    001/*
    002 * Licensed to the Apache Software Foundation (ASF) under one or more
    003 * contributor license agreements.  See the NOTICE file distributed with
    004 * this work for additional information regarding copyright ownership.
    005 * The ASF licenses this file to You under the Apache License, Version 2.0
    006 * (the "License"); you may not use this file except in compliance with
    007 * the License.  You may obtain a copy of the License at
    008 *
    009 *      http://www.apache.org/licenses/LICENSE-2.0
    010 *
    011 * Unless required by applicable law or agreed to in writing, software
    012 * distributed under the License is distributed on an "AS IS" BASIS,
    013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    014 * See the License for the specific language governing permissions and
    015 * limitations under the License.
    016 */
    017
    018package org.apache.commons.net.pop3;
    019
    020import java.io.IOException;
    021import java.security.InvalidKeyException;
    022import java.security.NoSuchAlgorithmException;
    023import java.security.spec.InvalidKeySpecException;
    024import java.util.Base64;
    025
    026import javax.crypto.Mac;
    027import javax.crypto.spec.SecretKeySpec;
    028
    029/**
    030 * A POP3 Cilent class with protocol and authentication extensions support (RFC2449 and RFC2195).
    031 *
    032 * @see POP3Client
    033 * @since 3.0
    034 */
    035public class ExtendedPOP3Client extends POP3SClient {
    036
    037    /** {@link Mac} algorithm. */
    038    private static final String MAC_ALGORITHM = "HmacMD5";
    039
    040    /**
    041     * The enumeration of currently-supported authentication methods.
    042     */
    043    public enum AUTH_METHOD {
    044
    045        /** The standardized (RFC4616) PLAIN method, which sends the password unencrypted (insecure). */
    046        PLAIN("PLAIN"),
    047
    048        /** The standardized (RFC2195) CRAM-MD5 method, which doesn't send the password (secure). */
    049        CRAM_MD5("CRAM-MD5");
    050
    051        private final String methodName;
    052
    053        AUTH_METHOD(final String methodName) {
    054            this.methodName = methodName;
    055        }
    056
    057        /**
    058         * Gets the name of the given authentication method suitable for the server.
    059         *
    060         * @return The name of the given authentication method suitable for the server.
    061         */
    062        public final String getAuthName() {
    063            return this.methodName;
    064        }
    065    }
    066
    067    /**
    068     * The default ExtendedPOP3Client constructor. Creates a new Extended POP3 Client.
    069     *
    070     * @throws NoSuchAlgorithmException on error
    071     */
    072    public ExtendedPOP3Client() throws NoSuchAlgorithmException {
    073    }
    074
    075    /**
    076     * Authenticate to the POP3 server by sending the AUTH command with the selected mechanism, using the given user and the given password.
    077     *
    078     * @param method   the {@link AUTH_METHOD} to use
    079     * @param user the user name
    080     * @param password the password
    081     * @return True if successfully completed, false if not.
    082     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    083     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    084     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    085     * @throws InvalidKeySpecException  If the CRAM hash algorithm failed to use the given password.
    086     */
    087    public boolean auth(final AUTH_METHOD method, final String user, final String password)
    088            throws IOException, NoSuchAlgorithmException, InvalidKeyException, InvalidKeySpecException {
    089        if (sendCommand(POP3Command.AUTH, method.getAuthName()) != POP3Reply.OK_INT) {
    090            return false;
    091        }
    092
    093        switch (method) {
    094        case PLAIN:
    095            // the server sends an empty response ("+ "), so we don't have to read it.
    096            return sendCommand(
    097                    new String(Base64.getEncoder().encode(("\000" + user + "\000" + password).getBytes(getCharset())), getCharset())) == POP3Reply.OK;
    098        case CRAM_MD5:
    099            // get the CRAM challenge
    100            final byte[] serverChallenge = Base64.getDecoder().decode(getReplyString().substring(2).trim());
    101            // get the Mac instance
    102            final Mac hmacMd5 = Mac.getInstance(MAC_ALGORITHM);
    103            hmacMd5.init(new SecretKeySpec(password.getBytes(getCharset()), MAC_ALGORITHM));
    104            // compute the result:
    105            final byte[] hmacResult = convertToHexString(hmacMd5.doFinal(serverChallenge)).getBytes(getCharset());
    106            // join the byte arrays to form the reply
    107            final byte[] userNameBytes = user.getBytes(getCharset());
    108            final byte[] toEncode = new byte[userNameBytes.length + 1 /* the space */ + hmacResult.length];
    109            System.arraycopy(userNameBytes, 0, toEncode, 0, userNameBytes.length);
    110            toEncode[userNameBytes.length] = ' ';
    111            System.arraycopy(hmacResult, 0, toEncode, userNameBytes.length + 1, hmacResult.length);
    112            // send the reply and read the server code:
    113            return sendCommand(Base64.getEncoder().encodeToString(toEncode)) == POP3Reply.OK;
    114        default:
    115            return false;
    116        }
    117    }
    118
    119    /**
    120     * Converts the given byte array to a String containing the hex values of the bytes. For example, the byte 'A' will be converted to '41', because this is
    121     * the ASCII code (and the byte value) of the capital letter 'A'.
    122     *
    123     * @param a The byte array to convert.
    124     * @return The resulting String of hex codes.
    125     */
    126    private String convertToHexString(final byte[] a) {
    127        final StringBuilder result = new StringBuilder(a.length * 2);
    128        for (final byte element : a) {
    129            if ((element & 0x0FF) <= 15) {
    130                result.append("0");
    131            }
    132            result.append(Integer.toHexString(element & 0x0FF));
    133        }
    134        return result.toString();
    135    }
    136}