    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 *      https://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.util.Base64;
    024
    025import javax.crypto.Mac;
    026import javax.crypto.spec.SecretKeySpec;
    027
    028/**
    029 * A POP3 Client class with protocol and authentication extensions support (RFC2449 and RFC2195).
    030 *
    031 * @see POP3Client
    032 * @since 3.0
    033 */
    034public class ExtendedPOP3Client extends POP3SClient {
    035
    036    /**
    037     * The enumeration of currently-supported authentication methods.
    038     */
    039    public enum AUTH_METHOD {
    040
    041        /** The standardized (RFC4616) PLAIN method, which sends the password unencrypted (insecure). */
    042        PLAIN("PLAIN"),
    043
    044        /** The standardized (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 String getAuthName() {
    059            return methodName;
    060        }
    061    }
    062
    063    /** {@link Mac} algorithm. */
    064    private static final String MAC_ALGORITHM = "HmacMD5";
    065
    066    /**
    067     * The default ExtendedPOP3Client constructor. Creates a new Extended POP3 Client.
    068     *
    069     * @throws NoSuchAlgorithmException Never thrown here.
    070     */
    071    public ExtendedPOP3Client() throws NoSuchAlgorithmException {
    072    }
    073
    074    /**
    075     * Authenticate to the POP3 server by sending the AUTH command with the selected mechanism, using the given user and the given password.
    076     *
    077     * @param method   the {@link AUTH_METHOD} to use
    078     * @param user the user name
    079     * @param password the password
    080     * @return True if successfully completed, false if not.
    081     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    082     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    083     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    084     */
    085    public boolean auth(final AUTH_METHOD method, final String user, final String password)
    086            throws IOException, NoSuchAlgorithmException, InvalidKeyException {
    087        if (sendCommand(POP3Command.AUTH, method.getAuthName()) != POP3Reply.OK_INT) {
    088            return false;
    089        }
    090
    091        switch (method) {
    092        case PLAIN:
    093            // the server sends an empty response ("+ "), so we don't have to read it.
    094            return sendCommand(
    095                    new String(Base64.getEncoder().encode(("\000" + user + "\000" + password).getBytes(getCharset())), getCharset())) == POP3Reply.OK;
    096        case CRAM_MD5:
    097            // get the CRAM challenge
    098            final byte[] serverChallenge = Base64.getDecoder().decode(getReplyString().substring(2).trim());
    099            // get the Mac instance
    100            final Mac hmacMd5 = Mac.getInstance(MAC_ALGORITHM);
    101            hmacMd5.init(new SecretKeySpec(password.getBytes(getCharset()), MAC_ALGORITHM));
    102            // compute the result:
    103            final byte[] hmacResult = convertToHexString(hmacMd5.doFinal(serverChallenge)).getBytes(getCharset());
    104            // join the byte arrays to form the reply
    105            final byte[] userNameBytes = user.getBytes(getCharset());
    106            final byte[] toEncode = new byte[userNameBytes.length + 1 /* the space */ + hmacResult.length];
    107            System.arraycopy(userNameBytes, 0, toEncode, 0, userNameBytes.length);
    108            toEncode[userNameBytes.length] = ' ';
    109            System.arraycopy(hmacResult, 0, toEncode, userNameBytes.length + 1, hmacResult.length);
    110            // send the reply and read the server code:
    111            return sendCommand(Base64.getEncoder().encodeToString(toEncode)) == POP3Reply.OK;
    112        default:
    113            return false;
    114        }
    115    }
    116
    117    /**
    118     * Converts the given byte array to a String containing the hexadecimal values of the bytes. For example, the byte 'A' will be converted to '41', because
    119     * this is the ASCII code (and the byte value) of the capital letter 'A'.
    120     *
    121     * @param a The byte array to convert.
    122     * @return The resulting String of hexadecimal codes.
    123     */
    124    private String convertToHexString(final byte[] a) {
    125        final StringBuilder result = new StringBuilder(a.length * 2);
    126        for (final byte element : a) {
    127            if ((element & 0x0FF) <= 15) {
    128                result.append("0");
    129            }
    130            result.append(Integer.toHexString(element & 0x0FF));
    131        }
    132        return result.toString();
    133    }
    134}