    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.imap;
    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;
    027import javax.net.ssl.SSLContext;
    028
    029/**
    030 * An IMAP Client class with authentication support.
    031 *
    032 * @see IMAPSClient
    033 */
    034public class AuthenticatingIMAPClient extends IMAPSClient {
    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
    043        PLAIN("PLAIN"),
    044        /** The standardized (RFC2195) CRAM-MD5 method, which doesn't send the password (secure). */
    045
    046        CRAM_MD5("CRAM-MD5"),
    047
    048        /** The standardized Microsoft LOGIN method, which sends the password unencrypted (insecure). */
    049        LOGIN("LOGIN"),
    050
    051        /** XOAUTH */
    052        XOAUTH("XOAUTH"),
    053
    054        /** XOAUTH 2 */
    055        XOAUTH2("XOAUTH2");
    056
    057        private final String authName;
    058
    059        AUTH_METHOD(final String name) {
    060            this.authName = name;
    061        }
    062
    063        /**
    064         * Gets the name of the given authentication method suitable for the server.
    065         *
    066         * @return The name of the given authentication method suitable for the server.
    067         */
    068        public String getAuthName() {
    069            return authName;
    070        }
    071    }
    072
    073    /** {@link Mac} algorithm. */
    074    private static final String MAC_ALGORITHM = "HmacMD5";
    075
    076    /**
    077     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient. Sets security mode to explicit (isImplicit = false).
    078     */
    079    public AuthenticatingIMAPClient() {
    080        this(DEFAULT_PROTOCOL, false);
    081    }
    082
    083    /**
    084     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    085     *
    086     * @param implicit The security mode (Implicit/Explicit).
    087     */
    088    public AuthenticatingIMAPClient(final boolean implicit) {
    089        this(DEFAULT_PROTOCOL, implicit);
    090    }
    091
    092    /**
    093     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    094     *
    095     * @param implicit The security mode(Implicit/Explicit).
    096     * @param ctx      A pre-configured SSL Context.
    097     */
    098    public AuthenticatingIMAPClient(final boolean implicit, final SSLContext ctx) {
    099        this(DEFAULT_PROTOCOL, implicit, ctx);
    100    }
    101
    102    /**
    103     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    104     *
    105     * @param context A pre-configured SSL Context.
    106     */
    107    public AuthenticatingIMAPClient(final SSLContext context) {
    108        this(false, context);
    109    }
    110
    111    /**
    112     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    113     *
    114     * @param proto the protocol.
    115     */
    116    public AuthenticatingIMAPClient(final String proto) {
    117        this(proto, false);
    118    }
    119
    120    /**
    121     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    122     *
    123     * @param proto    the protocol.
    124     * @param implicit The security mode(Implicit/Explicit).
    125     */
    126    public AuthenticatingIMAPClient(final String proto, final boolean implicit) {
    127        this(proto, implicit, null);
    128    }
    129
    130    /**
    131     * Constructor for AuthenticatingIMAPClient that delegates to IMAPSClient.
    132     *
    133     * @param proto    the protocol.
    134     * @param implicit The security mode(Implicit/Explicit).
    135     * @param ctx      the context
    136     */
    137    public AuthenticatingIMAPClient(final String proto, final boolean implicit, final SSLContext ctx) {
    138        super(proto, implicit, ctx);
    139    }
    140
    141    /**
    142     * Authenticate to the IMAP server by sending the AUTHENTICATE command with the selected mechanism, using the given user and the given password.
    143     *
    144     * @param method   the method name
    145     * @param user user
    146     * @param password password
    147     * @return True if successfully completed, false if not.
    148     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    149     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    150     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    151     */
    152    public boolean auth(final AuthenticatingIMAPClient.AUTH_METHOD method, final String user, final String password)
    153            throws IOException, NoSuchAlgorithmException, InvalidKeyException {
    154        if (!IMAPReply.isContinuation(sendCommand(IMAPCommand.AUTHENTICATE, method.getAuthName()))) {
    155            return false;
    156        }
    157
    158        switch (method) {
    159        case PLAIN: {
    160            // the server sends an empty response ("+ "), so we don't have to read it.
    161            final int result = sendData(Base64.getEncoder().encodeToString(("\000" + user + "\000" + password).getBytes(getCharset())));
    162            if (result == IMAPReply.OK) {
    163                setState(IMAP.IMAPState.AUTH_STATE);
    164            }
    165            return result == IMAPReply.OK;
    166        }
    167        case CRAM_MD5: {
    168            // get the CRAM challenge (after "+ ")
    169            final byte[] serverChallenge = Base64.getDecoder().decode(getReplyString().substring(2).trim());
    170            // get the Mac instance
    171            final Mac hmacMd5 = Mac.getInstance(MAC_ALGORITHM);
    172            hmacMd5.init(new SecretKeySpec(password.getBytes(getCharset()), MAC_ALGORITHM));
    173            // compute the result:
    174            final byte[] hmacResult = convertToHexString(hmacMd5.doFinal(serverChallenge)).getBytes(getCharset());
    175            // join the byte arrays to form the reply
    176            final byte[] usernameBytes = user.getBytes(getCharset());
    177            final byte[] toEncode = new byte[usernameBytes.length + 1 /* the space */ + hmacResult.length];
    178            System.arraycopy(usernameBytes, 0, toEncode, 0, usernameBytes.length);
    179            toEncode[usernameBytes.length] = ' ';
    180            System.arraycopy(hmacResult, 0, toEncode, usernameBytes.length + 1, hmacResult.length);
    181            // send the reply and read the server code:
    182            final int result = sendData(Base64.getEncoder().encodeToString(toEncode));
    183            if (result == IMAPReply.OK) {
    184                setState(IMAP.IMAPState.AUTH_STATE);
    185            }
    186            return result == IMAPReply.OK;
    187        }
    188        case LOGIN: {
    189            // the server sends fixed responses (base64("UserName") and
    190            // base64("Password")), so we don't have to read them.
    191            if (sendData(Base64.getEncoder().encodeToString(user.getBytes(getCharset()))) != IMAPReply.CONT) {
    192                return false;
    193            }
    194            final int result = sendData(Base64.getEncoder().encodeToString(password.getBytes(getCharset())));
    195            if (result == IMAPReply.OK) {
    196                setState(IMAP.IMAPState.AUTH_STATE);
    197            }
    198            return result == IMAPReply.OK;
    199        }
    200        case XOAUTH:
    201        case XOAUTH2: {
    202            final int result = sendData(user);
    203            if (result == IMAPReply.OK) {
    204                setState(IMAP.IMAPState.AUTH_STATE);
    205            }
    206            return result == IMAPReply.OK;
    207        }
    208        }
    209        return false; // safety check
    210    }
    211
    212    /**
    213     * Authenticate to the IMAP server by sending the AUTHENTICATE command with the selected mechanism, using the given user and the given password.
    214     *
    215     * @param method   the method name
    216     * @param user user
    217     * @param password password
    218     * @return True if successfully completed, false if not.
    219     * @throws IOException              If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
    220     * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
    221     * @throws InvalidKeyException      If the CRAM hash algorithm failed to use the given password.
    222     */
    223    public boolean authenticate(final AuthenticatingIMAPClient.AUTH_METHOD method, final String user, final String password)
    224            throws IOException, NoSuchAlgorithmException, InvalidKeyException {
    225        return auth(method, user, password);
    226    }
    227
    228    /**
    229     * 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
    230     * this is the ASCII code (and the byte value) of the capital letter 'A'.
    231     *
    232     * @param a The byte array to convert.
    233     * @return The resulting String of hexadecimal codes.
    234     */
    235    private String convertToHexString(final byte[] a) {
    236        final StringBuilder result = new StringBuilder(a.length * 2);
    237        for (final byte element : a) {
    238            if ((element & 0x0FF) <= 15) {
    239                result.append("0");
    240            }
    241            result.append(Integer.toHexString(element & 0x0FF));
    242        }
    243        return result.toString();
    244    }
    245}
    246