/**
 * 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
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.xml.security.signature;

import java.io.IOException;
import java.io.OutputStream;
import java.security.Key;
import java.security.PublicKey;
import java.security.cert.X509Certificate;

import javax.crypto.SecretKey;

import org.apache.xml.security.algorithms.SignatureAlgorithm;
import org.apache.xml.security.c14n.CanonicalizationException;
import org.apache.xml.security.c14n.Canonicalizer;
import org.apache.xml.security.c14n.InvalidCanonicalizerException;
import org.apache.xml.security.exceptions.Base64DecodingException;
import org.apache.xml.security.exceptions.XMLSecurityException;
import org.apache.xml.security.keys.KeyInfo;
import org.apache.xml.security.keys.content.X509Data;
import org.apache.xml.security.transforms.Transforms;
import org.apache.xml.security.utils.Base64;
import org.apache.xml.security.utils.Constants;
import org.apache.xml.security.utils.I18n;
import org.apache.xml.security.utils.SignatureElementProxy;
import org.apache.xml.security.utils.SignerOutputStream;
import org.apache.xml.security.utils.UnsyncBufferedOutputStream;
import org.apache.xml.security.utils.XMLUtils;
import org.apache.xml.security.utils.resolver.ResourceResolver;
import org.apache.xml.security.utils.resolver.ResourceResolverSpi;
import org.w3c.dom.Attr;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.Node;
import org.w3c.dom.NodeList;
import org.w3c.dom.Text;

/**
 * Handles <code>&lt;ds:Signature&gt;</code> elements.
 * This is the main class that deals with creating and verifying signatures.
 *
 * <p>There are 2 types of constructors for this class. The ones that take a
 * document, baseURI and 1 or more Java Objects. This is mostly used for
 * signing purposes.
 * The other constructor is the one that takes a DOM Element and a baseURI.
 * This is used mostly with for verifying, when you have a SignatureElement.
 *
 * There are a few different types of methods:
 * <ul><li>The addDocument* methods are used to add References with optional
 * transforms during signing. </li>
 * <li>addKeyInfo* methods are to add Certificates and Keys to the
 * KeyInfo tags during signing. </li>
 * <li>appendObject allows a user to add any XML Structure as an
 * ObjectContainer during signing.</li>
 * <li>sign and checkSignatureValue methods are used to sign and validate the
 * signature. </li></ul>
 */
public final class XMLSignature extends SignatureElementProxy {

    /** MAC - Required HMAC-SHA1 */
    public static final String ALGO_ID_MAC_HMAC_SHA1 = 
        Constants.SignatureSpecNS + "hmac-sha1";

    /** Signature - Required DSAwithSHA1 (DSS) */
    public static final String ALGO_ID_SIGNATURE_DSA = 
        Constants.SignatureSpecNS + "dsa-sha1";

    /** Signature - Recommended RSAwithSHA1 */
    public static final String ALGO_ID_SIGNATURE_RSA = 
        Constants.SignatureSpecNS + "rsa-sha1";
    
    /** Signature - Recommended RSAwithSHA1 */
    public static final String ALGO_ID_SIGNATURE_RSA_SHA1 = 
        Constants.SignatureSpecNS + "rsa-sha1";
    
    /** Signature - NOT Recommended RSAwithMD5 */
    public static final String ALGO_ID_SIGNATURE_NOT_RECOMMENDED_RSA_MD5 = 
        Constants.MoreAlgorithmsSpecNS + "rsa-md5";
    
    /** Signature - Optional RSAwithRIPEMD160 */
    public static final String ALGO_ID_SIGNATURE_RSA_RIPEMD160 = 
        Constants.MoreAlgorithmsSpecNS + "rsa-ripemd160";
    
    /** Signature - Optional RSAwithSHA256 */
    public static final String ALGO_ID_SIGNATURE_RSA_SHA256 = 
        Constants.MoreAlgorithmsSpecNS + "rsa-sha256";
    
    /** Signature - Optional RSAwithSHA384 */
    public static final String ALGO_ID_SIGNATURE_RSA_SHA384 = 
        Constants.MoreAlgorithmsSpecNS + "rsa-sha384";
    
    /** Signature - Optional RSAwithSHA512 */
    public static final String ALGO_ID_SIGNATURE_RSA_SHA512 = 
        Constants.MoreAlgorithmsSpecNS + "rsa-sha512";

    /** HMAC - NOT Recommended HMAC-MD5 */
    public static final String ALGO_ID_MAC_HMAC_NOT_RECOMMENDED_MD5 = 
        Constants.MoreAlgorithmsSpecNS + "hmac-md5";
    
    /** HMAC - Optional HMAC-RIPEMD160 */
    public static final String ALGO_ID_MAC_HMAC_RIPEMD160 = 
        Constants.MoreAlgorithmsSpecNS + "hmac-ripemd160";
    
    /** HMAC - Optional HMAC-SHA256 */
    public static final String ALGO_ID_MAC_HMAC_SHA256 = 
        Constants.MoreAlgorithmsSpecNS + "hmac-sha256";
    
    /** HMAC - Optional HMAC-SHA284 */
    public static final String ALGO_ID_MAC_HMAC_SHA384 = 
        Constants.MoreAlgorithmsSpecNS + "hmac-sha384";
    
    /** HMAC - Optional HMAC-SHA512 */
    public static final String ALGO_ID_MAC_HMAC_SHA512 = 
        Constants.MoreAlgorithmsSpecNS + "hmac-sha512";
    
    /**Signature - Optional ECDSAwithSHA1 */
    public static final String ALGO_ID_SIGNATURE_ECDSA_SHA1 = 
        "http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha1";
    
    /**Signature - Optional ECDSAwithSHA256 */
    public static final String ALGO_ID_SIGNATURE_ECDSA_SHA256 = 
        "http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha256";
    
    /**Signature - Optional ECDSAwithSHA384 */
    public static final String ALGO_ID_SIGNATURE_ECDSA_SHA384 = 
        "http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha384";
    
    /**Signature - Optional ECDSAwithSHA512 */
    public static final String ALGO_ID_SIGNATURE_ECDSA_SHA512 = 
        "http://www.w3.org/2001/04/xmldsig-more#ecdsa-sha512";

    private static org.slf4j.Logger log =
        org.slf4j.LoggerFactory.getLogger(XMLSignature.class);
    
    /** ds:Signature.ds:SignedInfo element */
    private SignedInfo signedInfo;

    /** ds:Signature.ds:KeyInfo */
    private KeyInfo keyInfo;

    /**
     * Checking the digests in References in a Signature are mandatory, but for
     * References inside a Manifest it is application specific. This boolean is
     * to indicate that the References inside Manifests should be validated.
     */
    private boolean followManifestsDuringValidation = false;

    private Element signatureValueElement;

    private static final int MODE_SIGN = 0;
    private static final int MODE_VERIFY = 1;
    private int state = MODE_SIGN;

    /**
     * This creates a new <CODE>ds:Signature</CODE> Element and adds an empty
     * <CODE>ds:SignedInfo</CODE>.
     * The <code>ds:SignedInfo</code> is initialized with the specified Signature
     * algorithm and Canonicalizer.ALGO_ID_C14N_OMIT_COMMENTS which is REQUIRED
     * by the spec. This method's main use is for creating a new signature.
     *
     * @param doc Document in which the signature will be appended after creation.
     * @param baseURI URI to be used as context for all relative URIs.
     * @param signatureMethodURI signature algorithm to use.
     * @throws XMLSecurityException
     */
    public XMLSignature(Document doc, String baseURI, String signatureMethodURI)
        throws XMLSecurityException {
        this(doc, baseURI, signatureMethodURI, 0, Canonicalizer.ALGO_ID_C14N_OMIT_COMMENTS);
    }

    /**
     * Constructor XMLSignature
     *
     * @param doc
     * @param baseURI
     * @param signatureMethodURI the Signature method to be used.
     * @param hmacOutputLength
     * @throws XMLSecurityException
     */
    public XMLSignature(Document doc, String baseURI, String signatureMethodURI,
                        int hmacOutputLength) throws XMLSecurityException {
        this(
            doc, baseURI, signatureMethodURI, hmacOutputLength, 
            Canonicalizer.ALGO_ID_C14N_OMIT_COMMENTS
        );
    }

    /**
     * Constructor XMLSignature
     *
     * @param doc
     * @param baseURI
     * @param signatureMethodURI the Signature method to be used.
     * @param canonicalizationMethodURI the canonicalization algorithm to be 
     * used to c14nize the SignedInfo element.
     * @throws XMLSecurityException
     */
    public XMLSignature(
        Document doc, 
        String baseURI, 
        String signatureMethodURI,
        String canonicalizationMethodURI
    ) throws XMLSecurityException {
        this(doc, baseURI, signatureMethodURI, 0, canonicalizationMethodURI);
    }

    /**
     * Constructor XMLSignature
     *
     * @param doc
     * @param baseURI
     * @param signatureMethodURI
     * @param hmacOutputLength
     * @param canonicalizationMethodURI
     * @throws XMLSecurityException
     */
    public XMLSignature(
        Document doc, 
        String baseURI, 
        String signatureMethodURI,
        int hmacOutputLength, 
        String canonicalizationMethodURI
    ) throws XMLSecurityException {
        super(doc);

        String xmlnsDsPrefix = getDefaultPrefix(Constants.SignatureSpecNS);
        if (xmlnsDsPrefix == null || xmlnsDsPrefix.length() == 0) {
            getElement().setAttributeNS(
                Constants.NamespaceSpecNS, "xmlns", Constants.SignatureSpecNS
            );
        } else {
            getElement().setAttributeNS(
                Constants.NamespaceSpecNS, "xmlns:" + xmlnsDsPrefix, Constants.SignatureSpecNS
            );
        }
        addReturnToSelf();

        this.baseURI = baseURI;
        this.signedInfo = 
            new SignedInfo(
                getDocument(), signatureMethodURI, hmacOutputLength, canonicalizationMethodURI
            );

        appendSelf(this.signedInfo);
        addReturnToSelf();

        // create an empty SignatureValue; this is filled by setSignatureValueElement
        signatureValueElement = 
            XMLUtils.createElementInSignatureSpace(getDocument(), Constants._TAG_SIGNATUREVALUE);

        appendSelf(signatureValueElement);
        addReturnToSelf();
    }

    /**
     *  Creates a XMLSignature in a Document
     * @param doc
     * @param baseURI
     * @param SignatureMethodElem
     * @param CanonicalizationMethodElem
     * @throws XMLSecurityException
     */
    public XMLSignature(
        Document doc, 
        String baseURI, 
        Element SignatureMethodElem, 
        Element CanonicalizationMethodElem
    ) throws XMLSecurityException {
        super(doc);

        String xmlnsDsPrefix = getDefaultPrefix(Constants.SignatureSpecNS);
        if (xmlnsDsPrefix == null || xmlnsDsPrefix.length() == 0) {
            getElement().setAttributeNS(
                Constants.NamespaceSpecNS, "xmlns", Constants.SignatureSpecNS
            );
        } else {
            getElement().setAttributeNS(
                Constants.NamespaceSpecNS, "xmlns:" + xmlnsDsPrefix, Constants.SignatureSpecNS
            );
        }
        addReturnToSelf();

        this.baseURI = baseURI;
        this.signedInfo = 
            new SignedInfo(getDocument(), SignatureMethodElem, CanonicalizationMethodElem);

        appendSelf(this.signedInfo);
        addReturnToSelf();

        // create an empty SignatureValue; this is filled by setSignatureValueElement
        signatureValueElement = 
            XMLUtils.createElementInSignatureSpace(getDocument(), Constants._TAG_SIGNATUREVALUE);

        appendSelf(signatureValueElement);
        addReturnToSelf();
    }
    
    /**
     * This will parse the element and construct the Java Objects.
     * That will allow a user to validate the signature.
     *
     * @param element ds:Signature element that contains the whole signature
     * @param baseURI URI to be prepended to all relative URIs
     * @throws XMLSecurityException
     * @throws XMLSignatureException if the signature is badly formatted
     */
    public XMLSignature(Element element, String baseURI)
        throws XMLSignatureException, XMLSecurityException {
        this(element, baseURI, false);
    }

    /**
     * This will parse the element and construct the Java Objects.
     * That will allow a user to validate the signature.
     *
     * @param element ds:Signature element that contains the whole signature
     * @param baseURI URI to be prepended to all relative URIs
     * @param secureValidation whether secure secureValidation is enabled or not
     * @throws XMLSecurityException
     * @throws XMLSignatureException if the signature is badly formatted
     */
    public XMLSignature(Element element, String baseURI, boolean secureValidation)
        throws XMLSignatureException, XMLSecurityException {
        super(element, baseURI);

        // check out SignedInfo child
        Element signedInfoElem = XMLUtils.getNextElement(element.getFirstChild());

        // check to see if it is there
        if (signedInfoElem == null) {
            Object exArgs[] = { Constants._TAG_SIGNEDINFO, Constants._TAG_SIGNATURE };
            throw new XMLSignatureException("xml.WrongContent", exArgs);
        }

        // create a SignedInfo object from that element
        this.signedInfo = new SignedInfo(signedInfoElem, baseURI, secureValidation);
        // get signedInfoElem again in case it has changed
        signedInfoElem = XMLUtils.getNextElement(element.getFirstChild());

        // check out SignatureValue child
        this.signatureValueElement = 
            XMLUtils.getNextElement(signedInfoElem.getNextSibling());

        // check to see if it exists
        if (signatureValueElement == null) {
            Object exArgs[] = { Constants._TAG_SIGNATUREVALUE, Constants._TAG_SIGNATURE };
            throw new XMLSignatureException("xml.WrongContent", exArgs);
        }
        Attr signatureValueAttr = signatureValueElement.getAttributeNodeNS(null, "Id");
        if (signatureValueAttr != null) {
            signatureValueElement.setIdAttributeNode(signatureValueAttr, true);
        }

        // <element ref="ds:KeyInfo" minOccurs="0"/>
        Element keyInfoElem = 
            XMLUtils.getNextElement(signatureValueElement.getNextSibling());

        // If it exists use it, but it's not mandatory
        if (keyInfoElem != null 
            && Constants.SignatureSpecNS.equals(keyInfoElem.getNamespaceURI()) 
            && Constants._TAG_KEYINFO.equals(keyInfoElem.getLocalName())) {
            this.keyInfo = new KeyInfo(keyInfoElem, baseURI);
            this.keyInfo.setSecureValidation(secureValidation);
        }
        
        // <element ref="ds:Object" minOccurs="0" maxOccurs="unbounded"/>
        Element objectElem =
            XMLUtils.getNextElement(signatureValueElement.getNextSibling());
        while (objectElem != null) {
            Attr objectAttr = objectElem.getAttributeNodeNS(null, "Id");
            if (objectAttr != null) {
                objectElem.setIdAttributeNode(objectAttr, true);
            }

            NodeList nodes = objectElem.getChildNodes();
            int length = nodes.getLength();
            // Register Ids of the Object child elements
            for (int i = 0; i < length; i++) {
                Node child = nodes.item(i);
                if (child.getNodeType() == Node.ELEMENT_NODE) {
                    Element childElem = (Element)child;
                    String tag = childElem.getLocalName();
                    if (tag.equals("Manifest")) {
                        new Manifest(childElem, baseURI);
                    } else if (tag.equals("SignatureProperties")) {
                        new SignatureProperties(childElem, baseURI);
                    }
                }
            }

            objectElem = XMLUtils.getNextElement(objectElem.getNextSibling());
        }
        
        this.state = MODE_VERIFY;
    }

    /**
     * Sets the <code>Id</code> attribute
     *
     * @param id Id value for the id attribute on the Signature Element
     */
    public void setId(String id) {
        if (id != null) {
            setLocalIdAttribute(Constants._ATT_ID, id);
        }
    }

    /**
     * Returns the <code>Id</code> attribute
     *
     * @return the <code>Id</code> attribute
     */
    public String getId() {
        return getLocalAttribute(Constants._ATT_ID);
    }

    /**
     * Returns the completely parsed <code>SignedInfo</code> object.
     *
     * @return the completely parsed <code>SignedInfo</code> object.
     */
    public SignedInfo getSignedInfo() {
        return this.signedInfo;
    }

    /**
     * Returns the octet value of the SignatureValue element.
     * Throws an XMLSignatureException if it has no or wrong content.
     *
     * @return the value of the SignatureValue element.
     * @throws XMLSignatureException If there is no content
     */
    public byte[] getSignatureValue() throws XMLSignatureException {
        try {
            return Base64.decode(signatureValueElement);
        } catch (Base64DecodingException ex) {
            throw new XMLSignatureException("empty", ex);
        }
    }

    /**
     * Base64 encodes and sets the bytes as the content of the SignatureValue
     * Node.
     *
     * @param bytes bytes to be used by SignatureValue before Base64 encoding
     */
    private void setSignatureValueElement(byte[] bytes) {

        while (signatureValueElement.hasChildNodes()) {
            signatureValueElement.removeChild(signatureValueElement.getFirstChild());
        }

        String base64codedValue = Base64.encode(bytes);

        if (base64codedValue.length() > 76 && !XMLUtils.ignoreLineBreaks()) {
            base64codedValue = "\n" + base64codedValue + "\n";
        }

        Text t = createText(base64codedValue);
        signatureValueElement.appendChild(t);
    }

    /**
     * Returns the KeyInfo child. If we are in signing mode and the KeyInfo
     * does not exist yet, it is created on demand and added to the Signature.
     * <br>
     * This allows to add arbitrary content to the KeyInfo during signing.
     *
     * @return the KeyInfo object
     */
    public KeyInfo getKeyInfo() {
        // check to see if we are signing and if we have to create a keyinfo
        if (this.state == MODE_SIGN && this.keyInfo == null) {

            // create the KeyInfo
            this.keyInfo = new KeyInfo(getDocument());

            // get the Element from KeyInfo
            Element keyInfoElement = this.keyInfo.getElement();
            Element firstObject = 
                XMLUtils.selectDsNode(
                    getElement().getFirstChild(), Constants._TAG_OBJECT, 0
                );

            if (firstObject != null) {
                // add it before the object
                getElement().insertBefore(keyInfoElement, firstObject);
                XMLUtils.addReturnBeforeChild(getElement(), firstObject);
            } else {
                // add it as the last element to the signature
                appendSelf(keyInfoElement);
                addReturnToSelf();
            }         
        }

        return this.keyInfo;
    }

    /**
     * Appends an Object (not a <code>java.lang.Object</code> but an Object
     * element) to the Signature. Please note that this is only possible
     * when signing.
     *
     * @param object ds:Object to be appended.
     * @throws XMLSignatureException When this object is used to verify.
     */
    public void appendObject(ObjectContainer object) throws XMLSignatureException {
        //try {
        //if (this.state != MODE_SIGN) {
        // throw new XMLSignatureException(
        //  "signature.operationOnlyBeforeSign");
        //}

        appendSelf(object);
        addReturnToSelf();
        //} catch (XMLSecurityException ex) {
        // throw new XMLSignatureException("empty", ex);
        //}
    }

    /**
     * Returns the <code>i<code>th <code>ds:Object</code> child of the signature
     * or null if no such <code>ds:Object</code> element exists.
     *
     * @param i
     * @return the <code>i<code>th <code>ds:Object</code> child of the signature
     * or null if no such <code>ds:Object</code> element exists.
     */
    public ObjectContainer getObjectItem(int i) {
        Element objElem = 
            XMLUtils.selectDsNode(
                getFirstChild(), Constants._TAG_OBJECT, i
            );

        try {
            return new ObjectContainer(objElem, this.baseURI);
        } catch (XMLSecurityException ex) {
            return null;
        }
    }

    /**
     * Returns the number of all <code>ds:Object</code> elements.
     *
     * @return the number of all <code>ds:Object</code> elements.
     */
    public int getObjectLength() {
        return this.length(Constants.SignatureSpecNS, Constants._TAG_OBJECT);
    }

    /**
     * Digests all References in the SignedInfo, calculates the signature value 
     * and sets it in the SignatureValue Element.
     *
     * @param signingKey the {@link java.security.PrivateKey} or 
     * {@link javax.crypto.SecretKey} that is used to sign.
     * @throws XMLSignatureException
     */
    public void sign(Key signingKey) throws XMLSignatureException {

        if (signingKey instanceof PublicKey) {
            throw new IllegalArgumentException(
                I18n.translate("algorithms.operationOnlyVerification")
            );
        }

        try {
            //Create a SignatureAlgorithm object
            SignedInfo si = this.getSignedInfo();
            SignatureAlgorithm sa = si.getSignatureAlgorithm();
            OutputStream so = null;
            try {
                // initialize SignatureAlgorithm for signing
                sa.initSign(signingKey);            

                // generate digest values for all References in this SignedInfo
                si.generateDigestValues();
                so = new UnsyncBufferedOutputStream(new SignerOutputStream(sa));
                // get the canonicalized bytes from SignedInfo
                si.signInOctetStream(so);
            } catch (XMLSecurityException ex) {
                throw ex;
            } finally {
                if (so != null) {
                    try {
                        so.close();
                    } catch (IOException ex) {
                        if (log.isDebugEnabled()) {
                            log.debug(ex.getMessage(), ex);
                        }
                    }
                }
            }

            // set them on the SignatureValue element
            this.setSignatureValueElement(sa.sign());
        } catch (XMLSignatureException ex) {
            throw ex;
        } catch (CanonicalizationException ex) {
            throw new XMLSignatureException("empty", ex);
        } catch (InvalidCanonicalizerException ex) {
            throw new XMLSignatureException("empty", ex);
        } catch (XMLSecurityException ex) {
            throw new XMLSignatureException("empty", ex);
        }
    }

    /**
     * Adds a {@link ResourceResolver} to enable the retrieval of resources.
     *
     * @param resolver
     */
    public void addResourceResolver(ResourceResolver resolver) {
        this.getSignedInfo().addResourceResolver(resolver);
    }

    /**
     * Adds a {@link ResourceResolverSpi} to enable the retrieval of resources.
     *
     * @param resolver
     */
    public void addResourceResolver(ResourceResolverSpi resolver) {
        this.getSignedInfo().addResourceResolver(resolver);
    }

    /**
     * Extracts the public key from the certificate and verifies if the signature
     * is valid by re-digesting all References, comparing those against the
     * stored DigestValues and then checking to see if the Signatures match on
     * the SignedInfo.
     *
     * @param cert Certificate that contains the public key part of the keypair 
     * that was used to sign.
     * @return true if the signature is valid, false otherwise
     * @throws XMLSignatureException
     */
    public boolean checkSignatureValue(X509Certificate cert)
        throws XMLSignatureException {
        // see if cert is null
        if (cert != null) {
            // check the values with the public key from the cert
            return this.checkSignatureValue(cert.getPublicKey());
        } 

        Object exArgs[] = { "Didn't get a certificate" };
        throw new XMLSignatureException("empty", exArgs);
    }

    /**
     * Verifies if the signature is valid by redigesting all References,
     * comparing those against the stored DigestValues and then checking to see
     * if the Signatures match on the SignedInfo.
     *
     * @param pk {@link java.security.PublicKey} part of the keypair or 
     * {@link javax.crypto.SecretKey} that was used to sign
     * @return true if the signature is valid, false otherwise
     * @throws XMLSignatureException
     */
    public boolean checkSignatureValue(Key pk) throws XMLSignatureException {
        //COMMENT: pk suggests it can only be a public key?
        //check to see if the key is not null
        if (pk == null) {
            Object exArgs[] = { "Didn't get a key" };
            throw new XMLSignatureException("empty", exArgs);
        }
        // all references inside the signedinfo need to be dereferenced and
        // digested again to see if the outcome matches the stored value in the
        // SignedInfo.
        // If followManifestsDuringValidation is true it will do the same for
        // References inside a Manifest.
        try {
            SignedInfo si = this.getSignedInfo();
            //create a SignatureAlgorithms from the SignatureMethod inside
            //SignedInfo. This is used to validate the signature.
            SignatureAlgorithm sa = si.getSignatureAlgorithm();               
            if (log.isDebugEnabled()) {
                log.debug("signatureMethodURI = " + sa.getAlgorithmURI());
                log.debug("jceSigAlgorithm    = " + sa.getJCEAlgorithmString());
                log.debug("jceSigProvider     = " + sa.getJCEProviderName());
                log.debug("PublicKey = " + pk);
            }
            byte sigBytes[] = null;
            try {
                sa.initVerify(pk);

                // Get the canonicalized (normalized) SignedInfo
                SignerOutputStream so = new SignerOutputStream(sa);
                OutputStream bos = new UnsyncBufferedOutputStream(so);

                si.signInOctetStream(bos);
                bos.close();
                // retrieve the byte[] from the stored signature
                sigBytes = this.getSignatureValue();
            } catch (IOException ex) {
                if (log.isDebugEnabled()) {
                    log.debug(ex.getMessage(), ex);
                }
                // Impossible...
            } catch (XMLSecurityException ex) {
                throw ex;
            }

            // have SignatureAlgorithm sign the input bytes and compare them to 
            // the bytes that were stored in the signature.
            if (!sa.verify(sigBytes)) {
                log.warn("Signature verification failed.");
                return false;
            }

            return si.verify(this.followManifestsDuringValidation);
        } catch (XMLSignatureException ex) {
            throw ex;
        } catch (XMLSecurityException ex) {
            throw new XMLSignatureException("empty", ex);
        } 
    }

    /**
     * Add a Reference with full parameters to this Signature
     *
     * @param referenceURI URI of the resource to be signed. Can be null in 
     * which case the dereferencing is application specific. Can be "" in which 
     * it's the parent node (or parent document?). There can only be one "" in 
     * each signature.
     * @param trans Optional list of transformations to be done before digesting
     * @param digestURI Mandatory URI of the digesting algorithm to use.
     * @param referenceId Optional id attribute for this Reference
     * @param referenceType Optional mimetype for the URI
     * @throws XMLSignatureException
     */
    public void addDocument(
        String referenceURI, 
        Transforms trans, 
        String digestURI, 
        String referenceId, 
        String referenceType
    ) throws XMLSignatureException {
        this.signedInfo.addDocument(
            this.baseURI, referenceURI, trans, digestURI, referenceId, referenceType
        );
    }

    /**
     * This method is a proxy method for the {@link Manifest#addDocument} method.
     *
     * @param referenceURI URI according to the XML Signature specification.
     * @param trans List of transformations to be applied.
     * @param digestURI URI of the digest algorithm to be used.
     * @see Manifest#addDocument
     * @throws XMLSignatureException
     */
    public void addDocument(
        String referenceURI, 
        Transforms trans, 
        String digestURI
    ) throws XMLSignatureException {
        this.signedInfo.addDocument(this.baseURI, referenceURI, trans, digestURI, null, null);
    }

    /**
     * Adds a Reference with just the URI and the transforms. This used the
     * SHA1 algorithm as a default digest algorithm.
     *
     * @param referenceURI URI according to the XML Signature specification.
     * @param trans List of transformations to be applied.
     * @throws XMLSignatureException
     */
    public void addDocument(String referenceURI, Transforms trans)
        throws XMLSignatureException {
        this.signedInfo.addDocument(
            this.baseURI, referenceURI, trans, Constants.ALGO_ID_DIGEST_SHA1, null, null
        );
    }

    /**
     * Add a Reference with just this URI. It uses SHA1 by default as the digest
     * algorithm
     *
     * @param referenceURI URI according to the XML Signature specification.
     * @throws XMLSignatureException
     */
    public void addDocument(String referenceURI) throws XMLSignatureException {
        this.signedInfo.addDocument(
            this.baseURI, referenceURI, null, Constants.ALGO_ID_DIGEST_SHA1, null, null
        );
    }

    /**
     * Add an X509 Certificate to the KeyInfo. This will include the whole cert
     * inside X509Data/X509Certificate tags.
     *
     * @param cert Certificate to be included. This should be the certificate of
     * the key that was used to sign.
     * @throws XMLSecurityException
     */
    public void addKeyInfo(X509Certificate cert) throws XMLSecurityException {
        X509Data x509data = new X509Data(getDocument());

        x509data.addCertificate(cert);
        this.getKeyInfo().add(x509data);
    }

    /**
     * Add this public key to the KeyInfo. This will include the complete key in
     * the KeyInfo structure.
     *
     * @param pk
     */
    public void addKeyInfo(PublicKey pk) {
        this.getKeyInfo().add(pk);
    }

    /**
     * Proxy method for {@link SignedInfo#createSecretKey(byte[])}. If you want 
     * to create a MAC, this method helps you to obtain the 
     * {@link javax.crypto.SecretKey} from octets.
     *
     * @param secretKeyBytes
     * @return the secret key created.
     * @see SignedInfo#createSecretKey(byte[])
     */
    public SecretKey createSecretKey(byte[] secretKeyBytes) {
        return this.getSignedInfo().createSecretKey(secretKeyBytes);
    }

    /**
     * Signal whether Manifest should be automatically validated.
     * Checking the digests in References in a Signature are mandatory, but for
     * References inside a Manifest it is application specific. This boolean is
     * to indicate that the References inside Manifests should be validated.
     *
     * @param followManifests
     * @see <a href="http://www.w3.org/TR/xmldsig-core/#sec-CoreValidation">
     * Core validation section in the XML Signature Rec.</a>
     */
    public void setFollowNestedManifests(boolean followManifests) {
        this.followManifestsDuringValidation = followManifests;
    }

    /**
     * Get the local name of this element
     *
     * @return Constants._TAG_SIGNATURE
     */
    public String getBaseLocalName() {
        return Constants._TAG_SIGNATURE;
    }
}
