staticpolicyfindermodule.java

sunxacml源码

/*
 * @(#)StaticPolicyFinderModule.java
 *
 * Copyright 2006 Sun Microsystems, Inc. All Rights Reserved.
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 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 * 
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
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package com.sun.xacml.support.finder;

import com.sun.xacml.AbstractPolicy;
import com.sun.xacml.EvaluationCtx;
import com.sun.xacml.ParsingException;
import com.sun.xacml.UnknownIdentifierException;

import com.sun.xacml.combine.CombiningAlgFactory;
import com.sun.xacml.combine.PolicyCombiningAlgorithm;

import com.sun.xacml.finder.PolicyFinder;
import com.sun.xacml.finder.PolicyFinderModule;
import com.sun.xacml.finder.PolicyFinderResult;

import java.io.File;

import java.net.MalformedURLException;
import java.net.URI;
import java.net.URISyntaxException;
import java.net.URL;

import java.util.Iterator;
import java.util.List;

import java.util.logging.Level;
import java.util.logging.Logger;


/**
 * This is a simple implementation of <code>PolicyFinderModule</code> that
 * supports retrieval based on context, and is designed for use with a
 * run-time configuration. Its constructor accepts a <code>List</code> of
 * <code>String</code>s that represent URLs or files, and these are resolved
 * to policies when the module is initialized. Beyond this, there is no
 * modifying or re-loading the policies represented by this class. This
 * class will optionally wrap multiple applicable policies into a dynamic
 * PolicySet.
 * <p>
 * Note that this class is designed to complement
 * <code>StaticRefPolicyFinderModule</code>. It would be easy to support both
 * kinds of policy retrieval in a single class, but the functionality is
 * instead split between two classes. The reason is that when you define a
 * configuration for your PDP, it's easier to specify the two sets of policies
 * by using two different finder modules. Typically, there aren't many
 * policies that exist in both sets, so loading the sets separately isn't
 * a problem. If this is a concern to you, simply create your own class and
 * merge the two existing classes.
 * <p>
 * This module is provided as an example, but is still fully functional, and
 * should be useful for many simple applications. This is provided in the
 * <code>support</code> package rather than the core codebase because it
 * implements non-standard behavior.
 *
 * @since 2.0
 * @author Seth Proctor
 */
public class StaticPolicyFinderModule extends PolicyFinderModule
{

    // the list of policy URLs passed to the constructor
    private List policyList;

    // the map of policies
    private PolicyCollection policies;

    // the optional schema file
    private File schemaFile = null;

    // the policy identifier for any policy sets we dynamically create
    private static final String POLICY_ID =
        "urn:com:sun:xacml:support:finder:dynamic-policy-set";
    private static URI policyId = null;

    // the logger we'll use for all messages
    private static final Logger logger =
        Logger.getLogger(StaticPolicyFinderModule.class.getName());

    static {
        try {
            policyId = new URI(POLICY_ID);
        } catch (Exception e) {
            // this can't actually happen, but just in case...
            if (logger.isLoggable(Level.SEVERE))
                logger.log(Level.SEVERE, "couldn't assign default policy id");
        }
    };

    /**
     * Creates a <code>StaticPolicyFinderModule</code> that provides
     * access to the given collection of policies and returns an error when
     * more than one policy matches a given context. Any policy that cannot
     * be loaded will be noted in the log, but will not cause an error. The
     * schema file used to validate policies is defined by the property
     * <code>PolicyReader.POLICY_SCHEMA_PROPERTY</code>. If the retrieved
     * property is null, then no schema validation will occur.
     *
     * @param policyList a <code>List</code> of <code>String</code>s that
     *                   represent URLs or files pointing to XACML policies
     */
    public StaticPolicyFinderModule(List policyList) {
        this.policyList = policyList;
        this.policies = new PolicyCollection();

        String schemaName =
            System.getProperty(PolicyReader.POLICY_SCHEMA_PROPERTY);
        if (schemaName != null)
            schemaFile = new File(schemaName);
    }

    /**
     * Creates a <code>StaticPolicyFinderModule</code> that provides
     * access to the given collection of policies and returns an error when
     * more than one policy matches a given context. Any policy that cannot
     * be loaded will be noted in the log, but will not cause an error.
     *
     * @param policyList a <code>List</code> of <code>String</code>s that
     *                   represent URLs or files pointing to XACML policies
     * @param schemaFile the schema file to validate policies against,
     *                   or null if schema validation is not desired
     */
    public StaticPolicyFinderModule(List policyList, String schemaFile) {
        this.policyList = policyList;
        this.policies = new PolicyCollection();

        if (schemaFile != null)
            this.schemaFile = new File(schemaFile);
    }

    /**
     * Creates a <code>StaticPolicyFinderModule</code> that provides
     * access to the given collection of policies. The given combining
     * algorithm is used to create new PolicySets when more than one
     * policy applies. Any policy that cannot be loaded will be noted in
     * the log, but will not cause an error. The schema file used to
     * validate policies is defined by the property
     * <code>PolicyReader.POLICY_SCHEMA_PROPERTY</code>. If the retrieved
     * property is null, then no schema validation will occur.
     *
     * @param combiningAlg the algorithm to use in a new PolicySet when more
     *                     than one policy applies
     * @param policyList a <code>List</code> of <code>String</code>s that
     *                   represent URLs or files pointing to XACML policies
     *
     * @throws URISyntaxException if the combining algorithm is not a
     *                            well-formed URI
     * @throws UnknownIdentifierException if the combining algorithm identifier
     *                                    isn't known
     */
    public StaticPolicyFinderModule(String combiningAlg, List policyList)
        throws URISyntaxException, UnknownIdentifierException
    {
        PolicyCombiningAlgorithm alg = (PolicyCombiningAlgorithm)
            (CombiningAlgFactory.getInstance().
             createAlgorithm(new URI(combiningAlg)));

        this.policyList = policyList;
        this.policies = new PolicyCollection(alg, policyId);

        String schemaName =
            System.getProperty(PolicyReader.POLICY_SCHEMA_PROPERTY);
        if (schemaName != null)
            schemaFile = new File(schemaName);
    }

    /**
     * Creates a <code>StaticPolicyFinderModule</code> that provides
     * access to the given collection of policies. The given combining
     * algorithm is used to create new PolicySets when more than one
     * policy applies. Any policy that cannot be loaded will be noted in
     * the log, but will not cause an error.
     *
     * @param combiningAlg the algorithm to use in a new PolicySet when more
     *                     than one policy applies
     * @param policyList a <code>List</code> of <code>String</code>s that
     *                   represent URLs or files pointing to XACML policies
     * @param schemaFile the schema file to validate policies against,
     *                   or null if schema validation is not desired
     *
     * @throws URISyntaxException if the combining algorithm is not a
     *                            well-formed URI
     * @throws UnknownIdentifierException if the combining algorithm identifier
     *                                    isn't known
     */
    public StaticPolicyFinderModule(String combiningAlg, List policyList,
                                    String schemaFile)
        throws URISyntaxException, UnknownIdentifierException
    {
        PolicyCombiningAlgorithm alg = (PolicyCombiningAlgorithm)
            (CombiningAlgFactory.getInstance().
             createAlgorithm(new URI(combiningAlg)));

        this.policyList = policyList;
        this.policies = new PolicyCollection(alg, policyId);
        
        if (schemaFile != null)
            this.schemaFile = new File(schemaFile);
    }

    /**
     * Always returns <code>true</code> since this module does support
     * finding policies based on context.
     *
     * @return true
     */
    public boolean isRequestSupported() {
        return true;
    }

    /**
     * Initialize this module. Typically this is called by
     * <code>PolicyFinder</code> when a PDP is created. This method is
     * where the policies are actually loaded.
     *
     * @param finder the <code>PolicyFinder</code> using this module
     */
    public void init(PolicyFinder finder) {
        // now that we have the PolicyFinder, we can load the policies
        PolicyReader reader = new PolicyReader(finder, logger, schemaFile);

        Iterator it = policyList.iterator();
        while (it.hasNext()) {
            String str = (String)(it.next());
            AbstractPolicy policy = null;

            try {
                try {
                    // first try to load it as a URL
                    URL url = new URL(str);
                    policy = reader.readPolicy(url);
                } catch (MalformedURLException murle) {
                    // assume that this is a filename, and try again
                    policy = reader.readPolicy(new File(str));
                }

                // we loaded the policy, so try putting it in the collection
                if (! policies.addPolicy(policy))
                    if (logger.isLoggable(Level.WARNING))
                        logger.log(Level.WARNING, "tried to load the same " +
                                   "policy multiple times: " + str);
            } catch (ParsingException pe) {
                if (logger.isLoggable(Level.WARNING))
                    logger.log(Level.WARNING, "Error reading policy: " + str,
                               pe);
            }
        }
    }

    /**
     * Finds a policy based on a request's context. If more than one policy
     * matches, then this either returns an error or a new policy wrapping
     * the multiple policies (depending on which constructor was used to
     * construct this instance).
     *
     * @param context the representation of the request data
     *
     * @return the result of trying to find an applicable policy
     */
    public PolicyFinderResult findPolicy(EvaluationCtx context) {
        try {
            AbstractPolicy policy = policies.getPolicy(context);

            if (policy == null)
                return new PolicyFinderResult();
            else
                return new PolicyFinderResult(policy);
        } catch (TopLevelPolicyException tlpe) {
            return new PolicyFinderResult(tlpe.getStatus());
        }
    }

}