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/*
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* This program is a part of the IoTa Project.
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*
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* Copyright © 2011-2012 Université de Caen Basse-Normandie, GREYC
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* Copyright © 2011 Orange Labs
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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* <http://www.gnu.org/licenses/>
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*
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* See AUTHORS for a list of contributors.
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*/
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package fr.unicaen.iota.xacml.combine;
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import com.sun.xacml.EvaluationCtx;
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import com.sun.xacml.Rule;
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import com.sun.xacml.combine.RuleCombinerElement;
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import com.sun.xacml.combine.RuleCombiningAlgorithm;
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import com.sun.xacml.ctx.Result;
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import java.net.URI;
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import java.net.URISyntaxException;
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import java.util.Iterator;
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import java.util.List;
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/**
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* This is the standard SC Group rule combining algorithm. It allows a single
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* evaluation of not applicable or indeterminate results to take precedence over
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* any number of permit, deny. The result will be Deny.
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*/
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public class SCGroupRuleAcceptAlg extends RuleCombiningAlgorithm {
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/**
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* The standard URN used to identify this algorithm
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*/
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public static final String algId =
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"urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:"
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+ "sc-rule-accept-group";
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// a URI form of the identifier
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private static URI identifierURI;
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// exception if the URI was invalid, which should never be a problem
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private static RuntimeException earlyException;
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static {
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try {
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identifierURI = new URI(algId);
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} catch (URISyntaxException se) {
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earlyException = new IllegalArgumentException();
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earlyException.initCause(se);
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}
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}
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@Override
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public URI getIdentifier() {
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return identifierURI;
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}
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/**
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* Standard constructor.
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*/
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public SCGroupRuleAcceptAlg() {
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super(identifierURI);
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if (earlyException != null) {
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throw earlyException;
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}
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}
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/**
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* Protected constructor used by the ordered version of this algorithm.
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*
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* @param identifier the algorithm's identifier
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*/
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public SCGroupRuleAcceptAlg(URI identifier) {
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super(identifier);
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}
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/**
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* Applies the combining rule to the set of rules based on the evaluation
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* context.
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*
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* @param context the context from the request
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* @param parameters a (possibly empty) non-null
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* <code>List</code> of
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* <code>CombinerParameter<code>s
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* @param ruleElements the rules to combine
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*
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* @return the result of running the combining algorithm
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*/
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@Override
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public Result combine(EvaluationCtx context, List parameters, List ruleElements) {
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boolean atLeastOneError = false;
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boolean potentialDeny = false;
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boolean atLeastOnePermit = false;
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Result firstIndeterminateResult = null;
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Iterator it = ruleElements.iterator();
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while (it.hasNext()) {
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Rule rule = ((RuleCombinerElement) (it.next())).getRule();
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Result result = rule.evaluate(context);
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int value = result.getDecision();
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// if there was a value of DENY, then regardless of what else
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// we've seen, we always return DENY
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if (value == Result.DECISION_DENY || value == Result.DECISION_NOT_APPLICABLE) {
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return result;
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}
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// if it was INDETERMINATE, then we couldn't figure something
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// out, so we keep track of these cases...
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if (value == Result.DECISION_INDETERMINATE) {
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atLeastOneError = true;
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// there are no rules about what to do if multiple cases
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// cause errors, so we'll just return the first one
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if (firstIndeterminateResult == null) {
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firstIndeterminateResult = result;
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}
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// if the Rule's effect is DENY, then we can't let this
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// alg return PERMIT, since this Rule might have denied
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// if it could do its stuff
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if (rule.getEffect() == Result.DECISION_DENY) {
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potentialDeny = true;
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}
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} else {
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// keep track of whether we had at least one rule that
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// actually pertained to the request
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if (value == Result.DECISION_PERMIT) {
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atLeastOnePermit = true;
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}
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}
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}
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// we didn't explicitly DENY, but we might have had some Rule
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// been evaluated, so we have to return INDETERMINATE
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if (potentialDeny) {
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return firstIndeterminateResult;
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}
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// some Rule said PERMIT, so since nothing could have denied,
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// we return PERMIT
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if (atLeastOnePermit) {
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return new Result(Result.DECISION_PERMIT,
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context.getResourceId().encode());
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}
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// we didn't find anything that said PERMIT, but if we had a
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// problem with one of the Rules, then we're INDETERMINATE
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if (atLeastOneError) {
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return firstIndeterminateResult;
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}
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// if we hit this point, then none of the rules actually applied
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// to us, so we return NOT_APPLICABLE
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return new Result(Result.DECISION_NOT_APPLICABLE,
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context.getResourceId().encode());
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}
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}
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