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ATT reference implementation of XACML PDP engine
/*
*
* Copyright (c) 2013,2019 AT&T Knowledge Ventures
* SPDX-License-Identifier: MIT
*/
package com.att.research.xacmlatt.pdp.policy.expressions;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import javax.xml.xpath.XPath;
import javax.xml.xpath.XPathConstants;
import javax.xml.xpath.XPathExpression;
import javax.xml.xpath.XPathExpressionException;
import javax.xml.xpath.XPathFactory;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import com.att.research.xacml.api.Attribute;
import com.att.research.xacml.api.AttributeValue;
import com.att.research.xacml.api.DataType;
import com.att.research.xacml.api.DataTypeException;
import com.att.research.xacml.api.DataTypeFactory;
import com.att.research.xacml.api.Identifier;
import com.att.research.xacml.api.Request;
import com.att.research.xacml.api.RequestAttributes;
import com.att.research.xacml.api.StatusCode;
import com.att.research.xacml.std.StdStatus;
import com.att.research.xacml.std.StdStatusCode;
import com.att.research.xacml.std.datatypes.DataTypes;
import com.att.research.xacml.std.datatypes.NodeNamespaceContext;
import com.att.research.xacml.std.datatypes.XPathExpressionWrapper;
import com.att.research.xacml.std.dom.DOMStructureException;
import com.att.research.xacml.std.dom.DOMUtil;
import com.att.research.xacml.util.FactoryException;
import com.att.research.xacmlatt.pdp.eval.EvaluationContext;
import com.att.research.xacmlatt.pdp.eval.EvaluationException;
import com.att.research.xacmlatt.pdp.policy.Bag;
import com.att.research.xacmlatt.pdp.policy.ExpressionResult;
import com.att.research.xacmlatt.pdp.policy.PolicyDefaults;
/**
* AttributeSelector extends {@link com.att.research.xacmlatt.pdp.policy.expressions.AttributeRetrievalBase} to implement
* the XACML AttributeSelector element.
*
* @author car
* @version $Revision: 1.2 $
*/
public class AttributeSelector extends AttributeRetrievalBase {
private Identifier contextSelectorId;
private String path;
@SuppressWarnings("unused")
private DataType dataType;
protected DataType getDataType() {
Identifier dataTypeIdThis = this.getDataTypeId();
if (dataTypeIdThis == null) {
return null;
} else {
DataTypeFactory dataTypeFactory = null;
try {
dataTypeFactory = DataTypeFactory.newInstance();
if (dataTypeFactory == null) {
return null;
}
} catch (FactoryException ex) {
return null;
}
return (this.dataType = dataTypeFactory.getDataType(dataTypeIdThis));
}
}
public AttributeSelector(StatusCode statusCodeIn, String statusMessageIn) {
super(statusCodeIn, statusMessageIn);
}
public AttributeSelector(StatusCode statusCodeIn) {
super(statusCodeIn);
}
public AttributeSelector() {
}
public Identifier getContextSelectorId() {
return this.contextSelectorId;
}
public void setContextSelectorId(Identifier identifier) {
this.contextSelectorId = identifier;
}
public String getPath() {
return this.path;
}
public void setPath(String pathIn) {
this.path = pathIn;
}
@Override
protected boolean validateComponent() {
if (!super.validateComponent()) {
return false;
} else if (this.getPath() == null) {
this.setStatus(StdStatusCode.STATUS_CODE_SYNTAX_ERROR, "Missing Path");
return false;
} else {
return true;
}
}
/**
* If there is a context selector ID, get the attributes from the given RequestAttributes with that
* ID, ensure they are XPathExpressions and return them.
*
* @param requestAttributes
* @return List of XPathExpression objects
*/
protected List getContextSelectorValues(RequestAttributes requestAttributes) {
Identifier thisContextSelectorId = this.getContextSelectorId();
if (thisContextSelectorId == null) {
return null;
}
List listXPathExpressions = null;
Iterator iterAttributes = requestAttributes.getAttributes(thisContextSelectorId);
if (iterAttributes != null) {
while (iterAttributes.hasNext()) {
Attribute attribute = iterAttributes.next();
Iterator> iterXPathExpressions = attribute.findValues(DataTypes.DT_XPATHEXPRESSION);
if (iterXPathExpressions != null && iterXPathExpressions.hasNext()) {
if (listXPathExpressions == null) {
listXPathExpressions = new ArrayList<>();
}
listXPathExpressions.add(iterXPathExpressions.next().getValue());
}
}
}
return listXPathExpressions;
}
@Override
public ExpressionResult evaluate(EvaluationContext evaluationContext, PolicyDefaults policyDefaults) throws EvaluationException {
if (!this.validate()) {
return ExpressionResult.newError(new StdStatus(this.getStatusCode(), this.getStatusMessage()));
}
/*
* Get the DataType for this AttributeSelector for converting the resulting nodes into AttributeValues
*/
DataType thisDataType = this.getDataType();
/*
* Get the Request so we can find the XPathExpression to locate the root node and to find the Content element
* of the requested category.
*/
Request request = evaluationContext.getRequest();
assert(request != null);
/*
* Get the RequestAttributes objects for our Category. If none are found, then we abort quickly with either
* an empty or indeterminate result.
*/
Iterator iterRequestAttributes = request.getRequestAttributes(this.getCategory());
if (iterRequestAttributes == null || !iterRequestAttributes.hasNext()) {
return this.getEmptyResult("No Attributes with Category " + this.getCategory().toString(), null);
}
/*
* Section 5.30 of the XACML 3.0 specification is a little vague about how to use the
* ContextSelectorId in the face of having multiple Attributes elements with the same CategoryId. My interpretation
* is that each is distinct, so we look for an attribute matching the ContextSelectorId in each matching Attributes element
* and use that to search the Content in that particular Attributes element. If either an Attribute matching the context selector id
* is not found or there is no Content, then that particular Attributes element is skipped.
*/
Bag bagAttributeValues = new Bag();
StdStatus statusFirstError = null;
while (iterRequestAttributes.hasNext()) {
RequestAttributes requestAttributes = iterRequestAttributes.next();
/*
* See if we have a Content element to query.
*/
Node nodeContentRoot = requestAttributes.getContentRoot();
if (nodeContentRoot != null) {
List listNodesToQuery = new ArrayList<>();
List listXPathExpressions = this.getContextSelectorValues(requestAttributes);
if (listXPathExpressions == null) {
listNodesToQuery.add(nodeContentRoot);
} else {
Iterator iterXPathExpressions = listXPathExpressions.iterator();
while (iterXPathExpressions.hasNext()) {
XPathExpression xpathExpression = iterXPathExpressions.next();
Node nodeContent = requestAttributes.getContentNodeByXpathExpression(xpathExpression);
if (nodeContent != null) {
listNodesToQuery.add(nodeContent);
}
}
}
/*
* If there are any nodes to query, do so now and add the results
*/
if (listNodesToQuery.size() > 0) {
for (Node nodeToQuery : listNodesToQuery) {
NodeList nodeList = null;
try {
XPath xPath = XPathFactory.newInstance().newXPath();
xPath.setNamespaceContext(new NodeNamespaceContext(nodeToQuery.getOwnerDocument()));
XPathExpression xPathExpression = xPath.compile(this.getPath());
Node nodeToQueryDocumentRoot = null;
try {
nodeToQueryDocumentRoot = DOMUtil.getDirectDocumentChild(nodeToQuery);
} catch (DOMStructureException ex) {
return ExpressionResult.newError(new StdStatus(StdStatusCode.STATUS_CODE_PROCESSING_ERROR, "Exception processing context node: " + ex.getMessage()));
}
nodeList = (NodeList)xPathExpression.evaluate(nodeToQueryDocumentRoot, XPathConstants.NODESET);
} catch (XPathExpressionException ex) {
if (statusFirstError == null) {
statusFirstError = new StdStatus(StdStatusCode.STATUS_CODE_PROCESSING_ERROR, "XPathExpressionException: " + ex.getMessage());
}
}
if (nodeList != null && nodeList.getLength() > 0) {
for (int i = 0 ; i < nodeList.getLength() ; i++) {
AttributeValue attributeValueNode = null;
try {
attributeValueNode = thisDataType.createAttributeValue(nodeList.item(i));
} catch (DataTypeException ex) {
if (statusFirstError == null) {
statusFirstError = new StdStatus(StdStatusCode.STATUS_CODE_PROCESSING_ERROR, ex.getMessage());
}
}
if (attributeValueNode != null) {
bagAttributeValues.add(attributeValueNode);
} else if (statusFirstError == null) {
statusFirstError = new StdStatus(StdStatusCode.STATUS_CODE_PROCESSING_ERROR, "Unable to convert node to " + this.getDataTypeId().toString());
}
}
}
}
}
}
}
if (bagAttributeValues.size() == 0) {
if (statusFirstError == null) {
return this.getEmptyResult("No Content found", null);
} else {
return ExpressionResult.newError(statusFirstError);
}
} else {
return ExpressionResult.newBag(bagAttributeValues);
}
}
@Override
public String toString() {
StringBuilder stringBuilder = new StringBuilder("{");
stringBuilder.append("super=");
stringBuilder.append(super.toString());
Object objectToDump;
if ((objectToDump = this.getContextSelectorId()) != null) {
stringBuilder.append(",contextSelectorId=");
stringBuilder.append(objectToDump.toString());
}
if ((objectToDump = this.getPath()) != null) {
stringBuilder.append(",path=");
stringBuilder.append((String)objectToDump);
}
stringBuilder.append('}');
return stringBuilder.toString();
}
}