1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one or more
3 * contributor license agreements. See the NOTICE file distributed with
4 * this work for additional information regarding copyright ownership.
5 * The ASF licenses this file to You under the Apache License, Version 2.0
6 * (the "License"); you may not use this file except in compliance with
7 * the License. You may obtain a copy of the License at
8 *
9 * https://www.apache.org/licenses/LICENSE-2.0
10 *
11 * Unless required by applicable law or agreed to in writing, software
12 * distributed under the License is distributed on an "AS IS" BASIS,
13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 * See the License for the specific language governing permissions and
15 * limitations under the License.
16 */
17
18 package org.apache.commons.net.pop3;
19
20 import java.io.IOException;
21 import java.security.InvalidKeyException;
22 import java.security.NoSuchAlgorithmException;
23 import java.util.Base64;
24
25 import javax.crypto.Mac;
26 import javax.crypto.spec.SecretKeySpec;
27
28 /**
29 * A POP3 Client class with protocol and authentication extensions support (RFC2449 and RFC2195).
30 *
31 * @see POP3Client
32 * @since 3.0
33 */
34 public class ExtendedPOP3Client extends POP3SClient {
35
36 /**
37 * The enumeration of currently-supported authentication methods.
38 */
39 public enum AUTH_METHOD {
40
41 /** The standardized (RFC4616) PLAIN method, which sends the password unencrypted (insecure). */
42 PLAIN("PLAIN"),
43
44 /** The standardized (RFC2195) CRAM-MD5 method, which doesn't send the password (secure). */
45 CRAM_MD5("CRAM-MD5");
46
47 private final String methodName;
48
49 AUTH_METHOD(final String methodName) {
50 this.methodName = methodName;
51 }
52
53 /**
54 * Gets the name of the given authentication method suitable for the server.
55 *
56 * @return The name of the given authentication method suitable for the server.
57 */
58 public String getAuthName() {
59 return methodName;
60 }
61 }
62
63 /** {@link Mac} algorithm. */
64 private static final String MAC_ALGORITHM = "HmacMD5";
65
66 /**
67 * The default ExtendedPOP3Client constructor. Creates a new Extended POP3 Client.
68 *
69 * @throws NoSuchAlgorithmException Never thrown here.
70 */
71 public ExtendedPOP3Client() throws NoSuchAlgorithmException {
72 }
73
74 /**
75 * Authenticate to the POP3 server by sending the AUTH command with the selected mechanism, using the given user and the given password.
76 *
77 * @param method the {@link AUTH_METHOD} to use
78 * @param user the user name
79 * @param password the password
80 * @return True if successfully completed, false if not.
81 * @throws IOException If an I/O error occurs while either sending a command to the server or receiving a reply from the server.
82 * @throws NoSuchAlgorithmException If the CRAM hash algorithm cannot be instantiated by the Java runtime system.
83 * @throws InvalidKeyException If the CRAM hash algorithm failed to use the given password.
84 */
85 public boolean auth(final AUTH_METHOD method, final String user, final String password)
86 throws IOException, NoSuchAlgorithmException, InvalidKeyException {
87 if (sendCommand(POP3Command.AUTH, method.getAuthName()) != POP3Reply.OK_INT) {
88 return false;
89 }
90
91 switch (method) {
92 case PLAIN:
93 // the server sends an empty response ("+ "), so we don't have to read it.
94 return sendCommand(
95 new String(Base64.getEncoder().encode(("\000" + user + "\000" + password).getBytes(getCharset())), getCharset())) == POP3Reply.OK;
96 case CRAM_MD5:
97 // get the CRAM challenge
98 final byte[] serverChallenge = Base64.getDecoder().decode(getReplyString().substring(2).trim());
99 // 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 }