/*
* @(#)PolicyCollection.java
*
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package com.sun.xacml.support.finder;
import com.sun.xacml.AbstractPolicy;
import com.sun.xacml.EvaluationCtx;
import com.sun.xacml.MatchResult;
import com.sun.xacml.Policy;
import com.sun.xacml.PolicyMetaData;
import com.sun.xacml.PolicyReference;
import com.sun.xacml.PolicySet;
import com.sun.xacml.Target;
import com.sun.xacml.TargetMatch;
import com.sun.xacml.TargetSection;
import com.sun.xacml.VersionConstraints;
import com.sun.xacml.combine.PolicyCombiningAlgorithm;
import com.sun.xacml.ctx.Status;
import java.net.URI;
import java.util.ArrayList;
import java.util.Comparator;
import java.util.HashMap;
import java.util.Iterator;
import java.util.StringTokenizer;
import java.util.TreeSet;
/**
* This class handles collections of <code>AbstractPolicy</code> instances,
* and provides some commonly useful operations. Specifically, it lets you
* retrieve matching policies (based on reference or context), it optionally
* handles wrapping multiple matches under a single PolicySet, and it manages
* different versions of policies correctly. This class is intended for use
* as a backing store to <code>PolicyFinderModule</code>s, but in practice
* may have many uses.
* <p>
* Note that this class will accept multiple versions of the same policy. This
* means that when you retieve a policy by reference, you will get the
* correct version. It also means that when you retrieve a policy based on
* context, there may be multiple revisions of the same policy, any number
* of which may apply. Generally speaking, the correct behavior here is not
* to return all of these policies, since they are (virtually speaking) the
* same policy, but may have conflicting rules. So, as a simplification, and
* to handle the most common cases, only the most recent version of a policy
* is returned in these cases. If you need a more complex solution, you
* will need to implement it yourself. Because the support modules use this
* class as their backing store, this is true also of those modules.
* <p>
* Note that this is not a heavily optimized class. It is intended more as
* an example, support code for the finder modules, and a starting utility
* for other programmers than as an enterprise-quality implementation. That
* said, it is fully functional, and should be useful for many applications.
*
* @since 2.0
* @author Seth Proctor
*/
public class PolicyCollection
{
// the actual collection of policies
private HashMap policies;
// the single instance of the comparator we'll use for managing versions
private VersionComparator versionComparator = new VersionComparator();
// the optional combining algorithm used when wrapping multiple policies
private PolicyCombiningAlgorithm combiningAlg;
// the optional policy id used when wrapping multiple policies
private URI parentId;
// default target that matches anything, used in wrapping policies
private static final Target target;
/**
* This static initializer just sets up the default target, which is
* used by all wrapping policy sets.
*/
static {
target =
new Target(new TargetSection(null, TargetMatch.SUBJECT,
PolicyMetaData.XACML_VERSION_2_0),
new TargetSection(null, TargetMatch.RESOURCE,
PolicyMetaData.XACML_VERSION_2_0),
new TargetSection(null, TargetMatch.ACTION,
PolicyMetaData.XACML_VERSION_2_0),
new TargetSection(null, TargetMatch.ENVIRONMENT,
PolicyMetaData.XACML_VERSION_2_0));
};
/**
* Creates a new <code>PolicyCollection</code> that will return errors
* when multiple policies match for a given request.
*/
public PolicyCollection() {
policies = new HashMap();
combiningAlg = null;
}
/**
* Creates a new <code>PolicyCollection</code> that will create a new
* top-level PolicySet when multiple policies match for a given request.
*
* @param combiningAlg the algorithm to use in a new PolicySet when more
* than one policy applies
* @param parentPolicyId the identifier to use for the new PolicySet
*/
public PolicyCollection(PolicyCombiningAlgorithm combiningAlg,
URI parentPolicyId) {
policies = new HashMap();
this.combiningAlg = combiningAlg;
this.parentId = parentPolicyId;
}
/**
* Adds a new policy to the collection, and uses the policy's identifier
* as the reference identifier. If this identifier already exists in the
* collection, and this policy does not represent a new version of the
* policy, then the policy is not added.
*
* @param policy the policy to add
*
* @return true if the policy was added, false otherwise
*/
public boolean addPolicy(AbstractPolicy policy) {
return addPolicy(policy, policy.getId().toString());
}
/**
* Adds a new policy to the collection using the given identifier as
* the reference identifier. If this identifier already exists in the
* collection, and this policy does not represent a new version of the
* policy, then the policy is not added.
*
* @param policy the policy to add
* @param identifier the identifier to use when referencing this policy
*
* @return true if the policy was added, false otherwise
*/
public boolean addPolicy(AbstractPolicy policy, String identifier) {
if (policies.containsKey(identifier)) {
// this identifier is already is use, so see if this version is
// already in the set
TreeSet set = (TreeSet)(policies.get(identifier));
return set.add(policy);
} else {
// this identifier isn't already being used, so create a new
// set in the map for it, and add the policy
TreeSet set = new TreeSet(versionComparator);
policies.put(identifier, set);
return set.add(policy);
}
}
/**
* Attempts to retrieve a policy based on the given context. If multiple
* policies match then this will either throw an exception or wrap the
* policies under a new PolicySet (depending on how this instance was
* constructed). If no policies match, then this will return null. See
* the comment in the class header about how this behaves when multiple
* versions of the same policy exist.
*
* @param context representation of a request
*
* @return a matching policy, or null if no policy matches
*
* @throws TopLevelPolicyException if multiple policies match but this
* instance wasn't setup to wrap policies
*/
public AbstractPolicy getPolicy(EvaluationCtx context)
throws TopLevelPolicyException
{
// setup a list of matching policies
ArrayList list = new ArrayList();
// get an iterator over all the identifiers
Iterator it = policies.values().iterator();
while (it.hasNext()) {
// for each identifier, get only the most recent policy
AbstractPolicy policy =
(AbstractPolicy)(((TreeSet)(it.next())).first());
// see if we match
MatchResult match = policy.match(context);
int result = match.getResult();
// if there was an error, we stop right away
if (result == MatchResult.INDETERMINATE)
throw new TopLevelPolicyException(match.getStatus());
// if we matched, we keep track of the matching policy...
if (result == MatchResult.MATCH) {
// ...first checking if this is the first match and if
// we automaticlly nest policies
if ((combiningAlg == null) && (list.size() > 0)) {
ArrayList code = new ArrayList();
code.add(Status.STATUS_PROCESSING_ERROR);
Status status = new Status(code, "too many applicable"
+ " top-level policies");
throw new TopLevelPolicyException(status);
}
list.add(policy);
}
}
// no errors happened during the search, so now take the right
// action based on how many policies we found
switch (list.size()) {
case 0:
return null;
case 1:
return ((AbstractPolicy)(list.get(0)));
default:
return new PolicySet(parentId, combiningAlg, target, list);
}
}
/**
* Attempts to retrieve a policy based on the given identifier and other
* constraints. If there are multiple versions of the identified policy
* that meet the version constraints, then the most recent version is
* returned.
*
* @param identifier an identifier specifying some policy
* @param type type of reference (policy or policySet) as identified by
* the fields in <code>PolicyReference</code>
* @param constraints any optional constraints on the version of the
* referenced policy (this will never be null, but
* it may impose no constraints, and in fact will
* never impose constraints when used from a pre-2.0
* XACML policy)
*/
public AbstractPolicy getPolicy(String identifier, int type,
VersionConstraints constraints) {
TreeSet set = (TreeSet)(policies.get(identifier));
// if we don't know about this identifier then there's nothing to do
if (set == null)
return null;
// walk through the set starting with the most recent version, looking
// for a match until we exhaust all known versions
Iterator it = set.iterator();
while (it.hasNext()) {
AbstractPolicy policy = (AbstractPolicy)(it.next());
if (constraints.meetsConstraint(policy.getVersion())) {
// we found a valid version, so see if it's the right kind,
// and if it is then we return it
if (type == PolicyReference.POLICY_REFERENCE) {
if (policy instanceof Policy)
return policy;
} else {
if (policy instanceof PolicySet)
return policy;
}
}
}
// we didn't find a match
return null;
}
/**
* A <code>Comparator</code> that is used within this class to maintain
* ordering amongst different versions of the same policy. Note that
* it actually maintains reverse-ordering, since we want to traverse the
* sets in decreasing, not increasing order.
* <p>
* Note that this comparator is only used when there are multiple versions
* of the same policy, which in practice will probably happen far less
* (from this class' point of view) than additions or fetches.
*/
class VersionComparator implements Comparator {
public int compare(Object o1, Object o2) {
// we swap the parameters so that sorting goes largest to smallest
String v1 = ((AbstractPolicy)o2).getVersion();
String v2 = ((AbstractPolicy)o1).getVersion();
// do a quick check to see if the strings are equal (note that
// even if the strings aren't equal, the versions can still
// be equal)
if (v1.equals(v2))
return 0;
// setup tokenizers, and walk through both strings one set of
// numeric values at a time
StringTokenizer tok1 = new StringTokenizer(v1, ".");
StringTokenizer tok2 = new StringTokenizer(v2, ".");
while (tok1.hasMoreTokens()) {
// if there's nothing left in tok2, then v1 is bigger
if (! tok2.hasMoreTokens())
return 1;
// get the next elements in the version, convert to numbers,
// and compare them (continuing with the loop only if the
// two values were equal)
int num1 = Integer.parseInt(tok1.nextToken());
int num2 = Integer.parseInt(tok2.nextToken());
if (num1 > num2)
return 1;
if (num1 < num2)
return -1;
}
// if there's still something left in tok2, then it's bigger
if (tok2.hasMoreTokens())
return -1;
// if we got here it means both versions had the same number of
// elements and all the elements were equal, so the versions
// are in fact equal
return 0;
}
}
}