Thursday, November 11, 2010

Guide to write XACML policies in WSO2 Identity Server - Part - 3

This blog post is a follow up to the Guide to write XACML policies in WSO2 Identity Server - Part - 2.

This post addresses following authorization requirements.

1. The operation getCustomers in the service http://localhost:8280/services/Customers should only be accessed by the users belong to group admin_customers

2. The operation getEmployees in the service http://localhost:8280/services/Customers should only be accessed by the users belong to group admin_emps

3. Request to any other service or operation should fail
<?xml version="1.0" encoding="UTF-8"?>
<Policy PolicyId="urn:sample:xacml:2.0:samplepolicy"
  RuleCombiningAlgId="urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:first-applicable" xmlns="urn:oasis:names:tc:xacml:2.0:policy:schema:os">
  <Description>Sample XACML Authorization Policy</Description>
  <Target>
    <Subjects>
      <AnySubject/>
    </Subjects>
    <Actions>
      <AnyAction/>
    </Actions>
    <Resources>
      <AnyResource/>
    </Resources>
  </Target>
  <Rule Effect="Permit" RuleId="primary-group-customer-rule">
    <Target>
      <Subjects>
        <AnySubject/>
      </Subjects>
      <Resources>
        <Resource>
          <ResourceMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:string-regexp-match">
            <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">http://localhost:8280/services/Customers/getCustomers</AttributeValue>
            <ResourceAttributeDesignator
              AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-id" DataType="http://www.w3.org/2001/XMLSchema#string"/>
          </ResourceMatch>
        </Resource>
      </Resources>
      <Actions>
        <Action>
          <ActionMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:string-equal">
            <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">read</AttributeValue>
            <ActionAttributeDesignator
              AttributeId="urn:oasis:names:tc:xacml:1.0:action:action-id" DataType="http://www.w3.org/2001/XMLSchema#string"/>
          </ActionMatch>
        </Action>
      </Actions>
    </Target>
    <Condition>
      <Apply FunctionId="urn:oasis:names:tc:xacml:1.0:function:string-subset">
        <Apply FunctionId="urn:oasis:names:tc:xacml:1.0:function:string-bag">
          <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">admin_customers</AttributeValue>
        </Apply>
        <SubjectAttributeDesignator AttributeId="group" DataType="http://www.w3.org/2001/XMLSchema#string"/>
      </Apply>
    </Condition>
  </Rule>
  <Rule Effect="Permit" RuleId="primary-group-emps-rule">
    <Target>
      <Subjects>
        <AnySubject/>
      </Subjects>
      <Resources>
        <Resource>
          <ResourceMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:string-regexp-match">
            <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">http://localhost:8280/services/Customers/getEmployees</AttributeValue>
            <ResourceAttributeDesignator
              AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-id" DataType="http://www.w3.org/2001/XMLSchema#string"/>
          </ResourceMatch>
        </Resource>
      </Resources>
      <Actions>
        <Action>
          <ActionMatch MatchId="urn:oasis:names:tc:xacml:1.0:function:string-equal">
            <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">read</AttributeValue>
            <ActionAttributeDesignator
              AttributeId="urn:oasis:names:tc:xacml:1.0:action:action-id" DataType="http://www.w3.org/2001/XMLSchema#string"/>
          </ActionMatch>
        </Action>
      </Actions>
    </Target>
    <Condition>
      <Apply FunctionId="urn:oasis:names:tc:xacml:1.0:function:string-subset">
        <Apply FunctionId="urn:oasis:names:tc:xacml:1.0:function:string-bag">
          <AttributeValue DataType="http://www.w3.org/2001/XMLSchema#string">admin_emps</AttributeValue>
        </Apply>
        <SubjectAttributeDesignator AttributeId="group" DataType="http://www.w3.org/2001/XMLSchema#string"/>
      </Apply>
    </Condition>
  </Rule>
  <Rule Effect="Deny" RuleId="deny-rule"/>
</Policy>
Following are few valid requests which will result in "Permit/Not Applicable/Deny" once evaluated against the above policy.

XACML request - 1
Resource : http://localhost:8280/services/Customers/getCustomers
User : "admin" belongs only to "admin_customers" group
Result : Permit
<Request xmlns="urn:oasis:names:tc:xacml:2.0:context:schema:os"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <Subject>
  <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id"
   DataType="http://www.w3.org/2001/XMLSchema#string">
   <AttributeValue>admin</AttributeValue>
  </Attribute>
  <Attribute AttributeId="group"
   DataType="http://www.w3.org/2001/XMLSchema#string">
   <AttributeValue>admin_customers</AttributeValue>
  </Attribute>
 </Subject>
 <Resource>
  <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-id"
   DataType="http://www.w3.org/2001/XMLSchema#string">
   <AttributeValue>http://localhost:8280/services/Customers/getCustomers</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>read</AttributeValue>
  </Attribute>
 </Action>
 <Environment />
</Request> 

XACML request - 2
Resource : http://localhost:8280/services/Customers/getCustomers
User : "admin" belongs only to "admin_emps" group
Result : Deny
<Request xmlns="urn:oasis:names:tc:xacml:2.0:context:schema:os"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
 <Subject>
  <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:subject:subject-id"
   DataType="http://www.w3.org/2001/XMLSchema#string">
   <AttributeValue>admin</AttributeValue>
  </Attribute>
  <Attribute AttributeId="group"
   DataType="http://www.w3.org/2001/XMLSchema#string">
   <AttributeValue>admin_emps</AttributeValue>
  </Attribute>
 </Subject>
 <Resource>
  <Attribute AttributeId="urn:oasis:names:tc:xacml:1.0:resource:resource-id"
   DataType="http://www.w3.org/2001/XMLSchema#string">
   <AttributeValue>http://localhost:8280/services/Customers/getCustomers</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>read</AttributeValue>
  </Attribute>
 </Action>
 <Environment />
</Request> 

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