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/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
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package com.sun.org.apache.xml.internal.security.keys.keyresolver.implementations;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.PublicKey;
import java.security.cert.CertificateException;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.ListIterator;
import java.util.Set;

import javax.xml.parsers.ParserConfigurationException;

import com.sun.org.apache.xml.internal.security.c14n.CanonicalizationException;
import com.sun.org.apache.xml.internal.security.exceptions.XMLSecurityException;
import com.sun.org.apache.xml.internal.security.keys.content.RetrievalMethod;
import com.sun.org.apache.xml.internal.security.keys.content.x509.XMLX509Certificate;
import com.sun.org.apache.xml.internal.security.keys.keyresolver.KeyResolver;
import com.sun.org.apache.xml.internal.security.keys.keyresolver.KeyResolverException;
import com.sun.org.apache.xml.internal.security.keys.keyresolver.KeyResolverSpi;
import com.sun.org.apache.xml.internal.security.keys.storage.StorageResolver;
import com.sun.org.apache.xml.internal.security.signature.XMLSignatureInput;
import com.sun.org.apache.xml.internal.security.transforms.Transforms;
import com.sun.org.apache.xml.internal.security.utils.Constants;
import com.sun.org.apache.xml.internal.security.utils.XMLUtils;
import com.sun.org.apache.xml.internal.security.utils.resolver.ResourceResolver;
import org.w3c.dom.Attr;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.xml.sax.SAXException;

The RetrievalMethodResolver can retrieve public keys and certificates from
other locations. The location is specified using the ds:RetrievalMethod
element which points to the location. This includes the handling of raw
(binary) X.509 certificate which are not encapsulated in an XML structure.
If the retrieval process encounters an element which the
RetrievalMethodResolver cannot handle itself, resolving of the extracted
element is delegated back to the KeyResolver mechanism.
/**
 * The RetrievalMethodResolver can retrieve public keys and certificates from
 * other locations. The location is specified using the ds:RetrievalMethod
 * element which points to the location. This includes the handling of raw
 * (binary) X.509 certificate which are not encapsulated in an XML structure.
 * If the retrieval process encounters an element which the
 * RetrievalMethodResolver cannot handle itself, resolving of the extracted
 * element is delegated back to the KeyResolver mechanism.
 *
 */
public class RetrievalMethodResolver extends KeyResolverSpi {

    private static final com.sun.org.slf4j.internal.Logger LOG =
        com.sun.org.slf4j.internal.LoggerFactory.getLogger(RetrievalMethodResolver.class);

    
Method engineResolvePublicKey
{@inheritDoc}
Params:
element – 
baseURI – 
storage – /**
     * Method engineResolvePublicKey
     * {@inheritDoc}
     * @param element
     * @param baseURI
     * @param storage
     */
    public PublicKey engineLookupAndResolvePublicKey(
           Element element, String baseURI, StorageResolver storage
    ) {
        if (!XMLUtils.elementIsInSignatureSpace(element, Constants._TAG_RETRIEVALMETHOD)) {
            return null;
        }

        try {
            // Create a retrieval method over the given element
            RetrievalMethod rm = new RetrievalMethod(element, baseURI);
            String type = rm.getType();
            XMLSignatureInput resource = resolveInput(rm, baseURI, secureValidation);
            if (RetrievalMethod.TYPE_RAWX509.equals(type)) {
                // a raw certificate, direct parsing is done!
                X509Certificate cert = getRawCertificate(resource);
                if (cert != null) {
                    return cert.getPublicKey();
                }
                return null;
             }
             Element e = obtainReferenceElement(resource, secureValidation);

             // Check to make sure that the reference is not to another RetrievalMethod
             // which points to this element
             if (XMLUtils.elementIsInSignatureSpace(e, Constants._TAG_RETRIEVALMETHOD)) {
                 if (secureValidation) {
                     if (LOG.isDebugEnabled()) {
                         String error = "Error: It is forbidden to have one RetrievalMethod "
                             + "point to another with secure validation";
                         LOG.debug(error);
                     }
                     return null;
                 }
                 RetrievalMethod rm2 = new RetrievalMethod(e, baseURI);
                 XMLSignatureInput resource2 = resolveInput(rm2, baseURI, secureValidation);
                 Element e2 = obtainReferenceElement(resource2, secureValidation);
                 if (e2 == element) {
                     LOG.debug("Error: Can't have RetrievalMethods pointing to each other");
                     return null;
                 }
             }

             return resolveKey(e, baseURI, storage);
         } catch (XMLSecurityException ex) {
             LOG.debug("XMLSecurityException", ex);
         } catch (CertificateException ex) {
             LOG.debug("CertificateException", ex);
         } catch (IOException ex) {
             LOG.debug("IOException", ex);
         } catch (ParserConfigurationException e) {
             LOG.debug("ParserConfigurationException", e);
         } catch (SAXException e) {
             LOG.debug("SAXException", e);
         }
         return null;
    }

    
Method engineResolveX509Certificate
{@inheritDoc}
Params:
element – 
baseURI – 
storage – /**
     * Method engineResolveX509Certificate
     * {@inheritDoc}
     * @param element
     * @param baseURI
     * @param storage
     */
    public X509Certificate engineLookupResolveX509Certificate(
        Element element, String baseURI, StorageResolver storage) {
        if (!XMLUtils.elementIsInSignatureSpace(element, Constants._TAG_RETRIEVALMETHOD)) {
             return null;
        }

        try {
            RetrievalMethod rm = new RetrievalMethod(element, baseURI);
            String type = rm.getType();
            XMLSignatureInput resource = resolveInput(rm, baseURI, secureValidation);
            if (RetrievalMethod.TYPE_RAWX509.equals(type)) {
                return getRawCertificate(resource);
            }

            Element e = obtainReferenceElement(resource, secureValidation);

            // Check to make sure that the reference is not to another RetrievalMethod
            // which points to this element
            if (XMLUtils.elementIsInSignatureSpace(e, Constants._TAG_RETRIEVALMETHOD)) {
                if (secureValidation) {
                    if (LOG.isDebugEnabled()) {
                        String error = "Error: It is forbidden to have one RetrievalMethod "
                            + "point to another with secure validation";
                        LOG.debug(error);
                    }
                    return null;
                }
                RetrievalMethod rm2 = new RetrievalMethod(e, baseURI);
                XMLSignatureInput resource2 = resolveInput(rm2, baseURI, secureValidation);
                Element e2 = obtainReferenceElement(resource2, secureValidation);
                if (e2 == element) {
                    LOG.debug("Error: Can't have RetrievalMethods pointing to each other");
                    return null;
                }
            }

            return resolveCertificate(e, baseURI, storage);
        } catch (XMLSecurityException ex) {
            LOG.debug("XMLSecurityException", ex);
        } catch (CertificateException ex) {
            LOG.debug("CertificateException", ex);
        } catch (IOException ex) {
            LOG.debug("IOException", ex);
        } catch (ParserConfigurationException e) {
            LOG.debug("ParserConfigurationException", e);
        } catch (SAXException e) {
            LOG.debug("SAXException", e);
        }
        return null;
    }

    
Retrieves a x509Certificate from the given information
Params:
e – 
baseURI – 
storage – 
Throws:
KeyResolverException – 
Returns:
a x509Certificate from the given information/**
     * Retrieves a x509Certificate from the given information
     * @param e
     * @param baseURI
     * @param storage
     * @return a x509Certificate from the given information
     * @throws KeyResolverException
     */
    private static X509Certificate resolveCertificate(
        Element e, String baseURI, StorageResolver storage
    ) throws KeyResolverException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Now we have a {" + e.getNamespaceURI() + "}"
                + e.getLocalName() + " Element");
        }
        // An element has been provided
        if (e != null) {
            return KeyResolver.getX509Certificate(e, baseURI, storage);
        }
        return null;
    }

    
Retrieves a PublicKey from the given information
Params:
e – 
baseURI – 
storage – 
Throws:
KeyResolverException – 
Returns:
a PublicKey from the given information/**
     * Retrieves a PublicKey from the given information
     * @param e
     * @param baseURI
     * @param storage
     * @return a PublicKey from the given information
     * @throws KeyResolverException
     */
    private static PublicKey resolveKey(
        Element e, String baseURI, StorageResolver storage
    ) throws KeyResolverException {
        if (LOG.isDebugEnabled()) {
            LOG.debug("Now we have a {" + e.getNamespaceURI() + "}"
                + e.getLocalName() + " Element");
        }
        // An element has been provided
        if (e != null) {
            return KeyResolver.getPublicKey(e, baseURI, storage);
        }
        return null;
    }

    private static Element obtainReferenceElement(XMLSignatureInput resource, boolean secureValidation)
        throws CanonicalizationException, ParserConfigurationException,
        IOException, SAXException, KeyResolverException {
        Element e;
        if (resource.isElement()){
            e = (Element) resource.getSubNode();
        } else if (resource.isNodeSet()) {
            // Retrieved resource is a nodeSet
            e = getDocumentElement(resource.getNodeSet());
        } else {
            // Retrieved resource is an inputStream
            byte inputBytes[] = resource.getBytes();
            e = getDocFromBytes(inputBytes, secureValidation);
            // otherwise, we parse the resource, create an Element and delegate
            LOG.debug("we have to parse {} bytes", inputBytes.length);
        }
        return e;
    }

    private static X509Certificate getRawCertificate(XMLSignatureInput resource)
        throws CanonicalizationException, IOException, CertificateException {
        byte inputBytes[] = resource.getBytes();
        // if the resource stores a raw certificate, we have to handle it
        CertificateFactory certFact =
            CertificateFactory.getInstance(XMLX509Certificate.JCA_CERT_ID);
        try (InputStream is = new ByteArrayInputStream(inputBytes)) {
            return (X509Certificate) certFact.generateCertificate(is);
        }
    }

    
Resolves the input from the given retrieval method
Throws:
XMLSecurityException – 
Returns:
the input from the given retrieval method/**
     * Resolves the input from the given retrieval method
     * @return the input from the given retrieval method
     * @throws XMLSecurityException
     */
    private static XMLSignatureInput resolveInput(
        RetrievalMethod rm, String baseURI, boolean secureValidation
    ) throws XMLSecurityException {
        Attr uri = rm.getURIAttr();
        // Apply the transforms
        Transforms transforms = rm.getTransforms();
        ResourceResolver resRes = ResourceResolver.getInstance(uri, baseURI, secureValidation);
        XMLSignatureInput resource = resRes.resolve(uri, baseURI, secureValidation);
        if (transforms != null) {
            LOG.debug("We have Transforms");
            resource = transforms.performTransforms(resource);
        }
        return resource;
    }

    
Method engineResolveSecretKey
{@inheritDoc}
Params:
element – 
baseURI – 
storage – /**
     * Method engineResolveSecretKey
     * {@inheritDoc}
     * @param element
     * @param baseURI
     * @param storage
     */
    public javax.crypto.SecretKey engineLookupAndResolveSecretKey(
        Element element, String baseURI, StorageResolver storage
    ) {
        return null;
    }

    private static Element getDocumentElement(Set<Node> set) {
        Iterator<Node> it = set.iterator();
        Element e = null;
        while (it.hasNext()) {
            Node currentNode = it.next();
            if (currentNode != null && Node.ELEMENT_NODE == currentNode.getNodeType()) {
                e = (Element) currentNode;
                break;
            }
        }
        List<Node> parents = new ArrayList<>();

        // Obtain all the parents of the elemnt
        while (e != null) {
            parents.add(e);
            Node n = e.getParentNode();
            if (n == null || Node.ELEMENT_NODE != n.getNodeType()) {
                break;
            }
            e = (Element) n;
        }
        // Visit them in reverse order.
        ListIterator<Node> it2 = parents.listIterator(parents.size()-1);
        Element ele = null;
        while (it2.hasPrevious()) {
            ele = (Element) it2.previous();
            if (set.contains(ele)) {
                return ele;
            }
        }
        return null;
    }
}