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Java example source code file (DigestScheme.java)

This example source code file (DigestScheme.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java tags/keywords

authenticationexception, basicnamevaluepair, credentials, header, hexadecimal, http, illegalstateexception, malformedchallengeexception, md5, messagedigest, qop_auth_int, qop_missing, security, string, stringbuilder, util

The DigestScheme.java example source code

/*
 * ====================================================================
 *
 *  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.annotation.NotThreadSafe;

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;

/**
 * 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}
 * </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;
    
    //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 if Digest authorization has been processed,
     *   <tt>false 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
     */
    public String getSchemeName() {
        return "digest";
    }

    /**
     * Returns <tt>false. Digest authentication scheme is request based.
     * 
     * @return <tt>false.
     */
    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");   
        }

        String digAlg = algorithm;
        if (digAlg.equalsIgnoreCase("MD5-sess")) {
            digAlg = "MD5";
        }
        MessageDigest digester = createMessageDigest(digAlg);

        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")) {
            // H( unq(username-value) ":" unq(realm-value) ":" passwd )
            //      ":" unq(nonce-value)
            //      ":" unq(cnonce-value)

            algorithm = "MD5";
            String cnonce = getCnonce();
            
            String tmp2 = encode(digester.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();
        }
        String hasha1 = encode(digester.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 hasha2 = encode(digester.digest(EncodingUtils.getAsciiBytes(a2)));

        // 3.2.2.1
        String serverDigestValue;
        if (qopVariant == QOP_MISSING) {
            StringBuilder tmp2 = new StringBuilder(
                    hasha1.length() + nonce.length() + hasha1.length());
            tmp2.append(hasha1);
            tmp2.append(':');
            tmp2.append(nonce);
            tmp2.append(':');
            tmp2.append(hasha2);
            serverDigestValue = tmp2.toString();
        } else {
            String qopOption = getQopVariantString();
            String cnonce = getCnonce();
            
            StringBuilder tmp2 = new StringBuilder(hasha1.length() + nonce.length()
                + NC.length() + cnonce.length() + qopOption.length() + hasha2.length() + 5);
            tmp2.append(hasha1);
            tmp2.append(':');
            tmp2.append(nonce);
            tmp2.append(':');
            tmp2.append(NC);
            tmp2.append(':');
            tmp2.append(cnonce);
            tmp2.append(':');
            tmp2.append(qopOption);
            tmp2.append(':');
            tmp2.append(hasha2); 
            serverDigestValue = tmp2.toString();
        }

        String serverDigest =
            encode(digester.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) {
        
        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(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 according to RFC 2617.
     * 
     * @param binaryData array containing the digest
     * @return encoded MD5, or <CODE>null if encoding failed
     */
    private 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.
     * @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;
    }
}

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