1/*
2 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25
26package sun.security.krb5.internal.ssl;
27
28import java.io.*;
29import java.security.*;
30import java.util.Arrays;
31
32import javax.net.ssl.*;
33
34import sun.security.krb5.EncryptionKey;
35import sun.security.krb5.EncryptedData;
36import sun.security.krb5.KrbException;
37import sun.security.krb5.internal.crypto.KeyUsage;
38
39import sun.security.ssl.Debug;
40import sun.security.ssl.HandshakeInStream;
41import sun.security.ssl.HandshakeMessage;
42import sun.security.ssl.ProtocolVersion;
43
44/**
45 * This is the Kerberos premaster secret in the Kerberos client key
46 * exchange message (CLIENT --> SERVER); it holds the
47 * Kerberos-encrypted pre-master secret. The secret is encrypted using the
48 * Kerberos session key.  The padding and size of the resulting message
49 * depends on the session key type, but the pre-master secret is
50 * always exactly 48 bytes.
51 *
52 */
53final class KerberosPreMasterSecret {
54
55    private ProtocolVersion protocolVersion; // preMaster [0,1]
56    private byte[] preMaster;           // 48 bytes
57    private byte[] encrypted;
58
59    /**
60     * Constructor used by client to generate premaster secret.
61     *
62     * Client randomly creates a pre-master secret and encrypts it
63     * using the Kerberos session key; only the server can decrypt
64     * it, using the session key available in the service ticket.
65     *
66     * @param protocolVersion used to set preMaster[0,1]
67     * @param generator random number generator for generating premaster secret
68     * @param sessionKey Kerberos session key for encrypting premaster secret
69     */
70    KerberosPreMasterSecret(ProtocolVersion protocolVersion,
71            SecureRandom generator, EncryptionKey sessionKey) throws IOException {
72
73        if (sessionKey.getEType() ==
74                EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD) {
75            throw new IOException(
76                    "session keys with des3-cbc-hmac-sha1-kd encryption type " +
77                            "are not supported for TLS Kerberos cipher suites");
78        }
79
80        this.protocolVersion = protocolVersion;
81        preMaster = generatePreMaster(generator, protocolVersion);
82
83        // Encrypt premaster secret
84        try {
85            EncryptedData eData = new EncryptedData(sessionKey, preMaster,
86                    KeyUsage.KU_UNKNOWN);
87            encrypted = eData.getBytes();  // not ASN.1 encoded.
88
89        } catch (KrbException e) {
90            throw (SSLKeyException)new SSLKeyException
91                    ("Kerberos premaster secret error").initCause(e);
92        }
93    }
94
95    /*
96     * Constructor used by server to decrypt encrypted premaster secret.
97     * The protocol version in preMaster[0,1] must match either currentVersion
98     * or clientVersion, otherwise, the premaster secret is set to
99     * a random one to foil possible attack.
100     *
101     * @param currentVersion version of protocol being used
102     * @param clientVersion version requested by client
103     * @param generator random number generator used to generate
104     *        bogus premaster secret if premaster secret verification fails
105     * @param input input stream from which to read the encrypted
106     *        premaster secret
107     * @param sessionKey Kerberos session key to be used for decryption
108     */
109    KerberosPreMasterSecret(ProtocolVersion currentVersion,
110            ProtocolVersion clientVersion,
111            SecureRandom generator, byte[] encrypted,
112            EncryptionKey sessionKey) throws IOException {
113
114        if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {
115            if (encrypted != null) {
116                Debug.println(System.out,
117                        "encrypted premaster secret", encrypted);
118            }
119        }
120
121        if (sessionKey.getEType() ==
122                EncryptedData.ETYPE_DES3_CBC_HMAC_SHA1_KD) {
123            throw new IOException(
124                    "session keys with des3-cbc-hmac-sha1-kd encryption type " +
125                            "are not supported for TLS Kerberos cipher suites");
126        }
127
128        // Decrypt premaster secret
129        try {
130            EncryptedData data = new EncryptedData(sessionKey.getEType(),
131                    null /* optional kvno */, encrypted);
132
133            byte[] temp = data.decrypt(sessionKey, KeyUsage.KU_UNKNOWN);
134            if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {
135                if (encrypted != null) {
136                    Debug.println(System.out,
137                            "decrypted premaster secret", temp);
138                }
139            }
140
141            // Remove padding bytes after decryption. Only DES and DES3 have
142            // paddings and we don't support DES3 in TLS (see above)
143
144            if (temp.length == 52 &&
145                    data.getEType() == EncryptedData.ETYPE_DES_CBC_CRC) {
146                // For des-cbc-crc, 4 paddings. Value can be 0x04 or 0x00.
147                if (paddingByteIs(temp, 52, (byte)4) ||
148                        paddingByteIs(temp, 52, (byte)0)) {
149                    temp = Arrays.copyOf(temp, 48);
150                }
151            } else if (temp.length == 56 &&
152                    data.getEType() == EncryptedData.ETYPE_DES_CBC_MD5) {
153                // For des-cbc-md5, 8 paddings with 0x08, or no padding
154                if (paddingByteIs(temp, 56, (byte)8)) {
155                    temp = Arrays.copyOf(temp, 48);
156                }
157            }
158
159            preMaster = temp;
160
161            protocolVersion = ProtocolVersion.valueOf(preMaster[0],
162                    preMaster[1]);
163            if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {
164                System.out.println("Kerberos PreMasterSecret version: "
165                        + protocolVersion);
166            }
167        } catch (Exception e) {
168            // catch exception & process below
169            preMaster = null;
170            protocolVersion = currentVersion;
171        }
172
173        // check if the premaster secret version is ok
174        // the specification says that it must be the maximum version supported
175        // by the client from its ClientHello message. However, many
176        // old implementations send the negotiated version, so accept both
177        // for SSL v3.0 and TLS v1.0.
178        // NOTE that we may be comparing two unsupported version numbers in
179        // the second case, which is why we cannot use object references
180        // equality in this special case
181        boolean versionMismatch = (protocolVersion.v != clientVersion.v);
182
183        /*
184         * we never checked the client_version in server side
185         * for TLS v1.0 and SSL v3.0. For compatibility, we
186         * maintain this behavior.
187         */
188        if (versionMismatch && (clientVersion.v <= 0x0301)) {
189            versionMismatch = (protocolVersion.v != currentVersion.v);
190        }
191
192        /*
193         * Bogus decrypted ClientKeyExchange? If so, conjure a
194         * a random preMaster secret that will fail later during
195         * Finished message processing. This is a countermeasure against
196         * the "interactive RSA PKCS#1 encryption envelop attack" reported
197         * in June 1998. Preserving the executation path will
198         * mitigate timing attacks and force consistent error handling
199         * that will prevent an attacking client from differentiating
200         * different kinds of decrypted ClientKeyExchange bogosities.
201         */
202        if ((preMaster == null) || (preMaster.length != 48)
203                || versionMismatch) {
204            if (HandshakeMessage.debug != null && Debug.isOn("handshake")) {
205                System.out.println("Kerberos PreMasterSecret error, "
206                        + "generating random secret");
207                if (preMaster != null) {
208                    Debug.println(System.out, "Invalid secret", preMaster);
209                }
210            }
211
212            /*
213             * Randomize the preMaster secret with the
214             * ClientHello.client_version, as will produce invalid master
215             * secret to prevent the attacks.
216             */
217            preMaster = generatePreMaster(generator, clientVersion);
218            protocolVersion = clientVersion;
219        }
220    }
221
222    /**
223     * Checks if all paddings of data are b
224     * @param data the block with padding
225     * @param len length of data, >= 48
226     * @param b expected padding byte
227     */
228    private static boolean paddingByteIs(byte[] data, int len, byte b) {
229        for (int i=48; i<len; i++) {
230            if (data[i] != b) return false;
231        }
232        return true;
233    }
234
235    /*
236     * Used by server to generate premaster secret in case of
237     * problem decoding ticket.
238     *
239     * @param protocolVersion used for preMaster[0,1]
240     * @param generator random number generator to use for generating secret.
241     */
242    KerberosPreMasterSecret(ProtocolVersion protocolVersion,
243            SecureRandom generator) {
244
245        this.protocolVersion = protocolVersion;
246        preMaster = generatePreMaster(generator, protocolVersion);
247    }
248
249    private static byte[] generatePreMaster(SecureRandom rand,
250            ProtocolVersion ver) {
251
252        byte[] pm = new byte[48];
253        rand.nextBytes(pm);
254        pm[0] = ver.major;
255        pm[1] = ver.minor;
256
257        return pm;
258    }
259
260    // Clone not needed; internal use only
261    byte[] getUnencrypted() {
262        return preMaster;
263    }
264
265    // Clone not needed; internal use only
266    byte[] getEncrypted() {
267        return encrypted;
268    }
269}
270