    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;
    024
    025import javax.crypto.Mac;
    026import javax.crypto.spec.SecretKeySpec;
    027
    028import org.apache.commons.net.util.Base64;
    029
    030/**
    031 * A POP3 Cilent class with protocol and authentication extensions support (RFC2449 and RFC2195).
    032 *
    033 * @see POP3Client
    034 * @since 3.0
    035 */
    036public class ExtendedPOP3Client extends POP3SClient {
    037    /**
    038     * The enumeration of currently-supported authentication methods.
    039     */
    040    public enum AUTH_METHOD {
    041        /** The standarised (RFC4616) PLAIN method, which sends the password unencrypted (insecure). */
    042        PLAIN("PLAIN"),
    043
    044        /** The standarised (RFC2195) CRAM-MD5 method, which doesn't send the password (secure). */
    045        CRAM_MD5("CRAM-MD5");
    046
    047        private final String methodName;
    048
    049        AUTH_METHOD(final String methodName) {
    050            this.methodName = methodName;
    051        }
    052
    053        /**
    054         * Gets the name of the given authentication method suitable for the server.
    055         *
    056         * @return The name of the given authentication method suitable for the server.
    057         */
    058        public final String getAuthName() {
    059            return this.methodName;
    060        }
    061    }
    062
    063    /**
    064     * The default ExtendedPOP3Client constructor. Creates a new Extended POP3 Client.
    065     *
    066     * @throws NoSuchAlgorithmException on error
    067     */
    068    public ExtendedPOP3Client() throws NoSuchAlgorithmException {
    069    }
    070
    071    /**
    072     * Authenticate to the POP3 server by sending the AUTH command with the selected mechanism, using the given username and the given password.
    073     * <p>
    074     *
    075     * @param method   the {@link AUTH_METHOD} to use
    076     * @param username the user name
    077     * @param password the password
    078     * @return True if successfully completed, false if not.
    079     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    080     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    081     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    082     * @throws InvalidKeySpecException  If the CRAM hash algorithm failed to use the given password.
    083     */
    084    public boolean auth(final AUTH_METHOD method, final String username, final String password)
    085            throws IOException, NoSuchAlgorithmException, InvalidKeyException, InvalidKeySpecException {
    086        if (sendCommand(POP3Command.AUTH, method.getAuthName()) != POP3Reply.OK_INT) {
    087            return false;
    088        }
    089
    090        switch (method) {
    091        case PLAIN:
    092            // the server sends an empty response ("+ "), so we don't have to read it.
    093            return sendCommand(new String(Base64.encodeBase64(("\000" + username + "\000" + password).getBytes(getCharset())), getCharset())) == POP3Reply.OK;
    094        case CRAM_MD5:
    095            // get the CRAM challenge
    096            final byte[] serverChallenge = Base64.decodeBase64(getReplyString().substring(2).trim());
    097            // get the Mac instance
    098            final Mac hmac_md5 = Mac.getInstance("HmacMD5");
    099            hmac_md5.init(new SecretKeySpec(password.getBytes(getCharset()), "HmacMD5"));
    100            // compute the result:
    101            final byte[] hmacResult = convertToHexString(hmac_md5.doFinal(serverChallenge)).getBytes(getCharset());
    102            // join the byte arrays to form the reply
    103            final byte[] usernameBytes = username.getBytes(getCharset());
    104            final byte[] toEncode = new byte[usernameBytes.length + 1 /* the space */ + hmacResult.length];
    105            System.arraycopy(usernameBytes, 0, toEncode, 0, usernameBytes.length);
    106            toEncode[usernameBytes.length] = ' ';
    107            System.arraycopy(hmacResult, 0, toEncode, usernameBytes.length + 1, hmacResult.length);
    108            // send the reply and read the server code:
    109            return sendCommand(Base64.encodeBase64StringUnChunked(toEncode)) == POP3Reply.OK;
    110        default:
    111            return false;
    112        }
    113    }
    114
    115    /**
    116     * 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
    117     * the ASCII code (and the byte value) of the capital letter 'A'.
    118     *
    119     * @param a The byte array to convert.
    120     * @return The resulting String of hex codes.
    121     */
    122    private String convertToHexString(final byte[] a) {
    123        final StringBuilder result = new StringBuilder(a.length * 2);
    124        for (final byte element : a) {
    125            if ((element & 0x0FF) <= 15) {
    126                result.append("0");
    127            }
    128            result.append(Integer.toHexString(element & 0x0FF));
    129        }
    130        return result.toString();
    131    }
    132}