/**
    * 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.ws.security.message;
  
  import org.apache.ws.security.WSConstants;
  import org.apache.ws.security.WSDocInfo;
  import org.apache.ws.security.WSEncryptionPart;
  import org.apache.ws.security.WSSConfig;
  import org.apache.ws.security.WSSecurityException;
  import org.apache.ws.security.components.crypto.Crypto;
  import org.apache.ws.security.components.crypto.CryptoType;
  import org.apache.ws.security.message.token.BinarySecurity;
  import org.apache.ws.security.message.token.DOMX509Data;
  import org.apache.ws.security.message.token.DOMX509IssuerSerial;
  import org.apache.ws.security.message.token.KerberosSecurity;
  import org.apache.ws.security.message.token.PKIPathSecurity;
  import org.apache.ws.security.message.token.Reference;
  import org.apache.ws.security.message.token.SecurityTokenReference;
  import org.apache.ws.security.message.token.X509Security;
  import org.apache.ws.security.transform.STRTransform;
  import org.apache.ws.security.util.Base64;
  import org.apache.ws.security.util.WSSecurityUtil;
  
  import org.w3c.dom.Document;
  import org.w3c.dom.Element;
  import org.w3c.dom.Node;
  
  import java.security.NoSuchProviderException;
  import java.security.cert.X509Certificate;
  import java.util.ArrayList;
  import java.util.List;
  
  import javax.xml.crypto.XMLStructure;
  import javax.xml.crypto.dom.DOMStructure;
  import javax.xml.crypto.dsig.CanonicalizationMethod;
  import javax.xml.crypto.dsig.SignatureMethod;
  import javax.xml.crypto.dsig.SignedInfo;
  import javax.xml.crypto.dsig.XMLSignature;
  import javax.xml.crypto.dsig.XMLSignatureFactory;
  import javax.xml.crypto.dsig.XMLSignContext;
  import javax.xml.crypto.dsig.dom.DOMSignContext;
  import javax.xml.crypto.dsig.keyinfo.KeyInfo;
  import javax.xml.crypto.dsig.keyinfo.KeyInfoFactory;
  import javax.xml.crypto.dsig.keyinfo.KeyValue;
  import javax.xml.crypto.dsig.spec.C14NMethodParameterSpec;
  import javax.xml.crypto.dsig.spec.ExcC14NParameterSpec;
  
  
  /**
   * Creates a Signature according to WS Specification, X509 profile.
   * 
   * This class is a re-factored implementation of the previous WSS4J class
   * <code>WSSignEnvelope</code>. This new class allows better control of
   * the process to create a Signature and to add it to the Security header.
   * 
   * The flexibility and fine granular control is required to implement a handler
   * that uses WSSecurityPolicy files to control the setup of a Security header.
   * 
   * @author Davanum Srinivas (dims@yahoo.com)
   * @author Werner Dittmann (werner@apache.org)
   */
  public class WSSecSignature extends WSSecSignatureBase {
  
      private static org.apache.commons.logging.Log log = 
          org.apache.commons.logging.LogFactory.getLog(WSSecSignature.class);
  
      protected boolean useSingleCert = true;
      protected String sigAlgo = null;
      protected String canonAlgo = WSConstants.C14N_EXCL_OMIT_COMMENTS;
      protected byte[] signatureValue = null;
      protected Document document = null;
      protected WSDocInfo wsDocInfo = null;
      protected String certUri = null;
      protected String keyInfoUri = null;
      protected SecurityTokenReference secRef = null;
      protected String strUri = null;
      protected BinarySecurity bstToken = null;
      
      protected KeyInfoFactory keyInfoFactory;
      protected XMLSignatureFactory signatureFactory;
      protected KeyInfo keyInfo;
      protected CanonicalizationMethod c14nMethod;
     protected XMLSignature sig;
     protected byte[] secretKey = null;
     protected String customTokenValueType;
     protected String customTokenId;
     
     private String encrKeySha1value = null;
     private Crypto crypto = null;
     private String digestAlgo = WSConstants.SHA1;
     private X509Certificate useThisCert = null;
     private Element securityHeader = null;
     private boolean useCustomSecRef;
 
     public WSSecSignature() {
         super();
         init();
     }
     
     public WSSecSignature(WSSConfig config) {
         super(config);
         init();
     }
     
     private void init() {
         // Try to install the Santuario Provider - fall back to the JDK provider if this does
         // not work
         try {
             signatureFactory = XMLSignatureFactory.getInstance("DOM", "ApacheXMLDSig");
         } catch (NoSuchProviderException ex) {
             signatureFactory = XMLSignatureFactory.getInstance("DOM");
         }
         try {
             keyInfoFactory = KeyInfoFactory.getInstance("DOM", "ApacheXMLDSig");
         } catch (NoSuchProviderException ex) {
             keyInfoFactory = KeyInfoFactory.getInstance("DOM");
         }
     }
    
     /**
      * Initialize a WSSec Signature.
      * 
      * The method sets up and initializes a WSSec Signature structure after the
      * relevant information was set. After setup of the references to elements
      * to sign may be added. After all references are added they can be signed.
      * 
      * This method does not add the Signature element to the security header.
      * See <code>prependSignatureElementToHeader()</code> method.
      * 
      * @param doc The SOAP envelope as <code>Document</code>
      * @param cr An instance of the Crypto API to handle keystore and certificates
      * @param secHeader The security header that will hold the Signature. This is used
      *                   to construct namespace prefixes for Signature. This method
      * @throws WSSecurityException
      */
     public void prepare(Document doc, Crypto cr, WSSecHeader secHeader)
         throws WSSecurityException {
         //
         // Gather some info about the document to process and store it for
         // retrieval
         //
         crypto = cr;
         document = doc;
         wsDocInfo = new WSDocInfo(doc);
         wsDocInfo.setCrypto(cr);
         securityHeader = secHeader.getSecurityHeader();
         
         //
         // At first get the security token (certificate) according to the parameters.
         //
         X509Certificate[] certs = getSigningCerts();
 
         try {
             C14NMethodParameterSpec c14nSpec = null;
             if (getWsConfig().isWsiBSPCompliant() && canonAlgo.equals(WSConstants.C14N_EXCL_OMIT_COMMENTS)) {
                 List<String> prefixes = 
                     getInclusivePrefixes(secHeader.getSecurityHeader(), false);
                 c14nSpec = new ExcC14NParameterSpec(prefixes);
             }
             
            c14nMethod = signatureFactory.newCanonicalizationMethod(canonAlgo, c14nSpec);
         } catch (Exception ex) {
             log.error("", ex);
             throw new WSSecurityException(
                 WSSecurityException.FAILED_SIGNATURE, "noXMLSig", null, ex
             );
         }
 
         keyInfoUri = getWsConfig().getIdAllocator().createSecureId("KI-", keyInfo);
         if (!useCustomSecRef) {
             secRef = new SecurityTokenReference(doc);
             strUri = getWsConfig().getIdAllocator().createSecureId("STR-", secRef);
             secRef.setID(strUri);
             
             //
             // Get an initialized XMLSignature element.
             //
             
             //
             // Prepare and setup the token references for this Signature
             //
             switch (keyIdentifierType) {
             case WSConstants.BST_DIRECT_REFERENCE:
                 Reference ref = new Reference(document);
                 ref.setURI("#" + certUri);
                 if (!useSingleCert) {
                     bstToken = new PKIPathSecurity(document);
                     ((PKIPathSecurity) bstToken).setX509Certificates(certs, crypto);
                     secRef.addTokenType(PKIPathSecurity.PKI_TYPE);
                 } else {
                     bstToken = new X509Security(document);
                     ((X509Security) bstToken).setX509Certificate(certs[0]);
                 }
                 ref.setValueType(bstToken.getValueType());
                 secRef.setReference(ref);
                 bstToken.setID(certUri);
                 wsDocInfo.addTokenElement(bstToken.getElement(), false);
                 break;
     
             case WSConstants.ISSUER_SERIAL:
                 String issuer = certs[0].getIssuerX500Principal().getName();
                 java.math.BigInteger serialNumber = certs[0].getSerialNumber();
                 DOMX509IssuerSerial domIssuerSerial = 
                     new DOMX509IssuerSerial(doc, issuer, serialNumber);
                 DOMX509Data domX509Data = new DOMX509Data(doc, domIssuerSerial);
                 secRef.setX509Data(domX509Data);
                 break;
     
             case WSConstants.X509_KEY_IDENTIFIER:
                 secRef.setKeyIdentifier(certs[0]);
                 break;
     
             case WSConstants.SKI_KEY_IDENTIFIER:
                 secRef.setKeyIdentifierSKI(certs[0], crypto);
                 break;
     
             case WSConstants.THUMBPRINT_IDENTIFIER:
                 secRef.setKeyIdentifierThumb(certs[0]);
                 break;
                 
             case WSConstants.ENCRYPTED_KEY_SHA1_IDENTIFIER:
                 if (encrKeySha1value != null) {
                     secRef.setKeyIdentifierEncKeySHA1(encrKeySha1value);
                 } else {
                     byte[] digestBytes = WSSecurityUtil.generateDigest(secretKey);
                     secRef.setKeyIdentifierEncKeySHA1(Base64.encode(digestBytes));
                 }
                 secRef.addTokenType(WSConstants.WSS_ENC_KEY_VALUE_TYPE);
                 break;
     
             case WSConstants.CUSTOM_SYMM_SIGNING :
                 Reference refCust = new Reference(document);
                 if (WSConstants.WSS_SAML_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.addTokenType(WSConstants.WSS_SAML_TOKEN_TYPE);
                     refCust.setValueType(customTokenValueType);
                 } else if (WSConstants.WSS_SAML2_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.addTokenType(WSConstants.WSS_SAML2_TOKEN_TYPE);
                 } else if (WSConstants.WSS_ENC_KEY_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.addTokenType(WSConstants.WSS_ENC_KEY_VALUE_TYPE);
                     refCust.setValueType(customTokenValueType);
                 } else if (KerberosSecurity.isKerberosToken(customTokenValueType)) {
                     secRef.addTokenType(customTokenValueType);
                     refCust.setValueType(customTokenValueType);
                 } else {
                     refCust.setValueType(customTokenValueType);
                 }
                 refCust.setURI("#" + customTokenId);
                 secRef.setReference(refCust);
                 break;
     
             case WSConstants.CUSTOM_SYMM_SIGNING_DIRECT :
                 Reference refCustd = new Reference(document);
                 if (WSConstants.WSS_SAML_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.addTokenType(WSConstants.WSS_SAML_TOKEN_TYPE);
                     refCustd.setValueType(customTokenValueType);
                 } else if (WSConstants.WSS_SAML2_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.addTokenType(WSConstants.WSS_SAML2_TOKEN_TYPE);
                 } else if (WSConstants.WSS_ENC_KEY_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.addTokenType(WSConstants.WSS_ENC_KEY_VALUE_TYPE);
                     refCustd.setValueType(customTokenValueType);
                 } else if (KerberosSecurity.isKerberosToken(customTokenValueType)) {
                     secRef.addTokenType(customTokenValueType);
                     refCustd.setValueType(customTokenValueType);
                 } else {
                     refCustd.setValueType(customTokenValueType);
                 }
                 refCustd.setURI(customTokenId);
                 secRef.setReference(refCustd);
                 break;
                 
             case WSConstants.CUSTOM_KEY_IDENTIFIER:
                 if (WSConstants.WSS_SAML_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.setKeyIdentifier(customTokenValueType, customTokenId);
                     secRef.addTokenType(WSConstants.WSS_SAML_TOKEN_TYPE);
                 } else if (WSConstants.WSS_SAML2_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.setKeyIdentifier(customTokenValueType, customTokenId);
                     secRef.addTokenType(WSConstants.WSS_SAML2_TOKEN_TYPE);
                 } else if (WSConstants.WSS_ENC_KEY_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.setKeyIdentifier(customTokenValueType, customTokenId, true);
                     secRef.addTokenType(WSConstants.WSS_ENC_KEY_VALUE_TYPE);
                 } else if (SecurityTokenReference.ENC_KEY_SHA1_URI.equals(customTokenValueType)) {
                     secRef.setKeyIdentifier(customTokenValueType, customTokenId, true);
                     secRef.addTokenType(WSConstants.WSS_ENC_KEY_VALUE_TYPE);
                 } else if (WSConstants.WSS_KRB_KI_VALUE_TYPE.equals(customTokenValueType)) {
                     secRef.setKeyIdentifier(customTokenValueType, customTokenId, true);
                     secRef.addTokenType(WSConstants.WSS_GSS_KRB_V5_AP_REQ);
                 } 
                 break;
                 
             case WSConstants.KEY_VALUE:
                 java.security.PublicKey publicKey = certs[0].getPublicKey();
                 
                 try {
                     KeyValue keyValue = keyInfoFactory.newKeyValue(publicKey);
                     keyInfo = 
                         keyInfoFactory.newKeyInfo(
                             java.util.Collections.singletonList(keyValue), keyInfoUri
                         );
                 } catch (java.security.KeyException ex) {
                     log.error("", ex);
                     throw new WSSecurityException(
                         WSSecurityException.FAILED_SIGNATURE, "noXMLSig", null, ex
                     );
                 }
                 break;
             default:
                 throw new WSSecurityException(WSSecurityException.FAILURE, "unsupportedKeyId");
             }
         }
         
         if (keyIdentifierType != WSConstants.KEY_VALUE) {
             XMLStructure structure = new DOMStructure(secRef.getElement());
             wsDocInfo.addTokenElement(secRef.getElement(), false);
             keyInfo = 
                 keyInfoFactory.newKeyInfo(
                     java.util.Collections.singletonList(structure), keyInfoUri
                 );
         }
     }
     
     
     /**
      * Builds a signed soap envelope.
      * 
      * This is a convenience method and for backward compatibility. The method
      * creates a Signature and puts it into the Security header. It does so by
      * calling the single functions in order to perform a <i>one shot signature</i>.
      * This method is compatible with the build method of the previous version
      * with the exception of the additional WSSecHeader parameter.
      * 
      * @param doc The unsigned SOAP envelope as <code>Document</code>
      * @param cr An instance of the Crypto API to handle keystore and certificates
      * @param secHeader the security header element to hold the encrypted key element.
      * @return A signed SOAP envelope as <code>Document</code>
      * @throws WSSecurityException
      */
     public Document build(Document doc, Crypto cr, WSSecHeader secHeader)
         throws WSSecurityException {
         doDebug = log.isDebugEnabled();
 
         if (doDebug) {
             log.debug("Beginning signing...");
         }
 
         prepare(doc, cr, secHeader);
         if (parts == null) {
             parts = new ArrayList<WSEncryptionPart>(1);
             String soapNamespace = WSSecurityUtil.getSOAPNamespace(doc.getDocumentElement());
             WSEncryptionPart encP = 
                 new WSEncryptionPart(
                     WSConstants.ELEM_BODY, 
                     soapNamespace, 
                     "Content"
                 );
             parts.add(encP);
         } else {
             for (WSEncryptionPart part : parts) {
                 if ("STRTransform".equals(part.getName()) && part.getId() == null) {
                     part.setId(strUri);
                 }
             }
         }
 
         List<javax.xml.crypto.dsig.Reference> referenceList = 
             addReferencesToSign(parts, secHeader);
 
         computeSignature(referenceList);
         
         //
         // if we have a BST prepend it in front of the Signature according to
         // strict layout rules.
         //
         if (bstToken != null) {
             prependBSTElementToHeader(secHeader);
         }
 
         return doc;
     }
     
     
     /**
      * This method adds references to the Signature.
      * 
      * @param references The list of references to sign
      * @param secHeader The Security Header
      * @throws WSSecurityException
      */
     public List<javax.xml.crypto.dsig.Reference> addReferencesToSign(
         List<WSEncryptionPart> references, 
         WSSecHeader secHeader
     ) throws WSSecurityException {
         return 
             addReferencesToSign(
                 document, 
                 references,
                 wsDocInfo,
                 signatureFactory, 
                 secHeader, 
                 getWsConfig(), 
                 digestAlgo
             );
     }
 
     /**
      * Returns the SignatureElement.
      * The method can be called any time after <code>prepare()</code>.
      * @return The DOM Element of the signature.
      */
     public Element getSignatureElement() {
         return
             WSSecurityUtil.getDirectChildElement(
                 securityHeader,
                 WSConstants.SIG_LN,
                 WSConstants.SIG_NS
             );
     }
     
     /**
      * Prepend the BinarySecurityToken to the elements already in the Security
      * header.
      * 
      * The method can be called any time after <code>prepare()</code>.
      * This allows to insert the BST element at any position in the Security
      * header.
      * 
      * @param secHeader The security header
      */
     public void prependBSTElementToHeader(WSSecHeader secHeader) {
         if (bstToken != null) {
             WSSecurityUtil.prependChildElement(secHeader.getSecurityHeader(), bstToken.getElement());
         }
         bstToken = null;
     }
 
     /**
      * Append the BinarySecurityToken to the security header. 
      * @param secHeader The security header
      */
     public void appendBSTElementToHeader(WSSecHeader secHeader) {
         if (bstToken != null) {
             Element secHeaderElement = secHeader.getSecurityHeader();
             secHeaderElement.appendChild(bstToken.getElement());
         }
         bstToken = null;
     }
     
     /**
      * Compute the Signature over the references. The signature element will be 
      * prepended to the security header.
      * 
      * This method can be called any time after the references were set. See
      * <code>addReferencesToSign()</code>.
      * 
      * @param referenceList The list of references to sign
      * 
      * @throws WSSecurityException
      */
     public void computeSignature(
         List<javax.xml.crypto.dsig.Reference> referenceList 
     ) throws WSSecurityException {
         computeSignature(referenceList, true, null);
     }
     
     /**
      * Compute the Signature over the references.
      * 
      * This method can be called any time after the references were set. See
      * <code>addReferencesToSign()</code>.
      * 
      * @param referenceList The list of references to sign
      * @param prepend Whether to prepend the signature element to the security header
      * @param siblingElement If prepending, then prepend before this sibling Element
      * 
      * @throws WSSecurityException
      */
     public void computeSignature(
         List<javax.xml.crypto.dsig.Reference> referenceList, 
         boolean prepend,
         Element siblingElement
     ) throws WSSecurityException {
         try {
             java.security.Key key;
             if (secretKey == null) {
                 key = crypto.getPrivateKey(user, password);
             } else {
                 key = WSSecurityUtil.prepareSecretKey(sigAlgo, secretKey);
             }
             SignatureMethod signatureMethod = 
                 signatureFactory.newSignatureMethod(sigAlgo, null);
             SignedInfo signedInfo = 
                 signatureFactory.newSignedInfo(c14nMethod, signatureMethod, referenceList);
             
             sig = signatureFactory.newXMLSignature(
                     signedInfo, 
                     keyInfo,
                     null,
                     getWsConfig().getIdAllocator().createId("SIG-", null),
                     null);
             
             //
             // Figure out where to insert the signature element
             //
             XMLSignContext signContext = null;
             if (prepend) {
                 if (siblingElement == null) {
                     Node child = securityHeader.getFirstChild();
                     while (child != null && child.getNodeType() != Node.ELEMENT_NODE) {
                         child = child.getNextSibling();
                     } 
                     siblingElement = (Element)child;
                 }
                 if (siblingElement == null) {
                     signContext = new DOMSignContext(key, securityHeader);
                 } else {
                     signContext = new DOMSignContext(key, securityHeader, siblingElement);
                 }
             } else {
                 signContext = new DOMSignContext(key, securityHeader);
             }
             
             signContext.putNamespacePrefix(WSConstants.SIG_NS, WSConstants.SIG_PREFIX);
             if (WSConstants.C14N_EXCL_OMIT_COMMENTS.equals(canonAlgo)) {
                 signContext.putNamespacePrefix(
                     WSConstants.C14N_EXCL_OMIT_COMMENTS, 
                     WSConstants.C14N_EXCL_OMIT_COMMENTS_PREFIX
                 );
             }
             signContext.setProperty(STRTransform.TRANSFORM_WS_DOC_INFO, wsDocInfo);
             wsDocInfo.setCallbackLookup(callbackLookup);
             
             // Add the elements to sign to the Signature Context
             wsDocInfo.setTokensOnContext((DOMSignContext)signContext);
             if (secRef != null && secRef.getElement() != null) {
                 WSSecurityUtil.storeElementInContext((DOMSignContext)signContext, secRef.getElement());
             }
             sig.sign(signContext);
             
             signatureValue = sig.getSignatureValue().getValue();
         } catch (Exception ex) {
             log.error(ex);
             throw new WSSecurityException(
                 WSSecurityException.FAILED_SIGNATURE, null, null, ex
             );
         }
     }
     
     /**
      * Set the single cert flag.
      * 
      * @param useSingleCert
      */
     public void setUseSingleCertificate(boolean useSingleCert) {
         this.useSingleCert = useSingleCert;
     }
 
     /**
      * Get the single cert flag.
      * 
      * @return A boolean if single certificate is set.
      */
     public boolean isUseSingleCertificate() {
         return useSingleCert;
     }
 
     /**
      * Set the name (uri) of the signature encryption algorithm to use.
      * 
      * If the algorithm is not set then an automatic detection of the signature
      * algorithm to use is performed during the <code>prepare()</code>
      * method. Refer to WSConstants which algorithms are supported.
      * 
      * @param algo the name of the signature algorithm
      * @see WSConstants#RSA
      * @see WSConstants#DSA
      */
     public void setSignatureAlgorithm(String algo) {
         sigAlgo = algo;
     }
 
     /**
      * Get the name (uri) of the signature algorithm that is being used.
      * 
      * Call this method after <code>prepare</code> to get the information
      * which signature algorithm was automatically detected if no signature
      * algorithm was preset.
      * 
      * @return the identifier URI of the signature algorithm
      */
     public String getSignatureAlgorithm() {
         return sigAlgo;
     }
 
     /**
      * Set the canonicalization method to use.
      * 
      * If the canonicalization method is not set then the recommended Exclusive
      * XML Canonicalization is used by default. Refer to WSConstants which
      * algorithms are supported.
      * 
      * @param algo Is the name of the signature algorithm
      * @see WSConstants#C14N_OMIT_COMMENTS
      * @see WSConstants#C14N_WITH_COMMENTS
      * @see WSConstants#C14N_EXCL_OMIT_COMMENTS
      * @see WSConstants#C14N_EXCL_WITH_COMMENTS
      */
     public void setSigCanonicalization(String algo) {
         canonAlgo = algo;
     }
 
     /**
      * Get the canonicalization method.
      * 
      * If the canonicalization method was not set then Exclusive XML
      * Canonicalization is used by default.
      * 
      * @return The string describing the canonicalization algorithm.
      */
     public String getSigCanonicalization() {
         return canonAlgo;
     }
 
     /**
      * @return the digest algorithm to use
      */
     public String getDigestAlgo() {
         return digestAlgo;
     }
 
     /**
      * Set the string that defines which digest algorithm to use. 
      * The default is Constants.ALGO_ID_DIGEST_SHA1.
      * 
      * @param digestAlgo the digestAlgo to set
      */
     public void setDigestAlgo(String digestAlgo) {
         this.digestAlgo = digestAlgo;
     }
     
     
     /**
      * Returns the computed Signature value.
      * 
      * Call this method after <code>computeSignature()</code> or <code>build()</code>
      * methods were called.
      * 
      * @return Returns the signatureValue.
      */
     public byte[] getSignatureValue() {
         return signatureValue;
     }
 
     /**
      * Get the id generated during <code>prepare()</code>.
      * 
      * Returns the the value of wsu:Id attribute of the Signature element.
      * 
      * @return Return the wsu:Id of this token or null if <code>prepare()</code>
      *         was not called before.
      */
     public String getId() {
         if (sig == null) {
             return null;
         }
         return sig.getId();
     }
     
     /**
      * Get the id of the BST generated  during <code>prepare()</code>.
      * 
      * @return Returns the the value of wsu:Id attribute of the 
      * BinaruSecurityToken element.
      */
     public String getBSTTokenId() {
         if (bstToken == null) {
             return null;
         }
         return bstToken.getID();
     }
     
     /**
      * Set the secret key to use
      * @param secretKey the secret key to use
      */
     public void setSecretKey(byte[] secretKey) {
         this.secretKey = secretKey;
     }
 
     /**
      * Set the custom token value type to use
      * @param customTokenValueType the custom token value type to use
      */
     public void setCustomTokenValueType(String customTokenValueType) {
         this.customTokenValueType = customTokenValueType;
     }
 
     /**
      * Set the custom token id
      * @param customTokenId the custom token id
      */
     public void setCustomTokenId(String customTokenId) {
         this.customTokenId = customTokenId;
     }
 
     /**
      * Set the encrypted key sha1 value
      * @param encrKeySha1value the encrypted key sha1 value
      */
     public void setEncrKeySha1value(String encrKeySha1value) {
         this.encrKeySha1value = encrKeySha1value;
     }
     
     /**
      * Set the X509 Certificate to use
      * @param cer the X509 Certificate to use
      */
     public void setX509Certificate(X509Certificate cer) {
         this.useThisCert = cer;
     }
     
     /**
      * Returns the BST Token element.
      * The method can be called any time after <code>prepare()</code>.
      * @return the BST Token element
      */
     public Element getBinarySecurityTokenElement() {
         if (bstToken != null) {
             return bstToken.getElement();
         }
         return null;
     }
     
     /**
      * @return the URI associated with the SecurityTokenReference
      * (must be called after {@link #prepare(Document, Crypto, WSSecHeader)}
      */
     public String getSecurityTokenReferenceURI() {
         return strUri;
     }
     
     /**
      * Get the SecurityTokenReference to be used in the KeyInfo element.
      */
     public SecurityTokenReference getSecurityTokenReference() {
         return secRef;
     }
     
     /**
      * Set the SecurityTokenReference to be used in the KeyInfo element. If this
      * method is not called, a SecurityTokenRefence will be generated.
      */
     public void setSecurityTokenReference(SecurityTokenReference secRef) {
         useCustomSecRef = true;
         this.secRef = secRef;
     }
 
     /**
      * Set up the X509 Certificate(s) for signing.
      */
     private X509Certificate[] getSigningCerts() throws WSSecurityException {
         X509Certificate[] certs = null;
         if (!(keyIdentifierType == WSConstants.CUSTOM_SYMM_SIGNING
             || keyIdentifierType == WSConstants.CUSTOM_SYMM_SIGNING_DIRECT
             || keyIdentifierType == WSConstants.ENCRYPTED_KEY_SHA1_IDENTIFIER
             || keyIdentifierType == WSConstants.CUSTOM_KEY_IDENTIFIER)) {
             if (useThisCert == null) {
                 CryptoType cryptoType = new CryptoType(CryptoType.TYPE.ALIAS);
                 cryptoType.setAlias(user);
                 certs = crypto.getX509Certificates(cryptoType);
             } else {
                 certs = new X509Certificate[] {useThisCert};
             }
             if (certs == null || certs.length <= 0) {
                 throw new WSSecurityException(
                         WSSecurityException.FAILURE,
                         "noUserCertsFound", 
                         new Object[] { user, "signature" }
                 );
             }
             certUri = getWsConfig().getIdAllocator().createSecureId("X509-", certs[0]);  
             //
             // If no signature algorithm was set try to detect it according to the
             // data stored in the certificate.
             //
             if (sigAlgo == null) {
                 String pubKeyAlgo = certs[0].getPublicKey().getAlgorithm();
                 log.debug("Automatic signature algorithm detection: " + pubKeyAlgo);
                 if (pubKeyAlgo.equalsIgnoreCase("DSA")) {
                     sigAlgo = WSConstants.DSA;
                 } else if (pubKeyAlgo.equalsIgnoreCase("RSA")) {
                     sigAlgo = WSConstants.RSA;
                 } else {
                     throw new WSSecurityException(
                         WSSecurityException.FAILURE,
                         "unknownSignatureAlgorithm",
                         new Object[] {pubKeyAlgo}
                     );
                 }
             }
         }
         return certs;
     }
     
 }