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OES allows external applications to ask authorization questions using the XACML protocol. This capability is supported only in the Web Services SSM.
The XACML service is implemented as an extension to the existing Authorization Service in the Web Service SSM and uses the same configuration and administration scripts of the Web Service SSM. The XACML service is silently installed together with the Web Service SSM. The XACML service is not viewable or configurable through the Administration Console.
Note: | The XACML service supports XACML 2.0 only. |
The basic use case for the XACML service is similar to the following:
OES includes a simple XACML client (PEP) application that does authorization to the Web Service SSM using the XACML protocol. The example demonstrates the following concepts:
The example is located in BEA_HOME\ales32-ssm\webservice-ssm\examples\XACMLClient
.
XACML is an OASIS standard language that specifies schemas for authorization policies and for authorization decision requests and responses. It also specifies how to evaluate policies against requests to compute a response. In this release, OES implements the authorization process using XACML context. The XACML context is used to convey an authorization decision request and response.
The XACML standard ( http://docs.oasis-open.org/xacml/2.0/access_control-xacml-2.0-core-spec-os.pdf) specifies how the XACML context should be used for authorization, and the behaviors of PEPs and PDPs.
The XACML context is the protocol used by the PEP to ask the PDP for an authorization decision. It defines a <xacml-context:Request>
element to convey the request and a <xacml-context:Response>
for the response. The request contains four elements for authorization, including:
— Subject
— Action
— Resource
— Environment
The PEP sends the authorization request to the PDP using a XACML context, which contains the subject, action, resource, and environment. The PEP is asking the PDP the following question: “Given such a subject, is it allowed to perform the specified action on the specified resource in the specified environment?”.
— Decision
— Status
— Obligations
The XACML service takes the XACML request, converts the request to a format understood by OES, and calls the Java API (specifically, the Authorization Service’s isAccessAllowed method) to authorize the user.
When a decision has been made, the XACML service wraps the returned values into the XACML response. The XACML service returns a SOAP fault if the PEP sends a malformed request that does not follow the XACML context schema. Otherwise, the XACML service will always return a decision of “Permit”, “Deny”, “Indeterminate” or “NotApplicable”.
The PEP then interprets the result and enforces the decision. For the “Permit” decision, the PEP allows the request, and for the “Deny” decision, the PEP denies the request. For results of “Indeterminate” or “NotApplicable,” it is up to the PEP to interpret them. For “Permit-biased” PEP, the access will be allowed; for “Deny-biased” PEP, access will be denied.
The policy enforcement point (PEP) that sends the authorization request to the XACML service is responsible for authenticating the user and supplying a valid OES token as the subject.
The following types of identity assertion tokens are supported:
The Extensible Markup Language (XML) structures used by the Authentication Service for transmitting identity assertion tokens and other credential types are defined the WSDL interface.
The XACML service accepts the token supplied by the PEP and tries to assert that token (assertion) in OES.
As described in XACML Context, the request contains an <xacml-context:Request>
and the response contains an <xacml-context:Response>
element. These two elements are directly enclosed in the SOAP body.
One, and only one, request or response should be in the SOAP body.
There are currently two defined XACML namespaces. Policies are defined using the identifier urn:oasis:names:tc:xacml:2.0:policy:schema:os
, and request and response contexts are defined using the identifier urn:oasis:names:tc:xacml:2.0:context:schema:os
.
This implementation uses the following identifier to represent the XACML service:http://security.bea.com/ssmws/ssm-ws-1.0.wsdl
.
Listing 6-1 shows a sample SOAP request.
POST /XACMLAuthorization HTTP/1.0
Host: pdp-01
Connection: Keep-Alive
Content-Type: application/soap+xml; charset=utf-8
SOAPAction: ssmws:xacml:authorization
<?xml version="1.0"?>
<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
<soap:Body>
<xacml-context:Request xmlns:xacml-context="urn:oasis:names:tc:xacml:2.0:context:schema:os">
<xacml-context:Subject>…</xacml-context:Subject>
<xacml-context:Resource>…</xacml-context:Resource>
<xacml-context:Action>…</xacml-context:Action>
<xacml-context:Environment>…</xacml-context:Environment>
</xacml-context:Request>
</soap:Body>
</soap:Envelope>
If a malformed SOAP request is sent to the server (for example, a non-XML request or an XML request that does not follow the schema definition), a SOAP fault is returned to the client (PEP).
The request element defined by the XACML standard ( http://docs.oasis-open.org/xacml/2.0/access_control-xacml-2.0-core-spec-os.pdf) is as follows:
<xs:element name="Request" type="xacml-context:RequestType"/>
<xs:complexType name="RequestType">
<xs:sequence>
<xs:element ref="xacml-context:Subject" maxOccurs="unbounded"/>
<xs:element ref="xacml-context:Resource" maxOccurs="unbounded"/>
<xs:element ref="xacml-context:Action"/>
<xs:element ref="xacml-context:Environment"/>
</xs:sequence>
</xs:complexType>
As detailed in the standard, the <Request>
element contains <Subject>
, <Resource>
, <Action>
and <Environment>
elements. There may be multiple <Subject>
elements and, under some conditions, multiple <Resource>
elements. Each child element contains a sequence of <xacml-context:Attribute>
elements associated with the subject, resource, action, and environment, respectively.
The sections that follow describe how the <Subject>
, <Resource>
, <Action>
and <Environment>
elements are interpreted.
XACML subject, resource, action, and environment elements usually contain XACML context attributes, <xacml-context:Attribute>
.
The context attributes contain metadata (such as AttributeId
, DataType
), and one or more <AttributeValue>
element. As described in the XACML standard (
http://docs.oasis-open.org/xacml/2.0/access_control-xacml-2.0-core-spec-os.pdf), the schema of Attribute is as follows:
<xs:element name="Attribute" type="xacml-context:AttributeType"/>
<xs:complexType name="AttributeType">
<xs:sequence>
<xs:element ref="xacml-context:AttributeValue" maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
<xs:attribute name="DataType" type="xs:anyURI" use="required"/>
<xs:attribute name="Issuer" type="xs:string" use="optional"/>
</xs:complexType>
Different attributes in different elements will have different AttributeId and DataType.
The <AttributeValue>
, by definition, can carry anything. It contains any element under any namespace, as well as any attributes. Any valid XML data can be put in. However, it must be meaningful for its parent <Attribute>
’s AttributeId
and DataType
.
There can be multiple <AttributeValue>
elements in an <Attribute>
; however, the XACML service allows only one of them. If there is more than one, an indeterminate result is returned and a processing-error status is reported.
An <Attribute>
without an <AttributeValue>
results in a SOAP fault because it does not follow the schema.
If there is an Issuer
attribute in <Attribute>
, it is currently ignored by the XACML service.
The DataType
of the <Attribute>
is usually ignored, because the content of the <AttributeValue>
is regarded only as a string type.
The <Subject>
consists of a sequence of <xacml-context:Attribute>
elements associated with the subject.
<xs:element name="Subject" type="xacml-context:SubjectType"/>
<xs:complexType name="SubjectType">
<xs:sequence>
<xs:element ref="xacml-context:Attribute" minOccurs="0"maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="SubjectCategory" type="xs:anyURI"
default="urn:oasis:names:tc:xacml:1.0:subject-category:access-subject"/>
</xs:complexType>
The <Subject>
element has an optional attribute, SubjectCategory
. This represents the subject’s role of this request. For example, ‘access-subject
’, ‘requesting-machine
’, ‘code-base
’.
Inside a <Subject>
, there could be an <Attribute>
with AttributeId
of “urn:oasis:names:tc:xacml:1.0:subject-category
”, and the <AttributeValue>
of this <Attribute>
also represents the subject category. This is equal to the “SubjectCategory
” attribute of the <Subject>
.
For example, the following two <Subject>
elements are functionally equal:
<Subject>
<Attribute AttributeId="urn:oasis:names:tc:xacml:2.0:subject-category" DataType="xs:anyURI">
<AttributeValue>urn:oasis:names:tc:xacml:1.0:subject-category:access-subject</AttributeValue>
</Attribute>
</Subject>
<Subject SubjectCategory=”urn:oasis:names:tc:xacml:1.0:subject-category:access-subject”>
</Subject>
There can be multiple subjects in a <Request>
element.
The XACML context specifies that these subjects should be "disjunctive," which is defined in the standard as a sequence of predicates combined using the logical ‘OR’ operation.
For example, one subject may represents the human user who initiates the request, another may represent the code that is doing the request. They are specified by subject categories.
The rules of handling multiple subjects are as follows:
<Subject>
element. <Subject>
having the “access-subjec
t” category, which represents the direct accessing subject. For the <Attribute>
elements of this category, there should be no more than one <Attribute>
element with the following AttributeId
, which represents the requester’s identity: urn:oasis:names:tc:xacml:1.0:subject:subject-id
.<Attribute>
is described in Subject Id <Attribute>.<Subject>
elements or other <Attribute>
elements that are not a subject-id, they are converted as an OES authorization context (AppContext).
The DataType
attribute of the subject-id <Attribute>
element indicates the subject type. The type is of “anyURI
” type, but in order to be understood, the DataType
should be prefixed with the
identifier that represents the XACML service: http://security.bea.com/ssmws/ssm-ws-1.0.wsdl
.
In addition, a fragment should be suffixed after this URL indicating the subject type that could be asserted in OES; that is, the first parameter of the assertIdentity()
method in the Authentication service API.
For example, if the subject contains ALESIdentityAssertion, it should have the DataType http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#ALESIdentityAssertion
, and the <AttributeValue>
of this <Attribute>
is taken as the subject.
However, if a valid <AttributeValue>
is provided and correctly recognized by the Web Service SSM, the DataType may not be checked.
If the <Subject>
(which is of ‘access-subject’ category) does not contain an <Attribute>
with “subject-id”, this subject will be considered as an anonymous user. The service will construct an anonymous identity and pass it to the authorization service.
Also note that this implementation reuses the Web Service SSM’s identity cache for better performance, as described in Optimizing Web Services Performance with Caches.
For other <Subject>
elements and <Attribute> elements that are not in the ‘access-subject’ category, or are in the ‘access-subject’ category but without a “subject-id” id, those <Attribute>
elements are converted as authorization context (AppContext) of OES.
If there are multiple <Attribute>
elements with the same id, a later one will override the previous one.
Also, only text values in <AttributeValue>
are acceptable; child XML elements are ignored.
The rule for converting an attribute to a context key-value pair is as follows:
urn:oasis:names:tc:xacml:1.0: subject:authn-locality:authentication-method
”), the last field of the URN, that is, the string after the last colon, is taken as the context key, and the AttributeValue is the context value. For example, if the previous URN has an AttributeValue of “username/password”, the resulting OES context will be “authentication-method” : “username/password”.Note that this is a XACML extension: the XACML standard does not have this type of URL as AttributeId, but the PEP could use this method to pass some context to the OES system.
At least one of the resource attributes should have the following AttributeId: urn:oasis:names:tc:xacml:2.0:resource:resource-id
.
The AttributeValue of this resource attribute should be the resource that can be understood by OES; that is, the resource under the binding point of the SSM. The example queries the user for the resource name, and suggests a value of "store/book."
The DataType of this attribute should always be the XML schema standard “string” type: http://www.w3.org/2001/XMLSchema#string
.
Other attributes in <Resource>, except for the one associated with the naming authority, are converted as authorization context attributes for authorization evaluation in OES, using the same rule as <Subject> attributes.
At least one of the attributes in the <Action> element must have the following AttributeId: urn:oasis:names:tc:xacml:1.0:action:action-id
.
The attribute value of this attribute is the action performed on the resource. For example: GET, POST. The example queries the user for the action name.
The DataType of this attribute should be the XML schema standard string http://www.w3.org/2001/XMLSchema#string
.
Other attributes in <Action>
are converted as context attributes for authorization evaluation in OES, using the same rule as <Subject>
attributes.
The XACML service converts environment attributes to OES application context. The rule to convert environment elements to OES contexts is the same as for the subject. All attributes in <Environment>
elements are converted.
For example, a sample environment element is as follows:
<Environment>
<Attribute AttributeId="http://security.bea.com/ssmws/ssm-ws-1.0.wsdl
#DOB" DataType="http://www.w3.org/2001/XMLSchema#dateTime">
<AttributeValue>1979-03-29</AttributeValue>
</Attribute>
</Environment>
The fragment (the string after the ‘#’ character) of the URL is taken as the context key and the AttributeValue is the context value, which results in an OES context of DOB:1979-03-29
.
Listing 6-2 shows a full sample of a XACML request, without the SOAP envelope.
<Request xmlns="urn:oasis:names:tc:xacml:2.0:context:schema:os">
<Subject>
<Attribute <AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id"
<DataType=" http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#
<ALESIdentityAssertion">
<AttributeValue>
<ALESIdentityAssertion xmlns=”…”>……</ALESIdentityAssertion>
</AttributeValue>
</Attribute>
</Subject>
<Resource>
<Attribute AttributeId="urn:oasis:names:tc:xacml:2.0:resource:resource-id"
DataType="http://www.w3.org/2001/XMLSchema#string">
<AttributeValue>/cgi-bin/j_security_check</AttributeValue>
</Attribute>
</Resource>
<Action>
<Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:action:action-id"
DataType="http://www.w3.org/2001/XMLSchema#string">
<AttributeValue>POST</AttributeValue>
</Attribute>
</Action>
<Environment/>
</Request>
The <Response>
element is the root element of a response. It contains one or more <Result>
elements, which contain authorization decision results. The XACML service supports only one <Result> element.
The <Result> element is defined as follows:
<xs:element name="Result" type="xacml-context:ResultType"/>
<xs:complexType name="ResultType">
<xs:sequence>
<xs:element ref="xacml-context:Decision"/>
<xs:element ref="xacml-context:Status" minOccurs="0"/>
<xs:element ref="xacml:Obligations" minOccurs="0"/>
</xs:sequence>
<xs:attribute name="ResourceId" type="xs:string" use="optional"/>
</xs:complexType>
The <Result> element has a ResourceId attribute that indicates the identifier of the request resource element. This implementation does not use this value.
Decision is the evaluation result. It contains a string value of “Permit”, “Deny”, “Indeterminate”, or “NotApplicable”. “Permit” or “Deny” are typically returned. For example: <Decision>Permit</Decision>.
If some required attribute is required, “Indeterminate” is returned, with the “missing-attribute” status.
The <Status> element is an optional element of <Result>. It contains the following elements:
<StatusCode> has an attribute named “Value,” which can be one of the following values:
— urn:oasis:names:tc:xacml:1.0:status:ok
— urn:oasis:names:tc:xacml:1.0:status:missing-attribute
— urn:oasis:names:tc:xacml:1.0:status:syntax-error
— urn:oasis:names:tc:xacml:1.0:status:processing-error
If any exception occurred during the authorization process, processing-error is returned.
If some attribute is required for evaluating the policy, missing-attribute is returned.
“syntax-error” is never returned.
<StatusMessage> is simply a string to show the message accompanying the status. If an exception occurs, the exception will be in the <StatusMessage> for information purpose.
<StatusDetail> is an extension point and it can contain anything. This implementation puts a <MissingAttributeDetail> value in it if the status is “missing-attribute”. In that case, the AttributeId is the missing attribute key, prefixed with the XACML service namespace (http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#
) and there is no <AttributeValue>
in the <MissingAttributeDetail>
element.
A XACML obligation is an operation specified in a policy or policy set that should be performed by the PEP in conjunction with the enforcement of an authorization decision.
This implementation places the returned evaluation values, such as roles or the report_as values, in an obligation. Obligations are used only when the authorization result is “Permit.”
<xs:element name="Obligations" type="xacml:ObligationsType"/>
<xs:complexType name="ObligationsType">
<xs:sequence>
<xs:element ref="xacml:Obligation" maxOccurs="unbounded"/>
</xs:sequence>
</xs:complexType>
<xs:element name="Obligation" type="xacml:ObligationType"/>
<xs:complexType name="ObligationType">
<xs:sequence>
<xs:element ref="xacml:AttributeAssignment" minOccurs="0"
maxOccurs="unbounded"/>
</xs:sequence>
<xs:attribute name="ObligationId" type="xs:anyURI" use="required"/>
<xs:attribute name="FulfillOn" type="xacml:EffectType"use="required"/>
</xs:complexType>
<xs:element name="AttributeAssignment" type="xacml:AttributeAssignmentType"/>
<xs:complexType name="AttributeAssignmentType" mixed="true">
<xs:complexContent mixed="true">
<xs:extension base="xacml:AttributeValueType">
<xs:attribute name="AttributeId" type="xs:anyURI" use="required"/>
</xs:extension>
</xs:complexContent>
</xs:complexType>
Obligations consist of one or more <Obligation> elements. An <Obligation> has the following attributes:
The <Obligation>
element has zero or more <AttributeAssignment>
elements. <AttributeAssignment>
has an AttributeId and text content. The AttributeId is the returned attribute key, prefixed with the namespace http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#, and the content is the attribute value.
For example, the response attribute “currency” : ”USD” is returned as:
<AttributeAssignment AttributeId="http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#currency"
DataType="http://www.w3.org/2001/XMLSchema#string">USD
</AttributeAssignment>
<AttributeAssignment AttributeId="http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#role"
DataType="http://www.w3.org/2001/XMLSchema#string">Admin
</AttributeAssignment>
Listing 6-3 shows a complete sample response, without the SOAP envelope.
<?xml version="1.0" encoding="UTF-8"?>
<Response xmlns="urn:oasis:names:tc:xacml:2.0:context:schema:os">
<Result>
<Decision>Deny</Decision>
<Status>
<StatusCode Value="urn:oasis:names:tc:1.0:status:processing-error"/>
<StatusMessage>Authentication required</StatusMessage>
</Status>
<Obligations>
<Obligation FulfillOn="Permit" <ObligationId="http://security.be.com/ssmws/ssm-ws-1.0.wsdl#Roles">
<AttributeAssignment DataType="http://www.w3.org/2001/XMLSchema#string" AttributeId="http://security.bea.com/ssmws/ssm-ws-1.0.wsdl#role">Admin
</AttributeAssignment>
</Obligation>
</Obligations>
</Result>
</Response>
Listing 6-4 shows the WSDL definition of the XACML Service.
<?xml version="1.0" encoding="UTF-8"?>
<definitions
xmlns="http://schemas.xmlsoap.org/wsdl/"
xmlns:xs="http://www.w3.org/2001/XMLSchema"
xmlns:soap="http://schemas.xmlsoap.org/wsdl/soap/"
xmlns:xacml-context="urn:oasis:names:tc:xacml:2.0:context:schema:os"
xmlns:ssm="http://security.bea.com/ssmws/ssm-soap-types-1.0.xsd"
xmlns:tns="http://security.bea.com/ssmws/ssm-ws-1.0.wsdl"
targetNamespace="http://security.bea.com/ssmws/ssm-ws-1.0.wsdl">
<types>
<!-- note this policy schema is stripped for the XACML runtime only -->
<xs:import namespace="urn:oasis:names:tc:xacml:2.0:policy:schema:os" schemaLocation="access_control-xacml-2.0-policy-schema-os.xsd"/>
<xs:import namespace="urn:oasis:names:tc:xacml:2.0:context:schema:os" schemaLocation="access_control-xacml-2.0-context-schema-os.xsd"/>
<!-- for fault types -->
<xs:import namespace="http://security.bea.com/ssmws/ssm-soap-types-1.0.xsd" schemaLocation="ssm-soap-types.xsd"/>
</types>
<message name="XACMLAtzDecisionRequest">
<part name="param" element="xacml-context:Request"/>
</message>
<message name="XACMLAtzDecisionResponse">
<part name="param" element="xacml-context:Response"/>
</message>
<message name="XACMLFault">
<part name="fault" element="ssm:xacmlFailure"/>
</message>
<message name="serviceFault">
<part name="fault" element="ssm:serviceFailure"/>
</message>
<portType name="XACMLPort">
<operation name="authorize">
<input message="tns:XACMLAtzDecisionRequest"/>
<output message="tns:XACMLAtzDecisionResponse"/>
<fault name="serviceFault" message="tns:serviceFault" />
<fault name="xacmlFault" message="tns:XACMLFault"/>
</operation>
</portType>
<binding name="XACMLBinding" type="tns:XACMLPort">
<soap:binding style="document" transport="http://schemas.xmlsoap.org/soap/http"/>
<!-- Axis has problem support this style, use document instead. -->
<operation name="authorize">
<soap:operation soapAction="ssmws:xacml:authorization" style="document"/>
<input>
<soap:body use="literal"/>
</input>
<output>
<soap:body use="literal"/>
</output>
<fault name="serviceFault">
<soap:fault use="literal"/>
</fault>
<fault name="xacmlFault">
<soap:fault use="literal"/>
</fault>
</operation>
</binding>
<service name="XACMLService">
<port name="XACMLAuthorization" binding="tns:XACMLBinding">
<soap:address location="http://localhost/XACMLAuthorization"/>
</port>
</service>
</definitions>
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