src/org/apache/http/impl/auth/DigestScheme.java - platform/external/apache-http - Git at Google

 /*
  * $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk/module-client/src/main/java/org/apache/http/impl/auth/DigestScheme.java $
  * $Revision: 659595 $
  * $Date: 2008-05-23 09:47:14 -0700 (Fri, 23 May 2008) $
  *
  * ====================================================================
  *
  *  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.
  * ====================================================================
  *
  * This software consists of voluntary contributions made by many
  * individuals on behalf of the Apache Software Foundation.  For more
  * information on the Apache Software Foundation, please see
  * <http://www.apache.org/>.
  *
  */

 package org.apache.http.impl.auth;

 import java.security.MessageDigest;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.StringTokenizer;

 import org.apache.http.Header;
 import org.apache.http.HttpRequest;
 import org.apache.http.auth.AuthenticationException;
 import org.apache.http.auth.Credentials;
 import org.apache.http.auth.AUTH;
 import org.apache.http.auth.MalformedChallengeException;
 import org.apache.http.auth.params.AuthParams;
 import org.apache.http.message.BasicNameValuePair;
 import org.apache.http.message.BasicHeaderValueFormatter;
 import org.apache.http.message.BufferedHeader;
 import org.apache.http.util.CharArrayBuffer;
 import org.apache.http.util.EncodingUtils;

 /**
  * <p>
  * Digest authentication scheme as defined in RFC 2617.
  * Both MD5 (default) and MD5-sess are supported.
  * Currently only qop=auth or no qop is supported. qop=auth-int
  * is unsupported. If auth and auth-int are provided, auth is
  * used.
  * </p>
  * <p>
  * Credential charset is configured via the
  * {@link org.apache.http.auth.params.AuthPNames#CREDENTIAL_CHARSET
  *        credential charset} parameter.
  * Since the digest username is included as clear text in the generated
  * Authentication header, the charset of the username must be compatible
  * with the
  * {@link org.apache.http.params.CoreProtocolPNames#HTTP_ELEMENT_CHARSET
  *        http element charset}.
  * </p>
  *
  * @author <a href="mailto:remm@apache.org">Remy Maucherat</a>
  * @author Rodney Waldhoff
  * @author <a href="mailto:jsdever@apache.org">Jeff Dever</a>
  * @author Ortwin Glueck
  * @author Sean C. Sullivan
  * @author <a href="mailto:adrian@ephox.com">Adrian Sutton</a>
  * @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
  * @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
  *
  * @since 4.0
  *
  * @deprecated Please use {@link java.net.URL#openConnection} instead.
  *     Please visit <a href="http://android-developers.blogspot.com/2011/09/androids-http-clients.html">this webpage</a>
  *     for further details.
  */

 @Deprecated
 public class DigestScheme extends RFC2617Scheme {

     /**
      * Hexa values used when creating 32 character long digest in HTTP DigestScheme
      * in case of authentication.
      *
      * @see #encode(byte[])
      */
     private static final char[] HEXADECIMAL = {
         '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
         'e', 'f'
     };

     /** Whether the digest authentication process is complete */
     private boolean complete;

     //TODO: supply a real nonce-count, currently a server will interprete a repeated request as a replay
     private static final String NC = "00000001"; //nonce-count is always 1
     private static final int QOP_MISSING = 0;
     private static final int QOP_AUTH_INT = 1;
     private static final int QOP_AUTH = 2;

     private int qopVariant = QOP_MISSING;
     private String cnonce;

     /**
      * Default constructor for the digest authetication scheme.
      */
     public DigestScheme() {
         super();
         this.complete = false;
     }

     /**
      * Processes the Digest challenge.
      *
      * @param header the challenge header
      *
      * @throws MalformedChallengeException is thrown if the authentication challenge
      * is malformed
      */
     @Override
     public void processChallenge(
             final Header header) throws MalformedChallengeException {
         super.processChallenge(header);

         if (getParameter("realm") == null) {
             throw new MalformedChallengeException("missing realm in challange");
         }
         if (getParameter("nonce") == null) {
             throw new MalformedChallengeException("missing nonce in challange");
         }

         boolean unsupportedQop = false;
         // qop parsing
         String qop = getParameter("qop");
         if (qop != null) {
             StringTokenizer tok = new StringTokenizer(qop,",");
             while (tok.hasMoreTokens()) {
                 String variant = tok.nextToken().trim();
                 if (variant.equals("auth")) {
                     qopVariant = QOP_AUTH;
                     break; //that's our favourite, because auth-int is unsupported
                 } else if (variant.equals("auth-int")) {
                     qopVariant = QOP_AUTH_INT;
                 } else {
                     unsupportedQop = true;
                 }
             }
         }

         if (unsupportedQop && (qopVariant == QOP_MISSING)) {
             throw new MalformedChallengeException("None of the qop methods is supported");
         }
         // Reset cnonce
         this.cnonce = null;
         this.complete = true;
     }

     /**
      * Tests if the Digest authentication process has been completed.
      *
      * @return <tt>true</tt> if Digest authorization has been processed,
      *   <tt>false</tt> otherwise.
      */
     public boolean isComplete() {
         String s = getParameter("stale");
         if ("true".equalsIgnoreCase(s)) {
             return false;
         } else {
             return this.complete;
         }
     }

     /**
      * Returns textual designation of the digest authentication scheme.
      *
      * @return <code>digest</code>
      */
     public String getSchemeName() {
         return "digest";
     }

     /**
      * Returns <tt>false</tt>. Digest authentication scheme is request based.
      *
      * @return <tt>false</tt>.
      */
     public boolean isConnectionBased() {
         return false;
     }

     public void overrideParamter(final String name, final String value) {
         getParameters().put(name, value);
     }

     private String getCnonce() {
         if (this.cnonce == null) {
             this.cnonce = createCnonce();
         }
         return this.cnonce;
     }

     /**
      * Produces a digest authorization string for the given set of
      * {@link Credentials}, method name and URI.
      *
      * @param credentials A set of credentials to be used for athentication
      * @param request    The request being authenticated
      *
      * @throws org.apache.http.auth.InvalidCredentialsException if authentication credentials
      *         are not valid or not applicable for this authentication scheme
      * @throws AuthenticationException if authorization string cannot
      *   be generated due to an authentication failure
      *
      * @return a digest authorization string
      */
     public Header authenticate(
             final Credentials credentials,
             final HttpRequest request) throws AuthenticationException {

         if (credentials == null) {
             throw new IllegalArgumentException("Credentials may not be null");
         }
         if (request == null) {
             throw new IllegalArgumentException("HTTP request may not be null");
         }

         // Add method name and request-URI to the parameter map
         getParameters().put("methodname", request.getRequestLine().getMethod());
         getParameters().put("uri", request.getRequestLine().getUri());
         String charset = getParameter("charset");
         if (charset == null) {
             charset = AuthParams.getCredentialCharset(request.getParams());
             getParameters().put("charset", charset);
         }
         String digest = createDigest(credentials);
         return createDigestHeader(credentials, digest);
     }

     private static MessageDigest createMessageDigest(
             final String digAlg) throws UnsupportedDigestAlgorithmException {
         try {
             return MessageDigest.getInstance(digAlg);
         } catch (Exception e) {
             throw new UnsupportedDigestAlgorithmException(
               "Unsupported algorithm in HTTP Digest authentication: "
                + digAlg);
         }
     }

     /**
      * Creates an MD5 response digest.
      *
      * @return The created digest as string. This will be the response tag's
      *         value in the Authentication HTTP header.
      * @throws AuthenticationException when MD5 is an unsupported algorithm
      */
     private String createDigest(final Credentials credentials) throws AuthenticationException {
         // Collecting required tokens
         String uri = getParameter("uri");
         String realm = getParameter("realm");
         String nonce = getParameter("nonce");
         String method = getParameter("methodname");
         String algorithm = getParameter("algorithm");
         if (uri == null) {
             throw new IllegalStateException("URI may not be null");
         }
         if (realm == null) {
             throw new IllegalStateException("Realm may not be null");
         }
         if (nonce == null) {
             throw new IllegalStateException("Nonce may not be null");
         }
         // If an algorithm is not specified, default to MD5.
         if (algorithm == null) {
             algorithm = "MD5";
         }
         // If an charset is not specified, default to ISO-8859-1.
         String charset = getParameter("charset");
         if (charset == null) {
             charset = "ISO-8859-1";
         }

         if (qopVariant == QOP_AUTH_INT) {
             throw new AuthenticationException(
                 "Unsupported qop in HTTP Digest authentication");
         }

         MessageDigest md5Helper = createMessageDigest("MD5");

         String uname = credentials.getUserPrincipal().getName();
         String pwd = credentials.getPassword();

         // 3.2.2.2: Calculating digest
         StringBuilder tmp = new StringBuilder(uname.length() + realm.length() + pwd.length() + 2);
         tmp.append(uname);
         tmp.append(':');
         tmp.append(realm);
         tmp.append(':');
         tmp.append(pwd);
         // unq(username-value) ":" unq(realm-value) ":" passwd
         String a1 = tmp.toString();

         //a1 is suitable for MD5 algorithm
         if(algorithm.equalsIgnoreCase("MD5-sess")) { // android-changed: ignore case
             // H( unq(username-value) ":" unq(realm-value) ":" passwd )
             //      ":" unq(nonce-value)
             //      ":" unq(cnonce-value)

             String cnonce = getCnonce();

             String tmp2=encode(md5Helper.digest(EncodingUtils.getBytes(a1, charset)));
             StringBuilder tmp3 = new StringBuilder(tmp2.length() + nonce.length() + cnonce.length() + 2);
             tmp3.append(tmp2);
             tmp3.append(':');
             tmp3.append(nonce);
             tmp3.append(':');
             tmp3.append(cnonce);
             a1 = tmp3.toString();
         } else if (!algorithm.equalsIgnoreCase("MD5")) { // android-changed: ignore case
             throw new AuthenticationException("Unhandled algorithm " + algorithm + " requested");
         }
         String md5a1 = encode(md5Helper.digest(EncodingUtils.getBytes(a1, charset)));

         String a2 = null;
         if (qopVariant == QOP_AUTH_INT) {
             // Unhandled qop auth-int
             //we do not have access to the entity-body or its hash
             //TODO: add Method ":" digest-uri-value ":" H(entity-body)
         } else {
             a2 = method + ':' + uri;
         }
         String md5a2 = encode(md5Helper.digest(EncodingUtils.getAsciiBytes(a2)));

         // 3.2.2.1
         String serverDigestValue;
         if (qopVariant == QOP_MISSING) {
             StringBuilder tmp2 = new StringBuilder(md5a1.length() + nonce.length() + md5a2.length());
             tmp2.append(md5a1);
             tmp2.append(':');
             tmp2.append(nonce);
             tmp2.append(':');
             tmp2.append(md5a2);
             serverDigestValue = tmp2.toString();
         } else {
             String qopOption = getQopVariantString();
             String cnonce = getCnonce();

             StringBuilder tmp2 = new StringBuilder(md5a1.length() + nonce.length()
                 + NC.length() + cnonce.length() + qopOption.length() + md5a2.length() + 5);
             tmp2.append(md5a1);
             tmp2.append(':');
             tmp2.append(nonce);
             tmp2.append(':');
             tmp2.append(NC);
             tmp2.append(':');
             tmp2.append(cnonce);
             tmp2.append(':');
             tmp2.append(qopOption);
             tmp2.append(':');
             tmp2.append(md5a2);
             serverDigestValue = tmp2.toString();
         }

         String serverDigest =
             encode(md5Helper.digest(EncodingUtils.getAsciiBytes(serverDigestValue)));

         return serverDigest;
     }

     /**
      * Creates digest-response header as defined in RFC2617.
      *
      * @param credentials User credentials
      * @param digest The response tag's value as String.
      *
      * @return The digest-response as String.
      */
     private Header createDigestHeader(
             final Credentials credentials,
             final String digest) throws AuthenticationException {

         CharArrayBuffer buffer = new CharArrayBuffer(128);
         if (isProxy()) {
             buffer.append(AUTH.PROXY_AUTH_RESP);
         } else {
             buffer.append(AUTH.WWW_AUTH_RESP);
         }
         buffer.append(": Digest ");

         String uri = getParameter("uri");
         String realm = getParameter("realm");
         String nonce = getParameter("nonce");
         String opaque = getParameter("opaque");
         String response = digest;
         String algorithm = getParameter("algorithm");

         String uname = credentials.getUserPrincipal().getName();

         List<BasicNameValuePair> params = new ArrayList<BasicNameValuePair>(20);
         params.add(new BasicNameValuePair("username", uname));
         params.add(new BasicNameValuePair("realm", realm));
         params.add(new BasicNameValuePair("nonce", nonce));
         params.add(new BasicNameValuePair("uri", uri));
         params.add(new BasicNameValuePair("response", response));

         if (qopVariant != QOP_MISSING) {
             params.add(new BasicNameValuePair("qop", getQopVariantString()));
             params.add(new BasicNameValuePair("nc", NC));
             params.add(new BasicNameValuePair("cnonce", getCnonce()));
         }
         if (algorithm != null) {
             params.add(new BasicNameValuePair("algorithm", algorithm));
         }
         if (opaque != null) {
             params.add(new BasicNameValuePair("opaque", opaque));
         }

         for (int i = 0; i < params.size(); i++) {
             BasicNameValuePair param = params.get(i);
             if (i > 0) {
                 buffer.append(", ");
             }
             boolean noQuotes = "nc".equals(param.getName()) ||
                                "qop".equals(param.getName());
             BasicHeaderValueFormatter.DEFAULT
                 .formatNameValuePair(buffer, param, !noQuotes);
         }
         return new BufferedHeader(buffer);
     }

     private String getQopVariantString() {
         String qopOption;
         if (qopVariant == QOP_AUTH_INT) {
             qopOption = "auth-int";
         } else {
             qopOption = "auth";
         }
         return qopOption;
     }

     /**
      * Encodes the 128 bit (16 bytes) MD5 digest into a 32 characters long
      * <CODE>String</CODE> according to RFC 2617.
      *
      * @param binaryData array containing the digest
      * @return encoded MD5, or <CODE>null</CODE> if encoding failed
      */
     private static String encode(byte[] binaryData) {
         if (binaryData.length != 16) {
             return null;
         }

         char[] buffer = new char[32];
         for (int i = 0; i < 16; i++) {
             int low = (binaryData[i] & 0x0f);
             int high = ((binaryData[i] & 0xf0) >> 4);
             buffer[i * 2] = HEXADECIMAL[high];
             buffer[(i * 2) + 1] = HEXADECIMAL[low];
         }

         return new String(buffer);
     }


     /**
      * Creates a random cnonce value based on the current time.
      *
      * @return The cnonce value as String.
      * @throws UnsupportedDigestAlgorithmException if MD5 algorithm is not supported.
      */
     public static String createCnonce() {
         String cnonce;

         MessageDigest md5Helper = createMessageDigest("MD5");

         cnonce = Long.toString(System.currentTimeMillis());
         cnonce = encode(md5Helper.digest(EncodingUtils.getAsciiBytes(cnonce)));

         return cnonce;
     }
 }
	/*
	* $HeadURL: http://svn.apache.org/repos/asf/httpcomponents/httpclient/trunk/module-client/src/main/java/org/apache/http/impl/auth/DigestScheme.java $
	* $Revision: 659595 $
	* $Date: 2008-05-23 09:47:14 -0700 (Fri, 23 May 2008) $
	*
	* ====================================================================
	*
	* 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.
	* ====================================================================
	*
	* This software consists of voluntary contributions made by many
	* individuals on behalf of the Apache Software Foundation. For more
	* information on the Apache Software Foundation, please see
	* <http://www.apache.org/>.
	*
	*/

	package org.apache.http.impl.auth;

	import java.security.MessageDigest;
	import java.util.ArrayList;
	import java.util.List;
	import java.util.StringTokenizer;

	import org.apache.http.Header;
	import org.apache.http.HttpRequest;
	import org.apache.http.auth.AuthenticationException;
	import org.apache.http.auth.Credentials;
	import org.apache.http.auth.AUTH;
	import org.apache.http.auth.MalformedChallengeException;
	import org.apache.http.auth.params.AuthParams;
	import org.apache.http.message.BasicNameValuePair;
	import org.apache.http.message.BasicHeaderValueFormatter;
	import org.apache.http.message.BufferedHeader;
	import org.apache.http.util.CharArrayBuffer;
	import org.apache.http.util.EncodingUtils;

	/**
	* <p>
	* Digest authentication scheme as defined in RFC 2617.
	* Both MD5 (default) and MD5-sess are supported.
	* Currently only qop=auth or no qop is supported. qop=auth-int
	* is unsupported. If auth and auth-int are provided, auth is
	* used.
	* </p>
	* <p>
	* Credential charset is configured via the
	* {@link org.apache.http.auth.params.AuthPNames#CREDENTIAL_CHARSET
	* credential charset} parameter.
	* Since the digest username is included as clear text in the generated
	* Authentication header, the charset of the username must be compatible
	* with the
	* {@link org.apache.http.params.CoreProtocolPNames#HTTP_ELEMENT_CHARSET
	* http element charset}.
	* </p>
	*
	* @author <a href="mailto:remm@apache.org">Remy Maucherat</a>
	* @author Rodney Waldhoff
	* @author <a href="mailto:jsdever@apache.org">Jeff Dever</a>
	* @author Ortwin Glueck
	* @author Sean C. Sullivan
	* @author <a href="mailto:adrian@ephox.com">Adrian Sutton</a>
	* @author <a href="mailto:mbowler@GargoyleSoftware.com">Mike Bowler</a>
	* @author <a href="mailto:oleg at ural.ru">Oleg Kalnichevski</a>
	*
	* @since 4.0
	*
	* @deprecated Please use {@link java.net.URL#openConnection} instead.
	* Please visit <a href="http://android-developers.blogspot.com/2011/09/androids-http-clients.html">this webpage</a>
	* for further details.
	*/

	@Deprecated
	public class DigestScheme extends RFC2617Scheme {

	/**
	* Hexa values used when creating 32 character long digest in HTTP DigestScheme
	* in case of authentication.
	*
	* @see #encode(byte[])
	*/
	private static final char[] HEXADECIMAL = {
	'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
	'e', 'f'
	};

	/** Whether the digest authentication process is complete */
	private boolean complete;

	//TODO: supply a real nonce-count, currently a server will interprete a repeated request as a replay
	private static final String NC = "00000001"; //nonce-count is always 1
	private static final int QOP_MISSING = 0;
	private static final int QOP_AUTH_INT = 1;
	private static final int QOP_AUTH = 2;

	private int qopVariant = QOP_MISSING;
	private String cnonce;

	/**
	* Default constructor for the digest authetication scheme.
	*/
	public DigestScheme() {
	super();
	this.complete = false;
	}

	/**
	* Processes the Digest challenge.
	*
	* @param header the challenge header
	*
	* @throws MalformedChallengeException is thrown if the authentication challenge
	* is malformed
	*/
	@Override
	public void processChallenge(
	final Header header) throws MalformedChallengeException {
	super.processChallenge(header);

	if (getParameter("realm") == null) {
	throw new MalformedChallengeException("missing realm in challange");
	}
	if (getParameter("nonce") == null) {
	throw new MalformedChallengeException("missing nonce in challange");
	}

	boolean unsupportedQop = false;
	// qop parsing
	String qop = getParameter("qop");
	if (qop != null) {
	StringTokenizer tok = new StringTokenizer(qop,",");
	while (tok.hasMoreTokens()) {
	String variant = tok.nextToken().trim();
	if (variant.equals("auth")) {
	qopVariant = QOP_AUTH;
	break; //that's our favourite, because auth-int is unsupported
	} else if (variant.equals("auth-int")) {
	qopVariant = QOP_AUTH_INT;
	} else {
	unsupportedQop = true;
	}
	}
	}

	if (unsupportedQop && (qopVariant == QOP_MISSING)) {
	throw new MalformedChallengeException("None of the qop methods is supported");
	}
	// Reset cnonce
	this.cnonce = null;
	this.complete = true;
	}

	/**
	* Tests if the Digest authentication process has been completed.
	*
	* @return <tt>true</tt> if Digest authorization has been processed,
	* <tt>false</tt> otherwise.
	*/
	public boolean isComplete() {
	String s = getParameter("stale");
	if ("true".equalsIgnoreCase(s)) {
	return false;
	} else {
	return this.complete;
	}
	}

	/**
	* Returns textual designation of the digest authentication scheme.
	*
	* @return <code>digest</code>
	*/
	public String getSchemeName() {
	return "digest";
	}

	/**
	* Returns <tt>false</tt>. Digest authentication scheme is request based.
	*
	* @return <tt>false</tt>.
	*/
	public boolean isConnectionBased() {
	return false;
	}

	public void overrideParamter(final String name, final String value) {
	getParameters().put(name, value);
	}

	private String getCnonce() {
	if (this.cnonce == null) {
	this.cnonce = createCnonce();
	}
	return this.cnonce;
	}

	/**
	* Produces a digest authorization string for the given set of
	* {@link Credentials}, method name and URI.
	*
	* @param credentials A set of credentials to be used for athentication
	* @param request The request being authenticated
	*
	* @throws org.apache.http.auth.InvalidCredentialsException if authentication credentials
	* are not valid or not applicable for this authentication scheme
	* @throws AuthenticationException if authorization string cannot
	* be generated due to an authentication failure
	*
	* @return a digest authorization string
	*/
	public Header authenticate(
	final Credentials credentials,
	final HttpRequest request) throws AuthenticationException {

	if (credentials == null) {
	throw new IllegalArgumentException("Credentials may not be null");
	}
	if (request == null) {
	throw new IllegalArgumentException("HTTP request may not be null");
	}

	// Add method name and request-URI to the parameter map
	getParameters().put("methodname", request.getRequestLine().getMethod());
	getParameters().put("uri", request.getRequestLine().getUri());
	String charset = getParameter("charset");
	if (charset == null) {
	charset = AuthParams.getCredentialCharset(request.getParams());
	getParameters().put("charset", charset);
	}
	String digest = createDigest(credentials);
	return createDigestHeader(credentials, digest);
	}

	private static MessageDigest createMessageDigest(
	final String digAlg) throws UnsupportedDigestAlgorithmException {
	try {
	return MessageDigest.getInstance(digAlg);
	} catch (Exception e) {
	throw new UnsupportedDigestAlgorithmException(
	"Unsupported algorithm in HTTP Digest authentication: "
	+ digAlg);
	}
	}

	/**
	* Creates an MD5 response digest.
	*
	* @return The created digest as string. This will be the response tag's
	* value in the Authentication HTTP header.
	* @throws AuthenticationException when MD5 is an unsupported algorithm
	*/
	private String createDigest(final Credentials credentials) throws AuthenticationException {
	// Collecting required tokens
	String uri = getParameter("uri");
	String realm = getParameter("realm");
	String nonce = getParameter("nonce");
	String method = getParameter("methodname");
	String algorithm = getParameter("algorithm");
	if (uri == null) {
	throw new IllegalStateException("URI may not be null");
	}
	if (realm == null) {
	throw new IllegalStateException("Realm may not be null");
	}
	if (nonce == null) {
	throw new IllegalStateException("Nonce may not be null");
	}
	// If an algorithm is not specified, default to MD5.
	if (algorithm == null) {
	algorithm = "MD5";
	}
	// If an charset is not specified, default to ISO-8859-1.
	String charset = getParameter("charset");
	if (charset == null) {
	charset = "ISO-8859-1";
	}

	if (qopVariant == QOP_AUTH_INT) {
	throw new AuthenticationException(
	"Unsupported qop in HTTP Digest authentication");
	}

	MessageDigest md5Helper = createMessageDigest("MD5");

	String uname = credentials.getUserPrincipal().getName();
	String pwd = credentials.getPassword();

	// 3.2.2.2: Calculating digest
	StringBuilder tmp = new StringBuilder(uname.length() + realm.length() + pwd.length() + 2);
	tmp.append(uname);
	tmp.append(':');
	tmp.append(realm);
	tmp.append(':');
	tmp.append(pwd);
	// unq(username-value) ":" unq(realm-value) ":" passwd
	String a1 = tmp.toString();

	//a1 is suitable for MD5 algorithm
	if(algorithm.equalsIgnoreCase("MD5-sess")) { // android-changed: ignore case
	// H( unq(username-value) ":" unq(realm-value) ":" passwd )
	// ":" unq(nonce-value)
	// ":" unq(cnonce-value)

	String cnonce = getCnonce();

	String tmp2=encode(md5Helper.digest(EncodingUtils.getBytes(a1, charset)));
	StringBuilder tmp3 = new StringBuilder(tmp2.length() + nonce.length() + cnonce.length() + 2);
	tmp3.append(tmp2);
	tmp3.append(':');
	tmp3.append(nonce);
	tmp3.append(':');
	tmp3.append(cnonce);
	a1 = tmp3.toString();
	} else if (!algorithm.equalsIgnoreCase("MD5")) { // android-changed: ignore case
	throw new AuthenticationException("Unhandled algorithm " + algorithm + " requested");
	}
	String md5a1 = encode(md5Helper.digest(EncodingUtils.getBytes(a1, charset)));

	String a2 = null;
	if (qopVariant == QOP_AUTH_INT) {
	// Unhandled qop auth-int
	//we do not have access to the entity-body or its hash
	//TODO: add Method ":" digest-uri-value ":" H(entity-body)
	} else {
	a2 = method + ':' + uri;
	}
	String md5a2 = encode(md5Helper.digest(EncodingUtils.getAsciiBytes(a2)));

	// 3.2.2.1
	String serverDigestValue;
	if (qopVariant == QOP_MISSING) {
	StringBuilder tmp2 = new StringBuilder(md5a1.length() + nonce.length() + md5a2.length());
	tmp2.append(md5a1);
	tmp2.append(':');
	tmp2.append(nonce);
	tmp2.append(':');
	tmp2.append(md5a2);
	serverDigestValue = tmp2.toString();
	} else {
	String qopOption = getQopVariantString();
	String cnonce = getCnonce();

	StringBuilder tmp2 = new StringBuilder(md5a1.length() + nonce.length()
	+ NC.length() + cnonce.length() + qopOption.length() + md5a2.length() + 5);
	tmp2.append(md5a1);
	tmp2.append(':');
	tmp2.append(nonce);
	tmp2.append(':');
	tmp2.append(NC);
	tmp2.append(':');
	tmp2.append(cnonce);
	tmp2.append(':');
	tmp2.append(qopOption);
	tmp2.append(':');
	tmp2.append(md5a2);
	serverDigestValue = tmp2.toString();
	}

	String serverDigest =
	encode(md5Helper.digest(EncodingUtils.getAsciiBytes(serverDigestValue)));

	return serverDigest;
	}

	/**
	* Creates digest-response header as defined in RFC2617.
	*
	* @param credentials User credentials
	* @param digest The response tag's value as String.
	*
	* @return The digest-response as String.
	*/
	private Header createDigestHeader(
	final Credentials credentials,
	final String digest) throws AuthenticationException {

	CharArrayBuffer buffer = new CharArrayBuffer(128);
	if (isProxy()) {
	buffer.append(AUTH.PROXY_AUTH_RESP);
	} else {
	buffer.append(AUTH.WWW_AUTH_RESP);
	}
	buffer.append(": Digest ");

	String uri = getParameter("uri");
	String realm = getParameter("realm");
	String nonce = getParameter("nonce");
	String opaque = getParameter("opaque");
	String response = digest;
	String algorithm = getParameter("algorithm");

	String uname = credentials.getUserPrincipal().getName();

	List<BasicNameValuePair> params = new ArrayList<BasicNameValuePair>(20);
	params.add(new BasicNameValuePair("username", uname));
	params.add(new BasicNameValuePair("realm", realm));
	params.add(new BasicNameValuePair("nonce", nonce));
	params.add(new BasicNameValuePair("uri", uri));
	params.add(new BasicNameValuePair("response", response));

	if (qopVariant != QOP_MISSING) {
	params.add(new BasicNameValuePair("qop", getQopVariantString()));
	params.add(new BasicNameValuePair("nc", NC));
	params.add(new BasicNameValuePair("cnonce", getCnonce()));
	}
	if (algorithm != null) {
	params.add(new BasicNameValuePair("algorithm", algorithm));
	}
	if (opaque != null) {
	params.add(new BasicNameValuePair("opaque", opaque));
	}

	for (int i = 0; i < params.size(); i++) {
	BasicNameValuePair param = params.get(i);
	if (i > 0) {
	buffer.append(", ");
	}
	boolean noQuotes = "nc".equals(param.getName()) \|\|
	"qop".equals(param.getName());
	BasicHeaderValueFormatter.DEFAULT
	.formatNameValuePair(buffer, param, !noQuotes);
	}
	return new BufferedHeader(buffer);
	}

	private String getQopVariantString() {
	String qopOption;
	if (qopVariant == QOP_AUTH_INT) {
	qopOption = "auth-int";
	} else {
	qopOption = "auth";
	}
	return qopOption;
	}

	/**
	* Encodes the 128 bit (16 bytes) MD5 digest into a 32 characters long
	* <CODE>String</CODE> according to RFC 2617.
	*
	* @param binaryData array containing the digest
	* @return encoded MD5, or <CODE>null</CODE> if encoding failed
	*/
	private static String encode(byte[] binaryData) {
	if (binaryData.length != 16) {
	return null;
	}

	char[] buffer = new char[32];
	for (int i = 0; i < 16; i++) {
	int low = (binaryData[i] & 0x0f);
	int high = ((binaryData[i] & 0xf0) >> 4);
	buffer[i * 2] = HEXADECIMAL[high];
	buffer[(i * 2) + 1] = HEXADECIMAL[low];
	}

	return new String(buffer);
	}


	/**
	* Creates a random cnonce value based on the current time.
	*
	* @return The cnonce value as String.
	* @throws UnsupportedDigestAlgorithmException if MD5 algorithm is not supported.
	*/
	public static String createCnonce() {
	String cnonce;

	MessageDigest md5Helper = createMessageDigest("MD5");

	cnonce = Long.toString(System.currentTimeMillis());
	cnonce = encode(md5Helper.digest(EncodingUtils.getAsciiBytes(cnonce)));

	return cnonce;
	}
	}