attribute to carry the
necessary information to issue a CMS message token. The schema that
describes the structure is:
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<xs:element name="MessageTokenRequest" type="MessageTokenRequestType"/>
<xs:complexType name="MessageTokenRequestType">
<xs:sequence>
<xs:element name="RoleToken"/>
<xs:element ref="Label"/>
<xs:element ref="RecipientInfo" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="KEK" type="xs:hexBinary" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:element name="RecipientInfo" type="RecipientInfoType"/>
<xs:complexType name="RecipientInfoType">
<xs:sequence>
<xs:element name="Subject" maxOccurs="unbounded">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:anySimpleType">
<xs:attribute name="type" type="xs:string" use="required"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="LockBox" type="xs:hexBinary"/>
</xs:sequence>
</xs:complexType>
When used in an xacml:Attribute, the structure is identified by:
Category = "urn:oasis:name:tc:xacml:3.0:attribute-category:data"
AttributeId = "urn:ietf:plasma:data-id"
DataType = "http://www.w3.org/2001/XMLSchema#anyType"
The elements of the structure are used as:
RoleToken contains the previously issued role token which provides
the authorization to use the policies in the label.
Label contains the label to be applied to the message.
Recipients is an optional element that contains one or more
recipient info structures.
KEK is an optional element that contains the KEK to decrypt the CMS
lock box.
One or both of KEK and Recipients MUST be present.
The elements of the RecipientInfoType structure are:
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Subject contains a subject identifier. Since a CMS recipient info
structure does not contain a great deal of information about the
recipient, this element contains a string which can be used to
identify the subject. This will normally be an RFC 822 name.
Multiple subject names can be provided for a single lock box.
This allows for the use a KEK value that is shared among the set
of recipients but not the Plasma server.
LockBox contains a hex encoded CMS Recipient Info structure. If the
recipient info structure is placed here, it MUST NOT be placed in
the CMS EnvelopedData structure as well.
9.2. Send Message Response
In response to a send message request, the Plasma server returns a
send message response message. The response messages uses the eps:
PlasmaResponse XML structure. When the response message is created,
the following should be noted:
o The xacml:Decisions is always included in the response. If the
'Permit' value is returned then the eps:CMSToken element MUST be
present.
o The eps:CMSToken element is included in a success message. It
contains value of the keyatt-eps-kek attribute defined in
[EPS-CMS].
An example of a message returning the set of policy information is:
<eps:PlasmaResponse>
<xacml:Response>
<xacml:Result>
<xacml:Decision>Permit</xacml:Decision>
</xacml:Result>
</xacml:Response>
<eps:CMSToken>234e34d3</eps:CMSToken>
</eps:PlasmaResponse>
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10. Decoding A Message
When the receiving agent is ready to decrypt the message, it
identifies that there is a KEKRecipientInfo object which contains a
key attribute identified by id-keyatt-eps-token. It validates that
communicating with the Email Policy Service is within local policy
and then sends a request to the service to obtain the encryption key
for the message.
In some cases the recipient of a message is not authorized to use the
same set of labels for sending a message. For this purpose a token
can be returned in the message along with the key so that recipient
of the can reply to the message using the same set of security
labels.
10.1. Requesting Message Key
The client sends a request to the Plasma server that is identified in
the token. For the CMS base tokens, the address of the Plasma server
to use is defined in [EPS-CMS] this is located in the aa-eps-url
attribute.
The request uses the eps:PlasmaRequest XML structure. When building
the request, the following should be noted:
o The xacml:Request MUST be present in the first message of the
exchange.
o The action used to denote that a CMS token should be decrypted is:
Category="urn:oasis:names:tc:xaml:3.0:attribute-category:action"
AttributeId="urn:ietf:plasma:action-id"
Attribute Value: ParseCMSToken
o The CMS token to be cracked is identified by:[anchor22]
Category="urn:oasis:names:tc:xacml:3.0:attribute-cateogry:data"
AttributeId="urn:ietf:plasma:data-id"
Attribute Value: CMSToken
o In the event that a reply to role token is wanted as well, then
that is supplied as a separate action:
Category="urn:oasis:names:tc:xaml:3.0:attribute-category:action"
AttributeId="urn:ietf:plasma:action-id"
Attribute Value: GetReplyToken
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o If the client is using the XML Digital Signature element in this
message, then the client MUST include the cryptographic channel
binding token (xref target="ChannelBind"/>) in the set of XACML
attributes.
An example of a message returning the set of policy information is:
<eps:PlasmaRequest>
<eps:Authentication>...</eps:Authentication>
<xacml:Request>
<xacml:Attributes Category="...:action">
<xacml:Attribute AttributeId="..:action-id">
<xacml:AttributeValue>ParseCMSToken</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
<xacml:Attribute Category="...:data">
<xacml:Attribute AttreibuteId="..:data-id">
<xacml:AttributeValue>
Hex encoded CMS Token Value
</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attribute>
</xacml:Request>
</eps:PlasmaRequest>
10.2. Requesting Message Key Response
In response to a message key request, the Plasma server returns a
decrypted key. The response message uses the eps:Plasma XML
structure. When a response message is create the following should be
noted:
o If the value of xacml:Decision is Permit, then response MUST
include an eps:CMSKey element.
o If a reply token was requested and granted, then the response MUST
include an eps:PlasmaToken element. The eps:PlasmaToken element
MUST use the Label option
An example of a message returning the set of policy information is:
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<eps:PlasmaResponse>
<xacml:Response>
<xacml:Result>
<xacml:Decision>Permit</xacml:Decision>
</xacml:Result>
</xacml:Response>
<eps:CMSKey>
<eps:DisplayString>Label TExt</eps:DisplayString>
<eps:KEK>hex based KEK</eps:KEK>
</eps:CMSKey>
</eps:PlasmaResponse>
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11. Plasma Attributes
In this document a number of different XAMCL attributes have been
defined, this section provides a more detailed description of these
elements.
11.1. Data Attributes
11.1.1. Channel Binding Data Attribute
The channel binding data attribute is used to provide for a binding
of the TLS session that is being used to transport the Plasma
messages with the content of the Plasma requests themselves. There
is a need for the server to be able to validate that the
cryptographic operations related to holder of key statements be made
specifically for the current conversation and not be left over from a
previous one as a replay attack. By deriving a cryptographic value
from the shared TLS session key and signing that value we are able to
do so.
The channel binding value to be used is created by the TLS key
exporter specification defined in RFC 5705 [RFC5705]. This allows
for a new cryptographic value to be derived from the existing shared
secret key with additional input to defined the context in which the
key is being derived. When using the exporter, the label to be input
into the key exporter is "EXPORTER_PLASMA". The value to be derived
will be 512 bits in length, and no context is provided to the
exporter.
When used as an XACML attribute in a request:
The category of the attribute is
"urn:oasis:names:tc:xacml:3.0:attribute-category:data".
The AttributeId attribute is
"urn:ietf:params:xml:plasma:data-id:ChannelBinding".
The Issuer attribute is absent.
The DataType is either base64Binary or hexBinary
The same value is used for both the XACML channel binding data
attribute and the XML channel binding structure defined in
Section 7.3.
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11.1.2. CMS Signer Info Data Attribute
In many cases a policy stays that the client is required to sign the
message before encrypting it. The server cannot verify that a
signature is applied to the message and included, but we can require
that a signature be supplied to the server. This signature can then
be validated by the server (except for the message digest attribute
value), and the server can take a hash of the value and return it as
part of the key returned to a decrypting agent. This agent can then
validate that the signature is a part of the message and complain if
it absent. This means we do not have an enforcement mechanism, but
we do have a way of performing an audit at a later time to see that
the signature operation was carried out correctly.
By requiring that a signature be supplied to the server as part of
the authentication process, the Plasma server can also be setup so
that the supplied signature is automatically setup for archival
operations. One way to do archiving is to use the data records
defined in [RFC4998].
The following applies when this data value is present:
The Category attribute is
"urn:oasis:names:tc:xacml:3.0:attribute-category:data".
The AttributeId attribute is
"urn:ietf:params:xml:plasma:data-id:CMSSignerInfo".
The Issuer attribute is absent.
The DataType attribute is either base64Binary or hexBinary.
11.1.3. S/MIME Capabilities Data Attribute
Policies sometimes require that specific algorithms be used in order
to meet the security needs of the policy. This attribute allows for
an S/MIME Capabilities to be carried in a DER encoded
SMIMECapabilities ASN.1 structure to be transmitted to the client.
Details on how the S/MIME Capabilities function can be found in
[SMIME-MSG].
The following attributes are to be set for the data value:
The Category attribute is
"urn:oasis:names:tc:xacml:3.0:attribute-category:data".
The AttributeId attribute is
"urn:ietf:params:xml:plasma:data-id:SMIME-Capabilties".
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The Issuer attribute is absent.
The DataType attribute is either base64binary or hexBinary.
11.2. Obligations and Advice
Obligations and advice consist of actions that the Plasma server
either requires or requests that the client PEP perform in order to
gain access or before granting access to the data. These normally
represent actions or restrictions that the PDP itself cannot enforce
and thus are not input attributes to the policy evaluation. The same
set of values can be used either as obligations or advice, the
difference being that if the PEP cannot do an obligation it is
required to change the policy decision.
11.2.1. Signature Required
Many policies require that a message be signed before it is encrypted
and sent. Since the unencrypted version of message is not sent to
the Plasma server, the policy cannot verify that a signature has been
placed onto the signed message. The attribute is not for use as a
returned obligation from an XACML decisions, rather it is for a pre-
request obligations used in role responses (Section 8.2).
When used as an Obligation:
The ObligationId attribute is
"urn:ietf:params:xml:plasma:obligation:signature-required".
A S/MIME Capabilities data value can optionally be included. If
it is included, then it contains the set of S/MIME capabilities
that describes the set of signature algorithms from which the
signature algorithm for the message MUST be selected.
11.2.2. Encryption Required
Occasionally a policy requires a specific set of encryption
algorithms be used for a message, when this is the case then the
encryption required obligation is included in the returned set of
obligations. If the default set of encryption algorithms is
sufficient then the obligation is omitted.
When used as an Obligation:
The ObligationId attribute is
"urn:ietf:params:xml:plasma:obligation:encryption-required".
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An S/MIME Capabilities data value MUST be included containing the
set of permitted encryption algorithms. The algorithms included
MUST include a sufficient set of algorithms for the message to be
encrypted. An absolute minimum would be a content encryption
algorithm and key encryption algorithm.
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12. Security Considerations
To be supplied after we have a better idea of what the document looks
like.
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13. IANA Considerations
We define the following name spaces
New name space for the plasma documents urn:ietf:params:xml:ns:plasma
Define a new action name space
urn:ietf:params:xml:ns:plasma:action-id
GetRoleTokens
GetSendCMSToken
ParseCMSToken
GetReplyToken
Define a new data name space urn:ietf:params:xml:ns:plasma:data-id
CMSToken
ChannelBinding
SMIME-Capabilities
Define a new name space for status codes at
urn:ietf:params:xml:ns:plasma:status. The initial set of values is
authentication-error This identifier indicates that the
authentication methods failed to successfully complete.
Define a new name space for obligations. The same namespace will be
used both for obligations and for advice and the values may appear in
either section.
signature-required This identifier indicates that that the encrypted
body must contain a signature element. The data value of this
type shall be "http://www.w3.org/2001/XMLSchema#hexBinary" and the
data structure shall consist of a DER encoded CMSCapabilities
structure [SMIME-MSG] with the list of permitted signature
algorithms. If there are no restrictions on the algorithms or the
restriction is implicit, then the data value MAY be omitted.
encryption-algorithms see above
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ambigous-identity The identity of the client is either not stated in
a form the Plasma server understands, or there are multiple
identities in the authentication data. To remedy this situation,
the client includes an explicit identity in the xacml:Reqeust
element.
We define a schema in appendix A at
urn:ietf:params:xml:schema:plasma-RFCTBD
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14. Open Issues
List of Open Issues:
o JLS: URL definitions - do we need a new schema or do we just
overload https? For our URLs - do we require that they be passed
through the internationalization step first? Probably should
since the locale information is on the server and the client might
not agree.
o JLS: Should we require that any SignatureProperty be present for
XML Signature elements?
o JLS: Need to figure out an appropriate way to reference the
assertion from a dig sig element. Could use a special version of
RetrievalMethod with a transform, but that does not seem correct.
May need to define a new KeyInfo structure to do it.
o JLS: Should X.509 certificates and attribute certificates be fully
specified as an authentication method?
o JLS: Should a SignerInfo attribute be placed under the access-
subject Category for a senders version and under Environment for a
machine version? Currently both are under Data
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15. References
15.1. Normative References
[ABFAB] Hartman, S. and J. Howlett, "A GSS-API Mechanism for the
Extensible Authentication Protocol", Work In
Progress draft-ietf-abfab-gss-eap-04, Oct 2011.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[EPS-CMS] Schaad, J., "Email Policy Service ASN.1 Processing", Work
In Progress draft-schaad-plamsa-cms, Jan 2011.
[XML-Signature]
Roessler, T., Reagle, J., Hirsch, F., Eastlake, D., and D.
Solo, "XML Signature Syntax and Processing (Second
Edition)", World Wide Web Consortium Recommendation REC-
xmldsig-core-20080610, June 2008,
<http://www.w3.org/TR/2008/REC-xmldsig-core-20080610>.
[XML-C14N11]
Boyer, J. and G. Marcy, "Canonical XML Version 1.1", World
Wide Web Consortium Recommendation REC-xml-c14n11-
20080502, May 2008,
<http://www.w3.org/TR/2008/REC-xml-c14n11-20080502>.
[WS-TRUST]
Lawrence, K., Kaler, C., Nadalin, A., Goodner, M., Gudgin,
M., Barbir, A., and H. Granqvist, "WS-Trust 1.3", OASIS
Standard ws-trust-200512, March 2007, <http://
docs.oasis-open.org/ws-sx/ws-trust/200512/
ws-trust-1.3-os.html>.
[XACML] Rissanen, E., "eXtensible Access Control Markup Language
(XACML) Version 3.0", OASIS Standard xacml-201008,
August 2010, <http://docs.oasis-open.org/xacml/3.0/
xacml-3.0-core-spec-cs-01.en.doc>.
[Plasma] Freeman, T., Schaad, J., and P. Patterson, "Requirements
for Message Access Control", Work in
progress draft-freeman-message-access-control,
October 2011.
[OASIS-CORE]
Cantor, S., Kemp, J., Philpott, R., and E. Maler,
"Assertions and Protocols for the OASIS Security Assertion
Markup Language (SAML) V2.0", OASIS Standard saml-core-
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2.0-os, March 2005.
[RFC5705] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, March 2010.
[SMIME-MSG]
Ramsdell, B. and S. Turner, "Secure/Multipurpose Internet
Mail Extensions (S/MIME) Version 3.2 Message
Specification", RFC 5751, January 2010.
15.2. Informative References
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4998] Gondrom, T., Brandner, R., and U. Pordesch, "Evidence
Record Syntax (ERS)", RFC 4998, August 2007.
[SAML-XACML]
Anderson, A. and H. Lockhart, "SAML 2.0 profile of XACML
v2.0", OASIS Standard access_control-xacml-2.0-saml-
profile-spec-os.pdf, February 2005.
[SOAP11] Box, D., Ehnebuske, D., Kakivaya, G., Layman, A.,
Mendelsohn, N., Nielsen, H., Thatte, S., and D. Winer,
"Simple Object Access Protocol (SOAP) 1.1", W3C NOTE NOTE-
SOAP-20000508, May 2000.
[SOAP12] Lafon, Y., Gudgin, M., Hadley, M., Moreau, J., Mendelsohn,
N., Karmarkar, A., and H. Nielsen, "SOAP Version 1.2 Part
1: Messaging Framework (Second Edition)", World Wide Web
Consortium Recommendation REC-soap12-part1-20070427,
April 2007,
<http://www.w3.org/TR/2007/REC-soap12-part1-20070427>.
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Editorial Comments
[anchor8] Brian: Should one be able to create a policy on the fly
for specific item where a set of attributes can be
defined by the sender of the message.
[anchor16] jls: Should this be the collection element as it
currently is, or should it be an unbounded occurs element
instead?
[anchor18] JLS: I don't know of any way to say use the asymmetric
key that you authenticated with originally - can this be
done?
[anchor21] JLS: I keep wondering if we need to define a set of
minimal structures that can be used for options so that
the entirety is not pushed off onto the client and server
to parse and understand the structures.
[anchor22] jls: I need to think this case out a bit more - I want to
be able to supply multiple CMS tokens at one time,
however I am not sure if that is do able because if you
get a success for one token and a deny for another token
there is no way to handle that in the xacml:Response.
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Appendix A. XML Schema
This appendix represents the entirety of the XML Schema for Plasma
documents.
<?xml version="1.0" encoding="UTF-8"?>
<!-- edited with XMLSpy v2007 sp2 (http://www.altova.com) by James Schaad (exmsft) -->
<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17" xmlns:wst="http://schemas.xmlsoap.org/ws/2005/02/trust" xmlns="urn:ietf:schema:plasma:1.0" xmlns:ds="http://www.w3.org/2000/09/xmldsig#" xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion" targetNamespace="urn:ietf:schema:plasma:1.0" elementFormDefault="qualified" attributeFormDefault="unqualified">
<xs:annotation>
<xs:documentation>
The PlasmaRequest element is one of two top level elements defined by this XSD schema.
The PlasmaRequest element is sent from the client to the server in order to
</xs:documentation>
</xs:annotation>
<xs:element name="PlasmaRequest" type="RequestType"/>
<xs:complexType name="RequestType">
<xs:sequence>
<xs:element ref="Authentication" minOccurs="0"/>
<xs:element ref="xacml:Request" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:element name="PlasmaResponse" type="ResponseType"/>
<xs:complexType name="ResponseType">
<xs:sequence>
<xs:element ref="xacml:Response"/>
<xs:element name="PlasmaTokens" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element ref="PlasmaToken" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="CMSToken" minOccurs="0" maxOccurs="unbounded">
<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:hexBinary">
<xs:attribute name="TokenId" type="xs:string" use="optional"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element ref="CMSKey" minOccurs="0"/>
<xs:element ref="Authentication" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:element name="RequestRoles">
<xs:complexType>
<xs:sequence>
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<xs:element ref="Authentication" minOccurs="0"/>
<xs:element name="Identity" type="xs:string"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="RequestMessageData">
<xs:complexType>
<xs:sequence>
<xs:element name="Label"/>
<xs:element name="RoleToken"/>
<xs:element name="Recipients"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="ReadMessage"/>
<xs:element name="Authentication" type="AuthenticationType"/>
<xs:complexType name="AuthenticationType">
<xs:sequence>
<xs:element name="SAML_Collection" minOccurs="0">
<xs:complexType>
<xs:sequence>
<xs:element ref="saml:Assertion" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="GSS_API" type="xs:hexBinary" minOccurs="0"/>
<xs:element name="WS_Token" type="xs:hexBinary" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="ds:Signature" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="LabelNode">
<xs:choice>
<xs:element name="AND">
<xs:complexType>
<xs:sequence>
<xs:element name="Label" type="LabelNode"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="OR">
<xs:complexType>
<xs:sequence>
<xs:element name="Label" type="LabelNode"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element name="LEAF">
<xs:complexType>
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<xs:simpleContent>
<xs:extension base="xs:string">
<xs:attribute name="label"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:choice>
</xs:complexType>
<xs:element name="PlasmaToken" type="PlasmaTokenType"/>
<xs:complexType name="PlasmaTokenType">
<xs:sequence>
<xs:element name="PDP" type="xs:anyURI" maxOccurs="unbounded"/>
<xs:choice>
<xs:element name="PolicyList">
<xs:complexType>
<xs:sequence>
<xs:element name="Policy" type="PolicyType" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
</xs:element>
<xs:element ref="Label"/>
</xs:choice>
<xs:element ref="wst:RequestSecurityTokenResponse"/>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
<xs:element ref="xacml:AssociatedAdvice" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:complexType name="PolicyType">
<xs:sequence>
<xs:element name="Name" type="xs:string"/>
<xs:element name="Identifier" type="xs:string"/>
<xs:element name="Options" type="xs:anyType"/>
</xs:sequence>
</xs:complexType>
<xs:element name="MessageTokenRequest" type="MessageTokenRequestType"/>
<xs:complexType name="MessageTokenRequestType">
<xs:sequence>
<xs:element name="RoleToken"/>
<xs:element ref="Label"/>
<xs:element ref="RecipientInfo" minOccurs="0" maxOccurs="unbounded"/>
<xs:element name="KEK" type="xs:hexBinary" minOccurs="0"/>
</xs:sequence>
</xs:complexType>
<xs:element name="RecipientInfo" type="RecipientInfoType"/>
<xs:complexType name="RecipientInfoType">
<xs:sequence>
<xs:element name="Subject" maxOccurs="unbounded">
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<xs:complexType>
<xs:simpleContent>
<xs:extension base="xs:anySimpleType">
<xs:attribute name="type" type="xs:string" use="required"/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:element name="LockBox" type="xs:hexBinary"/>
</xs:sequence>
</xs:complexType>
<xs:element name="Label" type="LabelType"/>
<xs:complexType name="LabelType">
<xs:sequence>
<xs:choice>
<xs:element ref="Label" minOccurs="0" maxOccurs="unbounded"/>
<xs:element ref="Leaf" minOccurs="0" maxOccurs="unbounded"/>
</xs:choice>
</xs:sequence>
<xs:attribute name="CombiningRule" type="CombiningRuleType" use="required"/>
</xs:complexType>
<xs:simpleType name="CombiningRuleType">
<xs:restriction base="xs:string">
<xs:enumeration value="and"/>
<xs:enumeration value="or"/>
<xs:enumeration value="except"/>
</xs:restriction>
</xs:simpleType>
<xs:element name="Leaf" type="LeafType"/>
<xs:complexType name="LeafType">
<xs:sequence>
<xs:any namespace="##any" minOccurs="0" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="Label" type="xs:string" use="required"/>
</xs:complexType>
<xs:element name="CMSKey" type="CMSKeyType"/>
<xs:complexType name="CMSKeyType">
<xs:sequence>
<xs:element name="DisplayString" type="xs:string"/>
<xs:choice>
<xs:element name="KEK" type="xs:hexBinary"/>
<xs:element name="KEKIdentifier" type="xs:hexBinary"/>
<xs:element ref="RecipientInfo"/>
</xs:choice>
<xs:element ref="PlasmaToken" minOccurs="0"/>
<xs:element name="EncryptionRequestor" type="xs:string"/>
</xs:sequence>
</xs:complexType>
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<xs:element name="SignBody" type="SignBodyType"/>
<xs:complexType name="SignBodyType">
<xs:sequence>
<xs:element name="ChannelBinding" type="xs:base64Binary"/>
</xs:sequence>
</xs:complexType>
</xs:schema>
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Appendix B. Example: Get Roles Request
This section provides an example of a request message to obtain the
set of roles for an individual named 'bart@simpsons.com'. The
authentication provided in this is a SAML statement included in the
SAML_Collection element.
<?xml version="1.0" encoding="UTF-8"?>
<PlasmaRequest xmlns="urn:ietf:schema:plasma"
xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17">
<Authentication>
<SAML_Collection>...</SAML_Collection>
</Authentication>
<xacml:Request CombinedDecision="false" ReturnPolicyIdList="false">
<xacml:Attributes Category="urn:oasis:names:tc:xacml:1.0:subect-category:access-subject">
<xacml:Attribute IncludeInResult="false"
AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id">
<xacml:AttributeValue
DataType="urn:oasis:names:tc:xacml:1.0:data-type:rfc822Name">bart@simpsons.com</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
<xacml:Attributes Category="urn:oasis:names:tc:xaml:3.0:attribute-catagory:action">
<xacml:Attribute IncludeInResult="false" AttributeId="urn:plasma:action-id">
<xacml:AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">GetRoleTokens</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
</xacml:Request>
</PlasmaRequest>
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Appendix C. Example: Get Roles Response
This section provides an example response to a successful request for
a role sets.
<?xml version="1.0" encoding="UTF-8"?>
<PlasmaResponse xmlns="urn:ietf:schema:plasma:1.0"
xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17"
xmlns:wst="http://schemas.xmlsoap.org/ws/2005/02/trust"
xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<xacml:Response>
<xacml:Result>
<xacml:Decision>Permit</xacml:Decision>
</xacml:Result>
</xacml:Response>
<PlasmaTokens>
<PlasmaToken>
<PDP>https://pdp.example.com/companyPolicies</PDP>
<PolicyList>
<Policy>
<Name>Company Confidential</Name>
<Identifier>urn:example:policies:confidential</Identifier>
</Policy>
<Policy>
<Name>Plasma Project</Name>
<Identifier>urn:example:policies:plasma</Identifier>
</Policy>
</PolicyList>
<wst:RequestSecurityTokenResponse>
<wst:TokenType>urn:plasma:roleToken</wst:TokenType>
<wst:RequestedSecruityToken>....</wst:RequestedSecruityToken>
<wst:Entropy><wst:BinarySecret>12345678</wst:BinarySecret></wst:Entropy>
<wst:Lifetime><wsu:Expires>2012-02-01T00:00:00</wsu:Expires></wst:Lifetime>
</wst:RequestSecurityTokenResponse>
</PlasmaToken>
</PlasmaTokens>
</PlasmaResponse>
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Appendix D. Example: Get CMS Token Request
This section contains an example of a request from a client to a
server for a CMS message token to be issued. The authentication for
the request is provided by using a WS-Trust token previously issued
as part of a role request/response dialog. The request contains the
following elements:
o A complex rule set is requested where permission to is to be
granted to anyone who meets either of the two policies given.
o A specific recipient info structure is provided for a subject
who's name is 'lisa@simpsons.com'. The details of the recipient
info structure are skipped but it would be any encoding of a
RecipientInfo structure from CMS.
o A generic key encryption key is provided for any other subject who
meets the policies specified.
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<?xml version="1.0" encoding="UTF-8"?>
<PlasmaRequest xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:schema:plasma:1.0 C:\ietf\drafts\Schema\Plasma.xsd"
xmlns="urn:ietf:schema:plasma:1.0"
xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17">
<Authentication>
<WS_Token>123456</WS_Token>
</Authentication>
<xacml:Request CombinedDecision="false" ReturnPolicyIdList="false">
<xacml:Attributes Category="urn:oasis:names:tc:xaml:3.0:attribute-catagory:action">
<xacml:Attribute IncludeInResult="false" AttributeId="urn:plasma:action-id">
<xacml:AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">GetCMSToken</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
<xacml:Attributes Category="urn:ietf:plasma:attribute-category:data">
<xacml:Attribute AttributeId="urn:plasma:data-id" IncludeInResult="false">
<xacml:AttributeValue DataType="xml">
<MessageTokenRequest>
<Label CombiningRule="or">
<Leaf Label="urn:example:policies:confidential"/>
<Leaf Label="urn:example:policies:plasma"/>
</Label>
<RecipientInfo>
<Subject type="urn:oasis:names:tc:xacml:1.0:data-type:rfc822Name">
lisa@simpsons.com
</Subject>
<LockBox>FF33eeddccaa002234</LockBox>
</RecipientInfo>
<KEK>AB123456</KEK>
</MessageTokenRequest>
</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
</xacml:Request>
</PlasmaRequest>
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Appendix E. Example: Get CMS Token Response
This section contains an example of a response from a server to a
client for a CMS message token to be issued. The token is returned
in the CMSToken element. This element would then be placed into the
CMS message being created by the client.
<?xml version="1.0" encoding="UTF-8"?>
<PlasmaResponse xmlns="urn:ietf:schema:plasma:1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:schema:plasma:1.0 C:\ietf\drafts\Schema\Plasma.xsd"
xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17">
<xacml:Response>
<xacml:Result>
<xacml:Decision>Permit</xacml:Decision>
</xacml:Result>
</xacml:Response>
<CMSToken>3425342352343243</CMSToken>
</PlasmaResponse>
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Appendix F. Example: Get CMS Key Request
<?xml version="1.0" encoding="UTF-8"?>
<PlasmaRequest xmlns="urn:ietf:schema:plasma:1.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:schema:plasma:1.0 C:\ietf\drafts\Schema\Plasma.xsd"
xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17">
<Authentication>
<SAML_Collection>....</SAML_Collection>
</Authentication>
<xacml:Request CombinedDecision="false" ReturnPolicyIdList="false">
<xacml:Attributes Category="urn:oasis:names:tc:xacml:3.0:attribute-catagory:action">
<xacml:Attribute AttributeId="urn:plasma:action-id" IncludeInResult="false">
<xacml:AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">ParseCMSToken</xacml:AttributeValue>
</xacml:Attribute>
<xacml:Attribute AttributeId="urn:plasma:action-id" IncludeInResult="false">
<xacml:AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">GetReplyToken</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
<xacml:Attributes Category="urn:ietf:plasma:attribute-category:data">
<xacml:Attribute AttributeId="urn:plasma:data-id" IncludeInResult="false">
<xacml:AttributeValue DataType="http://www.w3.org/2001/XMLSchema#hexBinary">AABBDDEEFF1122344</xacml:AttributeValue>
</xacml:Attribute>
</xacml:Attributes>
</xacml:Request>
</PlasmaRequest>
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Appendix G. Example: Get CMS KeyResponse
<?xml version="1.0" encoding="UTF-8"?>
<PlasmaResponse xmlns="urn:ietf:schema:plasma:1.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="urn:ietf:schema:plasma:1.0 C:\ietf\drafts\Schema\Plasma.xsd"
xmlns:xacml="urn:oasis:names:tc:xacml:3.0:core:schema:wd-17"
xmlns:wst="http://schemas.xmlsoap.org/ws/2005/02/trust"
xmlns:wsu="http://docs.oasis-open.org/wss/2004/01/oasis-200401-wss-wssecurity-utility-1.0.xsd">
<xacml:Response>
<xacml:Result>
<xacml:Decision>Permit</xacml:Decision>
</xacml:Result>
</xacml:Response>
<CMSKey>
<DisplayString>Company Confidential</DisplayString>
<KEK>3425342352343243</KEK>
<PlasmaToken>
<PDP>https://pdp.example.com/companyPolicies</PDP>
<Label CombiningRule="or">
<Leaf Label="urn:example:policies:confidential"/>
<Leaf Label="urn:example:policies:plasma"/>
</Label>
<wst:RequestSecurityTokenResponse>
<wst:TokenType>urn:plasma:roleToken</wst:TokenType>
<wst:RequestedSecurityToken>....</wst:RequestedSecurityToken>
<wst:Lifetime><wsu:Expires>2012-02-01T00:00:00</wsu:Expires></wst:Lifetime>
</wst:RequestSecurityTokenResponse>
</PlasmaToken>
</CMSKey>
</PlasmaResponse>
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Author's Address
Jim Schaad
Soaring Hawk Consulting
Email: ietf@augustcellars.com
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