    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.imap;
    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;
    028import javax.net.ssl.SSLContext;
    029
    030/**
    031 * An IMAP Client class with authentication support.
    032 *
    033 * @see IMAPSClient
    034 */
    035public class AuthenticatingIMAPClient extends IMAPSClient {
    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
    047        PLAIN("PLAIN"),
    048        /** The standardized (RFC2195) CRAM-MD5 method, which doesn't send the password (secure). */
    049
    050        CRAM_MD5("CRAM-MD5"),
    051
    052        /** The standardized Microsoft LOGIN method, which sends the password unencrypted (insecure). */
    053        LOGIN("LOGIN"),
    054
    055        /** XOAUTH */
    056        XOAUTH("XOAUTH"),
    057
    058        /** XOAUTH 2 */
    059        XOAUTH2("XOAUTH2");
    060
    061        private final String authName;
    062
    063        AUTH_METHOD(final String name) {
    064            this.authName = name;
    065        }
    066
    067        /**
    068         * Gets the name of the given authentication method suitable for the server.
    069         *
    070         * @return The name of the given authentication method suitable for the server.
    071         */
    072        public final String getAuthName() {
    073            return authName;
    074        }
    075    }
    076
    077    /**
    078     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient. Sets security mode to explicit (isImplicit = false).
    079     */
    080    public AuthenticatingIMAPClient() {
    081        this(DEFAULT_PROTOCOL, false);
    082    }
    083
    084    /**
    085     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    086     *
    087     * @param implicit The security mode (Implicit/Explicit).
    088     */
    089    public AuthenticatingIMAPClient(final boolean implicit) {
    090        this(DEFAULT_PROTOCOL, implicit);
    091    }
    092
    093    /**
    094     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    095     *
    096     * @param implicit The security mode(Implicit/Explicit).
    097     * @param ctx      A pre-configured SSL Context.
    098     */
    099    public AuthenticatingIMAPClient(final boolean implicit, final SSLContext ctx) {
    100        this(DEFAULT_PROTOCOL, implicit, ctx);
    101    }
    102
    103    /**
    104     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    105     *
    106     * @param context A pre-configured SSL Context.
    107     */
    108    public AuthenticatingIMAPClient(final SSLContext context) {
    109        this(false, context);
    110    }
    111
    112    /**
    113     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    114     *
    115     * @param proto the protocol.
    116     */
    117    public AuthenticatingIMAPClient(final String proto) {
    118        this(proto, false);
    119    }
    120
    121    /**
    122     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    123     *
    124     * @param proto    the protocol.
    125     * @param implicit The security mode(Implicit/Explicit).
    126     */
    127    public AuthenticatingIMAPClient(final String proto, final boolean implicit) {
    128        this(proto, implicit, null);
    129    }
    130
    131    /**
    132     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    133     *
    134     * @param proto    the protocol.
    135     * @param implicit The security mode(Implicit/Explicit).
    136     * @param ctx      the context
    137     */
    138    public AuthenticatingIMAPClient(final String proto, final boolean implicit, final SSLContext ctx) {
    139        super(proto, implicit, ctx);
    140    }
    141
    142    /**
    143     * Authenticate to the IMAP server by sending the AUTHENTICATE command with the selected mechanism, using the given user and the given password.
    144     *
    145     * @param method   the method name
    146     * @param user user
    147     * @param password password
    148     * @return True if successfully completed, false if not.
    149     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    150     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    151     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    152     * @throws InvalidKeySpecException  If the CRAM hash algorithm failed to use the given password.
    153     */
    154    public boolean auth(final AuthenticatingIMAPClient.AUTH_METHOD method, final String user, final String password)
    155            throws IOException, NoSuchAlgorithmException, InvalidKeyException, InvalidKeySpecException {
    156        if (!IMAPReply.isContinuation(sendCommand(IMAPCommand.AUTHENTICATE, method.getAuthName()))) {
    157            return false;
    158        }
    159
    160        switch (method) {
    161        case PLAIN: {
    162            // the server sends an empty response ("+ "), so we don't have to read it.
    163            final int result = sendData(Base64.getEncoder().encodeToString(("\000" + user + "\000" + password).getBytes(getCharset())));
    164            if (result == IMAPReply.OK) {
    165                setState(IMAP.IMAPState.AUTH_STATE);
    166            }
    167            return result == IMAPReply.OK;
    168        }
    169        case CRAM_MD5: {
    170            // get the CRAM challenge (after "+ ")
    171            final byte[] serverChallenge = Base64.getDecoder().decode(getReplyString().substring(2).trim());
    172            // get the Mac instance
    173            final Mac hmacMd5 = Mac.getInstance(MAC_ALGORITHM);
    174            hmacMd5.init(new SecretKeySpec(password.getBytes(getCharset()), MAC_ALGORITHM));
    175            // compute the result:
    176            final byte[] hmacResult = convertToHexString(hmacMd5.doFinal(serverChallenge)).getBytes(getCharset());
    177            // join the byte arrays to form the reply
    178            final byte[] usernameBytes = user.getBytes(getCharset());
    179            final byte[] toEncode = new byte[usernameBytes.length + 1 /* the space */ + hmacResult.length];
    180            System.arraycopy(usernameBytes, 0, toEncode, 0, usernameBytes.length);
    181            toEncode[usernameBytes.length] = ' ';
    182            System.arraycopy(hmacResult, 0, toEncode, usernameBytes.length + 1, hmacResult.length);
    183            // send the reply and read the server code:
    184            final int result = sendData(Base64.getEncoder().encodeToString(toEncode));
    185            if (result == IMAPReply.OK) {
    186                setState(IMAP.IMAPState.AUTH_STATE);
    187            }
    188            return result == IMAPReply.OK;
    189        }
    190        case LOGIN: {
    191            // the server sends fixed responses (base64("Username") and
    192            // base64("Password")), so we don't have to read them.
    193            if (sendData(Base64.getEncoder().encodeToString(user.getBytes(getCharset()))) != IMAPReply.CONT) {
    194                return false;
    195            }
    196            final int result = sendData(Base64.getEncoder().encodeToString(password.getBytes(getCharset())));
    197            if (result == IMAPReply.OK) {
    198                setState(IMAP.IMAPState.AUTH_STATE);
    199            }
    200            return result == IMAPReply.OK;
    201        }
    202        case XOAUTH:
    203        case XOAUTH2: {
    204            final int result = sendData(user);
    205            if (result == IMAPReply.OK) {
    206                setState(IMAP.IMAPState.AUTH_STATE);
    207            }
    208            return result == IMAPReply.OK;
    209        }
    210        }
    211        return false; // safety check
    212    }
    213
    214    /**
    215     * Authenticate to the IMAP server by sending the AUTHENTICATE command with the selected mechanism, using the given user and the given password.
    216     *
    217     * @param method   the method name
    218     * @param user user
    219     * @param password password
    220     * @return True if successfully completed, false if not.
    221     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    222     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    223     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    224     * @throws InvalidKeySpecException  If the CRAM hash algorithm failed to use the given password.
    225     */
    226    public boolean authenticate(final AuthenticatingIMAPClient.AUTH_METHOD method, final String user, final String password)
    227            throws IOException, NoSuchAlgorithmException, InvalidKeyException, InvalidKeySpecException {
    228        return auth(method, user, password);
    229    }
    230
    231    /**
    232     * 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
    233     * the ASCII code (and the byte value) of the capital letter 'A'.
    234     *
    235     * @param a The byte array to convert.
    236     * @return The resulting String of hex codes.
    237     */
    238    private String convertToHexString(final byte[] a) {
    239        final StringBuilder result = new StringBuilder(a.length * 2);
    240        for (final byte element : a) {
    241            if ((element & 0x0FF) <= 15) {
    242                result.append("0");
    243            }
    244            result.append(Integer.toHexString(element & 0x0FF));
    245        }
    246        return result.toString();
    247    }
    248}
    249