/*
    * ====================================================================
    *
    *  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.io.IOException;
  import java.security.MessageDigest;
  import java.security.SecureRandom;
  import java.util.ArrayList;
  import java.util.Formatter;
  import java.util.HashSet;
  import java.util.List;
  import java.util.Locale;
  import java.util.Set;
  import java.util.StringTokenizer;
  
  import org.apache.http.annotation.NotThreadSafe;
  
  import org.apache.http.Header;
  import org.apache.http.HttpEntity;
  import org.apache.http.HttpEntityEnclosingRequest;
  import org.apache.http.HttpRequest;
  import org.apache.http.auth.AuthenticationException;
  import org.apache.http.auth.ChallengeState;
  import org.apache.http.auth.ContextAwareAuthScheme;
  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.protocol.BasicHttpContext;
  import org.apache.http.protocol.HttpContext;
  import org.apache.http.util.CharArrayBuffer;
  import org.apache.http.util.EncodingUtils;
  
  /**
   * 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>
   * Credential charset is configured via the
   * {@link org.apache.http.auth.params.AuthPNames#CREDENTIAL_CHARSET}
   * parameter of the HTTP request.
   * <p>
   * 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>
   * The following parameters can be used to customize the behavior of this
   * class:
   * <ul>
   *  <li>{@link org.apache.http.auth.params.AuthPNames#CREDENTIAL_CHARSET}</li>
   * </ul>
   *
   * @since 4.0
   */
  @NotThreadSafe
  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;
 
     private static final int QOP_UNKNOWN = -1;
     private static final int QOP_MISSING = 0;
     private static final int QOP_AUTH_INT = 1;
     private static final int QOP_AUTH = 2;
 
     private String lastNonce;
     private long nounceCount;
     private String cnonce;
     private String a1;
     private String a2;
 
     /**
      * Creates an instance of <tt>DigestScheme</tt> with the given challenge
      * state.
      *
      * @since 4.2
      */
     public DigestScheme(final ChallengeState challengeState) {
         super(challengeState);
         this.complete = false;
     }
 
     public DigestScheme() {
         this(null);
     }
 
     /**
      * 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);
         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);
     }
 
     /**
      * @deprecated (4.2) Use {@link ContextAwareAuthScheme#authenticate(Credentials, HttpRequest, org.apache.http.protocol.HttpContext)}
      */
     @Deprecated 
     public Header authenticate(
             final Credentials credentials, final HttpRequest request) throws AuthenticationException {
         return authenticate(credentials, request, new BasicHttpContext());
     }
 
     /**
      * 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
      */
     @Override
     public Header authenticate(
             final Credentials credentials,
             final HttpRequest request,
             final HttpContext context) 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");
         }
         if (getParameter("realm") == null) {
             throw new AuthenticationException("missing realm in challenge");
         }
         if (getParameter("nonce") == null) {
             throw new AuthenticationException("missing nonce in challenge");
         }
         // 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);
         }
         return createDigestHeader(credentials, request);
     }
 
     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 digest-response header as defined in RFC2617.
      *
      * @param credentials User credentials
      *
      * @return The digest-response as String.
      */
     private Header createDigestHeader(
             final Credentials credentials,
             final HttpRequest request) throws AuthenticationException {
         String uri = getParameter("uri");
         String realm = getParameter("realm");
         String nonce = getParameter("nonce");
         String opaque = getParameter("opaque");
         String method = getParameter("methodname");
         String algorithm = getParameter("algorithm");
 
         Set<String> qopset = new HashSet<String>(8);
         int qop = QOP_UNKNOWN;
         String qoplist = getParameter("qop");
         if (qoplist != null) {
             StringTokenizer tok = new StringTokenizer(qoplist, ",");
             while (tok.hasMoreTokens()) {
                 String variant = tok.nextToken().trim();
                 qopset.add(variant.toLowerCase(Locale.US));
             }
             if (request instanceof HttpEntityEnclosingRequest && qopset.contains("auth-int")) {
                 qop = QOP_AUTH_INT;
             } else if (qopset.contains("auth")) {
                 qop = QOP_AUTH;
             }
         } else {
             qop = QOP_MISSING;
         }
 
         if (qop == QOP_UNKNOWN) {
             throw new AuthenticationException("None of the qop methods is supported: " + qoplist);
         }
 
         // If an algorithm is not specified, default to MD5.
         if (algorithm == null) {
             algorithm = "MD5";
         }
         String charset = getParameter("charset");
         if (charset == null) {
             charset = "ISO-8859-1";
         }
 
         String digAlg = algorithm;
         if (digAlg.equalsIgnoreCase("MD5-sess")) {
             digAlg = "MD5";
         }
 
         MessageDigest digester;
         try {
             digester = createMessageDigest(digAlg);
         } catch (UnsupportedDigestAlgorithmException ex) {
             throw new AuthenticationException("Unsuppported digest algorithm: " + digAlg);
         }
 
         String uname = credentials.getUserPrincipal().getName();
         String pwd = credentials.getPassword();
 
         if (nonce.equals(this.lastNonce)) {
             nounceCount++;
         } else {
             nounceCount = 1;
             cnonce = null;
             lastNonce = nonce;
         }
         StringBuilder sb = new StringBuilder(256);
         Formatter formatter = new Formatter(sb, Locale.US);
         formatter.format("%08x", nounceCount);
         String nc = sb.toString();
 
         if (cnonce == null) {
             cnonce = createCnonce();
         }
 
         a1 = null;
         a2 = null;
         // 3.2.2.2: Calculating digest
         if (algorithm.equalsIgnoreCase("MD5-sess")) {
             // H( unq(username-value) ":" unq(realm-value) ":" passwd )
             //      ":" unq(nonce-value)
             //      ":" unq(cnonce-value)
 
             // calculated one per session
             sb.setLength(0);
             sb.append(uname).append(':').append(realm).append(':').append(pwd);
             String checksum = encode(digester.digest(EncodingUtils.getBytes(sb.toString(), charset)));
             sb.setLength(0);
             sb.append(checksum).append(':').append(nonce).append(':').append(cnonce);
             a1 = sb.toString();
         } else {
             // unq(username-value) ":" unq(realm-value) ":" passwd
             sb.setLength(0);
             sb.append(uname).append(':').append(realm).append(':').append(pwd);
             a1 = sb.toString();
         }
 
         String hasha1 = encode(digester.digest(EncodingUtils.getBytes(a1, charset)));
 
         if (qop == QOP_AUTH) {
             // Method ":" digest-uri-value
             a2 = method + ':' + uri;
         } else if (qop == QOP_AUTH_INT) {
             // Method ":" digest-uri-value ":" H(entity-body)
             HttpEntity entity = null;
             if (request instanceof HttpEntityEnclosingRequest) {
                 entity = ((HttpEntityEnclosingRequest) request).getEntity();
             }
             if (entity != null && !entity.isRepeatable()) {
                 // If the entity is not repeatable, try falling back onto QOP_AUTH
                 if (qopset.contains("auth")) {
                     qop = QOP_AUTH;
                     a2 = method + ':' + uri;
                 } else {
                     throw new AuthenticationException("Qop auth-int cannot be used with " +
                             "a non-repeatable entity");
                 }
             } else {
                 HttpEntityDigester entityDigester = new HttpEntityDigester(digester);
                 try {
                     if (entity != null) {
                         entity.writeTo(entityDigester);
                     }
                     entityDigester.close();
                 } catch (IOException ex) {
                     throw new AuthenticationException("I/O error reading entity content", ex);
                 }
                 a2 = method + ':' + uri + ':' + encode(entityDigester.getDigest());
             }
         } else {
             a2 = method + ':' + uri;
         }
 
         String hasha2 = encode(digester.digest(EncodingUtils.getBytes(a2, charset)));
 
         // 3.2.2.1
 
         String digestValue;
         if (qop == QOP_MISSING) {
             sb.setLength(0);
             sb.append(hasha1).append(':').append(nonce).append(':').append(hasha2);
             digestValue = sb.toString();
         } else {
             sb.setLength(0);
             sb.append(hasha1).append(':').append(nonce).append(':').append(nc).append(':')
                 .append(cnonce).append(':').append(qop == QOP_AUTH_INT ? "auth-int" : "auth")
                 .append(':').append(hasha2);
             digestValue = sb.toString();
         }
 
         String digest = encode(digester.digest(EncodingUtils.getAsciiBytes(digestValue)));
 
         CharArrayBuffer buffer = new CharArrayBuffer(128);
         if (isProxy()) {
             buffer.append(AUTH.PROXY_AUTH_RESP);
         } else {
             buffer.append(AUTH.WWW_AUTH_RESP);
         }
         buffer.append(": Digest ");
 
         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", digest));
 
         if (qop != QOP_MISSING) {
             params.add(new BasicNameValuePair("qop", qop == QOP_AUTH_INT ? "auth-int" : "auth"));
             params.add(new BasicNameValuePair("nc", nc));
             params.add(new BasicNameValuePair("cnonce", cnonce));
         }
         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);
     }
 
     String getCnonce() {
         return cnonce;
     }
 
     String getA1() {
         return a1;
     }
 
     String getA2() {
         return a2;
     }
 
     /**
      * 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
      */
     static String encode(byte[] binaryData) {
         int n = binaryData.length;
         char[] buffer = new char[n * 2];
         for (int i = 0; i < n; 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.
      */
     public static String createCnonce() {
         SecureRandom rnd = new SecureRandom();
         byte[] tmp = new byte[8];
         rnd.nextBytes(tmp);
         return encode(tmp);
     }
 
     @Override
     public String toString() {
         StringBuilder builder = new StringBuilder();
         builder.append("DIGEST [complete=").append(complete)
                 .append(", nonce=").append(lastNonce)
                 .append(", nc=").append(nounceCount)
                 .append("]");
         return builder.toString();
     }
 
 }